长江流域片2000—2015年植被NPP时空特征及影响因子探测

植被净初级生产力对评价全球变化背景下植被生长状况、陆地生态系统质量、资源环境监测具有重要意义。基于2000—2015年的MODIS NPP产品MOD17A3数据,结合DEM数据、气象数据、土地利用数据,运用趋势分析、相关性分析、地理探测器等模型方法,探讨长江流域片植被NPP的时空特征,揭示了各驱动因子的贡献率。结果表明:(1)16 a间植被NPP均值在478.4～547.4 gC/(m²·a),平均值为516.5 gC/(m²·a),流域内NPP整体表现为缓慢上升趋势。(2)流域内NPP空间分布格局为自东南向西北减少,16 a间大部分地区NPP值基本不变,云南省迪庆州、贵州省毕节市西部增长最明显,下降区域多分布于贵州省东部。(3)研究区内植被NPP与气温、降水均呈正相关; NPP随海拔增加呈先增加后下降的趋势,2 000～3 500 m海拔范围内植被NPP值最高,且集中于横断山区; 坡度小于15°的区域对整个研究区NPP值贡献最大; 林地面积最大且NPP均值最大,对研究区的植被NPP值贡献最大。(4)各因子对NPP的解释力排序为海拔>气温>降水>土地利用类型>坡度,单因子海拔对NPP的解释力最强,海拔与气温双因子交互作用对NPP的解释力最强。研究结果可为长江流域生态修复及可持续发展提供数据支持。

Spatiotemporal Characteristics and Influencing Factors of Vegetation NPP in the Yangtze River Basin from 2000 to 2015

Vegetation net primary productivity(NPP)plays an important role in evaluating vegetation growth,terrestrial ecosystem quality,and resource and environmental monitoring.Based on MODIS NPP data from 2000 to 2015 and together with DEM data,meteorological data and land use data,we examined the spatiotemporal characteristics of vegetation NPP in the Yangtze River Basin and explored the contribution rate of each driving factor by using trend analysis,correlation analysis and geographic detector modeling methods.The results indicate that:(1)the overall NPP of vegetation in the basin was increasing slowly with the range from 478.4 gC/(m²·a)to 547.4 gC/(m²·a)and an average of 516.5 gC/(m²·a);(2)the NPP value in the basin decreased from southeast to northwest and remained unchanged in most areas during the past 16 years,in which the obvious increase appeared in the western part of Diqing Prefecture of Yunnan Province and Bijie City of Guizhou Province,and the decrease mainly occurred in the eastern part of Guizhou Province;(3)NPP of vegetation in the study area was positively correlated with temperature and precipitation,and with increasing altitude,the NPP of vegetation increased initially and then started to a drop,reached to the summit in the altitude range of 2000~3500 m and concentrated in the Hengduan Mountain region;the contribution of NPP of the region with a slope less than 15 degrees to NPP value of this study area was the highest;the area of forest land was the largest,and the average NPP of the forests was the highest;(4)the contribution of each factor to NPP decreased in the order:altitude>temperature>precipitation>land-use>slope;altitude as single factor had the greatest influence on NPP,while the interaction of altitude and temperature had even more significant effect.These results can provide data support for ecological restoration and help maintain sustainable development of the Yangtze River Basin.