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AbstractVegetation productivity first increases and then decreases with temperature; and temperature corresponding to the maximum productivity is called optimal temperature (Topt). In this study, we used satellite derived near‐infrared reflectance of vegetation (NIRv) data to map Topt of vegetation productivity at the spatial resolution of 0.1° on the Tibetan Plateau (TP), one of most sensitive regions in the climate system. The average Topt of non‐forest vegetation on the TP is about 14.7°C, significantly lower than the Topt value used in current ecosystem models. A remarkable geographical heterogeneity in Topt is observed over the TP. Higher Topt values generally appear in the north‐eastern TP, while the south‐western TP has relatively lower Topt (<10°C), in line with the difference of climate conditions and topography across different regions. Spatially, Topt tends to decrease by 0.41°C per 100 m increase in elevation, faster than the elevational elapse rate of growing season temperature, implying a potential CO2 regulation of Topt in addition to temperature acclimation. Topt increases by 0.66°C for each 1°C of rising mean annual temperature as a result of vegetation acclimation to climate change. However, at least at the decadal scale, there is no significant change in Topt between 2000s and 2010s, suggesting that the Topt climate acclimation may not keep up with the warming rate. Finally, future (2091–2100) warming could be close to and even surpass Topt on the TP under different RCP scenarios without considering potential climate acclimation. Our analyses imply that the temperature tipping point when the impact of future warming shifts from positive to negative on the TP is greatly overestimated by current vegetation models. Future research needs to include varying thermal and CO2 acclimation effects on Topt across different time scales in vegetation models.

Abstract The use of bio-energy crops for electricity production is considered an effective means to mitigate the greenhouse effect, mainly due to its ability to substitute fossil fuels. A whole range of crops qualify for bio-energy production and a rational choice is not readily made. This paper evaluates the energy and greenhouse gas balance of a mixed indigenous hardwood coppice as an extensive, low-input bio-energy crop. The impact on fossil energy use and greenhouse gas emission is calculated and discussed by comparing its life cycle (cultivation, processing and conversion into energy) with two conventional bio-energy crops (short rotation systems of willow and Miscanthus). For each life cycle process, the flows of fossil energy and greenhouse gas that are created for the production of one functional unit are calculated. The results show that low-input bio-energy crops use comparatively less fossil fuel and avoid more greenhouse gas emission per unit of produced energy than conventional bio-energy crops during the first 100 yr . Where the mixed coppice system avoids up till 0.13 t CO 2 eq./GJ, Miscanthus does not exceed 0.07 t CO 2 eq./GJ. After 100 yr their performances become comparable, amounting to 0.05 t CO 2 eq./ha/GJ. However, if the land surface itself is chosen as a functional unit, conventional crops perform better with respect to mitigating the greenhouse effect. Miscanthus avoids a maximum of 12.9 t CO 2 eq./ha/yr, while mixed coppice attains 9.5 t CO 2 eq./ha/yr at the most.

Abstract As bioenergy plantations are a relatively new phenomenon, long-term experimental data on their productivity and tolerance to environmental stress that provides a robust framework for site selection and potential productivity assessment is still lacking. To address this need, we developed a method to correlate the productivity of bioenergy plantations with local climate using tree-ring chronologies. Tree-ring width from 37 Populus nigra (age > 115 y) and 368 poplar hybrid (Populus nigra × Populus maximowiczii) (9–12 y) individuals were collected and analyzed at demonstration sites in the Czech Republic. The growth of mature, naturally grown solitary native trees and young congeneric hybrids grown in high density (∼10,000 ha−1) showed statistically significant correlations (r = 0.71, p

Abstract The energetic use of residues from agriculture can foster the transition towards a more renewable energy supply. However, sustainability issues have to be considered along the entire provision chain as they affect the resource and energy potential as well as the achievable contribution to climate mitigation. Straw is one of the most important agricultural residues in Germany. It is not yet used for energy purposes extensively and compared to other agricultural feedstock it shows low competition with food, feed or fiber. This paper analyses on the one hand the sustainable potential of cereal straw for energy application in Germany considering the actual agricultural conditions, and on the other hand the global warming potential from different energy provision chains based on straw. Different humus-balance tools that are able to assess the organic matter (OM) demand to presume soil fertility. The analysis of straw potentials was applied at NUTS 3 level for Germany, based on statistical data. The results of this analysis were used as input data for the modeling of concepts for straw provision and use. Greenhouse gas (GHG) emissions were calculated for each concept in order to compare the global warming potential of various energy applications, to investigate the relative contribution of different production steps and to compare them with fossil energy applications. In total, 29.8 Tg of straw (fresh matter) are produced annually in Germany (1999–2007). Approximately 4.8 Tg of the total straw occurrence are annually required by animal husbandry. Between 7.97 and 13.25 Tg straw can be classified as sustainable straw. Highest straw potential (3.99 Mg ha−1) can be found in parts of Schleswig-Holstein, Mecklenburg–West Pomerania, North Rhine-Westphalia and Lower Saxony. But there are also regions that show a net deficit. The cumulated GHG emissions for the resulting concepts are between 8 and 35 g CO2-eq. MJ−1. In comparison to fossil energy applications, the highest reduction potential occurs for concepts for combined heat and power (CHP) provision, i.e. 223 g CO 2 -eq . MJ el - 1 . This study highlights the possible contribution of straw as renewable energy carrier, but also demonstrates that there are regional restrictions for straw use.

