添加硫和锰对长白山森林土壤与腐殖质顽固性有机碳矿化的影响

Effects of Sulfur and Manganese Addition on Mineralization of Recalcitrant Organic Carbon of Forest Soil and Humus in Changbai Mountains

【目的】探究硫和锰添加对长白山森林土壤和腐殖质顽固性有机碳的矿化速率及其温度敏感性(Q10)的影响,为评估长白山森林碳元素的生物地球化学循环对大气硫输入的响应提供科学依据。【方法】采集长白山阔叶红松林、杨桦林和高山苔原土壤以及阔叶红松林和杨桦林腐殖质样品,进行室内培养试验。首先将样品置于25℃预培养90天,以移除易分解的活性碳组分,之后分别加入2 mL MnCl2、NaCl、MnSO4和Na2SO4溶液(Mn添加量为3 mg·g^-1有机碳),对照处理加入等体积的双蒸水,分别置于25和35℃下培养30天,于第1、3、6、10、15、21和30天测定释放的CO2量,并计算顽固性有机碳矿化速率、累积矿化量和有机碳矿化的温度敏感性(Q10)。在培养结束时(第30天),采用磷脂脂肪酸生物标记(PLFA)法测定土壤和腐殖质样品的磷脂脂肪酸总量。【结果】在MnCl2和NaCl处理间及在MnSO4和Na2SO4处理间,土壤和腐殖质的顽固性有机碳矿化速率、累积矿化量和Q10无显著差异(P>0.05);腐殖质的顽固性有机碳矿化速率在4种处理之间无显著差异;土壤顽固性有机碳矿化速率在MnSO4处理下得到提高(P<0.05),而MnCl2处理对其无显著影响;添加可MnSO4和Na2SO4显著提高3种土壤和杨桦林腐殖质顽固性有机碳累积矿化量(P<0.05),而添加MnCl2和NaCl处理则无显著影响,表明供试土壤和腐殖质有机碳矿化受到硫添加的影响,而不是锰添加;添加硫和锰可显著降低阔叶红松林土壤顽固性有机碳矿化速率Q10(P<0.05),而对杨桦林和高山苔原土壤无显著影响;阔叶红松林和杨桦林腐殖质的微生物总量在MnSO4处理下显著提高(P<0.05),而MnCl2处理对其无显著影响;MnSO4添加可提高土壤的微生物总量,特别是高山苔原土壤显著高于对照(P<0.05)。【结论】硫添加可显著提高长白山森林土壤的顽固性有机碳矿化速率和累积矿化量,而锰添加则无显著影响。考虑到硫对土壤有机碳矿化的重要性,今后建立土壤有机碳矿化模型时应将硫输入作为一个重要参数。

【Objective】The objective of the study was to investigate the effects of sulfur(S)and manganese(Mn)addition on the mineralization of recalcitrant organiccarbon(C)and temperature sensitivity(Q10)from forest soil and mor-humus collected from Changbai Mountains,northeastern China,in order to provide a basis for predicting the responses of biogeochemical cycling of carbon to atmospheric sulfur deposition.【Method】Soil and mor-humus samples were collected from montane forests(broadleaved Korean pine and Betulaplatyphylla-Populusdavidiana mixed forest)and tundra,and then pre-incubated at 25℃for 90-days toremovethe componentsof active carbonthat can be easily decomposed,followed by addition of 2 mL solutionsrespectivelyof MnCl2,MnSO4,NaCl,and Na2SO4,and addition of equivalent volumeofdouble distilled water to the control treatment,and further incubated at 25℃and 35℃for a 30-day period,respectively.Respired CO2 was periodically measured at day 1,3,6,10,15,21 and 30 during the 30 day’s period,cumulative mineralization of recalcitrant organic carbon,recalcitrant organic carbon mineralization rate and associated Q10 were calculated.Soil and mor-humus collected at the end of incubation experiment were used for measuring soil microbial biomass using phospholipid fatty acid(PLFA)method.【Result】The recalcitrant organic carbon mineralization rate,cumulative mineralization of recalcitrant organic carbon and Q10 were not significantly different between MnCl2 and NaCl treatments,and betweenMnSO4 and Na2SO4 treatments(P>0.05).The addition of S rather than Mn affected the recalcitrant organic carbon mineralization rate.Mineralization rate of soil recalcitrant organic carbon under the MnSO4 treatment were significantly higher than those of the Na2SO4 treatment(P<0.05).MnSO4 and Na2SO4 addition significantly increased the cumulative mineralization of recalcitrant organic carbon of the mor-humus samples from Betula platyphylla-Populus davidiana mixed forest and the three soil samples(P<0.05),whereas the MnCl2 and NaCl addition did not.The addition of Mn and S significantly decreased Q10 of soils collected from broadleaved Korean pine forest(P<0.05),but not those of soils from B.platyphylla-P.davidiana mixed forest and tundra.The addition of MnSO4 significantly increased total PLFAs of the mor-humus collected from broadleaved Korean pine and B.platyphylla-P.davidiana mixed forest and total PLFAs increased after the addition of MnSO4 solution,especially for the tundra soil.【Conclusion】Our results highlighted an effect of S rather than Mn on the mineralization of soil recalcitrant organic carbon in Changbai Mountains.Hence,we suggest that more careful studies of the influence of sulfur on organic carbon mineralization are required to determine biogeochemical cycling of carbon from the ecosystem where atmospheric sulfur deposition is still not declining.