Die Blattanalyse als Monitoring - Instrument im Waldökosystem : Monitoring Air Pollution Impact on Permanent Sample Plots, Data Processing and Results Interpretation

1991

S. 139-147

5 Ta., 1 Lit.

Unselbständiges Werk

200059995

In declining forests foliar discoloration can be utilized as a vidual diagnostic tool. For Mg, K, P, N and Mn deficiency these are well described in both coniferous and deciduous tree species. On the contrary, Ca deficiency symptoms are not yet sufficiently researched. For exact evaluation of the actual nutritional status of forest trees/stands foliar analysis is a much safer method than soil analysis. In a variety of tree species deficiency threshold values have been defined. In this context recent findings with regard to S nutrition of Picea abies are detailed. Element ratios calculated on the basis of contents realted to foliar dry matter allow insight into potential imbalances of the nutrient supply. To avoid misinterpretation of dilution effects due to increased biomass production absolute element concentrations should be determined related to absolute foliar weight (e.g. 1000-needle weight). With respect to conifers further conclusions can be drawn from the increase or decrease of phloem mobile or immobile nutrient elements in needles of different age classes. The evaluation of current needle contents can be impaired in declining trees, because occasionally the usually better nutrition of the uppermost crown area may not be present. This problem, paricularly evident in K nutrition, can be overcome by analyzing needles of different age classes of 4th or 7th whorl. In general macroutrient element and Mn contents are not significantly influenced by cleaning the needles (e.g. washing with water or chloroform) prior to chemical treatment. However, particle deposition frequently leads to higher Al, Fe and Pb values. To use foliar analysis as an instrument to record the nutritional status of trees/stands on a long-term basis, for example in permanent sample plots, standardized harvesting (and analysis) techniques must be applied. In conifers these include needle age, crown position, exposition, harvesting time and sample size. Also, foliar nutrient contents are influenced by the age, productivity and flowering (seed production) of the trees as well as by enhanced canopy leaching, e.g. due to insect attack, frost damage, acid precipitation and/or air pollutants. Above all foliar nutrient contents reflect the nutrient availability of the rooted solum which inturn is impacted by climatic conditions (e.g. precipitation) that vary from year to year. When considering these parameters foliar analysis can be utilized as an appropriate tool to monitor not only nutritional changes within the trees/stands but also long-term chemical alterations of the rooted substrate.