02388nas a2200205 4500008004100000245013700041210006900178300001300247490000800260520167900268653001501947653003201962653001901994653002802013653002002041100001902061700001602080700002002096856006602116 2009 eng d00aConservation of nitrogen increases with precipitation across a major grassland gradient in the Central Great Plains of North America0 aConservation of nitrogen increases with precipitation across a m a571 -5810 v1593 a

Regional analyses and biogeochemical models predict that ecosystem N pools and N cycling rates must increase from the semi-arid shortgrass steppe to the sub-humid tallgrass prairie of the Central Great Plains, yet few field data exist to evaluate these predictions. In this paper, we measured rates of net N mineralization, N in above- and belowground primary production, total soil organic matter N pools, soil inorganic N pools and capture in resin bags, decomposition rates, foliar 15N, and N use efficiency (NUE) across a precipitation gradient. We found that net N mineralization did not increase across the gradient, despite more N generally being found in plant production, suggesting higher N uptake, in the wetter areas. NUE of plants increased with precipitation, and δ15N foliar values and resin-captured N in soils decreased, all of which are consistent with the hypothesis that N cycling is tighter at the wet end of the gradient. Litter decomposition appeared to play a role in maintaining this regional N cycling trend: litter decomposed more slowly and released less N at the wet end of the gradient. These results suggest that immobilization of N within the plant–soil system increases from semi-arid shortgrass steppe to sub-humid tallgrass prairie. Despite the fact that N pools increase along a bio-climatic gradient from shortgrass steppe to mixed grass and tallgrass prairie, this element becomes relatively more limiting and is therefore more tightly conserved at the wettest end of the gradient. Similar to findings from forested systems, our results suggest that grassland N cycling becomes more open to N loss with increasing aridity.

10aGrasslands10aNet nitrogen mineralization10aNitrogen pools10aNitrogen use efficiency10aRegional trends1 aMcCulley, R.L.1 aBurke, I.C.1 aLauenroth, W.K. uhttps://link.springer.com/article/10.1007%2Fs00442-008-1229-102597nas a2200205 4500008004100000245011500041210006900156300001500225490000700240520194100247100001702188700001702205700001402222700001302236700001602249700001702265700001502282700001702297856007702314 2009 eng d00aLong-term patterns of mass loss during the decomposition of leaf and fine root litter: an intersite comparison0 aLongterm patterns of mass loss during the decomposition of leaf  a1320 -13380 v153 a

Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 sites and nine litter types (for a total of 234 cases) was used to test the frequency of this later, slow phase of decomposition. Litter mass remaining after up to 10 years of decomposition was fit to models that included (dual exponential and asymptotic) or excluded (single exponential) a slow phase. The resultant regression equations were evaluated for goodness of fit as well as biological realism. Regression analysis indicated that while the dual exponential and asymptotic models statistically and biologically fit more of the litter type–site combinations than the single exponential model, the latter was biologically reasonable for 27–65% of the cases depending on the test used. This implies that a slow phase is common, but not universal. Moreover, estimates of the decomposition rate of the slowly decomposing component averaged 0.139–0.221 year−1 (depending on method), higher than generally observed for mineral soil organic matter, but one-third of the faster phase of litter decomposition. Thus, this material may be slower than the earlier phases of litter decomposition, but not as slow as mineral soil organic matter. Comparison of the long-term integrated decomposition rate (which included all phases of decomposition) to that for the first year of decomposition indicated the former was on average 75% that of the latter, consistent with the presence of a slow phase of decomposition. These results indicate that the global store of litter estimated using short-term decomposition rates would be underestimated by at least one-third.

