WGE Joint Trend Report, Part ICP Forests

WGE Joint Trend Report, Part ICP Forests

General:Walter Seidling

Contribution Air Quality:Marcus Schaub, …

Contribution Deposition: Peter Waldner, Aldo Marchetto, Karin Hansen

Contribution Crown Condition: NenadPotočič, VolkmarTimmermann, Walter Seidling, SerinaTrotzer

Contribution Foliar: Mathieu Jonard, PasiRautio, Alfred Fürst

2.3ICP Forests( 1 page, including map of stations) revised: 7.1.2015

The tenuous situation of forest condition in the 1980s over large parts of Europe gave reason for a large-scale observation of forest tree crown condition, an activity which is as Level I monitoring still high on the agenda. According to the main hypothesis about air pollution – at that time especially SO2as causal agent was of concern – the International Co-operative Programme on the Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) became part of the UNECE structures related to the Convention on Large-scale Transboundary Air Pollution (Lorenz 1995). The need to develop models based on cause-effect relationships was decisive to start a more intensive ecosystem-oriented monitoring in the 1990s (Level II, de Vries et al. 2003). One or both parts of the programme, which were installed at least temporarily in 42 European countries, have produced plenty of valuable data, collected or generated according to a harmonized manual (ICP Forests 2010 and earlier versions, see also Ferretti & Fischer 2013).

Retrieving impacts of air pollution on forest ecosystems requires on the one hand monitoring of crucial substance flows through the systems; on the other hand records on plant responses are necessary as well. To suffice the first, on-side measurements of important air quality features by passive samplers (Chap. x.1) and recordings of deposition in- and outside forest stands are key elements performed in the intensive monitoring programme (Chap. x.2). Results from these activities should correspond with temporal changes on the emission side, as well as reflect total inputs of substances like nitrogen, sulphur and other elements on the receptor side. Measurements of element flows and stocks within forest ecosystem are methodically less assessable. One respective approach is the collection and analysis of soil solution at different depth, and therefore another core activity within the Level II programme (Chap. x.3). The biological matrix of forest ecosystems should also reflect changes in content of nutritional and other elements: Foliar element analyses are an important tree-ecosystem interface in this respect (Chap. x.4). The latter point might be an example for the interference of physico-chemical and biological processes at these exposed plant organs. Drivers behind tree performance parameters like growth or crown condition might even be more superimposed by biologically controlled processes. Both crown condition (Chap. x.5) and stem increment (Chap. x.6) reflect the sum of all natural and anthropogenic influences acting at certain sites. This implies that both are unspecific and their development in time has to be interpreted with care.

As many of those data are collected in more or less fixed time intervals it is obvious to compile meaningful time series and perform relevant descriptive statistics. Such analyses may already give certain evidence on trends of causes and effectsdriving the development in forests at various scales. Of course, the selection of sites to be included in such evaluations is not trivial, neither in geographic terms nor in its temporal aspects. The same is true for any stratification applied.

x.1Ambient Air Concentrations

coming soon

x.2Deposition

coming soon

x.3Foliar Element Contents

Foliar nutrient concentrations have been monitored in ICP Forests intensive monitoring (Level II) plots from the early 1990s. The objectives have been to assess the possible changes in the concentrations of the main pollutants (sulphur and nitrogen) but also how these possibly affect forest tree nutrition in general, that might in turn be reflected in tree health. Here we analysed the nutritional status of the main European tree species using data collected during 1992-2009 on Level II plots. Tree selection, leaf collection, and foliar analysis were carried out according to the guidelines provided by the ICP Forests manual on sampling and analysis of needles and leaves (Rautio et al. 2010,RautioFürst 2013). To detect temporal trends, linear mixed models under consideration of plot and country as random factors were used (Jonard et al. 2015).

Of the 22 significant temporal trends that were found in foliar nutrient concentrations, 20 were decreasing and two were increasing (Table X). Even though both N and S concentrations in many species show decreasing trend, worryingly many essential nutrients are decreasing also. Perhaps the most alarming trend is the clear deterioration in P nutrition during the past two decades in some of the main tree species (Table X and Fig. X).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. However, soil nutrient supply has not always been sufficient to meet the demand of faster growing trees. As tree nutrient status exerts a tight control on net ecosystem productivity, this deterioration in tree nutrition could have a strong impact on the response of forest ecosystems to climate change.

Abies alba
/ Fagussylvatica

Picea abies
/ Quercus petraea

Pinus sylvestris
/ Quercus robur

Figure X. Temporal trends in foliar phosphorus concentration of current-year leaves for the main tree species in Europe. Dashed lines are thresholds separating the deficiency, normal and surplus ranges according to MellertGöttlein (2012); p values < 0.05 indicate whether the linear trends (solid line) are significant or not.

