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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Ecol. Evol.</journal-id>
<journal-title-group>
<journal-title>Frontiers in Ecology and Evolution</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Ecol. Evol.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">2296-701X</issn>
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<publisher-name>Frontiers Media S.A.</publisher-name>
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<article-meta>
<article-id pub-id-type="doi">10.3389/fevo.2025.1635979</article-id>
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<article-categories>
<subj-group subj-group-type="heading">
<subject>Original Research</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Quantifying the spatio-temporal dynamics and coupling coordination of PLE spaces in Heilongjiang&#x2019;s Grain Belt: a grid-based geospatial analysis</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name><surname>Ge</surname><given-names>Sijia</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
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<contrib contrib-type="author" corresp="yes">
<name><surname>Ma</surname><given-names>Yanji</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="corresp" rid="c001"><sup>*</sup></xref>
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<aff id="aff1"><label>1</label><institution>Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences</institution>, <city>Changchun</city>, <state>Jilin</state>,&#xa0;<country country="cn">China</country></aff>
<aff id="aff2"><label>2</label><institution>College of Resources and Environment, University of Chinese Academy of Sciences</institution>, <city>Beijing</city>,&#xa0;<country country="cn">China</country></aff>
<author-notes>
<corresp id="c001"><label>*</label>Correspondence: Yanji Ma, <email xlink:href="mailto:mayanji@iga.ac.cn">mayanji@iga.ac.cn</email></corresp>
</author-notes>
<pub-date publication-format="electronic" date-type="pub" iso-8601-date="2025-09-25">
<day>25</day>
<month>09</month>
<year>2025</year>
</pub-date>
<pub-date publication-format="electronic" date-type="collection">
<year>2025</year>
</pub-date>
<volume>13</volume>
<elocation-id>1635979</elocation-id>
<history>
<date date-type="received">
<day>29</day>
<month>05</month>
<year>2025</year>
</date>
<date date-type="accepted">
<day>05</day>
<month>09</month>
<year>2025</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#xa9; 2025 Ge and Ma.</copyright-statement>
<copyright-year>2025</copyright-year>
<copyright-holder>Ge and Ma</copyright-holder>
<license>
<ali:license_ref start_date="2025-09-25">https://creativecommons.org/licenses/by/4.0/</ali:license_ref>
<license-p>This is an open-access article distributed under the terms of the <ext-link ext-link-type="uri" xlink:href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution License (CC BY)</ext-link>. The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</license-p>
</license>
</permissions>
<abstract>
<sec>
<title>Introduction</title>
<p>China&#x2019;s major grain-producing areas are facing increasingly prominent tensions between grain security and ecological protection. A systematic understanding of the evolution and coordination mechanisms of production&#x2013;living&#x2013;ecological (PLE) spaces is essential for promoting efficient land allocation and regional sustainable development.</p>
</sec>
<sec>
<title>Methods</title>
<p>Taking Heilongjiang Province as a representative case, we constructed a functional classification&#x2013;evaluation system for PLE spaces using land-use data from 2000, 2010, and 2020. Spatial analysis, land use transfer matrices, coupling coordination models, and gravity center migration methods were applied to assess functional evolution and spatial synergy.</p>
</sec>
<sec>
<title>Results</title>
<p>(1) Production space in the Songnen and Sanjiang plains expanded significantly, primarily through conversion of ecological space; (2) The spatial agglomeration of production space slightly declined (Moran&#x2019;s I decreased from 0.7567 to 0.7508); (3) Overall coupling coordination steadily improved, though production&#x2013;living integration remained weak in rural areas; (4) The coupling coordination center of gravity exhibited a &#x201c;northward-then-southward&#x201d; shift, reflecting a transition from ecological to agricultural spatial dominance.</p>
</sec>
<sec>
<title>Conclusion</title>
<p>This research makes three significant contributions: first, by integrating spatiotemporal dynamics with spatial coupling analysis, it systematically decodes the functional transition logic and trade-off mechanisms governing PLE spaces in grain-producing regions; second, it substantiates China&#x2019;s &#x201c;Big Food Vision&#x201d; policy by demonstrating how diversified food sources across forests, grasslands, and aquatic systems can harmonize ecological conservation with sustainable land use; third, it highlights marked regional differentiation in PLE space evolution, showing that while agricultural cores exhibit relatively high coordination, production&#x2013;living synergy remains suboptimal, necessitating targeted spatial governance interventions.</p>
</sec>
</abstract>
<kwd-group>
<kwd>major grain-producing areas</kwd>
<kwd>production-living-ecological (PLE) spaces</kwd>
<kwd>Heilongjiang Province</kwd>
<kwd>spatiotemporal evolution</kwd>
<kwd>coupling coordination</kwd>
</kwd-group>
<funding-group>
<funding-statement>The author(s) declare financial support was received for the research and/or publication of this article. Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA28070501).</funding-statement>
</funding-group>
<counts>
<fig-count count="14"/>
<table-count count="2"/>
<equation-count count="6"/>
<ref-count count="46"/>
<page-count count="16"/>
<word-count count="7917"/>
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<custom-meta>
<meta-name>section-in-acceptance</meta-name>
<meta-value>Biogeography and Macroecology</meta-value>
</custom-meta>
</custom-meta-group>
</article-meta>
</front>
<body>
<sec id="s1" sec-type="intro">
<label>1</label>
<title>Introduction</title>
<p>Global food security serves as the cornerstone of sustainable development for human society, and major grain-producing regions (Grain Belts) act as a stabilizing force in safeguarding this security. These regions&#x2014;such as the U.S. Corn Belt, Ukraine&#x2019;s Black Soil Region, and China&#x2019;s Northeast Plain&#x2014;face tremendous challenges in simultaneously securing food production while balancing economic development, urbanization, and ecological conservation. Conflicts and trade-offs among production-living-ecological (PLE) spaces have become central issues in the pursuit of sustainable development in these key areas. As one of the world&#x2019;s leading producers and consumers of food, China&#x2019;s spatial governance practices in its major grain-producing regions offer valuable references for similar regions globally (<xref ref-type="bibr" rid="B28">National Development and Reform Commission of the People's Republic of China, 2008</xref>). Heilongjiang Province, the core grain-producing region in China, exemplifies the spatial evolution of PLE spaces. Its transformation is closely tied to national food security and provides a typical case for exploring land use transitions and functional coordination in high-intensity agricultural zones worldwide. In recent years, driven by rapid socio-economic development and accelerated urbanization, conflicts among PLE spaces in major grain-producing areas have become increasingly prominent. Optimizing the spatial configuration of PLE spaces and balancing their production, living, and ecological functions represents a key strategy for promoting sustainable development in grain-producing regions.</p>
<p>International research on multifunctionality in land use emerged in the late 20th century, focusing primarily on the classification and assessment of productive, economic, social, and ecological functions. Studies on agricultural multifunctionality (<xref ref-type="bibr" rid="B36">Tait, 2001</xref>; <xref ref-type="bibr" rid="B13">Johansen et&#xa0;al., 2018</xref>; <xref ref-type="bibr" rid="B4">Callesen et&#xa0;al., 2022</xref>; <xref ref-type="bibr" rid="B24">Machefer et&#xa0;al., 2024</xref>) and the value conversion approaches from the TEEB initiative (<xref ref-type="bibr" rid="B17">Li and Fang, 2016</xref>) have provided theoretical foundations and practical tools for optimizing land use. Spatial simulation models and ecosystem service assessments have become the widely adopted methodologies. In recent years, growing attention has been given to land use conflicts, social equity, and regional coordination. <xref ref-type="bibr" rid="B33">Salhi et&#xa0;al. (2020)</xref> evaluated the social and environmental consequences of land use conflicts in a Mediterranean watershed, highlighting threats to sustainability from stakeholder misalignment. <xref ref-type="bibr" rid="B34">Sheikh and van Ameijde (2022)</xref> developed a comprehensive livability framework based on the &#x201c;theory of human needs,&#x201d; emphasizing spatial justice and planning responsiveness. <xref ref-type="bibr" rid="B2">Assiri et&#xa0;al. (2020)</xref> proposed a methodological framework to analyze the sustainability of local productive systems, promoting synergy between economic growth and environmental sustainability. <xref ref-type="bibr" rid="B14">Kangas et&#xa0;al. (2022)</xref> analyzed land use synergies and conflicts to inform spatial compatibility assessments. <xref ref-type="bibr" rid="B3">Bole et&#xa0;al. (2025)</xref> advanced an integrated assessment model of resources, environment, and ecology based on the PLE framework, underscoring multifunctionality as central to land carrying capacity. Remote sensing studies by <xref ref-type="bibr" rid="B1">Aslam et&#xa0;al. (2024)</xref> and <xref ref-type="bibr" rid="B10">Gazi et&#xa0;al. (2023)</xref>. further revealed how socio-economic dynamics and urbanization drive land-use transitions in wetlands and coastal zones.</p>
