02597nas 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.x02905nas a2200313 4500008004100000245013800041210006900179300001500248490000700263520198500270100001202255700001502267700001702282700001702299700001302316700001302329700001502342700001402357700001402371700001502385700001602400700001502416700001702431700002002448700001502468700001602483700001502499856007702514 2008 eng d00aModeled interactive effects of precipitation, temperature, and CO2 on ecosystem carbon and water dynamics in different climatic zones0 aModeled interactive effects of precipitation temperature and CO2 a1986 -19990 v143 a

Interactive effects of multiple global change factors on ecosystem processes are complex. It is relatively expensive to explore those interactions in manipulative experiments. We conducted a modeling analysis to identify potentially important interactions and to stimulate hypothesis formulation for experimental research. Four models were used to quantify interactive effects of climate warming (T), altered precipitation amounts [doubled (DP) and halved (HP)] and seasonality (SP, moving precipitation in July and August to January and February to create summer drought), and elevated [CO2] (C) on net primary production (NPP), heterotrophic respiration (Rh), net ecosystem production (NEP), transpiration, and runoff. We examined those responses in seven ecosystems, including forests, grasslands, and heathlands in different climate zones. The modeling analysis showed that none of the three-way interactions among T, C, and altered precipitation was substantial for either carbon or water processes, nor consistent among the seven ecosystems. However, two-way interactive effects on NPP, Rh, and NEP were generally positive (i.e. amplification of one factor's effect by the other factor) between T and C or between T and DP. A negative interaction (i.e. depression of one factor's effect by the other factor) occurred for simulated NPP between T and HP. The interactive effects on runoff were positive between T and HP. Four pairs of two-way interactive effects on plant transpiration were positive and two pairs negative. In addition, wet sites generally had smaller relative changes in NPP, Rh, runoff, and transpiration but larger absolute changes in NEP than dry sites in response to the treatments. The modeling results suggest new hypotheses to be tested in multifactor global change experiments. Likewise, more experimental evidence is needed for the further improvement of ecosystem models in order to adequately simulate complex interactive processes.

1 aLuo, Y.1 aGerten, D.1 aLe Maire, G.1 aParton, W.J.1 aWeng, E.1 aZhou, X.1 aKeough, C.1 aBeier, C.1 aCiais, P.1 aCramer, W.1 aDukes, J.S.1 aEmmett, B.1 aHanson, P.J.1 aKnapp, Alan, K.1 aLinder, S.1 aNepstad, D.1 aRustad, L. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01629.x02411nas a2200313 4500008004100000245010500041210006900146300001000215490000700225520152600232100001501758700001201773700001701785700001701802700001501819700001301834700001401847700001401861700001501875700001601890700001501906700001701921700002001938700001501958700001601973700001501989700001602004856007702020 2008 eng d00aModelled effects of precipitation on ecosystem carbon and water dynamics in different climatic zones0 aModelled effects of precipitation on ecosystem carbon and water  a1 -150 v143 a

The ongoing changes in the global climate expose the world's ecosystems not only to increasing CO2 concentrations and temperatures but also to altered precipitation (P) regimes. Using four well-established process-based ecosystem models (LPJ, DayCent, ORCHIDEE, TECO), we explored effects of potential P changes on water limitation and net primary production (NPP) in seven terrestrial ecosystems with distinctive vegetation types in different hydroclimatic zones. We found that NPP responses to P changes differed not only among sites but also within a year at a given site. The magnitudes of NPP change were basically determined by the degree of ecosystem water limitation, which was quantified here using the ratio between atmospheric transpirational demand and soil water supply. Humid sites and/or periods were least responsive to any change in P as compared with moderately humid or dry sites/periods. We also found that NPP responded more strongly to doubling or halving of P amount and a seasonal shift in P occurrence than that to altered P frequency and intensity at constant annual amounts. The findings were highly robust across the four models especially in terms of the direction of changes and largely consistent with earlier P manipulation experiments and modelling results. Overall, this study underscores the widespread importance of P as a driver of change in ecosystems, although the ultimate response of a particular site will depend on the detailed nature and seasonal timing of P change.

