Sun Wenchao, Song Hao, Yao Xiaolei, Ishidaira Hiroshi, Xu Zongxue
College of Water Sciences, Beijing Normal University, Beijing, China; Joint Center for Global Change Studies (JCGCS), Beijing, China.
Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Kofu, Yamanashi, Japan.
PLoS One. 2015 Aug 18;10(8):e0135376. doi: 10.1371/journal.pone.0135376. eCollection 2015.
The Heihe River Basin (HRB) is the second largest inland river basin in China, characterized by high diversity in geomorphology and irrigated agriculture in middle reaches. To improve the knowledge about the relationship between biotic and hydrological processes, this study used Global Inventory Modeling and Mapping Studies Normalized Difference Vegetation Index (NDVI) data (1982-2006) to analyze spatiotemporal variations in vegetation growth by using the Mann-Kendall test together with Sen's slope estimator. The results indicate that 10.1% and 1.6% of basin area exhibit statistically significant (p < 0.05) upward and downward trends, and maximum magnitude is 0.066/10a and 0.026/10a, respectively. More specifically, an increasing trend was observed in the Qilian Mountains and Hexi Corridor and a decreasing trend detected in the transitional region between them. Increases in precipitation and temperature may be one possible reason for the changes of vegetation growth in the Qilian Mountains. And decreasing trend in transitional region may be driven by the changes in precipitation. Increases of irrigation contribute to the upward trend of NDVI for cropland in the Hexi Corridor, reflecting that agricultural development becomes more intensive. Our study demonstrates the complexity of the response of vegetation growth in the HRB to climate change and anthropogenic activities and correspondingly adopting mechanistic ecological models capable of describing both factors is favorable for reasonable predictions of future vegetation growth. It is also indicated that improving irrigation water use efficiency is one practical strategy to balance water demand between human and natural ecosystems in the HRB.
黑河流域是中国第二大内陆河流域，其特点是地貌多样，中游有灌溉农业。为了增进对生物和水文过程之间关系的了解，本研究使用全球清单建模与制图研究归一化植被指数（NDVI）数据（1982 - 2006年），通过Mann - Kendall检验和Sen斜率估计器分析植被生长的时空变化。结果表明，流域面积的10.1%和1.6%分别呈现出具有统计学意义（p < 0.05）的上升和下降趋势，最大幅度分别为0.066/10年和0.026/10年。具体而言，祁连山和河西走廊观测到上升趋势，而它们之间的过渡区域则检测到下降趋势。降水和温度的增加可能是祁连山植被生长变化的一个原因。过渡区域的下降趋势可能是由降水变化驱动的。灌溉量的增加导致河西走廊农田NDVI呈上升趋势，这反映出农业发展变得更加集约化。我们的研究表明了黑河流域植被生长对气候变化和人类活动响应的复杂性，相应地采用能够描述这两个因素的机理生态模型有利于合理预测未来植被生长。研究还表明，提高灌溉用水效率是平衡黑河流域人类和自然生态系统用水需求的一项切实可行的策略。
