杨树根系分泌物对土壤养分和微生物的调控作用

The Regulating Roles of Root Exudates of Poplars on Soil Nutrients and Microorganisms

对于土壤微生物而言,其群落分布受到一系列因素影响,且呈现出复杂性和多样性特点,其中较为直接的制约因素就是根系分泌物,此外,土壤养分也受到的制约,为了探究根系分泌物作用机理,本文通过连续三年的实验对比分析,借助于根系分泌物溶液的研究方式,对比不同浓度下的群落分布特点,同时对土壤酶活性及微生物量的影响进行分析,并剖析其对微生物群落分布的作用,探究微生物商的反应机理。通过对比分析得知:(1)杨树根系分泌物具有多样性,其中占比较高的分别是酯类、烃类、酰胺类,其相对含量均在9%以上,其中酯类共计10种,相对含量达到54.12%;此外还包括苯酚类、酮类;从根系分泌物含量的角度来看,超过5%的合计七种,主要是顺-9-十八碳烯酸、3-乙基-5-十八烷等;(2)受根际分泌物浓度的差异影响,对于土壤有机碳、全氮、全钾而言,其含量存在较为明显的差异,且这种差异达到了0.05的显著检验水平,对于速效磷、活性酶及量碳来说亦是如此,此外,还包括微生物商、基础呼吸,但全磷较为例外,其差异并没有受到分泌物的显著制约,且未通过显著检验;与对照组相比,无论是低浓度处理LC,还是中浓度处理MC,其含量均更高;但是高浓度处理下HC,并没有突出差异,未通过显著检验;综合来看,对于根系分泌物而言,其无论是对土壤养分及酶活性,还是微生物群落分布,其低浓度下的促进作用与高浓度下的抑制效应并存;(3)虽然根际分泌物浓度存在较大的差异,但对于微生物的平均吸光值并没有产生突出的影响效应,对于物种丰度及多样性指数来说亦是如此,其差异并没有通过0.05的显著水平;与对照组相比,无论是低浓度处理LC,还是中浓度处理MC,其含量均更高;但是高浓度处理下HC,并没有突出差异,未通过显著检验;(4)通过成分分析得知,受低浓度根系分泌物处理下的影响,其土壤微生物分布及新陈代谢等方面与对照组较为接近,与高浓度处理下存在尤为突出的差异,综合来看,其对单一碳源的利用能力存在尤为突出的差异,其群落分布特点差异突出。

In order to study the regulation mechanism of poplars root exudates on soil nutrients and microorganisms,this study identified and detected the components of poplars root exudates in laboratory repeated tests for three consecutive years,and then added root exudates solution to soil.The effects of different concentrations of exogenous root exudates(CK,LC,MC,HC)on soil nutrients,enzyme activities,microbial community structure and functional diversity,and microbial metabolic entropy were studied.We found that:(1)the root exudates of poplars trees contained 10 esters(54.12%),7 hydrocarbons(15.23%),including 11.78%of aromatic hydrocarbons,1 ketone(0.98%),2 phenols(5.23%)and 1 amide(9.02%),with the highest content of esters.There were 7 substances with root exudates content more than 5%,which were cy-9-octadecenoic acid-(2-phenyl-1,3-dioxy-pentyclo-4-yl)-methyl ester(18.65%),3-ethyl-5-(2-ethylbutyl-octadecane)(11.44%),1,2-xylene(8.56%),2,6,11,respectively.15-tetramethylhexadecane(7.44%),tetradecenane(7.12%),2,4-di-tert-butylphenol(5.87%),phthalate-isobutyl-4-octane(5.22%).(2)Soil organic carbon,total nitrogen,total potassium,available phosphorus and available nitrogen contents,soil sucrase,urease,catalase,acid phosphatase activities,soil microbial biomass carbon,microbial quotient,basal respiration and microbial metabolic quotient had significant changes(P<0.05),while soil total phosphorus had no significant differences(P>0.05).The root exudates treated with low concentration(LC)and medium concentration(MC)were significantly higher than CK(P<0.05),but there was no significant difference between high concentration(HC)and CK(P>0.05).In conclusion,the effect of root exudates on soil nutrients,enzyme activities and microbial characteristics is the concentration effect of low promotion and high inhibition.(3)The average light absorption value,species richness index and diversity index of soil microorganisms had significant changes(P<0.05).With low concentration(LC)and concentration(MC)in the processing of root secretion under soil microbial average absorbance value,species richness index and diversity index were significantly higher than that of CK(P<0.05),high concentration(HC)with soil microorganisms under the average absorbance value,species richness index and diversity index and CK difference was not significant(P>0.05).(4)Principal component analysis showed that the microbial community metabolic characteristics of soil treated with low concentration of root exudates were similar to those of CK soil,which was significantly different from that of soil treated with high concentration of root exudates,indicating that they had different utilization capacity of single carbon source and their community metabolic characteristics were different.