, Volume 11, Issue 3, pp 454–468 | Cite as

Woody Plant Encroachment by Juniperus virginiana in a Mesic Native Grassland Promotes Rapid Carbon and Nitrogen Accrual

  • Duncan C. McKinleyEmail author
  • John M. Blair


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.


Juniperusvirginiana woody plant encroachment grassland conversion invasion nitrogen cycling nitrogen use efficiency mineralization carbon storage land cover change 



We gratefully acknowledge support from NASA’s Land Cover Land Use Change program, as well as a student fellowship from the NASA Kansas Space Grant program, and additional support from the Division of Biology at Kansas State University and the Konza Prairie Long-Term Ecological Research program. We would like to thank Jesse Nippert and Alan Knapp for advice on plant physiological measurements. We also thank Amy Austin and two anonymous reviewers whose constructive comments improved upon an earlier draft of the manuscript. This is publication 08-291-J from the Kansas Agricultural Experiment Station.


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Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  1. 1.Smithsonian Environmental Research CenterEdgewaterUSA
  2. 2.Division of BiologyKansas State UniversityManhattanUSA

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