摘要:河北坝上半干旱农牧交错带是首都西北重要的生态屏障。绿水在维持坝上半干旱生态系统稳定、保障京津冀地区生态环境安全中发挥着重要作用，但绿水资源的时空分布及其驱动因素还缺乏定量理解。本文基于GLASS蒸散产品，定量分析了2001—2015年河北坝上（康保县、沽源县、尚义县、张北县）县域尺度的绿水时空变化特征，通过线性变化系数、相关系数、贡献率方法评估了绿水变化对气温、降水、净辐射（Rn）、总第一性生产力（GPP）以及土地利用的响应规律，以期为坝上地区“首都水源涵养功能区和生态环境支撑区”建设、水资源高效利用提供科学依据。研究结果表明：1）2001—2015年坝上4县的绿水量总体呈下降趋势，多年平均绿水量为371.11 mm；绿水量季节变化明显，表现为夏季>春季>秋季>冬季。2）绿水量由西北至东南递增，其中沽源县绿水量最大，康保县绿水量最小；研究期间21.2%的区域绿水量呈增加趋势，78.8%的区域呈减少趋势。3）绿水与降水、GPP呈正相关关系，与气温和净辐射呈负相关关系，各影响因子对绿水变化的贡献率排序为GPP >气温>降水> Rn，GPP的贡献率高达51%。4）研究区内各土地利用类型绿水量表现为林地>草地>耕地>建设用地。绿水量变化趋势受土地利用变化影响显著，土地利用更直接地影响绿水的空间分布。
关键词:绿水/
蒸散/
气候因素/
总第一性生产力(GPP)/
土地利用/
河北坝上
Abstract:The Bashang area is a semi-arid farming-pastoral zone in Hebei Province and represents an important ecological barrier northwest of the capital. Green water plays an important role in maintaining the stability of the semi-arid ecosystem in Bashang and ensuring the safety of the ecological environment in the Beijing-Tianjin-Hebei region. However, a quantitative understanding of the temporal and spatial distribution of green water in this area and underlying driving factors is lacking. This study used Global Land Surface Satellite (GLASS) evapotranspiration products to quantitatively analyze the spatio-temporal changes in green water and evaluated the effect on changes in green water of temperature, precipitation, net radiation (Rn), gross primary productivity (GPP), and land use at the county level (Kangbao, Guyuan, Shangyi, and Zhangbei Counties) from 2001 to 2015. These results provide a scientific basis for the construction of the "Capital Water Conservation Functional Zone and Ecological Environment Support Zone" and more efficient use of the water resources in the Bashang area. This study used the linear trend method to assess the changing trends of green water, and based on the pixel and correlation coefficient methods to analyze the driving factors of green water variation. Multiple regression analysis was used to calculate the contribution rate of each driving factor. The results showed that: 1) the amount of green water in the four counties showed an overall insignificant downward trend from 2001 to 2015. The maximum value was in 2003 (415.34 mm), and the minimum value was in 2009 (322.35 mm). The annual average green water amount was 371.11 mm. The seasonal variation of green water amount was obvious. Summer had the highest amount of green water, followed by spring, autumn, and winter. 2) The amount of green water increased from northwest to southeast regions, most of which showed a decreasing trend. Guyuan County had the highest amount of green water, and Kangbao County had the least amount. Across the regions, 21.2% showed an increasing trend in the volume changes of green water, and 78.8% of the regions showed a decreasing trend from 2001 to 2015. 3) From 2001 to 2015, the precipitation, temperature, and GPP showed an overall increasing trend, whereas Rn showed an insignificant downward trend. Green water was positively correlated with precipitation and GPP and negatively correlated with temperature and Rn. The contribution rate of each influencing factor was in the following order: GPP > temperature > precipitation > Rn. The GPP contribution rate was as high as 51%. The above-mentioned factors primarily affected temporal changes in green water. 4) The highest amount of green water was in the forest land, followed by grassland, cultivated land, construction land, and unused land. There were no significant differences in the amount of green water among land-use types, but the trend of green water changes was significantly affected by land-use changes. Land use directly affected the spatial distribution of green water.
Key words:Green water/
Evapotranspiration/
Climate factors/
Gross Primary Productivity (GPP)/
Land use/
Bashang area of Hebei Province
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