Allelopathic Effects Of Exogenous Phenolic Acids On Soils Of Eucalyptus Grandis G2Sprout Pure Forest And Mingled Forest Of It And Dalbergia Odorifera

Since successive plating of pure eucalyptus forest tends to result in lower productivity of man-made forest and soil degradation, the allelopathic effect of phenolic substances is regarded as one of the major reasons. By artificially adding5exogenous phonolic acids, including benzoic acid, p-hydroxybenzoic acid, salicylic acid, ferulic acid and vanillic acid, this research studies the allelopathic effects of exogenous phenolic acids on soils of eucalyptus grandis G2sprout pure forest and mingled forest of it and dalbergia odorifera, makes analysis and comparisons of their background values and variation trend of soil physicochemical properties, explains whether it is appropriate to select dalbergia odorifera as the associated species, explores the respective effects of each phenolic acid and the mixed5acids on environmental factors and correlations, which would conclude the different effects of different kinds of phenolic acids. This experiment reached some conclusions:(1) Phenolic acids had significant inhibiting effect on most of the soil pH, nutrient availability, enzymatic activities and microbial populations of the two forest types. The mix of eucalyptus grandis G2sprout and dalbergia odorifera could improve soil physicochemical properties, which was the reasonable associated tree species. The pure forest soil pH was more acid than the mixed forest soil; The availabilities of Fe3+, Cu2+, Zn2+, Ca2+, K+, Mg2+, NO3--N and PO43-in mixed soil were greater than pure forest, Mn2+、NH4+-N were on the contrary; The background of urease activity value in mixed soil was greater than pure forest of eucalyptus, acid phosphatase and polyphenol oxidase were on the contrary. The number of soil bacteria, fungi in mixed forest soil were greater than the pure forest, actinomyces was on the contrary.(2) Under the continuous processing of mixed acid, the pH of pure forests and mixed forests soil kept falling. The availabilities of Fe3+、Cu2+、Mn2+、K+、 Ca2+、Mg2+、NO3--N、NH4+-N、PO43-in pure forest soil are declining, Zn2+instead. The availabilities of Cu2+、Zn2+、K+、Ca2+、Mg2+、NO3--N、NH4+-N、PO43-in mixed soil were declining, Mn2+instead, Fe3+was rising after falling. Under the continuous processing of mixed acid, the activity of urea enzyme and polyphenol oxidase was on the decline, the activity of acid phosphatase was on the rise in the double forests. Under the continuous processing of mixed acid, the number of microbial was greatly reduced in the double forests. The pH, nutrient availability and the number of microorganisms in mixed forests soil generally reduced more slowly than the pure forest, mixed forests could alleviate the decrease of phenolic acids’affections on soil physical and chemical properties. (3) P-hydroxybenzoic acid exerted the most significant effect on lowering pure forest soil pH; salicylic acid produced the most significant effect on lowering mingled forest soil pH.(4) Salicylic acid had significant effect on the availabilities of Ca2+、Mg2+、 K+and NH4+-N in pure forest soil; p-hydroxybenzoic acid produced significant effect on the availabilities of Ca2+, Mg+and NH4+-N in pure forest soil. Benzoic acid had significant effect on the availabilities of Fe3+, Mn2+and NO3--N; vanillic acid had significant effect on the availabilities of Fe3+, Cu2+and NO3--N; ferulic acid had significant inhibiting effect on the availabilities of Fe3+and Mn2+. In treatment of mingled forest soil by exogenous phenolic acid, vanillic acid exerted significant inhibiting influence on the availabilities of Cu2+, Mg2+and K+; ferulic acid had significant effect on lowering the availabilities of K+and PO43-; salicylic acid had significant impact on lowering the availabilities of K+, Mn2+and PO43-; p-hydroxybenzoic acid had significant effect on improving the availabilities of Fe3+and Mn2+; benzoic acid had significant effect on improving the availabilities of NO3--N.(5) Salicylic acid had the most significant effect on urease in pure forest soil, which was increased by29.8%; benzoic acid had the most significant effect on acid phosphatase, which was increased by12.4%; vanillic acid had the most significant effect on polyphenol oxidase, which was increased by42%. Salicylic acid had the most significant effect on acid phosphatase in mingled forest, which was increased by27.6%; vanillic acid had the most significant effect on polyphenol oxidase, which was increased by42%; benzoic acid had the most significant inhibiting effect on urease activity in mingled forest, which was decreased by42%.(6) Ferulic acid had the most significant inhibiting effect on fungus quantity, which was decreased by96.9%. Ferulic acid had the most significant inhibiting effect on bacteria in pure forest soil, which was decreased by98.3%; benzonic acid had the most significant effect on bacteria in mingled forest soil, which were decreased by99%. Only vanillic acid had an obvious accelerating effect over actinomycetes, which were17times increased.(7) The interactions between soil environmental factors changed when treated with different phenolic acids. Under the treatment of p-hydroxy benzoic acid, except the number of fungi and a few factors, most of the factors were positively correlated. Under the treatment of vanillic acid, in general microbial numbers had the most significantly negative correlation between mineral ions, with Zn2+, NO3--N significantly negative correlation. Under the treatment of ferulic acid, the majority of ions between the overall were positively correlated, and the soil pH, number of fungi, actinomycetes, acid phosphatase had significant or extremely significant negative correlation. Benzoic acid treatment, most of the minerals between ion and positively correlated with bacteria, Zn2+, fungi between overall quantity, enzyme activity were positively correlated. Under the treatment of salicylic acid, the pH, the number of fungi had significantly positively correlation, and Mg2+, Cu2+, Zn2+, NO3--N efficiency were very significant negative correlated.