State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Joint Center for Global Change Studies, Beijing 100875, China.
Sci Total Environ. 2017 Dec 15;603-604:290-298. doi: 10.1016/j.scitotenv.2017.06.087. Epub 2017 Jun 23.
Knowledge of the spatio-temporal responses of vegetation dynamics to hydro-climatic factors is important to assess ecological restoration efforts in arid and semiarid areas. In this study, the vegetation dynamics during 2000-2015 were investigated in the downstream area of the Heihe River Basin (HRB) in Northwest China where an ecological water diversion project (EWDP) commenced in 2000. The spatio-temporal relationships between vegetation cover and climatic factors (precipitation and temperature) and available water resources (river flow and groundwater) were determined. The results indicated that the mean growing season NDVI increased significantly during the period of 2000-2015, and the area of East Juyan Lake (EJL) enlarged to 36.4km in 2010. The scale effect of the relationships between NDVI and hydro-climatic factors was obvious. At the catchment scale, changes of NDVI were not significantly correlated with climatic factors, but significantly related with the antecedent 1-year river flow. River flow played an important role in vegetation growth within approximately 2000m distance from the river bank. At the pixel scale, the changes of NDVI were significantly positive with temperature and river flow in 17.40% and 7.14% of the study area, respectively, whereas significant relationship between NDVI and precipitation occurred in only 0.65% of study area. The suitable water table depth for vegetation growth was between 1.8 and 3.5m. The increased river flow and recovered groundwater due to the EWDP were critical for the improvement of vegetation cover, whereas the riparian vegetation degraded along some parts of the river bank. It is important to improve integrated watershed management with consideration of spatio-temporal lagged hydro-ecological connections in the study area.
了解植被动态对水热因素的时空响应对于评估干旱和半干旱地区的生态恢复工作至关重要。本研究以中国西北黑河流域（HRB）下游地区为研究对象，该地区于 2000 年启动了一项生态调水工程（EWDP），调查了 2000-2015 年期间的植被动态。确定了植被覆盖与气候因素（降水和温度）和可用水资源（河流流量和地下水）之间的时空关系。结果表明，2000-2015 年间生长季 NDVI 均值显著增加，东居延海（EJL）面积在 2010 年扩大到 36.4km。NDVI 与水热因子关系的尺度效应明显。在流域尺度上，NDVI 的变化与气候因子没有显著相关，但与前一年的河流流量显著相关。河流流量在距河岸约 2000m 范围内对植被生长起着重要作用。在像素尺度上，NDVI 的变化与温度和河流流量呈显著正相关，分别占研究区的 17.40%和 7.14%，而 NDVI 与降水的显著关系仅发生在研究区的 0.65%。植被生长的适宜地下水埋深为 1.8-3.5m。由于 EWDP，河流流量增加和地下水恢复对植被覆盖的改善至关重要，而一些河岸的河岸植被退化。在研究区，考虑时空滞后的水生态联系，进行综合流域管理非常重要。
