Variations of the biodiversity and carbon functions of karst forests in two morphologically different sites in southwestern China

Knowledge of the biodiversity and carbon (C) functions of karst forests is scarce. This study comprehensively compared the species diversity and floristic characteristics, biomass and its allocation, leaf and soil C and nitrogen (N) concentrations, and photosynthetic capacity of dominant tree species between peak clump depression (PCD)-type and plateau surface (PS)-type karst forests on the basis of two large plots (i.e., 1 and 2 ha, respectively) in southwestern China. Results showed that PCD-type karst forest exhibits higher biodiversity and more tropical family and genus types than PS-type karst forest. These two types of karst forest presented similar total biomass, but PCD-type karst forest allocated more biomass to supporting roots and less biomass to absorbing roots. PS-type karst forest had higher C/N ratios in leaves and soils than PCD-type karst forest. Deciduous tree species in PS-type karst forest had low net photosynthetic rates, resulting in lower net photosynthetic rate in PS-type karst forest than in PCD-type karst forest. Species richness and C storage in the karst morphologies would be considerably enhanced if degraded vegetation in different types of karst area could be successfully restored to forests according to respective morphological and vegetation features. A comprehensive understanding of the biodiversity and C functions of karst vegetation is essential to biodiversity conservation, regional C storage estimation, vegetation management and restoration, and potential global change mitigation.