Prediction of factors affecting fine root and litter decomposition of secondary forests in Lesser Khingan and their responses to different thinning intensities
[Objective]To investigate the effect of tending thinning on the decomposition of fine roots and litter,and to predict the driving factors of nutrient release during the decomposition of fine roots and litter,so as to lay a foundation for studying nutrient cycling in forest ecosystems.[Method]In the Dongfang Red forest farm of Xiaoxing'anling Daling Forestry Experimental Bureau,7 fixed plots of 30 m×30 m were set up,which were A(thinning intensity 10%),B(15%),C(20%),D(25%),E(30%),F(35%),and the unthinned sample plot was used as the control plot and recorded as CK.In July 2021,the decomposition experiment of fine roots and litter was carried out,and the Olson decay model was used to characterize the mass loss mode of fine root and litter decomposition,and the decomposition of fine roots and litter under different thinning intensities was studied.At the same time,the relevant indicators of stand factor,soil physical and chemical properties and soil microorganisms were investigated and measured,and the nutrient release(C release,N release,P release,K release)of fine roots and litter was carried out by random forest model to determine the most important factors affecting nutrient release.[Result]The time of decomposition of fine roots was 1.57-2.44 years,and the time of decomposition of 95%was 6.8-19.6 years.50%of litter decomposition time was 0.94-1.24 years,and 95%decomposition time was 4.05-4.06 years.The rate of litter decomposition was significantly faster than that of fine roots.The total variance interpretation rate of fine root C release by random forest fitting model was 67.42%,the total variance interpretation rate of fine root N release was 44.71%,the total interpretation rate of fine root P release was 79.43%,and the total variance interpretation rate of fine root K release was 73.96%.The total variance interpretation rate of litter C was 60.61%,the total variance interpretation rate of litter N release was 83.97%,the total interpretation rate of litter P release was 60.21%,and the total variance interpretation rate of litter K was 82.98%.The release of litter and fine root nutrients was mainly driven by their initial chemical matrix and stoichiometric ratio,microbial carbon,nitrogen and carbon-nitrogen ratio.In addition,arbor biomass had a significant driving effect on fine root decomposition.Soil bulk density and soil available potassium have significant driving effects on litter decomposition.[Conclusion]Nutrient cycling in forest is mainly affected by the properties of fine roots and litter and soil microbial mass.
fine root decompositionlitter decompositionXiaoxing'an Ridgerandom forest
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NSTL
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