疏勒河流域气候变化和人类活动对植被NPP的相对影响评价

气候变化和人类活动是对陆地生态系统碳循环产生重要影响的两个因素,定量评估气候变化与人类活动对植被净初级生产力(NPP)的相对影响,对深入理解其驱动机制和控制荒漠化发展具有重要意义。以疏勒河流域为研究区,利用遥感和气象数据计算潜在NPP(PNPP)及其与实际NPP(ANPP)之间的差值,分别衡量了气候变化和人类活动对流域NPP的相对影响。研究结果表明:(1)2001—2015年疏勒河流域年ANPP整体呈缓慢增加趋势,与全国和西北地区相比,普遍较低,流域植被整体生产力水平不高。流域年ANPP空间分布呈现上游祁连山区和中下游绿洲区ANPP较高,而中下游荒漠戈壁区ANPP较低的分布格局。(2)2001—2015年流域年PNPP的变化趋势表明,降水量的变化是导致疏勒河流域植被退化加剧或缓解的主要气候驱动因素,但气温的变化对植被的影响较为复杂。(3)2001—2015年流域大部分地区植被退化系人类活动造成的,但人类活动的负向影响力在减弱。(4)气候变化和人类活动对植被NPP的相对影响均表现出明显的空间异质性,其中人类活动是疏勒河流域植被变化的主要驱动因素。

Relative effects of climate change and human activities on net primary productivity in Shule River Basin

Climate change and human activities are two factors that have important effects on the carbon cycles of terrestrial ecosystems. Quantitative assessment of the relative effects of climate change and human activities on net primary productivity (NPP) of the ecosystem could significantly improve understanding of the mechanisms driving the system and help prevent desertification expansion. We used Shule River Basin as the study area. The potential NPP (PNPP) was calculated using remote sensing and meteorological data, and the difference between the PNPP and actual NPP (ANPP) during the period 2001-2015 was used to assess the effect of climate change and human activities on the NPP in the basin. The following conclusions were made:(1) the annual ANPP of the Shule River Basin increased slowly and was generally lower than that in Northwest China and the average for China. The overall productivity of vegetation in the basin was not high. The spatial distribution results showed that the annual ANPP was high in the upstream Qilian Mountains and the mid-downstream oasis region and low in the mid-downstream Gobi region. (2) The annual PNPP trend between 2001 and 2015 indicated that precipitation is the primary factor driving vegetation degradation in the Shule River Basin, but the effect of temperature change on vegetation is complex. (3) Between 2001 and 2015, vegetation degradation was caused by human activities in most areas of the basin, but the negative effect of human activities is weakening. (4) The spatial heterogeneity was detected from the relative effects of climate change and human activities on the NPP, but human activities were the main factors driving vegetation change in the Shule River Basin.