Nutrient Dynamics of Herbaceous Vegetation in Upland and Floodplain Forest Communities

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Abstract
The role of of herbaceous vegetation in the nutrient cycling regimes of adjacent upland (oak-hickory) and floodplain (silver maple) forests was studied at Robert Allerton Park in east-centrol Illinois [USA]. Net annual production of the upland spring ephemeral group was 68.5 g/m2 and was dominated by Claytonia virginica and Dicentra cucullaria; production by the summer herb group was 24.5 g/m2 and was dominated by Impatiens pallida. Net production by all floodplain herbs was 88.8 g/m2 and was affected by a summer flood which induced early senescence in some species. Net uptake of N, P and K by upland spring ephemerals was 10.6, 1.6 and 18.9 kg/ha, respectively, and by summer herbs, 6.3, 0.84 and 15.1 kg/ha, respectively. Uptake of these elements by floodplain herbs was 16.6, 3.6 and 20.3 kg/ha, respectively. Relative to annual losses in streamflow, uptake of N, P and K by upland herbaceous vegetation is substantial, and temporary storage of elements by spring ephemerals reduces nutrient loss from soils during a period of high potential leaching. The nutrient dynamics of floodplain forests are probably more strongly affected by annual flooding patterns and sedimentation than by herbaceous nutrient uptake. In general, the rapid decomposition of herbaceous litter provides a source of nutrients whose availability for plant uptake is intermediate to that of aqueous inputs and litter from overstory species.