2001-2015年天山北坡植被覆盖对干旱的响应——基于土地利用/土地覆盖分析

天山北坡生态系统脆弱，易受干旱影响，全球变暖和不合理的人类活动加剧了干旱的影响，评估植被覆盖对干旱的响应，为改善生态环境和减轻干旱影响提供科学参考。基于MODIS-NDVI遥感数据以及气象数据，计算了2001-2015年天山北坡多尺度标准化降水蒸散发指数（SPEI）和植被覆盖度，总结出植被覆盖度与多尺度SPEI时空动态变化规律，从土地利用/土地覆盖（LUCC）的角度分析了植被覆盖度对气候干旱的响应。结果表明：（1）天山北坡绝大部分区域呈湿润状态，中部（石河子、呼图壁）、西北部（克拉玛依市）呈轻度干旱。3个月、6个月、12个月时间尺度SPEI均表现出干旱化增强的年际变化趋势；（2）天山北坡植被覆盖度整体上属中低覆盖，总体呈南高北低，天山山区、城市绿洲内部高的分布特点。2001-2015年天山北坡植被覆盖度变化总体呈下降趋势；（3）年尺度天山北坡植被覆盖度与SPEI整体呈正相关关系。不同土地利用/土地覆盖的植被覆盖度与12个月时间尺度SPEI（SPEI 12）的相关性不同，大小依次为：草地 > 未利用地 > 城乡用地 > 林地 > 水域 > 耕地；（4）季节尺度夏季和春季干旱对植被覆盖度的影响最明显，不同季节干旱对不同土地利用/土地覆盖植被覆盖度影响程度不同。

Response of vegetation cover to drought in the northern slope of the Tianshan Mountains during 2001-2015 based on the land-use and land-cover change

The ecosystems on the northern slope of the Tianshan Mountains is fragile and vulnerable to drought. Global warming and damaging human activities exacerbate the effects of drought. Here, we assess the response of the vegetation cover to drought, and provide a scientific basis for improving the ecological environment and mitigating the effects of drought. Based on the normalized difference vegetation index of the moderate resolution imaging spectroradiometer (MODIS-NDVI) and meteorological observation data, standardised precipitation-evapotranspiration index (SPEI) and vegetation coverage on the northern slope of the Tianshan Mountains were calculated. Then, the temporal and spatial dynamics of vegetation coverage and multi-scale SPEI over the period from 2001 to 2015 were analyzed. Finally, in the perspective of land-use and land-cover change (LUCC), the correlation between them is discussed. The experimental results demonstrated that most of the northern slope of the Tianshan Mountains is in a humid state, with mild drought in the central (Shihezi, Hutubi) and northwest (Kenamayi) regions. The SPEI of three, six, and twelve months showed an inter-annual variation trend of enhanced aridificationt. The vegetation coverage of the northern slope in Tianshan Mountains was generally low to medium, of which with higher coverage level in the mountains and urban oases, with the overall height trend being high in the south and low in the north. From 2001 to 2015, the vegetation coverage of the northern slope of the Tianshan Mountains showed a downward trend, and this was positively correlated with drought. The vegetation coverage of different land-use and land-cover types was different from SPEI 12, and the order was:grassland > unutilized land > urban and rural land > forest land > water area > cultivated land. The influence of drought on vegetation coverage in summer and spring is the most obvious seasonal effect. The drought in different seasons had different degrees of influence on vegetation coverage of different land-use and land-cover types.