草地生态系统土壤呼吸对放牧干扰的响应研究进展

Review on responses of soil respiration to stock grazing in grassland ecosystems

草地占地球陆地总表面积的40%,是陆地生态系统的主体类型之一。草地生态系统碳贮量大,土壤呼吸又是陆地生态系统将碳释放到大气的重要环节,这类生态系统土壤呼吸对全球碳循环的贡献不可忽视。研究草地生态系统环境变化和人类活动干扰对土壤呼吸的影响对于估算未来碳循环前景和气候变化具有重要意义。放牧是人类对草地生态系统最重要的利用和干扰方式,在全球变化背景下,近年来草地生态系统土壤呼吸对放牧干扰的响应成为碳循环研究中的一项重要内容。现有研究结果显示,土壤呼吸对放牧干扰的响应具有一定的不确定性,其原因同这一过程所涉及的复杂机制有关。这些机制包括:放牧改变了植物凋落物的产量和质量、植物同化产物的分配和根系生物量、微生物生物量和多样性、与呼吸有关的酶的活性、土壤养分状况、土壤温度和水分状况等。对于土壤呼吸及其组分而言,上述机制有的具有促进作用,有的具有抑制作用,且在不同时间和地点起主导作用的机制各不相同,从而在放牧干扰的作用下,土壤呼吸会呈现出升高、降低或无反应等多种结果。由于根据现有这些不一致的结果,无法精确估算人类的放牧干扰活动对全球碳循环的影响,因此,今后要从土壤呼吸各个组分的区分入手,量化解析放牧干扰对土壤呼吸影响的机制过程及构建机理模型等方面加强该领域的研究。

Grassland,which occupied40%of the terrestrial surface,is one of the most important terrestrial ecosystems on earth.Contributions of soil respiration in grassland ecosystems to global carbon cycle could not be neglected.Carbon storage in grassland ecosystems is huge,and its soil respiration is an important part of carbon cycle.Researches on responses of soil respiration to environmental change and human disturbance in grassland ecosystems play an essential role in estimation of global carbon budget and predication of climatic change.As stock grazing is one of the most important disturbances in grassland ecosystems,its effects on soil respiration are one of the main contents of researches on carbon cycles.Previous studies showed that responses of soil respiration to grazing disturbance were not consistent.This inconsistent results from many complicated mechanisms,which involved a lot of biological and environmental factors,including productivity and quality of litter,allocation of assimilative masses,root biomass,microbe biomass and biodiversity,enzyme related to respiration,nutrient condition,soil temperature and moisture,and so on,are closely related to grazing intensity.Some of these changes might accelerate soil respiration while some might inhibit soil respiration.For the leading mechanisms may change with time and place,different results of increase,decrease,and lost response of soil respiration to grazing presented in similar studies.Because of those inconsistent results,researchers could not estimate the effects of grazing disturbance on global carbon cycle.Henceforth,studies on contributions from various ways of effects of grazing on soil respiration and its components,and mechanism model construction should be put in force with more concerning on the complicated processes and different components of soil respiration.