Litter Decomposition Of Typical Urban Greening Tree Species In Typhoon-affected Areas

Litter decomposition is not only the connection channel between above-and below-ground components in the ecosystem,but also the basis of material circulation and nutrient turnover.The decomposition process is regulated by climate,litter quality and soil biological community.Typhoon is an extreme disaster climate phenomenon that interferes with coastal forest ecosystem.In particular,the coastal forests produce a large number of abnormal litter,which deeply affects the material cycles and energy flow under the disturbance of typhoon.Abnormal litter lacks the process of nutrient resorption,the change in litter quality may directly or indirectly affect the decomposition process,such as affecting the selective feeding of soil fauna,and then altering the decomposition process.However,the effects of typhoon on the abnormal litter decomposition of urban forest,the effects of soil fauna on the abnormal litter decomposition process,and the litter decomposition process whether any difference between on soil and hanging on shrubs and grass have not been demonstrated.Therefore,in order to understand the impact of typhoon interference on the material cycle and energy flow of urban forest ecosystem,we selected the research site in Taizhou City,Zhejiang Province,which is frequently disturbed by typhoon,and selected representative urban garden tree species(Cinnamomum camphora,Salix babylonica,and Koelreuteria bipinnata var.integrifoliola)as the research object.The litterbag method was conducted to study the effects of typhoon “Hagupit” on abnormal litter decomposition process.1.The initial concentrations of bioelements(carbon,nitrogen and phosphorus)in abnormal litter under typhoon interference was significantly higher than that of normal litter(except the nitrogen concentration of K.bipinnata),while the concentrations of lignin and cellulose were lower than that of normal litter(except the lignin concentration of C.camphora and the cellulose concentration of S.babylonica),indicating that abnormal litter quality is higher than normal litter quality.The concentration of potassium(K)in abnormal litter was significantly higher than that in normal litter,and the sodium(Na)concentration was also higher than that in normal litter,but it was not significant.Additionally,the concentrations of calcium(Ca),magnesium(Mg),aluminum(Al),iron(Fe)and manganese(Mn)were significantly lower than normal litter(except the Ca concentrations of K bipinnata and Al concentrations of S.babylonica).It is possible that the accumulation of these metal element concentrations before physiological litter is conducive to the decomposition after falling.2.The abnormal litter by typhoon interference had higher decomposition rate,especially the mass loss rate of abnormal litter of C.camphora and S.babylonica at each key period.The concentrations of carbon,phosphorus and potassium in abnormal litter were released greater extent than normal litter during the whole process of decomposition,and the concentration of nitrogen was significantly higher than normal litter in the whole decomposition process.Besides,abnormal litter reached the threshold of nitrogen release before normal litterfall.Additionally,the lignin concentration of abnormal litter was significantly lower than normal litter at each critical period,and the dynamics of cellulose concentration in abnormal litter produced by typhoon interference was significantly different from that in normal litter.However,the concentration of cellulose in physiological and abnormal litter depended greatly on tree species and critical periods.Results of repeated measures ANOVA also showed that the interaction between species and typhoon also had a significant effect on cellulose concentrations.3.By the end of the decomposition experiment,the contribution of soil animal community to litter mass loss varied slightly with physiological and abnormal litter.However,the contribution of soil animal to physiological and abnormal litter mass loss varied greatly with critical periods.In the first 90 days of decomposition,the contribution of soil fauna to abnormal litter mass loss was significantly higher than that physiological normal litter,while in the plum rain season,the contribution of soil fauna to physiological litter mass loss increased significantly.The contributions of soil fauna to the concentrations of carbon,phosphorus,cellulose,potassium and sodium in foliar litter varied greatly with physiological and abnormal litter produced by typhoon.Moreover,the selection preferences of soil fauna for physiological and abnormal litter changed with the critical period.On the whole,soil fauna prefers to forage the abnormal litter owing to higher nutrient concentrations of abnormal litter.4.At the end of the decomposition experiment,the mass loss rate of physiological and abnormal litter on the lawn was higher than on soil surface,but there was no significant difference.Compared with litter on soil surface,litter had lower concentrations of carbon and potassium in litter,and higher concentration of nitrogen in litter on the lawn.However,there were significant differences in phosphorus concentration of litter on between soil surface and lawn.Interestingly,the contribution of soil animal to litter mass loss on the lawn was higher than that on soil surface.During the whole decomposition stage,the concentrations of soil fauna to the mass loss rate,carbon,nitrogen,lignin and cellulose of abnormal litter were significantly higher than those of physiological litter.Therefore,whether on the soil surface or on the lawn decomposition environment,soil fauna preferred to forage abnormal litter with higher quality,and further improved the decomposition rate of litter.5.Correlation analysis showed that the litter mass loss rate was significantly positively correlated with litter temperature,initial nitrogen and phosphorus concentrations,and significantly negatively correlated with initial concentrations of lignin and cellulose concentrations,and the ratios of C/N,C/P,N/P,L/N and L/P.The contribution rate of litter mass loss of soil fauna was also affected by litter temperature,humidity and initial lignin concentrations.Results of repeated measures ANOVA showed that soil fauna significantly affected the mass loss rate,and the concentrations of carbon,lignin and cellulose in litter.Therefore,abnormal litter with higher quality and edibility had higher decomposition rate compared with physiological litter.Taken together,our results indicate that typhoon disturbance,soil fauna,climate,species,different decomposition environments and complex interactions jointly determine the decomposition of litter leaves of typical urban greening tree species.Typhoon disturbance directly changes the litter quality and indirectly affects the contribution of soil fauna,thus promoting the loss of litter weight and nutrient release of litter leaves,and lawn decomposition environment can greatly stimulate the contribution of soil fauna to litter decomposition.The mechanism of accelerated material cycle has become a prerequisite for the maintenance and stability of coastal forest ecosystem.