Full references and selected summaries
(in alphabetical order of first author name by data set):

Chinese Forests NPP Data Set References

Gao, Q. and X.S. Zhang (1997) A simulation study of responses of the northeast China transect to elevated CO2 and climate change. Ecological Applications 7, 470-483.

Gao Q. and M. Yu (1998) A model of regional vegetation dynamics and its application to the study of Northeast China Transect (NECT) responses to global change. Global Biogeochemical Cycles 12, 329-344.

Gao, Q., M. Yu and X-S. Yang (2000) A simulation analysis of the relationship between regional primary production and vegetation structure under climatic change scenarios. Ecological Modelling 131, 33-45.

Ni, J. and X.S. Zhang. in press. Climate variability, ecological gradient and the Northeast China Transect (NECT). Journal of Arid Environments 46.

Ni, J. in press. Modeling vegetation distribution and net primary production along a precipitation gradient, the Northeast China Transect (NECT). Ekologia (Bratislava).

Ni, J., M.T. Sykes, I.C. Prentice and W. Cramer. in press. Modeling the vegetation of China using the process-based equilibrium terrestrial biosphere model BIOME3. Global Ecology and Biogeography 9.

Jiang, H., C-H. Peng, M.J. Apps, Y-L. Zhang, P.M. Woodard and Z-M. Wang. (1999) Modelling the net primary productivity of temperate forest ecosystems in China with a GAP model. Ecological Modelling 122, 225-238.

Jiang, H., M.J. Apps, Y-L. Zhang, C-H. Peng and P.M. Woodard (1999) Modelling the spatial pattern of net primary productivity in Chinese forests. Ecological Modelling 122, 275-288.

Fang, J.Y., G.G. Wang, G.H. Liu and S.L. Xu (1998) Forest biomass of China: an estimate based on the biomass-volume relationship. Ecological Applications 8, 1084-1091.

Feng Z.W., X.K. Wang and G. Wu (1999) Biomass and Primary Productivity of Forest Ecosystems in China. Science Press, Beijing. 241 pp. (in Chinese).

IBP Woodlands Data Set References

Burgess, R.L. (1981) Physiognomy and phytosociology of the international woodlands research sites. pp. 1-35. In: Reichle, D.E., ed. Dynamics of forest ecosystems. Cambridge University Press, Cambridge. 683 pp.

DeAngelis, D.L., R.H. Gardner, and H.H. Shugart (1981) Productivity of forest ecosystems studied during the IBP: the woodlands data set. pp. 567-672. In: Reichle, D.E., ed. Dynamics of forest ecosystems. Cambridge University Press, Cambridge. 683 pp.

Van Wijk, W.R., and D.W. Scholte Ubing (1966) Physics of Plant Environment, Ed. W. R. Van Wijk, Northern-Holland Publishing, Amsterdam.

Osnabruck NPP Data Set References

Cannell, M.G.R. (1982) World Forest Biomass and Primary Production Data. Academic Press, London. 391 pp.

Cramer, W., D.W. Kicklighter, A. Fischer, B. Moore, III, G. Churkina, A. Ruimy and A. Schloss (1997) Comparing global models of terrestrial net primary productivity (NPP): Overview and key results. Global Change Biology (forthcoming).

DeAngelis, D.L., R.H. Gardner, and H.H. Shugart (1981) Productivity of forest ecosystems studied during the IBP: the woodlands data set. pp. 567-672. In Reichle, D.E., (ed.) Dynamics of Forest Ecosystems. IBP 23. Cambridge University Press. 683 pp.

Esser, G., I. Aselman, and H.F.H. Lieth (1982) Modelling the carbon reservoir in the system compartment "litter". Mitt. Geol-Palaeontol., Inst. Univ. Hamburg, SCOPE/UNEP Sonderband, Heft 52, 39-58.

Esser, G. (1984) The significance of biospheric carbon pools and fluxes for atmospheric CO2: A proposed model structure. Progress in Biometeorology 3, 253-294.