1 aGerten, D.1 aLuo, Y.1 aLe Maire, G.1 aParton, W.J.1 aKeough, C.1 aWeng, E.1 aBeier, C.1 aCiais, P.1 aCramer, W.1 aDukes, J.S.1 aEmmett, B.1 aHanson, P.J.1 aKnapp, Alan, K.1 aLinder, S.1 aNepstad, D.1 aRustad, L.1 aSowerby, A. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01651.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-decomposition02986nas a2200157 4500008004100000245014500041210006900186300000800255490000700263520235900270100001702629700002102646700002002667700001702687856012402704 2005 eng d00aSimulated carbon sink response of shortgrass steppe, tallgrass prairie and forest ecosystems to rising [CO2], temperature and nitrogen input0 aSimulated carbon sink response of shortgrass steppe tallgrass pr a1 -0 v193 a[1] The response of plant ecosystems to environmental change will determine whether the terrestrial biosphere will remain a substantial carbon sink or become a source during the next century. We use two ecosystem models, the Generic Decomposition And Yield model (G'DAY) and the daily time step version of the Century model (DAYCENT), to simulate net ecosystem productivity (NEP) for three contrasting ecosystems (shortgrass steppe in Colorado, tallgrass prairie in Kansas, and Norway spruce in Sweden) with varying degrees of water, temperature, and nutrient limitation, to determine responses to gradual increases in atmospheric CO2 concentration ([CO2]), temperature, and nitrogen input over 100 years. Using G'DAY, under rising [CO2], there is evidence of C sink “saturation,” defined here as positive NEP reaching an upper limit and then declining toward zero, at all three sites (due largely to increased N immobilization in soil organic matter) but a positive C sink is sustained throughout the 100 years. DAYCENT also predicts a sustained C sink at all three sites under rising [CO2], with evidence of C sink saturation for the Colorado grassland and the C sink levels off after 80 years for the Kansas grassland. Warming reduces soil C and the C sink in both grassland ecosystems but increases the C sink in the forest. Warming increases decomposition and soil N mineralization, which stimulates net primary productivity (NPP) at all sites except when inducing water limitation. At the forest site some of the enhanced N release is allocated to a woody biomass pool with a low N:C ratio so that warming enhances NEP without increased N input at the forest site, but not at the grassland sites. Responses to combinations of treatments are generally additive for DAYCENT but more interactive for G'DAY, especially under combined rising [CO2] and warming at the strongly water- and N-limited shortgrass steppe. Increasing N input alleviates C sink saturation and enhances NEP, NPP, and soil C at all sites. At the water-limited grassland sites the effect of rising [CO2] on growth is greatest during the drier seasons. Key sensitivities in the simulations of NEP are identified and include NPP sensitivity to gradual increase in [CO2], N immobilization as a long-term feedback, and the presence or not of plant biomass pools with low N:C ratio.1 aPepper, D.A.1 aDel Grosso, S.J.1 aMcMurtrie, R.E.1 aParton, W.J. uhttp://knz.lternet.edu/content/simulated-carbon-sink-response-shortgrass-steppe-tallgrass-prairie-and-forest-ecosystems03031nas a2200349 4500008004100000245009100041210006900132300001100201490000800212520198400220653001202204653003002216653002602246653001502272653001202287100001702299700001702316700001502333700001402348700002102362700002002383700002002403700001702423700001902440700001802459700002302477700001602500700001702516700001702533700001502550856011602565 2004 eng d00aWater relations in grassland and desert ecosystems exposed to elevated atmospheric CO20 aWater relations in grassland and desert ecosystems exposed to el a11 -250 v1403 a

