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With the analytical tool, Frankfurt Harvested Wood Products Model, FPM, the carbon stocks and carbon stock changes of Harvested Wood Products, HWP, either in USE or in LANDFILLS L-F, have been evaluated, each separately, from the readily available statistical data base of the FAO, FAOSTAT, on the wood commodities: “Sawnwood and Wood-based Panels, SWP” and the paper commodities, “Paper and Paperboard, PAP”. The focus was on the newly founded Asia-Pacific Partnership countries for Clean Development and Climate (in short AP6), including Canada, which wants to join the AP6, in relation to the countries of the European Union EU-25. It could be shown that the stocks and stock changes of the HWP in USE follow a simple algorithm of the annual consumption or production and their mean annual growth, for the categories SWP and PAP, provided the mean residence times of the HWP in USE can be estimated. With the information on the fraction of residues entering the landfills and their estimated residence times an equivalent simple expression has been derived for stocks and stock changes of the HWP in LANDFILLS L-F. Their values have been calculated to be approximately 0.5 to 0.7 times smaller than those of the HWP in USE. Still, all stock changes of the HWP in L-F were positive and thus accumulating carbon. However, when methane outgasing within the HWP in L-F had been considered, the calculated Greenhouse Gas Balance was zero or negative under the estimated parameters thus to at least partly compensate the positive storage of carbon in HWP in USE. The percentage of CO2 removed by the HWP in USE in comparison to the annual greenhouse gas emissions varied from 0.3 to 1.7%, with a mean value of 0.8% for the AP6 countries including Canada, in contrast to 1.0% of the EU-25 countries. Despite of the relative small magnitude in relation to the total emission of all GHG this contribution should not be neglected in the GHG Budget of a country.

With the analytical tool: Frankfurt Harvested Wood Products (HWP) Model, carbon stocks and carbon stock changes of HWP, either in USE or in LANDFILLS, have been evaluated from the readily available statistical data base of the FAO, FAOSTAT, on the wood commodities: “Sawnwood and Wood-based Panels” and the paper commodities: “Paper and Paperboard”. Essential differences have been found between the individual 15 EU countries in the comparison of the Stock Change Approach and the Production Approach, as well as in the comparison of the stock changes of HWP with the National Greenhouse Gas (GHG) budgets. The stock changes for the HWP in USE within the EU-15 Community have been calculated to be 10.83 Mt C/a (39.71 Mt CO2/a) based on the Stock Change Approach and 9.81 Mt C/a (35.97 Mt CO2/a) for the Production Approach, respectively. These numbers can be compared to the total GHG Inventory of the EU-15 of 4,095 Mt CO2 equivalents, including all six Kyoto gases, which shows that the carbon sequestration of HWP in USE is of the order of 1% relative to GHG Inventory. The GHG balance for the carbon stock changes of HWP in LANDFILLS is of similar magnitude as for the HWP in USE, and therefore a sink when methane outgasing is disregarded. However, when methane outgasing is considered, which is formed as a 1:1 mixture with CO2 under the prevailing anaerobic conditions the GHG balance results in minus 10.0 Mt C equivalent/a and minus 10.6 Mt C equivalent/a for the Stock Change Approach and the Production Approach under the parameters chosen in this study.

We compared the simulated responses of net primary production, heterotrophic respiration, net ecosystem production and carbon storage in natural terrestrial ecosystems to historical (1765 to 1990) and projected (1990 to 2300) changes of atmospheric CO2 concentration of four terrestrial biosphere models: the Bern model, the Frankfurt Biosphere Model (FBM), the High-Resolution Biosphere Model (HRBM) and the Terrestrial Ecosystem Model (TEM). The results of the model intercomparison suggest that CO2 fertilization of natural terrestrial vegetation has the potential to account for a large fraction of the so-called "missing carbon sink" of 2.0 Pg C in 1990. Estimates of this potential are reduced when the models incorporate the concept that CO2 fertilization can be limited by nutrient availability. Although the model estimates differ on the potential size (126 to 461 Pg C) of the future terrestrial sink caused by CO2 fertilization, the results of the four models suggest that natural terrestrial ecosystems will have a limited capacity to act as a sink of atmospheric CO2 in the future as a result of physiological constraints and nutrient constraints on NPP. All the spatially explicit models estimate a carbon sink in both tropical and northern temperate regions, but the strength of these sinks varies over time. Differences in the simulated response of terrestrial ecosystems to CO2 fertilization among the models in this intercomparison study reflect the fact that the models have highlighted different aspects of the effect of CO2 fertilization on carbon dynamics of natural terrestrial ecosystems including feedback mechanisms. As interactions with nitrogen fertilization, climate change and forest regrowth may play an important role in simulating the response of terrestrial ecosystems to CO2 fertilization, these factors should be included in future analyses. Improvements in spatially explicit data sets, whole-ecosystem experiments and the availability of net carbon exchange measurements across the globe will also help to improve future evaluations of the role of CO2 fertilization on terrestrial carbon storage. [References: 92]

