秦岭不同海拔森林土壤-植物-凋落物化学计量特征对土壤氮组分的影响

为探究不同海拔森林土壤氮组分对土壤-植物-凋落物化学计量特征的响应规律,选取太白山1300~2600 m海拔范围内4种典型森林--锐齿栎林(Quercus aliena var.acuteserrata)、辽东栎林(Quercus liaotungensis)、红桦林(Betula albo-sinensis)、牛皮桦林(Betula albo-sinensis var.septen-trionalis)为研究对象,测定土壤、叶片、凋落物、根的碳(C)、氮(N)、磷(P)及土壤铵态氮、硝态氮、微生物生物量氮,分析不同森林土壤、植物、凋落物的化学计量比值的变化特征及其对氮组分的影响。结果表明:1)4种森林土壤C、N、P含量的变化范围分别为36.77~59.80、2.91~4.76、0.13~0.80 g·kg^-1。C、N含量在不同森林间变化趋势基本一致,均表现为牛皮桦林>红桦林>辽东栎林>锐齿栎林;P含量的变化趋势表现为辽东栎林>牛皮桦林>红桦林>锐齿栎林;2)锐齿栎林叶片N∶P<14,表明锐齿栎林生长较大程度受N限制;辽东栎林、红桦林、牛皮桦林叶片N∶P>16,表明辽东栎林、红桦林、牛皮桦林生长较大程度受P限制;3)不同森林间微生物量氮差异显著(P<0.05),铵态氮含量无显著差异,硝态氮含量表现为锐齿栎林(0.33 mg·kg^-1)>牛皮桦林(0.28 mg·kg^-1)>辽东栎林(0.27 mg·kg^-1)>红桦林(0.17 mg·kg^-1);4)冗余分析结果表明,土壤-植物-凋落物N∶P值是影响土壤微生物量氮的重要因子,土壤C∶N是影响铵态氮、硝态氮含量的重要因子。本研究结果为太白山森林生态系统的保护和氮循环研究奠定基础。

Effects of stoichiometric characteristics of soil plant litter on soil nitrogen components in different forests along an elevational gradient of Qinling Mountains.

We examined the response of soil N components in forests along an elevational gradient to the stoichiometric characteristics of soil-plant-litter with four typical forests Quercus aliena var.acuteserrata(QVA),Quercus liaotungensis(QW),Betula albo-sinensis(BA),Betula albosinensis var.septen-trionalis(BAV)in the range of 1300-2600 m elevation in Taibai Mountain.We measured the contents of organic C,total N,total P in soil,leaves,litter and roots,and soil ammonium-N,nitrate-N and microbial biomass N.We analyzed the stoichiometric characteristics of soil,plants,and litter in different forests and their effects on soil N components.The results showed that:(1)The variation ranges of soil C,N and P in the four forests were 36.77-59.80,2.91-4.76 and 0.13-0.80 g·kg^-1,respectively.The changes of soil C and N contents in different forests followed the same trend:BAV>BA>QW>QVA;the trend of change for soil P showedQW>BAV>BA>QVA.(2)The foliar N∶P ratio of QVA was lower than 14,indicating that plant growth in QVA was limited by N availability.Foliar N∶P ratio of QW,BA and BAV was above16,indicating that plant growth in QW,BA and BAV were all limited by P.(3)Microbial biomass N varied significantly among different forests(P<0.05).There was no significant difference in ammonium-N content.The nitrate-N content showed QVA(0.33 mg·kg^-1)>BAV(0.28 mg·kg^-1)>QW(0.27 mg·kg^-1)>BA(0.17 mg·kg^-1).(4)The results of redundancy analysis showed that the N∶P ratio of soil-plant-litter was an important factor affecting microbial biomass N.Soil C∶N ratio was an important factor affecting ammonium N and nitrate N contents.Our results provide a basis for the rational management of major tree species and the study of nitrogen cycling in forest ecosystems of Taibai Mountain.