Morris, S.J., S. Bohm, K. Paustian, E.T. Elliott, and E.A. Paul
Presented at the All Scientist Meeting (1999-07-20 to 1999-07-21 )
Disturbance to terrestrial ecosystems as a consequence of agriculture, deforestation, and land degradation over the last century has resulted in a net loss of soil C. Native forest soils contain 25 to 50% more C than associated agricultural sites. Increased C storage capacity in afforested agricultural land has the potential to mitigate increases in atmospheric CO2 resulting from anthropogenic sources. We evaluated C dynamics of afforested, native and agricultural areas of known history on similar soil types at the Fred Russ Forest managed by Kellogg Biological Station (KBS), Newton Woods and associated agricultural land in southern Michigan. A three pool constrained model was utilized to examine turnover rates of soil C pools to determine whether soil C sequestration resulting from afforestation of agricultural lands can contribute to changes in global C cycles.Our results from Russ Forest show significant differences in total C and N in the B horizon, and C horizon for the Afforested and Agricultural soils. Differences in bulk density and horizon depth necessitate corrections within treatments so that profiles are compared on the basis of equal soil weight. Total profile C and N corrected for equal soil weight also differed significantly among afforested, agricultural, and native soils. Results from long-term incubations showed differences in C dynamics among the three land types. A two pool constrained model constructed using the rate curve from CO2 evolution during incubations resulted in a larger Ca pool in the top 20 cm of soil for the Agricultural soils (302 mg/kg soil-4.3 % of total C) than the Afforested soils (261 mg/kg soil-1.25 of total C).These results have a number of implications for global change. The Russ Forest has large quantities of C stored in biomass, litter and soils. The afforested biomass and soil currently contain an estimated 122 Mg C/ha and 7.6 Mg N/ha while the comparable agricultural sites contain 56 Mg C/ha and 5.4 Mg N/ha. This represents an increase in C storage in the afforested site of approximately 66 Mg C/ha and 2.2 Mg N/ha since the forest was planted in the mid forties Additionally, afforested soils are sequestering soil C in pools with longer MRT’s. Additional studies on the effects of afforestation on C sequestration will include sites from the KBS-Long Term Ecological Research Station poplar plots, deciduous and coniferous forest plots, and associated agricultural plots.
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