Atmospheric CO2 enrichment may stimulate plant growth directly through (1) enhanced photosynthesis or indirectly, through (2) reduced plant water consumption and hence slower soil moisture depletion, or the combination of both. Herein we describe gas exchange, plant biomass and species responses of five native or semi-native temperate and Mediterranean grasslands and three semi-arid systems to CO2 enrichment, with an emphasis on water relations. Increasing CO2 led to decreased leaf conductance for water vapor, improved plant water status, altered seasonal evapotranspiration dynamics, and in most cases, periodic increases in soil water content. The extent, timing and duration of these responses varied among ecosystems, species and years. Across the grasslands of the Kansas tallgrass prairie, Colorado shortgrass steppe and Swiss calcareous grassland, increases in aboveground biomass from CO2 enrichment were relatively greater in dry years. In contrast, CO2-induced aboveground biomass increases in the Texas C3/C4 grassland and the New Zealand pasture seemed little or only marginally influenced by yearly variation in soil water, while plant growth in the Mojave Desert was stimulated by CO2 in a relatively wet year. Mediterranean grasslands sometimes failed to respond to CO2-related increased late-season water, whereas semiarid Negev grassland assemblages profited. Vegetative and reproductive responses to CO2 were highly varied among species and ecosystems, and did not generally follow any predictable pattern in regard to functional groups. Results suggest that the indirect effects of CO2 on plant and soil water relations may contribute substantially to experimentally induced CO2-effects, and also reflect local humidity conditions. For landscape scale predictions, this analysis calls for a clear distinction between biomass responses due to direct CO2 effects on photosynthesis and those indirect CO2 effects via soil moisture as documented here.

