避灾露营对城市公共绿地土壤呼吸的短期影响

2008年5月12日四川汶川发生里氏8．0级大地震后，城市居民大规模在公共绿地上露宿避灾，而这些强人为干扰活动对绿地植被和土壤影响的科学研究却十分少。选择不同时间露营点和出入帐棚必经的践踏区域，测量土壤CO2通量的变化及相关环境因子（空气温湿度、土壤容重、孔隙度和微生物生物量等）。结果发现土壤CO2通量明显地受露营和人为践踏的影响，露营和人为践踏区土壤CO2通量明显地低于对照区。随着露营的增加，土壤CO2通量呈现先降低（大约10d后）后略有增加（大约20d后），后期又下降的趋势（大约25d后）。在露营区，土壤紧实和遮荫是土壤CO2通量减少的两个主要过程，在早期，严重遮荫后引起根系呼吸下降是主要过程，而在后期，随着人入睡帐棚次数的增加，土壤紧实是控制土壤CO2通量的主要过程；而在践踏区，踩踏引起土壤紧实是土壤呼吸下降的主要原因。因此地震露营避灾后退化草坪恢复的一个关键措施是松土改善土壤的物理状况。

The short-term effect of field camping on soil CO2 efflux in urban grassland

On 12 May, 2008, a great sized earthquake of magnitude Ms= 8.0 occurred in Wenchuan County, Sichuan Province, southwest China. Many residents established a great of tents on all urban public and residential greenbelt for searching safe sites. However, there are few reports about the effect of these activities on soil and vegetation. We determined soil CO2 efflux and relative environmental factors (i.e., bulk density, porosity, air temperature and humidity, and microbial biomass)in the field camping sites of different established time and trample area. Soil CO2 efflux was significantly affected by field camping and trample. Soil CO2 efflux was significantly lower in the different field camping sites and trample area than in CK treatment. Soil CO2 efflux decreased firstly (after about 10 days), then increased little (after about 20 days) and again decreased (after 25 days) following field carmping time increasing. Soil compaction and shade was two main processes controlling soil CO2 efflux in field camping sites. In early periods, shade that caused root respiration decline was main process. With the increase of extent of compaction, soil physical properties were main factors. In trample area, soil compaction was main process that affected soil CO2 efflux. So, scarification that improved soil physical properties was the first work to restore degraded urban grassland after 5.12 Wenchuan great earthquake.