为了掌握北方农牧交错带植被NPP的多年时空变化特征,研究气候变化和人类活动对植被NPP的影响,基于VEGETATION-NDVI数据、气象数据及植被类型数据,采用CASA模型,对北方农牧交错带的植被NPP进行了估算,采用Theil-Sen Median趋势分析、偏相关分析、残差分析等方法分析了该地区NPP与气候因子及人类活动的关系。结果 表明:1998—2016年研究区的NPP年均值空间上呈西南、东北高,中间低,研究区内NPP增加的区域明显大于NPP减少的区域; 年降水量呈东南高、西北低分布,而年平均气温分布呈南高北低、东高西低,在研究时段内,年降水量整体呈增加趋势,大部分地区的年平均气温也呈上升趋势; NPP与降水量之间存在正相关关系,与年平均气温具有明显的负相关关系; 气候变化和人类活动对植被影响的积极贡献明显大于对植被变化的消极作用,气候变化在植被恢复中占主导地位,人类活动是植被退化的主要因素。在北方农牧交错带植被NPP的主要影响因子是气候变化,降水的增多促进了植被的修复; 气温升高和人类活动增强导致了植被的退化,因此,减少人类活动和减缓气候变暖对于该地区植被的修复具有重要意义。
In order to grasp the characteristics of multi-year spatiotemporal changes of vegetation NPP in the agricultural pastoral ecotone of northern China(APENC), the effects of climate change and human activities on vegetation NPP were studied. Based on VEGETATION-NDVI data, meteorological data and vegetation type data, the CASA model was used to estimate the vegetation NPP in the agricultural pastoral ecotone of Northern China. The Theil-Sen Median trend analysis, partial correlation analysis, residual analysis and other methods were used to analyze the relationship between NPP and climate factors and human activities in this area. The following conclusions are drawn. The annual average value of NPP in the study area from 1998 to 2016 was spatially high in the southwest and northeast, and low in the middle. The increase in NPP in the study area was significantly larger than the decrease in NPP. The annual precipitation was high in the southeast and low in the northwest, while the annual average temperature was high in the south and low in the north, high in the east and low in the west. During the study period, the annual precipitation had an overall increasing trend, and the annual average temperature in most areas had also increasing trend. There was a positive correlation between NPP and precipitation, and an obvious negative correlation with annual average temperature. The positive contribution of climate change and human activities to vegetation was significantly greater than its negative effect. Climate change is dominant in vegetation restoration. Human activities are the main factor of vegetation degradation. The main influencing factor of vegetation NPP in the APENC is climate change. The increase in precipitation promotes the restoration of vegetation; the increase in temperature and the enhancement of human activities lead to the degradation of vegetation. Therefore, reducing human activities and slowing down climate warming are of great significance to the restoration of vegetation in this area.
(3)
为xi的平均值; yi为第i年/月的降水量或气温;
为yi的平均值。
(4)
(5)
