川西平原灌区不同水旱轮作模式周年土壤呼吸特征

Annual soil respiration characteristics of different paddy-upland rotations in irrigation areas of the Western Sichuan Plain

水旱轮作是川西平原灌区重要的稻田种植模式,为探究本区域不同水旱轮作模式对周年土壤呼吸的影响,在四川崇州设置蒜稻(GR)、麦稻(WR)和油稻(RR)三种水旱轮作模式,采用静态箱气相色谱法测定不同模式周年土壤呼吸,并同步测定温度、水层高度等水热生态因子。结果表明:三种轮作模式周年土壤呼吸累积排放量表现为 GR>RR>WR,分别为 193.36、160.27、157.28kg/hm^2;土壤呼吸速率日动态规律基本一致,均表现为单峰型变化趋势,最高值出现在12:00-15:00,6-8月的日变幅高于其余月份;土壤呼吸速率季节动态均呈双峰型变化趋势,在 6 月和 9 月达到峰值,其中 GR 模式土壤呼吸速率年均值最高;三种模式土壤呼吸速率均受 0-10 cm、10-20 cm 土壤温度的显著影响,而与土壤含水量无显著相关性。土壤温度是旱季土壤呼吸速率季节变化的主要影响因素,土壤水层深度和土壤温度共同作用影响了稻季土壤呼吸速率的变化。

Paddy-upland rotation is the main cropping system in the irrigation area of the Western Sichuan Plain. In order to investigate the effects of different paddy-upland rotations on the annual soil respiration in this region, static chamber-gas chromatography was used to measure the soil respiration of garlic-rice (GR), wheat-rice (WR), and rape-rice (RR) models. The hydrothermal ecological factors, including the temperature and water layer height, were determined at the same time. The results showed that the cumulative discharges of soil respiration in the three rotation models were in the order of GR > RR > WR, at 193.36, 160.27, and 157.28 kg/hm^2, respectively. The daily dynamics of soil respiration were basically the same;all showed the unimodal variation trend, and the highest value appeared at 12:00-15:00. The daily variation from June to August was higher than that in the other months, and the seasonal dynamics of soil respiration showed a bimodal trend, with peaks in June and September. The annual average soil respiration rate of the GR model was the highest;the soil respiration of the three models was significantly affected by soil temperature at 0-10 cm and 10-20 cm, but there was no significant correlation with soil water content. Soil temperature is the main influencing factor of seasonal variation in soil respiration in the dry season, while a combination of soil water depth and soil temperature affects the variation in soil respiration in the rice growing season.