<p>Domestic research on production-living-ecological (PLE) spaces started relatively late. Scholars usually adopt two perspectives. One is based on the land use classification system (<xref ref-type="bibr" rid="B38">Wei et&#xa0;al., 2024</xref>; <xref ref-type="bibr" rid="B40">Xu et&#xa0;al., 2024</xref>; <xref ref-type="bibr" rid="B42">Yin et&#xa0;al., 2024</xref>), using current land use data to classify regional functional areas from the bottom up. Although this method is intuitive, the classification criteria are highly subjective, and it is difficult for this approach to fully reflect the multifunctional nature of land. The other is based on a functional evaluation system (<xref ref-type="bibr" rid="B21">Liu et&#xa0;al., 2017</xref>; <xref ref-type="bibr" rid="B15">Kong et&#xa0;al., 2021</xref>; <xref ref-type="bibr" rid="B22">Luo and Chen, 2023</xref>), through constructing an index system covering social, economic, and ecological dimensions, to assess the distribution of functions from the top down. Although this method is comprehensive, indicator selection is complex, data acquisition is challenging, and index systems vary in different studies, making horizontal comparisons of research results difficult. Therefore, constructing an evaluation scheme that reflects the functional characteristics of major grain-producing areas while being both objective and practical remains a challenge facing current research. With continuous methodological refinements and technological advancements, numerous empirical analyses related to PLE spaces were conducted. <xref ref-type="bibr" rid="B35">Sui et&#xa0;al. (2020)</xref> identified PLE spaces in Keshan County, a major grain-producing area in Songnen Plain&#x2019;s northern region. <xref ref-type="bibr" rid="B9">Fu et al. (2022)</xref> established an integrated evaluation index system combining grid-scale and administrative-scale approaches to assess spatial functionality in black soil regions, and analyzed the evolution patterns of PLE land use within Qiqihar. <xref ref-type="bibr" rid="B46">Zhou et&#xa0;al. (2024)</xref> utilized dynamic degree index, land-use transfer matrices, and center of gravity models to analyze the transformation dynamics of PLE spaces in Heilongjiang Province, while employing the InVEST model to assess carbon storage changes. <xref ref-type="bibr" rid="B7">Du et&#xa0;al. (2016)</xref> developed a three-dimensional &#x201c;socio-economic-ecological&#x201d; evaluation index system to assess land-use multifunctionality comprehensively in Northeast China. From a spatial-scale perspective, existing studies predominantly adopt administrative units (e.g., provinces, cities, counties) as analytical units. Such approaches readily integrate with socio-economic statistical data to serve macro-policy making, but often overlook internal spatial heterogeneity within administrative boundaries. Consequently, they struggle to accurately depict the evolution of PLE spatial functions. The grid-scale analysis effectively overcomes this limitation, revealing aggregation, conflict, and coupling patterns in PLE spaces more intuitively. Nevertheless, studies integrating fine-grained grid analysis with macro-functional evolution and dynamic spatial transition trajectories in major grain-producing areas remain limited.</p>
<p>In summary, although existing literature has laid a solid foundation for PLE space research, comparison with prior studies concerning indicator systems and spatial scales identifies the following gaps requiring exploration (<xref ref-type="bibr" rid="B30">Pang et&#xa0;al., 2021</xref>; <xref ref-type="bibr" rid="B29">Ni et&#xa0;al., 2022</xref>). First, regarding indicator system construction, existing studies either adopt highly subjective direct classification methods, or develop complex systems lacking cross-study comparability. This reveals a deficiency in quantitative evaluation schemes that are both targeted and operable for regions with intricately interwoven ecological-production functions, such as major grain-producing areas. The function scoring method based on land use types directly addresses this gap. Second, concerning spatial scale and analytical methods, mainstream administrative-unit research obscures internal spatial details, while existing grid-scale studies predominantly characterize static patterns. Few integrate refined spatial analysis with dynamic trajectory modeling of coupling coordination (e.g., center-of-gravity shift models), thus failing to reveal co-evolution directions and driving mechanisms of functional spaces. Third, theoretically, current research rarely links PLE synergy analyses to national macro-strategies like the &#x201c;Great Food View&#x201d; (a national food security strategy), resulting in limited strategic relevance and actionable implementation guidance for policies.</p>
<p>To bridge these gaps, this study selects Heilongjiang Province&#x2014;one of China&#x2019;s strategically vital grain-producing regions&#x2014;as a case study, aiming to contribute in three aspects: (1) constructing a PLE functional classification/evaluation system tailored to grain-producing regions; (2) integrating transition matrices, coupling coordination models, and center-of-gravity shift analysis to reveal spatiotemporal evolution patterns and quantify coupling coordination trajectories; and (3) exploring implementation pathways for regional spatial synergy optimization within the &#x201c;Great Food View&#x201d; framework. These contributions provide scientific references for sustainable development and spatial governance in Heilongjiang and comparable global grain-producing regions.</p>
</sec>
<sec id="s2">
<label>2</label>
<title>Research framework</title>
<sec id="s2_1">
<label>2.1</label>
<title>Study area</title>
<p>Heilongjiang Province (121&#xb0;11&#x2032;E&#x2013;135&#xb0;05&#x2032;E, 43&#xb0;26&#x2032;N&#x2013;53&#xb0;33&#x2032; N) occupies northeastern China, encompassing 473,000 km&#xb2;&#x2014;ranking sixth nationally in land area. Its terrain features higher elevations in the northwest, north, and southeast, contrasting with lower elevations in the northeast and southwest (<xref ref-type="fig" rid="f1"><bold>Figure&#xa0;1</bold></xref>). Diverse landforms, including mountains, terraces, plains, and water systems, are distributed across the Songnen Plain, Sanjiang Plain, and Greater and Lesser Khingan Mountains. Major rivers (e.g., Heilongjiang, Songhua) and lakes (e.g., Xingkai, Jingpo) provide optimal natural endowments for agriculture (<xref ref-type="bibr" rid="B31">People's Government of Heilongjiang Province, 2024</xref>).</p>
<fig id="f1" position="float">
<label>Figure&#xa0;1</label>
<caption>
<p>Location of the study area.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g001.tif">
<alt-text content-type="machine-generated">Map comparing geographical and land use features of a study area in northeastern China. The top left panel shows the study area's location within China. The bottom left panel is a digital elevation model highlighting variations in elevation from high (red) to low (blue). The right panel displays land use types such as cultivated land, woodland, and grassland, with a legend for classification. Boundaries are marked for provinces and cities, with a scale indicating distances in kilometers.</alt-text>
</graphic>
</fig>
<p>As China&#x2019;s primary grain-producing region, the province comprises 12 prefecture-level cities and one prefectural-level division, crucially sustaining national food security. The Statistical Bulletin (2023) reports its 2023 grain output at 77.882 million tons, with rice (24.400 million tons), maize (43.790 million tons), and soybeans (9.278 million tons) collectively constituting 11% of China&#x2019;s total output (<xref ref-type="bibr" rid="B12">Heilongjiang Provincial Bureau of Statistics and National Bureau of Statistics Survey Office in Heilongjiang, 2024</xref>). Rapid socio-economic development and urbanization have recently compelled the region to confront complex conflicts amidst expanding production spaces, increasing living spaces, and shrinking ecological spaces&#x2014;all during sustained grain production (<xref ref-type="bibr" rid="B41">Xue and Ma, 2022</xref>). These contradictions intensify the imbalance between resource utilization efficiency and ecological integrity, necessitating scientific investigation of PLE spatial evolution patterns to guide optimized land allocation and ecological conservation.</p>
</sec>
<sec id="s2_2">
<label>2.2</label>
<title>Data sources</title>
<p>This study utilizes land-use remote sensing data (2000, 2010, 2020) for Heilongjiang Province. The 30-m resolution raster data were obtained from the Resource and Environment Science and Data Center (RESDC), Chinese Academy of Sciences (<xref ref-type="bibr" rid="B32">Resource and Environment Science and Data Center and Chinese Academy of Sciences, 2024</xref>). Administrative boundaries, provided without modification by China&#x2019;s Ministry of Natural Resources (<xref ref-type="bibr" rid="B27">Ministry of Natural Resources of the People&#x2019;s Republic of China, 2024</xref>), conform to the GS(2019)3333 and GS(2023)2763 mapping standards. All spatial data were uniformly projected to the WGS 1984 Albers Equal Area Conic projection. Data processing and analysis employed ArcGIS 10.4 and Origin 9.1.</p>
</sec>
</sec>
<sec id="s3">
<label>3</label>
<title>Research methods</title>
<sec id="s3_1">
<label>3.1</label>
<title>Classification system and evaluation index construction for PLE spaces</title>
<p>Production-living-ecological (PLE) spaces constitute integrated systems where land primarily serves dominant functions while supporting secondary functions (<xref ref-type="bibr" rid="B44">Zhang et&#xa0;al., 2015</xref>; <xref ref-type="bibr" rid="B41">Xue and Ma, 2022</xref>). Based on functional differences, land is classified into three types: production (e.g., cropland, industrial/mining areas for agriculture/operations), living (urban/rural settlements supporting human habitation), and ecological lands (forests, grasslands, wetlands, water bodies providing ecosystem services and environmental stability) (<xref ref-type="bibr" rid="B6">Cui et&#xa0;al., 2018</xref>).</p>
