Majestic conifers around the world mostly occupy temperate, boreal, and subtropical climates (1). Global populations of these long-lived species are facing serious threats to their existence mostly due to anthropogenic activities and climate change (2). Among these conifers, Pinus geradiana Wallichex. D. Don forests are extremely important. They are native to the Western Himalayas and are distributed in eastern Afghanistan, southern Xizang (Tibet) in China, Jammu and Kashmir in India, and northern Pakistan (Shalizi et al., 2018; Urooj, 2019). These forests are extremely valuable, having key socioeconomic importance. However, rapid exploitation of these forests is gradually leading them toward extinction from their original habitat (Urooj and Jabeen, 2015; Aziz et al., 2018; Shalizi et al., 2018). Globally, P. gerardina forests are native to South East Asia, West Asia, and in the states of Central Asia (Shalizi and Khurram, 2016; Urooj, 2019). Pakistan is home to one of the largest P. gerardiana forest stands in the world (Print et al., 2015; Urooj and Jabeen, 2015; Urooj et al., 2020). These forests are extensively located in the Sulieman and Hindu Kush mountain ranges in the west (Khyber Pakhtun Khwa and Baluchistan) and north (Kashmir and Gilgit Baltistan) of the country (Print et al., 2015; Urooj and Jabeen, 2015; Urooj, 2019). P. gerardiana forests are major economic players in the region, generating a hefty revenue of 13 million USD annually (Haq et al., 2013; Print et al., 2015; Urooj, 2019). These forests are responsible for sustaining rural livelihoods in the form of employment and businesses (Shalizi et al., 2018; Alami and Mousavi, 2020; Rahimzadeh, 2020; Urooj et al., 2020; Alami and Mousavi, 2021). Forest understory vegetation is regarded as an ecological indicator due to its quick response to changing environmental conditions (Von Oheimb and Härdtle, 2009). As such, understory vegetation can serve as an important indicator of species composition in a forest. The understory layer is known to affect the establishment, survival rate, and adaptability of plant species, including soil physicochemical properties such as nutrient content, pH, and moisture (Dzwonko and Gawroński, 2002; Tinya et al., 2009). Understory medicinal plant species are an important component of forest communities’ livelihood, playing a vital role in providing subsistence and cash income to a large part of the world’s population, particularly in developing countries (Sher et al., 2014; Muhammad et al., 2019).

Studies have depicted the importance of understory species among the people living in the forest vicinity in the north of Pakistan (Kayani et al., 2014; Sher et al., 2014, 2016). Muhammad et al. (2019) displayed the inventory of medicinal plants in the dry and moist temperate forests of Kashmir. The authors depicted a large dependence of local communities upon these medicinal plants. Moreover, majority of people in these communities were dependent upon medicinal plant collection, processing, and marketing for sustaining their livelihood (Zubair et al., 2019). Understory species are affected by structural changes in the forests resulting from anthropogenic disturbances and overexploitation (Vellend et al., 2006; Liira et al., 2007; Wyatt and Silman, 2010). Such changes in forest structure may even lead to the local extinction of certain species (Vellend et al., 2006).

Slope aspect remains pivotal in affecting plant communities in terms of their characteristics, functional groups, and aspect orientation (Zhang et al., 2022). Slope aspect is instrumental in changing solar radiation distribution patterns, thereby altering soil temperature and moisture levels (Burnett et al., 2008). Thus, slope aspect affects almost all vegetation properties, importantly, species composition, photosynthetic efficiency, species diversity, cover, nutritional dynamics, and, in turn, productivity (Kakembo et al., 2007; Ortiz-Pulido and Pavon, 2010; Sharm et al., 2010; Aimme and Normaniza, 2015).

In Pakistan, the dependence of people on pine forest resources has continued to rise in the last few decades. This is mostly due to the increasing population inhabiting previously untouched forest ecosystems (Ali et al., 2005). Pakistan, with 260 km² of P. gerardina forest, experiences unsustainable overexploitation of resources. This not only leads to decreased production but aids deforestation. In these mountain ranges, most of the P. gerardiana forests are exploited by local people for pine nut collection and medicinal plant collection (Alami and Mousavi, 2020). Non-timber forest products (NTFPs) collected from the understory of these forests play a significant role in the socioeconomics of the forest community. But unsustainable and continuous resource exploitation coupled with deforestation mostly leading to settlements for new communities are having adverse effects on the understory vegetation that has been poorly explored by the scientific community of this region (Vellend et al., 2006; Urooj and Jabeen, 2015; Aziz et al., 2018). Hence, there is need of a study to measure the resources in the understory layer of these forests and to observe their relationship with changing land-use patterns (Hayat et al., 2021). The current study will provide crucial knowledge regarding the suitability of the ecosystem, especially in terms of habitat management.

