00605nas a2200157   4500008004100000245009100041210006900132260002400201300001300225100001900238700001700257700001800274700002000292700002000312856011500332       2008                        eng d00aBiogeochemical changes associated with Juniperus virginia encroachment into grasslands0 aBiogeochemical changes associated with Juniperus virginia encroa  bSpringer-Verlag, NY  a170 -1871 aMcKinley, D.C.1 aNorris, M.D.1 aJohnson, L.C.1 aBlair, John, M.1 aVan Auken, O.W.  uhttp://lter.konza.ksu.edu/content/biogeochemical-changes-associated-juniperus-virginia-encroachment-grasslands02839nas a2200265   4500008004100000245010400041210006900145300001500214490000700229520201100236653001802247653002402265653001402289653002102303653001402324653002202338653001902360653001802379653002102397653001202418100001902430700001702449700002002466856008702486       2008                        eng d00aConversion of grassland to coniferous woodland has limited effects on soil nitrogen cycle processes0 aConversion of grassland to coniferous woodland has limited effec  a2627 -26330 v403 a<p>In the last century, conversion of native North American grasslands to Juniperus virginiana forests or woodlands has dramatically altered ecosystem structure and significantly increased ecosystem carbon (C) stocks. We compared soils under recently established J. virginiana forests and adjacent native C4-dominated grassland to assess changes in potential soil nitrogen (N) transformations and plant available N. Over a 2-year period, concentrations of extractable inorganic N were measured in soils from forest and grassland sites. Potential gross N ammonification, nitrification, and consumption rates were determined using 15N isotope-dilution under laboratory conditions, controlling for soil temperature and moisture content. Potential nitrification rates (Vmax) and microbial biomass, as well as soil physical and chemical properties were also assessed. Extractable NH4+ concentrations were significantly greater in grassland soils across the study period (P &le; 0.01), but analysis by date indicated that differences in extractable inorganic N occurred more frequently in fall and winter, when grasses were senescent but J. virginiana was still active. Laboratory-based rates of gross N mineralization (ammonification) and nitrification were greater in grassland soils (P &le; 0.05), but only on one of four dates. Potential nitrification rates (Vmax) were an order of magnitude greater than gross nitrification rates in both ecosystems, suggesting that nitrification is highly constrained by NH4+ availability. Differences in plant uptake of N, C inputs, and soil microclimate as forests replace grasslands may influence plant available N in the field, as evidenced by seasonal differences in soil extractable NH4+, and total soil C and N accumulation. However, we found few differences in potential soil N transformations under laboratory conditions, suggesting that this grassland-to-forest conversion caused little change in mineralizable organic N pools or potential microbial activity.</p>10aExtractable N10aForest encroachment10agrassland10aIsotope dilution10aJuniperus10aMicrobial biomass10aMineralization10anitrification10aNitrogen cycling10aprairie1 aMcKinley, D.C.1 aRice, C., W.1 aBlair, John, M.  uhttps://www.sciencedirect.com/science/article/abs/pii/S0038071708002320?via%3Dihub02695nas 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%2Fs10021-008-9133-400503nas a2200121   4500008004100000245012600041210006900167260004300236300001100279490002100290100001900311856005100330       2007                        eng d00aConsequences of conversion of native Mesic grassland to coniferous forest on soil processes and ecosystem C and N storage0 aConsequences of conversion of native Mesic grassland to conifero  aManhattan, KSbKansas State University  a1 -2000 vPhD Dissertation1 aMcKinley, D.C.  uhttp://krex.k-state.edu/dspace/handle/2097/253