Shrub encroachment in North American grasslands: Shifts in growth form dominance rapidly alters control of ecosystem carbon inputs

TitleShrub encroachment in North American grasslands: Shifts in growth form dominance rapidly alters control of ecosystem carbon inputs
Publication TypeJournal Article
Year of Publication2008
AuthorsKnapp A.K., Briggs J.M, Collins S.L., Archer SR, Bret-Harte M.S., Ewers B., Peters DC, Young D., Shaver G., Cleary M.B.
JournalGlobal Change Biology
Volume14
Pagination615-623
Date PublishedJanuary 30, 2008
Accession NumberJRN00513
ARIS Log Number215068
Keywordsaboveground net primary production, carbon, climate change, encroachment, grass-dominated biomes, grasslands, growth form, LAI, MAP, North American, shrub, shrublands
Abstract

Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a 4-fold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (>1000 g/m2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently, the relationship between MAP and ANPP shifted from being non-linear in grasslands to linear in shrublands. Thus, relatively abrupt (<50 yrs) shifts in growth form dominance, without changes in resource quantity, can fundamentally alter continental-scale pattern of C inputs and control by MAP in ways that exceed the direct effects of climate change alone.

URL/files/bibliography/08-005.pdf
DOI10.1111/j.1365-2486.2007.01512.x