peer reviewed | The effects of chronically enhanced (NH(4))(2)SO(4) deposition on ion concentrations in soil solution and ionic fluxes were investigated in a Picea abies plot at Grizedale forest, NW England. Soil cores closed at the base and containing a ceramic suction cup sampler were 'roofed' and watered every 2 weeks with bulk throughfall collected in the field. Treatments consisted of the inclusion of living roots from mature trees in the lysimeters and increasing (NH(4))(2)SO(4) deposition (NS treatment) to ambient + 75 kg N ha(-1) a(-1). Rainfall, throughfall and soil solutions were collected every 2 weeks during 18 months, and analysed for major cations and anions. NO(3)(-) fluxes significantly increased following NS treatment, and were balanced by increased Al(3+) losses. Increased SO(4)(2-) concentrations played a minor role in controlling soil solution cation concentrations. The soil exchange complex was dominated by Al and, during the experimental period, cores of all treatments 'switched' from Ca(2+) to Al(3+) leaching, leading to mean [Formula: see text] molar ratios in soil solution of NS treated cores of 0.24. The experiment confirmed that the most sensitive soils to acidification (through deposition or changing environmental conditions) are those with low base saturation, and with a pH in the lower Ca, or Al buffer ranges.

peer reviewed | The replenishment and persistence of marine species is contingent on dispersing larvae locating suitable habitat and surviving to a reproductive stage. Pelagic larvae rely on environmental cues to make behavioural decisions with chemical information being important for habitat selection at settlement. We explored the sensory world of crustaceans and fishes focusing on the impact anthropogenic alterations (ocean acidification, red soil, pesticide) have on conspecific chemical signals used by larvae for habitat selection. Crustacean (Stenopus hispidus) and fish (Chromis viridis) larvae recognized their conspecifics via chemical signals under control conditions. In the presence of acidified water, red soil or pesticide, the ability of larvae to chemically recognize conspecific cues was altered. Our study highlights that recruitment potential on coral reefs may decrease due to anthropogenic stressors. If so, populations of fishes and crustaceans will continue their rapid decline; larval recruitment will not replace and sustain the adult populations on degraded reefs.

International audience | Evidence from an international survey in the Atlantic biogeographic region of Europe indicates that chronic nitrogen deposition is reducing plant species richness in acid grasslands. Across the deposition gradient in this region (2–44 kg N ha−1 yr−1) species richness showed a curvilinear response, with greatest reductions in species richness when deposition increased from low levels. This has important implications for conservation policies, suggesting that to protect the most sensitive grasslands resources should be focussed where deposition is currently low. Soil pH is also an important driver of species richness indicating that the acidifying effect of nitrogen deposition may be contributing to species richness reductions. The results of this survey suggest that the impacts of nitrogen deposition can be observed over a large geographical range. Atmospheric nitrogen deposition is reducing biodiversity in grasslands across Europe.

International audience | The objective of this study was to assess the time variation of mineral and water stress levels across the life of a declining, Mg-deficient, spruce stand, in order to clarify the factors that caused the decline. Since 1985, strong soil acidification linked to a large leaching of nitrate and base cations was measured at the study site. In 1994, 5 trees were felled and tree rings were measured and analysed for Ca, Mg, K, Sr, 13 C/ 12 C and 87 Sr/ 86 Sr isotopic ratios. Strontium pools and fluxes as well as root Sr isotope ratio in relation to depth were also measured. Wood chemical concentrations and isotope ratios were strongly related to the dominance status of each tree. On average during the study period, the 87 Sr/ 86 Sr ratio of spruce wood decreased. Using a mechanistic model computing long term variations of 87 Sr/ 86 Sr ratio in trees and soils, we reproduced the observed trend by simulating soil acidification-increasing Sr drainage from the whole profile, and particularly from the organic horizon-, and root uptake becoming more superficial with time. Between 1952 and 1976, tree ring 13 C decreased strongly and continuously, which, in addition to other factors, might be related to an increase in water stress. Thus, a decrease in rooting depth, possibly related to soil acidification, appeared as a possible cause for the long term increase in water stress. The extreme drought event of 1976 appears to have revealed and triggered the decline.