Root Decomposition And Nutrient Dynamics On Rhizosphere Soil In Complex Ecosystem Of Alnus Formosana-Lolium Multiflorum Lam

A nylon mesh bags method was conducted in a complex ecosystem of Alnus formosana-Lolium multiflorum lain to study the process of decomposition,dynamic of nutrient release in different phases of fine root,grass root and mixed root,At the same time research of nutrient dynamics in the rhizosphere with peeling method could put forwards to the sustainable cotmtermeasure and management techniques of this model.We get these results as follow:In a complex ecosystem of Alnus formosana-Lolium multiflorum lam model:rate of weight loss of fine root and grass root showed exponential relationship with decomposition time,with yearly weight loss of 60.53%,67.77%,62.89%,83.07%and 75.95%for fine rootΦ0～1mm,Φ1～2mm,Φ0～2mm,grass root and mixed root respectively.At the initial phase of fine root decomposition,N,P and Ca concentrations increased obviously,while K concentration declined adversely,and the Mg concentration had fluctuated slightly;Grass root and mixed root N,K concentrations had a same trend as fine root during the course of decomposition,but other nutrient elements concentrations had the different trends from fine root.There was a same trend of remaining percentages of C,K,Mg,P as weight loss during the decomposition of root,but the remaining percentages of N and Ca had a slight decrease.After 90 days decomposition,K remaining percentages of fine rootΦ0～1mm was 35.05%,others were below 30%.After 1 year decomposition,N remaining percentages of fine rootΦ0～1mm was 52.32%,fine rootΦ1～2mm,Φ0～2mm were both about 40%;P remaining percentages of fine rootΦ1～2mm was 47.22%,and fine rootΦ0～2mm,Φ0～2mm were both about 39%;Ca remaining percentages of fine rootΦ0～1mm,Φ1～2mm were both above 60%,but fine rootΦ0～2mm was 55.08%;Mg remaining percentages of fine rootΦ0～2mm,Φ0～2mm were both about 27%,and fine rootΦ1～2mm was 22.98%;The nutrient remaining percentages of grass root were significant lower than fine root except Mg;The nutrient remaining percentages of mixed root were between fine root and grass root.The correlation coefficients between the initial chemical composition and decomposition rate of root;the content of lignin is the best index of others.Significant correlation was found between lignin concentration and the rate of weight loss, furthermore,the relationship was increased from 30 days(R²=0.749),to 180 days (R²=0.885^*),and then to 360 days(R²=0.973^**).The rate of weight loss and nutrient release of fine rootΦ0～2mm in forest-grass model was different from natural model.After one-year decomposition,The remaining percentages of N,K,Ca in forest-grass model were significantly lower than those in natural model,but there was no significant difference of remaining percentages of P,Mg and weight between two models.This research found that the decomposition rate of root mixtures between fine rootΦ0～2mm and grass root was different between both singular materials and N,P,K,Ca,C release rate were different between them,too.however,Mg release rate was quicker than both singular materials;According to decomposition in the total year,when fine rootΦ0～2mm and grass root were mixed,the decomposition rate,P,K and Mg release rate were increased significantly,no visible increase was found in the from of N,however,C release rate was decreased significantly;The interactions between fine rootΦ0～2mm and grass root were different in the phase of mixed decomposition.As far as the all-year was concerned,both models total N increased in the rhizosphere, hydrolytic N contents in the rhizosphere soil and in forest bulk soil in forest-grass model were higher than those in natural grass model;Significant negative correlation was found between total N of fine root and hydrolytic N in rhizosphere(P＜0.01),forest bulk soil (P＜0.05),but no visible relationships were found with total N in rhizosphere and forest bulk soil(P＞0.05) through Correction analysis.No visible increased was found in the from of total P in the rhizosphere;total P contents in the rhizosphere soil and forest bulk soil in forest-grass model were lower than those in natural grass model,so it should be pay attention to applying P fertilizer in the process of management;Available P in the rhizosphere was higher than that in bulk soil all of the year in forest-grass model,but available P in the rhizosphere was lower than that in bulk soil in several parts of 1 year in natural grass model;No significant correlation was found between total P of fine root and available P in the rhizosphere soil and in bulk soil(P＞0.05),however,it could be found significant positive correlation between total P of fine root and total P in the rhizosphere soil and in bulk soil(P＜0.05).The total K showed enrichment in the rhizosphere sometimes,and deficit other times of both models;Available K in soil of the rhizosphere was higher than in bulk soil most time of the year in forest-grass model,but there was no significant correlation between rhizosphere soil and bulk soil;There was no significant correlation between total K of fine root and available K in the rhizosphere soil,available K in the bulk soil,total K in the bulk soil(P＞0.05),however,it could be found significant positive correlation between total K of fine root and total K in the rhizosphere soil(P＜0.05).