02231nas a2200349   4500008004100000245008200041210006900123300001300192490000700205520128800212653001901500653001201519653001501531653001801546653001501564100002001579700001401599700001701613700001801630700001201648700001901660700001601679700001601695700001501711700001401726700001801740700001701758700001501775700001401790700001301804856006401817       2008                        eng d00aConsequences of more extreme precipitation regimes for terrestrial ecosystems0 aConsequences of more extreme precipitation regimes for terrestri  a811 -8210 v583 a<p>mplification of the hydrological cycle as a consequence of global warming is forecast to lead to more extreme intra-annual precipitation regimes characterized by larger rainfall events and longer intervals between events. We present a conceptual framework, based on past investigations and ecological theory, for predicting the consequences of this underappreciated aspect of climate change. We consider a broad range of terrestrial ecosystems that vary in their overall water balance. More extreme rainfall regimes are expected to increase the duration and severity of soil water stress in mesic ecosystems as intervals between rainfall events increase. In contrast, xeric ecosystems may exhibit the opposite response to extreme events. Larger but less frequent rainfall events may result in proportional reductions in evaporative losses in xeric systems, and thus may lead to greater soil water availability. Hydric (wetland) ecosystems are predicted to experience reduced periods of anoxia in response to prolonged intervals between rainfall events. Understanding these contingent effects of ecosystem water balance is necessary for predicting how more extreme precipitation regimes will modify ecosystem processes and alter interactions with related global change drivers.</p>10aClimate change10aDrought10aEcosystems10aPrecipitation10asoil water1 aKnapp, Alan, K.1 aBeier, C.1 aBriske, D.D.1 aClassen, A.T.1 aLuo, Y.1 aReichstein, M.1 aSmith, M.D.1 aSmith, S.D.1 aBell, J.E.1 aFay, P.A.1 aHeisler, J.L.1 aLeavitt, S.W1 aSherry, R.1 aSmith, B.1 aWeng, E.  uhttps://academic.oup.com/bioscience/article/58/9/811/25085302809nas a2200205   4500008004100000245012800041210006900169300001300238490000800251520205600259653001202315653002502327653002602352653002102378653002302399653002202422100001702444700001702461856012502478       2001                        eng d00aBelow-ground carbon and nitrogen accumulation in perennial grasses: A comparison of caespitose and rhizomatous growth forms0 aBelowground carbon and nitrogen accumulation in perennial grasse  a117 -1270 v2373 aAn experiment was conducted to compare below-ground soil organic carbon and total nitrogen accumulation between caespitose and rhizomatous perennial grasses in long-term (<25 yrs) grazed and ungrazed sites in semi-arid and mesic communities in the North American Great Plains. Development of greater nutrient pools beneath than between clones occurred at minimal clone basal areas (<60 cm2) for both caespitose species. Caespitose grasses accumulated substantially greater pools of carbon (20–200 fold) and nitrogen (50–500 fold) in soils to a depth of 10 cm beneath clones than rhizomatous grasses accumulated in rhizomes in both communities. Carbon and nitrogen pools in soils beneath caespitose clones exceeded combined (soil + rhizome) pools for rhizomatous grasses for a majority of the clone basal areas (>90 cm2) in the mesic community. In contrast, both pool sizes were smaller beneath the caespitose grass at all clone basal areas than the combined pools for the rhizomatous grass in the semi-arid community. The occurrence of larger soil nutrient pools beneath the rhizomatous species in the semi-arid community was largely a consequence of niche separation for microsites characterized by soils with higher nutrient concentrations, rather than plant-induced increases in nutrient concentrations. Although nutrient islands do not occur beneath rhizomatous grasses, their distribution in the semi-arid community was restricted to microsites characterized by soils with higher SOC and N concentrations. A greater efficiency of nutrient accumulation per unit rhizome mass and the maintenance of rhizome nutrient pools of similar magnitude to those of the rhizomatous grass in the mesic community may also contribute to the distribution of rhizomatous grasses in semi-arid communities. The existence of nutrient islands beneath a wide range of clone sizes in both mesic and semi-arid communities provides circumstantial evidence to suggest that nutrient islands beneath caespitose