<p>China&#x2019;s State Council (<xref ref-type="bibr" rid="B11">General Office of the State Council of the People's Republic of China, 2024</xref>) emphasized in the &#x201c;Opinions on Implementing the Great Food View and Building a Diversified Food Supply System&#x201d; that grain security encompasses production, ecological, and social dimensions. In major grain-producing areas, land-use functions directly impact national grain security and ecological security goals. Proper management of PLE land interrelationships is fundamental to achieving sustainable regional development.</p>
<p>This study adapts methodologies from <xref ref-type="bibr" rid="B17">Li and Fang (2016)</xref>, <xref ref-type="bibr" rid="B21">Liu et&#xa0;al. (2017)</xref>, and <xref ref-type="bibr" rid="B6">Cui et&#xa0;al. (2018)</xref>&#x2014;specifically tailored to Heilongjiang&#x2014;to quantitatively evaluate land functions (<xref ref-type="bibr" rid="B44">Zhang et&#xa0;al., 2015</xref>). For assessment consistency, each land category was classified into six grades by functional intensity and coherence. Production lands, for example, are graded: strong (5&#xa0;points), relatively strong (4 points), semi-production (3 points), relatively weak (2 points), weak (1 point), and non-functional (0&#xa0;points). We applied identical grading principles to living/ecological functions, assigning dominant functions based on highest scores (ties resolved by dominant physical attributes). Scoring prioritizes the intensity and functional irreplaceability of dominant land-use functions. Key criteria include:</p>
<list list-type="">
<list-item>
<p>Production function: Paddy fields (5 points): Epitomize peak agricultural production due to maximum yield/unit area and capital/labor inputs. Drylands (4 points): Core production zones with 10-20% lower mean yield stability than paddies (based on provincial yield statistics 2000-2020).</p></list-item>
<list-item>
<p>Living function: Urban areas (5 points): Maximize settlement-supporting capacity through dense populations and integrated infrastructure. Industrial/transportation lands (2 points): Support economic activities but lack residential suitability.</p></list-item>
<list-item>
<p>Ecological function: Forests (5 points): Provide irreplaceable water/biodiversity conservation and carbon sequestration services. Low-coverage grasslands (2 points): Offer limited ecological services with 40-60% lower resilience than forests (per NDVI stability analysis).</p></list-item>
<list-item>
<p>We normalized functional scores to enable cross-spatial and cross-categorical comparisons. Based on Heilongjiang&#x2019;s current land-use patterns, this classification system captures major grain-producing area characteristics while embodying multifunctional land use principles. As detailed in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref>, land types were systematically categorized and scored to establish the core dataset for subsequent analysis.</p></list-item>
</list>
<table-wrap id="T1" position="float">
<label>Table&#xa0;1</label>
<caption>
<p>Land use classification system and scoring in Heilongjiang Province based on the "production-living-ecological " space.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="middle" colspan="2" align="center">Primary classification</th>
<th valign="middle" align="center">Secondary classification</th>
<th valign="middle" rowspan="2" align="center">Production land</th>
<th valign="middle" rowspan="2" align="center">Living land</th>
<th valign="middle" rowspan="2" align="center">Ecological land</th>
</tr>
<tr>
<th valign="middle" align="center">Code</th>
<th valign="middle" align="center">Name</th>
<th valign="middle" align="center">Code/ Name</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="middle" rowspan="2" align="center">1</td>
<td valign="middle" rowspan="2" align="center">Cultivated land</td>
<td valign="middle" align="center">11/Paddy field</td>
<td valign="middle" align="center">5</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">3</td>
</tr>
<tr>
<td valign="middle" align="center">12/Dry land</td>
<td valign="middle" align="center">4</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">3</td>
</tr>
<tr>
<td valign="middle" rowspan="4" align="center">2</td>
<td valign="middle" rowspan="4" align="center">Forest land</td>
<td valign="middle" align="center">21/Forested land</td>
<td valign="middle" align="center">2</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">22/Shrubland</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">23/Sparse woodland</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">24/Other forest land</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" rowspan="3" align="center">3</td>
<td valign="middle" rowspan="3" align="center">Grassland</td>
<td valign="middle" align="center">31/High-coverage grassland</td>
<td valign="middle" align="center">3</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">4</td>
</tr>
<tr>
<td valign="middle" align="center">32/Medium-coverage grassland</td>
<td valign="middle" align="center">2</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">4</td>
</tr>
<tr>
<td valign="middle" align="center">33/Low-coverage grassland</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">2</td>
</tr>
<tr>
<td valign="middle" rowspan="4" align="center">4</td>
<td valign="middle" rowspan="4" align="center">Water bodies</td>
<td valign="middle" align="center">41/Rivers and canals</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">3</td>
</tr>
<tr>
<td valign="middle" align="center">42/Lakes</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">43/Reservoirs and ponds</td>
<td valign="middle" align="center">2</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">3</td>
</tr>
<tr>
<td valign="middle" align="center">45/Mudflats</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" rowspan="3" align="center">5</td>
<td valign="middle" rowspan="3" align="center">Construction land</td>
<td valign="middle" align="center">51/Urban construction land</td>
<td valign="middle" align="center">2</td>
<td valign="middle" align="center">5</td>
<td valign="middle" align="center">0</td>
</tr>
<tr>
<td valign="middle" align="center">52/Rural residential land</td>
<td valign="middle" align="center">3</td>
<td valign="middle" align="center">5</td>
<td valign="middle" align="center">0</td>
</tr>
<tr>
<td valign="middle" align="center">53/Other construction land</td>
<td valign="middle" align="center">3</td>
<td valign="middle" align="center">2</td>
<td valign="middle" align="center">0</td>
</tr>
<tr>
<td valign="middle" rowspan="5" align="center">6</td>
<td valign="middle" rowspan="5" align="center">Unused land</td>
<td valign="middle" align="center">61/Sandy land</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">63/Saline-alkali land</td>
<td valign="middle" align="center">1</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">64/Marshland</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">65/Bare land</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
<tr>
<td valign="middle" align="center">66/Bare rocky and gravel land</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">0</td>
<td valign="middle" align="center">5</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
<sec id="s3_2">
<label>3.2</label>
<title>Analytical methods for spatiotemporal evolution of PLE spaces</title>
<p>We constructed a 3-km resolution grid using ArcGIS 10.4 to analyze the spatiotemporal evolution of PLE spaces in Heilongjiang Province. After assigning functional scores to land-use types, spatial overlay and min-max standardization generated PLE distribution maps for 2000, 2010, and 2020. Moran&#x2019;s I index measured spatial autocorrelation of PLE functions to quantify clustering characteristics and temporal trends (<xref ref-type="bibr" rid="B45">Zhou and Cheng, 2015</xref>; <xref ref-type="bibr" rid="B40">Xu et&#xa0;al., 2024</xref>; <xref ref-type="bibr" rid="B42">Yin et&#xa0;al., 2024</xref>). Additionally, Local Indicators of Spatial Association (LISA) identified high-high (HH) and low-low (LL) clusters, revealing PLE spatial distribution patterns and evolutionary trajectories across periods.</p>
</sec>
<sec id="s3_3">
<label>3.3</label>
<title>Construction and analysis of land-use transfer matrix for PLE spaces</title>
<p>To further reveal the dynamic changes in land areas of Production-Living-Ecological (PLE) spaces within the grain-producing region, this study employed a land-use transfer matrix to quantitatively analyze the directions and magnitudes of land type transitions in Heilongjiang Province during two periods: 2000&#x2013;2010 and 2010-2020. As a crucial tool in systemic analysis, the land-use transfer matrix accurately describes the mutual transformation relationships among different land categories and visually reflects the evolutionary processes of PLE spatial patterns over time (<xref ref-type="bibr" rid="B39">Xie et&#xa0;al., 2024</xref>). Using ArcGIS software to extract land-use data and Excel pivot tables to construct transfer matrices, the calculation is expressed by <xref ref-type="disp-formula" rid="eq1">Equation (1)</xref>:</p>
<disp-formula id="eq1"><label>(1)</label>
<mml:math display="block" id="M1"><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mi>i</mml:mi><mml:mi>j</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mo stretchy="false">[</mml:mo><mml:mtable equalrows="true" equalcolumns="true"><mml:mtr><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>11</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mo>&#x22ef;</mml:mo></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>1</mml:mn><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>21</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>22</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mo>&#x22ef;</mml:mo></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>2</mml:mn><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>31</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>32</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mo>&#x22ef;</mml:mo></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>3</mml:mn><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mo>&#x22ee;</mml:mo></mml:mtd><mml:mtd><mml:mo>&#x22ee;</mml:mo></mml:mtd><mml:mtd><mml:mo>&#x22ee;</mml:mo></mml:mtd><mml:mtd><mml:mo>&#x22ee;</mml:mo></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mi>n</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mi>n</mml:mi><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mtd><mml:mtd><mml:mo>&#x22ef;</mml:mo></mml:mtd><mml:mtd><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mi>n</mml:mi><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mtd></mml:mtr></mml:mtable><mml:mo stretchy="false">]</mml:mo></mml:mrow></mml:math>