Within the global carbon cycle the world's ecosystems are the most sensitive part with respect to environmental change. Seasonal changes in the atmospheric CO₂ content provide important clues to the understanding of the carbon exchange fluxes, which determine the global carbon budget. We developed the Frankfurt Biosphere Model (FBM) in order to simulate e.g. the seasonal course of net primary productivity and phenology of 32 vegetation types of the terrestrial biosphere given by a modified Matthews (1983) map of potential vegetation. In a spatial resolution of 0.5° by 0.5° grid the model calculates gross photosynthesis and autotrophic respiration on an hourly time step and heterotrophic respiration as well as the carbon pool sizes on a daily time step. The driving variables temperature, irradiation, and precipitation are derived from the Cramer and Leemans (1994) climate database. Soil moisture is calculated by a bucket model depending on FAO soil properties and rooting depth. We present and discuss here the global results of Net Primary Productivity calculated as balance of gross photosynthesis minus autotrophic respiration., Productivité primaire nette des écosystèmes terrestres selon le «Frankfurt Biosphere Model» (FBM) Dans le cycle global du carbone, les écosystèmes constituent le maillon le plus sensible aux changements environnementaux. Les variations saisonnières de CO₂ atmosphérique offrent des indices importants pour la compréhension des flux de carbone échangés qui conditionnent le bilan global. Nous avons développé le «Frankfurt Biosphere Model» (FBM) afin de simuler, par exemple, l'évolution saisonnière de la Productivité Primaire Nette (PPN) et la phénologie de 32 types de végétation selon une version modifiée de la carte de végétation potentielle de Matthews (1983). Le modèle calcule la photosynthèse brute et la respiration autotrophe à la résolution de 0,5° par 0,5° toutes les heures, et actualise quotidiennement la taille de chaque réservoir de carbone. Les variables d'entrée que sont la température, le rayonnement solaire incident et les précipitations sont issues de la base de données climatologiques de Cramer et Leemans (1994). L'humidité du sol est calculée à partir d'un modèle de réservoirs utilisant des profondeurs racinaires et d'autres propriétés pédologiques issues de la base de données de la FAO. Dans cet article, nous présentons et discutons les résultats de PPN globale, bilan entre la photosynthèse brute et la respiration autotrophe., Dönges Silke, Ramge Peter, Lüdeke Matthias K.B., Badeck Franz W., Otto Ralf D., Häger Christof, Kindermann Jürgen, Würth Gudrun, Lang Torsten, Jäkel Ulrich, Nadler Andreas, Habermehl Stefan, Kohlmaier Gundolf H. Net primary production of terrestrial ecosystems as evaluated by the Frankfurt biosphere model (FBM). / Productivité primaire nette des écosystèmes terrestres selon le «Frankfurt Biosphere Model » (FBM). In: Sciences Géologiques. Bulletin, tome 50, n°1-4, 1997. The global carbon cycle in the terrestrial biosphere, sous la direction de Gérard Dedieu et Jean-Luc Probst. pp. 59-71.

A global prognostic physiologically based model of the carbon budget in terrestrial ecosystems, the Frankfurt Biosphere Model (FBM), is applied to simulate the interannual variation of carbon exchange fluxes between the atmosphere and the terrestrial biosphere. The data on climatic forcing are based on Cramer and Leemans climate maps; the interannual variation is introduced according to records of temperature anomalies and precipitation anomalies for the period 1980 to 1993. The calculated net exchange flux between the atmosphere and the terrestrial biosphere is compared to the biospheric signal deduced from 13 C measurements. Some intermediate results are presented as well: the contributions of the most important global ecosystems to the biospheric signal, the contributions of different latitudinal belts to the biospheric signal, and the responses of net primary production (NPP) and heterotrophic respiration (R h ). From the simulation results it can be inferred that the complex temperature and precipitation responses of NPP and R h in different latitudes and different ecosystem types add up to a global CO 2 signal contributing substantially to the atmospheric CO 2 anomaly on the interannual timescale. The temperature response of NPP was found to be the most important factor determining this signal.

An algorithm based on a three-spline function fitted to measured NDVI courses (normalized difference vegetation index) was developed to analyze a given NDVI annual course with respect to leaf shooting and leaf abscission times of deciduous vegetation. In contrast to algorithms which are based on modified second derivatives of the NDVI time course to detect shooting or abscission, the proposed algorithm takes into account the whole annual time course and is therefore less sensitive to noise in the NDVI-signal. In the present study this algorithm was used to validate the phenology results for the deciduous vegetation of a global equilibrium run of the prognostic Frankfurt Biosphere Model (FBM, spatial resolution 0.5° × 0.5°) driven by a climatology which represents a mean seasonality of the driving variables. The mean value of the area-weighted frequency distribution of the difference between the shooting date deduced from NDVI and the shooting date calculated by the FBM for the deciduous vegetation types is −4 days, indicating that in the global mean the FBM predicts leaf shooting less than one week too late. A 75% fraction of the area under consideration shows predicted shooting dates lying within a range of ± 30 days compared to the satellite-derived dates. The distribution has its maximum at a difference of 0 days (i.e. the FBM exactly fits the NDVI deduced shooting day for these areas). This result supports the general assumption that at least in global scale models phenology can be successfully deduced from carbon flux balance considerations.

In this contribution, we perform a case study of the German forests. We couple the Frankfurt biosphere model (FBM) with a model of the age class development (AGEDYN). The coupled model is applied to simulate the temporal development of carbon pools in German forests under the influence of climate change taking into account changes in the age class structure. In the base case, the growth of forest stands is simulated using a temporally averaged climate dataset, being representative for the contemporary climate conditions. To assess the sensitivity of forest growth to changes in environmental conditions, the FBM is run in several scenarios. In these simulations the effects both of climate change and of the direct effect of increased levels of atmospheric CO 2 on photosynthesis (CO 2 fertilization) on forest growth are assessed. In another simulation run with the FBM both effects — climate change and CO 2 fertilization — are combined. In simulations under present day's climate conditions a good agreement is gained between simulation results and statistical data of the present standing stock carbon density of Germany's forests. A pure climate change leads to a decrease of the annual increments as well as to the climax standing stocks. The negative effect of climate change alone is overcompensated by enhanced photosynthesis in the simulations with combined climate change and CO 2 fertilization. In the transient case, the coupled model is used in two scenarios describing first a continuation of present day's climate conditions and second a transient climate change from present conditions (1990) to 2 × CO 2 conditions in 2090. Here, the simulations indicate that changes in the forest's age class structure can have a stronger influence on the future carbon balance of the forests in the considered region than the combined efffect of climate change and CO 2 fertilization. DOI: 10.1034/j.1600-0889.1999.00019.x

