红壤侵蚀区马尾松林恢复过程中土壤异养呼吸及微生物多样性的变化特征

Changes in Soil Heterotrophic Respiration and Its Microbial Diversity during Restoration of Pinus massoniana Plantations in Eroded Red Soil Area

土壤异养呼吸是影响土壤有机碳积累的关键因素。以南方红壤水土流失区不同恢复年限的马尾松林(未治理地(Y0)、恢复14 a(Y14)、恢复31 a(Y31))为对象,对不同呼吸组分进行测定并结合温度、水分以及微生物等因子,研究马尾松林恢复对土壤异养呼吸的影响。结果表明:不同恢复年限马尾松林土壤异养呼吸差异显著,恢复31 a显著大于恢复14 a以及未治理地,未治理地异养呼吸速率仅为0.99μmol·m^(–2)·s^(–1),而治理14 a、31 a分别为2.20、2.80μmol·m^(–2)·s^(–1);温度是异养呼吸季节变化的主要影响因子,分别解释季节变化的40.6%(Y0)、62.2%(Y14)、66.6%(Y31);马尾松林恢复后土壤异养呼吸温度敏感性(Q10)显著增加,Y0、Y14、Y31的Q10分别为1.58、1.93和1.82;不同恢复年限土壤异养呼吸占土壤总呼吸比例为77.94%(Y0)、70.84%(Y14)、77.35%(Y31)。结构方程表明,在马尾松林恢复过程中,土壤有机碳(SOC)、温度以及土壤微生物多样性变化是影响土壤异养呼吸变化的主要因子,其中SOC、土壤微生物与异养呼吸显著正相关,而植被恢复过程中土壤温度变化与异养呼吸显著负相关。本研究结果表明,马尾松林植被恢复过程中SOC的积累以及缺乏有效的物理保护增加了微生物对SOC的分解,另一方面土壤环境温度的降低和细菌、真菌丰度的增加以及群落中变形菌、子囊菌、酸杆菌的增加,更进一步加剧微生物对原有土壤有机质的分解强度,导致异养呼吸碳排放的持续增加,最终限制了马尾松林土壤碳吸存效率。因此,较高的土壤异养呼吸可能是影响红壤侵蚀退化区土壤有机质进一步提升的关键。

【Objective】The accumulation rate of soil organic matter directly restricts the improvement of productivity of Pinus massoniana(Masson pine)in the process of vegetation restoration in eroded red soil area.The way to solve this problem has been an inevitable development process of Masson pine in eroded red soil area.Heterotrophic respiration,an important part of soil carbon emission,is a key factor affecting soil organic carbon accumulation.Therefore,it is of great significance to study the effects of Masson pine plantation restoration on heterotrophic respiration and its temperature sensitivity in eroded red soil areas.This will enhance our understanding of the carbon output process and effectively increase soil organic matter accumulation in eroded red soil areas.【Method】In this study,Masson pine plantations with different restoration years(Y0,Y14,Y31)were selected as the research objects.The effects of vegetation restoration on soil heterotrophic respiration were studied by separating and measuring different respiration components and combining with soil factors such as soil organic carbon,total nitrogen,soil temperature,water content and litter.The structural equation model of heterotrophic respiration between litter,soil temperature,soil nutrients,soil microorganisms and heterotrophic respiration were established to analyze the correlation between heterotrophic respiration and environmental factors in the process of vegetation restoration,and to explore the main factors affecting heterotrophic respiration.【Result】The results showed that the heterotrophic respiration(RH)of the pine forests with different recovery years differed significantly.The RH in site Y31 was significantly higher than that in site Y14 and Y0.The RH in site Y0 was only 0.99μmol·m^(–2)·s^(–1),while in sites Y14 and Y31 it was 2.20 and 2.80μmol·m^(–2)·s^(–1),respectively.Temperature was the main influencing factor of the seasonal variation of heterotrophic respiration,explaining 40.6%(Y0),62.2%(Y14)and 66.6%(Y31)of the seasonal variation,respectively.During the restoration process,the temperature sensitivity(Q10)of relative humidity increased significantly,which was 1.58,1.93 and 1.82,respectively.The relative contributions of RH to total soil respiration in different recovery years are 77.94%(Y0),70.84%(Y14),and 77.35%(Y31).The structural equation model showed that soil organic carbon(SOC),temperature and soil microbial diversity were the main factors affecting soil RH during the restoration of Masson pine.SOC and soil microbial abundance significantly correlated with RH,and soil temperature varied with vegetation restoration which significantly and negatively correlated with RH.【Conclusion】The results of this study indicate that the accumulation of SOC and lack of effective physical protection during Masson pine vegetation restoration increase the decomposition of SOC by microorganisms;On the other hand,the reduction of soil environmental temperature,a continuous increase of bacteria and fungi abundance,and an increase of Proteobacteria,Ascomycota and Acidobacteria in the community further aggravate the microbes to the original strength of soil organic matter decomposition.Consequently,the continuous increase of heterotrophic respiration related carbon emissions limits the improvement of carbon sequestration efficiency of Masson pine forests.Therefore,the strong soil heterotrophic respiration in the eroded and degraded red soil area may be the key factor limiting further improvement of soil organic matter.