Esser, G. (1986) The carbon budget of the biosphere - structure and preliminary results of the Osnabrück Biosphere Model. Veroff. Naturf. Ges. zu Emden von 1814 7:1-160. (in German with English summary)

Esser, G. (1987) Sensitivity of Global Carbon Pools and Fluxes to Human and Potential Climatic Impacts. Tellus 39B, 245-260.

Esser, G. and H. Lieth (1989) Productivity Modelling. In: Kitani, O. and C. W. Hall (eds.). Biomass Handbook, Chap. 1.1.3, pp. 36-48. Gordon & Breach, New York, London, Paris, Montreux, Tokyo, Melbourne.

Esser, G. (1990) Modelling Global Terrestrial Sources and Sinks of CO2 with Special Reference to Soil Organic Matter. In: Bouwman, A. F. (ed.). Soils and the Greenhouse Effect, Chap. 10. John Wiley & Sons, Chichester, New York, Brisbane, Toronto, Singapore.

Esser, G. (1991) Osnabrück Biosphere Model: structure, construction, results. In: Modern Ecology: basic and applied aspects (G. Esser and D. Overdieck, eds.). Elsevier, Amsterdam and London. pp. 679-709.

Esser, G. (1992) Implications of Climate Change for Production and Decomposition in Grasslands and Coniferous Forests. Ecological Applications 2, 47-54.

Esser, G., J. Hoffstadt, F. Mack, and U. Wittenberg (1994) High Resolution Biosphere Model, Documentation, Model Version 3.00.00. Mitteilungen aus dem Institut für Pflanzenökologie der Justus-Liebig-Universität Gießen, Heft 2:68 S.

Esser, G. and M. Lautenschlager. (1994). Estimating the Change Of Carbon in the Terrestrial Biosphere from 18000-BP to Present Using a Carbon-Cycle Model. Environmental Pollution 83, 45-53.

Summary

The global High Resolution Biosphere Model (HRBM), which consists of a biome model and a carbon cycle model, was used to estimate the changes of carbon storage in the major pools of the terrestrial biosphere from 18 000 BP to the present. Climate change data to drive the biosphere for 18 000 BP were derived from an Atmospheric General Circulation Model (AGCM). The HRBM data base for the present climate was recalculated for 18 000 BP, using the AGCM anomalies interpolated to a 0.5-degree grid. Important processes influencing carbon storage included (1) climate-induced changes in biospheric processes and vegetation distribution, (2) the CO2 fertilization effect, (3) the inundation of lowland areas resulting from the sea level rise of 100 m. Two scenarios were investigated: the first, which ignored the CO2 fertilization effect, led to total carbon losses from the terrestrial biosphere of -460 x 10^9 t. The second scenario, which assumed that the model formulation of the CO2 fertilization effect as used for preindustrial to present could be extrapolated to the glacial 200 ppmv (parts per million volume), gave a carbon fixation in the terrestrial biosphere of +213 x 10^9 t. When compared with CO2 concentration data and isotopic ratios from air in ice cores, the results of Scenario 1 are not in agreement with the data. Scenario 2 gives realistic delta C-13 shifts in the atmosphere but the biospheric carbon storage at the end of the glacial period seems too large. It is suggested that the low atmospheric CO2 concentration may have favored the C-4 plants in ice age vegetation types. As a consequence the influence of the low CO2 concentration was eventually reduced and the glacial carbon storage in vegetation, litter, and soil was increased.

Foley, J.A. (1994) Net primary productivity in the terrestrial biosphere - the application of a global model. Journal of Geophysical Research - Atmospheres 99, 20773-20783.

Summary

A process-based model of the terrestrial biosphere, DEMETER, was used to simulate global patterns of net primary productivity (NPP). NPP and vegetation biomass for the modern climate were simulated to be 62.1 Gt C per year and 800.6 Gt C, respectively. Simulated NPP was found to be highly correlated to field observations (r=0.9343) and to the results of the empirically based Miami model (r=0.9587).

Lieth, H.F.H. (1972) Modelling the primary productivity of the the world (10 pp., offset). Deciduous Forest Biome Memo Rep. 72-9.

