59 Decomposition rates of shrub leaves compared to grass clippings in a tallgrass prairie

Tuesday, August 4, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Alexander J. Lyon , Biological Science, Emporia State University, Emporia, KS
Brenda A. Koerner , Department of Biological Sciences, Emporia State University, Emporia, KS
Background/Question/Methods

The suppression of fire has lead to an increase in density and cover of C3 shrubs within tallgrass prairies of the central United States. The morphological differences between shrubs and grasses alter the process by which aboveground C is released into the soil system. The rate of decomposition of leaf litter by soil microbes affects the amount of C that enters the belowground soil system. As microbial decomposition increases the amount of C entering the soil system decreases because the microbes release the C into the atmosphere. The goal of this study was to determine the decomposition rates of shrub leaves and grass clippings in both environments. I examined the decomposition rate of shrub leaves and grass clippings on the Ross Natural History Reservation, Americus, KS, USA.           

Shrub leaves and grass clippings were collected in November 2008 and were placed into a 2mm mesh bag. Approximately 30 grams of the respective litter were placed in each bag. A sub-sample of five shrub bags and five grass bags were dried at 55˚C for 24 hours to determine moisture content. The bags will be removed at three month intervals. Both shrub litter and grass litter were placed in both patch type to evaluate the different microclimate effects on decomposition rates. As bags were removed from the field they were dried at 55˚C for 24 hours and then weighed to determine the decomposition loss.  

Results/Conclusions

Soil microbes are able to decompose shrub leaves at a faster rate than they are able to decompose grass clippings. This is because grass clippings contain more lignin, which is resistant to most microbial decomposition, than shrub leaves containing less lignin. The C that is contained in shrub leaves is then released into the atmosphere at a faster rate than grass clippings. Therefore, less C is able to enter the soil system under shrubs leaves than compared to grass clippings. As shrub expansion continues into tallgrass prairies, less C will be stored by soils and more C will be released into the atmosphere.

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