Tree mineral nutrition is deteriorating in Europe.

The response of forest ecosystems to increased atmospheric CO2 is constrained by nutrient availability. It is thus crucial to account for nutrient limitation when studying the forest response to climate change. The objectives of this study were to describe the nutritional status of the main European tree species, to identify growth-limiting nutrients and to assess changes in tree nutrition during the past two decades. We analysed the foliar nutrition data collected during 1992-2009 on the intensive forest monitoring plots of the ICP Forests programme. Of the 22 significant temporal trends that were observed in foliar nutrient concentrations, 20 were decreasing and two were increasing. Some of these trends were alarming, among which the foliar P concentration in F. sylvatica, Q. Petraea and P. sylvestris that significantly deteriorated during 1992-2009. In Q. Petraea and P. sylvestris, the decrease in foliar P concentration was more pronounced on plots with low foliar P status, meaning that trees with latent P deficiency could become deficient in the near future. Increased tree productivity, possibly resulting from high N deposition and from the global increase in atmospheric CO2, has led to higher nutrient demand by trees. As the soil nutrient supply was not always sufficient to meet the demands of faster growing trees, this could partly explain the deterioration of tree mineral nutrition. The results suggest that when evaluating forest carbon storage capacity and when planning to reduce CO2 emissions by increasing use of wood biomass for bioenergy, it is crucial that nutrient limitations for forest growth are considered.

Mercury in tree rings close to emission sources in Austria.

Mercury in wood is an important pool of this heavy metal in forest ecosystems because of its relatively high proportion in the biomass compared to other pools. This paper describes the successful application of a modified methodology for stem disk sampling based on wood particles from stem disks from Donawitz (Styria, Austria; pig iron production), from Brixlegg (Tyrol; former copper and silver mining, copper ore processing and copper recycling), and from Gmunden (Upper Austria; cement production). The maximum mercury concentration in the stem disks from Donawitz (Hinterberg: 20.5 ppb, St. Peter: 9.3 ppb) was recorded in the early 1970s. Several maxima were obtained from the stem disks from Brixlegg: the first was in 1813 (149.9 ppb), potentially even earlier, a second (37.6 ppb) in the late nineteenth century until the late 1920s, and a third local maximum in the 1970s (9.1 ppb), followed by a tendency to decline until the present. A stem disk from Gmunden in Upper Austria showed values of mercury concentrations indicating no increases compared to literature about background sites (≤ 3.2 ppb). This method revealed trends in mercury concentrations in tree rings originating from several different mercury emission sources in Austria coinciding with information about industrial history (where available) together with a justifiable effort. We therefore recommend it for further investigations on mercury concentrations in tree rings and their changes over time.

Monitoring the impact of sulphur with the Austrian Bioindicator Grid.

In Austria, the impact of sulphur has been assessed since 1985 with the help of the Austrian Bioindicator Grid on 760 sample plots with Picea abies as the main tree species (90%). The annual sampling allows a precise evaluation of the temporal and regional development of the impact of sulphur on the basis of legal standards. Despite the reduction of SO2 emissions in Austria, the legal standard is still exceeded on 8% of the plots. These plots are mainly located near large Austrian emittors, but also in areas affected by transboundary sulphur emissions from neighbouring countries. The present paper describes how the Bioindicator Grid can be applied for the control of legal requirements to enact effective clean air measures in Austria and take supportive measures that reduce the impact of sulphur from emittors in neighbouring countries.