Andreas Heinemeyer

Fertile forests produce biomass more efficiently

Trees with sufficient nutrition are known to allocate carbon preferentially to aboveground plant parts. Our global study of 49 forests revealed an even more fundamental carbon allocation response to nutrient availability: forests with high-nutrient availability use 58 ± 3% (mean ± SE; 17 forests) of their photosynthates for plant biomass production (BP), while forests with low-nutrient availability only convert 42 ± 2% (mean ± SE; 19 forests) of annual photosynthates to biomass. This nutrient effect largely overshadows previously observed differences in carbon allocation patterns among climate zones, forest types and age classes. If forests with low-nutrient availability use 16 ± 4% less of their photosynthates for plant growth, what are these used for? Current knowledge suggests that lower BP per unit photosynthesis in forests with low- versus forests with high-nutrient availability reflects not merely an increase in plant respiration, but likely results from reduced carbon allocation to unaccounted components of net primary production, particularly root symbionts.

The impact of projected increases in urbanization on ecosystem services

Alteration in land use is likely to be a major driver of changes in the distribution of ecosystem services before 2050. In Europe, urbanization will probably be the main cause of land-use change. This increase in urbanization will result in spatial shifts in both supplies of ecosystem services and the beneficiaries of those services; the net outcome of such shifts remains to be determined. Here, we model changes in urban land cover in Britain based on large (16%) projected increases in the human population by 2031, and the consequences for three different services—flood mitigation, agricultural production and carbon storage. We show that under a scenario of densification of urban areas, the combined effect of increasing population and loss of permeable surfaces is likely to result in 1.7 million people living within 1 km of rivers with at least 10 per cent increases in projected peak flows, but that increasing suburban ‘sprawl’ will have little effect on flood mitigation services. Conversely, losses of stored carbon and agricultural production are over three times as high under the sprawl as under the ‘densification’ urban growth scenarios. Our results illustrate the challenges of meeting, but also of predicting, future demands and patterns of ecosystem services in the face of increasing urbanization.

Balancing alternative land uses in conservation prioritization

Pressure on ecosystems to provide various different and often conflicting services is immense and likely to increase. The impacts and success of conservation prioritization will be enhanced if the needs of competing land uses are recognized at the planning stage. We develop such methods and illustrate them with data about competing land uses in Great Britain, with the aim of developing a conservation priority ranking that balances between needs of biodiversity conservation, carbon storage, agricultural value, and urban development potential. While both carbon stocks and biodiversity are desirable features from the point of view of conservation, they compete with the needs of agriculture and urban development. In Britain the greatest conflicts exist between biodiversity and urban areas, while the largest carbon stocks occur mostly in Scotland in areas with low agricultural or urban pressure. In our application, we were able successfully to balance the spatial allocation of alternative land uses so that conflicts between them were much smaller than had they been developed separately. The proposed methods and software, Zonation, are applicable to structurally similar prioritization problems globally.

Ecosystem service benefits of contrasting conservation strategies in a human-dominated region

The hope among policy-makers and scientists alike is that conservation strategies designed to protect biodiversity also provide direct benefits to people by protecting other vital ecosystem services. The few studies that have examined the delivery of ecosystem services by existing conservation efforts have concentrated on large, ‘wilderness’-style biodiversity reserves. However, such reserves are not realistic options for densely populated regions. Here, we provide the first analyses that compare representation of biodiversity and three other ecosystem services across several contrasting conservation strategies in a human-dominated landscape (England). We show that small protected areas and protected landscapes (restrictive zoning) deliver high carbon storage and biodiversity, while existing incentive payment (agri-environment) schemes target areas that offer little advantage over other parts of England in terms of biodiversity, carbon storage and agricultural production. A fourth ecosystem service—recreation—is under-represented by all three strategies. Our findings are encouraging as they illustrate that restrictive zoning can play a major role in protecting natural capital assets in densely populated regions. However, trade-offs exist even among the four ecosystem services we considered, suggesting that a portfolio of conservation and sustainability investments will be needed to deliver both biodiversity and the other ecosystem services demanded by society.

