Climate Control on Net Primary Productivity in the Complicated Mountainous Area: A Case Study of Yunnan, China

In this study, the influence of altitude on the relationship between vegetation and climate was investigated via net primary productivity (NPP) in the mountainous Yunnan province of China. In order to undertake a detailed spatial analysis at a long-term level, a monthly 1-km NPP time series from 1982 to 2014 was constructed from multisource remote sensing data sets. The altitudinal variation of the relationship between NPP and climatic factors was disclosed at annual, seasonal, and monthly scales, respectively. The results indicated that the correlation between NPP and precipitation gradually decreases from positive to negative with the ascending elevation at an annual scale, which is completely the opposite to temperature. The relationships at seasonal and monthly scales are also consistent, but significant seasonal heterogeneity was found due to the uneven climate. It was also concluded that downward run-off is responsible for the altitudinal heterogeneity, in that high-elevation areas cannot easily retain water, and only low-elevation areas benefit from the increased precipitation. What is more, we also found that the impact of climatic drought on NPP is related to topography. Large river valleys help to facilitate droughts, but the negative impacts on NPP can be mitigated in the rugged area with fluctuating slope.