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Abstract: Central European grasslands are characterized by a wide range of different management practices in close geographical proximity. Site‐specific management strategies strongly affect the biosphere–atmosphere exchange of the three greenhouse gases (GHG) carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). The evaluation of environmental impacts at site level is challenging, because most in situ measurements focus on the quantification of CO2 exchange, while long‐term N2O and CH4 flux measurements at ecosystem scale remain scarce. Here, we synthesized ecosystem CO2, N2O, and CH4 fluxes from 14 managed grassland sites, quantified by eddy covariance or chamber techniques. We found that grasslands were on average a CO2 sink (−1,783 to −91 g CO2 m−2 year−1), but a N2O source (18–638 g CO2‐eq. m−2 year−1), and either a CH4 sink or source (−9 to 488 g CO2‐eq. m−2 year−1). The net GHG balance (NGB) of nine sites where measurements of all three GHGs were available was found between −2,761 and −58 g CO2‐eq. m−2 year−1, with N2O and CH4 emissions offsetting concurrent CO2 uptake by on average 21 ± 6% across sites. The only positive NGB was found for one site during a restoration year with ploughing. The predictive power of soil parameters for N2O and CH4 fluxes was generally low and varied considerably within years. However, after site‐specific data normalization, we identified environmental conditions that indicated enhanced GHG source/sink activity (“sweet spots”) and gave a good prediction of normalized overall fluxes across sites. The application of animal slurry to grasslands increased N2O and CH4 emissions. The N2O‐N emission factor across sites was 1.8 ± 0.5%, but varied considerably at site level among the years (0.1%–8.6%). Although grassland management led to increased N2O and CH4 emissions, the CO2 sink strength was generally the most dominant component of the annual GHG budget. [ABSTRACT FROM AUTHOR]

Anthropogenic activities are altering levels of greenhouse gases to the extent that multiple and diverse ecosystem processes are being affected. Two gases that substantially influence forest health are atmospheric carbon dioxide ( CO2) and tropospheric ozone ( O3). Plant chemistry will play an important role in regulating ecosystem processes in future environments, but little information exists about the longitudinal effects of elevated CO2 and O3 on phytochemistry, especially for long-lived species such as trees. To address this need, we analysed foliar chemical data from two genotypes of trembling aspen, Populus tremuloides, collected over 10 years of exposure to levels of CO2 and O3 predicted for the year 2050. Elevated CO2 and O3 altered both primary and secondary chemistry, and the magnitude and direction of the responses varied across developmental stages and between aspen genotypes. Our findings suggest that the effects of CO2 and O3 on phytochemical traits that influence forest processes will vary over tree developmental stages, highlighting the need to continue long-term, experimental atmospheric change research. [ABSTRACT FROM AUTHOR]

This review assesses the impacts, both direct and indirect, of man-made changes to the composition of the air over a 200 year period on the severity of arable crop disease epidemics. The review focuses on two well-studied UK arable crops, wheat and oilseed rape, relating these examples to worldwide food security. In wheat, impacts of changes in concentrations of SO in air on two septoria diseases are discussed using data obtained from historical crop samples and unpublished experimental work. Changes in SO seem to alter septoria disease spectra both through direct effects on infection processes and through indirect effects on soil S status. Work on the oilseed rape diseases phoma stem canker and light leaf spot illustrates indirect impacts of increasing concentrations of greenhouse gases, mediated through climate change. It is projected that, by the 2050s, if diseases are not controlled, climate change will increase yields in Scotland but halve yields in southern England. These projections are discussed in relation to strategies for adaptation to environmental change. Since many strategies take 10-15 years to implement, it is important to take appropriate decisions soon. Furthermore, it is essential to make appropriate investment in collation of long-term data, modelling and experimental work to guide such decision-making by industry and government, as a contribution to worldwide food security. [ABSTRACT FROM AUTHOR]