川西亚高山川滇高山栎林火烧迹地土壤呼吸特征及其影响因素

Soil Respiration Characteristics and Impacting Factors in Burned Area of Quercus aquifolioides in Western Sichuan,China

【目的】探究川西亚高山森林火烧迹地土壤总呼吸速率(Rs)和异养呼吸速率(Rh)的季节动态及其影响因素,比较火烧迹地与对照样地Rs和Rh的变化,为火干扰条件下森林土壤碳循环及其碳排放估算提供依据。【方法】以火烧8年后的川滇高山栎林火烧迹地和对照原始林为研究对象,于2010年9月—2011年12月采用LI-8100A土壤碳通量自动测量系统,通过挖壕沟方法测定Rs及Rh,同时测定5 cm深处的土壤温度(T5)和土壤体积含水量(W5),分析Rs和Rh与非生物因子的关系。【结果】休眠季火烧迹地Rs和Rh均显著高于对照样地(P<0.05),而生长季和全年Rs和Rh与对照无显著差异(P>0.05);T5与Rs和Rh呈极显著的指数正相关关系(P<0.01);W5仅在生长季与对照Rs和Rh相关性不显著(P>0.05),其余时间均对Rs和Rh产生显著影响(P<0.05),即W5低于25.8%时对Rs和Rh产生显著影响(P<0.05),超过37.7%时其影响作用不显著(P>0.05);T5和W5双因子与Rs和Rh的拟合模型明显优于单因素模型,表明该区域土壤碳排放受T5和W5的协同影响;不同季节火烧迹地的温度敏感性(Q10)均低于对照样地,且Rh的Q10最小,Rs的Q10最大;火烧迹地土壤硝态氮、轻组有机碳和颗粒有机碳含量对Rs和Rh的影响大于对照;火烧迹地Rs和Rh年累积量相比对照样地分别高13.9%和1.8%。【结论】火烧迹地土壤碳排放对温度变化的敏感性低于未过火林地,在评估和构建川西亚高山土壤碳排放模型时,应考虑火干扰林地和土壤底物代谢水平。

【Objective】To analyze the influence of environmental factors on total soil respiration rate（ Rs） and heterotrophic respiration rate（ Rh） and their seasonal dynamics of burned forest area in the subalpine regions in western Sichuan,China. By comparing the rate of Rsand Rhbetween burned area and control plot（ CK）,the results would provide a basis for comprehending the forest carbon cycle and estimation of soil C fluxes under the condition of fire disturbance.【Method】In this study,the burned area（ 8 years since fire） Quercus aquifolioides and control plots（ CK） of subalpine forest in Western Sichuan were studied. Using a field setup through root exclusion method and LI-8100 automated soil CO2 flux system,we measured Rsand Rh,soil temperature（ T5） and soil gravimetric water content（ W5） at5 cm depth from September 2010 to December 2011. Relationships of Rsand Rhwith abiotic factors were determined by fitting both an exponential model and a two-factor model.【Result】In dormant season,Rsand Rhrates for the burned areawere obviously higher than those of control plot（ P 〈 0. 05）,respectively. However,Rsand Rhwere not different between the burned area and the control plot in growing season and whole year（ P 〉 0. 05）. A significant exponential relationship was found between Rsor Rhand T5 in different seasons,respectively（ P 〈 0. 01）. There was a significant relationship between Rsor Rhand W5,but no significant effect was observed of W5 on Rsor Rhin the CK plot during growing season.We found that Rsor Rhappeared to be a inhibition phenomenon by W5 when it was low than 25. 8%,but there was no significant relationship when it was over 37. 7%（ P 〉 0. 05）. Notably,T5 and W5 two-way model was better than the single factor model. Therefore,soil carbon emission was significantly affected by T5 and W5 in the subalpine forest.Furthermore,the soil temperature sensitivity（ Q10） values of Rsand Rh from the burned area were lower than those of in the CK plot,whereas Rs are more sensitive to T5 in different seasons. Moreover,Rsand Rhof burned area and CK were strongly correlated to nitrate nitrogen,light fraction organic carbon and particulate organic carbon at 0-30 cm soil layers.The estimated values of Rsand Rhfor burned area was 13. 9% and 1. 8% higher than those for control plot.【Conclusion】Our study indicated that Rsand Rhwere dominated by interaction of T5 and W5. We can infer that soil carbon emission of burned area may be less sensitive to temperature variations than the CK under global warming scenarios. Our results emphasize that fire disturbance in forest land and associated carbon metabolisms should be taken into consideration in the model construction under climate change scenarios.