The study was conducted in Jhansi and Lalitpur districts, located within the Bundelkhand region of Uttar Pradesh (Figure 1), which lies between latitudes 24.6° N and 25.5° N and longitudes 78.4° E to 78.6° E (Table 1). Both districts lie at an average elevation of 328 metres above sea level and fall within a semi-arid climatic zone, characterized by a rugged and undulating terrain. The region has poor soil cover, which is predominantly shallow, coarse-textured, and rocky. These edaphic conditions contribute to low water retention capacity, resulting in a major portion of the limited rainfall averaging between 800 to 900mm annually being lost to surface runoff. The variability and unreliability of rainfall exacerbate the moisture stress, with the number of rainy days fluctuating between 48 and 75 per year, followed by prolonged dry periods lasting from 3 to 7months. Temperatures can soar up to 48°C during the peak summer months, intensifying drought conditions and posing substantial challenges for agriculture and water availability.

The study was conducted using a multistage stratified random sampling method to ensure adequate representation of different localities and diameter classes. In the first stage, two districts of the Bundelkhand region in Uttar Pradesh, namely Jhansi and Lalitpur, were selected. In the second stage, five localities were randomly selected from each district. The research employed a factorial randomized block design using diameter classes with diameter between 10 and 30 cm (D₁), diameter between 30 and 50 cm (D₂), and diameter above 50cm (D₃), as the first factor. During the study period, five locations (L₁–L₅), each from Jhansi and Lalitpur districts, were employed as the second factor, and replicated five times. A systematic distributional analysis of B. monosperma was carried out to understand its growth, biomass, and carbon parameters along with leaf and flower morphological traits in the study area. For the distributional analysis of B. monosperma in agroforestry systems and naturally regenerated areas in different localities, where the trees were selected based on each diameter class. In the present study, an agroforestry system was defined as agricultural lands where B. monosperma trees are integrated with seasonal crop cultivation. The trees were either grown along the field boundaries or interspersed within the farmland where intercrops were grown. These systems represent a field-level tree-crop combination, typical of farmer-managed agroforestry practices in the Bundelkhand region. Naturally occurring populations of B. monosperma were studied in forest patches, wastelands, grassland and fallows in farmer own land.

Growth parameters of B. monosperma trees were recorded following standard forestry procedures (Chaturvedi and Khanna, 1982). Tree height (m) was measured from ground level to the top of the crown using a Haga altimeter. Diameter at breast height (DBH) was measured at 1.37m above ground using a tree calliper. Tree stem volume was estimated using the tree bio-volume formula TBV=0.4×D² ×H, where D is diameter (m), and H stands for height (m) (Dave et al., 2018). Above-ground biomass (AGB) was derived by multiplying tree stem volume with wood density (0.465tm⁻³) (Salunkhe et al., 2016), and below-ground biomass (BGB) was estimated as 26% of AGB (Ravindranath and Ostwald, 2008). Carbon storage was calculated by multiplying the sum of AGB and BGB by a carbon fraction of 0.5. The CO₂ mitigation potential was then determined by multiplying stored carbon by 3.67, representing the molecular weight ratio of CO₂ to C (Howard et al., 2014).

For leaf parameters, three mature leaves were randomly collected from the canopy of each tree between September and February. Fresh and dry leaf weights were determined using an electronic balance, with drying done at 55–60°C for 60h to a constant weight. Leaf length and leaf width were measured using an electronic leaf area metre. During the flowering time in the months of February–March, the flowers have been collected manually from the selected trees of different localities. Three panicles per tree were selected, and panicle length was measured from the peduncle base to the terminal tip using a measuring scale. Flower fresh weight was determined by weighing three randomly collected flowers per tree, while dry weight was recorded after drying the flowers under sunlight to a constant weight.

Gum collected from the selected trees through the gum extraction method, i.e., the knotching method. The knotching method is a traditional technique used for gum extraction based on the principle of induced injury to the bark, which stimulates the tree’s natural defence response (Chavan et al., 2016). Gum extraction in B. monosperma using the knotching method was carried out during the months of November and December. The process began with cleaning the bark to remove surface debris and dead bark. Sharp tools such as a bill hook, axe, or similar instruments were used to make incisions on the tree. Each incision measured approximately 1.0cm in depth, 2.5cm in length, and 0.5cm in width, and was made in an upward direction from bottom to top. After the incisions were made, the trees were left undisturbed for 2–3days to allow the gum to ooze out and harden. The ruby-coloured brittle gum exudates were then collected manually by hand. The total gum yield per tree was recorded by weighing the collected gum.