Table X. Linear temporal trends in foliar concentrations for the main tree species in Europe. Direction of slope is given as “+” or “-”, degree of significance: p < 0.1: (+) or (-), p < 0.05: + or -, p < 0.01: ++ or --, p < 0.001: +++ or ---.

Tree species / Leaf/needle / Mass / Foliar concentrations (mg g-1)
age / N / P / S / Ca / Mg / K
Fagus sylvatica / current year / +++ / - / --- / --- / - / ---
Quercuspetraea / current year / --- / --- / --- / - / -
Quercusrobur / current year / (+)
Abies alba / current year / -- / +
Piceaabies / current year / +++ / --- / (+) / --
Pinussylvestris / current year / - / ---
Abies alba / 1-year-old / -
Piceaabies / 1-year-old / - / --- / -- / ---
Pinussylvestris / 1-year-old / +++

x.4Crown Condition

Text coming soon

Tab. x: Statistics for crown condition (defoliation) of European main tree species; *: Quercuscerris, Q. pubescens, Q. frainetto, Q. pyrenaica , **: Pinuspinaster, P. halepensis, P. pinea, ***: Quercuscoccifera, Q. ilex, Q. rotundifolia, Q. suber; -: no significant result could be achieved in rkt package (R, CRAN …)

Treespecies (group) / Tau / RegionalSen’sslope / P / Overallmean [%]
Quercus robur et petraea / 0.199 / + 0.356 / < 0.0001 / 23.44
Mediterraneandeciduousoaks* / 0.199 / + 0.333 / < 0.0001 / 22.44
Mediterraneanlowland pines** / 0.268 / + 0.286 / < 0.0001 / 18.34
Mediterraneanevergreenoaks*** / 0.218 / + 0.267 / < 0.0001 / 20.91
Fagussylvatica / 0.135 / + 0.200 / < 0.0001 / 19.08
Pinus sylvestris / - / - / - / 17.71
Picea abies / - / - / - / 19.76
/ Fig. x: Examples for trends (Sen’sslopes, omitedfor Pinus sylvestrisand Picea abies) and developments of annualmeans of crown condition of major Europeantreespecies at large-scale monitoring (Level I) sites. Points represent plot means, for claritythese are not interconnected as usuallydone in time series.

Literature

De Vries, W., Vel, E.M., Reinds, G.J., Deelstra, H., Klap, J.M., Leeters, E.E.J.M., Hendriks, C.M.A., Kerkvoorden, M., Landmann, G., Herkendell, J., Haußmann, T., Erisman, J.W., 2003: Intensive monitoring of forest ecosystems in Europe. 1. Objectives, set-up and evaluation strategy. For. Ecol. Manage. 174:77–95.

Ferretti, M., Fischer, R. (eds.), 2013: Forest Monitoring: Methods for terrestrial investigations in Europe with an overview of North America and Asia, Elsevier, Amsterdam, 507 p.

ICP Forests, 2010: Manual on methods and criteriafor harmonized sampling, assessment, monitoringand analysis of the effects of air pollutionon forests. UNECE ICP Forests, Hamburg, Germany[online URL:

Jonard, M., Fürst, A., Verstraeten, A., Thimonier, A., Timmermann, V., Potočić, N., Waldner, P., Benham, S., Hansen, K., Merilä, P., Quentin Ponette, Q., de la Cruz, A.C., Roskams, P., Nicolas, M., Croisé, L., Ingerslev, M., Matteucci, G., Decinti, B., Bascietto, M. and Rautio, P. 2015: Tree mineral nutrition is deteriorating in Europe. Global Change Biology 21: 418-430.

Lorenz, M., 1995: International co-operative programme on assessment of monitoring of air pollution effects on forests. Water Air Soil Pollut. 85:1221–1226.

Mellert, K.H., Göttlein, A., 2012: Comparison of new foliar nutrient thresholds derived from van den Burg’s literature compilation with established central European references. European Journal of Forest Research 131: 1461-1472.

Rautio, P., Fürst, A., 2013: Tree Foliage: Sampling and Chemical Analyses. In: Ferretti, M. & Fischer, R. (eds.): Forest Monitoring. Methods for Terrestrial Investigations in Europe with an Overview of North America and Asia. Developments in Environmental Science 12: 223-236.

Rautio, P., Fürst, A., Stefan, K. et al. 2010. Sampling and Analysis of Needles and Leaves.Manual Part XII. In: Manual on methods and criteria for harmonized sampling, assessment, monitoring and analysis of the effects of air pollution on forests, UNECE, ICP Forests Programme Co-ordinating Centre, Hamburg, Germany. [