模拟氮沉降对滇中云南松林湿干季土壤特性和土壤呼吸的影响

Effects of Changes in Soil-Based Properties on Soil Respiration in Pinus yunnanensis in Central Yunnan under Nitrogen Deposition

【目的】研究氮沉降背景下湿干两季土壤理化性质、微生物特征和酶活性变化对土壤呼吸影响,为亚热带森林生态系统碳循环及物质循环、能量流动提供科学依据。【方法】选择滇中亚高山云南松林为研究对象,研究模拟氮沉降下(对照CK 0 g/(m^(2)·a)、低氮LN 10 g/(m^(2)·a)、中氮MN 20 g/(m^(2)·a)、高氮HN 25 g/(m^(2)·a))湿干两季土壤理化性质、酶活性、土壤微生物数量、微生物量碳(MBC)、微生物量氮(MBN)以及土壤呼吸变化特征,阐明氮沉降下土壤呼吸的季节变化特征以及土壤呼吸与土壤特性之间的响应关系,并探讨其耦合机制的相关性。【结果】(1)与CK相比,各氮处理下土壤TN、NH_(4)^(+)-N均显著增加。(2)在湿干季时,脲酶在HN显著增加了16.38%~67.95%;蔗糖酶在HN显著降低了19.65%~35.65%;过氧化氢酶在LN、MN和HN显著增加了11.11%~100.00%;多酚氧化酶在MN、HN显著降低了8.69%~25.00%;(3)土壤微生物数量、MBC在LN、MN下均显著增加(4.70%~30.52%),在HN显著降低(18.57%~57.20%);MBN在HN显著降低(6.80%~13.70%)。(4)在湿季时,各氮处理促进了土壤呼吸,干季时HN抑制了土壤呼吸;随着时间的推移,HN对土壤呼吸从促进作用转变为抑制作用。土壤呼吸与土壤温度、湿度均呈显著相关;LN、HN的Q10提高了7.41%,60.27%。(5)湿季时,土壤呼吸与TN、TP、TK、NH_(4)^(+)-N、NO_(3)^(-)-N、脲酶呈显著正相关,与蔗糖酶、多酚氧化酶、微生物数量、MBC、MBN呈显著负相关;干季时,土壤呼吸与NO_(3)^(-)-N、脲酶呈显著负相关,与过氧化氢酶、多酚氧化酶、微生物数量、MBC、MBN呈极显著正相关。【结论】随着时间推移,HN抑制了云南松林的土壤呼吸,且施氮并未改变土壤呼吸的季节变化规律与日变化规律。

【Objective】 The current study was conducted to study the effects of changes in soil physicochemical properties,microbial characteristics and enzyme activities on soil respiration in wet and dry seasons under the background of nitrogen deposition,and to provide scientific basis for carbon cycle and material cycle and energy flow in subtropical forest ecosystems.【Method】 The alpine Pinus yunnanensis in Central Yunnan were selected for the study.Soil physicochemical properties,enzyme activities,soil microbial population,microbial biomass carbon(MBC),microbial biomass nitrogen(MBN) and soil respiration under simulated N deposition(CK 0 g/(m^(2)·a),low N LN 10 g/(m^(2)·a),medium N MN 20 g/(m^(2)·a),high N HN 25 g/(m^(2)·a)) in wet and dry seasons were investigated in this study to elucidate the seasonal variation of soil respiration under N deposition and the response relationship between soil respiration and soil properties,and to explore the relevance of the coupling mechanism.【Result】(1) Soil TN and NH_(4)^(+)-N were significantly increased under all N treatments compared to CK.(2) During the wet-dry season,urease was significantly increased by 16.38%-67.95% in HN;sucrase was significantly decreased by 19.65%-35.65% in HN;catalase was significantly increased by 11.11%-100.00% in LN,MN,and HN;while polyphenol oxidase was significantly decreased in MN,HN by 8.69%-25.00%,compared to CK.(3)Compared to control,soil microbial population and MBC was significantly increased in LN,MN(4.70%-30.52%) but significantly decreased in HN(18.57%-57.20%);MBN was significantly decreased in HN(6.80%-13.70%).(4)N deposition promoted soil respiration in the wet season,however HN inhibited soil respiration in the dry season;across the tested period,HN changed from promoting to inhibiting effect on soil respiration.Soil respiration was significantly correlated with soil temperature and moisture;Q10 of LN,HN increased by 7.41%,60.27%,respectively.(5)In the wet season,soil respiration was significantly and positively correlated with TN,TP,TK,NH_(4)^(+)-N,NO_(3)^(-)-N,and urease,but was significantly and negatively correlated with sucrase,polyphenol oxidase,microbial population,MBC,and MBN;in the dry season,soil respiration was significantly and negatively correlated with NO_(3)^(-)-N and urease,but was significantly and negatively correlated with peroxidase,polyphenol oxidase,microbial population,MBC,and MBN.【Conclusion】 HN suppressed soil respiration in P.yunnanensis forests over time,and N application did not change the seasonal and daily patterns of soil respiration.