Wednesday, November 15, 2006 - 11:45 AM
296-7
SOM and Microbial Changes Following Planting of Cedar and Pine Plantations on Sandy Native Prairie.
Afforestation of agricultural soils is providing soil C sequestration of atmospheric CO2 in both the plant biomass and soil. Tree growth on prairies can also sequester C. Its other effects such as those on the soil profile, microorganisms and nutrient cycling are not well established. The Nebraska National Forest at Halsey was sampled to explore the effects on amounts and distribution of SOM and associated microorganisms under cedars and pines planted on native sandy prairie approximately 100 years ago. Cedar soils had more soil C in the top 5cm than the prairie, which is attributed to large input of fine roots and litter and possibly Ca movement from lower soil layers. Pine stands contained the largest amount of litter C. This sink for ecosystem C is of unknown duration. Pine stands contained the least amount of total soil C and had a more negative d13C suggesting that pine soils are degrading prairie C faster than cedar soils. This data is supported by d13C values for soil and CO2 evolved during incubation. A drift of approximately 2‰ more negative was seen in the d13C-CO2 during extended incubation of the prairie soil without a known change in species composition. This was attributed to degradation of more aromatic-lignin-like compounds later in the incubation. Cedar soils contained larger amounts of soil Ca especially in the top 5cm. A positive correlation between Ca and soil C storage was found and its ecosystem effects are being investigated. Our research suggests changes in soil C and nutrient content following land conversion from prairie to forest are dependent on the species planted. Overall, if ecosystems are to be used as sinks for atmospheric C, then we must know the relative impacts of different management strategies on soil C pools and microbial populations to prescribe the best management options.
Recorded presentation