黄淮海平原不同土地利用方式对土壤有机碳及微生物呼吸的影响

Effects of Different Land Use Types on Soil Organic Carbon and Microbial Respiration in Huang-Huai-Hai Plain

土壤是陆地生态系统最大的碳库,有机碳通过微生物分解作用向大气释放CO_2,土壤碳库的微小变化将会对大气CO_2浓度和全球碳循环产生巨大的影响。在当前人类活动频繁和土地利用与土地覆被变化的背景下,研究不同土地利用方式对土壤有机碳等理化性质和土壤微生物呼吸等功能的影响,可以阐明影响土壤碳汇功能的关键因子,为未来土地利用管理提供科学依据。以开封市为例,研究了黄淮海平原不同土地利用方式(包括弃耕地、草地、果园、农田和森林)下土壤湿度、pH值、铵态氮、硝态氮、总碳、总氮、有机碳、可溶性有机碳、微生物生物量碳氮、微生物呼吸及其温度敏感性的变化规律。研究结果表明,(1)森林土壤湿度、总碳、总氮、有机碳(1.48%)、微生物生物量碳氮含量显著高于其他土地利用方式,但其微生物呼吸(101.06 mg·kg^(-1)·d^(-1))和温度敏感性(1.18)最小。(2)农田土壤的总碳、总氮、有机碳、微生物生物量碳氮含量均次于森林且高于其他土地利用方式,微生物呼吸速率较大(128.55 mg·kg^(-1)·d^(-1))。(3)弃耕地、草地和果园土壤碳氮和微生物碳氮较小。(4)结构方程模型表明土地利用方式可以直接解释土壤有机碳积累的68%,且可通过土壤湿度间接地影响土壤有机碳和微生物呼吸。土壤有机碳和微生物呼吸分别被土壤湿度和硝态氮含量等因子解释了93%和54%。该研究表明森林生态系统利于土壤有机碳固持,其较小的微生物呼吸温度敏感性对应对未来全球气候变化具有重大意义;农田占地面积广大,农业经营中在保障粮食生产的同时要采取免耕或秸秆还田等措施充分发挥其碳汇作用。

Soils are the largest carbon pools in terrestrial ecosystems.Soil organic carbon can be decomposed by microorganisms andrelease CO2to atmosphere.Minor changes in soil carbon pool will significantly affect atmospheric CO2concentration and globalcarbon cycling.Under the current background of frequent human activities and land use/cover changes(LUCC),it is necessary tostudy the effects of different land use types on soil physico-chemical properties and microbial functions(such as soil organic carbonand microbial respiration)to illuminate the key factors of influence soil carbon sequestration function and provide scientific evidencefor future land use management.This study chose Kaifeng as pilot city and measured soil moisture,soil pH,NH4+,NO3-,total carbon,total nitrogen,organic carbon,dissolved organic carbon,microbial biomass carbon,microbial biomass nitrogen,microbial respirationand its temperature sensitivity in different land use types,including old-field,grassland,orchard,farmland,and forest inHuang-Huai-Hai Plain.The results showed that:(1)All soil moisture,total carbon,total nitrogen,organic carbon(1.48%),microbialbiomass carbon and nitrogen in forest were significantly higher than that in other land use types.However,microbial respiration(101.06mg·kg-1·d-1)and its temperature sensitivity(1.18)were minimum.(2)Soil total carbon,total nitrogen,organic carbon,microbial biomass carbon and nitrogen in farmland were lower than that in forest,but higher than that in other land use types.Microbial respiration rate(128.55mg·kg-1·d-1)was high in farmland.(3)Soil carbon,nitrogen,and microbial carbon and nitrogencontents in old-field,grassland,and orchard were less than forest and farmland.And(4)structural equation model showed that landuse type directly explained68%of soil organic carbon and indirectly influenced soil organic carbon and microbial respirationthrough soil moisture.Soil organic carbon and microbial respiration were explained93%and54%,respectively,by soil moisture andNO3-.The results indicate that forest ecosystem will facilitate soil organic carbon sequestration,and their minor temperaturesensitivity of microbial respiration will be of great importance in countermeasure of global climatic change in future.Farmland coverlarger area.Carbon sink function should be developed by no-tillage and straw return in agricultural management in the meantime ofcrop production are protected.