Document: CHR-3-59-13

Assessing the impact of prairie restoration and agricultural land use on soil carbon dynamics in southern Wisconsin.

KUCHARIK, C.J.*

University of Wisconsin-Madison, Madison, WI 53706, USA ¹

Abstract:
Data collected from 1995-2000 within southern Wisconsin agroecosystems show that different land management practices (tillage and fertilization), and ecosystem type (prairie versus corn) have profound influence on soil C dynamics. Total soil C and N data were obtained (to 1 m depth) in 4 remnant and 5 restored prairies, and several corn agroecosystems to provide an improved understanding of the effects of agriculture and prairie restoration on soil C changes across this region. Soil C density measurements were obtained within four varied corn treatments (tillage/no-tillage; fertilized/unfertilized) at the UW-Madison Agricultural Research Station near Arlington (45 km N of Madison; plano silt loam). The data depict that all corn plots contain 40-60% of the native soil C content estimated for this region. The no-tillage corn plots contain more carbon than chisel-plow treatments, as do the fertilized plots, which are adding 1.6 times more residue back to the soil each year compared to the unfertilized treatments. The remnant prairie ecosystems contain 20-80% more soil C than restored prairies (which range in age from 2-65 years). Of particular interest is data collected within a 24-yr old restored prairie (located 2.5 km from the Arlington corn plots on the same soil type). This ecosystem currently contains 20% and 40% less soil C than the unfertilized and fertilized corn agroecosystems, respectively. Moreover, based on a time series of measurements from 1996-2000, the Arlington prairie lost an additional 20% of its soil C content. Moreover, its current carbon density is the lowest measured among all the ecosystems we studied. These data suggest that the restoration of this prairie has done little to replenish its soil C content over the past two decades, while the corn agroecosystems are possibly sequestering atmospheric C. The reasoning for the prairie's additional release of carbon is unclear at this point; however, a nitrogen deficiency might be one possible hypothesis, as evident from N-min data. This poses an important question of whether or not current methods of prairie restoration, which are highly correlated to aesthetics and rehabilitating the aboveground biodiversity, are beneficial to the soil fertility while helping to mitigate the greenhouse effect.

Keywords: prairie restoration, carbon cycling, agroecosystems

This abstract is being presented at: 1:30 PM in session:
Oral Session #31: Agroecology.