一年生植物功能群对放牧草原生物量和土壤呼吸的影响

Effects of annual plant functional group on biomass and soil respiration in agrazing community of a typical steppe grassland

作为草原群落重要层片的一年生植物功能群,在湿润季节和年份高度发育补偿群落生物量、维持放牧草原生态系统稳定,但尚不清楚一年生植物功能群通过这一补偿方式如何补偿群落地上/地下生物量和影响土壤呼吸。基于2012年和2013年内蒙古锡林郭勒大针茅(Stipagrandis)+羊草(Leymus chinensis)典型草原两个放牧强度试验样地群落地上/地下生物量、土壤呼吸及相关环境因子的测定。研究表明,1)一年生植物功能群对群落生产力的补偿作用及生长季土壤呼吸累积量在湿润年份(2012年)均大于干旱年份(2013年);且在中度放牧处理中均显著大于轻度放牧处理(P<0.05);2)土壤呼吸与一年生植物功能群地上、地下生物量、土壤5cm温度和土壤0-10cm含水率均具有极显著正相关关系(P<0.001)。由此表明,当放牧降低了草原群落多年生功能群生物量时,一年生植物功能群在湿润季节和年份可补偿群落生产力、促进土壤呼吸排放速率,进而影响草原生态系统碳循环过程。

As a critical synusia in steppe grasslands,annual plant functional groups can compensate for changes in community biomass and maintain its stability in wet seasons and across years.This compensation should be evident because they are more sensitive to precipitation than perennial plant functional groups,especially in grazing communities with low biomass of perennial plant functional groups.However,it is not clear how the compensation effects of the annual plant functional groups improve productivity and affect soil respiration（Rs）in grazing areas in the steppe.We conducted a 2-year grazing experiment,including light-grazing（L）and moderate-grazing（M）treatments,in a typical steppe in Inner Mongolia in 2012 and 2013.Above-ground biomass（AGB）,under-ground biomass（UGB）,Rs,and environmental factors were monitored during the growing season.We found that：1）either compensation of the annual plant functional groups occurred in the AGB and UGB,or Rs was higher in the wet year（2012）than in the dry year（2013）;2）both compensation effects in the annual plant functional groups in the AGB and UGB and Rs were significantly greater in moderate-grazing than light-grazing;3）Rs was positively correlated with both the AGB and UGB of the annual plant functional groups,as well as with soil temperature and moisture（P〈0.001）.This study showed that grazing utilization decreased biomass of the perennial plant functional groups,and the annual plant functional groups dramatically developed in wet seasons and years to compensate for loss in community biomass to improve productivity and maintain ecosystem stability,which as a principal biotic mechanism that affects the ecosystem carbon cycle in grasslands.