Short rotation coppice cultures (SRC) are intensively managed, high-density plantations of multi-shoot trees. In April 1996, an SRC field trial with 17 different poplar clones was established in Boom (Belgium) on a former waste disposal site. In December 1996 and January 2001, all shoots were cut back to a height of 5 cm to create a coppice culture. For six clones, wood and bark were sampled at the bottom, middle and top of a shoot in August and November 2002. No significant height effect of metal concentration was found, but for wood, metal concentrations generally increased toward the top of the shoot in August, and decreased toward the top of the shoot in November. Phytoextraction potential of a clone was primarily determined by metal concentration and by biomass production. Shoot size and number of shoots per stool were less important, as a high biomass production could be achieved by producing a few large shoots or many smaller shoots. Clone Fritzi Pauley accumulated 1.4 kg ha(-1) of Al over two years; Wolterson and Balsam Spire showed a relatively high accumulation of Cd and Zn, i.e. averaging, respectively 47 and 57 g ha(-1) for Cd and 2.4 and 2.0 kg ha(-1) for Zn over two years.

Because of their prominent role in global biomass productivity, as well as their complex structure and function, forests and tree species deserve particular attention in studies on the likely impact of elevated atmospheric CO2 on terrestrial vegetation. Poplar (Populus) has proven to be an interesting study object due to its fast response to a changing environment, and the growing importance of managed forests in the carbon balance. Results of both chamber and field experiments with different poplar species and hybrids are reviewed in this contribution. Despite the variability between experiments and species, and the remaining uncertainty over the long term, poplar is likely to profit from a rising atmospheric CO2 concentration with a mean biomass stimulation of 33%. Environmental conditions and pollutants (e.g. O3) may counteract this stimulation but with managed plantations, environmental constraints might not occur. The predicted responses of poplar to rising atmospheric CO2 have implications for future forest management and the expected forest carbon sequestration.

The protection and management of protected areas must be adapted to the effects of climate change. An important question is if the law on protected areas is capable of dealing with the required changes. In general, both international nature conventions and European Union nature conservation law do not contain any specific provisions on climate change and protected areas. Attention has been paid to this link in non-binding decisions and policy documents. In order to adapt the law to increased dynamics from climate change, more flexibility is needed. This flexibility should not be understood as "legal" flexibility, in the sense of the weakening nature conservation provisions. Scientific uncertainties on the effects of climate change might conflict with the need for legal certainties. In order to adapt to the effects of climate change, the two crucial elements are the strengthening of core protected areas and connectivity between the core areas. At the international level, both elements can be found in non-binding documents. International law enables the required adaptation; however, it often lacks concrete obligations. A stronger legal framework can be found at the level of the European Union. The Birds and Habitats Directives contain sufficient tools to deal with the effects of climate change. The Directives have been insufficiently implemented so far. Especially the central goals of reaching a favorable conservation status and connectivity measures need to be addressed much more in the future.

POTAMON is a unidimensional, non-stationary model, designed for simulating potamoplankton from source to mouth. The forcing variables are discharge, river morphology, water temperature, available light and nutrient inputs. Given the description of several algal categories, POTAMON allows to simulate algal "successions" at a particular site, as well as longitudinal changes of potamoplankton composition and biomass. The algal categories differ by their physiology, their loss rates, and their sensitivity to grazing by zooplankton. Two zooplankton categories were considered, Brachionus-like and Keratella-like, which differ by their clearance rate, their incipient limiting level, their selectivity towards phytoplankton, and their growth yield. The model simulates satisfactorily the onset and the magnitude of the phytoplankton spring bloom in the Belgian part of R. Meuse, the biomass decrease in early summer, and the autumn bloom. It also renders the major variations of algal assemblages along the river. The model allows to confirm that the main driving variables of potamoplankton dynamics in a eutrophic river are physical factors: discharge and related variables (e.g. retention time), light and temperature. In addition, the simulations confirm that the zooplankton-phytoplankton interaction may result in phytoplankton biomass fluctuations and compositional changes. POTAMON can be useful to explore plankton dynamics in a large river, and it may become a tool to test various management measures.