@article {KNZ001242,
	title = {Conservation of nitrogen increases with precipitation across a major grassland gradient in the Central Great Plains of North America},
	journal = {Oecologia},
	volume = {159},
	year = {2009},
	pages = {571 -581},
	abstract = {<p>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\&ndash;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.</p>},
	keywords = {LTER-KNZ, Grasslands, Net nitrogen mineralization, Nitrogen pools, Nitrogen use efficiency, Regional trends},
	doi = {10.1007/s00442-008-1229-1},
	url = {https://link.springer.com/article/10.1007\%2Fs00442-008-1229-1},
	author = {McCulley, R.L. and Burke, I.C. and Lauenroth, W.K.}
}
@article {KNZ001016,
	title = {A comparison of the species-timerelationship across ecosystems and taxonomic groups},
	journal = {Oikos},
	volume = {112},
	year = {2006},
	pages = {185 -195},
	abstract = {The species{\textendash}time relationship (STR) describes how the species richness of a community increases with the time span over which the community is observed. This pattern has numerous implications for both theory and conservation in much the same way as the species{\textendash}area relationship (SAR). However, the STR has received much less attention and to date only a handful of papers have been published on the pattern. Here we gather together 984 community time-series, representing 15 study areas and nine taxonomic groups, and evaluate their STRs in order to assess the generality of the STR, its consistency across ecosystems and taxonomic groups, its functional form, and its relationship to local species richness. In general, STRs were surprisingly similar across major taxonomic groups and ecosystem types. STRs tended to be well fit by both power and logarithmic functions, and power function exponents typically ranged between 0.2 and 0.4. Communities with high richness tended to have lower STR exponents, suggesting that factors increasing richness may simultaneously decrease turnover in ecological systems. Our results suggest that the STR is as fundamental an ecological pattern as the SAR, and raise questions about the general processes underlying this pattern. They also highlight the dynamic nature of most species assemblages, and the need to incorporate time scale in both basic and applied research on species richness patterns.},
	keywords = {LTER-KNZ},
	doi = {10.1111/j.0030-1299.2006.14223.x},
	author = {White, E.P. and P. Adler and Lauenroth, W.K. and Gill, R.A. and Greenberg, D. and Kaufman, D.M. and Rassweiler, A. and Rusak, J.A. and M. A. Smith and Steinbeck, J. and Waide, R.B. and Yao, J.}
}
@article {KNZ001008,
	title = {Evidence for a general species-time-area relationship},
	journal = {Ecology},
	volume = {86},
	year = {2005},
	pages = {2032 -2039},
	abstract = {The species{\textendash}area relationship (SAR) plays a central role in biodiversity research, and recent work has increased awareness of its temporal analogue, the species{\textendash} time relationship (STR). Here we provide evidence for a general species{\textendash}time{\textendash}area relationship (STAR), in which species number is a function of the area and time span of sampling, as well as their interaction. For eight assemblages, ranging from lake zooplankton to desert rodents, this model outperformed a sampling-based model and two simpler models in which area and time had independent effects. In every case, the interaction term was negative, meaning that rates of species accumulation in space decreased with the time span of sampling, while species accumulation rates in time decreased with area sampled. Although questions remain about its precise functional form, the STAR provides a tool for scaling species richness across time and space, for comparing the relative rates of species turnover in space and time at different scales of sampling, and for rigorous testing of mechanisms proposed to drive community dynamics. Our results show that the SAR and STR are not separate relationships but two dimensions of one unified pattern.},
	keywords = {LTER-KNZ},
	doi = {10.1890/05-0067},
	author = {P. Adler and White, E.P. and Lauenroth, W.K. and Kaufman, D.M. and Rassweiler, A. and Rusak, J.A.}
}
@article {KNZ00893,
	title = {Regional patterns in carbon cycling across the Great Plains of North America},
	journal = {Ecosystems},
	volume = {8},
	year = {2005},
	pages = {106 -121},
	abstract = {The 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.},
	keywords = {LTER-KNZ, grassland, Great Plains, litter decomposition, Net primary production, Precipitation, Regional trends, soil respiration},
	doi = {10.1007/s10021-004-0117-8},
	author = {McCulley, R.L. and Burke, I.C. and Nelson, J.A. and Lauenroth, W.K. and Alan K. Knapp and Kelly, E.F.}
}
@article {KNZ00841,
	title = {Influence of climate variability on plant production and N-mineralization in Central US grasslands},
	journal = {Journal of Vegetation Science},
	volume = {13},
	year = {2002},
	pages = {383 -394},
	abstract = {We 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.},
	keywords = {LTER-KNZ, Annual variation, ANPP, Central Grasslands region, Environmental gradient, IGBP Transect, Mineralization, Nitrogen flux, Seasonal variation},
	doi = {10.1111/j.1654-1103.2002.tb02062.x},
	author = {Barrett, J.E. and McCulley, R.L. and Lane, D.R. and Burke, I.C. and Lauenroth, W.K.}
}
@article {KNZ0014,
	title = {Regional climatic similarities in the temperate zones of North and South America},
	journal = {Journal of Biogeography},
	volume = {22},
	year = {1995},
	pages = {915 -925},
	abstract = {<p>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</p>},
	keywords = {LTER-KNZ, climate},
	url = {http://www.jstor.org/stable/2845992},
	author = {Paruelo, J.M. and Lauenroth, W.K. and Epstein, H.E. and Burke, I.C. and Aguiar, M.R. and Sala, O.E.}
}
@article {KNZ00310,
	title = {Regional analysis of the central Great Plains},
	journal = {BioScience},
	volume = {41},
	year = {1991},
	pages = {685 -692},
	keywords = {LTER-KNZ},
	doi = {http://www.jstor.org/stable/1311763},
	author = {Burke, I.C. and Kittel, T.G.F. and Lauenroth, W.K. and Snook, P. and Yonker, C.M. and Parton, W.J.}
}
