Comparisons of Biomass and Net Primary Productivity of Karst and Non-karst Forests in Mountainous Areas,Southwestern China

Using the forest inventory data of five provinces and autonomous regions(Guangxi,Guizhou,Yunnan,Sichuan including Chongqing,and Hunan) in southwestern China from 1989 to 1993,forest biomass and net primary productivity(NPP) in 1968 plots were estimated and their spatial pattern was analyzed.The difference of karst forest with non-karst forest was further compared.Results showed that the averaged forest biomass in SW China was 148.66 t·hm-2 and the NPP reached 9.64 t·hm-2·a-1 in the early 1990s.The karst forest biomass(124.33 t·hm-2) was less than the non-karst forest(163.48 t·hm-2);NPP of karst forest(8.67 t·hm-2·a-1) was generally also less than that of non-karst(9.56 t·hm-2·a-1),but there were differences in various provinces/autonomous regions.Among the key forest types in SW China,the subtropical and tropical coniferous forests and montane coniferous forests,subtropical evergreen broadleaved forest,and evergreen-deciduous broadleaved mixed forest,mean biomass(122.95 t·hm-2) and NPP(8.77 t·hm-2·a-1) of karst forest were less than those of non-karst forest too(152.88 t·hm-2 and 9.92 t·hm-2·a-1,respectively).The biomass and NPP of natural and artificial forests expressed the same trend,i.e.karst forest had smaller biomass and NPP than non-karst forest.Such differences implied that habitat of the karst morphology is very harsh.Under similar bioclimatic conditions,the shallow soil of karst terrain and the stress of underground water leakage restricted the growth of karst forests and their biomass accumulation and increment.