1 aHarmon, M.E.1 aSilver, W.L.1 aFasth, B.1 aChen, H.1 aBurke, I.C.1 aParton, W.J.1 aHart, S.C.1 aCurrie, W.S. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01837.x01489nas a2200241 4500008004100000245009000041210006900131300001300200490000800213520073000221100001700951700001700968700001600985700001701001700001701018700001701035700001501052700001601067700001701083700001501100700001401115856011801129 2007 eng d00aGlobal-scale similarities in nitrogen release patterns during long-term decomposition0 aGlobalscale similarities in nitrogen release patterns during lon a361 -3640 v3153 aLitter decomposition provides the primary source of mineral nitrogen (N) for biological activity in most terrestrial ecosystems. A 10-year decomposition experiment in 21 sites from seven biomes found that net N release from leaf litter is dominantly driven by the initial tissue N concentration and mass remaining regardless of climate, edaphic conditions, or biota. Arid grasslands exposed to high ultraviolet radiation were an exception, where net N release was insensitive to initial N. Roots released N linearly with decomposition and exhibited little net N immobilization. We suggest that fundamental constraints on decomposer physiologies lead to predictable global-scale patterns in net N release during decomposition.1 aParton, W.J.1 aSilver, W.L.1 aBurke, I.C.1 aGrassens, L.1 aHarmon, M.E.1 aCurrie, W.S.1 aKing, J.Y.1 aAdair, E.C.1 aBrandt, L.A.1 aHart, S.C.1 aFasth, B. uhttp://knz.lternet.edu/content/global-scale-similarities-nitrogen-release-patterns-during-long-term-decomposition02490nas a2200265 4500008004100000245008100041210006900122300001300191490000600204520166200210653001401872653001701886653002501903653002701928653001801955653002001973653002101993100001902014700001602033700001702049700002002066700002002086700001602106856010202122 2005 eng d00aRegional patterns in carbon cycling across the Great Plains of North America0 aRegional patterns in carbon cycling across the Great Plains of N a106 -1210 v83 aThe large organic carbon (C) pools found in noncultivated grassland soils suggest that historically these ecosystems have had high rates of C sequestration. Changes in the soil C pool over time are a function of alterations in C input and output rates. Across the Great Plains and at individual sites through time, inputs of C (via aboveground production) are correlated with precipitation; however, regional trends in C outputs and the sensitivity of these C fluxes to annual variability in precipitation are less well known. To address the role of precipitation in controlling grassland C fluxes, and thereby soil C sequestration rates, we measured aboveground and belowground net primary production (ANPP-C and BNPP-C), soil respiration (SR-C), and litter decomposition rates for 2 years, a relatively dry year followed by a year of average precipitation, at five sites spanning a precipitation gradient in the Great Plains. ANPP-C, SR-C, and litter decomposition increased from shortgrass steppe (36, 454, and 24 g C m−2 y−1) to tallgrass prairie (180, 1221, and 208 g C m−2 y−1 for ANPP-C, SR-C, and litter decomposition, respectively). No significant regional trend in BNPP-C was found. Increasing precipitation between years increased rates of ANPP-C, BNPP-C, SR-C, and litter decomposition at most sites. However, regional patterns of the sensitivity of ANPP-C, BNPP-C, SR-C, and litter decomposition to between-year differences in precipitation varied. BNPP-C was more sensitive to between-year differences in precipitation than were the other C fluxes, and shortgrass steppe was more responsive than were mixed grass and tallgrass prairie.10agrassland10aGreat Plains10alitter decomposition10aNet primary production10aPrecipitation10aRegional trends10asoil respiration1 aMcCulley, R.L.1 aBurke, I.C.1 aNelson, J.A.1 aLauenroth, W.K.1 aKnapp, Alan, K.1 aKelly, E.F. uhttp://knz.lternet.edu/content/regional-patterns-carbon-cycling-across-great-plains-north-america02408nas a2200133 4500008004100000245009900041210006900140300001300209490000700222520188500229100001902114700001602133856012502149 2004 eng d00aMicrobial community composition across the Great Plains: Landscape versus regional variability0 aMicrobial community composition across the Great Plains Landscap a106 -1150 v683 aRates of nutrient cycling vary across landscape and regional scales. This biogeochemical variability can be partially attributed to patterns in plant community characteristics and abiotic and edaphic conditions across topographic gradients at the landscape-scale or across regional climatic gradients. However, it is also possible that concomitant changes in the microbial communities performing