</disp-formula>
<p>Where <italic>i</italic> represents the initial land-use type, <italic>j</italic> denotes the terminal land-use type, and <italic>S<sub>ij</sub></italic> indicates the land area transitioning from type <italic>i</italic> to type <italic>j</italic>. The symbol <italic>n</italic> denotes the total number of land-use types. Thus, the row sum represents the total land area of a specific type at the initial stage, while the column sum represents the total land area at the final stage.</p>
</sec>
<sec id="s3_4">
<label>3.4</label>
<title>Construction and calculation method of coupling coordination models for PLE spaces</title>
<p>To investigate the synergistic dynamics of production-living-ecological (PLE) functions in Heilongjiang Province, we developed an integrated coupling coordination model (<xref ref-type="bibr" rid="B5">Cong, 2019</xref>; <xref ref-type="bibr" rid="B35">Sui et&#xa0;al., 2020</xref>; <xref ref-type="bibr" rid="B16">Lei et&#xa0;al., 2024</xref>) with complementary pairwise submodels. We further traced spatiotemporal evolution through coupling coordination gravity migration analysis.</p>
<sec id="s3_4_1">
<label>3.4.1</label>
<title>Integrated PLE coupling coordination model</title>
<p>This framework quantifies multi-dimensional interactions among production, living, and ecological functions, which are formally expressed in <xref ref-type="disp-formula" rid="eq2">Equations (2</xref>&#x2013;<xref ref-type="disp-formula" rid="eq4">4)</xref>:</p>
<disp-formula id="eq2"><label>(2)</label>
<mml:math display="block" id="M2"><mml:mrow><mml:mtext>C</mml:mtext><mml:mo>=</mml:mo><mml:mn>3</mml:mn><mml:mo>&#xd7;</mml:mo><mml:msup><mml:mrow><mml:mo>{</mml:mo><mml:mfrac><mml:mrow><mml:msub><mml:mtext>P</mml:mtext><mml:mtext>i</mml:mtext></mml:msub><mml:mo>&#xb7;</mml:mo><mml:msub><mml:mtext>R</mml:mtext><mml:mtext>i</mml:mtext></mml:msub><mml:mo>&#xb7;</mml:mo><mml:msub><mml:mtext>E</mml:mtext><mml:mtext>i</mml:mtext></mml:msub></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mtext>P</mml:mtext><mml:mtext>i</mml:mtext></mml:msub><mml:mo>+</mml:mo><mml:msub><mml:mtext>R</mml:mtext><mml:mtext>i</mml:mtext></mml:msub><mml:mo>+</mml:mo><mml:msub><mml:mtext>E</mml:mtext><mml:mtext>i</mml:mtext></mml:msub><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mn>3</mml:mn></mml:msup></mml:mrow></mml:mfrac><mml:mo>}</mml:mo></mml:mrow><mml:mrow><mml:mfrac><mml:mn>1</mml:mn><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:mfrac></mml:mrow></mml:msup></mml:mrow></mml:math>
</disp-formula>
<disp-formula id="eq3"><label>(3)</label>
<mml:math display="block" id="M3"><mml:mrow><mml:mtext>T</mml:mtext><mml:mo>=</mml:mo><mml:mi>&#x3b1;</mml:mi><mml:msub><mml:mtext>P</mml:mtext><mml:mtext>i</mml:mtext></mml:msub><mml:mo>+</mml:mo><mml:mi>&#x3b2;</mml:mi><mml:msub><mml:mtext>R</mml:mtext><mml:mtext>i</mml:mtext></mml:msub><mml:mo>+</mml:mo><mml:mi>&#x3b3;</mml:mi><mml:msub><mml:mtext>E</mml:mtext><mml:mtext>i</mml:mtext></mml:msub></mml:mrow></mml:math>
</disp-formula>
<disp-formula id="eq4"><label>(4)</label>
<mml:math display="block" id="M4"><mml:mrow><mml:mtext>D</mml:mtext><mml:mo>=</mml:mo><mml:msqrt><mml:mrow><mml:mtext>C</mml:mtext><mml:mo>&#xb7;</mml:mo><mml:mtext>T</mml:mtext></mml:mrow></mml:msqrt></mml:mrow></mml:math>
</disp-formula>
<p>The coupling degree C quantifies interaction intensity among production-living-ecological (PLE) functions, while Pi, Ri, and Ei denote region i&#x2019;s production, living, and ecological function indices respectively. The comprehensive coordination index T reflects overall PLE synergistic development, with weighting coefficients &#x3b1;, &#x3b2;, and &#x3b3; assigned equal values of 1/3 based on functional equivalence in grain-producing systems (<xref ref-type="bibr" rid="B35">Sui et&#xa0;al., 2020</xref>; <xref ref-type="bibr" rid="B16">Lei et&#xa0;al., 2024</xref>; <xref ref-type="bibr" rid="B40">Xu et&#xa0;al., 2024</xref>).</p>
<p>The classification of coupling coordination degrees directly affects the judgment of regional development status. Currently, the equal interval method or threshold method is widely adopted in academia for classification (<xref ref-type="bibr" rid="B37">Wang and Tang, 2018</xref>; <xref ref-type="bibr" rid="B43">Yu et&#xa0;al., 2025</xref>). We establish five distinct tiers: [0, 0.2) severe imbalance, [0.2, 0.5) mild coordination, [0.5, 0.6) moderate coordination, [0.6, 0.8) high coordination, and [0.8, 1.0] excellent coordination. This framework delineates explicit coordination thresholds while capturing transitional states from conflict to synergy, enabling precise tracking of spatial functional evolution.</p>
</sec>
<sec id="s3_4_2">
<label>3.4.2</label>
<title>Pairwise PLE coupling coordination analysis</title>
<p>Beyond the integrated PLE coordination model, we established specialized pairwise coupling frameworks to dissect nuanced interactions within functional dyads&#x2014;production-ecological, production-living, and ecological-living systems (<xref ref-type="bibr" rid="B37">Wang and Tang, 2018</xref>; <xref ref-type="bibr" rid="B23">Luo et&#xa0;al., 2023</xref>). Weighting coefficients were calibrated to reflect intrinsic functional priorities: the production-ecological model assigned <italic>&#x3b1;</italic>&#xa0;=&#xa0;0.55 and <italic>&#x3b3;</italic>&#xa0;=&#xa0;0.45, the production-living model utilized balanced weights <italic>&#x3b1;</italic>&#xa0;=&#xa0;0.5 and <italic>&#x3b2;</italic>&#xa0;=&#xa0;0.5, while the living-ecological model employed <italic>&#x3b2;</italic>&#xa0;=&#xa0;0.55 and <italic>&#x3b3;</italic>&#xa0;=&#xa0;0.45. These targeted formulations overcome limitations of aggregate models by capturing asymmetric subsystem dynamics crucial for grain-producing systems, where production-ecological tensions often dominate spatial conflicts yet living-ecological synergies underpin long-term resilience.</p>
</sec>
<sec id="s3_4_3">
<label>3.4.3</label>
<title>Center-of-gravity shift analysis based on coupling coordination degree</title>
<p>Departing from conventional gravity models that focus on individual PLE functions, this study employs coupling coordination degree (D) as the mass attribute for spatial units. This approach tracks spatiotemporal shifts in systemic functional synergy, mapping migration pathways of integrated coordination states. Gravity centers for 2000, 2010, and 2020 were computed using D-values to analyze spatial distribution patterns and displacement trajectories (<xref ref-type="bibr" rid="B20">Lin et&#xa0;al., 2019</xref>; <xref ref-type="bibr" rid="B46">Zhou et&#xa0;al., 2024</xref>). The coordinates of the gravity center are calculated as shown in <xref ref-type="disp-formula" rid="eq5">Equations (5</xref>, <xref ref-type="disp-formula" rid="eq6">6)</xref>:</p>
<disp-formula id="eq5"><label>(5)</label>
<mml:math display="block" id="M5"><mml:mrow><mml:msub><mml:mtext>X</mml:mtext><mml:mtext>c</mml:mtext></mml:msub><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mstyle displaystyle="true"><mml:munderover><mml:mo>&#x2211;</mml:mo><mml:mrow><mml:mi>i</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow><mml:mtext>n</mml:mtext></mml:munderover><mml:mrow><mml:msub><mml:mi>x</mml:mi><mml:mi>i</mml:mi></mml:msub><mml:msub><mml:mi>D</mml:mi><mml:mi>i</mml:mi></mml:msub></mml:mrow></mml:mstyle></mml:mrow><mml:mrow><mml:mstyle displaystyle="true"><mml:munderover><mml:mo>&#x2211;</mml:mo><mml:mrow><mml:mi>i</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow><mml:mi>n</mml:mi></mml:munderover><mml:mrow><mml:msub><mml:mi>D</mml:mi><mml:mi>i</mml:mi></mml:msub></mml:mrow></mml:mstyle></mml:mrow></mml:mfrac></mml:mrow></mml:math>
</disp-formula>
<disp-formula id="eq6"><label>(6)</label>
<mml:math display="block" id="M6"><mml:mrow><mml:msub><mml:mi>Y</mml:mi><mml:mtext>c</mml:mtext></mml:msub><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mstyle displaystyle="true"><mml:munderover><mml:mo>&#x2211;</mml:mo><mml:mrow><mml:mi>i</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow><mml:mtext>n</mml:mtext></mml:munderover><mml:mrow><mml:msub><mml:mi>y</mml:mi><mml:mi>i</mml:mi></mml:msub><mml:msub><mml:mi>D</mml:mi><mml:mi>i</mml:mi></mml:msub></mml:mrow></mml:mstyle></mml:mrow><mml:mrow><mml:mstyle displaystyle="true"><mml:munderover><mml:mo>&#x2211;</mml:mo><mml:mrow><mml:mi>i</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow><mml:mi>n</mml:mi></mml:munderover><mml:mrow><mml:msub><mml:mi>D</mml:mi><mml:mi>i</mml:mi></mml:msub></mml:mrow></mml:mstyle></mml:mrow></mml:mfrac></mml:mrow></mml:math>
</disp-formula>
<p>Where <italic>X<sub>c</sub></italic> and <italic>Y<sub>c</sub></italic> denote gravity center coordinates, <italic>x<sub>i</sub></italic> and <italic>y<sub>i</sub></italic> represent the geographic centroid of grid cell <italic>i</italic>; and <italic>D<sub>i</sub></italic> indicates the coupling coordination degree at cell <italic>i</italic>.</p>
<p>Using GIS, we mapped the gravity center positions for 2000, 2010, and 2020 with displacement trajectories, quantitatively revealing dynamic evolutionary characteristics of Production-Living-Ecological (PLE) spatial coordination in major grain-producing areas.</p>
</sec>
</sec>
</sec>
<sec id="s4" sec-type="results">
<label>4</label>
<title>Results and analysis</title>
<sec id="s4_1">
<label>4.1</label>
<title>Spatiotemporal evolution characteristics of PLE spaces</title>
<sec id="s4_1_1">
<label>4.1.1</label>
<title>Temporal variation characteristics</title>
