02695nas a2200241   4500008004100000245012400041210006900165300001300234490000700247520189300254653001902147653002502166653001302191653002502204653002202229653001902251653002102270653002802291653002902319100001902348700002002367856006602387       2008                        eng d00aWoody plant encroachment by Juniperus virginiana in a mesic native grassland promotes rapid carbon and nitrogen accrual0 aWoody plant encroachment by Juniperus virginiana in a mesic nati  a454 -4680 v113 a<p>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.</p>10acarbon storage10agrassland conversion10ainvasion10aJuniperus virginiana10aland cover change10aMineralization10aNitrogen cycling10aNitrogen use efficiency10awoody plant encroachment1 aMcKinley, D.C.1 aBlair, John, M.  uhttps://link.springer.com/article/10.1007%2Fs10021-008-9133-4