放牧对草原生态系统地下生产力及生物量的影响

Influence of Grazing Pressures on Belowground Productivity and Biomass in Mongolia Steppe

放牧作为一种人类活动的干扰因子,主要通过动物的采食、践踏及其排泄物的输入对草原生态系统产生影响,这些影响直接作用于草原生态系统的地上部分和土壤,从而影响草原生态系统的物质生产和分配,进而影响到地下生产力和生物量.以蒙古克氏针茅 Stipakrylovii -冷蒿 Artemisiafrigida 草原为研究对象,对自由放牧区和围栏禁牧封育区草原生态系统地下生产力、生物量进行了比较研究.结果表明:自由放牧区草原生态系统地下生产力为147.6g·m-2·y-1,围栏禁牧封育区地下生产力达187.3g·m-2·y-1,二者地下生产力差异显著 α=0.05 ,说明封育保护可以提高过牧草原生态系统的地下生产力.地下生物量在自由放牧区为2032.6g·m-2,其中活地下生物量占54.9%,死地下生物量占45.1%;在围栏禁牧封育区平均为2071.8g·m-2,其中活地下生物量占56.4%,死地下生物量占43.6%,两者没有明显差异.地下生物量在土壤中垂直分布规律在两个试验区均表现为自地表向下呈指数函数减小,主要集中分布在0～30cm的土层.

Grazing,as one of disturbing factors of human activities,imposes influences on grassland ecosystem through the behavior of feeding,tramping and excreting from animals.These influences give the effect on aboveground of plants and soil in grassland ecosystem,consequently on matter production and distribution of grassland ecosystem,resulting in the change of belowground biomass and productivities.This study aims to discuss the effect of grazing on belowground biomass and productivities of grassland ecosystem in Mongolia Steppe.The results showed that belowground biomass in grazing free plot averaged 2 071.8 g·m^(-2)·y^(-1) in which living biomass accounted for 56.4% and dead biomass accounted for 43.6%;the belowground biomass of grazing plot averaged 2 032.6 g·m^(-2)·y^(-1),in which living biomass occupied 54.9% and dead biomass occupied 45.1%.The protection through prohibiting grazing showed no significant influence on belowground biomass.The vertical distribution of belowground biomass decreased exponentially with the increasing of soil depth.The belowground biomass mainly distributed in 0~30 cm soil depth.During the growing season (from June to September) the accumulated belowground biomass was 187.3 g·m^(-2)·y^(-1) and 147.6 g·m^(-2)·y^(-1) in grazing free plot and grazing plot respectively.The belowground growth amount in grazing free plot was significantly higher than that in grazing plot,which illustrated that protection from prohibiting grazing can raise belowground growth amount of grassland ecosystem.At the same time,litter bag method was used to measure decomposition rate of belowground litter.Weight loss rate of litter decomposition was only 17% within 105 days after the experiment was conducted.No significant difference of decomposition rate between grazing free plot and grazing plot was found.