Soil carbon dynamics : an integrated methodology

1. Soil carbon relations - an overview Werner L. Kutsch, Michael Bahn and Andreas Heinemeyer 2. Field measurements of soil respiration: principles and constraints, potentials and limitations of different methods J. Pumpanen, B. Longdoz and Werner L. Kutsch 3. Experimental design: scaling up in time and space, and its statistical considerations J.-A. Subke, A. Heinemeyer and M. Reichstein 4. Determination of soil carbon stocks and changes Mirco Rodeghiero, Andreas Heinemeyer, Marion Schrumpf and Pat Bellamy 5. Litter decomposition: concepts, methods and future perspectives M. Francesca Cotrufo, Ilaria Del Galdo and Daniela Piermatteo 6. Characterization of soil organic matter Karolien Denef, Alain F. Plante and Johan Six 7. Respiration from roots and the mycorrhizosphere Fernando E. Moyano, Owen K. Atkin, Michael Bahn, Dan Bruhn, Andrew J. Burton, Andreas Heinemeyer, Werner L. Kutsch and Gerhard Wieser 8. Separating autotrophic and heterotrophic components of soil respiration: lessons learned from trenching and related root exclusion experiments Daniel Epron 9. Measuring soil microbial parameters relevant for soil carbon fluxes Werner L. Kutsch, Joshua Schimel and Karolien Denef 10. Trophic interactions and their implications for soil C fluxes Edward Ayres, Diana H. Wall and Richard D. Bardgett 11. Semi-empirical modelling of the response of soil respiration to environmental factors in laboratory and field conditions 12. Modelling soil carbon dynamics Pete Falloon and Pete Smith 13. The role of soils in the Kyoto Protocol Pete Smith, Pete Falloon and Werner L. Kutsch 14. Synthesis: emerging issues and challenges for an integrated understanding of soil carbon fluxes M. Bahn, W. L. Kutsch and A. Heinemeyer 15. Towards a standardised protocol for the measurement of soil CO2 efflux M. Bahn, W. Kutsch, A. Heinemeyer and I. A. Janssens.

Reconciling biodiversity and carbon conservation

Climate change is leading to the development of land-based mitigation and adaptation strategies that are likely to have substantial impacts on global biodiversity. Of these, approaches to maintain carbon within existing natural ecosystems could have particularly large benefits for biodiversity. However, the geographical distributions of terrestrial carbon stocks and biodiversity differ. Using conservation planning analyses for the New World and Britain, we conclude that a carbon-only strategy would not be effective at conserving biodiversity, as have previous studies. Nonetheless, we find that a combined carbon-biodiversity strategy could simultaneously protect 90% of carbon stocks (relative to a carbon-only conservation strategy) and > 90% of the biodiversity (relative to a biodiversity-only strategy) in both regions. This combined approach encapsulates the principle of complementarity, whereby locations that contain different sets of species are prioritised, and hence disproportionately safeguard localised species that are not protected effectively by carbon-only strategies. It is efficient because localised species are concentrated into small parts of the terrestrial land surface, whereas carbon is somewhat more evenly distributed; and carbon stocks protected in one location are equivalent to those protected elsewhere. Efficient compromises can only be achieved when biodiversity and carbon are incorporated together within a spatial planning process.

Mycorrhizas and global environmental change: research at different scales

Global environmental change (GEC), in particular rising atmospheric CO2 concentration and temperature, will affect most ecosystems. The varied responses of plants to these aspects of GEC are well documented. As with other key below-ground components of terrestrial ecosystems, the response of the ubiquitous mycorrhizal fungal root symbionts has received limited attention. Most of the research on the effects of GEC on mycorrhizal fungi has been pot-based with a few field (especially monoculture) studies. A major question that arises in all these studies is whether the GEC effects on the mycorrhizal fungi are independent of the effects on their plant hosts. We evaluate the current knowledge on the effects of elevated CO2 and increased temperature on mycorrhizal fungi and focus on the few available field examples. The value of using long-term and large-scale field experiments is emphasised. We conclude that the laboratory evidence to date shows that the effect of elevated CO2 on mycorrhizal fungi is dependent on plant growth and that temperature effects seen in the past might have reflected a similar dependence. Therefore, how temperature directly affects mycorrhizal fungi remains unknown. In natural ecosystems, we predict that GEC effects on mycorrhizal fungal communities will be strongly mediated by the effects on plant communities to the extent that community level interactions will prove to be the key mechanism for determining GEC-induced changes in mycorrhizal fungal communities.

