【摘要】 补偿性生长是草地植物对动物采食的一种适应策略,合理的放牧强度能够促进植物的补偿性生长,有利于草地生产力和稳定性的维持,而长期过度放牧则导致草地退化.因此,确定合理的放牧强度是科学配置草地生产-生态功能实现草牧业可持续发展的基础.本文基于各类放牧实验已发表的118篇研究文献,将放牧家畜的采食率(地上生物量移除量,%)作为放牧强度的测度指标,对我国北方5种主要草地类型的植物补偿生长特征及其合理放牧强度进行了整合分析,并结合气候、土壤及植物群落地下生物量和多样性等数据,厘清了影响植物补偿生长的关键生物和非生物因子.结果表明,我国北方草地植物总体处于欠补偿生长状态,且植物地上部分的补偿性生长主要以牺牲其地下生物量为代价.其中,高寒草甸、草甸草原和荒漠草原植物群落均表现为欠补偿生长,高寒草原和典型草原植物群落表现为等补偿生长.在区域尺度上,补偿性生长的绝对值随年降水量和植物物种丰富度的增加而增加.满足植物群落地上生物量实现等补偿或超补偿,且对地下生物量不产生负效应,各类草地的合理利用强度为:高寒草甸50%、草甸草原48%、典型草原40%、高寒草原37%、荒漠草原31%.本研究对指导我国北方草地保护与合理利用,以及退化草地恢复具有重要的理论和实践意义.更多还原

【Abstract】 Grassland ecosystems cover a total area of 4 million square kilometers and account for approximately 41% of the total land area in China, providing multiple ecosystem functions and services, such as primary production, carbon sequestration,forage and food production, soil erosion control, and climate change mitigation. About 3/4 of China’s grasslands are distributed in the northern areas, which is an important ecological security barrier in northern China. Grazing is the most dominant land use form in grasslands worldwide; however, overgrazing has resulted in widespread degradation of ecosystem structure and functions. Previous studies indicate compensatory growth is a key adaptive strategy for grassland plants in response to herbivory. Moderate grazing can stimulate plant compensatory growth and enhance primary production and ecosystem stability. Therefore, reasonable grazing intensity is the basis for optimizing ecological and production functions for sustaining the long-term utilization of grasslands in this region. Based on data from 118 studies on field grazing experiments in grasslands of northern China, we conducted a meta-analysis assessing plant compensatory growth and optimal grazing intensity of five dominant grassland types: Alpine meadow, alpine steppe, meadow steppe,typical steppe, and desert steppe. We collected the data of aboveground biomass, belowground biomass, and plant species richness in grazed and ungrazed grasslands. Here, we converted the grazing intensity into forage consumption rate(i.e.,percent removal aboveground biomass by domestic animals) for each study to facilitate data analysis and comparisons across different grassland types. Furthermore, we examined the relationships of plant compensatory growth with climatic conditions, soil fertility, and changes in belowground biomass and plant species diversity. Overall, our results showed the under-compensation in plant community biomass production across the northern China grassland and that compensatory growth in plant aboveground biomass frequently occurred at the expense of decreaced belowground biomass. Specifically,plant under-compensations were found in alpine meadow, meadow steppe, and desert steppe, while plant equivalent compensations were found in alpine steppe and typical steppe. The magnitude of plant compensatory growth positively related to mean annual precipitation and plant species richness across the northern China grassland, although the driving factors differed among grassland types. Our study indicates that the sustainable utilization of the northern China grassland requires the equivalent-and/or over-compensation of plant aboveground biomass and, simultaneously, with no substantial reductions in belowground biomass. To achieve these goals, our results suggest that the optimal forage consumption rate is50% for alpine meadow, 48% for meadow steppe, 40% for typical steppe, 37% for alpine steppe, and 31% for desert steppe.Our findings have important implications for the ecology and management of grassland ecosystems in northern China and beyond.更多还原