Reliable biochemical analysis requires careful sample preparation and standardized laboratory procedures. For the biochemical estimations of B. monosperma flowers and gum, replications were maintained by compositing samples collected from randomly selected trees under each treatment. 0.1g of each sample was homogenized and processed according to standard analytical protocols. Total phenolic content was determined by extracting the sample in 80% ethanol, followed by centrifugation and reaction with Folin–Ciocalteu reagent; absorbance was recorded at 650nm to quantify phenols (Gol et al., 2015). For ash estimation, a pre-weighed amount of dried sample was placed in a crucible and ignited in a muffle furnace at 575°C until a constant weight was obtained, and the ash percentage was calculated gravimetrically.

Antioxidant activity was assessed using the DPPH free radical scavenging method. The methanolic extract of the sample was reacted with a DPPH solution and incubated in the dark, and the reduction in absorbance at 515nm was used to compute antioxidant activity (Abrol et al., 2014). Total carotenoid content was estimated by extracting pigments in acetone, transferring them into petroleum ether, and measuring absorbance at 452nm; carotenoid concentration was expressed as mg β-carotene equivalent per 100g of sample. Ascorbic acid content was determined by extracting the sample in 3% metaphosphoric acid and titrating the filtrate against 2,6-dichlorophenol indophenol dye, with results expressed as mg 100g⁻¹ based on the calculated dye factor (Pila et al., 2010). Crude fat was quantified through Soxhlet extraction using petroleum ether, and the percentage of fat was computed from the difference in sample weight before and after extraction (AOAC, 1975).

Data on growth, biomass, carbon parameters, along with leaf and flower morphological traits, were analysed using analysis of variance (ANOVA) for a factorial randomized block design, with diameter classes (D₁–D₃) as the first factor and locations from both Jhansi and Lalitpur district (L₁–L₅) as the second factor. The biochemical analysis of flowers and gums was also conducted. Treatment differences were analysed using OPSTAT software at 5% level of significance.

The diameter class had a significant influence on growth, biomass, and carbon attributes of Butea monosperma in agroforestry systems in Jhansi district (Table 2). Trees in D₃ (above 50cm) recorded the significantly highest growth, biomass, and carbon parameters (p≤0.05) (DBH 55.56cm, tree height 10.90m, stem volume 1.55m³, AGB 0.72t tree⁻¹, BGB 0.18t tree⁻¹, carbon stock 0.45t tree⁻¹, and CO₂ mitigation potential 1.67t tree⁻¹). These results indicate a strong positive relationship between diameter class and biomass accumulation, carbon storage, and CO₂ mitigation potential. Leaf and flower traits were observed as non-significant across diameter classes. However, the highest leaf fresh weight was observed in D₃ (3.28g), leaf dry weight in D₂ (1.90g), flower fresh weight and dry weight in D₃ (1.90g and 0.47g), leaf length, leaf width, and panicle length in D₂ (15.44cm, 14.19cm, 15.80cm), respectively.

The growth, biomass, and carbon have a significant effect across the localities (Table 2). The significantly highest growth, biomass, and carbon parameters (p≤0.05) were observed in L₃ (DBH 44.03cm, stem volume 1.22m³, carbon stock 0.36t tree⁻¹, and CO₂ mitigation potential 1.31t tree⁻¹). The tree height was found significantly highest (p≤0.05) in L₃ (9.78m), which was at par with L₁ (9.46m), L₄ (8.9m), and L₅ (8.58m), respectively. These trends of B. monosperma reflect the influence of favourable site conditions on growth and carbon accumulation. Leaf and flower parameters were mostly found to be non-significant, except that leaf width was observed to be significant across the localities. The highest leaf width was noted in L₅ (15.02cm), which was at par with L₂ (14.5cm). Leaf fresh weight was observed to be highest in L₄ (3.53g), leaf dry weight in L₂ (2.01g), flower fresh weight in L₄ (1.91g), flower dry weight in L₃ and L₅ (0.45–0.47g), and panicle length in L₅ (16.20cm) (Figure 2). The interaction between diameter class and locations had significant effects on growth, biomass, and carbon parameters, reflecting site-specific growth responses across diameter classes.

