京津风沙源区2000—2015年植被覆盖状况的区域差异研究

植被覆盖状况是监测与表征区域生态建设成效的重要指标。以往研究注重区域植被覆盖状况的整体变化分析，对长时期区域内部植被覆盖变化及其差异研究较少。文中基于京津风沙源区遥感影像数据，采用GIS空间分析技术，重点评估了2000—2015年植被覆盖度的年际变化及其区域差异。研究结果表明，2000—2015年京津风沙源区植被覆盖度变化为35%~45%，且随年份变化呈波动增加趋势，年均增速为0.4%(P<0.05)，生态治理取得明显植被恢复成效。8个治理分区植被覆盖均有所增加，但区域差异明显，晋北山地丘陵亚区和燕山丘陵山地水源保护亚区植被覆盖度年均增速超过0.6%，浑善达克沙地亚区与荒漠草原亚区植被覆盖度年均增速不及0.2%，这与区域地表组成和气候背景有关。从地市来看，北京、天津和承德植被覆盖度较高，但朔州和张家口植被覆盖度增速明显，而乌兰察布和包头植被覆盖度年均增速低于0.1%。相比2000年，2015年京津风沙源区有51%的区域植被覆盖度增加，49%区域植被覆盖度未变或降低，主要集中在京津风沙源区的中部和西部县市(旗)，未来生态治理过程中应加以重点关注。

Regional differences of vegetation cover in the BeijingTianjin sandstorm source region from 2000 to 2015

Vegetation status represents the overall condition of regional ecological environment, hence vegetation coverage is often used to measure the effectiveness of ecological protection and restoration projects. Although numerous studies have reported the overall changes of vegetation coverage in the BeijingTianjin sandstorm source region, few studies have investigated the regional differences over the years. In this paper, we calculated the annual vegetation coverage from 2000 to 2015 in the BeijingTianjin sandstorm source region using MODIS data, emphasizing the regional variations of vegetation cover in different subzones through statistical and GIS technology. The results indicated that, during the study period, the annual vegetation coverage in the region increased from 35% to 45% with an average annual growth rate of 0.4%. Although vegetation coverage in the eight subzones presented similar growth trend, remarkable differences existed in the vegetation status and growth speed. The annual vegetation growth rates in the Jinbei mountain-hill and Yanshan mountain-hill-water-source-protection subzones exceeded 0.6%, however, lower than 0.2% annual growth rates were observed in the Otindag sandy land and Desert grassland subzones. In addition, higher degree of vegetation primarily distributed in the sandstorm source regions of Beijing, Chengde and Tianjin with Shuozhou and Zhangjiakou showing higher growth rates, whereas the rates were lower than 0.1% in Wulanchabu and Baotou. Approximately 51% BeijingTianjin sandstorm source region saw growth rate increasing in 2015 compared to 2000, while the remaining areas experienced decline in the mid and western districts. In conclusion, this study confirmed that significant vegetation improvement has been made in the BeijingTianjin sandstorm source region, however, some areas remain poorly covered, therefore more efforts should be directed to these areas towards ecological restoration.