To assess the role of the boreal and temperate forests and the tundra ecosystems in a future CO2-induced climate change, the Frankfurt biosphere model (FBM) was applied to the 3 × CO2 climate as calculated by the GCM of the MPI für Meteorologie in Hamburg. The FBM predicts on a 1° × 1° spatial grid the seasonal and perannual course of leaf biomass and feeder roots, woody biomass, soil carbon and soil water in response to the seasonal course of light, precipitation and temperature. The phenology is controlled by the flux balance of carbon gains and losses, thus being dependent on the driving climate and the state of vegetation. Two equilibrium runs based on the 3 × CO2 climate were performed: (1) Considering the pure climate effect (with no direct CO2 fertilization) we obtained a 22% decrease of the net primary production (NPP) due to enhanced autotrophic respiration and increased water limitation. Together with the effect on the soils this results in a 170 Gt carbon source. (2) Considering a CO2 -induced enhancement of the maximum photosynthesis the pure climate effect is more than compensated and we predict a NPP increase of 9% and a total carbon sink of 50 Gt C. This effect may even be an underestimate if one takes into consideration a shift in the optimum temperature for photosynthesis under enhanced levels of atmospheric CO2 as proposed by Long and Drake.DOI: 10.1034/j.1600-0889.47.issue1.16.x

The rôle of the temperate and boreal forests as a global CO2 source or sink is examined, both for the present time and for the next hundred years. The results of the Forest Resource Assessment for 1990 of the Economic Comission for Europe and the Food and Agricultural Organisation of the United Nations (1992) serve as the main database in this study. Out of the estimated total area of approximately 20 • 106 km2 of forests and wooded lands in the temperate and boreal zone only approximately fifty percent is documented within the category of exploitable forests, which are examined in detail here. In this study, a general formalism of the time evolution of an ensemble of forests within an ecological province is developed using the formalism of the Leslie matrix. This matrix can be formulated if the age class dependent mortalities which arise from the disturbances are known. A distinction is made between the natural disturbances by fire, wind throw and insect infestations and disturbances introduced through harvesting of timber. Through the use of Richards growth function each age class of a given biome is related to the corresponding biomass and annual increment. The data reported on the mean net annual increment and on the mean biomass serve to calibrate the model. The difference of the reported net annual increment and annual fellings of approximately 550 • 106 m3 roundwood correspond to a sink of 210-330 Mt of carbon per year excluding any changes in the soil balance. It could be shown that the present distribution of forest age classes for the United States, Canada, Europe, or the former Soviet Union does not correspond to a quasi-stationary state, in which biomass is accumulated only due to a stimulated growth under enhanced atmospheric CO2 levels. The present CO2 sink function will not persist in the next century, if harvesting rates increase with 0.5% annually or even less. The future state will also be influenced by the effect of the greenhouse climate, the impact of which may range from a stimulating effect on growth, which is calculated by the Frankfurt biosphere model, up to a transitional negative effect through a shift in vegetation zones.DOI: 10.1034/j.1600-0889.47.issue1.18.x

SUMMARY Uptake of NO2 via stomata and its elimination in the mesophyll are investigated by use of mathematical models. Systems of differential equations describe simultaneous diffusion and reaction of the chemical species taken into account. The common hypothesis, postulating the disproportionation reaction of NO2 being the predominant path for the transformation of NO2 into the cellular nitrate and nitrite pools, could be false because of its failure to reproduce the measured sorption characteristics. If however the reduction of the pro-oxidative NO2 by apoplastic ascorbate is taken into account the calculated uptake rates and the effects of changes in immission concentration and vegetational characteristics fit well within corresponding experimental results. The onset of acute injury in case of a fall in apoplastic ascorbate concentration below a critical level is postulated.

Points out that differences in the background of the working population, are often made responsible for the observed inequality of income distribution. Explores whether the observed distribution in incomes in countries such as the Federal Republic of Germany (West and East), Great Britain, Sweden, the United States and Brazil could not be the result of a statistical distribution process in which households participate. Recalls the early work in statistical thermodynamics by Boltzmann and Maxwell, who studied the distribution of energy among an ensemble of identical molecules, and which showed that not all molecules hold the same energy, but rather that the distribution has an exponential fall‐off character, with most molecules being in the lower energy bracket. Adapts the Maxwell‐Boltzmann distribution to incomes, and transforms these distributions into well‐known Lorenz graphs, and obtains a perfect match for each examined country. Suggests that, as the distributions can be directly related to their corresponding statistical weights, and as their logarithms are proportional to entropy in statistical thermodynamics, it could be shown that the unequal income distribution has a higher entropy, and therefore is more stable than the corresponding low entropy distribution resulting from Boulding′s principle of equal advantage where all households earn the same income. Supposes that neither of the two extreme stand‐points to explain the inequality of incomes can lead to a totally satisfactory explanation. Proposes that evolutionary strategies may be an interesting lead to follow up in more detail.

The uptake rates of dissolved pollutants in an aquatic environment by fish are frequently characterized by their corresponding ventilation efficiency ϵ of the gill organ. Many lipophilic organic chemicals with a n-octanol-water partition coefficient log Kow = 2–7 have efficiencies as high as between 25% and 100%. Conventional ‘inert’ mass exchange models, also in the flow limiting case (neglecting the transbarrier diffusive resistance), predict very low ventilation efficiencies (5–15%) at given physiological conditions. However, an enhancement of mass transfer across the gill barrier can be described by postulating a rapid and effective binding of pollutants with plasma proteins, such as albumin-like and lipoprotein fractions. This assumption is in agreement with pharmacological experience, where a certain lipophilicity of a drug or metabolite is required for a high degree of protein binding. The effects on ϵ by incorporating a linear binding curve for the pollutant/plasma protein interaction into the so-called countercurrent model (model I) and the arterial well-stirred model (model II) have been studied in detail. Experimentally found correlations between the ventilation efficiency and the n-octanol-water partition coefficient (obtained by direct measurements of the transport rates of the chemicals across the gills of rainbow trout) are quantitatively well described by our models. Model II is also studied analytically by considering the non-linear effects on ϵ resulting from a binding curve described by a one-term, Langmuir-type equation.

