Research On The Soil Enzyme Activities And Microbialavailability And Degradation Characteristics In Changbai Mountain Forest Soils

Forest ecosystem is the largest carbon storage in the land.Forest soil respiration is an important part of terrestrial ecosystem soil respiration,and its dynamic change will have a profound impact on global carbon balance.Today's increasingly severe global climate change exacerbates soil dryness and freeze-thaw processes and the annual net flux of soil greenhouse gases,while the Changbai Mountain area is affected by its unique geographical location and climatic conditions.Whether this effect significantly changes the annual net flux of soil greenhouse gases and what feedback to climate change is still unclear.In this paper,the soil physical and chemical characteristics of the mixed forest of broad-leaved Korean pine and its adjacent secondary birch forest in different succession stages were studied in depth,and the soils of different depths(0-10 cm,10-20 cm and 20-30 cm)and organic layers in the Changbai Mountain area of Northeast China were used to study the extraction methods of dissolved organic matter in the two sub-mineral layers,through the indoor test specific discussion:(1)the relationship between soil urease and soil physical and chemical properties,soil microbes and forest stands;(2)effects of different leaching agents on the content of soil dissolved organic matter(DOM)at different depths of organic and mineral layers that to analyze the relationship between soil DOM content and soil microbial carbon and nitrogen availability and biodegradability.It is necessary to provides an important research basis for further understanding the conditions of soil net greenhouse gas flux and the establishment of carbon and nitrogen conversion processes and related models and also can provide an important support for studying the soil enzyme activity and dissolved organic matter content and its bioavailability and degradation characteristics and the response to environmental changes under different site conditions.The results show that:(1)Under different leaching treatments,the soils of the mixed forest and the secondary Betula Platyphylla were slightly acidic,while the soil pH directly affected the rate of soil enzyme involved in the biochemical reaction.Compared with the mixed forest of broad-leaved Korean pine,the soil water content of secondary birch forest is bigger,the soil bulk density is opposite,and the soil acidity of secondary birch forest is slightly larger than that of broad-leaved Korean pine forest.In the whole,the soil physical and chemical properties of the mixed forest of broad-leaved Korean pine were better than those of secondary birch and the indexes were significant.(2)Soil urease activity was most affected by microbial biomass and soil depth,and they were significantly correlated(P <0.01).The soil urease activity of the soil layer(0 ~ 10 cm)in the formation stage was significantly higher than that in the soil layer(10 ~ 20 cm)and stable stage(20 ~ 30 cm).And the soil urease activity decreased with the deepening of soil layer.The soil urease activity of different forest stands was also different due to the different vegetation stands.The soil urease activity of broadleaf pine forest was higher than that of secondary birch forest.(3)There were significant differences in the contents of dissolved organic matter between the organic extracts and the soil layers(0 ~ 10 cm)in the five kinds of extracts,and the content of hot water and hot Ca Cl2(0.01 mol / L)was higher than that of cold water and cold CaCl2(0.01 mol / L),and K2SO4(0.5 mol / L)was neutralized.(4)(MBC / TOC)and the ratio of microbial biomass N and total organic nitrogen(MBN / TN)were significantly positively correlated with the content of soil organic carbon(DOC)extracted from the five extracts;there was a significant positive correlation between the ratio of soil dissolved organic nitrogen(DON)extracted from the other four extracts and the ratio of microbial carbon to total organic carbon,as well as the ratio of microbial nitrogen and total organic nitrogen,except for cold water extract,among them,the correlation of hot water extractant is the highest.The choice of hot water extractant is more suitable for studying the variation of soil organic matter content and its response to environmental changes under different site conditions.(5)Compared with the mixed forest of broad-leaved Korean pine,the ratio of MBC / TC in the soil layer and the mineral layer of the secondary birch forest increased significantly,and the ratio of MBN / TN in 10 ~ 20 cm and 20 ~ 30 cm soil layer increased significantly.The biodegradation rate of soil organic matter in different soil extracts increased with the increase of soil depth,and there was no significant change between the two stands.The absorbance(UV254)at 254 nm decreased with the increase of soil depth and had a significant negative correlation with the biodegradability rate.