Effects Of Endophytic Fungi Of Cunninghamia Lanceolata On Leaf Litter Decomposition And Soil Enzyme

Forest litter is the metabolite of forest plants in the process of its growth and development,as an important source of soil organic matter and nutrients in forest ecosystem.Decomposition of leaf litter plays an important role in the cycle of forest ecosystems,and soil microbes play a key role in this process.In order to investigate the effects of endophytic fungi on nutrient release and soil enzyme activity during the decomposition of leaf litter of Cunninghamia lanceolata,this paper took leaf litter of Cunninghamia lanceolata as the research object,and endophytic fungi CG2、AY13、AJ14(numbered A、B、C)selected from the roots,stems and leaves of Cunninghamia lanceolata as test strains,which had a significant effect on the growth of Cunninghamia lanceolata and the alleviation of low phosphorus stress.The simulated leaf litter decomposition experiment of Cunninghamia lanceolata was designded,and groups added with single bacteria A,B,C and their mixture AB,AC,BC were set as treatments,and groups added without any endophytic fungi were set as blank controls.The mycelium and fermentative sterilized fungus liquid were cultivated and extracted from strains,and all of them were added into the soil buried with litter in the bowl to simulate the litter decomposition experiment.And the mass loss rate and nutrient contents of leaf litter,and the soil enzyme activity in the tested soil were measured and analyzed after the experiment.This experiment was designed to explore the degradation effects mechanism of endophytic fungi on leaf litter of Cunninghamia lanceolata,and to screen out the best strains and the best matching way to provide new ideas and tools to enhance forestry production and to solve soil productivity decline problem in continuous plant of Cunninghamia lanceolata.(1)The effect of endophytic fungi of Cunninghamia lanceolata on the mass loss rate of leaf litter.With the progress of decomposition,the mass loss rate of leaf litter increased under the two treatments of mycelium and fungus liquid.The mycelium treatments could improve the mass loss rate of leaf litter more effectively than the fungus liquid treatments under the same strain.The effect of mixed fungi was better than that of single fungus,and the most prominent treatment was AC mycelium treatment,whose mass loss rate increased by 24.01%compared with CK treatment.The degradation ability of A and C strains were higher than that of B strain among the three strains of A,B and C.(2)Effects of endophytic fungi of Cunninghamia lanceolata on the nutrient release of leaf litterThe change trends of nutrient content and stoichiometric ratio of the leaf litter were different under the different treatments of endophytic fungi of Cunninghamia lanceolata.With the progress of decomposition,carbon,phosphorus,calcium and magnesium content declined overall,which indicated the release state;the potassium content fluctuated greatly,but demonstrating the release state overall;the nitrogen content showed an upward trend overall,which showed the accumulation state;carbon nitrogen ratio assumed a decreasing trend,and carbon phosphorus ratio showed an increasing trend in most of the treatments.From the treatments of mycelium and fungus liquid,except that the response of potassium and calcium elements of leaf litter to mycelium treatment was more significant,there wasn’t significant difference among the responses of other elements and stoichiometric ratio to mycelium and fungus liquid treatments.There was no treatment that can promote release or enrichment of all nutrients.In the whole process of decomposition,the effects of different treatments of three endophytic fungi on the nutrient release and stoichiometric ratio of leaf litter were different,but the effect of single fungus treatment on leaf litter nutrient and stoichiometric ratio was more significant than that of mixed fungi,especially A single fungus treatment.For the carbon element,A mycelium treatment had the most significant effect on the release of organic carbon than the other treatments,whose organic carbon content reduced significantly by 16.74%compared with CK at the end of the first fungi treatment cycle.For the nitrogen element,the nitrogen content of most strain treatments were higher than that of CK,but only A fungus liquid and BC mycelium treatments promoted the enrichment of nitrogen element significantly,which increased respectively by 17.05%and 14.14%compared with CK.For phosphorus element,the phosphorus content of all strain treatments