草地灌丛化土壤碳氮地球化学循环

灌丛化(shrub encroachment)是全球陆地生态系统重要的生态现象之一,是影响草地碳库的重要过程。灌丛化由全球气候变化、降雨、火烧和生物活动等多因素共同作用形成,对区域环境、气候、土壤性质和碳循环影响显著。目前灌丛化对生态系统的影响仍存在分歧,表现在不同气候和降雨梯度下灌丛化后土壤有机碳/氮储量、养分循环和土壤温室气体排放等差异。本文总结和归纳了灌丛化形成与控制因素、灌丛化对团聚体稳定性、酶活性和土壤碳、氮循环的影响。灌丛化改变了土壤团聚体稳定性和酶活性,进而影响土壤呼吸以及土壤生源物质的存储、分解和循环,这将显著影响区域乃至全球气候变化。因此分析提出,今后应进一步加强对灌丛化形成过程长期的定位观察研究,以便了解灌丛化的可控因素,并加强对灌丛化后土壤有机碳库、土壤团聚体稳定性变化对碳氮循环进程和全球气候变化的影响研究。

Study on the geochemical cycles of carbon and nitrogen in shrub encroachment soils

Shrub encroachment is one of most pressing ecological concerns within terrestrial ecosystems as it is an important process of grass soil carbon stocks.Shrub encroachment is the result of the combination of global climate change,rainfall,fire,and biological activities and has a significant impact on regional environments,climate,soil properties,and the carbon cycle.At present,the impacts of shrub encroachment on ecosystems are still unclear,and differences in soil organic carbon and nitrogen reserves,nutrient cycling,and soil greenhouse gas emissions have all been reported after shrub encroachment under different climates and rainfall gradients.This paper summarizes and reviews the effects of shrub encroachment on aggregate stability,enzyme activity,and soil carbon and nitrogen cycling.Shrub encroachment alters the stability and enzyme activities of soil aggregates,which affects soil respiration and the storage,decomposition,and recycling of soilderived materials.This will significantly affect regional and global climate change.Therefore,this paper proposes strengthening the long-term localization of experimental observations of the shrub formation process to understand the controllable influencing factors underlying shrub encroachment.In addition,this paper recommends strengthening the stability of the soil organic carbon pool and soil aggregates within the carbon and nitrogen cycle after shrub encroachment.