|Blumenthal, Dana - UNIVERSITY OF MINNESOTA|
|Jordan, Nicholas - UNIVERSITY OF MINNESOTA|
Submitted to: Ecological Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 2002
Publication Date: June 1, 2003
Citation: Blumenthal, D.M., Jordan, N.R., Russelle, M.P. 2003. Soil carbon addition controls weeds and facilitates prairie restoration. Ecological Applications. 13(3):605-615. Interpretive Summary: There is growing interest in re-establishing native vegetation in many areas of the USA, but it has proven very difficult to establish prairie plantings on former agricultural land. Part of the problem arises due to extreme competition between fast-growing weeds and slow-growing prairie seedlings. Previous research has shown that high nitrate supply supports growth of many weedy species. An effective approach to reducing nitrate supply is needed to improve the success of prairie restoration. We found that nitrate supply was only 14% as large when high applications of sawdust and wood chips were made to the soil before planting. These woody materials contain very little nitrogen, so soil microorganisms absorb the available soil nitrogen as they decompose the sawdust and chips. At the highest rate of wood chip and sawdust application, the weight of weed species declined by one-half, while prairie plant seedlings were seven times larger than on unamended soil. Our results provide another tool that land managers can us to re-establish native prairie vegetation. In addition, the application of these materials to soil will help sequester carbon in soil organic matter, thereby improving soil quality and reducing global warming.
Technical Abstract: Soil nitrogen enrichment, and consequent vigorous weed growth, is thought to hinder the restoration of tallgrass prairie. Adding carbon to the soil may facilitate prairie restoration by inducing immobilization of plant- available nitrogen. Early attempts to use this method, however, have had mixed results. Success of C addition depends on three conditions: weeds must suppress prairie species in the absence of C addition, weeds must be nitrophilic relative to prairie species, and C addition must result in a large enough decrease in N to alter the balance of competition among weeds and prairie species. We examined these conditions by comparing productivity of 10 weeds and 10 tallgrass prairie species under 14 levels of C addition, ranging from 84 to 3346 g C/m2. Carbon was tilled into the soil prior to planting. To control for non-N effects of C addition, N was added to a subset of plots. Relative to untreated plots, the highest level of C addition resulted in an 86% decrease in available nitrate-N, a 14-fold increase in early-season light availability, a 54% decrease in weed biomass, and a 7-fold increase in prairie biomass. Nitrogen addition significantly reduced or reversed all of these effects. Significant species-specific responses to C addition included decreased biomass for six annual weeds and increased biomass for six prairie species, one annual weed, and three perennial weeds. These results suggest that C addition may be a useful tool for restoring N-limited plant communities.