格网尺度下张掖生态系统服务价值时空演变及地形梯度分异特征

Spatial-temporal evolution pattern and terrain gradient differentiation of ecosystem service value in Zhangye, Northwest China at the grid scale

张掖生态环境脆弱,在西北乃至全国的生态地位十分重要,是生态系统服务研究的典型区域。以张掖1987、2000、2016年的3期土地利用数据为基础,划分3 km×3 km格网,基于修正后的生态系统服务价值当量,估算张掖生态系统服务价值,并分析其时空变化和地形梯度分异特征。结果表明:1987-2016年,张掖生态系统服务价值增加5.64亿元,在南部山区和北部荒漠区保持稳定,在人类活动密集的中部绿洲区变化显著;生态系统贡献上,林地生态系统的贡献最大,单项生态系统服务价值中,水文调节价值最大;生态系统服务价值具有很强的空间依赖性,在两极集聚的空间格局上,形成甘州区、焉支山和镜铁山3个"插花"集聚区;生态系统服务价值呈现出地形梯度分异规律,从祁连山区向平原绿洲区再向荒漠区递减;生态系统服务价值与地形起伏度呈线性负相关,随高程增加呈现出下降-上升-下降的变化规律,随坡度增加呈下降-稳定-下降的分异格局,说明山前区和绿洲荒漠过渡区亦是生态系统服务价值的梯度过渡区;单项生态系统服务价值在低坡度和小地形起伏地区最大,其中,低平地区绿洲的发展受水资源的严重制约。

Zhangye serves as a good case for studying ecological services because of its fragile ecological environment and its ecological importance. Using land use data from 1987, 2000 and 2016 as well as the modified ecosystem service value(ESV) equivalent, the ESV was estimated and its spatial and temporal changes and gradient differentiation characteristics were analyzed by dividing the studied region into a grid of 3 km×3 km in size. The results showed that from 1987 to 2016, the ESV in Zhangye increased by 564 million Yuan, with the mountainous areas in the south and the desert areas in the north being stable. The ESV of central oasis areas with concentrated human acti-vities significantly changed. Forests contributed to most of the ESVs. Water regulation value was the strongest among all the individual ESVs. The ESV showed strong spatial dependence. Based on the spatial pattern of the two aggregated poles, it shaped three "flower arrangement" clusters, including Ganzhou District, Yanzhi Mountain, and Jingtie Mountain. The ESV distribution showed a topographic differentiation as the value decreased from the Qilian Mountains to the plain oasis, and further to the desert areas. The linear correlation of the terrain and the ESV was negative. As the increasing elevation gradient, the ESV showed a "decreased-increased-decreased" trend, while and it had a "decreased-stable-decreased" in the increasing slope gradient. Overall, the ESV presented two turning zones on the terrain gradient, indicating that both the piedmont zone and the oasis desert transition zone acted as transition zones of the ESV. Areas with the strongest ESV were distributed in the low slope and low terrain relief zones, and the development of oases in flat terrain areas were strongly constrained by water resources.