There is general agreement that terrestrial systems in the Northern Hemisphere provide a significant sink for atmospheric CO2; however, estimates of the magnitude and distribution of this sink vary greatly. National forest inventories provide strong, measuretment-based constraints on the magnitude of net forest carbon uptake. We brought together forest sector C budgets for Canada, the United States, Europe, Russia, and China that were derived from forest inventory information, allometric relationships, and supplementary data sets and models. Together, these suggest that northern forests and woodlands provided a total sink for 0.6-0.7 Pg of C per year (1 Pg = 10(15) g) during the early 1990s, consisting of 0.21 Pg C/yr in living biomass, 0.08 Pg C/yrin forest products, 0.15 Pg C/yr in dead wood, and 0.13 Pg C/yr in the forest floor and soil organic matter. Estimates of changes in soil C pools have improved but remain the least certain terms of the budgets. Over 80% of the estimated sink occurred in one-third of the forest area, in temperate regions affected by fire suppression, agricultural abandonment, and plantation forestry. Growth in boreal regions was offset by fire and other disturbances that vary considerably from year to year. Comparison with atmospheric inversions suggests significant land C sinks may occur outside the forest sector.

For the period 1980–89, we estimate a carbon sink in the coterminous United States between 0.30 and 0.58 petagrams of carbon per year (petagrams of carbon = 10 15 grams of carbon). The net carbon flux from the atmosphere to the land was higher, 0.37 to 0.71 petagrams of carbon per year, because a net flux of 0.07 to 0.13 petagrams of carbon per year was exported by rivers and commerce and returned to the atmosphere elsewhere. These land-based estimates are larger than those from previous studies (0.08 to 0.35 petagrams of carbon per year) because of the inclusion of additional processes and revised estimates of some component fluxes. Although component estimates are uncertain, about one-half of the total is outside the forest sector. We also estimated the sink using atmospheric models and the atmospheric concentration of carbon dioxide (the tracer-transport inversion method). The range of results from the atmosphere-based inversions contains the land-based estimates. Atmosphere- and land-based estimates are thus consistent, within the large ranges of uncertainty for both methods. Atmosphere-based results for 1980–89 are similar to those for 1985–89 and 1990–94, indicating a relatively stable U.S. sink throughout the period.

Strategies are developed to analyze and represent spatially resolved biosphere models for carbon sequestration in response to changes in atmospheric CO2 and climate by reduced-form, substitute models. We explore the High-Resolution Terrestrial Biosphere Model as implemented in the Community Terrestrial Biosphere Model (HRBM/CTBM), the Frankfurt Biosphere Model (FBM), and the box-type biosphere of the Bern model. Storage by CO2 fertilization is described by combining analytical representations of (1) net primary productivity (NPP) as a function of atmospheric CO2 and (2) a decay impulse response function to characterize the timescales of biospheric carbon turnover. Storage in response to global warming is investigated for the HRBM/CTBM. The relation between the evolution of radiative forcing and climate change is expressed by a combination of impulse response functions and empirical orthogonal functions extracted from results of the European Center/Hamburg (ECHAM3) coupled atmosphere-ocean general circulation model. A box-type, differential-analogue substitute model is developed to represent global carbon storage of the HRBM/CTBM in response to regional changes in Temperature, Precepitation and cloud cover. The substitute models represent the spatially resolved models accurately and cost-efficiently for carbon sequestration in response to changes in CO2 or in CO2 and climate and for simulations of the global isotopic signals. Deviations in carbon uptake simulated by the spatially resolved models and their substitutes are less than a few percent.

The Frankfurt Biosphere Model (FBM), a mechanistic and prognostic compartment model of the terrestrial biosphere, has been developed to simulate global carbon exchange fluxes between terrestrial vegetation and the atmosphere with a spatial resolution of 0.5° × 0.5°. The FBM also offers the opportunity to simulate either interannual fluctuations of carbon exchange fluxes or the long-term development of the vegetation under the influence of climate change.

Results of an intercomparison among terrestrial biogeochemical models (TBMs) are reported, in which one diagnostic and five prognostic models have been run with the same long-term climate forcing. Monthly fields of net ecosystem production (NEP), which is the difference between net primary production (NPP) and heterotrophic respiration R-H, at 0.5 degrees resolution have been generated for the terrestrial biosphere, The monthly estimates of NEP in conjunction with seasonal CO2 flux fields generated by the seasonal Hamburg Model of the Oceanic Carbon Cycle (HAMOCC3) and fossil fuel source fields were subsequently coupled to the three-dimensional atmospheric tracer transport model TM2 forced by observed winds. The resulting simulated seasonal signal of the atmospheric CO2 concentration extracted at the grid cells corresponding to the locations of 27 background monitoring stations of the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory network is compared with measurements from these sites. The Simple Diagnostic Biosphere Model(SDBM1), which is tuned to the atmospheric CO2 concentration at five monitoring stations in the northern hemisphere, successfully reproduced the seasonal signal of CO2 at the other monitoring stations. The SDBM1 simulations confirm that the north-south gradient in the amplitude of the atmospheric CO2 signal results from the greater northern hemisphere land area and the more pronounced seasonality of radiation and temperature in higher latitudes. In southern latitudes, ocean-atmosphere gas exchange plays an important role in determining the seasonal signal of CO2. Most of the five prognostic models (i.e., models driven by climatic inputs) included in the intercomparison predict in the northern hemisphere a reasonably accurate seasonal cycle in terms of amplitude and, to some extent, also with respect to phase. In the tropics, however, the prognostic models generally tend to overpredict the net seasonal exchanges and stronger seasonal cycles than indicated by the diagnostic model and by observations. The differences from the observed seasonal signal of CO2 may be caused by shortcomings in the phenology algorithms of the prognostic models or by not properly considering the effects of land use and vegetation fires on CO2 fluxes between the atmosphere and terrestrial biosphere. [References: 80]