Lieth, H.F.H. (1973) Primary production: terrestrial ecosystems. Human Ecology 1, 303-332.

Lieth, H.F.H. (1975) Modelling the primary productivity of the world. In: Lieth, H. and R.H. Whittaker (eds.), Primary Productivity of the Biosphere. Ecological Studies 14. Springer-Verlag, New York and Berlin. pp. 237-283.

Lieth, H.F.H., and E. Box (1972) Evapotranspiration and primary productivity: C.W. Thornthwaite Memorial Model. Publications in Climatology 25, 37-46. Centerton/Elmer, New Jersey.

Lieth, H.F.H., and G. Esser (1982) Modelling the relation between global net primary productivity and environmental factors [in German]. Unwellttress, Wiss. Beiträge 1982/1983 der Martin Luther Universität Wittenberg, Halle (Saale), pp. 303-321.

Lurin, B., W. Cramer, B. Moore III, and S.I. Rasool (1994) Global terrestrial net primary productivity. Global Change Newsletter, The International Geosphere-Biosphere Programme: A Study of Global Change (IGBP) of the International Council of Scientific Unions, No. 19, September 1994. pp 6-8.

McGuire, A.D., L.A. Joyce, D.W. Kicklighter, J.M. Melillo, G. Esser, and C.J. Vorosmarty (1993) Productivity response of climax temperate forests to elevated temperature and carbon dioxide - a North American comparison between two global models. Climatic Change 24, 287-310.

Summary

Regression- and process-based approaches are assessed for predicting biogeochemical responses of ecosystems to global change. A regression-based model, the Osnabrück Model (OBM), and a process-based model, the Terrestrial Ecosystem Model (TEM), were applied to the historical range of temperate forests in North America in a factorial experiment with three levels of temperature (+0-deg-C, +2-deg-C, and +5-deg-C) and two levels Of CO2 (350 ppmv and 700 ppmv) at a spatial resolution of 0.5-deg latitude/longitude. For contemporary climate (+0-deg-C, 350 ppmv), OBM and TEM estimate the total net primary productivity (NPP) for temperate forests in North America to be 2.250 and 2.602 x 10^15 g C per year, respectively. Although the continental predictions for contemporary climate are similar, the responses of NPP to altered changes differ qualitatively; at +0-deg-C and 700 ppmv CO2, OBM and TEM predict median increases in NPP of 12.5% and 2.5%, respectively. The response of NPP to elevated temperature agrees most between the models in northern areas of moist temperate forest, but disagrees in southern areas and in regions of dry temperate forest - and the response to CO2 is qualitatively different between the models for all regions. These differences occur, in part, because TEM includes known feedbacks between temperature and ecosystem processes that affect N availability, photosynthesis, respiration, and soil moisture. Also, it may not be appropriate to extrapolate regression-based models for climatic conditions that are not now experienced by ecosystems. These results suggest that the process-based approach is able to progress beyond the limitations of the regression-based approach.

Michener, W.K., J.W. Brunt, J.J. Helly, T.B. Kirchner, and S.G. Stafford (1997) Non-geospatial metadata for the ecological sciences. Ecological Applications 7, 330-342.

Nevison, C.D., G. Esser, and E.A. Holland (1996) A global model of changing N2O emissions from natural and perturbed soils. Climatic Change 32, 327-378.

Olson, R.J., J.M.O. Scurlock, R.S. Turner, and S.V. Jennings (1995) Ground-based grasslands data to support remote sensing and ecosystem modeling of terrestrial primary production. pp. 345-350. In: Guyot, G. (ed.) Proceedings of the International Colloquium on Photosynthesis and Remote Sensing. European Association of Remote Sensing Laboratories, Paris/ INRA, Avignon.

Olson, R.J., and S.D. Prince (1996) Global Primary Production Data Initiative update. Global Change Newsletter, The International Geosphere-Biosphere Programme: A Study of Global Change (IGBP) of the International Council of Scientific Unions, No. 27, September 1996. p 13.