Leaf and flower traits did not show significant interaction effects but exhibited slight variations. The present study observed a positive association between increasing diameter class and biomass/carbon accumulation, indicating that larger trees of diameter more than 50cm (D₃) contributed disproportionately to ecosystem carbon storage compared to smaller trees (D₁). This trend is consistent with earlier findings that large-diameter trees play a dominant role in biomass accumulation and carbon sequestration across forest ecosystems (Stephenson et al., 2014). Similarly, a larger diameter tree is a stronger determinant of carbon storage than stand density or species richness (Ali et al., 2019). Location-specific differences in tree performance further emphasized the role of site conditions in modulating growth. Trees in L₃ exhibited the highest DBH, stem volume, and biomass, while those in L₁ showed the lowest values. These variations may be attributed to differences in edaphic and microclimatic conditions, which strongly influence carbon accumulation and biomass allocation (Kumar et al., 2024; Kaushal and Baishya, 2021). Similar patterns have been reported in other Indian dry deciduous forest, where site quality significantly regulate biomass distribution (Raha et al., 2020; Raj and Jhariya, 2021). These findings align with the conclusions of Sist et al. (2014), Dube and Mutanga (2015), Kaushal et al. (2024), and Gautam et al. (2025), who emphasized that spatial heterogeneity in growth potential must be incorporated into biomass and carbon stock assessments.

The physiological and reproductive behaviour in B. monosperma remains relatively stable across varying sizes and sites. However, little differences such as higher flower biomass in larger trees may reflect size-dependent reproductive allocation, consistent with the theory that larger individuals invest more in reproduction while maintaining functional leaf traits for carbon assimilation (Thomas, 2011). The findings highlight that B. monosperma has strong potential for biomass accumulation and carbon sequestration in agroforestry systems, aligning with evidence that such land-use practices enhance carbon sinks, soil health, and climate resilience in India (Kant et al., 2020; Birla et al., 2024).

Diameter class significantly influenced to tree linear growth parameters in naturally regenerated areas (Table 2). The trees in D₃ (diameter above 50cm) recorded maximum tree growth parameters, viz., DBH (53.33cm), tree height (10.61m), stem volume (1.21m³), AGB (0.56t tree⁻¹), BGB (0.15t tree⁻¹), carbon stock (0.35t tree⁻¹), and CO₂ mitigation potential (1.30t tree⁻¹). The leaf and flower traits were found statistically non-significant across the diameter class. Non-significant differences were observed in tree growth and biomass parameters across localities (Table 2). However, L₄ exhibited the highest DBH (39.49cm), tree height (9.00m), stem volume (0.73m³), carbon stock (0.21t tree⁻¹), and CO₂ mitigation potential (0.78t tree⁻¹).

These findings correlated with earlier studies, which have consistently shown that tree size is the primary determinant of biomass accumulation and carbon storage, with large-diameter individuals contributing disproportionately to ecosystem-level carbon dynamics (Lutz et al., 2018; Piponiot et al., 2022). Larger trees were found to store more carbon, emphasizing the conservation of mature individuals for sustaining carbon stocks and ecosystem stability (Hauck et al., 2023; Kozák et al., 2023). Previous studies on B. monosperma also suggest genetic and environmental influences on vegetative and flowering traits (Singh et al., 2015; Singh et al., 2017), which could explain the slight variation observed across localities. Mikosch et al. (2012) found that B. monosperma maintained stable photosynthetic performance across contrasting habitats in Rajasthan, despite site-specific variations in irradiance and isotope signatures.