10abiomass10aCarbon dioxide enrichment10aLandscape predictions10asoil water10aStomata1 aMorgan, J.A.1 aPataki, D.E.1 aKorner, C.1 aClark, H.1 aDel Grosso, S.J.1 aGrunzweig, J.M.1 aKnapp, Alan, K.1 aMosier, A.R.1 aNewton, P.C.D.1 aNiklaus, P.A.1 aNippert, Jesse, B.1 aNowak, R.S.1 aParton, W.J.1 aPolley, H.W.1 aShaw, M.R. uhttp://knz.lternet.edu/content/water-relations-grassland-and-desert-ecosystems-exposed-elevated-atmospheric-co201024nas a2200313 4500008004100000245010500041210006900146260003100215300001300246100001700259700002100276700002100297700001600318700001900334700001800353700001800371700001900389700001700408700001900425700001500444700001800459700002100477700001500498700002000513700001500533700001800548700001600566856012800582 1996 eng d00aGlobal grassland ecosystem modelling: development and test of ecosystem models for grassland systems0 aGlobal grassland ecosystem modelling development and test of eco aChichesterbWiley and Sons a229 -2701 aParton, W.J.1 aCoughenour, M.B.1 aScurlock, J.M.O.1 aOjima, D.S.1 aGilmanov, T.G.1 aScholes, R.J.1 aSchimel, D.S.1 aKirchner, T.B.1 aMenaut, J.C.1 aSeastedt, T.R.1 aMoya, E.G.1 aKamnalrut, A.1 aKinyamario, J.I.1 aHall, D.O.1 aBreymeyer, A.I.1 aHall, D.O.1 aMelillo, J.M.1 aAgren, G.I. uhttp://knz.lternet.edu/content/global-grassland-ecosystem-modelling-development-and-test-ecosystem-models-grassland-systems01102nas a2200361 4500008004100000245008800041210006900129260003100198300001300229100001600242700001700258700002100275700002100296700002000317700001900337700001500356700001800371700001500389700001900404700001900423700001800442700002100460700001500481700001700496700001500513700001800528700001900546700002000565700001500585700001800600700001600618856010600634 1996 eng d00aImpact of climate and atmospheric carbon dioxide changes on grasslands of the world0 aImpact of climate and atmospheric carbon dioxide changes on gras aChichesterbWiley and Sons a271 -3121 aOjima, D.S.1 aParton, W.J.1 aCoughenour, M.B.1 aScurlock, J.M.O.1 aKirchener, T.B.1 aKittel, T.G.F.1 aHall, D.O.1 aSchimel, D.S.1 aMoya, E.G.1 aGilmanov, T.G.1 aSeastedt, T.R.1 aKamnalrut, A.1 aKinyamario, J.I.1 aLong, S.P.1 aMenaut, J.C.1 aSala, O.E.1 aScholes, R.J.1 avan Veen, J.A.1 aBreymeyer, A.I.1 aHall, D.O.1 aMelillo, J.M.1 aAgren, G.I. uhttp://knz.lternet.edu/content/impact-climate-and-atmospheric-carbon-dioxide-changes-grasslands-world01561nas a2200193 4500008004100000245007400041210006900115300001300184520093700197100001801134700001801152700001701170700001801187700001901205700001601224700001701240700001501257856009501272 1996 eng d00aNew technologies for remote sensing of ecosystem change in rangelands0 aNew technologies for remote sensing of ecosystem change in range a139 -1423 aThe collective area of rangelands, 40-50% of the global land surface, presents significant logistical challenges for obtaining ecological data for large, heterogeneous areas quickly, cheaply and with a significant level of accuracy. The use of remote sensing for rangeland monitoring and scaling up from plot to region is reviewed. A major challenge in remote sensing applications lies with assessing ecosystem function from spectral measurements of ecosystem structure. New methods which may assist in the identification and tracking of rangeland response to management practices at the regional scale and provide information on vegetation structure at the continental scale are described. On-going attempts to develop a coupled remote sensing rangeland ecosystem modelling approach for monitoring structure and quantifying energy flow and nutrient cycling are described and examples using Konza Prairie, Kansas, USA data are given1 aWessman, C.A.1 aSchimel, D.S.1 aArcher, S.R.1 aBateson, C.A.1 aBraswell, B.H.1 aOjima, D.S.1 aParton, W.J.1 aWest, N.E. uhttp://knz.lternet.edu/content/new-technologies-remote-sensing-ecosystem-change-rangelands02783nas a2200157 4500008004100000245013700041210006900178300001300247490000600260520216300266100001902429700001802448700001602466700001702482856012602499 1994 eng d00aImportance of photosynthetic pathways, management, and climate on plant production and soil carbon of semihumid temperate grasslands0 aImportance of photosynthetic pathways management and climate on  a344 -3540 v43 aA modeling study evaluated the importance of photosynthetic pathways (C3, C4, or both) and management strategies to the foliage productivity and soil carbon characteristics of a semihumid temperate grassland subjected to various combinations of climate change. Model values for plant and soil characteristics were obtained at sites near Manhattan, Kansas, and the Manhattan climate record provided the nominal climatic drivers. Model runs used both actual monthly temperature and precipitation data for a 100—yr interval and average weather conditions generated from this record. Monthly temperatures were increased 2°C, left unchanged, or decreased 2°C; annual precipitation was increased 6 cm, left unchanged, or decreased 6 cm. All possible combinations of temperature and precipitation were then used in 100—yr simulations. Regardless of the specific climate scenario, plant production was lowest for C3 grasses and highest for the mixed C3—C4 community. The nominal seasonal pattern of precipitation favored an active C3 plant community in early to late spring, prior to the emergence of the C4 vegetation. However, the higher growth and water use efficiencies of C4 vegetation during summer contributed to the maximization response of the grasslands containing both C3 and C4 grasses. An analysis of variance of annual average values observed