Showing papers by "Ernst Detlef Schulze published in 2001"

Productivity overshadows temperature in determining soil and ecosystem respiration across European forests

Abstract: Summary This paper presents CO2 flux data from 18 forest ecosystems, studied in the European Union funded EUROFLUX project. Overall, mean annual gross primary productivity (GPP, the total amount of carbon (C) fixed during photosynthesis) of these forests was 1380 ± 330 gC m−2 y−1 (mean ±SD). On average, 80% of GPP was respired by autotrophs and heterotrophs and released back into the atmosphere (total ecosystem respiration, TER = 1100 ± 260 gC m−2 y−1). Mean annual soil respiration (SR) was 760 ± 340 gC m−2 y−1 (55% of GPP and 69% of TER). Among the investigated forests, large differences were observed in annual SR and TER that were not correlated with mean annual temperature. However, a significant correlation was observed between annual SR and TER and GPP among the relatively undisturbed forests. On the assumption that (i) root respiration is constrained by the allocation of photosynthates to the roots, which is coupled to productivity, and that (ii) the largest fraction of heterotrophic soil respiration originates from decomposition of young organic matter (leaves, fine roots), whose availability also depends on primary productivity, it is hypothesized that differences in SR among forests are likely to depend more on productivity than on temperature. At sites where soil disturbance has occurred (e.g. ploughing, drainage), soil espiration was a larger component of the ecosystem C budget and deviated from the relationship between annual SR (and TER) and GPP observed among the less-disturbed forests. At one particular forest, carbon losses from the soil were so large, that in some years the site became a net source of carbon to the atmosphere. Excluding the disturbed sites from the present analysis reduced mean SR to 660 ± 290 gC m−2 y−1, representing 49% of GPP and 63% of TER in the relatively undisturbed forest ecosystems.

Global Biogeochemical Cycles in the Climate System

Abstract: 1 Uncertainties of Global Biogeochemical Predictions 2 Uncertainties of Global Climate Predictions 3 Uncertainties in the Atmospheric Chemical System 4 Inferring Biogeochemical Sources and Sinks from Atmospheric Concentrations: General Consideration and Applications in Vegetarian Canopies 5 Biogeophysical Feedbacks and the Dynamics of Climate 6 Land-Ocean-Atmosphere Interactions and Monsoon Climate Change: A Paleo-Perspective 7 Paleobiogeochemistry 8 Should Phosphorus Availability Be Constraining Moist Tropical Forest Responses to Increasing CO2 Concentrations? 9 Trees in Grasslands: Biogeochemical Consequences of Woody Plant Expansion 10 Biogeochemistry in the Arctic: Patterns, Processes, and Controls 11 Evaporation in the Boreal Zone During Summer--Physics and Vegetation 12 Past and Future Forest Response to Rapid Climate Change 13 Biogeochemical Models: Implicit vs. Explicit Microbiology 14 The Global Soil Organic Carbon Pool 15 Plant Compounds and Their Turnover and Stability as Soil Organic Matter 16 Input/Output Balances and Nitrogen Limitation in Terrestrial Ecosystems 17 Interactions Between Hillslope Hydrochemistry, Nitrogen Dynamics and Plants in Fennoscandian Boreal Forest 18 The Cycle of Atmospheric Molecular Oxygen and its Isotopes 19 Constraining the Global Carbon Budget from Global to Regional Scales -- the Measurement Challenge 20 Carbon Isotope Discrimination of Terrestrial Ecosystems -- How Well do Observed and Modeled Results Match? 21 Photosynthetic Pathways and Climate 22 Biological Diversity, Evolution and Biogeochemistry 23 Atmospheric Perspectives on the Ocean Carbon Cycle 24 International Instruments for the Protection of the Climate and Their National Implementation 25 A New Tool to Characterizing and Managing Risks 26 Contrasting Approaches: The Ozone Layer, Climate Change and Resolving the Kyoto Dilemma 27 Optimizing Long-Term Climate Management Subject Index

Ecosystems and Their Goods and Services

Abstract: Follow this and additional works at: http://lib.dr.iastate.edu/ge_at_pubs Part of the Climate Commons, Environmental Indicators and Impact Assessment Commons, and the Systems Biology Commons The complete bibliographic information for this item can be found at http://lib.dr.iastate.edu/ ge_at_pubs/181. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html.

Quantification of insect nitrogen utilization by the venus fly trap Dionaea muscipula catching prey with highly variable isotope signatures

Abstract: Dionaea is a highly specialized carnivorous plant species with a unique mechanism for insect capture. The leaf is converted into an osmotically driven trap that closes when an insect triggers sensory trichomes. This study investigates the significance of insect capture for growth of Dionaea at different successional stages after a fire, under conditions where the prey is highly variable in its isotope signature. The contribution of insect-derived nitrogen (N) was estimated using the natural abundance of 15N. In contrast to previous 15N studies on carnivorous plants, the problem emerges that delta15N values of prey insects ranged between -4.47 per thousand (grasshoppers) and +7.21 per thousand (ants), a range that exceeds the delta15N values of non carnivorous reference plants (-4.2 per thousand) and soils (+3 per thousand). Thus, the isotope-mixing model used by Shearer and Kohl to estimate the amount of insect-derived N is not applicable. In a novel approach, the relationships of delta15N values of different organs with delta15N of trapping leaves were used to estimate N partitioning within the plant. It is estimated that soon after fire approximately 75% of the nitrogen is obtained from insects, regardless of plant size or developmental stage. The estimates are verified by calculating the average isotope signatures of insects from an isotope mass balance and comparing this with the average measured delta15N values of insects. It appears that for Dionaea to survive and reach the flowering stage, seedlings must first reach the 6th-leaf rosette stage, in which trap surface area nearly doubles and facilitates the capture of large insects. Large amounts of nitrogen thus made available to plants may facilitate an enhanced growth rate and the progressive production of additional large traps. Dionaea reaches a maximum abundance after fire when growth of the competing vegetation is suppressed. About 10 years after fire, when grasses and shrubs recover, Dionaea becomes overtopped by other species. This would not only reduce carbon assimilation but also the probability of catching larger prey. The amount of insect-derived nitrogen decreases to 46%, and Dionaea becomes increasingly dependent on N-supply from the soil. Competition for both light and N may cause the near disappearance of Dionaea in older stages of the fire succession.

