中国耕地景观细碎度时空变化特征及其影响因素

耕地细碎化是中国耕地利用效率提高和农业现代化转型的关键制约因素。2014年以来中央政府试图通过鼓励土地经营权流转以实现耕地细碎度降低和适度规模经营耕地的目标。然而,少有研究开展中国全域尺度的耕地细碎化趋势分析,土地经营权流转政策的相关实施效果也尚不明晰。该研究基于长时序土地利用数据,辅以景观格局指数、趋势分析和动态面板模型等方法,对1990-2020年中国耕地景观细碎度的时空变化特征进行了识别,并剖析了土地流转政策实施对耕地景观细碎化的影响。结果表明,1）中国耕地景观细碎度大致呈"平原、盆地低、山地、高原高"的分布格局,东北平原、黄淮海平原、长江中下游平原以及四川盆地、准噶尔和塔里木盆地等地区耕地景观细碎度低,而二三级地势阶梯过渡地带以及黄土高原、云贵高原和东南丘陵等地区耕地景观相对细碎;2）1990-2020年中国耕地景观细碎度大致呈"持续细碎化-细碎化改善-波动细碎化"变化特征,其中2004-2013年耕地景观整体呈细碎化趋势,超过70%的县域耕地斑块密度（Patch Density,PD）/形状指数（Landscape Shape Index,LSI）显著增加、聚集度指数（Aggregation Index,AI）显著减小,集中分布在黄淮海平原、长江中下游平原、四川盆地以及两广地区,但2014-2020年70%的省份耕地景观细碎度有所改善,以两广地区表现最为典型;3）土地流转政策显著降低了耕地景观细碎度,此外,区域土地利用变化、非粮化耕地利用、坡度以及灌溉条件等因素也是影响中国耕地景观细碎度变化的重要因素。该研究从全域尺度剖析了中国耕地景观细碎度的时空变化特征并揭示土地流转政策等因素对其的影响,研究结果可为区域耕地景观细碎度变化以及不同土地利用/生态系统类型变化分析提供新思路。

Spatiotemporal characteristics and influencing factors of landscape fragmentation of cultivated land in China

Abstract: Cultivated land fragmentation has been widely known as one of the key limiting factors for cultivated land use efficiency, as well as agricultural modernization and transformation in China. Since 2014, much effort has been made to encourage the transfer of land management rights for the less cultivated land fragmentation, even for the cultivated land at a moderate scale. Most studies have also been conducted at the local or regional scales. However, only a few studies are focused on the fine-grained changes in cultivated land fragmentation from a national perspective. It is still lacking in the implementation effect of land management right transfer policy on the cultivated land fragmentation. In this study, a systematic analysis was made of the temporal and spatial variation characteristics of China''s cultivated land fragmentation from 1990 to 2020. The influencing factors were also identified near the implementation of the land transfer policy (2008-2020). The long-term land use data was selected to supplement the landscape pattern index, trend analysis, and dynamic panel model. The cultivated land fragmentation was roughly divided into ownership fragmentation and landscape fragmentation, in terms of connotation. The landscape fragmentation of cultivated land (CLF) was then used in this case. The results show that: (1) China''s CLF presented a distribution pattern of low in the plain and basin areas, and high in the mountainous and plateau areas. Specifically, the CLF was relatively low in the Northeast Plain, the Huang-Huai-Hai Plain, the Middle and Lower Reaches of the Yangtze River Plain, as well as the Sichuan Basin, Junggar and Tarim Basin; while the cultivated land in the transition zone of the second and third-level topographic steps, as well as the Loess Plateau, Yunnan-Guizhou Plateau, and the Southeastern Hills, is relatively fragmented. 2) China''s CLF generally showed a changing trend of continuous-improved-fluctuating fragmentation from 1990 to 2020. Specifically, the overall cultivated land showed a trend of landscape fragmentation from 2004 to 2013. More than 70% of the counties showed a significant increase in the PD/LSI or a significant decrease in the AI, which were concentrated in the Huang-Huai-Hai Plain, the Middle and Lower Reaches of the Yangtze River Plain, the Sichuan Basin, and the Guangdong-Guangzhou region. However, 70% of the provinces improved the landscape fragmentation of cultivated land from 2014 to 2020. Spatially, the counties with the improved CLF (that is, the counties with the significantly reduced PD and LSI, but increased AI) were mainly located in the transition zone of the second and third-level topographic steps, the Loess Plateau, northwest Xinjiang, and the Guangdong-Guangzhou region. (3) The land transfer policy significantly reduced the CLF. In addition, some important factors were the regional land use change, non-grained utilization of cultivated land, slope, and irrigation conditions. The spatial-temporal variation characteristics of CLF in China on a nationwide scale revealed the impact of land transfer policies and other factors on the CLF. The finding can provide a new research paradigm for the changes in the regional CLF and different land use/ecosystem types.