不同地表覆盖下低温季节对西南亚高山土壤微生物量碳动态的影响

Soil Biomass Carbon Dynamics of Subalpine Forest in Western Sichuan Province during the Cold Season

西南亚高山森林土壤是我国土壤碳密度最高区域之一,作为敏感的低温生态系统越来越受到关注。通过对均质化土壤重装土柱在积雪与凋落物覆盖(Control)、积雪覆盖(BNS)、凋落物覆盖(LNS)和裸露土壤(BNS)条件下原位培养,测定各处理0～10 cm和10～20 cm土壤微生物量变化。结果显示,低温季节亚高山土壤微生物量仍处于较高水平,显示低温季节是亚高山土壤生态过程重要时期;雪被和凋落物覆盖对亚高山森林土壤低温季节的微生物量碳影响显著,在0～10 cm土层control微生物量最高,裸地(BNS)最低,只有凋落物(LNS)或积雪覆盖(BS)处理介于二者之间;control在10～20 cm深度的土壤微生物量碳也维持较高水平。在低温季节不同覆盖处理下时间动态差异显著,对于0～10 cm土壤,BNS和BS呈单峰变化,即微生物量碳在低温季节中期显著高于前期和末期,LNS在低温季节前期显著低于后期含量,而control则是在低温季节中期显著低于前期和后期。效应和交互作用分析显示,土壤表面雪被、凋落物、培养时间和土壤深度对土壤微生物量碳的作用均显著,同时这4个因素之间也存在显著的交互作用。这显示全球暖化或者土地利用变化导致的地表覆盖和积雪消失,在短期内可能降低亚高山森林土壤微生物量,有助于土壤碳固存。

Subalpine forest in the southwestern of China, as one of the most important cold ecosystem with high sensitivity and altitude, and high density of soil organic carbon, attaches more and more attentions recently. Re- packed columns of homogenized subalpine forest topsoil （0 - 20 cm） were incubated onsite under three treatments, i.e. , bare soil without litter and snow cover （ BNS）, bare soil with snow cover （ BS）, snow-free soil with litter cover of 10 cm depth （LNS）, and control （soil with 10 cm litter and snow cover） to determined the impacts of sur- face coverage on soil microbial biomass （MBC） dynamics during the cold season. The results showed that content of MBC was bery high during the cold season, and turnover. Coverage of snowpack and litter indicating that cold season is an important period for soil C storage impacted MBC significantly, and MBC of the control is higher than other treatment during the mid and later period of cold season while the BNS （bare soil） is the lowest, suggesting that snowpack and litter cover improve the soil MBC significantly. The temporal fluctuations, and difference of MBC contents between 0 - 10 cm and 10 - 20 cm of the 3 treatments and control are also different during the cold season, and there were significant interactions between snowcover, litter cover, soil depth and sampling time on soil MBC. We conclude that snow and litter cover improved soil MBC due to insulating soil from adruptly temperature fluctuation and frequently freeze-thaw cycle, and disappearance of snowpack and litter under climate change and LUCC would reduce soil MBC, soil respiration, and organic carbon mineralization for subalpine forest soil during the cold season.