DISTRIBUTION PATTERNS OF ABOVEGROUND BIOMASS IN TIBETAN ALPINE VEGETATION TRANSECTS
青藏高原植被样带地上部分生物量的分布格局（英文）

We measured aboveground live_biomass density (ABD) in 22 sites along the Tibetan Alpine Vegetation Transects (TAVT) for different vegetation types including forests, shrublands and grasslands. Pattern analysis indicated that ABD of natural vegetation in the mountain areas increased from lower to higher altitudinal zones until the maximum was reached at some optimum elevation level and then declined as the altitude continued to increase. We believe that the altitudinal patterns to some extent reflect the latitudinal differences of maximum biomass in global forests. Regressions of transformed data based on the Weber's law revealed that January, July and annual mean temperatures and annual precipitation, singly or in combination, accounted for 28%_53% of the variation in ABD along the TAVT where annual precipitation and its combination with annual mean temperature had the highest relationship to ABD (R2=0.46_0.53, p<0.001). The relationships between ABD and the climatic factors could be expressed as logistic equations with a maximum ABD of 1 500 Mg DW@hm-2. However, the variations in annual precipitation and mean temperatures could not explain the highest ABD in the alpine fir forest in Sergyemla Mountains because ABD distribution patterns of natural vegetation can be limited by additional climatic factors such as solar radiation, wind, moisture and related water/energy balances.