from 100—yr simulations was used to evaluate the relative importance of climate, photosynthetic pathways, and management activities (annually burned, burned every 4 yr, unburned, or lightly grazed) to plant production and soil carbon values. Photosynthetic pathway and precipitation were identified as the most significant single variables affecting foliage production; the interaction between photosynthetic and temperature was the most significant interaction term. Management treatments were by far the most important variables affecting soil carbon values, but 2°C warming did produce substantial soil carbon losses from C3 grasslands. Enhanced carbon fixation by the C4 and C3—C4 plant communities negated the losses of soil carbon caused by enhanced soil respiration at warmer temperatures.1 aSeastedt, T.R.1 aCoxwell, C.C.1 aOjima, D.S.1 aParton, W.J. uhttp://knz.lternet.edu/content/importance-photosynthetic-pathways-management-and-climate-plant-production-and-soil-carbon02099nas a2200241 4500008004100000245008100041210006900122300001100191490000700202520134400209653001101553653000901564653001901573653001901592653002801611653002401639653002201663100001601685700001801701700001701719700001801736856010301754 1994 eng d00aLong and short-term effects of fire on nitrogen cycling in tallgrass prairie0 aLong and shortterm effects of fire on nitrogen cycling in tallgr a67 -840 v243 aFires in the tallgrass prairie are frequent and significantly alter nutrient cycling processes. We evaluated the short-term changes in plant production and microbial activity due to fire and the long-term consequences of annual burning on soil organic matter (SOM), plant production, and nutrient cycling using a combination of field, laboratory, and modeling studies. In the short-term, fire in the tallgrass prairie enhances microbial activity, increases both above-and belowground plant production, and increases nitrogen use efficiency (NUE). However, repeated annual burning results in greater inputs of lower quality plant residues causing a significant reduction in soil organic N, lower microbial biomass, lower N availability, and higher C:N ratios in SOM. Changes in amount and quality of below-ground inputs increased N immobilization and resulted in no net increases in N availability with burning. This response occurred rapidly (e.g., within two years) and persisted during 50 years of annual burning. Plant production at a long-term burned site was not adversely affected due to shifts in plant NUE and carbon allocation. Modeling results indicate that the tallgrass ecosystem responds to the combined changes in plant resource allocation and NUE. No single factor dominates the impact of fire on tallgrass plant production.10acarbon10afire10aimmobilization10aMineralization10aNitrogen use efficiency10asoil organic matter10atallgrass prairie1 aOjima, D.S.1 aSchimel, D.S.1 aParton, W.J.1 aOwensby, C.E. uhttp://knz.lternet.edu/content/long-and-short-term-effects-fire-nitrogen-cycling-tallgrass-prairie02304nas a2200253 4500008004100000245010800041210006900149300001300218490000600231520146900237100001701706700002101723700001601744700001901760700001801779700001801797700001701815700001701832700001901849700001501868700001801883700002101901856012801922 1993 eng d00aObservations and modeling of biomass and soil organic matter dynamics for the grassland biome worldwide0 aObservations and modeling of biomass and soil organic matter dyn a785 -8090 v73 aCentury is a model of terrestrial biogeochemistry based on relationships between climate, human management (fire, grazing), soil properties, plant productivity, and decomposition. The grassland version of the Century model was tested using observed data from 11 temperate and tropical grasslands around the world. The results show that soil C and N levels can be simulated to within ±25% of the observed values (100 and 75% of the time, respectively) for a diverse set of soils. Peak live biomass and plant production can be simulated within ± 25% of the observed values (57 and 60% of the time, respectively) for burned, fertilized, and irrigated grassland sites where precipitation ranged from 22 to over 150 cm. Live biomass can be generally predicted to within ±50% of the observed values (57% of the time). The model underestimated the live biomass in extremely high plant production years at two of the Russian sites. A comparison of Century model results with statistical models showed that the Century model had slightly higher r2 values than the statistical models. Data and calibrated model results from this study are useful for analysis and description of grassland carbon dynamics, and as a reference point for testing more physiologically based models prediction's of net primary production and biomass. Results indicate that prediction of plant and soil organic matter (C and N) dynamics requires knowledge of climate, soil texture, and N inputs.1 aParton, W.J.1 aScurlock, J.M.O.1 aOjima, D.S.1 aGilmanov, T.G.1 aScholes, R.J.1 aSchimel, D.S.1 aKirchner, T.1 aMenaut, J.C.1 aSeastedt, T.R.1 aMoya, E.G.1 aKamnalrut, A.1 aKinyamario, J.I. uhttp://knz.lternet.edu/content/observations-and-modeling-biomass-and-soil-organic-matter-dynamics-grassland-biome-worldwide01816nas a2200145 4500008004100000245013800041210006900179300001300248490000700261520123400268100001901502700001701521700001601538856011601554 1992 eng d00aMass loss and nitrogen dynamics of decaying litter of grasslands: the apparent low nitrogen immobilization potential of root detritus0 aMass loss and nitrogen dynamics of decaying litter of grasslands a384 -3910 v703 a

