Species diversity, primary production, decomposition, and soil carbon sequestration in a restored prairie, a cool-season grass pasture, and an old field

Background/Question/Methods

Restoration of prairies has been advocated by many for numerous reasons such as recovery of biological diversity and ecosystem functions.  We investigated measures of ecosystem function in a prairie, located in Taltree Arboretum, Valparaiso, IN, that was restored in 1998.  To do this, we hypothesized that the restoration of prairie would promote the species diversity and richness of native species and thus capacity for carbon sequestration by its vegetation and soil.  We tested this hypothesis by comparing the primary production, decomposition rate of organic matter, and concentration of soil carbon in the restored prairie plots (n=10) with the ones in a nearby pasture (n=10) that was established by seeding of cool-season grass species and an old field (n=10) where a secondary succession has been underway since abandonment of farming in 1998.  The primary production was determined by harvesting and measuring above- and belowground biomass.  The concentration of organic matter was determined by loss of soil weight on ignition at 450^oC for 4 hours.  The decomposition rate was measured by loss of organic matter mass in mesh-bags in the field plots during May-September, 2012. 

Results/Conclusions

The species richness was highest in the restored prairie (47 species) and followed by the cool-season pasture (39 species) and the old field (21 species), and the species diversity was highest in the pasture (H'=2.65) and followed by the prairie (H'=2.39) and the old field (H'=1.50).  This higher H' of the pasture was most likely due to establishment of native plant species, in addition to the existing cool-season grass species, from the adjacent restored prairie.   Biomass production was higher in the old field (8.6+1.1 Kg m^-2) than the prairie (6.0+0.5 Kg) and the pasture (6.0+1.1 Kg), although the difference was marginally significant (p=0.097).   Decomposition was also higher in the old field (29.0+1.7%) than the prairie (15.9+1.5 %) and the pasture (22.7+2.6%).  Soil organic matter was lower in the prairie (3.9+0.7%) than the pasture (4.8+0.7%) and the old field (5.0+0.6%).  Our results suggest that the restored prairie has not reached to the same level of old field for sequestration of atmospheric carbon by both vegetation and soil.  Also, we did not find the evidence that supports the hypothesis “promoted primary production and carbon sequestration by vegetation of higher species richness or diversity” at this time.