| Human impact on natural ecosystems is causing extensive biodiversity loss. The loss of biodiversity has become a major topic of concern in recent decades, and numerous researches have been devoted to understanding the consequences of ecosystem simplification. Changes in plant diversity are known to affect ecosystem functioning, including aboveground arid belowground. Microbial communities, inhabiting soil, are vital to soil quality and functioning due to their involvement in organic matter dynamics, nutrient cycling and decomposition processes. In the past decades, the aboveground and belowground components of ecosystem have traditionally been considered in isolation from one another and few studies have experimentally investigated the influence of plant diversity on soil microorganisms. Now there is increasing recognition of the influence of these components on one other and of the fundamental role played by aboveground and be-lowground feedbacks in controlling ecosystem processes and properties. The subalpine coniferous forest is considered as an important gene pool and reservoir in the upper reaches of the Yangtze River, due to its well known ecological status. However, Changes in plant diversity how to influence soil microorganism in subalpine coniferous forests is still uninvestigated. In order to stimulate plant diversity loss, we used a 'removal experiment' approach, manually removed herb (HR) and shrub (SR) layer of spruce plantation. Through studied on soil microorganism and soil enzyme activities, we found that:The quantity of aerobic bacteria, actinomycetes, fungi and total microorganism in herb removal and shrub removal treatment were less than control, the aerobic bacteria was the most, the actinomycetes took the second place, the fungi was the least. The quantity of aerobic bacteria, actinomycetes, fungi and total microorganism of herb removal treatment were greater than shrub removal treatment. Soil microbes showed seasonal variation, were the highest in August and the lowest in October.Layer removal had significant effects on microbial biomass carbon (MBC) and nitrogen (MBN) in soil. The average content microbial biomass carbon and nitrogen in herb removal and shrub removal treatment were less than control. The average content microbial biomass carbon and nitrogen in shrub removal were less than herb removal treatment. At the same time, soil microbial biomass carbon and nitrogen showed seasonal variation as well, which were the highest in August and the lowest in October.The average content of soil organic carbon in herb removal treatment and shrub removal treatment were less than control. The content of soil organic carbon in herb treatment was greater than that in shrub removal treatment. At the same time, the content of soil organic carbon of spruce plantation had a trend, which is gradually declining, highest in October of 2008, lowest in August of 2009. In this study, we also found that layer removal of spruce plantation could change the soil microbial metabolic quotient (Cmic /Corg). Except in the treatment of herb treatment of April of 2009, the soil microbial metabolic quotient of all treatments was higher than control in October of 2008 and August of 2009. Besides, soil microbial metabolic quotient had seasonal variation, which was the most in August of 2009 and lowest in October of 2008.The removal of herb and shrub layer in spruce plantation changed soil enzyme activities. The relationship of invertase activity in October and April in all plots was: CK>HR>SR. However, the relationship of invertase activity in August was:HR≈SR>CK. The removal of herb and shrub in spruce plantation declined urease activity. In study period, the relationship of urease activity was: CK>HR>SR. In April of 2009, urease activity reached the peak value. The relationship of Cellelase activity in all treatment was: CK>HR>SR, highest in August of 2009, lowest in October of 2008. In October of 2008 and April of 2009, the relationship of activity of dehydrogenase between all treatments was: CK>HR>SR. However, in August of 2009, the relationship of activity of dehydrogenase between all treatments was:CK>SR>HR. In October of 2008 and April of 2009, the activity of invertase, urease, cellelase and dehydrogenase between all treatments had a same trend. That was:CK>HR>SR.The relationship of soil respiration rate between all treatments was:CK>HR>SR, in April of 2009. But in August of 2009, the relationship of soil respiration rate between all treatments was:CK |
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