was significantly higher than that of CK treatment,which was not conducive to the release of phosphorus,especially A mycelium treatment.For potassium element,only C fungus liquid treatment reduced the potassium content significantly,and decreased by 28%compared with CK treatment.For calcium element,the differences between all treatments and CK treatment were not significant throughout the period of decomposition.For magnesium element,each treatment did not show a significant effect on its release.For carbon nitrogen ratio,B,C mycelium and A fungus treatments reduced the carbon nitrogen ratio of leaf litter significantly,and decreased by 19.05%,21.15%,28.56%compared with CK treatment.For carbon phosphorus ratio,A,B,C and BC mycelium treatments and A,B,AB and BC fungus liquid treatments reduced the carbon phosphorus ratio of leaf litter significantly,especially A mycelium,A fungus liquid and B mycelium treatments,which reduced by 43.05%,35.5%and 17.88%compared with CK treatment.(3)Effects of endophytic fungi of Cunninghamia lanceolata on soil enzymes activityThe change trends of soil enzymes activity under different treatments were different.With the progress of decomposition,the activities of soil cellulase,lignin peroxidase,urease and acid phosphatase increased and soil invertase decreased,and soil laccase decreased under single fungus treatments while increased under mixed fungi treatments.The effects of mycelium and fungus liquid treatments on different soil enzymes activities were different to each other.The effects of mycelium were better than fungus liquid treatment for soil cellulose and invertase,while the effects of fungus liquid were better than mycelium treatment for lignin peroxidase and acid phosphatase,but there were no significant differences between mycelium and fungus liquid treatments effects on laccase and urease.All in all,the effects of different treatments on soil enzymes activities of three endophytic fungi were enhanced when compared with control,and mixed fungi treatments were better than single fungus treatments.Soil cellulose activities significantly increased under C,AB fungus liquid and AC,BC mycelium treatments by 56.46%,37.41%,24.83%,23.72%when compared with control.Soil laccase activities significantly increased under AB,AC,BC mycelium and fungus liquid treatments,the laccase activities of the most significant BC treatment increased by 36.75%when compared with control.Soil lignin peroxidase activities significantly increased under all endophytic fungi treatments except AC mycelium and A,BC fungus liquid treatments,and the lignin peroxidase activities of the most significant C,AB treatment increased by 43.97%,37.84%when compared with control.Soil urease activities significantly increased under all endophytic fungi treatments except BC fungus liquid treatments,and the effects of B,AC mycelium and fungus liquid treatments were the most significant,and the laccase activity under AC fungus liquid treatment was the highest which increased by 69.78%when compared with control.Soil invertase activities significantly increased under A,AB mycelium and AB fungus liquid treatments,and their invertase activities increased by 78.84%,162.9%,111.01%when compared with control.Soil acid phosphatase activities significantly increased under all mycelium and fungus liquid treatments,and the effects of AC mycelium and C,AC,BC fungus liquid treatments were the most significant,and the acid phosphatase activities under C,BC fungus liquid treatment were the highest,which increased by 163.65%,134.62%when compared with control.(4)Correlation analysis of substrate mass and soil enzyme activity of leaf litter of Cunninghamia lanceolataAt the end of decomposition,correlation was established by coefficients of the mass loss rate,nutrient content,stoichiometric ratio and soil enzyme activity of leaf litter of Cunninghamia lanceolata under the two treatments of mycelium and fungus liquid respectively.The results showed that the correlation between the indicators under mycelium treatments was stronger than that of fungus liquid treatments,in particular,the correlation between the mass loss rate,the nutrient content and stoichiometric ratio under mycelium treatments was significantly stronger than that of fungus liquid treatments.There was a significant difference in the correlation of soil enzyme activity between mycelium and fungus liquid treatments,and there was a positive correlation between soil enzyme activities under fungus liquid treatments,but there was a negative correlation between individual enzyme activities under mycelium treatments.