模拟增温条件下翻耕免耕农田土壤CH4通量响应

为研究未来气候变暖下我国华北翻耕、免耕农田CH4通量响应,评估该地农田碳汇/源情况,使用远红外辐射增温仪模拟气候变暖,设计翻耕增温(CTW)、翻耕不增温(CTN)、免耕增温(NTW)、免耕不增温(NTN)4个处理。研究表明,2013—2015年小麦-玉米季,增温分别显著提高翻耕、免耕农田10 cm土壤温度1.5℃和1.4℃(P0.05);但对两种耕作农田土壤水分的影响并不显著(P0.05)。各处理土壤CH4通量无明显季节变化,但累积CH4吸收具有显著年际差异。2013—2014年小麦季,CTW和NTW相比CTN和NTN处理,累积CH4吸收分别显著增加35.8%和108.8%(P0.01);但在2014—2015年,CTW处理显著降低17.7%(P0.05)。两年玉米季,处理间累积CH4吸收无显著差异(P0.05)。各处理土壤微生物生物量碳(MBC)含量与CH4存在显著正相关关系。未来气候变暖条件下,翻耕农田MBC含量减小将可能减缓华北农田CH4吸收。

Responses of soil CH4 fluxes to simulated warming in conventional tillage and no-tillage systems

Methane(CH4)is one of the most important greenhouse gases contributing to climate warming. Understanding the responses of cropland soil CH4 fluxes to climate warming under different tillage systems is critical to evaluation of the dynamics of soil carbon sink/source along with climate changes in the North China Plain(NCP). A field experiment of simulated climate warming using infrared radiation in-strument was conducted to measure CH4 fluxes from the wheat-maize rotation field with four treatments including conventional tillage with and without warming(CTW and CTN)and no-tillage with and without warming(NTW and NTN). Results showed that during wheat-maize growing period in 2013—2015 soil temperature at 10 cm soil depth was significantly elevated by 1.5 ℃ in CTW, and 1.4 ℃ in NTW, com-pared with CTN and NTN, respectively(P﹤0.05). The warming did not significantly affect soil moisture in these two tillage systems because of irrigation(P﹥0.05). Furthermore, soil CH4 fluxes did not show obvious seasonal changes among treatments. However, annual cumulative soil CH4 uptake showed significant differences among years. During wheat season in 2013—2014, the cumulative CH4 uptake in CTW and NTW increased by 35.8% and 108.8%, compared with those in CTN and NTN, respectively(P﹤0.01). During 2014—2015, however, it was reduced by 17.7% in CTW, compared with CTN(P﹤0.05). During maize season in two years, cumulative CH4 uptake was not signifi-cantly affected by experimental warming in two tillage systems(P﹥0.05). In addition, a significant positive relationship between soil microbial biomass carbon(MBC)and CH4 uptake was found. Decreased MBC content in CTW indicated that the limitation of climate warm-ing projection on activity of soil organism may reduce the capability of soil CH4 sink in conventional tillage farmland of NCP.