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in organic matter content from 7,196 kg/ha to 2,632 kg/ha after <br />32 years and- available nitrogen dropped from 399 kg/ha to 154 <br />kg/ha. These data suggest that even though much of the basin is <br />now cropped, sufficient organic matter remains to contribute <br />significantly should we find the mechanism to introduce it to the <br />river. <br />In wetlands, where complete-decomposition of above and <br />belowground materials occurs in one year, annual root biomass may <br />be ane-fourth to one times the shoot biomass (Richardson 1978, <br />Klopatek and Stearns 1976). The high moisture content and <br />relatively poor aeration characteristics of wetland soils leads <br />to the accumulation of high organic matter content. <br />Forest soils on the other hand have much less organic matter. <br />The belowground biomass of forest species is only nine percent of <br />aboveground biomass (Ovington et al. 1963).. Tree roots are <br />longer lived and therefore convert to humus more slowly. In <br />addition, leaf litter in forest conditions reaches the humus <br />stage more slowly. Hence, a river which would erode these soils <br />would receive a smaller contribution of organic carbon. <br />The Missouri River Floodplain <br />Plant Community, Past and Present. <br />- 7 - <br />