Evidence of physiological decoupling from grassland ecosystem drivers by an encroaching woody shrub

dc.citation.doidoi:10.1371/journal.pone.0081630en_US
dc.citation.issue12en_US
dc.citation.jtitlePLoS ONEen_US
dc.citation.spagee81630en_US
dc.citation.volume8en_US
dc.contributor.authorNippert, Jesse B.
dc.contributor.authorOcheltree, Troy W.
dc.contributor.authorOrozco, Graciela L.
dc.contributor.authorRatajczak, Zakary J.
dc.contributor.authorLing, Bohua
dc.contributor.authorSkibbe, Adam M.
dc.contributor.authoreidnipperten_US
dc.date.accessioned2014-03-05T22:26:47Z
dc.date.available2014-03-05T22:26:47Z
dc.date.issued2014-03-05
dc.date.published2013en_US
dc.description.abstractShrub encroachment of grasslands is a transformative ecological process by which native woody species increase in cover and frequency and replace the herbaceous community. Mechanisms of encroachment are typically assessed using temporal data or experimental manipulations, with few large spatial assessments of shrub physiology. In a mesic grassland in North America, we measured inter- and intra-annual variability in leaf δ¹³C in Cornus drummondii across a grassland landscape with varying fire frequency, presence of large grazers and topographic variability. This assessment of changes in individual shrub physiology is the largest spatial and temporal assessment recorded to date. Despite a doubling of annual rainfall (in 2008 versus 2011), leaf δ¹³C was statistically similar among and within years from 2008-11 (range of −28 to −27‰). A topography*grazing interaction was present, with higher leaf δ¹³C in locations that typically have more bare soil and higher sensible heat in the growing season (upland topographic positions and grazed grasslands). Leaf δ¹³C from slopes varied among grazing contrasts, with upland and slope leaf δ¹³C more similar in ungrazed locations, while slopes and lowlands were more similar in grazed locations. In 2011, canopy greenness (normalized difference vegetation index – NDVI) was assessed at the centroid of individual shrubs using high-resolution hyperspectral imagery. Canopy greenness was highest mid-summer, likely reflecting temporal periods when C assimilation rates were highest. Similar to patterns seen in leaf δ¹³C, NDVI was highest in locations that typically experience lowest sensible heat (lowlands and ungrazed). The ability of Cornus drummondii to decouple leaf physiological responses from climate variability and fire frequency is a likely contributor to the increase in cover and frequency of this shrub species in mesic grassland and may be generalizable to other grasslands undergoing woody encroachment.en_US
dc.identifier.urihttp://hdl.handle.net/2097/17205
dc.language.isoen_USen_US
dc.relation.urihttp://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0081630en_US
dc.subjectGrasslanden_US
dc.subjectShrub encroachmenten_US
dc.subjectCornus drummondiien_US
dc.titleEvidence of physiological decoupling from grassland ecosystem drivers by an encroaching woody shruben_US
dc.typeArticle (publisher version)en_US

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