Olson, R.J., J.M.O. Scurlock, W. Cramer, W.J. Parton, and S.D. Prince (1997) From Sparse Field Observations to a Consistent Global Data Set on Net Primary Production. IGBP-DIS Working Paper No. 16. International Geosphere-Biosphere Programme Data and Information System, Toulouse, France. 23 pp.

Prince, S.D., R.J. Olson, G. Dedieu, G. Esser, and W. Cramer (1995) Global Primary Production Data Initiative Project Description. IGBP-DIS Working Paper No. 12. International Geosphere-Biosphere Programme Data and Information System, Toulouse, France. 38 pp.

Whittaker, R.H., and P.L. Marks (1975) Methods of Assessing Terrestrial Productivity. In: Lieth, H., Whittaker, R.H. (eds.), Primary Productivity of the Biosphere. Ecological Studies 14. Springer-Verlag, New York and Berlin. pp. 55-118.

Wittenberg, U., and G. Esser (1997) Evaluation of the isotopic disequilibrium in the terrestrial biosphere by a global carbon isotope model. Tellus 49B, 263-269.

OTTER NPP Data Set References

Gholz, H.L. (1982) Environmental limits on aboveground net primary production, leaf area, and biomass in vegetation zones of the Pacific northwest. Ecology 63, 469-481.

Summary

Vegetation parameters were estimated for eight of the 12 major vegetation zones in Oregon and Washington states, along a transect from the Pacific Coast to the east slopes of the Cascade Mountains. Six stands were in forests, one in woodland, and one in the shrub-steppe. Aboveground over-story net primary production (NPP, estimated as the sum of annual stem, branch, and foliage production), aboveground biomass, and leaf area index (all sides) ranged from <100 to 1500 g/m2/yr, 300 to 150,000 g/m2, and 1 to 47, respectively; the minima and maxima for these parameters were in the shrub-steppe and the coastal forest zones, respectively. Maximum leaf area index, biomass, and NPP were all strongly related to a simple index of growing season water balance and mean minimum air temperatures in January. However, in the subalpine conifer zone, cold winter temperatures apparently have a stronger influence than summer water availability. Of the water balance components, evaporative demand alone accounted for >90% of the variation in leaf area index. Although annual precipitation ranged from 200 mm in the shrub-steppe to 2600 mm at the coast, it was a relatively poor predictor of stand structure and production. Biomass and NPP increased linearly up to a leaf area index of about 30 (all-sided): above this point, biomass continued to increase while NPP decreased. Except in the coastal forest zones, NPP was less than maximum values reported for other mature systems elsewhere in the world for the same range of leaf area indices. Compared to other forested regions of the temperate zone with the same NPP, these systems receive more annual precipitation, and have about twice the basal area and biomass on average.

Goward, S.N, R.H. Waring, D.G. Dye and J. Yang (1994) Ecological remote sensing at OTTER: satellite macroscale observations. Ecological Applications 4, 322-343.

Summary

Satellite remote-sensing observations at coarse, global-scale resolution were compared with ground measurements collected during the OTTER study, in order to derive from the satellite data those ecological and environmental variables which are needed to define primary production in western Oregon. The TOMS sensor and the AVHRR sensor provided estimates of incident PAR radiation, intercepted PAR, atmospheric humidity, air temperature, vapor pressure deficit, and drought. The satellite observations compared favorably with the coincident ground measurements, but were only modestly strongly related in some cases. Atmospheric attenuation of the remotely sensed measurements and ground measurement quality both limit the strength of these relationships. We demonstrate that satellite remote sensing is capable of providing information needed for macroscale ecological monitoring. Currently, it appears possible to derive periodic approximations of ecological conditions from AVHRR and TOMS observations, sufficient to drive a simple production-efficiency type model. However, to provide the type of measurement precision required by more refined ecosystem models will require more refined remote-sensing methods.

Law, B.E. and R.H. Waring (1994) Combining remote-sensing and climatic data to estimate net primary production across Oregon. Ecological Applications 4, 717-728.

