汉江流域耕地生产力变化趋势与持续性分析

Change Trend and Sustainability Analysis of Farmland Productivity in the Han River Basin

开展耕地生产力变化趋势研究对耕地占补平衡评估与耕地资源可持续利用具有重要意义。近20年来,退耕还林(草)工程和城镇化对汉江流域耕地的分布与生产力产生了重大影响。基于Google Earth Engine云平台利用时间序列土地覆被与MOD17A3 NPP数据集,采用趋势分析、变异系数、Hurst指数和GIS空间分析等方法对2001~2019年汉江流域耕地净初级生产力(NPP)的时空变化趋势、稳定性及持续性进行了分析,并对汉江流域耕地生产力占补平衡状况及区域差异进行了探讨。结果表明:(1)2001~2019年汉江流域耕地NPP总体呈波动上升趋势,2001~2010年增长态势明显快于2011~2019年。(2)汉江流域耕地NPP呈西高东低的分布格局,79%的耕地NPP值介于400~600 g C·m·a,集中分布在中上游河谷盆地;耕地NPP呈显著增加的区域占全流域耕地的53.20%,主要位于中上游河谷盆地和南阳盆地,呈显著减少的区域仅占1.06%;耕地NPP变化稳定的区域集中在上游河谷盆地以及下游荆门、应城等地,不稳定区域主要位于十堰郧阳区、襄阳以及下游汉川、天门、武汉等地的城镇扩张区;流域耕地NPP未来将处于持续增加的趋势。(3)2001~2019年汉江流域转入耕地占全流域耕地的0.56%,转出耕地占4.70%,转入耕地明显少于转出耕地,汉江流域及其三级流域耕地生产力均呈较显著的占补负平衡,且以唐白河流域最为突出。

Research on the change trend and sustainability of farmland productivity is of great significance for the assessment of the requisition-compensation balance and the sustainable use of farmland resources. In the past 20 years, afforestation projects and urbanization have had important impacts on the distribution and productivity of farmland in the Han River Basin. Based on time series land cover and MOD17 A3 NPP datasets derived from the Google Earth Engine cloud platform, this study investigated the spatial and temporal change trends, stability, and sustainability of net primary productivity(NPP) of farmland in the Han River basin from 2001 to 2019 using trend analysis, coefficient of variation, Hurst index, and GIS spatial analysis. The state of requisition-compensation balance for farmland productivity and their regional differences in the Han River Basin were discussed as well. Firstly, the farmland NPP generally showed a fluctuating upward trend in the Han River Basin from 2001 to 2019, and the growth trend from 2001 to 2010 was significantly faster than that from 2011 to 2019. Secondly, the farmland NPP in the Han River Basin showed a distribution pattern of high in the west and low in the east. 79% of the farmland had NPP values between 400 and 600 g C·m·a, which was concentrated in the valley basins of middle and upper reaches. Moreover, 53.20% of the farmland presented a significant increase in NPP and was mostly distributed in the valley basins of upper-middle reaches and the Nanyang Basin, while only 1.06% of the farmland got a significant decrease in NPP. Thirdly, farmland areas having a stable change in NPP were mainly concentrated in the upper valley basins and the lower reaches such as Jingmen and Yingcheng, while unstable areas were mostly located in Yunyang, Xiangyang and the urban expansion areas of the downstream urban expansion areas of Hanchuan, Tianmen and Wuhan. Furthermore, farmland NPP in the Han River Basin will be in a continuous increasing trend in the future. Besides, 0.56% of the farmland in the Han River Basin was transferred in and 4.70% was transferred out from 2001 to 2019, with significantly less farmland transferred in than transferred out. Farmland productivity in the Han River Basin and its third-level sub-basins all showed a more significant negative balance of requisition and compensation, and was most prominent in the Tangbai River Watershed.