Gundolf H. Kohlmaier

Forest carbon sinks in the northern hemisphere

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, measurement-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 = 1015 g) during the early 1990s, consisting of 0.21 Pg C/yr in living biomass, 0.08 Pg C/yr in 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.

Evaluation of terrestrial carbon cycle models through simulations of the seasonal cycle of atmospheric CO2: First results of a model intercomparison study

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 RH, at 0.5° 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.

Interannual variation of carbon exchange fluxes in terrestrial ecosystems

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.

Carbon dioxide mitigation in forestry and wood industry.

List of Contents.- 1 Forest Resources: Past, Present and Future Role of Managed and Unmanaged Forests in the Global Carbon Balance.- 1.1 Historic Role of Forests in the Global Carbon Cycle.- 1.2 The History and Future Dynamics of Carbon Sequestration in Finlands Forest Sector.- 1.3 Dynamics of Forest Resources of the Former Soviet Union with Respect to the Carbon Budget.- 1.4 Past and Possible Future Carbon Dynamics of Canadas Boreal Forest Ecosystems.- 1.5 Assessment of Humid Tropical Forest Distribution and Conditions Using Remote Sensing at a Global Scale.- 2 Implementation of Carbon Dioxide Mitigation Measures in Forestry and Wood Industry on a National and International Scale.- 2.1 Analysis and Potential for Mitigation Options.- 2.2 Carbon Mitigation Potential of German Forestry Considering Competing Forms of Land Use.- 2.3 Present and Future Options of Forests and Forestry for CO2-Mitigation in Germany.- 2.4 Afforestation in Europe: Experiences and Future Possibilities.- 2.5 Implementing Carbon Mitigation Measures in the Forestry Sector - a Review.- 3 Quantitative and Qualitative Evaluation of Carbon Dioxide Mitigation in Forestry and Wood Industry.- 3.1 World Forests: The Area for Afforestation and their Potential for Fossil Carbon Sequestration and Substitution.- 3.2 Substitution of Wood from Plantation Forestry for Wood from Deforestation: Modelling the Effects on Carbon Storage.- 3.3 Life Cycle Assessment of Wood Products.- 3.4 The Face Foundation.- 3.5 Climate Stabilisation and Conservation of Biodiversity - Two Goals - One Way?.- 4 Forestry Mitigation Options under Future Climate Change and Socioeconomic Pressures.- 4.1 Future Development of the Carbon Cycle: The Role of the Biota/Forests within the IPCC Stabilisation Scenarios.- 4.2 The Frankfurt Biosphere Model (FBM): Regional Validation Using German Forest Yield Tables and Iventory Data and Extrapolation to a 2xCO2 Climate.- 4.3 The Direct Effect of CO2 Enrichment on the Growth of Trees and Forests.- 4.4 Ecosystem Properties and the Continued Operation of the Terrestrial Carbon Sink.- 4.5 The Distribution of Future Global Forests as Affected by Changing Climate and Land Use.

Model of the seasonal and perennial carbon dynamics in deciduous-type forests controlled by climatic variables

Abstract 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.

The use of satellite NDVI data for the validation of global vegetation phenology models: application to the Frankfurt Biosphere Model

Abstract 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.

Contribution of Temperate Forests to the World’s Carbon Budget

Temperate forests currently cover about 600 MHa, about half of their potential. Almost all these forests have been directly impacted by humans. The total living biomass in trees (including roots) was estimated to contain 33.7 Gt C. The total C pool for the entire forest biome was estimated as 98.8 Gt. The current net sink flux of biomass was calculated at 205 Mt yr−1, with a similar amount removed in harvests for manufacture into various products. The major cause of this C sink is forest regrowth. Forest regrowth is possible because fossil fuels are the major source of energy in temperate countries, instead of fuelwood. Future C in these forests will be greatly influenced by human activity. Options to sequester more C include conservation of forest resources, activities that increase forest productivity such as adopting rotation ages to optimize C production, afforestation, improvement of wood utilization, and waste management.

Structure of a global and seasonal carbon exchange model for the terrestrial biosphere the frankfurt biosphere model (FBM)

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.

Modelling ventilation efficiency of teleost fish gills for pollutants with high affinity to plasma proteins

Abstract 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.

Dramatic development in the dying of German spruce-fir forests: In search of possible cause-effect relationships

ABSTRACT 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 70s, 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 80s 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.