01892nas a2200241   4500008004100000245013500041210006900176300001300245490000700258520110800265100002001373700001901393700002401412700001701436700002101453700001601474700001701490700001601507700001701523700001601540700001701556856007701573       2008                        eng d00aShrub encroachment in North American grasslands: Shifts in growth form dominance rapidly alters control of ecosystem carbon inputs0 aShrub encroachment in North American grasslands Shifts in growth  a615 -6230 v143 a<p>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 fourfold 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 (&gt;1000 g m&minus;2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently, the relationship between MAP and ANPP shifted from being nonlinear in grasslands to linear in shrublands. Thus, relatively abrupt (&lt;50 years) shifts in growth form dominance, without changes in resource quantity, can fundamentally alter continental-scale pattern of C inputs and their control by MAP in ways that exceed the direct effects of climate change alone.</p>1 aKnapp, Alan, K.1 aBriggs, J., M.1 aCollins, Scott., L.1 aArcher, S.R.1 aBret-Harte, M.S.1 aEwers, B.E.1 aPeters, D.P.1 aYoung, D.R.1 aShaver, G.R.1 aPendall, E.1 aCleary, M.B.  uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2007.01512.x