There are already extensive studies reporting the benefits and importance of pine nut forests regarding its top story. But there are very few studies exploring the ecological, ethnological, and economic importance of the understory of Pinus spp. forests (López-Marcos et al., 2019, 2020). It is extremely crucial that the understory vegetation of pine forests are studied, and in particular P. gerardina. This would help in effective forest management and resource sustainability, thus ensuring the stable livelihood of the inhabitants dependent upon them (Mölder et al., 2008; Muhammad Azam Khan et al., 2010; Haq et al., 2011). Researching the understory vegetation of these forests can help in determining the vital role that it plays in nutrient cycling and carbon sequestration, thus influencing the overall ecosystem’s health and resilience (Ou et al., 2020; Ali and Khan, 2022). More importantly studying the diversity and distribution of understory vegetation can help in identifying invasive species, promoting biodiversity conservation, and mitigating the risk of pest and disease outbreaks (Ullah et al., 2013; Zilliox and Gosselin, 2014).

In this study, we aim to explore the understory vegetation of P. gerardiana forests in South Waziristan Agency under different aspects (northern and southern). There are limited cross-sectional studies and systematic documentation highlighting the understory vegetation density concerning various aspects and the use of different plant species in Pakistan (Liira et al., 2007; Wyatt and Silman, 2010; Ali and Khan, 2022). The present study introduces an avenue of knowledge about the role of different aspects influencing the distribution, abundance of understory vegetation, and its diversity for this precious forest resource. Since aspects were the focus of study across which different vegetation parameters were assessed, therefore, the core objectives of the study was to assess species diversity across different aspects (northern and southern) of the understory vegetation in P. gerardiana stands in the dry temperate forest of South Waziristan, Khyber Pakhtunkhwa (KPK), Pakistan.

The results showed the understory portion of the forest to have considerable biodiversity. Our research study depicted that the P. gerardiana forest of South Waziristan Agency has diverse understory vegetation. The understory is enriched with different medicinal plants that are used for various purposes including food and fodder. These plants play a key role in the livelihood of the local communities using them in herbal medicines as well as the functioning of the forest (Chidumayo and Gumbo, 2010). Most of the plants were used for medicinal need. The current research study was similar to the research work of Qasim et al. (2013) depicting that most of the plants in the Himalayan range were being used for medicinal purposes. Vegetation density came out to be moderate in the understudied area. Qasim et al. (2013) observed similar results depicting low species diversity in P. gerardiana stands. Results depicted homogenous variance in understory species composition on the northern and southern aspects of the study sites. Similarly, various researchers have observed variations in understory composition and structure according to the aspects (Mishra et al., 2004; Mölder et al., 2008).

The maximum biodiversity was found on the southern aspect of the study site. The area was open in canopy cover which provided a suitable environment for different medicinal plants (Qasim et al., 2013; Khel et al., 2022). Similar observations were found by Adnan and Hölscher (2012) at Ayubia National Park of Khyber Pakhtoon Khwa, where they perceived that the decrease in understory plants, herbs, and shrubs was due to the dense canopy cover of overstorey vegetation. Zilliox and Gosselin (2014) concluded that northern aspects showed minimum abundance of understory vegetation because of the closed canopy and less availability of sunlight, moisture, and nutrients for the understory plants and grasses. Similar observations were found by Whitmore (1978), wherein forest cover remained instrumental in affecting the vegetation underneath it. Similar outcomes were perceived by Sagar et al. (2008), in which they exhibited that the areas with sparse canopy cover had high understory plant cover. It was observed that the evergreen forest closed canopy had less understory biodiversity. The study noted that understory vegetation is completely dependent on the overstory of the forest trees including pure and mixed forests.

Aspect and canopy affected the diversity, density, and cover of understory vegetation of the study site, as endorsed in various similar studies (Khan et al., 2012). Overall diversity of the understory vegetation in the study area was on the lower side. This is coherent with similar studies conducted in these areas (Khan et al., 2011; Zubair et al., 2021; Ali et al., 2022). Studies in the pine nut forests of Pakistan and Afghanistan have usually depicted lower understory vegetation diversity (Khan et al., 2011; Rahman et al., 2017; Luintel et al., 2018; Ali et al., 2022; Prakash et al., 2023). However, the pine nut forests of China, India, and other regions have shown higher diversity of understory plant species compared with understory vegetation diversity of pine forests of the area under study (Huo et al., 2014; Su and Lu, 2020; Aqeel et al., 2023; Prakash et al., 2023). The study depicted a lower density and frequency of plant species in both study areas. This is mostly related to the vegetation damaging effects caused by overgrazing, unsustainable medicinal/edible plant collection, and deforestation, as reported in various studies (Shinwari and Qaiser, 2011; Shalizi et al., 2018; Hussein et al., 2021; Khan et al., 2021).