grasses may contribute to clone fitness in this growth form.10aGrazing10aislands of fertility10anutrient accumulation10anutrient islands10ashortgrass prairie10atallgrass prairie1 aDerner, J.D.1 aBriske, D.D.  uhttp://knz.lternet.edu/content/below-ground-carbon-and-nitrogen-accumulation-perennial-grasses-comparison-caespitose-and01930nas a2200181   4500008004100000245009000041210006900131260003800200300001300238520126500251100001701516700001701533700001701550700002201567700001701589700002201606856012001628       1999                        eng d00aDo caespitose and rhizomatous grass growth forms constitute unique functional groups?0 aDo caespitose and rhizomatous grass growth forms constitute uniq  aTownsville, Queensland, Australia  a927 -9283 aStudies of a semiarid shortgrass plant community (Central Plains Experimental Range, Colorado, USA) and a mesic tallgrass community (Konza Prairie Research Natural Area, Kansas, USA) are described. Soil C and N pools were measured from soil cores taken below rhizomatous and caespitose grass species from both grazed and ungrazed sites. Physiological plasticity was determined for the roots of both grass types by exposure to ammonium sulfate solution and rhizome and root morphological plasticity was determined on the long-term grazed sites. Caespitose grasses [Schizachyrium scoparium and Bouteloua gracilis] accumulated larger pools of nutrients in soils directly beneath plants than rhizomatous grasses [Andropogon gerardii and Pascopyrum smithii [Elymus smithii]] did in rhizomes. Caespitose and rhizomatous grasses had inconsistent modifications of nutrient pools on grazed compared with ungrazed sites, which indicated the occurrence of either species- or system-specific responses. Neither grass type expressed morphological or physiological root plasticity in the mesic community but both grass types expressed morphological root plasticity and the rhizomatous grass displayed significant physiological root plasticity in the semiarid plant community1 aDerner, J.D.1 aBriske, D.D.1 aEldridge, D.1 aFreudenberger, D.1 aEldridge, D.1 aFreudenberger, D.  uhttp://knz.lternet.edu/content/do-caespitose-and-rhizomatous-grass-growth-forms-constitute-unique-functional-groups02416nas a2200181   4500008004100000245011800041210006900159300001300228490000700241520173500248653001801983653001902001653002502020653002702045100001702072700001702089856012802106       1999                        eng d00aDoes a tradeoff exist between morphological and physiological root plasticity? A comparison of grass growth forms0 aDoes a tradeoff exist between morphological and physiological ro  a519 -5260 v203 aA series of experiments were conducted to evaluate the potential tradeoff between morphological and physiological root plasticity in caespitose and rhizomatous grass growth forms in semi-arid and mesic communities. Morphological and physiological root plasticity were evaluated with in-growth cores and excised root assays, respectively. The rhizomatous grass in the semi-arid community was the only species to display significant physiological root plasticity, but all species possessed the capacity to proportionally increase 15N uptake with increasing concentrations of (15NH4)2SO4 solution. Neither the caespitose nor the rhizomatous grass displayed morphological root plasticity in response to nitrogen addition in the mesic community. In contrast, significant morphological root plasticity occurred in species of both growth forms in the semi-arid community. These data suggest that the compact architecture and the ability to accumulate nutrients in soils directly beneath caespitose grasses did not increase selection pressure for physiological root plasticity at the expense of morphological root plasticity and that the coarse grained foraging strategy and low density of large diameter roots did not increase morphological root plasticity at the expense of physiological root plasticity in rhizomatous grasses. These preliminary data suggest that 1) a high maximum uptake rate for nitrogen in these perennial grasses may minimize the expression of physiological root plasticity, 2) morphological and physiological root plasticity may represent complimentary, rather than alternative, foraging strategies, and 3) the expression of root plasticity may be strongly influenced by abiotic variables within specific habitats.10aclonal plants10aplant foraging10aplant-soil relations10aResource heterogeneity1 aDerner, J.D.1 aBriske, D.D.  uhttp://knz.lternet.edu/content/does-tradeoff-exist-between-morphological-and-physiological-root-plasticity-comparison-grass