环境地球化学国家重点实验室知识库

Repeated observation based on large permanent monitoring plots is a key method for directly understanding forest regeneration dynamics. Karst forests grow slowly in adverse habitats and possess a special regeneration mode. However, no data can support these properties because no repeated observations have been performed. The mortality, recruitment, and net change in live woody biomass (NPPlw) of a karst evergreen and deciduous broad-leaved mixed forest in Central Guizhou Province, Southwestern China, were studied on the basis of a short-term continuous monitoring (3 years) of a 2 ha plot. The species richness of individuals with a diameter at breast height (DBH) 1 cm decreased from 66 to 58 during the study period. Eight species disappeared, and no new species appeared. The individual number declined from 16,821 to 15,003 because most species indicated more deaths than recruitments. Trees presented the lowest mortality rate, and shrubs presented the highest recruitment rate among the species. Individual death number decreased with the increase in DBH classes. The estimated aboveground NPPlw was 8.41 t ha(-1) year(-1). The survivors, recruitments, and deaths contributed 10.88, 0.11, and -2.58 t ha(-1) year(-1), respectively. Trees (8.37 t ha(-1) year(-1)), rather than shrubs (0.04 t ha(-1) year(-1)) and lianas (-0.004 t ha(-1) year(-1)), were the major contributors. The karst forest presented higher mortality and lower NPPlw than nonkarst forests in subtropical China and in the world.