ASSESSMENT AND ANALYSIS OF THE IMPACT OF AIR POLLUTANTS ON FOREST ECOSYSTEMS.

Objetivo

THE AIMS OF THE PROGRAMME ARE FOCUSSED ON IDENTIFICATION, ASSESSEMENT AND STRESS-SPECIFIC ANALYSIS OF POSSIBLE CAUSES FOR RECENT FOREST DECLINE.
In 1989 the comparative ecophysiological measurements started in 1988 on 20-year old spruce trees growing on natural sites in open top chambers with charcoal filtered and ambient air were continued. One part of our studies was the determination of diurnal courses of carbon dioxide and water vapour exchange parameters under normal ambient conditions. Additional to this, measurements for the characterisation of the performance of photosynthetic apparatus were carried out by studies of light and carbon dioxide response curves under controlled conditions.

Comparison of 20 year old spruce trees kept in non filtered air, in charcoal filtered air and on outside standing trees resulted in slightdifferences in microclimate factors between the experimental chambers and ambient climate. However, conditions for radiation, wind and deposition in chambers were more disadvantageous. The exclusion rate of sulphur dioxide, ozone, nitrogen oxides, dust and aerosols in charcoal filtered air was found to be more than 75 %.

Investigations were carried out on the uptake, storage and possible detoxification of minerals, especially aluminium ions, by ectomycorrhizae of forest trees. Elements were localised at the cellular level with an analytical transmission electron microscope using electron energy loss analysis. Aluminium was found to be localised on the surface of tips of non mycorrhizal roots, on the slimed surface of outer hyphae and in the polyphosphate droplets of the hyphal mantle and Harting net. The results indicate a filter mechanism for aluminium, but further experimentation is required in order to confirm this.

In open top chambers set up around 15 to 20 year old spruces (thus standing on undisturbed substrate) the influence of filtered and surrounding air on deposition and leaching processes in the tree crown were examined. Also, appropriate measuring instruments were installed under open air spruces. There was considerably less sulphate deposition under spruces affected by filtered air than under those exposed to surrounding air and also reduced leaching of calcium, magnesium and manganese. However, the loss of nutrient elements in the needles by leaching was compensated by a quick uptake through the roots.

Litter of beech, mountain maple, and spruce stands was sampled and analysed for nitrogen, phosphorus, potassium, calcium and magnesium. Yearly litter was compared to yearly bulk deposition in the stands. The ratio bulk deposition/litter input was used to characterize the importance of input pathways. The main input of macronutrients, except potassium, was found to be through litter. However, in soils poor in magnesium and calcium, bulk deposition showed a tendency to be greater than litter input, presumably because of crown exchange and folier leaching.

Lyophilised needle homogenates, obtained from spruce trees (Picea abies L), were biochemically characterised in relation to the environmental conditions (natural stand or open-top chambers). Biochemical parameters assayed were intermediates of energy (adenine and pyridine nucleotides) and carbohydrate metabolism (carbon partitioning between starch and sucrose). Generally, there were considerable differences between developing (current year) and older needles, in that developing needles had significantly higher adenosine triphosphate (ATP)/ adenosine diphosphate (ADP) and redox ratios. Needles from declining trees showed increased levels of both ratios of ATP/ADP and reduced nicotinamide adenine dinucleotide (NADH)/ nicotinamide adenine dinucleotide (NAD), and also a higher fructose 2,6-biphosphate content.
THE AIMS OF THE FOUR PROJECTS WITH TECHNICAL, SOIL-SCIENTIFIC AND ECOPHYSIOLOGICAL GOALS IN OPEN TOP CHAMBERS WILL ATTEMPTS TO CORRELATE THE DEGREE OF TREE DAMAGE AND POLLUTANT CONCENTRATION. BESIDES PILOT STAGE TESTING OF A NEW TYPE OF OPEN TOP CHAMBER BOTH THE LEACHING PHENOMENON AND THE ACTIVITY OF RESPIRATION AND PHOTOSYNTHESIS WILL BE ANALYSED.

USING SAMPLES FROM THESES OTC'S AS WELL AS FROM CONIFERS FROM VARYING NATURAL STANDS THE CONTENT OF IMPORTANT METABOLIC INTERMEDIATES SHALL BE RELATED TO THE PHENOMENOLOGICAL SYMPTOMS OF DAMAGE. SPECIAL EMPHASIS WILL BE PLACED ON THE ELUCIDATION OF INTERMEDIATE STPES IN THE CAUSAL CHAIN OF NEEDLE YELLOWING IN MATERIAL TAKEN AT MEDIUM ALTITUDE STANDS.
THE ROLE OF AIRBORNE NITROGENOUS COMPOUNDS AND THE STUDY OF DETOXIFICATION REGULATION IN CONIFER SEEDLINGS IS ALSO SUBJECT TO INVESTIGATION.IN CONNECTION WITH THE EFFECTS OF DIFFERENT STRESS FACTORS ON FOREST TREES THE REACTION OF THE RHIZOSPHERE AND PREDOMINANTLY OF THE MYCORRHIZA IS OF SPECIAL INTEREST. THE QUALITATIVE AND QUANTITATIVE DEPENDENCE OF THE FRUCTIFICATION OF MYCORRHIZA FUNGI ON AIR POLLUTION CONDITIONS, ON THE DEGREE OF TREE DAMAGE AND ON FERTILISATION MEASURES IS TO BE DETERMINED IN SPRUCE STANDS OF THE SOUTHERN BLACK FOREST. IN CONNECTION WITH SUCH THERAPIES THE REPEATEDLY RAISED QUESTION OF ENDANGERED GROUND WATER RESOURCES AND THE ASPECT OF HYPERFERTILISATION BY INCREASED NITROGEN INPUT WILL BE INVESTIGATED IN A CATCHMENT STUDY AT THREE WELL SEPARATED WATERSHEDS IN THE SOUTHERN BLACK FOREST.
ALL THE PROJECTS ARE BEING CARRIED OUT IN COOPERATION WITH RESEARCH GROUPS IN THE FRENCH PROGRAMME DEFORPA.

Ámbito científico

Programa(s)

FP1-ENVPROT 4C - Multiannual research and development programmes (EEC) in the field of the environment - Protection of the environment -, 1986-1990

Tema(s)

Data not available

Convocatoria de propuestas

Data not available

Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

Forschungszentrum Karlsruhe Technik und Umwelt GmbH

Aportación de la UE

Sin datos

Dirección

76021 Karlsruhe
Alemania

Coste total