CO2浓度升高和施氮条件下小麦根际呼吸对土壤呼吸的贡献

依托FACE技术平台, 采用稳定¹³C同位素技术, 通过将小麦(C₃作物)种植于长期单作玉米(C₄作物)的土壤上, 研究了大气CO₂浓度升高和不同氮肥水平对土壤排放CO₂的δ¹³C值及根际呼吸的影响. 结果表明: 种植小麦后土壤排放CO₂的δ¹³C值随作物生长逐渐降低, CO₂浓度升高200 μmol·mol^-1显著降低了孕穗、抽穗期(施氮量为250 kg·hm^-2, HN)与拔节、孕穗期(施氮量为150 kg·hm^-2, LN)土壤排放CO₂的δ¹³C值, 显著提高了孕穗、抽穗期的根际呼吸比例. 拔节至成熟期, 根际呼吸占土壤呼吸的比例在高CO₂浓度下为24%～48%(HN)和21%～48%(LN), 在正常CO₂浓度下为20%～36% (HN)和19%～32%(LN). 不同CO₂浓度下土壤排放CO₂的δ¹³C值和根际呼吸对氮肥增加的响应不同, CO₂浓度与氮肥用量在拔节期对根际呼吸的交互效应显著.

Contribution of wheat rhizosphere respiration to soil respiration under elevated atmospheric CO2 and nitrogen application.

With the support of free-air carbon dioxide enrichment (FACE) system and by using isotope ¹³C technique, and through planting wheat (Triticum aestivum L., C₃ crop) on a soil having been planted with maize (Zea mays L., C₄ crop) for many years, this paper studied the effects of elevated atmospheric CO₂ and nitrogen application on the δ¹³C value of soil emitted CO₂ and the wheat rhizosphere respiration. With the growth of wheat, the δ¹³C value of soil emitted CO₂ had a gradual decrease. Elevated atmospheric CO₂ concentration (200 μmol·mol^-1) decreased the δ¹³C value of emitted CO₂ at booting and heading stages significantly when the nitrogen application rate was 250 kg·hm^-2 (HN), and at jointing and booting stages significantly when the nitrogen application rate was 150 kg·hm^-2 (LN). Nevertheless, the elevated atmospheric CO₂ promoted the proportions of wheat rhizosphere respiration to soil respiration at booting and heading stages significantly. From jointing stage to maturing stage, the proportions of wheat rhizosphere respiration to soil respiration were 24%-48% (HN) and 21%-48% (LN) under elevated atmospheric CO₂, and 20%-36% (HN) and 19%-32% (LN) under ambient atmospheric CO₂. Under both elevated and ambient atmospheric CO₂ concentrations, the δ¹³C value of emitted CO₂ and the rhizosphere respiration had different responses to the increased nitrogen application rate, and there was a significant interactive effect of atmospheric CO₂ concentration and nitrogen application rate on the wheat rhizosphere respiration at jointing stage.