The growth, biomass, and carbon parameters of B. monosperma in agroforestry systems were significantly influenced by diameter class (Table 3). Trees in the smallest diameter class (D₁) recorded the lowest growth. In contrast, the trees in D₃ (diameter above 50cm) exhibited the highest DBH (52.56cm), tree height (12.78m), stem volume (1.42m³), AGB (0.66t tree⁻¹), BGB (0.17t tree⁻¹), carbon stock (0.41t tree⁻¹), and CO₂ mitigation potential (1.52t tree⁻¹), indicating a strong positive relationship between tree size and biomass potential. Leaf dry weight and leaf length were significantly highest (p≤0.05) in D₂ (2.29g and 15.77cm), which was at par with D₃ (2.02g and 15.5cm), respectively. Panicle length was significantly highest (p≤0.05) in D₃ (15.7cm), which was at par with D₂ (15.02cm) (Figure 3). The other leaf and flower traits generally showed non-significant variation across diameter classes.

Across localities (L₁–L₅), all growth, leaf, and flower parameters were found statistically non-significant. However, DBH was highest in L₄ (38.91cm), tree height in L₂ (10.98m), and stem volume in L₂ (0.82m³). The maximum AGB (0.38t tree⁻¹), BGB (0.099t tree⁻¹), carbon stock (0.24t tree⁻¹), and CO₂ mitigation potential (0.88t tree⁻¹) were also observed in L₂, reflecting the influence of favourable site conditions.

The results clearly demonstrate that the growth, biomass, and carbon dynamics of B. monosperma in agroforestry systems of Lalitpur district are strongly governed by tree diameter, while locality and interaction effects play a relatively minor role. The significant increase in DBH, tree height, stem volume, and biomass across diameter classes, with D₃ trees showing the highest accumulation, reflects the well-established principle that larger trees disproportionately contribute to biomass & carbon stocks (Lutz et al., 2018; Mildrexler et al., 2020). Similar findings have been reported from other tropical and subtropical areas, where tree size and age strongly determine carbon sequestration capacity (Köhl et al., 2017; Piponiot et al., 2022). Leaf and flower traits, which were mostly non-significant across diameter classes and sites, suggest that reproductive allocation in B. monosperma may not scale strictly with tree size but could be regulated by physiological trade-offs between growth and reproduction (Obeso, 2002). The effect of locality was non-significant for most growth parameters, likely due to high environmental homogeneity across naturally regenerated sites and potential genetic uniformity within wild populations, which may have reduced site-specific variability. Diameter class is the principal determinant of growth and carbon sequestration in B. monosperma, with larger trees serving as keystone contributors to ecosystem carbon dynamics. These findings align with global evidence emphasizing the ecological and climatic significance of conserving and managing large-diameter trees in agroforestry systems (Poorter et al., 2015).

The growth and biomass parameters of B. monosperma in naturally regenerated areas of Lalitpur district were significantly influenced by diameter classes (Table 3). Trees in D₁ exhibited the lowest growth and biomass parameter, while largest diameter class (D₃) recorded significantly highest (p≤0.05)DBH (50.8cm), tree height (11.9m), stem volume (1.23m³), AGB (0.57t tree⁻¹), BGB (0.02t tree⁻¹), carbon stock (0.36t tree⁻¹), and CO₂ mitigation potential (1.33t tree⁻¹), indicating that diameter class is a key determinant of biomass accumulation and carbon sequestration in naturally regenerated stands. Leaf fresh weight and leaf dry weight was significantly highest (p≤0.05) in D₂ (5.74g, 2.03g), while leaf length was significantly highest (p≤0.05) in D₂ (15.6cm) which was at par with D₃ (15.35cm) Flower fresh weight (1.77g) and flower dry weight (0.39g) were slightly higher in D₂ compared to D₃, and panicle length increased with tree size, with D₃ recording 14.25cm (Figure 3).

Across localities, growth and biomass parameters were largely non-significant, although a specific locality showed maximum growth L₂. Leaf fresh weight was significantly highest (p≤0.05) in L₂, L₄, and L₅ (5.34g), which was at par with L₄ (5.12g), while leaf dry weight was also significantly highest (p≤0.05) in L₂ (2.01g) which was at par with L₄ (2.0g) and L₃ (1.74g), respectively. Leaf length and width were relatively uniform across sites, with slight maxima in L₄ (154.5mm length) and L₄ (148.2mm width); whereas panicle length was significantly highest (p≤0.05) in L₂ and L₄ (14.40cm), which was at par with L₁ (13.45cm) and L₃ (13.32cm). The interaction between diameter class and locality (D×L) was mostly significant for all parameters except diameter at breast height (Table 3), suggesting that tree size is the primary driver of growth and biomass accumulation.