For the analyzed period between 1980 and 1989 a terrestrial biospheric sink of the order of 1.7 to 1.8 Gt C per year is required to close the CO2 budget between atmospheric CO2 input, observed atmospheric CO2 increase, CO2 ocean uptake and CO2 release from deforestation. The reasons for the additional terrestrial sink are still not completely clarified, however, the fertilization through additional atmospheric CO2 and deposition of nitrogen compounds are believed to be of importance in addition to factors associated with climate change, age class distribution of forests as well as land management practices. The IPCC (Intergovernmental Panel on Climate Change) has generated a series of atmospheric CO2 profiles leading to stabilization levels in the range 350 to 1000 ppmV. These profiles correspond to developments with very strong efforts, intermediate efforts, or nearly absent (at least during the next 30 to 50 years) efforts to stabilize greenhouse gases. In the present study, we examine the CO2 exchange between the land biota and the atmosphere studying in particular the long term development of a potential CO2 related fertilization effect for the profiles stabilizing atmospheric CO2 at 450 (S450), 650 (S650) and 1000 (S1000) ppmV. Two different biosphere box models, an ultra-simple two-box model (USBM) and the Bern four-box biosphere model as well as the high-resolution Frankfurt Biosphere Model (FBM) were investigated to study the long-term response (up to the year 2300) of the biota and soils.

Uptake of NO2 and ozone via stomata and their elimination in the mesophyll were investigated using mechanistic mathematical models. The common hypotheses, postulating the disproportionation reaction of NO2 being the predominant path for the transformation of NO2 into the cellular nitrate and nitrite pools, could be falsified because it fails to reproduce the sorption characteristics as determined experimentally. If, however, the reduction of the pro-oxidative NO2 by apoplastic ascorbate is taken into account the calculated uptake rates and the effects of changes in immission concentration and vegetation characteristics fit well within corresponding experimental results. The onset of acute injury in case of a fall in apoplastic ascorbate concentration below a critical level is postulated.

The response of the vegetation and soils of the higher latitude forests and tundra ecosystems to an anticipated climate change is investigated using two alternative approaches to calculate the resulting change in the total carbon content (TCC) of the vegetation and the soils: On the one hand a BGC (bio-geochemicalcycle) model, in this case the FBM (Frankfurt Biosphere Model), where the ecosystem response is entirely due to the ecophysiological response of the vegetation and the ecological response of the soils. On the other hand a biome or “rule-based” model, in this case the BIOME model, which allows for the determination of the occurrence of a specific biome type from a given climatic situation assuming equilibrium conditions. Within the FBM prognosis net primary production and TCC are reduced both for needle leaved and broad leaved forests if the CO2-fertilisation effect is not taken into account. When the CO2-fertilisation effect is taken into consideration NPP, standing biomass and soil carbon are increased in a future greenhouse climate. Although there is a considerable shift of the biomes in response to the greenhouse climate within the BIOME approach, the TCC in the investigated northern biomes stayed more or less constant. This is due to a decrease in biomass in the southern regions of today’s temperate forests compensating the biomass increase by the northward shift of the taiga border.

Carbon exchange fluxes of terrestrial ecosystems are expected to depend on the internal dynamics of C stocks in vegetation and soils, on nutrient availability, and on the local climatic conditions / weather. The model structure which we present focuses on the internal dynamics in the living vegetation. The mathematical description is derived from two basic hypotheses: 1) vegetation tends to maximize photosynthesizing tissue, and 2) the relative amounts of C in pools with relatively short and long turnover times are given by allometric relations. The model can be calibrated for any vegetation type in a typical climate under the condition to meet mean ecological estimates of e.g. biomass and NPP. For C cycle modeling the FBM yields the net CO2 flux between the grid elements and the atmosphere in a daily resolution. It is demonstrated that simulations with a 1°x1° spatial resolution reproduce the response of the time course of C fluxes to local climates.

This paper focusses on the significance of the land biota and their role as a source or sink of atmospheric CO2 in a changing world. We would like to address three areas of concern.

The role of the temperate and boreal forests as a global CO 2 source or sink is examined, both for the present time and for the next hundred years. The results of the Forest Resource Assessment for 1990 of the Economic Comission for Europe and the Food and Agricultural Organisation of the United Nations (1992) serve as the main database in this study. Out of the estimated total area of approximately 20 • 10 6 km 2 of forests and wooded lands in the temperate and boreal zone only approximately fifty percent is documented within the category of exploitable forests, which are examined in detail here. In this study, a general formalism of the time evolution of an ensemble of forests within an ecological province is developed using the formalism of the Leslie matrix. This matrix can be formulated if the age class dependent mortalities which arise from the disturbances are known. A distinction is made between the natural disturbances by fire, wind throw and insect infestations and disturbances introduced through harvesting of timber. Through the use of Richards growth function each age class of a given biome is related to the corresponding biomass and annual increment. The data reported on the mean net annual increment and on the mean biomass serve to calibrate the model. The difference of the reported net annual increment and annual fellings of approximately 550 • 10 6 m 3 roundwood correspond to a sink of 210-330 Mt of carbon per year excluding any changes in the soil balance. It could be shown that the present distribution of forest age classes for the United States, Canada, Europe, or the former Soviet Union does not correspond to a quasi-stationary state, in which biomass is accumulated only due to a stimulated growth under enhanced atmospheric CO 2 levels. The present CO 2 sink function will not persist in the next century, if harvesting rates increase with 0.5% annually or even less. The future state will also be influenced by the effect of the greenhouse climate, the impact of which may range from a stimulating effect on growth, which is calculated by the Frankfurt biosphere model, up to a transitional negative effect through a shift in vegetation zones. DOI: 10.1034/j.1600-0889.47.issue1.18.x

To assess the role of the boreal and temperate forests and the tundra ecosystems in a future CO 2 -induced climate change, the Frankfurt biosphere model (FBM) was applied to the 3 × CO 2 climate as calculated by the GCM of the MPI fur Meteorologie in Hamburg. The FBM predicts on a 1° × 1° spatial grid the seasonal and perannual course of leaf biomass and feeder roots, woody biomass, soil carbon and soil water in response to the seasonal course of light, precipitation and temperature. The phenology is controlled by the flux balance of carbon gains and losses, thus being dependent on the driving climate and the state of vegetation. Two equilibrium runs based on the 3 × CO 2 climate were performed: (1) Considering the pure climate effect (with no direct CO 2 fertilization) we obtained a 22% decrease of the net primary production (NPP) due to enhanced autotrophic respiration and increased water limitation. Together with the effect on the soils this results in a 170 Gt carbon source. (2) Considering a CO 2 -induced enhancement of the maximum photosynthesis the pure climate effect is more than compensated and we predict a NPP increase of 9% and a total carbon sink of 50 Gt C. This effect may even be an underestimate if one takes into consideration a shift in the optimum temperature for photosynthesis under enhanced levels of atmospheric CO 2 as proposed by Long and Drake. DOI: 10.1034/j.1600-0889.47.issue1.16.x

