旱改水型农田整治对土壤碳排放的短期影响

灌溉农业可提升粮食生产潜力，已成为全球农业重要的发展方向，但此类土地利用转换势必影响旱作农田土壤的稳定性，尤其是碳循环。然而，旱改水整治过程中土壤碳通量变化及其与环境因子间的互馈机制尚不清楚。为此，采用大田模拟实验，连续7 d监测土壤碳通量变化，评估旱改水整治对土壤碳库组成及环境驱动的短期效应。结果表明：①旱地、水田的土壤碳通量和温度均呈昼高夜低的单峰型曲线，且碳通量与温度峰值出现于每日13：00前后，但水田土壤碳通量稍高于旱地。②旱改水后短期内土壤可溶性有机碳（DOC）、微生物量碳（MBC）、易氧化有机碳（EOC）、惰性有机碳（ROC）、总有机碳（TOC）和土壤碳库管理指数均呈减少趋势，其中土壤微生物量碳、易氧化有机碳降幅分别达28.55%、29.09%。③土壤含水量、微生物OTU数、碳库含量是影响碳通量速率变化的关键因子（P<0.05），土壤温度、理化性状是制约土壤碳库的主控因子（P<0.05）。农业活动是重要的碳源之一，深入研究大范围旱改水诱发的碳排放问题可为低碳农业、气候减缓及其应对策略制定提供科学依据。

Short-term effects of land consolidation of dryland-to-paddy conversion on soil carbon flux

Irrigation agriculture has become an important developmental direction of the worldwide agricultural filed, because it could improve the food production capacity. Nevertheless, the conversion of land use pattern is guaranteed to affect the soil stability of dry farmland, especially for the soil carbon cycle. However, the mutual feedback mechanisms between carbon flux variation and environmental factors during the farmland consolidation process are still unclear. Therefore, to assess the short-term effects of dryland-to-paddy consolidation on the composition of soil carbon pool and environmental drivers, field experiments were carried out to monitor continuously the changes of soil carbon flux for 7 days. The results showed that:(1) the soil carbon flux and temperature in both dry land and paddy field presented as the unimodal curve of high day and low night. The peak values of soil CO₂ flux and temperature appeared around 13:00 every day, whereas the soil CO₂ flux of paddy field was slightly higher. (2) The soil dissolved organic carbon, microbial biomass carbon, easily oxidized organic carbon, resistant organic carbon, soil total organic carbon and soil carbon pool management index showed the decreasing trends after a short period of farmland consolidation, while the decrease rates of soil microbial biomass carbon and easily oxidized organic carbon were 28.55% and 29.09%, respectively. (3) The modeling results of structural equation models showed that soil water content, microbial OTU number, and soil carbon pool significantly affected the change of soil CO₂ flux (P<0.05). The soil temperature and soil physicochemical properties were the key environmental factors, which could constraint the soil carbon pool (P<0.05). The agricultural activities are one of the important carbon sources, and the depth study of carbon emissions induced by large-scale dryland-to-paddy might provide the scientific basis for low-carbon agriculture, climate mitigation and the formulation of coping strategies.