黄土丘陵区柠条人工林不同深度土壤呼吸速率对土壤温湿度的响应

Response of Soil Respiration Rates to Soil Temperature and Moisture at Different Soil Depths of Caragana korshinskii Plantation in the Loess-Hilly Region

明确气候变化背景下生态脆弱区土壤呼吸速率特征和土壤温湿度对其影响,对准确评估和预知该区碳收支具有重要意义.以陕北黄土丘陵区自然撂荒地22 a柠条人工纯林为研究对象,通过CO_(2)分析仪和温湿度传感器测定不同土层(10、50和100 cm)CO_(2)浓度平均值和土壤温湿度,采用Fick第一扩散系数法计算土壤呼吸速率,探究不同土层土壤温度、土壤湿度和土壤呼吸速率的动态变化特征,并进一步分析不同土层土壤呼吸速率对土壤温湿度的响应.结果表明,土壤呼吸速率日变化随土层深度增加显著降低(P<0.05),峰值出现时间存在滞后现象,相邻土层间(10、50和100 cm)土壤呼吸速率由上至下均滞后1 h;6~9月土壤呼吸速率月变化为多峰曲线,其中10、50和100 cm土层土壤呼吸速率最大值分别在7月25日、8月6日和8月10日,达13.96、2.96和1.47μmol·(m^(2)·s)^(-1);土壤温度对土壤呼吸速率影响随土层深度增加而减弱,50 cm及以下土层土壤温度对土壤呼吸速率无显著影响(P>0.05),10 cm土层指数拟合最优,R^(2)=0.96,50 cm和100 cm土层拟合较差,R^(2)分别为0.00和0.01,温度敏感系数Q_(10)随土层深度增加而减小;不同土层土壤湿度对土壤呼吸速率影响均显著(P<0.05),二次拟合表现为50 cm(R^(2)=0.35)>10 cm(R^(2)=0.22)>100 cm(R^(2)=0.31);10、50和100 cm土层土壤温度与土壤湿度的综合作用可解释土壤呼吸速率的96%、6%~50%和22%~24%.综上所述,黄土丘陵区柠条人工纯林不同深度土壤温湿度对土壤呼吸速率影响存在差异,10 cm土层土壤呼吸速率受土壤温湿度的综合影响,但土壤温度的相对贡献更高,50 cm土层及以下土壤湿度为关键因子.研究结果有助于更好地预测未来气候变化对该区陆地生态系统碳循环影响,为温室气体调控提供理论依据.

It is of great significance to clarify the influence of soil temperature and moisture on soil respiration rate and its characteristics in ecologically fragile regions under the background of climate change for the accurate assessment and prediction of carbon budgets in this region.The average CO_(2)concentration and soil temperature and moisture at different soil depths(10,50,and 100 cm)were measured using a CO_(2)analyzer and temperature and moisture sensors.The soil respiration rate was calculated using Fick’s first diffusion coefficient method.The dynamic characteristics of soil temperature,soil moisture,and soil respiration rate in different soil depths were explored,and the response of soil respiration rate to soil temperature and moisture were further analyzed.The results showed that the diurnal variation in soil respiration rate decreased significantly with the increase in soil depth(P<0.05),and the peak time lagged behind.Soil respiration rate in adjacent soil depths(10,50,and 100 cm)lagged 1 h from top to bottom.The monthly variation in soil respiration rate was a multi-peak curve,in which the maximum soil respiration rates of 10,50,and 100 cm soil depths were on July 25^(th),August 6^(th),and August 10^(th),reaching 13.96,2.96,and 1.47μmol·(m^(2)·s)^(-1),respectively.The effect of soil temperature on soil respiration rate decreased with the increase in soil depth.Soil temperature at 50 cm and below had no significant effect on soil respiration rate(P>0.05).The fitting index of 10 cm soil depth was the best(R^(2)=0.96),but the fitting indexes of 50 cm and 100 cm soil depths were poor(R^(2)=0.00 and R^(2)=0.01,respectively).The temperature sensitivity coefficient Q_(10) decreased with the increase in soil depth.Soil moisture in different soil depths had significant effects on soil respiration rate(P<0.05),and the quadratic fitting indicated that 50 cm(R^(2)=0.35)>10 cm(R^(2)=0.22)>100 cm(R^(2)=0.31).The combined effects of soil temperature and moisture in different soil depths could explain 96%,6%-50%,and 22%-24%of soil respiration rate,respectively.In summary,the effects of soil temperature and moisture at different soil depths of the Caragana korshinskii plantation in the loess-hilly region on soil respiration rate differed.The soil respiration rate of the 10 cm soil depth was affected by the comprehensive effect of soil temperature and moisture;however,the relative contribution of soil temperature was higher,and soil moisture at and below a soil depth of 50 cm was the key factor.These results could help improve predictions on the impact of future climate change on the carbon cycle of terrestrial ecosystems in the region and provide a theoretical basis for greenhouse gas regulation in the future.