| In order to explore the dynamic changes of nutrients and phyllospheric microganism during the decomposing process and to reveal the intrinsic relationship and to find influencing factors,this study chose the leaf litter of Quercus wutaishanica as the research object in Renjiatai Forest Farm of Ziwuling,Shaanxi Province.There were three treatments:normal addition(10 g)and doubling addition(15,20 g)leaf litter were placed on the litter layer,humus layer and soil layer for decomposition.The dynamic sampling method was used,we determined the nutrients(C?N?P?K),mass loss rate,and phyllospheric microganism(bacteria and fungi)of leaf litter,in order to reveal the characteristics of nutrient elements,ecological stoichiometry,and to reveal the regularity of phyllospheric microganism communities during seasonal dynamic changes.The relationship between the physical and chemical properties of leaf litter and the changes of the phyllospheric microganism can provide basic data for understanding the material circulation processes and the influencing mechanisms.Results:(1)The total carbon contents of the leaf litter in the soil layer were greatly reduced during the decomposition.In the same environment,the greater amount of leaf litter,the greater amount of exogenous carbon supplementation,and the slower release rate of carbon.At the same time,the release and accumulation of total nitrogen in the litter layer was affected by hydrothermal conditions and it was also affected by the weight of leaf litter which was the dominant factor.The total nitrogen contents showed an increasing trend during the litter decomposition process,and the release rate of total nitrogen(17.23%)was lower than the total carbon(38.48%).The initial content of total phosphorus(0.37g/kg)was too low in leaf litter on litter layer and humus layer,which lead to a rapid increase during the decomposition.The different placement layers had little effect on the total phosphorus enrichment and release during the decomposition of litter.In the same placement layer,the external hydrothermal conditions were consistency,the main factor that caused the difference in the phosphorus accumulation index was the weight of the leaf litter,and the total phosphorus accumulation index of 15 g leaf litter was relatively high(NAI-K 154.44%).The change trends of total potassium contents in litter layer and humus layer of three different added leaf litters were consistency during decomposing process.The total potassium contents of leaf litter on soil layer were always higher than the other layers.The placement of layers was main factor that caused the difference in total potassium contents during decomposition.Leaf litter was placed on soil layer,the total potassium in the soil will be continuously added to the leaf litter in the decomposition period,and contents were increased.(2)During the seasonal rainfall period,microorganisms colonized large numbers in litters.Strong life activities required microorganisms to absorb nitrogen and phosphorus from the outside,then the nitrogen and phosphorus contents in the leaf litter will increase(1.64g/kg?0.34g/kg),and the carbon is continuously released during decomposition process.Therefore,the C/N and C/P under different treatments showed a decreasing trend as a whole.The content of total carbon in the litter decomposition process is high and the variation is small.The main factors affecting the ratio of carbon to nitrogen,phosphorus and potassium are the changes of nitrogen,phosphorus,and potassium contents.The leaf litter total potassium contents will be significantly higher which placed on soil layer,mainly due to potassium from soil added into the leaf litter.Therefore,placement layer impacted on the total potassium contents of the litter decomposition process also was the main factor affecting the C/K ratio.But the difference weight additions of leaf litter were not significant factor.(3)In the same placement layer,the mass loss rate of the normal added leaf litter(litter layer 38.95%,humus layer 36.42%)was higher than that of the doubled 15 g leaf litter(litter layer 32.83%,humus layer 26.78%),and was also higher than the doubled 20 g leaf litter(litter layer 30.88%,humus layer 25.46%).Moreover,under the same addition weight treatment method,the mass loss rate of leaf litter on the litter layer was higher than that of the humus layer,and the mass loss rate of leaf litter at the humus layer was higher than that at the soil layer.In the same climatic environment,the mass loss rate was affected not only by the chemical composition of the dead leaves but also by the addition weight and the placement layers when the leaf litter was decomposing.There was a significant negative correlation between the C/N ratio and the mass loss rate of the leaf litter in the decomposition process(R~2=0.6899;R~2=0.6291).The smaller C/N ratio,the more mass loss,this was mainly because of the low C/N ratio and the high total nitrogen content and high microorganisms activity is related.And then the decomposition rate of leaf litter was faster.The total phosphorus content was low and the potassium was mostly in the unbound state at the initial stage of leaf litter decomposition.Therefore,the relationship between the mass loss rate of the leaf litter and total phosphorus and total potassium was not obvious.(4)There were dominant groups of phyllospheric microganism in this experiment.The predominant phyllospheric microganism groups were Proteobacteria(67.56-80.05%)and Ascomycota(77.10-99.31%)in different seasons.The predominant phyllospheric microganism groups were the?-Proteobacteria(38.28-47.87%)and Sordariomycetes(46.17-67.71%)at class levels.In the spring,the hydrothermal environment was well,which made the phyllospheric microganism multiply and increasing the diversity.In summer,the predominant strains rapidly colonize in the early stages of decomposition,creating survival conditions for other strains,at which time microbial diversity was relatively small.In autumn and winter seasons,the abundance of some phyllospheric microganism was reduced,due to the reduction in the amount of rainwater and the decrease in temperature.While the relative abundance of microorganisms with strong tolerance,such as?-Proteobacteria(47.87%)was relatively high in winter and Agaricomycetes(6.82%,7.05%)was relatively high in autumn and winter.The basic physicochemical properties of the leaf litter had significant effects on the composition and distribution of the phyllospheric microganism.The composition and distribution of the bacterial communities in the deciduous trees in different seasons were mainly affected by the leaf litter moisture content and C/N,and the composition and distribution of the fungal communities were mainly affected by N/P and total potassium content,while other factors(pH,nutrient factors,and eco-stoichiometric ratio)also had different degrees of influence on different microbes. |
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