葡萄糖添加对不同演替阶段森林土壤微生物及酶化学计量特征的影响

糖类作为一种重要的根系分泌物,如何影响土壤微生物及酶化学计量特征目前尚不清楚,制约着人们对上述过程的认识。为探究糖类对森林生态系统中土壤微生态环境和酶活性的影响,以黄土高原子午岭地区森林演替先锋(山杨林)、中期(油松林)和气候顶级群落(辽东栎林)为研究对象,通过野外土壤采样、添加3种不同浓度的葡萄糖(0.1,0.5,1 g/kg干土),和室内培养的方法,研究了葡萄糖添加对土壤微生物量和酶活性及化学计量的影响。结果表明:(1)随着森林演替,土壤中速效磷(SAP)、硝态氮(NO^-₃-N)等速效养分显著降低。在葡萄糖影响下,3种林地土壤全氮(TN)降低,山杨林土壤C/N值显著大于油松林和辽东栎林。(2)随着森林演替,山杨林和辽东栎林微生物碳(MBC)和微生物氮(MBN)的值显著大于油松林,均为先减小后增加。随葡萄糖浓度增加,3种林地MBC和MBN均增加,微生物(MBP)呈波动趋势。(3)山杨林和辽东栎林土壤酶活性均显著大于油松林。随葡萄糖浓度增加,油松林和辽东栎林4种酶活性均为先增加后减小。BG/(LAP+NAG)、BG/AP和(LAP+NAG)/AP辽东栎林的值最大,山杨林和辽东栎林的值显著大于油松林。(4)RDA分析表明,土壤酶、微生物量及其酶活性分别与有机质(SOC),MBC有着显著性正相关关系,土壤酶活性(除NAG)与pH值均呈显著负相关。本研究说明碳输入增加了3种林分土壤的激发效应,土壤微生物量增加,降低了土壤TN含量,改变了土壤养分化学计量,进而加剧了油松林地微生物N限制和辽东栎林地微生物P限制,影响根际土壤有机质分解和养分代谢等过程,从而影响了森林演替过程。

Effects of Glucose Addition on Stoichiometric Characteristics of Microorganisms and Enzymes in Forest Soils at Different Succession Stages

As an important root exudate,how sugars affect the stoichiometric characteristics of soil microorganisms and enzymes is not clear,which restricts understanding of the above process.In order to explore the effects of sugars on soil microecological environment and enzyme activity in forest ecosystem,the pioneer(poplar forest),middle stage(Pinus tabulaeformis forest)and climatic top community(Liaodong oak forest)of forest in Ziwuling area of Loess Plateau were selected as the sampling sites.The effects of glucose addition on soil microbial biomass,enzyme activity and stoichiometry were studied by adding three different concentrations of glucose(0,0.1,0.5,1 g/kg dry soil)to soils sampled in the forests and indoor culture methods.The results showed that:(1)with forest succession,soil available nutrients such as available phosphorus(AP)and nitrate nitrogen(NO-3-N)decreased significantly;under the influence of glucose,the soil TN of three kinds of woodland decreased,and the soil C/N value of poplar forest was significantly higher than that of Pinus tabulaeformis forest and Liaodong oak forest;(2)with forest succession,the values of microbial carbon(MBC)and microbial nitrogen(MBN)in Populus davidiana forest and Liaodong oak forest were significantly higher than those in Pinus tabulaeformis forest,which decreased at first and then increased;with the increase of glucose concentration,MBC and MBN in three kinds of woodland increased,and MBP showed a fluctuating trend;(3)the soil enzyme activities of Populus davidiana forest and Liaodong oak forest were significantly higher than those of Pinus tabulaeformis forest;with the increase of glucose concentration,the activities of four enzymes in Pinus tabulaeformis forest and Liaodong oak forest increased at first and then decreased;the values of BG/(LAP+NAG),BG/AP and(LAP+NAG)/AP of Liaodong oak forest were the highest,and these values of Populus davidiana forest and Liaodong oak forest were significantly higher than those of Pinus tabulaeformis forest;(4)RDA analysis showed that there was a significant positive correlation between soil enzyme,microbial biomass and enzyme activity and SOC,MBC,respectively,and a significant negative correlation between soil enzyme activity(except NAG)and pH.This study showed that carbon input increased the stimulating effect of three kinds of forest soil,increased soil microbial biomass,decreased soil TN content,changed soil nutrient stoichiometry,and then intensified microbial N limitation in Pinus tabulaeformis woodland and Liaodong microbial P limitation in oak woodland,affected the decomposition of organic matter and nutrient metabolism in rhizosphere soil,thus affected the process of forest succession.