Structural diversity is a key driver of above-ground biomass in tropical forests

ABSTRACTBackground A gamut of abiotic and biotic factors is related to the amount of above-ground biomass (AGB) produced in ecosystems. Some factors have direct and others indirect relationships with AGB. Detailed analyses in tropical forests are few but much needed for better understanding the potential impacts of global change drivers and for mitigating impacts.Aims Here, we examined the relationship between AGB and different predictor variables and quantitatively evaluated their relative importance in lowland to lower montane deciduous and lower montane – montane evergreen forest types. We hypothesised that the relationship between AGB and climate, topography, structural diversity, species diversity (alpha and beta) and phylogenetic diversity would differ between the two forest types.Methods We inventoried trees from 114 plots (each 0.1 ha) and used partial least square (PLS) structural equation modelling (SEM) to test the direct and indirect relationship between AGB and the predictor variables.Results We found that structural diversity variables, stem density and tree girth, were significantly and positively related to AGB in both forest types, displaying a stronger relationship in montane evergreen forests (w = 0.65 for density and 0.89 for tree girth). In the deciduous forest, alpha and phylogenetic diversity were also important factors, whereas beta and phylogenetic diversity were important in the evergreen forest. The effects of topography and climate varied between forest types, with elevation and precipitation being related to AGB directly and indirectly through their relationship with structural diversity.Conclusion Our results suggest that structural diversity is a key driver of tropical forest biomass, both directly and indirectly. This fundamental understanding can aid in the predictive efforts of biodiversity conservation and forest management.Policy highlightsStructural diversity affects biomass, directly and indirectly facilitating the importance of monitoring and land-use planning.A structurally diversified forest can be considered while selecting reserves for conservation.Prioritizing the preservation and improvement of structural diversity in forests is crucial.Assessing forest productivity requires considering stand characteristics and biodiversity.KEYWORDS: Climatedeciduous forestevergreen foresttree diversityWestern ghatsDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also. Declaration of competing interestThe authors declare no conflict of interest.AcknowledgementsWe thank the Karnataka Forest Department for providing the necessary permissions and assistance for the fieldwork. We also express sincere gratitude to all the anonymous reviewers and the Editor- in-Chief for their valuable comments, which contributed to improving the quality of the paper.Additional informationFundingThis work was supported by the Department of Biotechnology and Department of Space, Government of India (Grant no.-BT/Cood.II/10/02/2016), as a part of a project ‘Biodiversity characterization at community level in India using Earth observation data’.