北方典型设施菜地土壤CO2排放特征

为研究我国北方典型设施菜地的土壤CO₂排放特征及其影响因素，通过原位监测手段，研究山东省寿光市农田转变为不同种植年限（6、12 a）设施菜地及设施菜地荒废12 a后土壤CO₂排放规律及影响因素.结果表明:①种植6 a设施菜地较农田具有较高的土壤CO₂排放量，可能是由于设施菜地种植过程中大量施加有机肥造成的，并且设施菜地土壤温度及含水率较高，增加了土壤蔗糖酶活性，加剧土壤CO₂排放.②当种植年限超过10 a，设施菜地施肥量减少，降低了土壤微生物可利用底物的供应.因此，种植12 a设施菜地土壤CO₂排放量降至农田水平.③种植6 a设施菜地土壤的w（DOC）（DOC表示水溶性有机碳）比农田较高.④土壤CO₂排放年内分配不均匀，表现为农田及荒废设施菜地土壤CO₂排放主要集中在5—8月，其排放量占全年的75.09%、87.02%，峰值出现在7月.种植6 a设施菜地土壤CO₂排放主要集中在5—8月和11月—翌年2月，两阶段排放量分别占全年的48.48%、42.34%，峰值分别出现在7月、12月.研究显示，农田转变为设施菜地短期（种植6 a）内可显著促进土壤CO₂排放及DOC的输出，但随着种植年限延长至12 a，土壤CO₂排放降至农田水平. 

CO2 Emissions from Typical Greenhouse Soils in Northern China

In order to study the effects of land use change on CO₂ emissions and its influencing factors, the CO₂ flux rates and environmental factors were studied in farmland greenhouse soil cultivated for 6 and 12 a, as well as greenhouse soil that was abandoned for 12 a. The results showed that:(1) The highest CO₂ emission rates existed in the soils of greenhouse soil cultivated for 6 a. More fertilizers, higher soil temperature and higher soil moisture could enhance the soil invertase enzyme activities in the treatment, then increase the CO₂ released from soils. (2) After more than ten years'' cultivation, the application of organic manure could be reduced in the greenhouse. This could reduce the supply of available substrates for microbial decomposition. Then, the annual CO₂ emissions in greenhouse soil cultivated for 12 a decreased to the level of farmland. (3) The concentrations of dissolved organic carbon (DOC) in greenhouse soil cultivated for 6 a were higher than those in farmland. (4) The CO₂ emission patterns were different between the treatments. The percentages of annual CO₂ emissions occurring from May to August were 75.08% in farmland and 87.02% in greenhouse soil that was abandoned for 12 a, and peak values of CO₂ emissions occurred in July in these treatments. CO₂ in greenhouse soil cultivated for 6 a was mainly released from May to August (48.48%) and from November to the next February (42.34%), and peak values of CO₂ emission occurred in July and December, respectively. In conclusion, land use change from farmland to greenhouse soil cultivated for 6 a enhances CO₂ emissions and soil DOC production. However, CO₂ emissions decrease with years of cultivation. After 12 years of cultivation, CO₂ emission decrease to the level of farmland.