Summary

Remote sensing data and climatic data were combined for several of the Oregon Transect Ecosystem Research Project (OTTER) forested sites and neighboring shrub sites, to determine whether percentage intercepted photosynthetically active radiation (%IPAR) can be estimated from remotely sensed observations and to evaluate climatic constraints on the ability of vegetation to utilize intercepted radiation for production. The Thematic Mapper Simulator (TMS) normalized difference vegetation index (NDVI) provided a good linear estimate of %IPAR (r2 = 0.97). Vegetation intercepted from 24.8% to 99.9% of incident photosynthetically active radiation (PAR), and aboveground net primacy production (ANPP) ranged from 53 to 1310 g/m2/yr. ANPP was linearly related to annual IPAR across sites (r2 = 0.70). Constraints on the ability of each species to utilize intercepted light, as defined by differential responses to freezing temperatures, drought, and vapor pressure deficit, were quantified from hourly meteorological station measurements near the sites and field physiological measurements. The proportion of intercepted radiation utilized by vegetation ranged from 30%, for the semi-arid juniper woodland and shrub sites to the East, to 97% for the maritime coastal sites. Energy-use efficiency (epsilon(u)), calculated from aboveground production and IPAR modified by the environmental limits, averaged 0.5 g/MJ for the shrub sites and 0.9 g/MJ for the forested sites.

Marshall, J.D., and R.H. Waring (1986) Comparison of methods of estimating leaf-area index in old-growth Douglas-fir. Ecology 67, 975-979.

Summary

Leaf-area index of an old-growth Douglas-fir stand in western Oregon was estimated by a variety of methods: based upon litterfall, light interception, sapwood cross-sectional area, and tree diameter. The first three methods produced similar estimates, but the estimate based on tree diameter was twice as high as the others. Estimates of leaf area based on tree diameter appear to be inaccurate for large trees with variable amounts of live crown. The exceedingly high leaf-area indices previously reported for Douglas-fir forests are therefore unreliable. Sapwood cross-sectional area varies in correspondence with the canopy area and therefore is a better estimator of leaf area on large trees. Maximum LAI estimates based on sapwood area were similar to those for other temperate coniferous forests.

Peterson, D.L. and R.H. Waring (1994) Overview of the Oregon transect ecosystem research project. Ecological Applications 4, 211-225.

Summary

The Oregon Transect Ecosystem Research (OTTER) project studied ecosystem functions in coniferous forests using a variety of methods: computer modeling, experimental and theoretical remote sensing, and ecological field and laboratory techniques. The study focused on predicting the major fluxes of carbon, nitrogen, and water, and the factors that dynamically regulate them. The OTTER project was conceived to test two major questions: (1) Can a generalized ecosystem simulation model, designed to use mainly parameters available from remote sensing, predict the functioning of forests across an environmentally variable region? and (2) To what extent can the variables required by this model be derived from remotely sensed data? A coordinated effort was made to link ground measurements with remote sensing and modeling requirements. The OTTER project was the focus for a NASA-sponsored Multi-sensor Aircraft Campaign (MAC; combining NASA aircraft and sensors with those of others). Having several independent approaches available, both on the ground and from various remote-sensing platforms, proved valuable in estimating and validating many of the critical variables.

Pierce L.L., S.W. Running, and J. Walker (1994) Regional-scale relationships of leaf-area index to specific leaf-area and leaf nitrogen-content. Ecological Applications 4, 313-321.

Summary

Specific leaf area (SLA) describes the allocation of leaf biomass per unit of leaf area, and is an important link between vegetation water and carbon cycles. Several studies in many vegetation types have shown that canopy SLA is closely related to canopy leaf nitrogen (N) content and photosynthetic capacity. SLA increases as light is attenuated by leaf area down through a plant canopy, so the spatial patterns in canopy-average SLA and leaf N content should be significantly correlated with the spatial patterns in leaf area index (LAI) and canopy transmittance across an individual biome . LAI across the Oregon transect was closely related to canopy-average SLA (r2 = 0.82) and leaf N content on a mass basis (r-squared = 0.80). Canopy-average leaf N per unit area was highly correlated to canopy transmittance (r2 = 0.94) across the transect. At any given site, canopy-average SLA and leaf N per unit area do not vary significantly, either seasonally or between different codominant species occupying the same site. It is suggested that the spatial distribution of canopy-average SLA and leaf nitrogen content (and perhaps canopy photosynthetic capacity) can be predicted across biomes from satellite estimates of LAI.

