Title | Woody plant encroachment by Juniperus virginiana in a mesic native grassland promotes rapid carbon and nitrogen accrual |
Publication Type | Journal Article |
Year of Publication | 2008 |
Authors | McKinley, DC, Blair, JM |
Journal | Ecosystems |
Volume | 11 |
Pagination | 454 -468 |
Accession Number | KNZ001175 |
Keywords | carbon storage, grassland conversion, invasion, Juniperus virginiana, land cover change, Mineralization, Nitrogen cycling, Nitrogen use efficiency, woody plant encroachment |
Abstract | The cover and abundance of Juniperus virginiana L. in the U.S. Central Plains are rapidly increasing, largely as a result of changing land-use practices that alter fire regimes in native grassland communities. Little is known about how conversion of native grasslands to Juniperus-dominated forests alters soil nutrient availability and ecosystem storage of carbon (C) and nitrogen (N), although such land-cover changes have important implications for local ecosystem dynamics, as well as regional C and N budgets. Four replicate native grasslands and adjacent areas of recent J. virginiana encroachment were selected to assess potential changes in soil N availability, leaf-level photosynthesis, and major ecosystem C and N pools. Net N mineralization rates were assessed in situ over two years, and changes in labile soil organic pools (potential C and N mineralization rates and microbial biomass C and N) were determined. Photosynthetic nitrogen use efficiencies (PNUE) were used to examine differences in instantaneous leaf-level N use in C uptake. Comparisons of ecosystem C and N stocks revealed significant C and N accrual in both plant biomass and soils in these newly established forests, without changes in labile soil N pools. There were few differences in monthly in situ net N mineralization rates, although cumulative annual net N mineralization was greater in forest soils compared to grasslands. Conversely, potential C mineralization was significantly reduced in forest soils. Encroachment by J. virginiana into grasslands results in rapid accretion of ecosystem C and N in plant and soil pools with little apparent change in N availability. Widespread increases in the cover of woody plants, like J. virginiana, in areas formerly dominated by graminoid species suggest an increasing role of expanding woodlands and forests as regional C sinks in the central U.S. |
URL | https://link.springer.com/article/10.1007%2Fs10021-008-9133-4 |
DOI | 10.1007/s10021-008-9133-4 |