人类活动和气候变化对锡林郭勒草原生产力影响

Natural grasslands are increasingly subjected to the dual stresses of grazing pressures and climate change. However, the contribution of human activities, especially grassland ecology conservation projects, to grassland improvement remains ambiguous. Utilizing MODIS satellite data in conjunction with the VPM model, the gross primary productivity (GPP) changes in the Xilingol grassland from 2000 to 2020 were assessed. Based on GPP data derived from remote sensing, this study quantitatively assessed the spatiotemporal dynamics of the impacts of climate change and human activities on the productivity of grassland in the Xilingol League. From 2000 to 2020, the grasslands exhibited a greening trend characterized by a significant annual GPP increment of 2.66 g C m ^–2 yr ^–1 ( P <0.05). Climate change and human activities jointly contributed to this greening trend, with relative contribution rates of 55% and 45%, respectively. However, the relative contributions of climate change and human activities to the trend of GPP varied greatly in different regions. Climate change emerged as the principal driver in the central and eastern regions of Xilingol League with robust grass growth, accounting for more than 65% of the GPP enhancement. Conversely, human activities were the dominant factors in less verdant western regions and the agro-pastoral ecotone, representing more than 60% of the GPP change. Grassland productivity was sensitive to grassland ecological restoration measures, with significant changes in the trends of grassland productivity attributed to human activities in pivotal policy implementation years such as 2005 and 2011. Specifically, measures such as the control of wind/sand sources and returning grazing land to grassland from 2000 to 2005 gradually alleviated the pressure of human activities on grassland productivity, as they significantly improved vegetation growth in high-quality grasslands. Under the forage-livestock balance policy from 2005 to 2011, inadequate compensation for grassland ecological protection led to a significant reduction in GPP, as some herders increased their livestock holdings despite grazing restrictions, and this particularly affected the high-quality grasslands. The implementation of the Grassland Ecological Protection Subsidy and Reward Program from 2011 to 2020 generally promoted the recovery of productivity in eastern and western Xilingol League grasslands, but significant ecological pressure persisted. This study provides theoretical support for optimizing grassland ecosystem management and forming a virtuous cycle of grassland conservation in pastoral areas.

天然草原正承受着放牧压力和气候变化带来的双重影响。然而，人类活动尤其是草地生态保护工程对草地改善的贡献尚不明确。本研究基于 MODIS 卫星数据，利用 VPM 模型定量分析了人类活动及气候变化对锡林郭勒盟草原生产力影响的时空动态。2000–2020 年锡林郭勒盟草地总体变绿，生产力年均显著增加 2.66 g C m ^–2 yr ^–1 （ P <0.05）。气候变化及人类活动共同促进草地的变绿趋势，相对贡献率分别为 55%及 45%。不同地区气候变化及人类活动对 GPP 变化趋势的相对贡献存在很大差异，在锡林郭勒盟中东部等草地生长较好的地区，气候变化是 GPP上升的主导因素，其相对贡献度均在 65%以上；在锡林郭勒盟西部草地生长较差的地区和农牧交错带，人类活动是GPP 变化的主导因素，其相对贡献度均在 60%以上。此外，草地生产力对草原生态修复工程措施响应敏感，在 2005年和 2011 年等政策实施的关键年份，草地生产力变化趋势受人类活动显著影响。2000–2005 年，风沙源治理和退牧还草等措施逐渐缓解了人类活动对草地生产力的压力，高质量草地植被生长明显改善。2005–2011 年草畜平衡政策实施期间，由于生态补偿吸引力不足，部分牧民在限制放牧的情况下仍扩大了牲畜规模，其对高质量草地的生态影响尤为明显，导致了 GPP 显著下降。2011–2020 年草原生态保护补贴奖励计划实施，总体上促进了锡林郭勒盟东、西部草地生产力恢复，但部分地区依然存在生态压力。本研究旨在为优化牧区草地生态系统管理、形成草原保护良性循环提供理论支持。