Research For The Dynamics Of Organic Acids During The Decay Of Plant Remainders In Soils

In the area of Ziwuling forest after recovering of secondary forest, the degrees of soil development were varies in different parts of landform because of the variations in soil water contents, the sequence of vegetation recovery and vegetation types. This study has analyzed the soil nutrient under different vegetations. Selecting corn remainder, Spodiopogon sibiricus remainder, alfalfa remainder, Quercus liaotungensis remainder and Hippophae rhamnoides remainder as decaying materials, the characteristics of the remainders during the process of decaying and the change of organic acids in remainders during the process of decaying was also studied by normal analysis combined with HPLC. It can accumulate data for the research of the accumulation and decomposition of soil organic matter, the situation of soil fertility, the dynamic of organic acid, and also can provide foundations for soil and water conservation and the reconstruction of environment. The main conclusions were as follows:1. The vegetation types made a significant effect on the content of soil organic matter, active organic matter, total N, available N, available P and available K, and the nutrient content almost increased followed by the sequences of vegetation succession. There is no significant effect on total P and total K, the soil nutrients in abandoned field were lower than those of farmland, which proved that the condition of agroecotype had a certain protective effect on soil fertility. In the hill area of the Loess Plateau, rebuilding of forest from cropland in slopes and vegetation recovery could improve the status of soil nutrients.2. According to the changes of decaying remainders, the decaying process can be divided into 4 stages: the stage of fast decomposition---the stage of stagnation decomposition ----the stage of slow decomposition---the stage of tending to be stable. Olsen's exponential attenuation model performed well in regressing the relationship between the decaying rate of plant remainder and the decaying time.3. The changes of organic C, N and K in decay remainders were different. The content of organic C almost did not change during the whole decay time. The content of nitrogen increased in 7-12months gradually, and then kept steady. The content of K decreased slowly in 0-1months and decreased quickly in 6-8months, and then kept steady.4. Under the different vegetation type, the content of soil organic acid was basically in the order of Tree bush≈herb >farmland abandoned land. Therefore, it can be seen that the content of soil organic acids were increased gradually along with the enhancement of vegetational succession stage.5. Oxalic acid, Tartaric acid, Malic acid, Acetic acid were detected in corn and corn+N . In Spodiopogon sibiricus and Spodiopogon sibiricus+N we detected oxalic acid, malic acid, acetic acid. In alfalfa we only detected three of them: oxalic acid, malic acid, acetic acid. Oxalic acid, malic acid, acetic acid, criric acids were detected in Hippophae rhamnoides. In Quercus liaotungensis, all of the organic acids were detected by HPLC.Oxalic acid in decomposition, all of the remainders have a growth trend. Malic acid in the process of decomposition, with the decomposition of the extension of time, the content gradually reduced, this is because Malic acid is easy for microbial use, Acetic acid content accumulate less of the decomposition extend. Tartaric acid during decomposition is less and less in corn and corn+N,while it is accumulated in Quercus liaotungensis...