The trend observed here aligns with global findings that large-diameter trees disproportionately contribute to stand-level carbon dynamics due to their accelerated growth and higher accumulation rates over time (Forrester, 2021). Similar trait-specific variations have been reported in other tropical species, where reproductive and vegetative allocations fluctuate depending on developmental stage and tree size (Thomas, 2011). The observed maximum flower weight in intermediate classes suggests that B. monosperma may allocate relatively more resources to reproduction before attaining maximum vegetative size, a trade-off pattern also noted in other forest species (Gower and Richards, 1990). Maintaining large numbers of B. monosperma could substantially enhance carbon sequestration in semi-arid landscapes, echoing global evidence on the ecological and carbon storage importance of conserving large and old trees (Kozák et al., 2023). The reproductive allocation observed in intermediate classes underscores the dual ecological role of B. monosperma as a carbon sink and as a keystone species supporting ecosystem regeneration. These findings reinforce the need for conservation and sustainable management practices that promote the survival and growth of larger-diameter B. monosperma individuals. Such strategies could significantly augment biomass carbon stocks in dry deciduous ecosystems, contributing both to climate mitigation targets and to ecosystem resilience in agroforestry landscapes (Murthy et al., 2013; Birla et al., 2024; Singh and Tiwari, 2024).

Diameter class and locality had significant effects on gum yield, while their interaction effect was also significant in Jhansi and Lalitpur (Figure 4). With respect to diameter class in Jhansi district, the significantly highest gum yield (p≤0.05) was observed in D₂ (207.76g tree⁻¹). With respect to localities, the significantly highest gum yield was recorded in L₄ (163.66g tree⁻¹), which was at par with L₃ (155.93g tree⁻¹) and L₅ (144.93g tree⁻¹). There was a significant effect of diameter class and localities on the quantity of gum collected per tree in Lalitpur. Among the diameter classes, the significantly highest gum yield was recorded in D₁ (224.60g tree⁻¹). Among localities, the significantly maximum gum yield was recorded in L₄ (194.33g tree⁻¹), and the interaction effect was also found to be significant.

These results indicate that gum yield in B. monosperma is significantly influenced by tree diameter and site-specific environmental conditions. Medium-diameter trees (D₂) consistently produced more gum than smaller (D₁) or larger (D₃) trees, likely due to their optimal physiological vigour and the presence of actively functioning resin canals, which enhance gum exudation. The observed differences between localities may be linked to variations in microclimate, soil fertility, and moisture availability, which affect resin secretion. Similar findings were reported by Gyedu-Akoto et al. (2007), that both location and tree maturity significantly influenced gum production in cashew trees in Ghana. Eltahir and Ismaeil (2020) also identified growth attributes such as stem diameter and canopy spread as key determinants of high gum yield in Acacia senegal, while Eltahir and Holi (2021) observed that peak gum picking coincided with specific growth parameters. Likewise, Singh et al. (2025) reported that tree density and girth class significantly impacted non-timber product yields in Senegaliasenegal. Ballal et al. (2005) highlighted that gum arabic yield was affected by environmental factors, tapping dates, and tapping intensity in Acacia senegal plantations. Verma et al. (2023) demonstrated the effect of diameter class and environmental variables on gum production from Acacia tortilis in the arid zone of western Rajasthan, indicating that similar ecological factors influence gum yield across species and regions. Prasad et al. (2021) and Prasad et al. (2024) studied the influence of planting geometry and seasonal variability on gum yield in B. monosperma plantations in semi-arid central India. Environmental variables substantially affect both the quantity and quality of Acacia senegal gum production in different tropical environments (Hamouda, 2017; Raj and Jhariya, 2022).

