针阔混交林中兴安落叶松比例对土壤化学性质和酶化学计量比的影响

Effect of Larix gmelinii proportion on soil chemical properties and enzymatic stoichiometry in mixed coniferous and broad-leaved forest

【目的】研究不同比例兴安落叶松Larix gmelinii的针阔混交林土壤的化学性质和酶化学计量比。【方法】按照群落中兴安落叶松材积所占的不同比例(70%、75%、80%、85%、90%、95%),把调查的森林群落分为6种类型,分别监测了各类型群落0~5和5~20 cm土层的养分和生物化学性状等。【结果】分析的5种酶中酸性磷酸酶的活性最高,0~5与5~20 cm土层均值分别为463.74 nmol·g^-1·h^-1和312.91 nmol·g^-1·h^-1。在0~5 cm土层中,群落中兴安落叶松比例的增加对亮氨酸氨肽酶的活性有明显的促进作用,兴安落叶松比例为95%的群落亮氨酸氨肽酶活性比兴安落叶松比例为75%和85%的群落显著提高了57.44%和59.40%。群落中兴安落叶松的比例也影响了土壤中酶的化学计量特征,当兴安落叶松比例达95%时,5~20 cm土层与氮、磷矿化相关的酶计量比显著高于兴安落叶松比例为80%和85%的群落(P95%-80%=0.020, P95%-85%=0.020)。与碳、氮矿化相关的酶计量比在兴安落叶松为95%的群落中最低。土壤的酶活性与土壤养分质量分数间呈现复杂的相关性,并随着土壤深度的增加而改变。在0~5 cm土层,土壤pH与葡萄糖苷酶(BG)、乙酰氨基葡萄糖苷酶(NAG)的活性间存在显著的负相关(PpH-BG=0.010, PpH-NAG=0.030);在5~20 cm土层,亮氨酸氨肽酶(LAP)和乙酰氨基葡萄糖苷酶(NAG)的活性与土壤全氮(TN)质量分数存在显著的正相关(PLAP-TN=0.020, PNAG-TN=2×10^-4),酸性磷酸酶(AP)与土壤全磷(TP)质量分数间存在显著的负相关(PAP-TP=0.020)。通过对上述变量进行冗余分析,发现土壤酶的化学计量比在0~5 cm土层主要受到土壤酸碱度的影响,在5~20 cm土层则主要受到土壤全氮和有效氮质量分数的影响。【结论】暖温带针阔混交林中兴安落叶松所占比例是调控土壤养分动态的一个重要生物因子,其调控作用的发挥则主要依赖于土壤中酶的活性及其化学计量特征。图4表4参41。

[Objective]The objective of this research is to study the chemical properties and enzyme stoichiometry of soil under different proportions of Larix gmelinii forests.[Method]The investigated L.gmelinii forests were classified into six groups according to its volume proportion in the community(70%,75%,80%,85%,90%,95%),and its soil samples were monitored for the nutrient content and biochemical properties in 0-5 cm soil layers and 5-20 cm soil layers.[Result]Among the five enzymes analyzed,the activity of acid phosphatase was the highest,and the mean value of 0-5 and 5-20 cm soil layers were 463.74 and 312.91 nmol·g^-1·h^-1.In 0-5 cm soil layer,the activity of leucine aminopeptidase(LAP)was promoted by the increase of L.gmelinii proportion,and the leucine aminopeptidase activity of L.gmelinii community with 95%proportion significantly increased by 57.44%and 59.40%,compared with that of L.gmelinii community with75%and 85%proportion.The proportion of L.gmelinii in the community also affected the chemometric characteristics of soil enzymes.When the proportion of L.gmelinii reached 95%in 5-20 cm soil layer,the ratio of nitrogen-acquiring enzyme to phosphorus-acquiring enzyme was much higher than that of L.gmelinii communities with the proportion of 80%and 85%(P95%-80%=0.02,P95%-85%=0.02).However,the ratio of carbon-acquiring enzyme to nitrogen-acquiring enzymewas lowest in forest community with 95%proportion of L.gmelinii.There existed a complex correlation between soil enzyme activity and soil nutrient content,which also changed with the increase of soil depth.In 0-5 cm soil layer,soil p H negatively correlated with the activities of glucosidase(BG),and acetylglucosaminidase(NAG)(PpH-BG=0.01,PpH-NAG=0.03).In the 5-20 cm soil layer,there existed a positive correlation between soil total nitrogen(TN)content and the activities of leucine aminopeptidase(LAP)and NAG(PLAP-TN=0.02,PNAG-TN=2×10^-4),and a negative correlation between acid or alkaline phosphatase(AP)and soil total phosphorus(TP)content(PAP-TP=0.02).Through the redundancy analysis of the above variables,it was found that the enzymatic stoichiometry was greatly influenced by soil p H in 0-5 cm layer,while in 5-20 cm layer it was mainly affected by the mass fraction of soil total nitrogen and available nitrogen.[Conclusion]The proportion of L.gmelinii in the mixed coniferous and broad-leaved forest in warm temperate zone is an important biological factor for regulating soil nutrient dynamics,and its regulation largely relies on the activity and stoichiometric characteristics of soil enzymes.[Ch,4 fig.4 tab.41 ref.]