秸秆覆盖条件下小麦生长季根系呼吸对土壤呼吸作用的贡献

在紫色土丘陵区连续6年进行秸秆覆盖试验的"旱三熟"农田系统中,于2012年12月—2013年4月小麦生长季内对土壤呼吸进行测定,并对小麦根系生物量、土壤温度、土壤水分和土壤有机碳含量等指标进行监测,以分析土壤呼吸动态变化的影响因素.结果表明,秸秆覆盖措施显著提高了土壤呼吸速率,秸秆覆盖(S)和秸秆覆盖+腐熟剂(SD)处理分别比对照(CK)增加了45.0%和29.4%.曲线估计表明,土壤呼吸作用与根系生物量呈显著线性关系,通过建立二者的线性回归方程,采用生物量外推法估算小麦根系呼吸作用占土壤呼吸作用的比例,在分蘖期(2012年12月)、拔节期(2013年1月)、抽穗期(2012年3月)和灌浆期(2013年4月),根系呼吸分别占土壤呼吸的28.2%、44.0%、56.9%、56.2%,平均贡献为46.3%,并呈先增加再降低的趋势,在抽穗期达到最大,与根系生物量的变化同步.按照不同处理建立根系生物量与土壤呼吸间的线性回归方程,经计算得出CK、S和SD 3个处理中,根系呼吸作用占土壤呼吸作用的比例分别为42.9%、43.8%和43.7%,秸秆覆盖对根系呼吸作用比例无显著影响.

Contribution of root respiration to soil respiration based on straw mulching in wheat growing season

In a dryland with triple intercropping system and 6-year straw mulching experiment in purple hilly region of southwest China, the soil respiration was measured, and the biomass of wheat root, soil temperature, soil moisture and soil organic carbon content were monitored during the growing season of wheat (December 2012 to April 2013), so as to analyze the factors influencing soil respiration dynamics. The results showed that straw mulching could significantly improve the rate of soil respiration. Compared to the control (CK), the treatments of straw mulching (S) and straw mulching+decomposing inoculant (SD) increased soil respiration by 45.0% and 29.4%, respectively. Curve estimation revealed that there was significant linear relationship between soil respiration and root biomass. The equation of liner regression was constructed between soil respiration and root biomass, and the contribution of root respiration to soil respiration was estimated by the method of Root Biomass Extrapolation. At the tillering(Dec 2012), shooting (Jan. 2013), heading (Mar. 2013) and filling (Apr. 2013) stages of wheat, the root respiration accounted for 28.2%, 44.0%, 56.9% and 56.2%, respectively, of soil respiration, and the average contribution was 46.3%. The trend of proportion of root respiration was increasing firstly, peaking at the heading stage of wheat and then decreasing, which was synchronous with the change of root. The linear regression between root biomass and soil respiration was established for different treatments, which showed that the contribution rate of wheat root to soil respiration in CK, S and SD was 42.9%, 43.8% and 43.7%, respectively. Straw mulching had no significant effect on the proportion of root respiration.