Yellowing of trees with current year needle-class remaining green shows typical symptoms of magnesium deficiency. The chemical analysis proved severe deficiency of magnesium and mild deficiency of calcium in needles and forest soils indeed. This corresponds to the new forest decline as observed in the 1970s and the 1980s in some regions in Germany and France. Other contributing factor breaking out yellowing at that extent at particularly short time is not known. The problem is even increasing, because yellowing has recently appeared also in other mountain localities in Central Europe even though in smaller scale

The aim of the international EU project was to characterize the status, conditions, and constraints for natural regeneration of Norway spruce (Picea abies [L.] Karst.) ecosystems in different stage of forest decline on three permanent research plots in the Giant Mts., to assess whether the biotechnological measures are necessary to support a natural regeneration at each plot. There were not ascertained any fundamental differences in basic soil types of three permenent research plots. No significant differences were observed in diversity of fungal and bacterial rhizospheric populations, including ectomycorrhizal symbionts

Determination of the streses operating on a forest ecosystem demands the use of several bioindication methods. Air quality indicators were assessed from an inventory of forest decline based on the assessment of tree crowns and lichens. Photosynthetic pigments, ascorbic acid and major macro nutrients were studied in mountain pine (Pinus mugo Yurra) needles as indicators of physiological and biochemical stress. Analyses were carried out at selected forest plots and transects in predominantly unpolluted areas within Triglav National Park, Julian Alps, Slovenia. It was assumed that air pollutant input in forest ecosystems is of two kind, e.g. local from the air pollutin sources in the valleys on the North-West part of tha national park and transboundary source at high altitudes

While nitrogen input exceeded the critical loads of the WHO (1995), nitrogen deficiency and nutrient imbalances were verified by needle analyses. The atmospheric input of inorganic nitrogen was higher than the nitrogen output in 50 cm soil depth. A tracer experiment with 15N helped to prove that not more than half of the applied nitrate could be discharged. This allows the conclusion that nitrogen is stored in the system and that the site cannot yet be said to be saturated with nitrogen. The same result was also obtained by modelling

Spis region is due to long-term effect of air pollution one of the most polluted regions in Slovakia. Decline of trees, mostly of spruce, was recorded here altogether with disintegration of forest stands. Incidental felling and its volume is frequently connected with local source of air pollution from iron-ore works Rudnany and Kovohuty. Long-range transfer of air pollutants from Poland (Katowice) plays a certain role in air pollution as well. In the year 1994 the damaged stands were classified into the zones of endangerment, the period of the validity of forest management plan was shortened and there were proposed measures for forest regeneration

Toxic effects of photochemical smog on ponderosa and Jeffrey pines in the San Bernardino Mountains were discovered in the 1950s. It was revealed that ozone is the main cause of foliar injury manifested as chlorotic mottle and premature needle senescence. Various morphological, physiological and biochemical alterations in the affected plants have been reported over a period of about 40 years of multidisciplinary research. Recently, the focus of research has shifted from studying the effects of ozone to multiple pollutant effects. Recent studies have indicated that the combination of ozone and nitrogen may alter biomass allocation in pines towards that of deciduous trees, accelerate litter accumulation and increase carbon sequestration rates in heavily polluted forests

The phenolic compounds showed different responses to fertilization. Fine roots of beech showed a significant decrease of (-) epicateching (84-99%) and pecatannol (78-98%) with nitrogen fertilization. Fine roots of fertilized Norway spruce showed decreased concentrations of 4-hydroxyacetophenone (33-48%), p-coumaric acid (44-64%), and pecatannol (36-61%). Concentration of p-hydroxybenzoic acid and protocatechuic acid were significantly higher in no fertilized roots. However in both tree species fertilization had no effect on vanillin and quercetin concentration in fine roots. It is suggested that roots of beech and Norway spruce are more susceptible to attacks of pathogens when they are exposed to impact of nitrogen

A DIRT (Detritus Input and Removal Treatments) experiment was initiated at the Sikfokut Forest LTER site in Hungary in November 2000. This study was designed to evaluate how sources and quantities of litter inputs control nutrient cycling and carbon storage in forest soils across sites with different climate, C and N status. Sikfokut Forest was selected for its high N deposition rate compared the Harvard Forest LTER, Bousson Forest and Andrews Forest LTER DIRT experiment sites in the United States. Trends in soil enzyme phosphatase and beta-glucosidase activity at Sikfokut indicate that the microbial community there is already clearly responding to reduced litter availability after only two years of treatment

Passive samplers offer considerable advantages for measuring ozone (O3) concentrations in remote areas. Measurements with passive samplers typically result in data about weekly-to-monthly O3 concentrations, which are not consistent with the definitions of cumulative indices currently being used to estimate the exposure of vegetation to O3. For this reason, attempts were and are being made to develop statistical and empirical methods to estimate exposure indices like the AOT40 adopted in Europe (O3 Accumulated Over Threshold 40 ppb) starting from mean concentrations obtained from passive samplers. This paper describes an empirical method adopted in Italy to estimate 1996-2000 AOT40 values at 20 forest sites of the Italian network of intensive monitoring of forest ecosystems

This paper summarizes the data on growth response and N uptake in open-top chambers planted with ponderosa pine (Pinus ponderosa Laws.) treated with both N (0, 10, and 20 g N msub-2 yrsub-1 as ammonium sulfate ) and CO2. Both N and elevated CO2 caused increased growth. The effects of N on growth response to elevated CO2 were assessed in various ways and various interpretations could be drawn depending on which metric was used, including a negative effect of N on growth response to CO2. These calculations suggest that expressing growth as percentages can be misleading, especially when done on a grams per tree basis