Biomass and net primary productivity (NPP) are important factors for studying terrestrial carbon storage and the carbon cycle. Using data from existing literature, this study synthesized and analyzed a comprehensive database of direct field observations of forest biomass and NPP for Southwestern China. The biomass of mature natural forests and mature planted forests range from 81.2 Mg·ha⁻¹ to 692.6 Mg·ha⁻¹ (mean = 288.1 Mg·ha⁻¹) and from 76.8 Mg·ha⁻¹ to 670.1 Mg·ha⁻¹ (mean = 181.5 Mg·ha⁻¹), respectively. Mature natural forests have higher biomass than mature planted ones. The NPP values of natural and planted forests range from 1.4 Mg·ha⁻¹·year⁻¹ to 29.6 Mg·ha⁻¹·year⁻¹ (mean = 13.6 Mg·ha⁻¹·year⁻¹) and from 0.6 Mg·ha⁻¹·year⁻¹ to 26.5 Mg·ha⁻¹·year⁻¹ (mean = 9.9 Mg·ha⁻¹·year⁻¹), respectively. Correlations among biomass, NPP, and environmental factors show that NPP significantly decreases with latitude and increases with mean annual temperature, mean annual precipitation, growing degree-days on a 0 °C base, and mean annual drought index, whereas biomass positively correlates with stand age and leaf area index strongly. Karst forests exhibit almost the same NPP as non-karst forests, but the former have significantly lower biomass compared to the latter. Comprehensive regional data synthesis and analysis based on direct field observations of forest biomass and NPP are important for benchmarking global and regional vegetation and carbon models, estimating regional carbon content, restoring vegetation, and mitigating climate change.

The biomass of a secondary evergreen and deciduous broad-leaved mixed forest was comprehensively inventoried in a permanent 2 ha plot in southwestern China. Biomass models, sub-sampling, soil pit method, and published data were utilized to determine the biomass of all components. Results showed that the total biomass of the forest was 158.1 Mg ha; the total biomass included the major aboveground (137.7 Mg ha) and belowground (20.3 Mg ha) biomass components of vascular plants as well as the minor biomass components of bryophytes (0.078 Mg ha) and lichens (0.043 Mg ha). The necromass was 17.6 Mg ha and included woody debris (9.0 Mg ha) and litter (8.6 Mg ha). The spatial pattern of the aboveground biomass was determined by the spatial distribution of dominant trees with large diameter, tall height, and dense wood. The belowground biomass differed in terms of root diameter and decreased with increasing soil depth. The belowground biomass in each soil pit in local habitats was not related to the spatial distribution of woody plants and soil pit depth. The karst forest presented lower biomass compared than the nonkarst forests in the subtropical zone. Biomass carbon in the karst terrains would increase substantially if degraded karst vegetation could be successfully restored to the forest. Comprehensive site-based biomass inventory of karst vegetation will contribute not only to provide data for benchmarking global and regional vegetation and carbon models but also for regional carbon inventory and vegetation restoration.−1 −1 −1 −1 −1 −1 −1 −1