Organic Acids In Forest Litters And Their Effect On Phosphorus Release Of Dark Brown Forest Soil

Based on the main kinds on trees in the north part of China, such as Larch(Larix dahurica), Manchurian(Fraxinus mandshurica), Korean pine(Pinus koraiensis) and White birch(Betula platyphylla), and Dark Brown Forest Soil which is a maximum zonal soil in area, quantitative and qualitative analysis of organic acids in the four kinds of trees' L litters and more decomposed F litters were done by Gas Chromatogram system. At the same time, the effect of insoluble Phosphorus nutrient on Dark Brown Forest Soil caused by Oxalic acid presenting in all litters dominantly was studied.The results are as follows:First, The method used in this paper to separate and identify organic acids in the forest litters by Gas Chromatogram (GC) system is a reliable and convenient method. The Recoveries of thirteen organic acids detected ranged from 74.66% to 87.45% with Coefficient Variation from 1.53% to 8.54%. These data showed that the method accorded with the analyzing demand.Second, Organic acids were present in the forest litters comprehensively. As to L litters of all samples, Oxalic acid was maximum in the seven Low-molecular-weight organic acids and its amounts always were above 30mg/g, and Oleic acid or Linoleic acid was maximum in six fatty acids, above 40mg/g. To F litters, Oxalic acid was maximum, next is Linoleic acid and oleic acid respectively in all the organic acids detected. As for the same kinds of tree, amounts of organic acids in L litters were obviously higher than those in F litters.Third, Oxalic acid could obviously contribute to phosphorus release in Dark Brown Forest Soil A1 horizon, and amounts of phosphorus release rose with the rising of concentrations of Oxalic acid. What's more, amounts of phosphorus release caused by Oxalic acid in B horizon were lower distinctly than those in A1 horizon. As to Dark Brown Forest Soil, the percent of phosphorus activation caused by Oxalic acid anion were higher than the effect of solving of acid.Forth, Activation of phosphorus caused by organic acid could be added up. Amounts of phosphorus release were decided by Loading Amounts of Oxalic acid dominantly, and didn't have much something to do with adding patterns of Oxalic acid. Regression equation of amounts of phosphorus release (y) and Oxalic acid Loading (x) was y = -0.0008x2 + 0.2125x, and Correlation coefficient was 0.9919.Fifth, based on the Regression equation mentioned above, amounts of phosphorus release caused by Oxalic acid in L and F litters were estimated, its quantity was about 2.085 kg/ hm2.yr and accounted for one in third to one in four in the amounts of phosphorus adsorbed by mid-aged or mature forests in a year.