An algorithm is developed to calculate the seasonal carbon exchange flux between the living parts of the vegetation and the atmosphere by using monthly time series of NDVI satellite data, air temperature and photosynthetically active radiation. The algorithm is based on already-existing models of the optical and physiological properties of the plant cover, introducing the concept of a seasonally variable green cover and considering some primary plant processes driven by climatic variables. The resulting carbon flux is compared to fluxes obtained by simpler models for one example pixel in Northern Germany during a period of 2 years, showing significant differences in timing and shape. In addition, the seasonal carbon exchange rate measured for beech trees is compared with the corresponding flux derived from the proposed model. DOI: 10.1034/j.1600-0889.1991.00012.x

We agree with Idso that CO2 fertilization of terrestrial ecosystems is of great importance in the understanding of the behaviour of the amplitude of the seasonal cycle of atmospheric CO2 as analyzed in our paper (Kohlmaier et al., 1989, henceforth called II). DOI: 10.1034/j.1600-0889.1991.t01-1-00008.x

In this contribution we try to give a synopsis of the more important processes within the global C cycle. Special attention is paid to the mechanisms by which atmospheric CO2 is interchanged between the biosphere and the oceans, and existing qualitative and quantitative uncertainties are pointed out.

The authors present classical computations for V to T energy transfer of highly vibrationally excited Morse diatomics in Cinfinity collisions with atoms, assuming a pure exponential interaction. Phase-averaged energy transfer over a wide range of mass distributions and initial energies have been obtained. Effects of 'excluded' phase angles, 'double' impacts and vibrational enhancement of inhibition on de-activational efficiency were studied. Some new analytical results are also presented.

A simple classical phenomenological Markoffian damping model for the collisional T-V energy transfer of a gas atom impinging on a “surface”-atom of a polyatomic molecule or a solid lattice surface is proposed. The relevant dynamical features of the polyatomic system, projected onto the collisional axis, are taken to be reduced to a local (surface oscillator) and to a dissipating (damping) part. In the context of a new approximate renormalizing procedure for the calculation of T-V energy transfer, analytical results were derived for the case of a intermolecular Morse potential in a wide velocity range. We have shown that the existence of a V-V intramolecular dissipative mechanism can strongly influence the velocity dependence on the energy transfer. Different effects due to the intermolecular dissipating forces were observed for the energy transfer in the impulsive and languid collisional regime. Mit Hilfe eines phanomenologischen klassischen Markoffschen Dissipations-Modells wird die T-V-Stosenergieubertragung zwischen einem Gasatom und einem “Oberflachenatom” eines vielatomigen Molekuls oder einer Festkorperoberflache beschrieben. Dabei werden die wesentlichen, auf die Stosachse projizierten, dynamischen Eigenschaften des vielatomigen Systems in einen lokalen (Oberflachenoszillator) und in einem innermolekularen dissipativen (Dampfung) Anteil zerlegt. In diesem Zusammenhang wird ein neues Naherungs-verfahren der Renormierung zur Berechnung der T-V-Energieubertragung vorgeschlagen, wobei analytische Ergebnisse fur den Fall einer zwischenmolekularen Morse-Wechselwirkung uber einen weiten Geschwindigkeitsbereich erhalten wurden. Wir konnten zeigen, das durch die intramolekulare V-V-Energieubertragung, beschrieben durch den Dissipationsmechanismus, die Geschwindigkeitsabhangigkeit der T-V-Energieubertragung stark beeinflust wird. Die zusatzliche Dampfung fuhrte fur verschiedene Stoszeitbereiche zu unterschiedlichen dynamischen Effekten.

A model of the seasonal and long-term carbon dynamics of temperature deciduous forests and tropical broadleaved evergreen forests in response to variations of the climatic parameters light intensity and air temperature, is proposed in order to be able to assess the influence of (future) climatic change on vegetation. The driving variables operate upon carbon assimilation and respiration of a two-compartment model of living biomass. The model allocation of assimilates depends on the developmental stage of the living biomass and on the climatic variables, without prescribing the time course of the phenophases explicitly. Almost all model parameters can be interpreted in terms of measurable physiological/ecological quantities, restricting the parameter values to a limited range. Measured growth dynamics and annual CO2 fluxes for a non-seasonal tropical forest and two different temperate deciduous forest stands are reproduced satisfactorily.

Eine analytische Behandlung des Kohlenstoffaustauschs zwischen der Atmosphare und der Oberflachenschicht des Meeres sowie zwischen dieser und der Tiefsee wird vorgestellt. Anhand der daraus gewonnenen Ergebnisse wird diskutiert, inwieweit die Festlandbiota (im Rahmen der bisher konstruierten Ozeanmodelle) als Quelle oder als Senke fur zusatzliches atmospharisches CO2 in Frage kommen. Auserdem werden die Auswirkungen verschiedener Szenarien des fossilen Kohlenstoffinputs auf den CO2-Gehalt der Atmosphare fur die nachsten Jahrzehnte abgeschatzt. An analytical treatment of carbon exchange processes between the atmosphere and the surface layer of the oceans as well as between the latter and the deep sea is presented. With the results obtained it is discussed to which extent the terrestrial biota may as a source or a sink for additional atmospheric CO2 (within the framework of hitherto constructed ocean models). An assessment is made of the effect of different scenarios for the fossil carbon inbut on the CO2 content of the atmosphere for the coming decades.

