三江源地区植被覆盖度变化及其与气候因子的关系

为揭示气候变化对三江源地区草地生态系统的影响及适应机制，研究以SPOT-VGT为基础数据，利用像元二分模型估算了三江源地区1998—2012年的植被覆盖度，分析了年最大覆盖度的变异特征，并对植被覆盖度与气候因子之间的响应关系进行了深入探讨。结果表明:在区域尺度上，15 a来研究区生长季植被覆盖度呈极显著增加的趋势（P < 0.01），平均每年增加0.004。在草地生态系统类型上，高寒草甸植被覆盖度与生长季温度的相关关系更加密切（r=0.802，P < 0.01）；高寒草原植被覆盖度与生长季温度呈显著相关关系（r=0.515，P < 0.05）。与生长季降水量相比较，5—7月降水量对高寒草原植被覆盖度变化的影响更加关键，但在高寒草甸上却不存在这种差异。

Vegetation Coverage Change and Its Response to Climate Change in Three-River Headwaters Region

Vegetation plays a pivotal role in the interaction between the biosphere and the atmosphere. Previous studies have focused on monitoring changes in the fractional vegetation cover (FVC) on account of its important role in regulating the terrestrial carbon and water cycling during the past several decades. To reveal the effects and adaptation mechanism of climate change to grassland ecosystem in Three-River headwaters region (TRH), we firstly estimated FVC using SPOT-VGT datasets and dimidiate pixel model in TRH from 1998 to 2012. Secondly, the variation characteristics of annual FVC were analyzed. Discussions were finally carried out for the response on FVC to climate factors. The results showed that FVC of TRH during the past 15 years significantly increased (P < 0.01) in the growing season, with an annual increase of 0.004 at the regional scale. For the types of alpine grassland ecosystem, the relationship of FVC with temperature of the growing season in alpine meadow was better than that in alpine steppe (for alpine meadow: r=0.802, P < 0.01; for alpine steppe: r=0.515, P < 0.05). Compared precipitation in May-July with precipitation in growing season, the former had the more key impact on FVC in alpine steppe, but there were hardly any differences for alpine meadow.