The majority of these plants are available year round and the local communities use them for their subsistence (Farooq et al., 2012; ANG et al., 2014; Aziz et al., 2016). The higher composition of species diversity and dominance on the southern aspect compared with the northern aspect was shown by the rank abundance curve highlighting the richness of S. glutinosa and S. nubicola species. Similar results were observed by Ali et al. (2007), which depicted that there was a slight decrease in the species abundance of northern aspects. Promis et al. (2012) observed similar results, stating that the areas with dense vegetation showed less understory plants. The aspects with a decrease in grazing patterns and partially closed forest cover (southern aspects) had high understory vegetation including medicinal plants. Similar results were observed by Zubair et al. (2021), stating that the spots with medium canopy cover resulted in high understory vegetation. The research study results were obtained by appropriate samples collection as justified in the rarefaction curves. The curves were used in data to overcome difficulties and interference often experienced during counting and relating to taxon richness. (Gotelli and Colwell, 2001). The availability of plants across time is a critical factor for observing richness and abundance (Wulf and Naaf, 2009; Mestre et al., 2017). Moreover, plants grown under conditions of ample light and space are more abundant compared with plants dispersed under dense forests (Walker et al., 1999). Likewise, species tend to be more diverse and richer in their flora when the available forest condition is either termed as open canopy or undisturbed partial canopy cover(Hamilton, 2004; Promis et al., 2012).

The P. gerardiana forests of Pakistan are rapidly degrading due to the overexploitation of pine nuts, unsustainable collection of medicinal/edible plant species, and continuous deforestation (Urooj et al., 2020; Khan et al., 2021). These factors not only alter the structure and functioning of the forest but also increase soil erosion events and reduce nutrients availability (Mölder et al., 2008; Qasim et al., 2013; Hussein et al., 2021). Our study depicts the lower density, cover, and diversity of important medicinal/edible plant species on the northern and southern aspects. This indicates a crucial restoration hotspot that harbors endangered species whose recovery could benefit from effective forest landscape rehabilitation and conservation practices (Höhl et al., 2020; De Matos et al., 2021).

Many previous studies have indicated direct links between diversity, composition, and the structure of understory vegetation on the functioning and provisioning of the forest (Ou et al., 2020). The quantitative inventory of the understory vegetation clearly translates as a warning of potential irreversible degradation (Xie et al., 2021). Building on the results of such vegetation surveys, it is important that we engage government departments and non-governmental organizations to take part in conservation practices utilizing wider and systematic formal monitoring activities, since forest communities have minimum input in the management and conservation of forest resources (Tabassum, 2020). This emphasized the need to understand policy and practice of forest landscape restoration (FLR) in meeting local needs and livelihoods for sustainable management of forest resources, though important, yet is important (Mansourian et al., 2020; Tabassum, 2020). Various global studies have indicated that different resource management endeavors with minimum integration of vegetation surveys in terms of monitoring usually lead to poor management and low rehabilitation success (Chazdon, 2019; Mansourian et al., 2020). Through this study, there is an opportunity for considering the incorporation of vegetation surveys with respect to aspects and canopy cover to measure the diversity of understory vegetation for better management and conservation of forest ecosystems.

The research conducted in the P. gerardiana forest of South Waziristan Agency, Pakistan, has illuminated the intricate vegetation dynamics influenced by aspectual variations. Our findings underscore that the understory vegetation is rich in biodiversity, with a marked representation of both edible and medicinal plants. While both the northern and southern aspects of the study site showcased diverse species, the southern aspect stood out with a higher prevalence of medicinal plants. Notably, the vegetation diversity was found to be marginally higher on the southern aspect when compared with the northern aspect. This is particularly significant as it hints at the influence of aspect on species richness and abundance. For instance, species such as A. carolinianum DC. and S. nubicola (Darshel) emerged as dominant on the northern and southern aspects, respectively. Furthermore, the biodiversity indices, including the Shannon diversity index and Simpson’s index, provided a deeper understanding of species richness and evenness across the two aspects. Such differences in vegetation dynamics between the northern and southern aspects could be attributed to various ecological factors, which may include light availability, soil properties, moisture content, and other microclimatic conditions. It is also worth noting that the region, though rich in biodiversity, is vulnerable to anthropogenic pressures, such as livestock grazing. The southern aspect, in particular, displayed signs of being more affected by these practices. Sustainable management practices and conservation efforts are paramount to ensure the protection and preservation of these ecologically valuable landscapes. In light of our findings, it becomes evident that understanding the role of aspect in vegetation dynamics can provide valuable insights for biodiversity conservation and sustainable forest management. Further studies across different forest reserves in Pakistan would amplify our knowledge about the intricate relationships between aspect and vegetation, aiding in informed conservation strategies for the country’s rich biodiversity.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.

IK and DZ conceptualized and wrote the main manuscript. MZ, GY, and SM helped to perform the lab analysis. MM, MZ, GY, and SM reviewed and edited the manuscript in the present form. KAK provided resources and funds. SR and AQ supervised and provided funding and approved the manuscript. All authors contributed to the article and approved the submitted version.