Process Of Typical Plant Leaves Decomposition And Its Effect On Soil Nutrients And Soil Microbial Community In Southern Area Of Ningxia

Accumulation and decomposition of plant leaves could changed soil microenvironment, improved soil nutrient content and increased soil microbial diversity. Plant leaves is a link of connect soil and plant, It plays an important role in cycle of the ecosystem material and energy. This study selected three typical herbaceous vegetation as research subjects in this area, adopted field decomposition method simulate decomposition of plant leaves, analysis the changes of plant leaves nutrients and soil nutrients and soil microbial diversity in the process of plant leaves decomposition, study the effect of different treatment on vegetation and soil properties, provided scientific basis for Loess Plateau revegetation and restoration of ecosystems biodiversity. The main conclusions are as follows:(1) Seasonal changes affect the release of nutrients in plant leaves, release of the elements were not significant in the different treatment. Original content of the element directly affects the rate of decomposition. BLX has the lowest original nitrogen, and the highest original lignin and cellulose, these conditions lead to a lower rate of decomposition under the treatment of BLX, and has lower nutrient loss in the end of decomposition. Because of the high Original nitrogen in each mixing treatment, nitrogen is released during the decomposition process. Organic carbon of each treatment showed leaching, enrichment and released during decomposition. In the early stage of decomposition, leaching and degradation of soluble materials and easy decomposed carbohydrates make organic carbon prompt release. In the late stage of decomposition, insoluble materials such as lignin and cellulose has a large rate, make the decomposition slowly. As the decomposition, release of phosphorus is consistent between different treatments, and follow the fluctuation mode of released, enrichment and released. Phosphorus enrichment has different originate time between mix treatment and single treatment. In single treatment, CMC and BLX begin enrichment in the first 45 days of decomposition, but mix treatment and TGH begin enrichment in the first 90 days of decomposition. On the first 390 days of decomposition, lignin is almost not decomposition of plant leaves from each treatment. In the first 90 days, cellulose is no significant change, but it is decomposition fast after 90 days. In the late stage of decomposition, CMC has the fastest rate of decomposition and the largest amount of decomposition.(2) There is a same trend of soil nutrient between plant leaves treatment and blank treatment, this means that the decomposition of plant stems and leaves on soil nutrients is mainly affected by external impact of changes in hydrothermal conditions. Content of plant leaves treatment soil nutrition was increased than blank treatment, this means that decomposition of plant leaves can provide some nutrients to the soil. Changes in soil nutrients of each treatment, but the difference was not significant, it is closely related with chemical composition of plant leaves. Soil total nitrogen mainly come from organic matters of plant leaves decomposition, so soil total nitrogen and organic carbon with a similar trend, content of soil total nitrogen and organic carbon reached the maximum after decomposition 135 days. The content of soil available phosphorus is mainly affected by changes in hydrothermal conditions, and it was increased slowly at rainfall adequacy in the summer. In the early stage of decomposition, content of soil ammonium was decreased, and the nitrate was increased. The content of soil ammonium did not change significantly in the whole decomposition.(3) Environmental variables were the most important factors to affect soil enzyme activities,however, plant leaf had little effect on soil enzyme activities. Soil initial nutrients had some degree effect on soil enzyme activities. For example, soil total N, soil organic matter and available nitrogen had significant effects on soil urease enzyme, soil sucrose enzyme, soil cellulose decomposing enzyme, and alkaline phosphatase enzyme. Soil available P was significantly related with alkaline phosphatase enzyme. Plant leaf decomposition could enhance the concentrations of soil nutrients and soil quality. At the later stage of plant leaf decomposition, soil urease enzyme, soil Sucrose enzyme and soil Cellulose decomposing enzyme were increased and soil alkaline phosphatase enzyme was decreased. With mixture of different plant leaf, soil enzyme activities and soil nutrients were significantly increased. There was no significant difference among different plant leaf addition treatments.(4)Soil and plant leaves nutrients and their ecological stoichiometry were main factors to affect soil microbial biomass. The environment with suitable soil water and temperature improve soil microbial biomass. At the end of plant leaves decomposition, soil microbial biomass carbon and nitrogen were greatly correlated with soil and plants nutrition, suggesting that soil and plant leaves nutrients affected soil microbial biomass. Soil microbial biomass nitrogen were significantly correlated with soil total N(P<0.001). There were significant positive correlation between soil microbial biomass carbon and nitrogen and plant leaves total N, total P and lignin. At the beginning of plant leaves decomposition, microorganism could make full use of soil mineral nutrients and enhance their growth. The greater growth of microorganism might accelerate soil mineralization, leading the decline of soil nutrients. With progress of plant leaves decomposition, soil microbial biomass declined for the lower nutrients which couldn’t meet the requirements of microorganism. After 435 days’ decomposition, soil microbial biomass nitrogen for the plant leaves addition treatments was lower than that for CK treatment. There was no significant difference among different plant leaves addition treatments.(5) We analyzed soil microbial communities by the method of 454 high prosequnecing. The results after 435 days’ decomposition showed that bacterial indexes of Chao, Shannon and Ace of the treatments with additions of plant leaves were higher than those of CK treatment, but Simpson index was lower than that of CK treatment, suggesting plant leaves decomposition could improve the diversity of fungi. At the phylum level, the dominant taxonomic bacterial phyla observed in all samples were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes, which were account for 90%. The relative abundance of Actinobacteria were appropriately about 40%. Ascomycota, Basidiomycota and Glomeromycota were the dominant taxonomic fungal phyla, with the relative abundance of 95%. The relative abundance of Ascomycota was appropriately about 50% in all samples. At the class level, Dothideomycetes, Sordariomycetes, Agaricomycetes, Pezizomycetes and Glomeromycetes were the dominant taxa, and the relative abundance of them varied from 60% to 80%. At the order level, Pleosporales, Pezizales, Agaricales, Hypocreales and Glomerales were the most abundant taxa which were accounted for 75%. Actinobacteria and Basidiomycota played important roles in decomposing plant leaves which helped improve soil quality. plant leaves decomposition had great effects on bacterial communities and soil nutrients cycling which provided important significance for global changes.