<p>Production space showed a continuous expansion trend. Specifically, the area of production space increased from 160,284.43 km&#xb2; in 2000 to 163,910.28 km&#xb2; in 2020, representing a net increase of 3,625.85 km&#xb2; over the past 20 years.</p>
<p>Living space experienced a &#x201c;rise-followed-by-decline&#x201d; trend, reflecting phased fluctuations under urbanization. The area of living space rose from 8,570.38 km&#xb2; in 2000 to 9,239.48 km&#xb2; in 2010, then decreased to 8,930.86 km&#xb2; in 2020, resulting in a net increase of 360.48 km&#xb2; over the past 20 years.</p>
<p>Ecological space showed a continuous declining trend. The area of ecological space decreased from 283,546.01 km&#xb2; in 2000 to 279,530.40 km&#xb2; in 2020, a net reduction of 4,015.61 km&#xb2; (<xref ref-type="fig" rid="f2"><bold>Figure&#xa0;2</bold></xref>).</p>
<fig id="f2" position="float">
<label>Figure&#xa0;2</label>
<caption>
<p>Changes in the area of &#x201c;Production&#x2013;Living&#x2013;Ecological Spaces&#x201d; in Heilongjiang Province from 2000 to 2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g002.tif">
<alt-text content-type="machine-generated">Bar chart depicting land use changes from 2000 to 2020. It displays production space as dotted bars, living space as striped bars, and ecological space as solid bars. Living space has the largest area, followed by production space, with ecological space as the smallest across all years.</alt-text>
</graphic>
</fig>
<p>The production function score of land use in Heilongjiang Province increased from 1.17&#xd7;10<sup>6</sup> to 1.19&#xd7;10<sup>6</sup>. The living function score rose from 4.33&#xd7;10<sup>4</sup> to 4.58&#xd7;10<sup>4</sup>. The ecological function score slightly declined, from 1.85&#xd7;10<sup>6</sup> to 1.84&#xd7;10<sup>6</sup> (<xref ref-type="fig" rid="f3"><bold>Figure&#xa0;3</bold></xref>).</p>
<fig id="f3" position="float">
<label>Figure&#xa0;3</label>
<caption>
<p>Temporal distribution of functional scores of Production-Living-Ecological (PLE) spaces in Heilongjiang Province (2000&#x2013;2020).</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g003.tif">
<alt-text content-type="machine-generated">Line graph showing PLE functional scores for Production Space, Living Space, and Ecological Space from 2000 to 2020. Production Space scores are lowest, increasing slightly. Living Space scores remain consistent and mid-range. Ecological Space scores are highest and stable.</alt-text>
</graphic>
</fig>
<p>Based on these temporal variations, ecological space and ecological function of land use in Heilongjiang&#x2019;s major grain-producing areas not only support the production of grain and various agricultural products but also serve as crucial guarantees for constructing a green ecological living environment. Their health and stability directly influence regional agricultural sustainability and residents&#x2019; quality of life.</p>
</sec>
<sec id="s4_1_2">
<label>4.1.2</label>
<title>Spatial variation characteristics</title>
<p>Using ArcGIS zonal statistics and spatial overlay analysis, we observed significant spatial differentiation and dynamic evolution in Heilongjiang&#x2019;s Production-Living-Ecological (PLE) patterns from 2000 to 2020.</p>
<p>High-value production function areas predominantly concentrated in the Songnen and Sanjiang Plains &#x2013; core grain-producing regions with abundant land resources and prominent agricultural capacities (<xref ref-type="fig" rid="f4"><bold>Figure&#xa0;4</bold></xref>). These core zones maintained stable spatial aggregation over 20 years, though peripheral areas experienced slight functional weakening due to urban expansion.</p>
<fig id="f4" position="float">
<label>Figure&#xa0;4</label>
<caption>
<p>Spatial distribution of production space use patterns in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g004.tif">
<alt-text content-type="machine-generated">Map series labeled A, B, and C showing evaluation values of the production function across a geographic area. The gradient from dark to light blue indicates high to low values. Each map includes a north arrow and a scale bar illustrating distances from zero to two hundred kilometers.</alt-text>
</graphic>
</fig>
<p>Living function spaces expanded radially from central cities, primarily around Harbin, Qiqihar, and Daqing metropolitan zones (<xref ref-type="fig" rid="f5"><bold>Figure&#xa0;5</bold></xref>). Higher population density and developed infrastructure enhanced living functions, with western regions showing faster expansion and superior functionality than eastern areas, correlating with economic development and population distribution.</p>
<fig id="f5" position="float">
<label>Figure&#xa0;5</label>
<caption>
<p>Spatial distribution of living space use patterns in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g005.tif">
<alt-text content-type="machine-generated">Three maps labeled A, B, and C show the evaluation value of the living function across a region. They display varying degrees of red shading, with darker red indicating higher values. A scale bar shows distances up to two hundred kilometers, and a north arrow is present on each map. The legend indicates a gradient from high (1) to low (0).</alt-text>
</graphic>
</fig>
<p>Ecological function spaces clustered in the Greater Khingan, Lesser Khingan, and Wandashan Mountains &#x2013; regions with strong ecological regulation capacities despite challenging topography (<xref ref-type="fig" rid="f6"><bold>Figure&#xa0;6</bold></xref>). While the overall ecological pattern remained stable, central urban peripheries witnessed encroachment and functional degradation.</p>
<fig id="f6" position="float">
<label>Figure&#xa0;6</label>
<caption>
<p>Spatial distribution of ecological space use patterns in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g006.tif">
<alt-text content-type="machine-generated">Three maps labeled A, B, and C display the ecological function evaluation value of an area. The maps use shades of green to indicate value, with darker green representing higher values. Each map includes a scale bar showing 0 to 200 kilometers, and a north directional arrow. The legend shows values ranging from low (zero) to high (one).</alt-text>
</graphic>
</fig>
<p>In summary, the spatial dynamics of Heilongjiang&#x2019;s PLE system revealed three co-occurring processes: production space consolidation predominantly concentrated in agricultural core zones like the Songnen and Sanjiang Plains demonstrated functional stability; concurrently, living space expansion radiated outward from urban centers under intensifying urbanization pressures, particularly around major metropolitan areas; meanwhile, ecological space experienced pronounced fragmentation near development zones, though functional stability persisted in remote mountainous regions acting as ecological strongholds.</p>
</sec>
</sec>
<sec id="s4_2">
<label>4.2</label>
<title>Analysis of spatial aggregation characteristics of PLE spaces</title>
<p>Analysis of Moran&#x2019;s I index and Local Indicators of Spatial Association (LISA) cluster analysis reveals that the production-living-ecological (PLE) spaces in Heilongjiang Province between 2000 and 2020 exhibited significant spatial agglomeration. However, the intensity of this agglomeration and its evolutionary trajectory varied considerably across different functional spaces (<xref ref-type="table" rid="T2"><bold>Table&#xa0;2</bold></xref>).</p>
<table-wrap id="T2" position="float">
<label>Table&#xa0;2</label>
<caption>
<p>Changes in global Moran&#x2019;s I Index for " production-living-ecological spaces " in Heilongjiang province from 2000 to 2020.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="middle" rowspan="2" align="center">Year</th>
<th valign="middle" colspan="3" align="center">Moran&#x2019;s I index</th>
</tr>
<tr>
<th valign="middle" align="center">Production space</th>
<th valign="middle" align="center">Living space</th>
<th valign="middle" align="center">Ecological space</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="middle" align="left">2000</td>
<td valign="middle" align="left">0.754439***</td>
<td valign="middle" align="left">0.530564***</td>
<td valign="middle" align="left">0.730692***</td>
</tr>
<tr>
<td valign="middle" align="left">2010</td>
<td valign="middle" align="left">0.756683***</td>
<td valign="middle" align="left">0.555624***</td>
<td valign="middle" align="left">0.732309***</td>
</tr>
<tr>
<td valign="middle" align="left">2020</td>
<td valign="middle" align="left">0.750819***</td>
<td valign="middle" align="left">0.558534***</td>
<td valign="middle" align="left">0.714170***</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn>
<p>*p &lt; 0.05, **p &lt; 0.01, ***p &lt; 0.001.</p></fn>
</table-wrap-foot>
</table-wrap>
<p>The Moran&#x2019;s I index for production space demonstrated relatively minor fluctuations throughout the period. It rose from 0.754439 in 2000 to 0.756683 in 2010, before experiencing a slight decline to 0.750819 in 2020. This trend indicates that while the spatial agglomeration of production functions remained robust, it experienced a subtle weakening over time. High-value agglomeration (H-H zones) were predominantly situated in the Songnen Plain and Sanjiang Plain, regions recognized for their extensive agricultural resources and advanced mechanized farming practices, thereby establishing them as Heilongjiang&#x2019;s primary grain-producing hubs. Conversely, low-value agglomeration (L-L zones) were concentrated in the Greater Khingan Range to the north and the wetland fringe areas to the south. These locations are characterized by challenging geographical conditions and stringent ecological protection regulations, resulting in comparatively less pronounced production functions (<xref ref-type="fig" rid="f7"><bold>Figure&#xa0;7</bold></xref>).</p>
<fig id="f7" position="float">
<label>Figure&#xa0;7</label>
<caption>
<p>LISA cluster types of production space in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g007.tif">