Marine transport of inorganic and organic carbon is simulated by means of a computer model in which the oceans are divided into a high and low latitude region. Water transport (and with it carbon transport) is reproduced 1) as downwelling of surface waters at low latitudes, and 2) in general, as different depth-dependent turbulent diffusion in both deep-sea regions. The model is calibrated with pre-bomb 14C and validated against perturbations of total carbon, 13C/C- and 14C/C-ratios; it is compatible with carbon release from fossil fuels and from biogenic sources.

Gegenwartig ist die Rolle der Landbiota als Quelle oder Senke fur atmospharisches CO2 und ihre Veranderung innerhalb des globalen C-Zyklus umstritten [1–4]. In unserem Ansatz beschreiben wir die autonome, vom Menschen unbeeinfluste Dynamik eines bestimmten Teilsystems (z. B. Biosphare Land) als die Differenz einer Input- und Outputrate von im allgemeinen nicht-linearer Struktur und unterscheiden uns damit von konventionellen linearen Ansatzen. Im besonderen wird ein 2-Kompartment-System: Atmosphare – Biosphare-Festland vorgestellt, das einmal als materiell abgeschlossenes und zum anderen als materiell offenes, jeweils nicht-autonomes System behandelt wird. Als Resultat erhalten wir, das ein nicht-linearer Ansatz zu gegensatzlichem Stabilitatsverhalten sowohl in bezug auf den entsprechenden linearisierten als auch in bezug auf einen ad-hoc-linearen Ansatz fuhren kann. Bemerkenswert ist der ubergang Stabilitat/Instabilitat fur das abgeschlossene, nicht-autonome System bei einer Grenzrate, deren Wert in der gleichen Grosenordnung liegt. wie der obere Schatzwert der tatsachlichen effektiven Reduktion der Biosphare. Auserdem werden einfache Regeln zur Bestimmung der globalen Stabilitat eines abgeschlossenen, autonomen Systems hergeleitet und vor dem Hintergrund des globalen C-Zyklus diskutiert. At present it is debated, whether the land biota are to be regarded as a source or a sink for atmospheric CO2 within the global carbon cycle [1–4]. In our approach we describe the autonomous, natural dynamics of a certain subsystem (e.g. land biosphere) as the difference of an input and an output rate of a general non-linear structure. Thus our method differs from conventional linear approaches. In particular the 2-compartment system “atmosphere – land biosphere” is presented and treated as a materially open as well as a closed system. As a result we obtain that a non-linear approach may lead to opposed stability behaviour with respect to the corresponding linearized as well as to the ad-hoc-linear rate expressions. It is noteworthy that the stability/instability transition occurs at a critical rate, with values in the same order of magnitude as the present estimates of the anthropogenic transfer of biogenic carbon to the atmosphere. Finally we present some simple rules to determine the global stability of closed autonomous systems, and apply them to the global carbon cycle.

Dans l'etat actuel des connaissances, on ne sait pas s'il faut considerer le milieu terrestre comme une source ou un capteur du CO 2 atmospherique

Kohlmaier, G.H., Sire, E.O., Brohl, H., Kilian, W., Fischbach, U., Plochl, M., Muller, T. and Jiang, Y., 1984. Dramatic development in the dying of German spruce-fir forests: in search of possible cause-effect relationships. Ecol. Modelling, 22: 45–65. Tree diseases caused by air pollution have been observed for the last 100 years in the near neighbourhood of industrial facilities. In the middle of the 70's, for the first time tree injury and death in fir species were recognized in extended areas remote from pollution sources in the southern parts of the Federal Republic of Germany. Since the beginning of the 80's at an ever accelerating rate dieback of other tree species, especially within the very common Picea abies stands, has been observed affecting practically all forest areas in Western Germany. This paper focuses on the dynamics of the dieback of forest stands in a formal kinetic description. After a short review of the time development of spruce dieback in Western Germany, the emission and immission data of the main air pollutants in Europe are summarized and observed pollution effects are discussed. Rather than concentrating on the effect of a specific pollutant to specific parts of the forest ecosystems we are interested here in what type of dynamics will lead to an abrupt change in the variables of state following a nearly constant input of fume gases or an increasing input of NO x and heavy metals. A threshold model with continous accumulation of pollutants up to a certain critical level and following collapse is discussed and applied to the changes in soil chemistry, especially pH-changes following acid input. Second, a model of canopy photosynthesis as affected by pollution is presented and possible transitions from healthy to injured states following a change in pollution parameters are discussed.

For pt.I see ibid., vol.11, no.18, p.3145 (1978). A classical trajectory analysis for T to V excitation and CID processes of highly vibrationally excited Morse diatomics in Cinfinity collisions with atoms, assuming a pure repulsive exponential interaction, is presented. Phase-averaged energy transfer and CID probabilities have been obtained for a wide range of mass distributions and initial energies. Effects of vibrational inhibition/enhancement and 'double' impacts on CID probabilities are investigated. Some analytical results for the hard-sphere limit are also presented.

In einer fruheren Arbeit wurde von den Autoren Nikitin und Kohlmaier ein phanomenologisch eingefuhrter “Reibungskoeffizient” γ benutzt, um die wahrend eines Stosvorganges stattfindende Energieabwanderung aus der Endbindung in den Molekulrest zu beschreiben. In dieser Arbeit wird der Koeffizient γ uber eine mechanische Theorie atomistisch begrundet. In an earlier publication by Nikitin and Kohlmaier a “friction coefficient” γ was introduced phenomenologically to describe the energy flow from the terminal bond into the molecule during a collision process. In this paper the coefficient γ is substantiated atomistically by a mechanic theory.

