青海湖北岸高寒草甸草原非生长季土壤呼吸对温度和湿度的响应

Effect of grazing exclusion on soil respiration during the dormant season in alpine meadow grassland ecosystems on the northern shore of Qinghai Lake,China

非生长季土壤呼吸是生态系统碳循环的重要组成部分,显著地影响着碳收支。本研究利用Li-8100开路式碳通量测定系统,研究了青海湖北岸高寒草甸草原非生长季土壤呼吸对短期围栏封育(自由放牧,3年围栏封育和5年围栏封育样地)的响应,并讨论了温度和湿度对非生长季土壤呼吸的影响。结果表明,1)自由放牧、3年围栏封育和5年围栏封育样地非生长季土壤呼吸平均速率分别是全年土壤呼吸平均速率的0.21,0.22和0.19倍;2)自由放牧、3年围栏封育和5年围栏封育样地非生长季土壤呼吸所排放的碳量分别为117.2,109.2和100.7g C/m2,占全年土壤呼吸所排放的碳量的21.2%,22.3%和23.2%;3)相比于生长季和全年土壤呼吸的温度敏感性,非生长季具有更低的土壤呼吸温度敏感性;4)非生长季土壤温度和土壤湿度对土壤呼吸的解释率相当,一定的土壤湿度是保证土壤呼吸对温度响应的必要条件。因此,当考虑到碳收支和生态系统碳循环时不能忽略掉非生长季土壤呼吸的作用,而且水分在调节非生长季土壤呼吸中起着重要的作用。

Dormant season soil CO2 efflux is a significant component of the ecosystem carbon cycle and it therefore plays an important role in carbon budgets calculated to address global climate change.This study investigates the response of dormant season soil CO2 efflux to short-term grazing exclusion.It also explores the impacts of soil temperature and moisture on soil respiration using the Li-8100 system.Soil respiration was studied in three blocks-free-range grazing（FG）,grazing exclusion for 3years（GE3）,and grazing exclusion for 5years（GE5）.Respectively,the average dormant season soil respiration was 0.21,0.22,and 0.19 times of the annual average soil respiration in each of the three blocks.The carbon released by soil respiration during the dormant season was 117.2,109.2and 100.7g/cm^2,accounted for 21.2%,22.3% and 23.2% of the amount of annual carbon released from soil for FG,GE3 and GE5,respectively.The Q10 values during the dormant season were lower than both the annual and growing season scores.Soil temperature and moisture almost equally account for the variation in soil respiration,and a certain amount of soil water content is necessary for maintaining the response of soil respiration to soil temperature.Therefore,when considering the carbon budget and cycle of ecosystems,we cannot ignore dormant season soil respiration;and soil moisture plays a considerable role in regulating this process.