<alt-text content-type="machine-generated">Maps labeled A, B, and C display a geographic area with color-coded sections in red and blue. The legend indicates categories: &#x201c;Do not display,&#x201d; H-H, H-L, L-H, L-L. Each map includes a scale and compass rose, illustrating variations in data across different scenarios.</alt-text>
</graphic>
</fig>
<p>The agglomeration patterns of living space exhibited a more consistent evolution. The Moran&#x2019;s I index for living space increased from 0.530564 in 2000 to 0.558534 in 2020, indicating a gradual upward trend and a moderate enhancement in spatial concentration (<xref ref-type="table" rid="T2"><bold>Table&#xa0;2</bold></xref>). High-value agglomeration areas (H-H zones) were primarily clustered in major urban centers such as Harbin, Qiqihar, and Daqing, as well as their adjacent vicinities. This distribution underscores the intensifying influence of urbanization on the development of living spaces. Areas at the urban expansion fringe displayed a high-low agglomeration (H-L zone), while rural regions, characterized by weaker living space functions, presented as low-value agglomeration (L-L zones) (<xref ref-type="fig" rid="f8"><bold>Figure&#xa0;8</bold></xref>).</p>
<fig id="f8" position="float">
<label>Figure&#xa0;8</label>
<caption>
<p>LISA cluster types of living space in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g008.tif">
<alt-text content-type="machine-generated">Three maps labeled A, B, and C display a region with red dots representing data points. Each map uses a legend indicating categories: H-H (high-high), H-L (high-low), and L-H (low-high). The maps include scale bars ranging from zero to two hundred kilometers and indicate north orientation.</alt-text>
</graphic>
</fig>
<p>The Moran&#x2019;s I index for ecological space initially increased from 0.730692 in 2000 to 0.732309 in 2010. However, it subsequently decreased to 0.714170 by 2020 (<xref ref-type="table" rid="T2"><bold>Table&#xa0;2</bold></xref>), suggesting a trend towards weakening spatial agglomeration and increasing dispersion. High-value agglomeration areas (H-H zones) were mainly located in the Greater Khingan Range, Lesser Khingan Range, and designated wetland protection areas within the Sanjiang Plain. These concentrations are attributed to the implementation of strict ecological protection policies and favorable natural topography. In contrast, low-value agglomeration areas (L-L zones) were observed in the intensively farmed Songnen Plain and in regions undergoing urban expansion. This pattern reflects the considerable pressure exerted on ecological spaces by the encroachment of living and production activities, leading to a reduction in ecological connectivity (<xref ref-type="fig" rid="f9"><bold>Figure&#xa0;9</bold></xref>).</p>
<fig id="f9" position="float">
<label>Figure&#xa0;9</label>
<caption>
<p>LISA cluster types of ecological space in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g009.tif">
<alt-text content-type="machine-generated">Three maps labeled A, B, and C depict a region with areas marked in red and blue. The legend indicates categories: &#x201c;Do not display,&#x201d; &#x201c;H-H,&#x201d; &#x201c;H-L,&#x201d; &#x201c;L-H,&#x201d; and &#x201c;L-L.&#x201d; Scale indicates 0 to 200 kilometers. Red areas are more concentrated in the northern parts compared to blue.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s4_3">
<label>4.3</label>
<title>Analysis of structural transition of land-use in PLE spaces</title>
<p>From 2000 to 2020, significant dynamic shifts occurred in the structure of the production-living-ecological (PLE) spaces in Heilongjiang Province, with functional flows between production, living, and ecological spaces exhibiting divergent trends and spatial distribution characteristics.</p>
<p>Analysis of land use data revealed that production space continued to expand (<xref ref-type="fig" rid="f10"><bold>Figure&#xa0;10</bold></xref>), primarily concentrating in areas with high agricultural development intensity, such as core agricultural regions around Harbin and Qiqihar, and the Sanjiang Plain. The expansion of production space was largely a conversion from ecological space (<xref ref-type="fig" rid="f11"><bold>Figure&#xa0;11</bold></xref>), a phenomenon particularly pronounced in the central Songnen Plain and the southeastern Sanjiang Plain, characterized by contiguous expansion of cultivated land. This reflects the dual drivers of enhanced agricultural functions and urban development on production space.</p>
<fig id="f10" position="float">
<label>Figure&#xa0;10</label>
<caption>
<p>Sankey diagram of "Production-Living-Ecological" land use changes in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g010.tif">
<alt-text content-type="machine-generated">Sankey diagram displaying changes in land use from 2000 to 2020 across three categories: production space, living space, and ecological space. Production space increases slightly from 160,284.43 to 163,910.28 square kilometers. Living space also increases from 8,570.38 to 8,930.86 square kilometers. Ecological space decreases from 283,546.01 to 279,530.40 square kilometers.</alt-text>
</graphic>
</fig>
<fig id="f11" position="float">
<label>Figure&#xa0;11</label>
<caption>
<p>Spatial distribution of land use transitions among "Production-Living-Ecological" spaces in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g011.tif">
<alt-text content-type="machine-generated">Two maps labeled A and B show land use transformations within a region. Both maps use color coding to indicate changes: red for transforming production space into living space, pink for production to ecological space, blue for living to production space, teal for living space to ecological space, dark green for ecological to production space, and light green for ecological to living space. A scale and compass are present, indicating north and distances up to 165 kilometers. The maps illustrate spatial distributions of these transformations.</alt-text>
</graphic>
</fig>
<p>Living space, however, initially expanded before experiencing a decline (<xref ref-type="fig" rid="f10"><bold>Figure&#xa0;10</bold></xref>). Spatially, the expansion of living space was concentrated in cities such as Harbin, Daqing, and Jiamusi, and their surrounding areas (<xref ref-type="fig" rid="f11"><bold>Figure&#xa0;11</bold></xref>). The expansion of living space primarily originated from the transfer of ecological space, a trend that was more evident between 2000 and 2010, manifesting as the gradual replacement of ecological land with living and construction land around urban peripheries.</p>
<p>The changes in ecological space were the most significant, with a net decrease of 4015.61 km&#xb2; over the 20-year period (<xref ref-type="fig" rid="f10"><bold>Figure&#xa0;10</bold></xref>). Areas from which ecological space was transferred were mainly concentrated in regions with high intensity of agricultural development and urban expansion, particularly in the central-southern Songnen Plain and the eastern Sanjiang Plain (<xref ref-type="fig" rid="f11"><bold>Figure&#xa0;11</bold></xref>). In these areas, the conversion of ecological functional land, such as wetlands and forests, into production space (e.g., cultivated land) and living space (e.g., urban and rural construction land) was evident. The conversion of ecological space to production and living space occurred in both phases, but it was more pronounced between 2010 and 2020, indicating limited policy intervention effectiveness and continued pressure on ecological space.</p>
<p>From the perspective of temporal and spatial characteristics, the structure of Heilongjiang Province&#x2019;s &#x201c;three spaces&#x201d; underwent a continuous evolution from ecological to production and living functions between 2000 and 2020. Specifically, the structural changes were relatively gradual during the 2000&#x2013;2010 period, with the transfer from ecological to living space being dominant. In contrast, during the 2010&#x2013;2020 period, the rate of transfer from ecological to production space accelerated, while living space exhibited a complex pattern of coexisting contraction and outward expansion. This trend is primarily driven by multiple factors such as regional economic development, urbanization processes, and agricultural expansion, reflecting the long-term risk of ecological space being squeezed during the restructuring of &#x201c;three spaces.&#x201d;</p>
</sec>
<sec id="s4_4">
<label>4.4</label>
<title>Analysis of coupling coordination degree of PLE spaces</title>
<sec id="s4_4_1">
<label>4.4.1</label>
<title>Overall spatiotemporal evolution of coupling coordination degree</title>
<p>Based on the analysis of the functions of the production-living-ecological spaces within each geographical grid between 2000 and 2020, the coupling coordination degree of these spaces in Heilongjiang Province exhibits distinct spatial differentiation characteristics.</p>
<p>From an overall perspective, areas with high coordination are predominantly concentrated in the central and southern regions of the Songnen Plain and the Sanjiang Plain. These areas are primarily agricultural, with production space taking precedence. Intense agricultural activity coexists with concentrated living spaces that possess well-developed infrastructure, forming a pattern of highly integrated production and living spaces.</p>
<p>Moderately and weakly coordinated areas are widely distributed across most of the province, representing the dominant type of coupling coordination degree in Heilongjiang. In contrast, areas with low or even disordered coordination are mainly situated in the northern Greater Xing&#x2019;an Mountains, Lesser Xing&#x2019;an Mountains, and the southeastern Wandashan region. In these areas, ecological space prevails, and production and living spaces are noticeably insufficient, resulting in poorer integration of the production-living-ecological spaces and overall lower coordination levels.</p>