The significant effect of the individual factors was observed on total phenol content in the gum of B. monosperma in Jhansi district (Table 4). Among the diameter classes, the significantly highest total phenol content, ash content, and ascorbic acid in gum (p≤0.05) were recorded in D₃ (11.27mgg⁻¹, 4.12%, 38.07mg 100g⁻¹). The antioxidant activity, total carotenoid content, and crude fat of gum from B. monosperma trees showed no significant effect of diameter class. Similarly, with respect to localities, the highest total phenol content in gum was noted in L₄ (10.82mgg⁻¹), which was at par with L₃ (10.34mgg⁻¹), and L₄ (10.02mgg⁻¹). The significantly highest ash content (p≤0.05) was reported in L₃ (4.10%), which was at par with L₂ (3.63%) and L₄ (3.36%). The crude fat was observed significantly highest (p≤0.05) in L₁ (1.12%) which was at par with L₃ (1.04%), L₄ (1.0%), and L₅ (0.89%), respectively. There was no significant effect of localities on antioxidant activity, total carotenoid content, and ascorbic acid.

In Lalitpur, there is a significant effect (p≤0.05) of both diameter class and locality on the total phenol content and crude fat in the gum of B. monosperma trees (Table 5). Among the diameter classes, the significantly highest total phenol content was recorded in D₃ (13.61mgg⁻¹). The ash content and antioxidant activity in the gum of B. monosperma were not significantly affected by diameter class. The total carotenoid content was observed significantly highest in D₂ (16.61mg 100g⁻¹), which was at par with D₃ (15.5mg 100g⁻¹). The ascorbic acid was highest in D₃ (42.08mg 100g⁻¹), which was at par with D₂ (39.41mg 100g⁻¹). The highest crude fat content was recorded in gum from D₁ trees (0.67%). Among the different localities, the significantly highest total phenol content was recorded in L₅ (12.80mgg⁻¹), which was at par with L₄ (12.42mgg⁻¹), and L₁ (12.23mgg⁻¹). The highest crude fat content was recorded in gum from L₁ (0.82%). Localities showed a non-significant effect on the ash content, antioxidant activity, total carotenoid content, and ascorbic acid.

Based on the results obtained, it is evident that larger diameter classes accumulated higher total phenols and ascorbic acid in gum, attributed to greater metabolic activity and enhanced storage capacity in older trees. These findings are consistent with Gyedu-Akoto et al. (2008), who reported that the physico-chemical properties of cashew tree gum varied with location and tree characteristics. Environmental factors such as soil type, temperature, and water availability significantly impacted the secondary metabolism of medicinal plants (Mohiuddin, 2019). The observed increase in ash content with larger diameter classes could be attributed to the higher accumulation of mineral constituents in older trees. Variation among different localities may be due to differences in soil mineral composition and environmental factors influencing mineral uptake and deposition in gum. Tahir et al. (2007) noted that tree age and site conditions significantly affected the physiochemical properties of natural gums. Tree age and site may slightly enhance or reduce the antioxidant properties of gum, attributed to variations in plant stress factors or secondary metabolite synthesis. The significant increase in ascorbic acid content observed in medium and larger diameter trees aligns with the role of ascorbic acid as a crucial antioxidant metabolite in woody plants. Bilska et al. (2019) highlighted the multifunctional role of ascorbic acid in woody plants, particularly its involvement in stress mitigation and cellular protection. The younger trees (smaller diameter) accumulated higher crude fat levels in their gum, attributed to differences in metabolic allocation of lipophilic compounds during early growth stages. The observed differences across sites indicate that environmental factors, including soil properties, moisture availability, and microclimatic conditions, play a substantial role in influencing lipid synthesis and deposition in the gum. Quainoo and Dugbatey (2016) reported that the age of Shea trees (Vitellaria paradoxa) significantly influenced latex flow, suggesting that physiological age-related changes impact the biosynthesis and exudation of lipophilic compounds.

In Jhansi, there is a non-significant effect of diameter class, locality on total phenol content in flowers of B. monosperma (Table 4). There was a significant effect (p≤0.05) of diameter classes on total carotenoid content, antioxidant activity, and ascorbic acid. The total carotenoid content was recorded in D₂ (35.65mg 100g⁻¹), which was at par with D₁ (34.04mg 100g⁻¹). The antioxidant activity was observed significantly highest in D₁ (72.92%) and at par with D₃ (69.27%). The interaction between diameter class and localities (D×L) was found to be significant in terms of antioxidant activity. Among diameter classes, the significantly highest ascorbic acid content was recorded in D₂ (5.74mg 100g⁻¹), which was at par with D₃ (5.61mg 100g⁻¹). The locality has significantly recorded the highest ash content was reported in L₃ (6.66%). With respect to locality, a significant effect on crude fat content was observed. The significantly highest crude fat content was observed in L₅ (3.39%), which was at par with L₃ (3.21%), L₄ (3.07%), and L₂ (2.79%), respectively. With respect to localities, there is a non-significant effect on total carotenoid content, antioxidant activity, and ascorbic acid.

