砾石覆盖条件下土壤水热效应对冬小麦田CO2排放的影响

通过2年田间试验,采用静态暗箱-气象色谱法监测冬小麦田CO_2排放速率和通量,并计算了生态系统净交换和收获指数。试验设置无覆盖对照(CK)、无覆盖补灌对照(WCK)、砾石覆盖(GM)和砾石覆盖补灌(WGM)4个处理。结果表明:2个生长季内砾石覆盖补灌处理各阶段土壤含水率和温度平均最高,其次为砾石覆盖处理,说明砾石覆盖的保水保温效果明显;土壤温度的变化规律与CO_2排放规律相同,土壤含水率变化规律与CO_2排放规律相反,土壤温度和含水率变化对CO_2排放具有显著的交互作用(P0.05);对影响农田生态系统CO_2排放的冬小麦生长参数和土壤理化特性进行相关矩阵和主成分分析,CO_2排放的分布与CK和WCK对照处理分布相似度较高,与GM和WGM砾石覆盖处理则完全相反;产量、收获指数、生态系统净交换的分布与WGM处理最为接近,其次为GM处理,说明砾石覆盖处理提高了产量,促进了生态系统净交换,降低了CO_2排放量。砾石覆盖结合关键生育期补充灌水的田间管理方式能有效改善土壤水热状况,减少农田生态系统CO_2排放。

Impacts of Soil Water and Temperature Effects on CO2 Emissions in Winter Wheat Field under Gravel Mulching Condition

Gravel mulching technology, as one of the most important field management techniques, has been long applied by farmers in dry areas to decrease water evaporation and maintain soil temperature, which can also improve crop production in the arid and semi-arid regions. Studying on the influences of gravel mulching on soil water and temperature as well as ecosystem CO2 emissions will play an important role in assessing farmland ecological effects of gravel mulching. A winter wheat field experiment over two-year periods was carried out and annual CO2 emission was monitored with a static opaque chamber and chromatography method, and the net ecosystem exchange and harvest index were calculated. In the experiment, four field treatments were applied, including CK (control with no mulching), WCK (supplementary irrigation with no mulching), GM (gravel mulching with no irrigation), and WGM (gravel mulching with supplementary irrigation). Compared with the control treatments, the gravel mulching treatments can significantly increase the soil temperature and moisture, for specific performance, WGM was the largest, and followed by GM. Consequently, gravel mulching exerted greater effect on soil water and temperature. Seasonal dynamics of CO2 emissions generally followed the change of soil temperature with high peaks of CO2 fluxes from April to June in both years, whereas CO2 fluxes went conversely with soil water content change over the two years. Statistical analysis also showed that soil temperature and soil moisture had significant interactions on CO2 emissions at P<0.05 level. By the correlation matrix and principal component analyses, the distribution of CO2 emissions was the closest with the two control treatments (CK and WCK), and the farthest with the two gravel mulch treatments (GM and WGM). The gravel mulching practice, particularly the WGM treatment, can significantly influence the distribution of winter wheat growth parameters such as yield, harvest index, net ecosystem exchange and so on. The above mentioned results indicated that the gravel mulching technology had the potential to increase winter wheat yield, promote net ecosystem exchange and reduce CO2 emissions from ecosystem. All in all, gravel mulching combined with supplemental irrigation in the key growth stages could effectively improve soil hydro-thermal conditions, and reduce CO2 emissions from farmland ecosystems.