Carbon balance gradient in European forests: should we doubt 'surprising' results? A reply to Piovesan & Adams

Abstract: This paper responds to the Forum contribution by Piovesan & Adams (2000) who criticized the results obtained by the EUROFLUX network on carbon fluxes of several European forests. The major point of criticism was that the data provided by EUROFLUX are inconsistent with current scientific understanding. It is argued that understanding the terrestrial global carbon cycle requires more than simply restating what was known previously, and that Piovesan & Adams have not been able to show any major conflicts between our findings and ecosystem or atmospheric-transport theories.

Evaporation in the boreal zone during summer - Physics and vegetation

Abstract: Publisher Summary The short but hot and dry summers in the boreal zone involve significant surface–atmosphere energy exchange. This chapter examines the regulation of this exchange in terms of evaporation from vegetation and soil by utilizing available field data, about half of which has been published in the past two years, with some new information from Siberia. For wetland, tundra, and broad-leaved deciduous forest, seasonal average evaporation obtains the theoretically expected equilibrium rate. A variety of sometimes unrelated factors apparently compensates over the course of a summer. For deciduous and evergreen needle-leaved forests, evaporation is about 70% and 50%, respectively, of the equilibrium rate, indicating an overwhelming degree of surface control. Among the three tree life-forms found in the boreal zone, forest evaporation rate is physiologically related to overstorey leaf habit, xylem anatomy, and especially successional position following disturbances such as fire. For the forests compared, this determines leaf nitrogen content and in turn the maximum stomatal and surface conductances and the leaf area index via the effects on photosynthetic and growth rates. The leaf area index affects understorey evaporation rate which is half the total in the needle-leaved forests and is governed largely by rainfall frequency.

Growth and Photosynthetic Carbon Metabolism in Tobacco Plants under an Oscillating CO2 Concentration in the Atmosphere

Abstract: The hypothesis for the present work was that photosynthetic acclimation to increased atmospheric CO2 in Nicotiana tabacum could be prevented by an oscillating supply of CO2. This was tested by growing half of the plants (for the 20 day period after sowing) at 700 μmol mol-1 CO2 (S+ plants) and half at 350 μmol mol-1 CO2 (S- plants) and thereafter switching them every 48 h from high to low CO2 and vice versa. These plants were compared with plants continuously kept (from sowing onwards) at 350 μmol mol-1 CO2 (C- plants) and 700 μmol mol-1 CO2 (C+ plants). Switching plants from high to low CO2 and vice versa (S+ and S-) did not improve plant growth efficiency, as hypothesized. The extra carbon fixed by the leaves under increased CO2 in the atmosphere, supplied either continuously or intermittently, was mostly stored as starch and not used to build additional structural biomass. The differences in final plant biomass, observed between S+ and S- plants, are explained by the CO2 concentration in the atmosphere during the first 20 days after sowing, the oscillation in CO2 supply thereafter is playing a smaller role in this response. Switching plants from high to low CO2 and vice versa, also did not prevent down-regulation of photosynthesis, despite lower leaf sugar concentrations than in C+ plants. Nitrate concentration decreased dramatically in C+, S+ and S- plants. The leaf C/N ratio was highest in C+ plants (ranging from 8 to 13), intermediate in S+ and S- plants (from 7 to 11) and lowest in C- plants (from 6 to 8). This supports the view that the balance between carbohydrates and nitrogen may have a triggering role in plant response under elevated CO2. Carbon export rates by the leaves seem to be independent of total carbon assimilation, suggesting a sink limiting effect on tobacco growth and phototsynthesis under elevated CO2.

Uncertainties of global biochemical predictions

Abstract: Publisher Summary In the past few years, application of improved measurements and models suggests a robust partitioning of CO 2 emissions from fossil fuel consumption and land use: about one-third remains in the atmosphere, one-third is reassimilated by land surfaces, and one-third is absorbed by the oceans. This chapter deals with the problems in locating a sink and emphasizes on the spatial, temporal, and biological variability of processes on local as well as continental scale. The commercial idea to market carbon sinks has initiated a major discussion about where on earth the largest sink capacity exists. It has been proposed that the sink exists in the Northern hemisphere with its center in the Eurasian region. This was countered and other theory propose based on analysis of gradients of CO 2 in the atmosphere that continental USA was the major carbon sink in the Northern hemisphere. On the other hand another theory predicts that the main terrestrial carbon sink is in the tropics. Current identification of biomes is not based on a functional analysis, and while some major biomes function similarly in carbon uptake (e.g., European conifer and deciduous forest) within-biome or-species effects can be extremely large. New ways of organizing ecological variability are needed. Further, the quantification of the mean residence time of vegetation and soil compartments and an understanding of the parameters that control this time-scale is necessary for process based predictions of carbon storage.