Study On Leaf Litters Decomposition Of Loropetalum Chinense And Pinus Massoniana In Karst Area

The paper makes Loropetalum chinense and Pinus massoniana litter in the karst and non-karst area as the study objec by field litterbag decomposition method that make the litter decomposition experiment in the same place for a year. The research content mainly includes:changes of leaf litter weight loss rate in the litter decomposition process and predict the leaf litter decomposition time by Olson attenuation index model; Determine the initial nutrient concentrations of the litter, explore its effect on leaf litter decomposition rates, and determine dynamic change and nutrient release patterns of the litter metamer element in the decomposition process; it studies the impact of the decomposition of leaf litter on soil physicochemical properties and the variation rules of soil enzyme activities in the process of leaf litter decomposition. The main results are as follows:1. Study decomposition dynamics of litter by leaf litter decomposition bags. The results show that:the two species of leaf litter decomposition rates under different geological background are the karst area< non-karst area; the two species of leaf litter decomposition under the same geological background rates are Loropetalum chinense> Pinus massoniana. The decomposition dynamics of four kinds of leaf litter are consistent with Olson exponential attenuation model, we can infer that the time required of Loropetalum chinense leaf litter decomposition 50% and 95% in the karst area according to the model is 0.85a 3.38a, and Pinus massoniana in karst area needs 2.16a and 10.83a, the Loropetalum chinense in the non-karst needs 3.38a and 0.82a, the Pinus massoniana in the non-karst area needs 1.73a and 6.97a. It shows that leaf litter decomposition cycle in the karst area is longer than that in the non-karst area, especially the Pinus massoniana decomposition time in karst area is longer than that in the non-karst area.2. C and lignin has the largest content of the initial concentration in 4 kinds of leaf litter, followed by N, Ca, K, fibrin and P. The same species under different geological background litter initial leaf nutrient content except that the elements of C and K content had no significant difference, the initial nutrient content of N, P, Ca, cellulose in the leaves of the tree species in the karst area were greater than those in the non-karst area, the lignin content is karst area more than non-karst area, Loropetalum chinense in the karst area is greater than that in the non-karst area,but there was no significant difference between the lignin content of Loropetalum chinense in Karst area and non-karst area.Each ratio of the chemical components is Karst species< non-karst species; the nutrient content of P, Ca, K is Loropetalum chinense>Pinus massoniana between the two species in the same geological background except that there is no difference in the content of N, the content of C and lignin is Pinus massoniana species>Loropetalum chinense species, there is no obvious difference in the fibrin in non-karst area between the two species, Loropetalum chinense in the karst area>Pinus massonianain the karst atea, the chemical components are Pinus massoniana>Loropetalum chinense.3. The results show through the correlation analysis that the leaf litter decomposition rate and leaf litter initial organic carbon (C) content are significantly of negative correlation, of extremely significant negative correlation with lignin concentrations, and of significant positive correlation with K concentration, and there is a little correlation with C /N, C/P, lignin/N, lignin/fibrin but not significant.4. The dynamic change of the litter nutrient in the process of decomposition has a certain difference, the changes of C concentration show:increasing-decreasing-increasing; N is firstly increasing and then decreasing; there is obvious difference of P, the Loropetalum chinense and Pinus massoniana in the karst area are decreasing in the overall, and the Loropetalum chinense and Pinus massoniana in the non-karst area is rising; the change trend of K and lignin is firstly decreasing and then turns to rise, but the overall content of K is increasing but the lignin is decreasing; the fibrin content in the first half year is basically rising and then turns to decrease. The litter weight loss rate shows an extremely significant negative correlation with the content change of C and lignin, and shows a significant positive correlation with K by the difference analysis.5. The change rules of chemical composition ratio of the litter in the decomposition process are that C/N, lignin/N, lignin/fibrin have similar trend, they are all firstly decreasing and then increasing, the changes of C/P are more complex, the decomposition trend in the first half of the year is mainly reflected the differences between two tree species in the same geological background, Pinus massoniana shows firstly increasing and then decreasing, Loropetalum chinense is increasing, the tree species in the karst area are firstly increasing and then turn to be stablee, the tree species in non-karst area are decreasing first and then increasing in the post half year because of differences in geological conditions. We can see by weight loss rate and the ratio difference analysis that weight loss rate shows a significant negative correlation with lignin/N, lignin/fibrin.6. The releasing rule of litter elements:C and lignin are sustaining net release, and shows a significant positive correlation with litter weight loss rate, and C releasing of Loropetalum chinense and Pinus massoniana in the karst area is slower than that in the non-karst area; N element in the decomposition process is first holding and then releasing, the remaining percentage ratio order of various nutrients in the holding stage is roughly: Pinus massoniana in the karst area>Loropetalum chinense in the non karst area>Pinus massoniana in the non karst area>Loropetalum chinense in the karst area, N releasing in the karst area is faster than that in the non karst area in the releasing phase; P is firstly releasing and then enriches; fibrin is firstly accumulating and then releasing.7. The paper studies the effect of leaf fall decomposition on soil physical and chemical properties. The results show that the soil pH value has a trend of increasing after 1 year of the leaf litter decomposition, unless the soil organic matter of Masson Pine increases in the karst area, the remaining three kinds of samples are all decreasing compared the decomposition before, and N, P, K in the soil all increase, indicating that leaf litter decomposition increases the nutrients in the soil, which makes some improvement on the soil.The paper explores litter characteristics and its role in karst ecosystem in the karst area and learns the nutrient releasing dynamics by analyzing the differences between leaf litter decomposition in the karst area and the leaf litter decomposition of the same species in the non karst area, and then provides a reference for Karst Forest maintenance and reconstruction.