these biogeochemical processes occur across the same spatial scales and may therefore contribute to the observed biogeochemical trends. To assess patterns of microbial community composition across regional and landscape scales, we sampled upland and lowland topographic positions at three grassland communities spanning a 500-mm regional precipitation gradient across the central Great Plains. Soil microbial community composition and biomass were determined using phospholipid fatty acid (PLFA) analysis. Microbial biomass increased across the regional gradient, and different microbial communities were associated with the different grassland community types. The relative abundance of fungi decreased while gram-negative anaerobic bacteria increased from shortgrass steppe to tallgrass prairie. There were no differences in microbial biomass at the landscape-scale, and the only alteration in microbial community composition between upland and lowland landscape positions was a shift toward more nonspecific bacteria in lowlands. The fact that the trends in microbial biomass and community composition at the landscape-scale were less pronounced suggests that variability in microbial community composition is larger regionally across the Great Plains than landscape variability associated with topographical features at any particular site. Alterations in the microbial community may play a role in determining the biogeochemical patterns of grasslands in the Great Plains region.1 aMcCulley, R.L.1 aBurke, I.C. uhttp://knz.lternet.edu/content/microbial-community-composition-across-great-plains-landscape-versus-regional-variability02373nas a2200265 4500008004100000245010300041210006900144300001300213490000700226520149600233653002101729653000901750653003001759653002701789653001801816653001901834653001801853653002301871100001801894700001901912700001501931700001601946700002001962856012501982 2002 eng d00aInfluence of climate variability on plant production and N-mineralization in Central US grasslands0 aInfluence of climate variability on plant production and Nminera a383 -3940 v133 aWe assessed the influence of annual and seasonal climate variability over soil organic matter (SOM), above-ground net primary production (ANPP) and in situ net nitrogen (N) mineralization in a regional field study across the International Geosphere Biosphere Programme (IGBP) North American mid-latitude transect (Koch et al. 1995). We hypothesized that while trends in SOM are strongly correlated with mean climatic parameters, ANPP and net N-mineralization are more strongly influenced by annual and seasonal climate because they are dynamic processes sensitive to short-term variation in temperature and water availability. Seasonal and monthly deviations from long-term climatic means, particularly precipitation, were greatest at the semi-arid end of the transect. ANPP is sensitive to this climatic variability, but is also strongly correlated with mean annual climate parameters. In situ net N-mineralization and nitrification were weakly influenced by soil water content and temperature during the incubation and were less sensitive to seasonal climatic variables than ANPP, probably because microbial transformations of N in the soil are mediated over even finer temporal scales. We found no relationship between ANPP and in situ net N-mineralization. These results suggests that methods used to estimate in situ net N-mineralization are inadequate to represent N-availability across gradients where microbial biomass, N-immobilization or competition among plants and microbes vary.10aAnnual variation10aANPP10aCentral Grasslands region10aEnvironmental gradient10aIGBP Transect10aMineralization10aNitrogen flux10aSeasonal variation1 aBarrett, J.E.1 aMcCulley, R.L.1 aLane, D.R.1 aBurke, I.C.1 aLauenroth, W.K. uhttp://knz.lternet.edu/content/influence-climate-variability-plant-production-and-n-mineralization-central-us-grasslands02723nas a2200193 4500008004100000245010400041210006900145300001300214490000800227520201700235653001402252653002702266653003502293653002302328653002502351100001702376700001602393856012002409 1997 eng d00aContingent effects of plant species on soils along a regional moisture gradient in the Great Plains0 aContingent effects of plant species on soils along a regional mo a393 -4020 v1103 aThe central grassland region of the United States encompasses major gradients in temperature and precipitation that determine the distribution of plant life forms, which in turn may influence key ecosystem processes such as nutrient cycling and soil organic matter dynamics. One such gradient is the threefold increase in precipitation from the eastern Colorado shortgrass-steppe, in