In Lalitpur, the data revealed that the effect of diameter class on total phenol content, ash content, antioxidant activity, total carotenoid content, and ascorbic acid was statistically significant (Table 5). The highest phenol content was recorded in D₂ (16.03mgg⁻¹), which was at par with D₃ (14.72mgg⁻¹). This suggests that trees in the intermediate diameter class may have optimized secondary metabolite production. The significantly highest ash content was observed in D₂ (6.08%). The highest carotenoid content (37.14mg 100g⁻¹) was recorded in D_1, which was at par with D₂ (36.97mg 100g⁻¹). D₃ showed the highest antioxidant activity (68.90%) and was at par with D₁ (68.49%). The significantly highest ascorbic acid was found in D₂ (5.74mg 100g⁻¹), which was at par with D₃ (5.34mg 100g⁻¹). In Lalitpur, the diameter class exhibited a non-significant effect on crude fat content. While among localities, the data was found to be statistically significant. Among localities, the highest antioxidant activity was observed in L₅ (69.64%), while the lowest (57.98%) was in L₄, which was at par with L₁ (69.05%), L₃ (68.88%), and L₂ (64.41%). Interaction analysis of diameter class and locality on antioxidant activity was found to be significant. The maximum crude fat was observed in L₃ (3.35%) which was at par with L₁ (3.32%), L₄ (3.06%), and L₅ (2.94%). With regard to localities, there is no significant effect of locality on phenol content, ash content, total carotenoid content, and ascorbic acid in the flowers of B. monosperma.

Phenolic biosynthesis may peak at an optimal balance between tree maturity and metabolic activity, which is often higher at intermediate growth stages due to optimal physiological conditions (Dong et al., 2011; Verma and Shukla, 2015; Li et al., 2020). The role of elicitors and physiological maturation in secondary metabolite accumulation has also been highlighted by Bharti et al. (2023) and Mazumder et al. (2011) in B. monosperma. Oguntunde et al. (2011) and Meena and Asrey (2018) demonstrated that tree age significantly affects mineral levels and nutrient allocation in fruit crops. Carotenoid pigment synthesis is closely linked to the developmental stage rather than the spatial variation. Yan et al. (2023) found similar results in Torreya grandis, where younger and intermediate-aged trees had higher carotenoid and flavonoid concentrations compared to older ones. Aregay et al. (2021) also recorded such age-related trends in Citrus spp., emphasising physiological vigour in earlier stages. Carotenoid biosynthesis is influenced by both light intensity and metabolic activity, which may explain the decline in older trees (Padghan, 2018). Antioxidant levels in plants are largely governed by phenolic and carotenoid concentrations (Lobo et al., 2010; Salar and Seasotiya, 2011). The wide variability between localities in Lalitpur could be attributed to site-specific stressors, microclimatic variations, and soil nutrient status, all of which have been shown to modulate antioxidant capacity. The association between phenolic content and antioxidant capacity was reported by Sehrawat and Kumar (2012) in B. monosperma. The result suggests that Ascorbic acid biosynthesis peaks at intermediate maturity before declining in older trees. This is consistent with reports that metabolic activity and antioxidant vitamin accumulation are linked to active growth phases (Pandey et al., 2015). Kumar et al. (2017) observed that climate change stress influenced antioxidant vitamin levels in medicinal plants, suggesting that under strong environmental pressures, locality could play a larger role. Crude fat content showed non-significant differences across diameter classes in both districts but significant locality-wise differences, with higher values in specific fertile sites. This aligns with research showing that lipid biosynthesis in flowers and seeds is influenced by nutrient and moisture availability (Pachkore et al., 2010). The lack of a strong age effect suggests that lipid accumulation in B. monosperma flowers is more sensitive to current environmental conditions, especially soil fertility and water status, than to developmental stage. Gupta et al. (2016) noted that floral lipids in Butea are important for pollinator attraction, and their variation may be ecologically significant.