黄土高原退耕方式与年限对土壤呼吸及其温度敏感性的影响

Soil Respiration and Temperature Sensitivity of Apple Orchards and Abandoned Lands with Different Years After Returning Farmland to Forest on the Loess Plateau

土壤呼吸是陆地生态系统碳循环的关键过程,明确退耕后土地利用变化对土壤呼吸及其温度敏感性的影响是提升土壤碳汇能力的重要前提。以黄土高原20 a耕地、退耕3、6、10 a的苹果园与撂荒地为研究对象,原位监测样地2018年7-12月的土壤呼吸速率,估算其温度敏感性,并应用偏最小二乘结构方程模型,明确土壤呼吸及其温度敏感性的关键影响因子。结果表明,随退耕年限的增加,撂荒地土壤有机碳和全氮含量呈现先降低后升高的趋势,苹果园则与之相反。监测期间撂荒地平均土壤呼吸速率为2.73~4.65μmol·m^(-2)·s^(-1),苹果园为1.07~3.13μmol·m^(-2)·s^(-1),退耕3 a和6 a撂荒地的土壤呼吸速率显著高于苹果园(P<0.05)。土壤呼吸温度敏感性的变化范围为1.477~4.055,不同退耕方式间土壤呼吸温度敏感性并无显著差异。偏最小二乘-结构方程模型结果表明,土壤因子共解释了土壤呼吸及其温度敏感性34.4%的变化;相比于化学和生物因子,土壤水分与温度等物理因子对土壤呼吸及其温度敏感性的影响更为显著。研究表明,退耕后短期内(0~6 a),苹果园的固碳潜力更大,但随着退耕年限的延长(>6 a),撂荒地更有利于土壤固碳。

Soil respiration is a key process in the carbon cycle of terrestrial ecosystems.It is an important prerequisite for improving soil carbon sink capacity to clarify the effects of land conversion patterns and years on soil respiration,and its temperature sensitivity.In this study,the soil respiration rates of 20-year cultivated land,3-,6-and 10-year apple orchards and grassland in Loess Plateau was monitored in situ from July to December 2018,and the temperature sensitivity of different soils was estimated.The partial least square-structural equation model(PLS-SEM)was used to analyze the key factors affecting soil respiration and its temperature sensitivity.The results showed that the contents of soil organic carbon and total nitrogen decreased first and then increased with the increase of the years of returning farmland to forest/grassland,while the apple forest was in opposite.During the monitoring period,the average soil respiration rate of grassland was 2.73-4.65μmol·m^(-2)·s^(-1),and that of apple orchard was 1.07-3.13μmol·m^(-2)·s^(-1).The soil respiration rate of grassland was significantly higher than that of apple orchard after 3 and 6 years of restoration(P<0.05).The temperature sensitivity of soil respiration ranged from 1.477-4.055,and there was no significant difference in soil respiration temperature sensitivity among different conversion patterns.The results of applying PLS-SEM showed that soil factors explained 34.4%of the variation of soil respiration and its temperature sensitivity.Compared with chemical and biological factors,physical factors such as soil moisture and temperature had more significant effects on soil respiration and its temperature sensitivity.Studies have shown that in the short term(0-6 years)after returning farmland to forest/grassland,the carbon sequestration potential of apple forest is greater,but when the years of returning farmland are longer(6 years later),grassland is more conducive to soil carbon sequestration.