川中丘陵区冬水田种植模式转旱作土壤呼吸组分特征及碳平衡

冬水田-水稻是川中丘陵区传统的稻田种植模式,冬水田种植模式转变是实现多熟种植及机械化的重要途径。为探究冬水田-水稻种植模式转旱作过程中作物季及休闲期土壤呼吸速率及其组分构成,试验设置冬水田-水稻转旱作(FTD)、冬水田-水稻(FR)和冬闲田-玉米(FM)3种不同种植模式,采用根排除法和静态明箱-气相色谱法原位取样测定作物季及季后休闲期土壤呼吸及其组分,并通过测算净生态系统生产力(NEP)进而判断冬水田-水稻转旱作过程的农田系统碳汇强度。结果表明:(1)FTD显著提高了土壤总呼吸速率及其自养和异养呼吸速率,从而提高了其累积排放量(P<0.05)。与FR相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了13.14倍、11.32倍和15.56倍(P<0.05);与FM相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了70.56%、40.83%和115.47%(P<0.05)。(2)与FR和FM相比,FTD均降低了土壤呼吸及其组分的温度敏感性(Q₁₀),且土壤总呼吸的温度敏感性介于异养呼吸和自养呼吸之间。(3)FR,FM和FTD的净生态系统生产力(NEP)均为正值,其数值分别为7911.66 kg/hm²,5667.89 kg/hm²和1583.46 kg/hm²,均表现为大气CO₂的碳汇,但与FR与FM相比,FTD显著降低了其净生态系统生产力,呈现出较弱的碳汇。

Carbon balance and characteristics of soil respiration components during the transition from paddy field to upland in the hilly region of central Sichuan

Winter paddy field-rice is a traditional rice planting pattern in the hilly areas of central Sichuan Province. The transformation of winter paddy field-rice planting pattern is an important measure to promote multi-cropping and mechanized cropping production. To investigate the soil respiration rate and its composition during crop season and fallow period during the transition from winter paddy field-rice to upland cropping (FTD), three different cropping patterns were set up in this experiment, including paddy field-rice to upland cropping (FTD), paddy field-rice (FR), and fallow field-corn (FM). Root removal method and static chamber gas chromatography were used to determine soil respiration and its components in crop season and fallow period after crop was harvested. The intensity of farmland carbon sink of FTD was evaluated by calculating net ecosystem productivity (NEP). The results showed that: (1) the total soil respiration rate, autotrophic respiration rate and heterotrophic respiration rate significantly increased in FTD than FR and FM (P<0.05). Compared with FR, the cumulative emissions amount of total soil respiration, autotrophic and heterotrophic respiration increased by 13.14 times, 11.32 times, and 15.56 times, respectively (P<0.05); Compared with FM, the cumulative emissions amount of the total soil respiration, autotrophic and heterotrophic respiration increased by 70.56%, 40.83% and 115.47%, respectively (P<0.05). (2) The respiration temperature sensitivity (Q₁₀) value of total soil respiration, autotrophic respiration and heterotrophic respiration decreased in FTD than FR and FM. Meanwhile Q₁₀ value of total soil respiration was between heterotrophic respiration Q₁₀ value and autotrophic respiration Q₁₀ value. (3) The NEP of FR, FM and FTD were positive, and their values were 7911.66 kg/hm², 5667.89 kg/hm² and 1583.46 kg/hm², respectively. The three plant patterns were all the carbon sink of atmospheric CO₂. Whereas, because the NEP in FTD was significantly lower than FR and FM, it only showed a weak carbon sink in FTD than that in FR and FM.