模拟增温对羊草生态系统土壤呼吸速率的影响

Abstract

草地是陆地生态系统的重要组成部分，研究草地系统土壤呼吸速率对全球气候变暖的响应，对预测全球碳循环具有重要作用。采用高度分别为0.5 m（T1）和1.85 m（T2）的开顶式增温箱（OTCs）对羊草生态系统进行模拟增温，仔细观察羊草的生育期，在每个生育期的同一天的晨间t₁时段（9：00-11：00）、午间t₂时段（13：30-15：30）和晚间t₃时段（17：00-19：00）监测土壤呼吸速率。分析不同增温幅度下土壤呼吸速率的变化规律，明确影响土壤碳排放的主要因素，探讨土壤呼吸速率与影响因素间存在的关系。结果显示：1）相对于空白对照C，模拟增温T1和T2导致0-10 cm土壤温度分别显著提高1.18和2.37℃；导致0-10 cm土壤湿度降低2.27%和4.57%；2）在羊草生长阶段，土壤呼吸速率呈现明显的季节性变化特征，同一天的t₁时段、t₂时段和t₃时段土壤呼吸速率峰值分别出现在结实期、抽穗期和开花期。非生长阶段土壤呼吸速率无显著差异；3）不同处理下土壤呼吸速率与近地表气温、0-10 cm土壤温度和地下生物量呈指数正相关关系，与0-10 cm的土壤湿度呈显著二次项负相关关系，与地上生物量表现为二次项正相关关系。研究结果明确了羊草生态系统中土壤碳排放对增温的响应，可为草原生态系统应对气候变化及可持续发展提供理论依据。;Grasslands are one of the major types of terrestrial ecosystems and their soil respiration makes up one of the largest flux of carbon between their ecosystems and the atmosphere. Therefore, revelation of the responses of their soil respiration to global warming can be vital and will shed light on identifying and predicting the global carbon cycle. To simulate climate change, we used two open-top chambers (OTCs) T1 (0.5 m) and T2 (1.85 m) to manipulate warming Leymus chinensis systems and meanwhile observed the growth of Leymus chinensis. The soil respiration of these systems in both OTCs was monitored and the soil respiration rate was measured at the time t₁ (9:00-11:00), t₂ (13:30-15:30), and t₃ (17:00-19:00). The change in the soil respiration of heated Leymus chinensis systems was investigated to identify the main factors contributing to release of soil carbon to atmosphere and put insight into the relationship between the soil respiration and these main factors. The observations showed that T1 and T2 increased annual surface soil temperature by 2.14 and 4.03℃ respectively compared to control, but decreased annual soil moisture by 2.27% and 4.57% in the soil depth range between 0 cm and 10 cm. The results demonstrated that the manipulated heating significantly (p < 0.05) enhanced soil respiration through growth stages and soil respiration patterns changed over seasons. In grain filling, heading, and blossom stage, peak values of soil respiration rate were observed at t₁, t₂ and t₃ in the Leymus chinensis of the same growth day. The soil respiration rate did not change significantly at non-growth stages. The study also found that the soil respiration rate under different treatments had a positive exponential correlation to near-surface air temperature, surface soil temperature, and below-ground biomass. It also had a negative quadratic correlation with surface soil moisture and a positive quadratic correlation with above-ground biomass. This study reveals the change in release of soil carbon from Leymus chinensis systems to atmosphere when they were treated with manipulated warming, which can provide useful information for understanding how grassland ecosystems respond to climate change and sustainable development of animal husbandry.