针阔树种人工林地表凋落物对土壤呼吸的贡献

摘要

Aboveground litter is of great importance in the study of carbon cycle in terrestrial ecosystem. However, current understandings of the contribution of aboveground litter to soil respiration are far too limited. In order to investigate the degree of contribution of aboveground litter to soil respiration, three treatments of non-litter (NL), cover litter (CL) and the control (C, natural litter cover) were set up in ten-year old Pinus tabulaeform and Populus plantations in Beijing-Tianjin sandstorm source area. Each treatment was replicated three times in galvanized sheet irons of size of 40 cm × 40 cm × 9 cm, 4 cm of which was above ground surface. Polyvinyl chloride (PVC) collars (with 10 cm inside diameter) were installed in each plot for soil respiration measurements. The field experiments were conducted from March 2013 to November 2013 and measurements taken only on days without precipitation and/or high winds to minimize equipment damage and measurement error. Soil respiration rates (Rs) were measured approximately once a month during the period of the experiment using Li-6400 portable CO2 infrared gas analyzer (IRGA) equipped with Li-6400-09 chamber (Li-COR IC., LiColn, NE, USA). Rs was continuously measured in three cycles at each collar and the three measurements averaged for the collar mean. Soil temperature was monitored simultaneously along soil respiration using a thermocouple penetration probe inserted in the soil to the depth of 5 cm in the vicinity of the respiration chamber. Soil moisture in the top soil layer (0-5 cm) was monitored using the oven-dry method. Results showed that soil respiration was significantly different among different treatments (P < 0.05). The mean soil respiration rates (Rs, μmol·m-2·s-1) under P. tabulaeform and Populus plantations in the NL, CL, C treatments were respectively 2.28, 2.81, 2.55, and 2.13, 2.62, 2.32., indicating that CL>C>NL. Soil respiration was positively correlated with soil temperature at 5 cm soil depth (R2=0.54 to 0.88, P<0.05), but not with soil moisture at 5 cm soil depth. The order of sensitivity to temperature of soil respiration (Q10) was NL< CL< C. The contribution rates of aboveground litter to soil respiration under P. tabulaeform and Populus plantations were 20.78% and 20.75%, respectively, suggesting little difference in litter contribution to soil respiration between P. tabulaeform and Populus. The results of the study could have significant implications for future study on soil respiration and the estimation of carbon sequestration of young coniferous and deciduous plantations in the Beijing-Tianjin sandstorm source area.%了解地表凋落物呼吸对陆地生态系统碳循环研究具有重要意义。为了研究针阔树种地表凋落物对土壤呼吸的贡献,本文在京津风沙源地区选择林龄为10年的油松、杨树人工林,设置去除凋落物(no litter, NL)、覆盖凋落物(cover litter, CL)和自然状态(control, C)3种处理,利用Li-6400-09土壤呼吸测定系统对土壤呼吸速率以及地表5 cm 土壤温度、土壤湿度进行观测。结果表明：1)凋落物的去除与覆盖显著改变土壤呼吸速率(P<0.05),油松、杨树人工林3种处理土壤呼吸速率年均值(μmol⋅m-2⋅s-1)分别为2.28、2.81、2.55和2.13、2.62、2.32,均为CL>C>NL(P<0.05)；2)土壤呼吸对环境因子的响应产生地表凋落物贡献的季节性差异,土壤呼吸速率与地表5 cm土壤温度呈显著指数正相关关系(R2=0.54~0.88, P<0.05),但与地表5 cm土壤湿度不存在相关关系,油松和杨树CL、NL、C 3种处理土壤呼吸的温度敏感性指数Q10值分别为1.97、1.90、2.25和2.79、2.61、2.93,大小趋势均为 NL