Abstract:

Aims: Biomass as an important ecological indicator because its critical role in evaluating the function of forest ecosystems. However, the global subtropical forest biotopes are facing fragmentation, currently. We made a thorough inquiry into the influencing mechanism of biomass in evergreen broad-leaved forests, aiming to provide scientific insights for functional restoration of forest ecosystems in subtropical forest. 

Methods: We investigated the subtropical forest located in Wuyishan National Park, Fujian. Based on the inventory data collected in 2018 and 2023 from five 0.48-ha dynamics plot established along elevation gradient, we analyzed the changes of biomass and species composition, the correlation between biomass and influencing factors (biodiversity, structural diversity, leaf functional traits and soil element content) using general linear mixed model. Additionally, using hierarchical partitioning method to seek the dominant factors affecting biomass accumulation. 

Results: (1) Over the five-year period, the total biomass in the research area increased by 62.60 t, with a productivity of 5.22 t·ha⁻¹·a⁻¹. Evergreen species contributed 5.05 t·ha⁻¹·a⁻¹ (96.81%) to this productivity, while deciduous species accounted for 0.17 t·ha⁻¹·a⁻¹ (3.19%). (2) There 25 dominant tree species (importance value greater than 1.00%) were identified, among which Castanopsis faberi, Lithocarpus harlandii, Itea omeiensis, and Eurya rubiginosa var. attenuate exhibited reduced biomass accumulation during the period. (3) The results of linear mixed model revealed that significantly positive correlations (P < 0.05) exist between biomass and both DBH standard deviation and Simpson diversity index. Conversely, significantly negative correlations (P < 0.05) were detected between biomass and both Margalef richness index and Pielou evenness index. (4) The hierarchical partitioning analysis results indicated that structural diversity and biodiversity as primary drivers of biomass accumulation, with leaf functional traits and soil element content had little effect on biomass accumulation. Among all influencing factors, the contribution rate of DBH standard deviation to biomass accumulation was the highest (31.42%), followed by Pielou evenness index (21.79%). 

Conclusion: This investigation explored the correlations between influencing factors and biomass accumulation in the evergreen broad-leaved forests of Wuyishan National Park, emphasizing that structural diversity and biodiversity indices as paramount determinants of biomass accumulation, which can provide actionable silvicultural implications for ecological restoration of subtropical evergreen broad-leaved forest ecosystems.

Key words: evergreen broad-leaved forest, biomass, community structure, biodiversity, structural diversity