The Dynamic Of Litterfall Decomposition And Nutrient Release In Natural Grassland Of Guizhou Karst Regions

Litterfall plays an important role in material and energy conversion between plant and soil.Litterfall decomposition with nutrient and energy release which provide soil microorganisms and maintain the detritus food chain.As one of the important ecosystem functions,litterfall decomposition controls the return of nitrogen,phosphorus and other nutrient elements to the soil which makes the nutrients in a relatively stable state.In this research,the decomposition bags were used to investigate the litterfall decomposition and its response to soil factors in the natural grasslands of Dafang,Guangling and Dushan in Guizhou province which have obvious karst gromorphology.By periodically determining litterfall residue,soil factors,and litterfall nutrient residue in plots.Olsen equation model was used to simulate litterfall decomposition.Litterfall decomposition rate and the relationship between nutrient release and soil factors were used in the regression analysis model to explore litterfall nutrient release mechanism.The conclusions are as follows:(1)In this research,the main compositional species of the three grasslands litterfall were Cymbopogon caesius and Miscanthus floridulus.The leaf in the three grasslands litterfall was more than 80%,which was the main component of litterfall.The annual litterfall amount of the three grasslands were 157.16-222.46 g/m~2.The amount of litterfall increased first and then decreased with time.The litterfall amount reaches the maximum in July-September.The proportions of litterfall in the three grasslands growing seasons(July-December)were 55.64%,61.87%,and54.91%.(2)The litterfall remaining decreased sharply in the initial stage of decomposition,and with the decomposition progressed,the rate of decay of the remaining decreased and gradually became flat.The entire decomposition process showed an oblique“L”distribution.The simulation of litterfall decomposition over time by the Olsen equation index model shows that the 7 litterfall decomposition coefficients range from 0.001384 to 0.002742.The treatment DSTH litterfall decomposition coefficient is the largest,and the time required for the 50%litterfall decomposition takes 0.457 years,the 95%of litterfall decomposition takes 2.757 years.The litterfall decomposition coefficient of the treatment GLTZ was the smallest,the time required for the decomposition of 50%litterfall takes 1.024 years,and the time required for the decomposition of 95%litterfall takes 5,583 years.(3)The litterfall decomposition rate is mainly affected by soil temperature,water content,and electric conductivity,among which soil temperature promotes litterfall decomposition,and soil water content and electric conductivity inhibit litterfall decomposition.The litterfall decomposition rate was mainly affected by the content of soil organic carbon and total nitrogen.Soil organic carbon inhibited the decomposition and soil total nitrogen promoted the decomposition.(4)There are three models of litterfall nutrient release,enrichment-release,leaching-enrichment-release,and leaching-release.Soil temperature,water content,organic carbon,total nitrogen and total phosphrous content are the dominant factors which affect the litterfall nutrient release.(5)The litterfall nutrient release rate of natural grassland in Dushan is higher than other grasslands.During the decomposition,organic carbon and total potassium show a net release.The natural grassland in Guanling natural grassland was enriched and the remaining grassland was released.In the natural grassland,total phosphorus was enriched in the net and the remaining grassland was released.In the sample areas,the annual nutrient release was higher and the nutrient turnover was faster.