Runyon, J., R.H. Waring, S.N. Goward, and J.M. Welles (1994) Environmental limits on net primary production and light-use efficiency across the Oregon transect. Ecological Applications 4, 226-237.

Summary

An extreme range in productivity, due to climate differences, occurs along a 250-km, West-East transect at about latitude 44 N in western Oregon, USA, where coniferous evergreen forests dominate. As part of the OTTER project, our objective was to evaluate how climate constrains net primary production (NPP) by limiting the utilization of intercepted photosynthetically active radiation (IPAR). The forests measured along the transect intercepted from 22% to 99.5% of the incident PAR. Using data collected from recording meteorological stations installed near each site, the hourly conditions were defined when photosynthesis was partly or completely limited by drought, extreme humidity deficits, or frost. The fraction of incident PAR that could be utilized throughout the year was calculated, ranging from 92% in the coastal rainforests to <25% in the juniper woodland. NPP varied from 300 to 2600 g/m2/yr, with the fraction of belowground NPP, estimated from litterfall, increasing from 20% to 60% of the total NPP as the environment becomes harsher. Light-use efficiency, calculated under conditions when the environment did not constrain photosynthesis, averaged 0.8 g/MJ for aboveground NPP and 1.3 g/MJ for total NPP.

Spanner, M., L. Johnson, J. Miller, R. McCreight, J. Freemantle, J. Runyon and P. Gong (1994) Remote sensing of seasonal leaf area index across the Oregon transect. Ecological Applications 4, 258-271.

Summary

We acquired remotely sensed data from four remote-sensing instruments on three different aircraft platforms over a transect of coniferous forest stands in Oregon, and analyzed them with respect to seasonal leaf area index (LAI). Data were corrected for the varying seasonal and geographic atmospheric conditions present along the transect. Strong logarithmic relationships were observed between seasonal maximum and minimum LAI and the simple ratio (SR) (near infrared/red reflectance) calculated from the broad-spectral-band Thematic Mapper Simulator (TMS), as well as from the narrow-spectral-band Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), the Compact Airborne Spectrographic Imager (CASI), and a Spectron SE590 spectro-radiometer (r2=0.82-0.97). The TMS SR reached an asymptote at an LAI of nearly 7-8. However, the SE590 and the CASI SR continued to increase up to the maximum LAI of 10.6. The variability of the relationship between the AVIRIS SR and LAI increased for stands with LAI >7, making a trend in the AVIRIS SR-LAI relationship for LAI >7 difficult to discern. The SRs of the coniferous forest stands measured by the narrow-spectral-band instruments were higher than they were from the broad-spectral-band TMS. We attributed this partially to the integration of the TMS over a broad wavelength region in the red and more strongly to calibration differences between the sensors. Seasonal TMS SR trends for four time periods for some of the stands deviated from the expected seasonal LAI trends, possibly because of smoke and very low sun angles during some of the acquisition periods. However, the expected SR differences for the seasonal minimum and maximum LAI were observed for all of the sensors for nearly all of the forest stands. We demonstrated that remotely sensed data from both broad- and narrow-spectral-band instruments can provide estimates of LAI for use in forest ecosystem simulation models to estimate evapotranspiration, photosynthesis, canopy turnover, and net primary production over large areas.

Waring, R.H. and S.W. Running (1998) Forest Ecosystems: analysis at multiple scales. Second edition, Academic Press, San Diego. 370 pp. with supplemental CD-ROM.

Terrestrial Ecosystem Model (TEM) NPP Data Set References

McGuire, A.D., J.M. Melillo, L.A. Joyce, D.W. Kicklighter, A.L. Grace, B. Moore III, and C.J. Vorosmarty (1992) Interactions between carbon and nitrogen dynamics in estimating net primary productivity for potential vegetation in North America. Global Biogeochemical Cycles 6, 101-124.

