The Relationships between Forest Above-ground Biomass and Environmental Factors in Taiwan

In recent years, since the growing concerns of climate change and global warming, estimation on forest biomass has become one of the main methods to understand the carbon cycle. Due to the large range of variation in elevations, and the interactions between the Central Mountain Range and two major climate systems (monsoon and typhoon), Taiwan is an island with high spatial heterogeneity of environment factors. As an overall realization of AGB and its relationship between environmental factors were still unavailable in Taiwan, the aim of this study was to identify the relationships between above-ground biomass (AGB) and different types of environmental factors (such as climatic, topographic, and human disturbance factors) in Taiwan. A total of 2,813 plots in the database of The National Vegetation Diversity Inventory and Mapping Project (2003 – 2008) were analyzed by generalized linear models (GLMs). The most influential factor was mean annual temperature, followed by winter precipitation, length of dry season, actual evaportranspiration, convexity, distances to major roads, the windwardness index. Among the eight influential factors, mean annual temperature (as quadratic term), winter precipitation, length of dry season and slope were negatively related to AGB, whereas actual evaportranspiration, convexity, distances to major roads and the windwarness index were positive correlated with AGB. For climatic factors, higher stem turnover rate appeared to limit AGB accumulation in warmer forests, while both adequate water balance and temporal evenness of precipitation distribution contributed to enhance AGB accumulation. The island-wide spatial patterns of AGB showed the mechanism related to convexity and slope might regulate the quantity of AGB reduction. Both human- and natural-induced disturbances would result in decreasing AGB. Considering with the interactions of typhoons and topographic factors, landslides followed with intensive rainfall were the potential impact of typhoons on AGB in Taiwan. The intensity of the winter monsoons were not evenly distributed at island-widei, which might be one reason of unexpected relationships between AGB and the windwardness index and winter precipitation which both were used to evaluate the impacts of the northeast monsoons in winter.