1992-2015年中亚五国土地覆盖与蒸散发变化

1991年苏联解体,中亚五国独立使得土地覆盖与蒸散发格局发生深刻变化。以中亚五国为研究区,采用欧空局气候变化项目（CCI）土地覆盖和全球陆地数据同化系统（GLDAS）蒸散发数据,分析1992-2015年土地覆盖与蒸散发时空变化特征,进一步研究耕地蒸散耗水特征。结果表明：① 中亚五国土地覆盖变化具有阶段性特征,耕地扩张引起土地覆盖格局变化。1992-2003年耕地快速增加（1.1万km ²/a）,林地和草地大幅减少。2003-2015年耕地增速趋缓（0.3万km ²/a）,林地和草地有一定恢复,裸地和水体持续减少,城镇用地持续增长。耕地共增加12.3万km ²,林地和草地分别减少4.0万km ²和2.3万km ²,且集中于哈萨克斯坦中北部。裸地减少3.5万km ²,集中于哈萨克斯坦西南部,水体减少3.1万km ²,集中在咸海湖泊。乌兹别克斯坦耕地减少、裸地增加,吉尔吉斯斯坦、塔吉克斯坦和土库曼斯坦土地覆盖变化幅度较小;② 中亚五国蒸散发变化与土地覆盖格局基本一致。蒸散发总体呈增加态势（6 mm/a）,1992-2003年快速增加（11.3 mm/a）,2003-2015年缓慢上升（2.4 mm/a）。中亚五国年蒸散发达到276.8 mm,东南部的吉尔吉斯斯坦（347.3 mm）和塔吉克斯坦（302.9 mm）最高,中北部的哈萨克斯坦（297.9 mm）次之,西南部的乌兹别克斯坦（211.0 mm）和土库曼斯坦（150.0 mm）最低;③ 中亚五国蒸散耗水结构受耕地面积大小的影响。中亚五国耕地蒸散耗水的贡献由24.7%增至27.9%,土库曼斯坦耕地蒸散耗水仅占本国的11%,其他国家均超过25%。草地、林地和裸地的蒸散耗水贡献降低,但哈萨克斯坦、吉尔吉斯斯坦和塔吉克斯坦仍以草地和林地蒸散耗水为主（≥ 50%）,土库曼斯坦（61.3%）和乌兹别克斯坦（46.4%）的裸地蒸散耗水占绝对优势。本文明确了中亚五国土地覆盖连续动态变化过程,细化各国土地覆盖与蒸散发特征及差异,增强对土地覆盖与蒸散发现状的认识,可为水土资源管理和生态环境保护提供数据参考。

Changes in land cover and evapotranspiration in the five Central Asian countries from 1992 to 2015

In 1991, the collapse of the Soviet Union and the independence of the five Central Asian countries led to profound changes in land cover and evapotranspiration pattern. This study used the five Central Asian countries as target areas. European Space Agency Climate Change Initiative and Global Land Data Assimilation System data were utilised to analyse the spatio-temporal variation of land cover and evapotranspiration from 1992 to 2015 and to further study the cropland evapotranspiration water consumption. This study investigated the continuous change of land cover, specified the characteristics of and differences in land cover and evapotranspiration, strengthened the understanding of land cover and evapotranspiration in the current situation, and provided data references for water and soil resource management and environmental protection. Results show that the changes in land cover in the five countries were characterised by stages, and cropland expansion modified the land cover pattern. From 1992 to 2003, cropland increased rapidly (1.1×10 ⁴ km ²), whereas forest land and grassland decreased. From 2003 to 2015, cropland increased slowly (0.3×10 ⁴ km ²), whereas forest land and grassland increased slightly. Bare land and water bodies continued to decrease, whereas settlements continued to increase; the annual evapotranspiration was 276.8 mm. Evapotranspiration increased rapidly from 1992 to 2003 (11.3 mm/a) and then slowly from 2003 to 2015 (2.4 mm/a). The evapotranspiration of cropland (352.2 mm) and grassland (322.1 mm) was significantly higher than that of forest land (254.7 mm) and bare land (173.2 mm). The evapotranspiration changes in the five Central Asian countries were consistent with the land cover patterns; the evapotranspiration water consumption of the five countries was affected by the cropland area. From 1992 to 2015, the water consumption of cropland evapotranspiration increased by 3.2%, and the contributions of grassland, forest land and bare land continued to decrease. The cropland of Turkmenistan accounted for only 11% of the total evapotranspiration water consumption, whereas that of the other countries accounted for more than 25%.