Summary

The terrestrial ecosystem model (TEM), a process-based model, was used to investigate how interactions between carbon (C) and nitrogen (N) dynamics affect predictions of net primary productivity (NPP) for potential vegetation in North America. Data on pool sizes and fluxes of C and N from intensively studied field sites were used to calibrate the model for each of 17 non-wetland vegetation types. Information on climate, soils, and vegetation was used to estimate for each of 11,299 non-wetland, 0.5° lat/long grid cells in North America. The potential annual NPP and net N mineralization (NETNMIN) of North America are estimated at 7.032 x 10^15 g C/yr and 104.6 x 10^12 g N/yr, respectively. Both NPP and NETNMIN increase along gradients of increasing temperature and moisture in northern and temperate regions of the continent, respectively. Nitrogen limitation of productivity is weak in tropical forests, increasingly stronger in temperate and boreal forests, and very strong in tundra ecosystems. The degree to which productivity is limited by the availability of N also varies within ecosystems. Spatial resolution in estimating exchanges of C between the atmosphere and the terrestrial biosphere is improved by modeling the linkage between C and N dynamics. A factorial experiment was performed with TEM on temperate mixed forest in North America to evaluate the importance of considering interactions between C and N dynamics in the response of NPP to an elevated temperature of 2° C. Uncoupling the C cycle from the N cycle caused NPP to decrease primarily because of higher plant respiration. NPP increased with the C and N cycles coupled because productivity that is due to increased N availability more than offsets the higher costs of plant respiration. Process-based models need to consider linkages between the C and N cycles in order to investigate how global change will affect biosphere-atmosphere interactions.

Melillo, J.M., A.D. McGuire, D.W. Kicklighter, B. Moore, C.J. Vorosmarty, and A.L. Schloss (1993) Global climate-change and terrestrial net primary production. Nature 363, 234-240.

Summary

Global patterns of net primary production (NPP) and soil nitrogen (N) cycling were estimated using a process-based model for contemporary climate conditions and current atmospheric CO2 concentration. More than 50% of global annual NPP was estimated to occur in the tropics, with most of this attributable to tropical evergreen forest. The effects of CO2 doubling and associated climate changes were also explored. Responses in tropical and dry temperate ecosystems were dominated by CO2, whereas those in northern and moist temperate ecosystems reflected the effects of temperature on N availability.

Pan, Y., A.D. McGuire, D.W. Kicklighter, and J.M. Melillo (1996) The importance of climate and soils for estimates of net primary production: a sensitivity analysis with the terrestrial ecosystem model. Global Change Biology 2, 5-23.

Summary

The Terrestrial Ecosystem Model (TEM) was used to investigate how alternative input data sets of climate (temperature/precipitation), solar radiation, and soil texture affect estimates of net primary productivity (NPP) for the conterminous United States. At the continental resolution, the climates of Cramer and Leemans (C&L) and of the Vegetation/ Ecosystem Modelling and Analysis Project (VEMAP) represent cooler and drier conditions for the United States in comparison to the Legates and Willmott (L&W) climate, and cause 5.2% and 2.3% lower estimates of NPP. Solar radiation derived from C&L and given in VEMAP is 32% and 60% higher than the solar radiation data derived from Hahn cloudiness. These differences result in 8-10% lower NPP because of radiation-induced water stress. In comparison to the FAO/CSRC soil texture, which represents most biomes with loam soils, the soil textures are finer (more silt and clay) in the Zobler and VEMAP data sets. The use of VEMAP soil textures instead of FAO/CSRC soil textures causes about 3% higher NPP because enhanced volumetric soil moisture results in higher rates of nitrogen cycling, but use of the Zobler soil textures has little effect. Overall, NPP estimates of TEM are more sensitive to alternative data sets at the biome and grid cell resolutions than at the continental resolution. At all spatial resolutions, the sensitivity of NPP estimates represents the impact of uncertainty among the alternative data sets we used in this study. Input data sets need to reduce their uncertainty to improve the spatial resolution of NPP estimates by process-based ecosystem models. This is especially important for improving assessments of the regional impacts of global change.