Land-use effect on spatiotemporal patterns of precipitation-vegetation relationship in the Loess Plateau, China

The Loess Plateau in China has long been suffered the most severe soil erosion in the world. Many believed that vegetation attenuation is the major cause, but many mechanistic details have yet been discovered. We investigated relationships between precipitation and vegetation phenology corresponding to different land use at broader scales to reveal spatiotemporal patterns of the relationships of the region, therefore, a prudent, ecologically sound management approach for this region could be developed. We correlated the long-term data of precipitation and SPOT-VGT normalized difference vegetation index (NDVI) (1km resolution) from January 1999 to December 2003 to develop joint spatiotemporal patterns between the two variables of the region. Our analyses demonstrated that: 1) vegetation types highly correlate to annual precipitation; 2) phenology of natural vegetation is highly corresponding to the precipitation with the highest leaf cover parallel the rainy season; 3) agricultural land-use of the region mismatch the precipitation with peak leaf period off the rainy season with a time lag of about 1-2 month when the most severe soil erosion occurred. Our results suggested that the main cultivation practice (planting winter wheat Triticum aestivum L., account for > 40% of the agricultural field), greatly reduced the land cover of the agricultural fields during the rainy season due to mismatching the seasonal variation of precipitation, need to be changed by cultivation of other crops with phenology match the variation of precipitation.