Effect Of Simulated Acid Rain And Nitrogen Deposition Respectively On The Leaf Litter Decomposition Of Three Dominant Trees In The Subtropical Forests

In some places, acid rain led to some phenomenon:soil acidification, nutrient leaching, soil fertility decline, vegetation withered. Under natural conditions, soil acidification is extremely difficult to reverse, if soil is a large area of acidification, the consequences would be disastrous. In the maintenance of forest ecosystem productivity, net carbon storage to ease the role of soil acidification plays an irreplaceable role in and status. Forest litter and litter decomposition for nutrient cycling, maintaining forests, preventing soil erosion, protect the soil from environmental stress, is of great significance. Previous studies of litter decomposition found a lot of work law, but the lack of contact with acid rain. And while nitrogen deposition, water stress, drought stress and other effects on litter decomposition in some reports, but acid rain effects on litter decomposition study involved very few. From the view of the study area, the subtropical study is not sufficient. Under the pressure of growing acid rain, in-depth study of acid rain on litter decomposition is very urgent in the subtropical regions of severe acid rain damage.Too much atmospheric nitrogen deposition results in a series of ecological problems:such as soil acidification, soil nutrient imbalance and water storage eutrophication. At present, the results of the impact of nitrogen deposition on litter decomposition rate can be broadly divided into three kinds: One is to promote litter decomposition, two is to slow litter decomposition and three is no significant effect. The influence of N deposition on litter decomposition is of great uncertainty, the role of test results are often the same intensity, tree species used in the experiment and the duration of such closely related to the further research should be carried out to conduct a comprehensive assessment. After Europe and the United States as the world's third largest N deposition area, we should as soon as possible N deposition on litter decomposition response to the research, a more comprehensive, in-depth understanding of N deposition on terrestrial ecosystems in China.To reveal the simulated acid rain and nitrogen deposition are typical of tropical leaf litter decomposition of tree species, the study of acid rain damage in the subtropical very serious kind of set up an experiment in Lin'an City, Zhejiang Province, the choice subtropical pine, C. glauca, litter for the study of Schima object. Set pH4.0, pH2.5 acid rain, respectively, with each gradient and 10g, 20g,40g weight of three conditions; nitrogen and high nitrogen and low nitrogen deposition has two processing; controlled trials, this study by acid rain and nitrogen deposition thickness of each species under the conditions typical of subtropical pine, Cyclobalanopsis superba leaf litter decomposition model, the main nutrient elements nitrogen, the release rule, carbon and lignin dynamics in decomposing leaf litter activity, and soil respiration of leaf litter laws, the establishment of a mathematical model of litter decomposition to analyze three typical species of leaf litter decomposition in acid rain and nitrogen deposition thickness of response characteristics and patterns of change in the global environment, the litter decomposition to provide more adequate data and theoretical basis, while the subtropical region ecological environment construction and sustainable development of forestry also plays an active role in promoting.The results show that:Analysis of simulated acid rain and nitrogen deposition were of pine, superba, C. glauca three different species of leaf litter decomposition, the results show that:acid rain inhibited leaf litter decomposition, in the same acid gradient treatments, leaf litter thicker the decomposition rate of the more Slow, and vice versa. Therefore, the thickness of leaf litter decomposition of leaf litter slowed. The decomposition rate constant k value is the characterization of the common litter decomposition rate index, k greater the faster the decomposition rate of litter. Also reflects two factors of acid rain and the thickness of the inhibition of leaf litter decomposition.The first 6 months, significantly enhanced by high N pine leaf litter decomposition, low N significantly inhibited the pine leaf litter decomposition. In the first 16 months, the N treatment suppressed to some extent, the decomposition of pine litter.6 months before the stage of processing Schima dry weight of the remaining nitrogen rate has been lower than the control group and the low N treatment, to 16 months, the remaining dry weight of the control group was significantly smaller than the high nitrogen and low nitrogen treatment; the first 6 months period, the dry weight Cyclobalanopsis high nitrogen surplus and the rate has been lower than the control group nitrogen N treatment inhibited the decomposition of leaf litter glauca, nitrogen concentration increased, the slower the decomposition of this point there superba common soil nitrogen has accumulated to a certain concentration, nitrogen is no longer a major limiting factor, other factors may change as the limiting factor. This also explains, N deposition has accumulated to a certain extent their role in litter decomposition may be transferred to the opposite effect. This is consistent with Mo JM similar results.Simulated acid rain and nitrogen deposition on these three species were leaf litter dynamics of nutrient elements. The results show that:acid rain affects the release of leaf litter or enrichment of elements, there are differences between different species, the species if the initial concentration is low, usually expressed as enrichment, the initial high concentrations of elements, usually expressed as the release of so to show the specific circumstances. Thickness of leaf litter in the rain and under the double impact of changes in nitrogen is quite complex, alternately rising and falling repeatedly, it may be related to the surrounding environment. Of nitrogen deposition on the dynamical changes of the elements is the biggest nitrogen, due to the addition of external nitrogen, increasing the concentration of nitrogen, so that the nitrogen content of leaf litter increased. Little effect on the concentration of other elements.In the beginning of litter decomposition, pine, leaf litter Cyclobalanopsis the highest urease activity, and then gradually decreased, the occasional ups and downs, to 16 months, the basic minimum, while the highest value superba in the following year was 8 month. Urease activity of leaf litter significantly affected by acid rain. Treated in the same gradient of acid rain, pine litter thicker lower urease activity, and vice versa. Therefore, the thickness of leaf litter inhibits urease activity of pine leaf litter. At the same time, we can see:20g heavy urease activity, greater than the moderate and severe acid rain acid rain,40g also do so. Can be seen, simulated acid rain on pine leaf litter thickness of urease activity was inhibited. This illustrates superba leaf litter thickness on urease activity and influence of leaf litter, but also by the impact of the season. The highest value was superba in the following year in August, August 2010, is the hottest month of the year. This study shows that inhibition of acid rain and thick leaf litter urease. cellulase activity, activation of invertase activity.Early activation of high nitrogen, urease, cellulase activity, the late inhibition. Of nitrogen deposition on urease activity of three species have some differences, different periods of cellulase have different trends. For invertase, like pine and Schima, and C. glauca are very different with both...