中国陆地生态系统分类识别及其近20年的时空变化

生态系统分类制图是理解生态系统时空格局和支撑生态系统分类管理的基础。研究以反映生态系统主导服务功能和人类干预强度为主线,构建了包括9个一级和25个二级类的生态系统分类体系,集成土地利用、气候、地形、植被、土壤、居民点分布等多源数据,开展了2000和2020年中国陆地生态系统的分类制图,并对其类型、结构、格局及时空变化特征进行了分析。结果表明：近20年,我国城镇生态系统扩张1.1倍,64.51%来自耕种生态系统。耕种生态系统缩减0.88万km²,其中水田和旱田分别减少0.60万km²和2.09万km²,但绿洲扩张1.81万km²。受退耕还林还草影响,农牧和农林混合生态系统分别减少2.88万km²和0.92万km²,林地生态系统增加1.61万km²。水域湿地生态系统增加0.31万km²,70%源自沼泽生态系统的扩张,尤其是青藏高原水域湿地,受气候变暖影响扩张明显。气候暖湿化促使部分干旱荒漠和冰冻寒漠生态系统的盖度增加,使牧草地生态系统增加9.97万km²,而干旱荒漠和冰冻寒漠生态系统分别减少14.98万km²和0.92万km²。我国生态系统变化导致整体景观的连接性下降、破碎度增加、类型多样性增加,斑块间生态过程的阻碍增强。我国生态状况明显改善,92.06%的区域NDVI增加,平均NDVI增幅为0.74%/a,其中农牧和农林混合生态系统NDVI增幅最显著,分别为1.26%/a和0.85%/a。该分类方案与制图结果突出了生态系统结构、生态环境风险和生产力的差异,可为宏观尺度的生态系统管理提供科学支撑。

Terrestrial ecosystem classification and its spatiotemporal changes in China during last 20 years

Ecosystem classification is fundamental for its identification of spatiotemporal changes and type-oriented management. Based on the dominant service function and human intervention intensity, this study developed an ecosystem classification system comprising 9 first-level and 25 second-level categories, identified their spatial distribution, and further analyzed the spatiotemporal changes between 2000 and 2020, by integrating multi-source data of land use, climate, topography, vegetation, soil, and settlement distribution. The results showed that urban/township ecosystem in China expanded 1.1 times, with 64.51% of the increased area converted from the cultivated land ecosystem. Cultivated land ecosystem was shrunk by 0.88×10⁴ km², its second-level ecosystems of paddyland and dry farmland decreased by 0.60×10⁴ km² and 2.09×10⁴ km², respectively, and oasis farmland expanded by 1.81×10⁴ km². Due to implementation of the "Grain for Green" project, mixed farmland/pastureland and farmland/forestland ecosystems decreased by 2.88×10⁴ km² and 0.92×10⁴ km², respectively, while the forestland ecosystem increased by 1.61×10⁴ km². The water/wetland ecosystem increased by 0.31×10⁴ km², of which 70% was from the expansion of marshland ecosystem. With the climate becoming warmer and wetter, the arid desert and frozen land ecosystems were shrunk by 14.98×10⁴ km² and 0.92×10⁴ km², respectively, while the pastureland ecosystem was expanded by 9.97×10⁴ km². Associated with these changes, the landscape connectivity declined while the fragmentation and diversity, as well as the resistance of ecological processes increased. The ecological status in China improved significantly from 2000 to 2020, with 92.06% of the ecosystems showing an increase in the normalized difference vegetation index (NDVI) at the mean increase rate of 0.74%/a. Of the identified ecosystems, the mixed farmland/pastureland and farmland/forestland ecosystems showed the most evident increase in the NDVI, increased by 1.26%/a and 0.85%/a, respectively. The classification and mapping results highlight the differences in ecosystem structure, ecological environment risks and productivity, providing scientific support for macro-scale ecosystem management.