1982—2015年永定河山区植被变化及对天然径流的影响

采用归一化植被指数NDVI和气温、降水、径流等监测资料，在分析永定河山区NDVI时空变化的基础上，通过构建地理加权回归模型，研究了流域内NDVI和降水、平均气温的回归参数及残差的空间关系特征，定量估算了永定河山区NDVI变化对天然径流量衰减的影响。结果表明： 1982—2015年永定河山区在土地利用格局总体变化不大的情况下，年、季尺度的NDVI均显著增加，NDVI和降水、平均气温的空间回归参数及残差的均值、趋势均具有显著的空间异质性，降水、气温等气候因素和人类活动对NDVI均表现为促进作用，但各影响因素趋势变化的时空分布差异显著。永定河山区天然径流量具有显著的衰减趋势，结合Budyko方程发现流域天然径流量对植被变化具有高度敏感性，以植被变化为突出特征的下垫面变化对永定河天然径流衰减的贡献率达到了80%，流域植被保护和水土保持对天然径流量衰减的这种影响应给予高度重视。

Analysis of vegetation change and its impact on natural runoff in the mountain area of the Yongding River Basin from 1982 to 2015

Based on the monitoring data of NDVI, temperature, precipitation, and runoff, the spatial relationship between NDVI and temperature, precipitation and residual was studied respectively by constructing geographically weighted regression model, then the influence of NDVI change on natural runoff attenuation was quantitatively estimated. The result showed that:the overall change of land use pattern was minimum from 1982 to 2015 in the mountain area of Yongding River, and NDVI of vegetation increased significantly at both annual and seasonal scales. The mean and trend values of spatial regression parameters, residual of NDVI and precipitation or average temperature had obvious spatial heterogeneity. The mean values of regression parameters and residual were positive at different time scales, while their trends fluctuated obviously. It indicated that precipitation, temperature and human activities all can increase NDVI value, while the trend of each factor had significant difference. The natural runoff had a significant attenuation trend. Due to underlying surface change with the increase of NDVI, the contribution rate of the natural runoff attenuation of typical section was about 80%, which indicated that the natural runoff was highly sensitive to vegetation change by Budyko equation. Great attention should be paid to the impact of vegetation conservation in the watershed on the attenuation of natural runoff.