the rain shadow of the Rocky Mountains, to the tallgrass prairie in eastern Kansas. We investigated the relative roles of plant species and plant cover in influencing soil C and N cycling in three sites along this gradient. Plant cover (i.e., the presence or absence of an individual plant) was relatively more important than plant species in explaining variability in soil properties at the dry site, the Central Plains Experimental Range in␣northeastern Colorado. However, plant species explained relatively more of the variability in soil properties than did plant cover at the two wetter sites, Hays and Konza, in central and eastern Kansas. The wetter sites had more continuous plant cover, resulting in less plant-cover-induced variation in soil C and N, than did the dry site, which had distinct patches of bare ground. Plant species at the wetter sites had higher and more variable levels of tissue C:N than plant species at the dry site, due to both within species changes and changes in species composition. Aboveground tissue C:N was better correlated with net nitrogen mineralization rates at the wet sites than the dry site. Thus, tissue chemistry appears to exert more control on nitrogen dynamics at the wet than the dry sites. The results suggest that plant species traits that are relevant to nutrient cycling (e.g., tissue C:N ratios, spatial patterns, productivity) reflect environmental limitations as well as species' physiological potentials. Furthermore, a dominant environmental driver such as precipitation may ameliorate or exaggerate the importance of individual species traits for nutrient cycling.10agrassland10a    Litter quality10a   Plant-soil interactions10a   Soil carbon10a   Soil nitrogen1 aVinton, M.A.1 aBurke, I.C. uhttp://knz.lternet.edu/content/contingent-effects-plant-species-soils-along-regional-moisture-gradient-great-plains02459nas a2200193 4500008004100000245008500041210006900126300001300195490000700208520189400215653001202109100001802121700002002139700001802159700001602177700001702193700001502210856004002225 1995 eng d00aRegional climatic similarities in the temperate zones of North and South America0 aRegional climatic similarities in the temperate zones of North a a915 -9250 v223 a

An analysis of the climatic patterns of the temperate zones in North and South America using a global database of monthly precipitation and temperature was performed. Three synthetic variables, identified by a principal component analysis of the monthly data, were used: mean annual precipitation, mean annual temperature and the proportion of the precipitation falling during summer. The spatial gradient of the 3 variables was displayed by constructing a composite colour raster image. A parallelepiped classification algorithm was used to locate areas in both continents that are climatically similar to 5 North American long term ecological research (LTER) sites and to 2 South American LTER sites. The same algorithm was used to identify areas in South America which are climatically similar to some of the major grassland and shrubland types of North America. There was substantial overlap between the climates of North and South America. Most of the climatic patterns found in South America are well represented in North America but there are certain climates in North America that are not found in South America. An example is a climate with relatively low mean annual temperature and high summer precipitation. The climatic signatures of 3 North American LTER sites (Cedar Creek, CPER and Sevilleta) were not found in South America. The climatic signatures of two LTER sites (Konza and Jornada) had some representation in South America. Two South American research sites (Rio Mayo and Las Chilcas) were well represented climatically in North America. The climates of 6 out of 7 selected North American grassland and shrubland types were represented in South America. The northern mixed prairie type was not represented climatically in South America. It is suggested that comparisons of North and South America may provide a powerful test of climatic control over vegetation

10aclimate1 aParuelo, J.M.1 aLauenroth, W.K.1 aEpstein, H.E.1 aBurke, I.C.1 aAguiar, M.R.1 aSala, O.E. uhttp://www.jstor.org/stable/284599200508nas a2200169 4500008004100000245005000041210005000091300001300141490000700154100001600161700001900177700002000196700001400216700001700230700001700247856007400264 1991 eng d00aRegional analysis of the central Great Plains0 aRegional analysis of the central Great Plains a685 -6920 v411 aBurke, I.C.1 aKittel, T.G.F.1 aLauenroth, W.K.1 aSnook, P.1 aYonker, C.M.1 aParton, W.J. uhttp://knz.lternet.edu/content/regional-analysis-central-great-plains