基于Google Earth Engine平台与复杂网络的黄河流域土地利用/覆被变化分析

黄河流域在中国社会经济发展和生态安全方面的地位十分重要，过去几十年的自然演变和人类活动对其造成了深远影响，系统科学地认识黄河流域的环境格局变化是实现黄河流域高质量发展的重要前提。基于Google Earth Engine平台和复杂网络分析方法，解译并分析了1986年至2018年黄河流域的连续年度土地利用/覆被变化(LUCC)。基于1000个独立验证点进行的评估显示解译的覆盖黄河流域33年的年度土地利用/覆被数据集的7个一级类的总体准确率为82.6%,15个二级类的总体准确率为74.7%。分析结果显示黄河流域的土地系统在整个研究期间呈现出复杂的时空变化，主要的LUCC模式包括：不变或很小的变化、伴随耕地流失的城市扩张、草地恢复、果园和梯田扩张和森林增加。基于复杂网络方法对黄河流域土地系统的分析表明，土地利用/覆被转移网络中的高覆盖草地、低植被覆盖地表和落叶常绿混交林与其他地类的转移较频繁，地类节点的中介中心性和度值较高，是黄河流域土地系统中的关键地类。另外与人类活动关系密切的果园和梯田、谷物耕地和城市及建设用地节点组成了较为活跃的网络社区结构，它们都有较高的结构多样性、接近中心性，这些地...

Land use/cover change in the Yellow River Basin based on Google Earth Engine and complex network

The Yellow River Basin plays an important role in China''s economic and social development and ecological security. The natural evolution and human activities in past decades had a profound impact on the Basin. A systematic and scientific understanding of the environmental changes in the Yellow River Basin is an important premise to achieve the high-quality development of the Basin. Using landsat imagery (17080 scenes) and the classification and regression trees algorithm, mapped and analyzed the annual continuous land use/cover change (LUCC) of the Yellow River Basin based on the Google Earth Engine platform and complex network analysis methods, and provided a set of 90 m resolution continuous annual land use/cover maps from 1986 to 2018. The assessment based on 1000 independent validation points collected in Google Earth indicated that these maps achieved an overall accuracy of 82.6% for 7 first-degree classes and 74.7% for 15 second-degree classes. The analysis of the land system showed that the Yellow River Basin presented complex temporal and spatial changes during the study period. The main LUCC patterns included no change or little change, urban expansion with croplands loss, grasslands restoration, orchard and terrace expansion, and forests growth. In the land use/cover transfer network, high coverage grasslands, low-vegetated lands, and the mixed forests were the key land class nodes in the land system of the Yellow River Basin, with high degrees and frequent transfers with other classes. In addition, the nodes of orchard and terrace, croplands, and urban and built-up all had high diversity and closeness and form one relatively active network community structure. The transfers between them were more important land transfer types in the land system. Time series transfer network analysis showed that the land system of the Yellow River Basin had three unstable periods in 1993-1998, 2001-2007, and 2011-2014 with lower average shortest-path length and higher network density and network transitivity. The possible reasons for these three periods are the reclamation of a large amount of agricultural land, the implementation of the Grain for Green program, and the large increase in orchard and terrace, respectively. Based on the data and analysis results, we can further understand the role of the land system in the mutual feedback between society and the environment. The results of LUCC analysis revealed the land use/cover dynamics caused by frequent human activities in the Yellow River Basin, provided insights on the impact of environmental policies and socio-economic activities on the land system, which showed that the Yellow River is moving towards achieving the sustainable development goals of livelihood security, economic growth, and ecological protection. Research provided new data processing methods and new system science perspectives for LUCC analysis, which can help to achieve high-quality regional development and to understand the interaction between human and natural systems.