The aboveground biomass of vegetation is significant to the global carbon cycle and climate change mitigation. Both biotic factors, such as forest structure attributes, community-weighted mean of traits, and functional diversity, and abiotic factors, such as topography and soil properties, can impact this biomass, either directly or indirectly, with these effects varying according to the spatial scale of the data collected.
In a study published in Forest Ecology and Management, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and collaborators examined how biotic factors and abiotic factors affect the aboveground biomass at two spatial scales (i.e., 20 m × 20 m and 50 m × 50 m) in a tropical seasonal rainforest in southwestern China.
Researchers first found that, at both spatial scales, the relative importance of biotic factors on above-ground biomass was greater than that of abiotic factors. Forest structure was the most important determinant of variation in aboveground biomass, which emphasizes the importance of forest structure in the context of forest management and restoration to improve forest carbon sequestration and mitigate climate change.
Besides, they found that the mass ratio effect played an important role in determining aboveground biomass at the small spatial scale, while there was no evidence to support the niche complementarity effect at either scale. The community-weighted mean of traits indirectly influenced aboveground biomass via forest structure.
Furthermore, researchers found higher aboveground biomass when species had conservative resource-use strategies, and revealed that at the large scale, functional richness and functional evenness indirectly reduced aboveground biomass by negatively influencing forest structure.
In addition to their indirect effects mediated by forest structure and/or traits, topography and soil properties had direct effects on aboveground biomass. Contribution of topography to aboveground biomass increased with spatial scale. Convexity negatively influenced aboveground biomass via its effects on soil properties and forest structure.
Researchers suggested that it is important to consider the scale dependence of the effects of abiotic and biotic factors on aboveground biomass concerning forest management. At larger scales, afforestation and forest restoration should be carried out in suitable terrains to maximize carbon storage. At smaller scales, forest management should prioritize regulating biotic factors.