Processes controlling DOC in pore water during simulated drought cycles in six different UK peats

The effect of episodic drought on dissolved organic carbon (DOC) dynamics in peatlands has been the subject of considerable debate, as decomposition and DOC production is thought to increase under aerobic conditions, yet decreased DOC concentrations have been observed during drought periods. Decreased DOC solubility due to drought-induced acidification driven by sulphur (S) redox reactions has been proposed as a causal mechanism; however evidence is based on a limited number of studies carried out at a few sites. To test this hypothesis on a range of different peats, we carried out controlled drought simulation experiments on peat cores collected from six sites across Great Britain. Our data show a concurrent increase in sulphate (SO4) and a decrease in DOC across all sites during simulated water table draw-down, although the magnitude of the relationship between SO4 and DOC differed between sites. Instead, we found a consistent relationship across all sites between DOC decrease and acidification measured by the pore water acid neutralising capacity (ANC). ANC provided a more consistent measure of drought-induced acidification than SO4 alone because it accounts for differences in base cation and acid anions concentrations between sites. Rewetting resulted in rapid DOC increases without a concurrent increase in soil respiration, suggesting DOC changes were primarily controlled by soil acidity not soil biota. These results highlight the need for an integrated analysis of hydrologically driven chemical and biological processes in peatlands to improve our understanding and ability to predict the interaction between atmospheric pollution and changing climatic conditions from plot to regional and global scales.

Characterization of soil organic matter

INTRODUCTION Soil organic matter (SOM) generally refers to the non-living organic material within the soil matrix that was once part of, or produced by, a living organism. It is usually determined on soil that has passed through a 2-mm sieve, and therefore is free of coarse animal residues, surface litter and large roots. Soil organic matter can be of plant, animal or microbial origin, and consists of a continuum of materials in various stages of alteration due to both biotic and abiotic processes (Baldock and Skjemstad, 2000). Methods used in the past to estimate directly SOM content involved the destruction of the organic matter by treatment with hydrogen peroxide (H 2 O 2 ) or by ignition of the soil at high temperature (Nelson and Sommers, 1996). Both of these techniques, however, are subject to significant error: oxidation of SOM by H 2 O 2 is incomplete, and some inorganic soil constituents decompose upon heating. While different elements such as C, N, P, S etc. are bound into organic compounds, we will concentrate on soil organic carbon (SOC) for the purposes of this chapter because it is the dominant element, and because of its role in the global carbon cycle. Organic carbon to SOM conversion factors for surface soils typically range from 1.72 to 2.0 g SOM g −1 C (Nelson and Sommers, 1996). Direct measurement of total soil carbon involves the conversion of all forms of carbon to carbon dioxide (CO 2 ) by wet or dry combustion and subsequent quantification of the evolved CO 2 .

Climatic factors controlling the eastern and altitudinal distribution boundary of Digitalis purpurea L. in Germany

Summary Digitalis purpurea was studied as a representative of a plant species with subatlantic geographical distribution in Central Germany with the objective of identifying the underlying climatic causes of the species’ eastern distribution boundary. A transplantation experiment with 1-year-old plants and seeds was performed along a ca. 100 km west-east transect across the regional distribution boundary in northwest Thuringia and along an altitudinal transect from 380 m to 1130 m a.s.l. in the Harz Mountains. Continuous measurements of air temperatures below rosette leaves confirmed a clear gradient of increasing mean temperatures with decreasing elevation and, with the exception of one field site, from west to east. Biometrical measurements of the transplants and the survival rate of seedlings generally matched the temperature gradients. Photosynthesis measurements along the elevational transect showed that differences in growth between altitudes were reflected in differences of temperature optima of net assimilation. Seedling mortality was highest in winter at the highest and at the easternmost plot. Although this should be a clear indication of frost sensitivity, there was no satisfactory correlation with absolute minimum temperatures below the rosettes, which exhibited a range between −4.1°C and –9.2°C. Frost tolerance experiments were carried out in a freeze chamber at the end of the winter. Significant damage to leaves was found at −12°C or below; whereas the threshold for buds and roots was −15°C and −18°C, respectively. Although frost events of this magnitude were not observed below the rosettes during the period ofinvestigation, mainly because of snow cover, they occur regularly in the study area. In addition to the winter conditions, summer drought was found to have a strong influence on growth of adult plants at the eastern sites. This was confirmed by a manipulative experiment with additional watering. Transpiration experiments also showed a strong water deficit in unwatered plants in the east. The general conclusion from the study is that frost events in winter, which mainly affect the survival of seedlings, combined with summer drought periods, which mainly limit growth of adults, explain the eastern distribution boundary of Digitalis purpurea .