<p>In terms of temporal evolution, from 2000 to 2020, the coupling coordination degree of the production-living-ecological spaces in Heilongjiang Province generally demonstrated a slow upward trend, with coordination levels gradually improving (<xref ref-type="fig" rid="f12"><bold>Figure&#xa0;12</bold></xref>). Between 2000 and 2010, the number of moderately and highly coordinated areas progressively increased, and the coordination pattern remained relatively stable. During the 2010&#x2013;2020 period, the trend of improvement became more pronounced, particularly in agricultural regions such as the Songnen Plain and Sanjiang Plain, where highly coordinated areas expanded further. Concurrently, coordination levels in the northern and eastern regions, characterized by dominant ecological functions, remained relatively stable, exhibiting no significant fluctuations. This indicates the relative lag in the integration of production-living-ecological spaces within ecologically dominant areas.</p>
<fig id="f12" position="float">
<label>Figure&#xa0;12</label>
<caption>
<p>Spatial distribution of coupling coordination degree of "Production-Living-Ecological" spaces in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g012.tif">
<alt-text content-type="machine-generated">Three maps labeled A, B, and C depict levels of land coordination within a region. Each map uses color coding: white for serious imbalance, light yellow for mild coordination, orange for moderate coordination, and red for highly coordinated areas. A scale indicates distances from zero to two hundred kilometers.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s4_4_2">
<label>4.4.2</label>
<title>Evolution characteristics of pairwise coupling coordination degrees among PLE functions</title>
<p>To further elucidate the coupling coordination relationships among the functions of the production-living-ecological spaces, this study analyzes the evolutionary characteristics of three pairwise coupling coordination degrees: production&#x2013;living, production&#x2013;ecology, and living&#x2013;ecology. Following the classification standards for coupling coordination degrees, the proportions of different level intervals for each year were calculated, and the evolution curves of the pairwise coupling coordination degrees for the production-living-ecological spaces in Heilongjiang Province in 2000, 2010, and 2020 were fitted (<xref ref-type="fig" rid="f13"><bold>Figure&#xa0;13</bold></xref>).</p>
<fig id="f13" position="float">
<label>Figure&#xa0;13</label>
<caption>
<p>Evolution curves of pairwise coupling coordination degrees among "Production-Living-Ecological" spaces in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g013.tif">
<alt-text content-type="machine-generated">Line graphs labeled A, B, and C show the percentage distribution across coupling coordination degrees (CCD) for the years 2000, 2010, and 2020. Graph A shows a decrease from 60% to nearly 0% as CCD increases. Graph B shows a curve peaking around 0.6 to 0.8 CCD with percentages increasing up to 40%. Graph C mirrors A with a declining trend from 60% to almost 0% as CCD increases. Data points are marked with different shapes for each year.</alt-text>
</graphic>
</fig>
<p>The production&#x2013;living space coupling coordination degree exhibited the lowest overall level (<xref ref-type="fig" rid="f13"><bold>Figure&#xa0;13A</bold></xref>). From 2000 to 2020, it was predominantly concentrated in low-level intervals (0&#x2013;0.2 and 0.2&#x2013;0.4). Although there was a slight increase in high-level intervals in 2010 and 2020, the overall change was limited. This suggests that the functional integration between living and production spaces remains weak, necessitating a strengthening of their spatial coordination.</p>
<p>The production&#x2013;ecology space coupling coordination degree was the highest (<xref ref-type="fig" rid="f13"><bold>Figure&#xa0;13B</bold></xref>), predominantly falling within the intervals of 0.6&#x2013;0.8 and 0.8&#x2013;1. This indicates a steady enhancement in the synergy between agricultural production and ecological protection in Heilongjiang Province, leading to the gradual formation of an ecological agricultural pattern.</p>
<p>The living&#x2013;ecology space coupling coordination degree was at a moderate level (<xref ref-type="fig" rid="f13"><bold>Figure&#xa0;13C</bold></xref>). While it was primarily in low-level intervals in 2000, high-level intervals had increased by 2020. Overall, the coupling coordination degree remained low, reflecting the need for further spatial integration of urban and rural living functions with ecological functions to improve the green living environment.</p>
<p>The pairwise coupling coordination relationships among the production-living-ecological spaces in Heilongjiang Province demonstrate significant structural differences. The highest production&#x2013;ecology coupling coordination degree reflects a robust synergy between agricultural production and ecological protection, serving as the core driving force for the efficient integration of these spaces in major grain-producing areas. The living&#x2013;ecology space coupling coordination degree was predominantly at a low level, indicating that living functions in urban and rural areas and ecological space require gradual achievement of coordinated coexistence. The production&#x2013;living space coupling coordination degree remained relatively low, characterized by weak spatial functional integration, highlighting the urgent need to optimize land use structure and improve infrastructure to further promote their coordinated spatial development.</p>
</sec>
<sec id="s4_4_3">
<label>4.4.3</label>
<title>Migration trends of center of gravity of production-living-ecological spaces coupling coordination degree</title>
<p>To further quantify and dynamicize the spatial synergistic effects of production-living-ecological spaces, this study employs a barycenter migration model of coupling coordination degree. The temporal evolution of the barycenter of this coordination was analyzed for Heilongjiang Province between 2000 and 2020. The results reveal a phased characteristic of the overall barycenter, exhibiting a pattern of initial northward migration followed by a subsequent southward shift (<xref ref-type="fig" rid="f14"><bold>Figure&#xa0;14</bold></xref>).</p>
<fig id="f14" position="float">
<label>Figure&#xa0;14</label>
<caption>
<p>The center of gravity of migration of coupling coordination degree for "Production-Living-Ecological" spaces in Heilongjiang Province, 2000&#x2013;2020.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-13-1635979-g014.tif">
<alt-text content-type="machine-generated">Map depicting three points with coordinates and years. Point labeled 2000 at coordinates 127&#xb0;38'6"E, 46&#xb0;50'10"N, 2010 at 127&#xb0;41'5"E, 46&#xb0;54'22"N, and 2020 at 127&#xb0;38'41"E, 46&#xb0;51'58"N. Lines connect the points sequentially. Grid shows latitude and longitude markings.</alt-text>
</graphic>
</fig>
<p>During the period of 2000&#x2013;2010, the barycenter of coupling coordination degree migrated from (127&#xb0;38&#x2019;6&#x201d;E, 46&#xb0;50&#x2019;10&#x201d;N) to (127&#xb0;41&#x2019;5&#x201d;E, 46&#xb0;54&#x2019;22&#x201d;N). This represented an overall eastward and northward displacement of approximately 8.64 kilometers, averaging 0.86 kilometers per year. This movement indicates a significant enhancement in coupling coordination degree within the northern regions during this phase. Such improvement can likely be attributed to the initial efficacy of ecological protection policies and the sustained stability of ecologically functional advantage zones.</p>
<p>Subsequently, from 2010 to 2020, the barycenter experienced a southwestward regression to (127&#xb0;38&#x2019;41&#x201d;E, 46&#xb0;51&#x2019;58&#x201d;N), covering a migration distance of approximately 5.38 kilometers. The magnitude of this migration was notably less than that of the preceding period. This suggests that while coordination degrees in southern agricultural areas, such as the Songnen Plain, saw improvement, the dominant influence of the northern regions on the barycenter&#x2019;s position persisted.</p>
<p>In summation, the trajectory of the barycenter&#x2019;s migration illustrates a dynamic process wherein the coupling coordination pattern of production-living-ecological spaces initially optimized from south to north before undergoing a slight southward adjustment. This evolution mirrors the changing regional coordination within Heilongjiang Province as it navigated advancements in ecological protection, agricultural development, and urbanization. Furthermore, this trend underscores that the spatial competition between production and ecological spaces continues to be a critical constraint on the enhancement of overall coupling coordination.</p>
</sec>
</sec>
</sec>
<sec id="s5" sec-type="discussion">
<label>5</label>
<title>Discussion</title>
<p>This study reveals a profound intrinsic trade-off inherent in the evolution of the &#x201c;Production-Living-Ecological Spaces&#x201d; (PLES) in Heilongjiang Province. While previous research has predominantly highlighted the expansionary trend of production spaces in major grain-producing regions (<xref ref-type="bibr" rid="B17">Li and Fang, 2016</xref>; <xref ref-type="bibr" rid="B26">Meng et&#xa0;al., 2022</xref>; <xref ref-type="bibr" rid="B19">Li et&#xa0;al., 2023</xref>; <xref ref-type="bibr" rid="B46">Zhou et&#xa0;al., 2024</xref>), this study, through meticulous delineation of land use transition pathways, further demonstrates that such expansion has primarily occurred at the expense of ecological spaces within core agricultural areas, notably the Songnen Plain and Sanjiang Plain. This finding establishes a direct link between the macro-level national food security strategy and micro-level land use changes, clearly identifying a typical &#x201c;eco-space-for-production&#x201d; model prevalent in local practices. Although this model has effectively supported grain yields in the short term, our coupled coordination degree analysis also warns that it is undermining the long-term resilience of regional ecosystems, representing a core risk to regional sustainable development identified herein.</p>