Litter-bag studies and simulation modeling were used to examine the relationship between mass loss and nitrogen content of decaying prairie foliage and root litter. In contrast with forest studies, grassland roots were low in lignin and nitrogen, decayed more rapidly than foliage, and demonstrated very low nitrogen immobilization potentials. Our findings agree with reports indicating that buried substrates with high C:N ratios do not immobilize substantial amounts of nitrogen-limited environments induce steeper slopes in the mass loss-nitrogen concentration relationship. However, results suggesting rapid nitrogen mineralization contradict our own studies demonstrating reduced inorganic nitrogen availability in soils of frequently burned prairie. Simulation of observed patterns using the CENTURY grassland model indicated that these results could not occur without creating soil organic matter with unrealistically high C:N ratios. Litter-bag studies of buried substrates therefore may provide an incomplete perspective on the mass loss and nitrogen dynamics of buried litter in grassland and agroecosystem soils. key words: Andropogon gerardii, C:N ratio, decomposition, immobilization, mineralization, nitrogen

1 aSeastedt, T.R.1 aParton, W.J.1 aOjima, D.S. uhttp://knz.lternet.edu/content/mass-loss-and-nitrogen-dynamics-decaying-litter-grasslands-apparent-low-nitrogen03436nas a2200193 4500008004100000245007900041210006900120300001300189490000700202520279700209653002203006100001803028700001903046700002003065700001903085700001703104700001603121856010503137 1991 eng d00aPhysiological interactions along resource gradients in a tallgrass prairie0 aPhysiological interactions along resource gradients in a tallgra a672 -6840 v723 a

Spatial variability in availability of resources that limit photosynthesis (water and N) leads to variation in rates of atmosphere- biosphere exchange. N content and allocation are canopy properties that link ecosystem, physiological, and biophysical processes and that vary in space at scales relevant to atmosphere-biosphere interaction. We studied landscape-scale variation in these and related canopy properties in Kansas Tallgrass Prairie (USA). The tallgrass ecosystem was suited to this investigation because primary production in the prairie is constrained by N availability. This work was designed to aid in interpertation and spatial extrapolation of gas exchange measurements made using aerodynamic techniques as part of FIFE (First ISLSCP Field Experiment), a NASA- supported study. We collected data on spatial disrtibution of biomass, leaf area index (LAI), canopy N mass. N concentration ([N]), and gas exchange along topographic and management gradients. We also measured height distribution of N, light interception, and gas exchange within canopies as a function of position in the landscape. Substantial variation in biomass, LAI, N accumulation, and N allocation occurred over time, with topography, and as a result of previous burning. The verticle gradient of [N] and photosynthetic capacity within canopies were correlated, in space and time, with biomass and canopy light interception. The gradients were steper in high biomass sites than in low biomass sites. In addition, proportional N allocation to the upper layer increased with time (12% in June, 32% in August) as biomass increased. As nutrient uptake increased within the tallgrass landscape, biomass increased and light limitation in the lower canopy was induced. As this light limitation increased with increasing biomass, or with accumulation of dead vegetation, allocation of N to the upper canopy increased. Height distribution of photosyntheticd capicity paralleled within-canopy N allocation and light interception. As resource ratios (light, water and nitrogen) varied in the landscape, so did rates of gas exchange. This work suggests that in interactions between light extinction, N allocation, and photosynthesis that have been proposed for monospecific stands apply to the multispecies, but structurally simple, canopy of the tallgrass prairie. Models of plant performance based on evolutionary arguments may provide a powerful basis for spatial extarapolation of atmosphere-ecosystem exchange rates from sites to landscape and larger regions. Key words: atmosphere-ecosystem exchange, FIFE; Konza Prairie Long-Term Ecological Research site; leaf area index; light interception; nitrogen allocation; photosynthetic capacity; photosynthetically active radiation; remote sensing; toposequences

