01977nas a2200265 4500008004100000245015800041210006900199300001500268490000700283520111400290100002001404700002001424700001601444700001501460700001701475700001801492700001901510700001801529700001601547700001701563700001901580700001901599700001601618856007701634 2012 eng d00aThe effect of experimental warming and precipitation change on proteolytic enzyme activity: positive feedbacks to nitrogen availability are not universal0 aeffect of experimental warming and precipitation change on prote a2617 -26250 v183 a
Nitrogen regulates the Earth's climate system by constraining the terrestrial sink for atmospheric CO2. Proteolytic enzymes are a principal driver of the within-system cycle of soil nitrogen, yet there is little to no understanding of their response to climate change. Here, we use a single methodology to investigate potential proteolytic enzyme activity in soils from 16 global change experiments. We show that regardless of geographical location or experimental manipulation (i.e., temperature, precipitation, or both), all sites plotted along a single line relating the response ratio of potential proteolytic activity to soil moisture deficit, the difference between precipitation and evapotranspiration. In particular, warming and reductions in precipitation stimulated potential proteolytic activity in mesic sites – temperate and boreal forests, arctic tundra – whereas these manipulations suppressed potential activity in dry grasslands. This study provides a foundation for a simple representation of the impacts of climate change on a central component of the nitrogen cycle.
1 aBrozostek, E.R.1 aBlair, John, M.1 aDukes, J.S.1 aFrey, S.D.1 aHobbie, S.E.1 aMelillo, J.M.1 aMitchell, R.J.1 aPendall, E.S.1 aReich, P.B.1 aShaver, G.R.1 aStefanskii, A.1 aTjoelker, M.G.1 aFinzi, A.C. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2012.02685.x02050nas a2200313 4500008004100000245008100041210006900122300001300191490000700204520112700211653001901338653001801357653002301375653001701398653002801415100002001443700001601463700001701479700002401496700001601520700001901536700001701555700002801572700001801600700001901618700001701637700001801654856006401672 2012 eng d00aPast, present, and future roles of long-term experiments in the LTER Network0 aPast present and future roles of longterm experiments in the LTE a377 -3890 v623 aThe US National Science Foundation–funded Long Term Ecological Research (LTER) Network supports a large (around 240) and diverse portfolio of long-term ecological experiments. Collectively, these long-term experiments have (a) provided unique insights into ecological patterns and processes, although such insight often became apparent only after many years of study; (b) influenced management and policy decisions; and (c) evolved into research platforms supporting studies and involving investigators who were not part of the original design. Furthermore, this suite of long-term experiments addresses, at the site level, all of the US National Research Council's Grand Challenges in Environmental Sciences. Despite these contributions, we argue that the scale and scope of global environmental change requires a more-coordinated multisite approach to long-term experiments. Ideally, such an approach would include a network of spatially extensive multifactor experiments, designed in collaboration with ecological modelers that would build on and extend the unique context provided by the LTER Network.
10aClimate change10aglobal change10along-term research10aLTER Network10amultifactor experiments1 aKnapp, Alan, K.1 aSmith, M.D.1 aHobbie, S.E.1 aCollins, Scott., L.1 aFahey, T.J.1 aHansen, G.J.A.1 aLandis, D.A.1 aLa Pierre, Kimberly, J.1 aMelillo, J.M.1 aSeastedt, T.R.1 aShaver, G.R.1 aWebster, J.R. uhttps://academic.oup.com/bioscience/article/62/4/377/24376201892nas 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 aShrub 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 (>1000 g m−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 (<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.
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