<p>The tension between production and ecology outlined above is deeply rooted in the traditional &#x201c;grain-only approach&#x201d;. In contrast, the &#x201c;Big Food Vision&#x201d; proposed by the Chinese government (General Office of the State Council, 2024) provides a novel theoretical perspective and solution. The essence of this approach lies in transcending the traditional concept equating &#x201c;food&#x201d; solely with &#x201c;grain,&#x201d; expanding food sources from reliance on cultivated land alone to encompass the entire territorial space (including forests, grasslands, and water bodies), thereby constructing a diversified food supply system. This theory aptly explains a key finding of this study: the persistent suboptimal functional coupling between &#x201c;production&#x201d; and &#x201c;living&#x201d; functions in Heilongjiang Province is largely attributable to the high degree of fixation of the production function on cultivated land, while the considerable economic potential inherent in vast ecological spaces (e.g., forest land, wetlands) remains largely untapped. This profoundly reveals that excessive dependence on the output from a single land type (cultivated land) not only encroaches upon ecological space but also proven ineffective in driving diversified development and enhancing resident well-being in rural areas.</p>
<p>The findings of this study also engage effectively with existing research while advancing it further. For instance, while <xref ref-type="bibr" rid="B25">Mao and Jia (2022)</xref> noted the intensifying landscape fragmentation of regional agricultural and forestry land, our research, from a functional coupling perspective, uncovers the underlying functional root cause of this spatial fragmentation&#x2014;namely, the lack of synergistic effects resulting from the simplification of land functions. Concurrently, <xref ref-type="bibr" rid="B18">Li et al. (2025)</xref> emphasize that future improvements in land habitat quality depend on strict ecological protection. This study provides a crucial supplement to this view: sole reliance on &#x201c;passive protection&#x201d; may prove unsustainable; greater emphasis needs to be placed on &#x201c;proactive integration&#x201d; guided by the &#x201c; Big Food Vision.&#x201d; This entails developing eco-friendly industries to endogenously transform ecological advantages into economic benefits, thereby fundamentally alleviating the long-standing conflict between conservation and development. This paradigm shift from &#x201c;protection&#x201d; to &#x201c;integration&#x201d; represents the core concept that this study seeks to advocate at both theoretical and policy levels.</p>
<p>Building upon the preceding discussion, optimizing the &#x201c;Production-Living-Ecological Space&#x201d; (PLES) pattern in Heilongjiang Province necessitates a suite of systematic strategies that integrate regional characteristics with a global perspective. At the regional level, differentiated spatial governance should be implemented. In the Songnen Plain, where conflicts between production and ecology are acute, the establishment of integrated &#x201c;farmland-ecological corridor&#x201d; systems is required, coupled with the linkage of ecological compensation mechanisms to incentives for major grain-producing areas. In rural areas exhibiting weak production-living coupling, beyond utilizing the &#x201c;Diversified Food Systems&#x201d; concept to guide industrial development and foster new formats like eco-agriculture, understory economy, and rural tourism, further optimization of the land use structure is essential. This optimization should prioritize the promotion of scaled development among agricultural operators to achieve the <italic>in-situ</italic> integration of production and living functions. Here, &#x2018;scaled development&#x2019; specifically emphasizes achieving a &#x2018;functional moderate scale&#x2019;. This logic operates through three mechanisms: 1) Enhancement of production efficiency and specialization: The consolidation of fragmented farmland into relatively concentrated operational units can significantly improve land use efficiency, providing the foundation for the adoption of advanced agricultural machinery and the dissemination of efficient production technologies; 2) Strengthening of livelihood support capacity: Moderate expansion of operational scale can generate stronger economic agglomeration effects, accumulating more funds for infrastructure development (e.g., roads, water supply, networks) and public services (e.g., education, healthcare) in rural areas; 3) Promotion of synergistic integration of production and living spaces: Once agricultural production reaches a certain scale with enhanced efficiency, its surplus products, by-products, or generated ecosystem services (e.g., environmentally friendly farming practices) can be more effectively converted into economic income and resources for improving the livelihoods of rural residents.</p>
<p>More significantly, the Heilongjiang case offers universal policy insights for other major global grain-producing regions&#x2014;such as the US Corn Belt or Brazil&#x2019;s Cerrado savanna, which face similar pressures of agricultural expansion and ecological degradation (<xref ref-type="bibr" rid="B8">Foley, 2005</xref>). The core lies in shifting land use from &#x201c;single-function maximization&#x201d; towards &#x201c;multifunctional synergistic optimization&#x201d;. Globally applicable strategies include: 1) Implementation of Nature-based Solutions (NbS), embedding ecological infrastructure within agricultural landscapes to enhance systemic resilience; 2) Establishment of policy frameworks capable of accounting for Ecosystem Service Value (ESV), making the contributions of ecological conservation &#x201c;visible&#x201d; in economic decision-making; 3) Promotion of diversified food systems to address the dual risks of global climate change and market volatility. These strategies collectively point towards a sustainable future: safeguarding global food supply while maintaining the ecological health and community prosperity of critical agricultural regions.</p>
<p>It should be noted that while the macro-scale trends and spatial patterns revealed by this study, based on 30m resolution remote sensing data, are clear, the resolution may mask micro-scale land function variations and dynamic changes to some extent. Future research could refine the understanding of functional evolution and synergistic optimization mechanisms at the village level by integrating higher-resolution data or field surveys.</p>
</sec>
<sec id="s6" sec-type="conclusions">
<label>6</label>
<title>Conclusion</title>
<p>This study systematically elucidates the spatiotemporal evolution patterns and coupling coordination characteristics of the &#x201c;Production-Living-Ecological Space&#x201d; (PLES) in Heilongjiang Province&#x2014;a representative major grain-producing area in China&#x2014;during the 2000&#x2013;2020 period. The principal findings are summarized as follows:</p>
<list list-type="order">
<list-item>
<p>Pattern Evolution and Intrinsic Trade-offs: Production space has undergone continuous expansion at the expense of critical ecological spaces, intensifying functional tensions between these two domains. Concurrently, living space demonstrates distinct enclave-style growth around central urban cores, exhibiting insufficient spatial integration with extensive production areas.</p></list-item>
<list-item>
<p>Functional Coupling and Structural Imbalance: Significant structural disparities are observed in PLES coupling coordination levels, manifested through relatively high production-ecological coordination juxtaposed with persistently low production-living coordination. This structural imbalance constitutes a fundamental constraint on regional holistic development.</p></list-item>
<list-item>
<p>Gravity Shift and Dynamic Transition: The trajectory of coupling coordination gravity&#x2014;characterized by initial northward displacement followed by southward migration&#x2014;provides clear evidence of a historic transition in regional development dynamics, shifting from ecological conservation imperatives toward agricultural production dominance.</p></list-item>
</list>
<p>The core contribution of this research resides in its quantitative revelation of profound spatial-functional trade-offs within localized systems under national food security strategies, complemented by the innovative application of the &#x201c;Big Food Vision&#x201d; concept as a theoretical framework for reconciling PLES conflicts. Our findings underscore the imperative for a paradigm shift in land policies across grain-producing regions: transitioning from a singular yield-maximization orientation toward an integrated governance model that synergistically coordinates production, livelihood, and ecological functions. This investigation not only holds significant practical implications for China&#x2019;s territorial spatial planning but also offers valuable empirical insights for achieving sustainable development objectives in global agricultural regions confronting analogous challenges.</p>
</sec>
</body>
<back>
<sec id="s7" sec-type="data-availability">
<title>Data availability statement</title>
<p>The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.</p></sec>
<sec id="s8" sec-type="author-contributions">
<title>Author contributions</title>
<p>SG: Funding acquisition, Conceptualization, Formal Analysis, Writing &#x2013; review &amp; editing, Methodology, Writing &#x2013; original draft, Data curation, Visualization. YM: Writing &#x2013; original draft, Investigation, Software, Supervision, Resources, Writing &#x2013; review &amp; editing, Project administration, Validation.</p></sec>
<sec id="s10" sec-type="COI-statement">
<title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p></sec>
<sec id="s11" sec-type="ai-statement">
<title>Generative AI statement</title>
<p>The author(s) declare that no Generative AI was used in the creation of this manuscript.</p>
<p>Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.</p></sec>
<sec id="s12" sec-type="disclaimer">
<title>Publisher&#x2019;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p></sec>
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