不同林龄尾巨桉人工林土壤养分与微生物的耦合关系

Coupling Relationships between Soil Microbe and Soil Nutrient in Eucalyptus urophylla×E.grandis Plantation at Different Stand Ages

基于对广西东南部不同林龄尾巨桉人工林下土壤养分和微生物测定及典范对应分析,探讨了不同林龄尾巨桉林土壤养分、微生物特征及其相互关系。结果表明:(1)不同林龄尾巨桉人工林下土壤有效磷和pH值的林龄效应不显著,土壤有机质、全氮、全钾、碱解氮随林龄增加基本上呈先增后减趋势,但各养分含量最高点的林龄有所不同。(2)土壤微生物种群总数、细菌、真菌及放线菌数量含量的林龄效应明显,土壤微生物种群总数量、细菌、真菌均在3a和8a龄林地含量较高,而且微生物种群中细菌比例最大,放线菌次之,真菌最小;细菌、真菌数量变化趋势相似,随林龄增长表现为增长减少再增长的趋势,放线菌数量变化没有一定规律。(3)微生物量碳(Cmic)、氮(Nmic)、磷(Pmic)的林龄效应均比较明显,Cmic从1a～8a龄林地呈折线变化,最高峰位于8a龄林地,1a龄林地次之;Nmic的变化趋势呈"V"状,1a和8a龄林地含量基本相同,最低点出现在3a龄林地;Pmic含量变化情况则相反,最高点位于5a龄林地,1a、8a龄林地含量较低。(4)典范对应分析表明,5个不同林龄尾巨桉人工林地土壤主要养分与微生物大部分不呈正相关或相关性不显著,说明影响土壤养分、微生物及其之间的关系不仅受林龄的影响,地形等其他因素也起到很大作用。

Based on the measurements of soil nutrients and microbe and canonical correspondence analysis of them,the paper aimed to reveal the relationships between soil nutrients and microbe in Eucalyptus urophylla×E.grandis plantations with different ages in southeastern Guangxi,China.The results indicated that：（1）The effect of stand ages on available phosphorus and pH were not significant,while that on other indexes differed greatly.Soil organic matter（SOM）,total nitrogen（TN）,total potassium（TK）,and available nitrogen（AN） basically increased firstly and then decreased,and the details about peaks differed.（2）The effects of stand ages on the sum of soil microbial population,bacterium,fungi,and actinomycetes were evident：the sum of soil microbial population,population of bacterium,fungi,and actinomycetes had higher values in 3a and 8a stand plantations;the variation trend of bacterium was increasing firstly,and then decreasing,and finally increasing,which was identical with fungi,while the variation trend of actinomycetes was not evident;bacterium accounted for most percentage parts in the sum of microbial population,followed by actinomycetes and fungi.（3）All the affection of stand aging on soil microbial biomass of carbon（Cmic）,nitrogen（Nmic）,and phosphorus（Pmic） was distinct.The variation of Cmic performed in a broken-line manner,peaked at 8a plantation and followed by at 1a plantation;that of Nmic presented in a “V” shape,peaking at 1a and 8a plantations and lowest value existing in 3a plantation;the variation of Pmic was opposite to Nmic,peaking at 5a plantation and lowest values occurring in 1a and 8a plantations.（4）Canonical correspondence analysis showed that most of the relationships between soil main nutrients and soil microbes were not positive or not-significant.This indicated that soil main nutrients,soil microbe as well as the relation between them was not only affected by stand age,but also influenced by the topography factors.