10atallgrass prairie1 aSchimel, D.S.1 aKittel, T.G.F.1 aKnapp, Alan, K.1 aSeastedt, T.R.1 aParton, W.J.1 aBrown, V.B. uhttp://knz.lternet.edu/content/physiological-interactions-along-resource-gradients-tallgrass-prairie00508nas 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-plains01599nas a2200169 4500008004100000245010600041210006900147300001300216490000700229520097300236653002201209100001701231700001801248700001901266700001701285856012701302 1989 eng d00aEffects of available P and N:P ratios on non-symbiotic dinitrogen fixation in tallgrass prairie soils0 aEffects of available P and NP ratios on nonsymbiotic dinitrogen  a471 -4740 v793 a

Prescribed burning is a major control over element cycles in Tallgrass prairie (Eastern Kansas, USA). In this paper we report potential effects on fire on non-symbiotic nitrogen fixation. Fire resulted in additions of available P in ash, which may stimulate nitrogen fixation by terrestrial cyanobacteria. Cyanobacterial nitrogenase activity and biomass responded positively to additions of ash or P in laboratory assays using soil. Further assays in soils showed that cyanobacteria responded to changes in available N: available P ratio (aN:P) across a range of concentrations. Nitrogen fixation rate could be related empirically to a N:P via a log-linear relationship. Extrapolation of laboratory results to the field yielded a maximal estimate of 21 kg N ha-1y-1. Results support arguments from the marine and terrestrial literature that P availability is central to regulation of ecosystem N budgets. Key words: Cyanobacteria, fire, acetyline reduction, ash

10atallgrass prairie1 aEisele, K.A.1 aSchimel, D.S.1 aKapustka, L.A.1 aParton, W.J. uhttp://knz.lternet.edu/content/effects-available-p-and-np-ratios-non-symbiotic-dinitrogen-fixation-tallgrass-prairie-soils01774nas a2200193 4500008004100000245009300041210006900134260002700203300001300230520109000243653002201333100001601355700001701371700001901388700001801407700002901425700001901454856010701473 1988 eng d00aSimulating the long-term impact of burning on C, N, and P cycling in a tallgrass prairie0 aSimulating the longterm impact of burning on C N and P cycling i aRoma, ItalybVia Nizza a353 -3703 a

A model has been developed to simulate the long-term dynamics of soil organic matter and plant production in response to different management practices. The model simulates the flow of C, N, and P in soil-plant systems and deals primarily with the cycling of nutrients in various soil organic matter pools. The model was used to simulate the long- term effects of different fire frequency and timing of the burning on soil organic matter levels, nutrient cycling and plant production. The model results are compared to nutrient cycling data, soil organic matter data and plant production data from a site in Kansas which was established in 1928 to study the impact of annual burning on a tallgrass prairie. The model results compare very favorably with the observed data and show that maximum production is achieved by annual burning in the late spring (April 20). The annual burning also causes the soil organic matter levels and N mineralization potential to decrease. Burning tends to increase the inorganic P levels at the soil surface, which results in increased N fixation

10atallgrass prairie1 aOjima, D.S.1 aParton, W.J.1 aSchimell, D.S.1 aOwensby, C.E.1 aGiovannozzi-Sermanni, G.1 aNannipieri, P. uhttp://knz.lternet.edu/content/simulating-long-term-impact-burning-c-n-and-p-cycling-tallgrass-prairie