Sediment and Nutrient Accumulation in Floodplain and Depressional Cypress-gum Forest Soils of Southwestern Georgia
Craft, Christopher B.
Casey, William P.
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Historical (125 yr, ²¹⁰Pb) and recent (30 yr, ¹³⁷Cs) rates of sediment and nutrient (C, N, P) accumulation were measured in open (floodplain) and closed ( depressional) cypress-gum wetland soils to evaluate the effects of changing land use on nutrient, carbon and sediment retention. Over the past 125 yr, rates of sediment (1420 g/m²/yr ), C (78 g/m²/yr ), N (6.1 g/m²/yr ) and P (0.58 g/m²/yr ) accumulation were two to ten times higher in the floodplain forests as compared to the depressional wetlands (144 g sediment /m²/yr, 46 g C/m²/yr , 3.2 g N/m²/yr , 0.22 g P/m²/yr ). In the depressional wetlands, there was no difference in sediment and nutrient accumulation during the past 30 years versus the past 125 years. However, in the floodplain forests, sediment and nutrient accumulation during the past 100 years were five to ten times higher as compared to the past 30 years. Higher historical rates of sediment, C, N and P accumulation in the floodplain forests probably reflect widespread land clearing for agriculture and grazing in southwestern Georgia during the late 19th and early 20th century.