Abstract: Based on the  forest inventory data of 5500 sampling plots from 1996 to 2000 in Guizhou Province and according to the biomass expansion factors (BEF) of various forest types, the forest biomass in the Province was estimated, with its spatial pattern and its differences between karst and non-karst regions analyzed. In the study period, the total biomass of trees and shrubs on forest and non-forest lands was 3.51×10⁸ t, 18% and 82% of which came from karst and non-karst regions, respectively. Different forest types had different forest biomass. Forest stands had the highest forest biomass, accounting for 71.4% of the total, and the total forest biomass in karst region was obviously lower than that in non-karst region. Among the dominant tree species and groups, Cunninghamia lanceolata had the highest total biomass (5.38×10⁷ t), followed by sclerophyll broadleaved woods (4.99×10⁷ t), Pinus massoniana, P. yunnanensis, and Quercus (2.87×10⁷-3.54×10⁷ t), Cupress (1.52×10⁷ t) and malacophyll broadleaved woods (1.43×10⁷ t), and the others (<1.00×10⁷ t). Based on the administrative division, the total forest biomass (9.83×10⁷) and forest stand biomass (5.88×10⁷ t) in South Guizhou were 1-2 folds higher than those in Zunyi, Tongren and Qiannan Districts, and far higher than those in Qianxinan, Bijie, Guiyang, Anshun, and Liupanshui Districts (total forest biomass 0.53×10⁷-1.85×10⁷ t and forest stand biomass 0.16×10⁷-0.86×10⁷t). High biomass (>400 t·hm^-2) and medium-high biomass density (100-400 t·hm^-2) mainly occurred in the bamboo forest and other forest stands in Southeast, East, and Northwest Guizhou, while medium-low biomass (30-100 t·hm^-2) occurred in the forest and non-forest areas of the Province. Low forest biomass (0-30 t·hm^-2) mainly occurred in karst region. Overall, the forest biomass in the Province was relatively low, being closely related to the topography of plateau and mountains, the rocky-desertification in karst region, and the shallow soil layer and dry habitat under karst forests, as well as the strong disturbance of human activities.

Key words: forest biomass, stem volume, karst, spatial pattern, Guizhou Province