黄河源区植被净初级生产力时空变化特征及其对气候要素的响应

Spatial-Temporal Variation Characteristics of Vegetation Annual NPP and Responses to Climatic Factors in the Source Region of the Yellow River

以2000-2010年MODIS NPP数据为基础,并结合该区同期气温和降水量数据,采用趋势分析和偏相关分析法研究了黄河源区植被NPP年累积量(aNPP)时空变化特征及影响因素。结果表明:受水热条件和植被类型分布的地带性规律影响,黄河源区植被aNPP呈由东南向西北逐渐递减趋势。常绿针叶林aNPP最高,高寒草原aNPP最低。2000-2010年黄河源区植被aNPP呈显著增加趋势,线性增长率为3.64gC/(m2 a),其中高寒沼泽、常绿针叶林、高寒草甸和高寒草原aNPP的增长率分别为4.47gC/(m2 a)、4.08gC/(m2 a)、3.61ggC/(m2 a)和3.53gC/(m2 a)。植被aNPP显著增加区域占研究区面积的46.67%,并主要分布在黄河源区中下游的河谷地带。植被aNPP显著减少区域仅占研究区面积的0.03%,在空间上呈零星分布。植被aNPP与6-9月平均气温和6-7月降水量呈显著正相关性。植被aNPP与温度呈极显著正相关和显著正相关的区域分别占研究区面积的58.53%和18.36%,并主要分布在黄河源区西部、中部和东南部。植被aNPP与降水量呈极显著正相关和显著正相关的区域分别占研究区面积的3.87%和11.27%,并主要分布在黄河区北部。气候的暖湿化是导致黄河源区植被aNPP增加的主要原因。

The source region of the Yellow River, located in the northeast of the Tibetan Plateau, is an ideal region for identifying the effects of climate change on vegetation activity and inter-annual variation. Based on MODIS NPP data from 2000-2010, we analyzed spatial-temporal variation characteristics of annual NPP and its driving forces in the source region of the Yellow River, combined with temperature and precipitation datasets. We found that vegetation NPP decreased from the southeast to northwest and was coupled with changes in thermal and hydrological conditions, as well as spatial vegetation distribution. The NPP of evergreen coniferous forest was larger than any vegetation types including alpine swamp, alpine meadow and alpine grassland. In the past 11 years, vegetation annual NPP （aNPP） has increased at a rate of 3.64gC/（m2. a）; the rate varied across different vegetation types. The aNPP of alpine swamp increased fastest among all vegetation types. Regions with a significant increase in aNPP appeared in river valleys lying in middle and low reaches of the studied area, which occupied 46.67% of the total area. However, regions with a significant decrease in aNPP were distributed randomly with a proportion of only 0.03%. There was a significant positive correlation between vegetation aNPP and average temperature from June to September, and total precipitation from June to July. The positive region between vegetation aNPP and temperature covered 76.89% of the total area and was mainly distributed in the west, central and southeast part. The significant positive region between vegetation aNPP and precipitation covered 15.14% of the total area and was distributed in the northern part. A warmer and wetter climate possibly caused these vegetation aNPP changes.