The study of collisional transitional probabilities for the de‐excitation by inert gases of chemically activated sec‐butyl radicals, excited to internal energies in excess of 40 kcal mole−1, has been extended to H2, D2, N2, CO2, CH4, CD3F, CH3Cl, and SF6. The diatomic gases display behavior similar to the rare gases, and on a preferred exponential model of collisional transition probabilities the average amount of energy transferred per collision is 〈ΔE〉expon≃1.3 kcal mole−1. On a stepladder model the corresponding amount is ΔE≃2.5 kcal mole−1. From higher‐pressure data, the efficiency for CD3F, CH3Cl, and SF6 is deduced to be comparable with that for butene and, on a preferred stepladder model, ΔE>9 kcal. For CO2 and CH4 the behavior is intermediate. The possible importance of the role of internal rotation of butyl in facilitating energy transfer is noted; some uncertainty concerning the role of over‐all rotations and vibrational modes of the deactivator in the relaxation process exists.

Es wird eine exakte klassische Behandlung eines unelastischen Stosvorganges zwischen einem strukturlos gedachten Atom und einem beliebig angeregten vielatomigen Modellmolekul, das als System ungekoppelter Normalschwingungen beschrieben wird, diskutiert. Dabei wird der Stosvorgang eindimensional — entlang einer Symmetrieachse des Molekuls — behandelt („symmetrischer Zentralstos“); die Wechselwirkung des einfallenden Atoms mit einem Molekulbaustein, der seine Gleichgewichtslage auf der Symmetrieachse hat, wird als lineares repulsives Paarpotential angesetzt. Die bei beliebigen Anfangs-Schwingungszustanden aus den Rechnungen hergeleiteten exakten Ausdrucke fur die Energieubertragung gestatten eine Diskussion der moglichen Elementarprozesse (Desaktivierungs-, Mehrfachstose usw.); die Ergebnisse werden tabellarisch nach kinematischen und energetischen Gesichtspunkten zusammengestellt.

Vibrationally excited sec‐butyl radicals, having a narrow range of energies above 40 kcal mole−1, were produced in a heat bath of cis‐butene‐2‐rare‐gas mixtures by H addition to cis‐butene‐2. He, Ne, Ar, and Kr were used. Two competing reactions of the chemically activated radicals, decomposition by C–C rupture with critical energy of 33 kcal mole−1 and collisional stabilization, were studied as a function of pressure. Apparent rate constants for decomposition ka were obtained at three temperatures over a range of bath pressures by analysis of the decomposition and stabilization products. Strong and weak multistep collisional deactivation processes, corresponding to transfer of all or only part of the initial excess vibration energy (≥7 kcal mole−1) of the radicals, were considered. Multistep models of various step sizes (ΔE) give a family of calculated curves of ka as a function of p, each of which turns up from a quasi‐constant value at higher pressures to higher values at low pressures. Comparison with...

Ein eindimensionales System von linear angeordneten harmonischen Oszillatoren, die untereinander ebenfalls harmonisch gekoppelt sind, wird als vielatomiges Molekul- bzw. Festkorpermodell benutzt, um sowohl die intramolekulare Energiewanderung als auch die bei Stosprozessen stattfindende intermolekulare Schwingungsenergieubertragung zu beschreiben. Bei dem diskutierten Modell lassen sich zwei Grenzfalle unterscheiden; namlich der Fall der starken Kopplung, bei dem die Oszillatorfederkonstante wesentlich kleiner ist als die Kopplungskonstante, was auf das Modell der homogenen Kette fuhrt; und andererseits der Fall der schwachen Kopplung, der als Modellsystem schwach gekoppelter Oszillatoren interpretiert werden kann. An one-dimensional system of harmonic oscillators arranged linearly and coupled harmonically also among themselves is used as a model of a polyatomic molecule or solid to describe the intramolecular energy flow, as well as the intermolecular transfer of vibrational energy during collision processes. Two limiting cases can be distinguished: 1) the case of strong coupling characterized by an oscillator force constant considerably smaller than the coupling constant; this case leads to the model of the homogeneous chain; 2) the case of weak coupling leading to a model system for weakly coupled oscillators.

The longest standing hypothesis of interaction of acid precipitation (rain, snow, fog, particulate or gaseous compounds) with the vegetation is to be understood in a literal sense: deposition or interception of protons by the aboveground vegetation and soil leads to a negative stress for the plant metabolism. Both the leaves (needles) of the tree canopy as well as the soil-root system may be affected adversely by the excess acid.

The concentration of S(IV) in leaf cells is determined by a steady-state equilibrium. The input term is given by diffusion of SO2, solution of SO2 in cell wall liquids and the dissociation-equilibrium of [SO2·H2O] [S03 2-] [HSO3 -]. The output term describes the metabolisation (elimination) of S(IV). Under physiological conditions and with open stomata (i.e. resistance « 104sec·m-1) the velocity of elimination is neglegible compared with the velocity of the input. In this case the S(IV)-concentration in leaf cells is determined almost exclusively by the input term. Under these circumstances the S(IV) concentration inside the cell (c5) is about 105 times the S02 concentration in the environment (c1). For the same reason changes in vmax of the elimination reaction over a range of 102 (0.000054–0.0054) don’t change the S(IV) level significantly (differences < 0.1%). Only during the night when the stomata are closed (resistance: 1.3x104 sec·m-1) the input velocity decreases sufficiently to show a visible effect of elimination reactions on the steady-state equilibrium.

The role of the biosphere in the carbon cycle is considerably more complex and less well understood than that of the ocean, which is considered by Baes and Bjorkstrom (this volume). In order to understand its present function we need to examine its evolution in the past. Thus we first consider in this chapter the history of the biosphere and how it has been influenced by climate and man, and then go on to discuss its structure and function. Here the major vegetation types are described in relation to the environment. The basic components of and main processes within ecosystems, or biomes, are discussed and some simple model concepts for carbon transfers as a function of certain biotic or environmental parameters are developed.

Decrease of gross photosynthesis and increase of dark respiration are discussed as main effects of sulfur dioxide and its derivatives on vegetation. The nature of inhibition of the ribulose bisphosphate carboxylase as the main enzyme of the Calvin cycle is examined in model simulations. First simulation runs are compared with measurements under controlled conditions. Further simulation runs combine effects of climate and air pollution under ambient conditions. The effect of SO2 on net photosynthesis is measurable at relative high SO2 concentrations (more than 100 ppb) but seems to be neglectable at ambient conditions.