洋河流域NDVI时空变化及驱动力分析

Temporal and spatial variations of NDVI and its driving factors in the Yanghe Watershed of northern China

【目的】研究洋河流域的植被覆盖变化及驱动因素,可以为该区域生态建设及植被修复提供重要的参考价值。【方法】基于SPOT Vegetation NDVI数据、气象数据及土地利用数据,运用趋势分析、偏相关分析、复相关分析及残差分析等方法,探究1999—2015年气候变化及人类活动对洋河流域NDVI的影响。【结果】(1) 1999—2015年洋河流域NDVI整体呈上升趋势,增速为每10年3. 9%,NDVI显著改善和显著退化的面积分别占流域总面积的57. 90%和1. 13%,其中有林地和灌木林地改善最为明显。(2)研究区有51. 99%的区域NDVI变化受气候因子驱动明显,其中降水驱动型和降水、气温驱动型分别占流域总面积的26. 13%和25. 44%,前者主要分布在兴和、尚义、阳高、天镇、怀安及宣化等区域,后者主要分布在兴和南部及向东偏南方向延伸的带状区域,单一的年均气温对NDVI的变化影响较弱。(3) 1999年以来,流域植被受人类活动的干扰逐渐增强,增速为每10年4. 5%,以正向作用为主,正向作用主要分布在坝缘3县(尚义、万全、崇礼)及阳高等地,负向作用主要分布在城镇和农村等人口较为密集的地区。【结论】1999—2015年洋河流域NDVI变化是气候变化和人类活动共同作用的结果,但主要影响因素为人类活动干扰,京津风沙源治理等工程项目对当地的植被改善有十分重要的作用。

[Objective] The study of vegetation cover change and driving factors in the Yanghe Watershed of northern China can provide important reference value for regional ecological construction and vegetation restoration. [Method] Based on SPOT Vegetation NDVI data,meteorological data and land use data,the impacts of climate change and human activities on vegetation NDVI in the Yanghe Watershed during 1999 to 2015 were explored using trend analysis,partial correlation analysis,multiple correlation analysis and residual analysis. [Result]( 1) The vegetation NDVI of the Yanghe Watershed in the last 17 years generally showed an upward trend with the growth rate of 3. 9% every 10 years. The area proportion of increasing and decreasing NDVI were 57. 90% and 1. 13%,respectively. Shrub land and forest improved significantly.( 2) In the study area,51. 99% of the regional NDVI changes weredriven by climate factors,with area driven by precipitation and both precipitation and temperature accounted for 26. 13% and 25. 44% of the total area of the watershed,respectively. The former area was mainly distributed in Xinghe,Shangyi,Yanggao,Tianzhen,Huaian and Xuanhua regions,and the latter was distributed in the south of Xinghe and a banded region extending to the southeast. Furthermore,annual mean temperature had little effect on the change of NDVI.( 3) The interference of human activities to the vegetation of Yanghe Watershed had an increasing trend since 1999,with more positive impacts and the growth rate of 4. 5% every 10 years. The positive effects of human activities on vegetation were mainly distributed in Shangyi,Wanquan,Chongli and Yanggao regions,while the negative effects mainly generated from towns and countries with dense population. [Conclusion] The change of NDVI in the Yanghe Watershed during the year of 1999-2015 was the result of combined effects of climate change and human activities,while human activities had the bigger effect. BeijingTianjin Dust Storm Source Control Project and other ecological projects play an important role in the improvement of NDVI in Yanghe Watershed of northern China.