放牧强度对青海海北高寒矮嵩草草甸碳交换的影响

以禁牧、轻度放牧、中度放牧和重度放牧4种不同放牧强度的高寒矮嵩草草甸为研究对象,分别于2014年和2015年植物生长季5～9月,使用LI-6400便携式光合仪和同化箱测定生态系统净CO_2交换(NEE)和生态系统呼吸(ER),并利用土壤温湿度自动记录仪测定土壤10cm处的温度和体积含水率,以研究放牧强度对青海海北高寒矮嵩草草甸碳交换的影响。结果表明:生长季5～9月,试验地10cm土壤温度的变化范围在7.21～13.23℃,随放牧强度增大而增大;体积含水率在19.68%～32.33%间波动,随放牧强度增大而减小。高寒草甸NEE在生长季表现出明显的"V"型变化,5月NEE最大,为1.43μmolCO_2/m^2·s,此时草地仍处于碳排放状态,7月最小(碳吸收速率最大),为-14.32μmolCO_2/m^2·s,吸收强度表现出随放牧强度增大而增大的趋势;ER呈倒"V"型变化规律,7月最大,为12.15μmolCO_2/m^2·s,放牧强度仅对7月的ER产生影响,其余月份4个样地差异均不显著。相关分析表明,NEE与土壤温度和绿体生物量极显著负相关,相关系数分别为-0.910和-0.559,与土壤湿度显著正相关,相关系数为0.559;ER与土壤温度和绿体生物量显著正相关,相关系数分别为0.824和0.453,与土壤有机碳含量极显著负相关,相关系数为-0.605,与土壤湿度、枯体生物量和全氮含量相关不显著。

Effects of Grazing Density on Ecosystem CO_2 Exchange of Haibei Alpine Kobresia humilis Meadow in Qinghai

In order to study the influence of grazing density on carbon exchange of alpine Kobresia meadow, net ecosystem CO2 exchange (NEE) and ecosystem respiration (ER) was measured by LI-6400 and carbon assimilation chamber under four different grazing density (Forbidden grazing, light grazing, moderate grazing and heavy grazing) during the plant growing season of 2014 and 2015.The temperature and volumetric moisture content at 10cm of soil were measured by an automatic soil temperature and humidity recorder.The results showed that 10cm soil temperature changes in the range of 7.21~13.23℃, and with the grazing intensity increases;the volume moisture content fluctuated from 19.68% to 32.33% and with the grazing intensity decreased.NEE of alpine meadow showed obvious "V" type change during the growing season.The maximum value of NEE was 1.43μmol CO2/m^2·s in May, and the grassland was still in the state of carbon emission.The minimum valve (The maximum carbon absorption rate) was -14.32 μmol CO2/m ·s in July, and the absorption intensity increased with the increase of grazing intensity.ER showed an inverted "V" pattern, with the maximum value at 12.15μmol CO2/m^2·s in July.Grazing intensity only affects the ER in July and the differences of ER between the four plots were not significant in the other months.The correlation analysis showed that NEE had significant negative correlation with soil temperature and fresh biomass, with correlation coefficients of -0.910 and -0.559, respectively, and had significant positive correlation with soil water content, with correlation coefficient of 0.559.ER had significant positive correlation with soil temperature and fresh biomass, with correlation coefficients of 0.824 and 0.453, respectively, and had significant negative correlation with soil organic carbon content, with correlation coefficient of -0.605.It had no significant correlations with soil water content, litter biomass and soil nitrogen content.