Volker Mues

Forest Health Status in Europe

Forest health status in Europe is assessed by the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). Established by the Convention on Long-Range Transboundary Air Pollution (CLRTAP) under the United Nations Economic Commission for Europe (UNECE), the ICP Forests has been monitoring forest condition in close cooperation with the European Commission (EC) for 20 years. The present paper describes the latest results of the deposition measurements on permanent monitoring plots and of the extensive defoliation sample survey. The findings reveal marked spatial patterns in bulk and throughfall depositions of nitrate (N-NO3), ammonium (N-NH4), and sulfate (S-SO4), as well as an obvious decrease in bulk and throughfall deposition of sulfate. Latest analyses of defoliation data confirm previous results, indicating a high correlation with weather extremes.

Climate variability drives recent tree mortality in Europe

Tree mortality is an important process in forest ecosystems, frequently hypothesized to be highly climate sensitive. Yet, tree death remains one of the least understood processes of forest dynamics. Recently, changes in tree mortality have been observed in forests around the globe, which could profoundly affect ecosystem functioning and services provisioning to society. We describe continental-scale patterns of recent tree mortality from the only consistent pan-European forest monitoring network, identifying recent mortality hotspots in southern and northern Europe. Analyzing 925,462 annual observations of 235,895 trees between 2000 and 2012, we determine the influence of climate variability and tree age on interannual variation in tree mortality using Cox proportional hazard models. Warm summers as well as high seasonal variability in precipitation increased the likelihood of tree death. However, our data also suggest that reduced cold-induced mortality could compensate increased mortality related to peak temperatures in a warming climate. Besides climate variability, age was an important driver of tree mortality, with individual mortality probability decreasing with age over the first century of a trees life. A considerable portion of the observed variation in tree mortality could be explained by satellite-derived net primary productivity, suggesting that widely available remote sensing products can be used as an early warning indicator of widespread tree mortality. Our findings advance the understanding of patterns of large-scale tree mortality by demonstrating the influence of seasonal and diurnal climate variation, and highlight the potential of state-of-the-art remote sensing to anticipate an increased likelihood of tree mortality in space and time.

Creating a regional MODIS satellite-driven net primary production dataset for european forests

Net primary production (NPP) is an important ecological metric for studying forest ecosystems and their carbon sequestration, for assessing the potential supply of food or timber and quantifying the impacts of climate change on ecosystems. The global MODIS NPP dataset using the MOD17 algorithm provides valuable information for monitoring NPP at 1-km resolution. Since coarse-resolution global climate data are used, the global dataset may contain uncertainties for Europe. We used a 1-km daily gridded European climate data set with the MOD17 algorithm to create the regional NPP dataset MODIS EURO. For evaluation of this new dataset, we compare MODIS EURO with terrestrial driven NPP from analyzing and harmonizing forest inventory data (NFI) from 196,434 plots in 12 European countries as well as the global MODIS NPP dataset for the years 2000 to 2012. Comparing these three NPP datasets, we found that the global MODIS NPP dataset differs from NFI NPP by 26%, while MODIS EURO only differs by 7%. MODIS EURO also agrees with NFI NPP across scales (from continental, regional to country) and gradients (elevation, location, tree age, dominant species, etc.). The agreement is particularly good for elevation, dominant species or tree height. This suggests that using improved climate data allows the MOD17 algorithm to provide realistic NPP estimates for Europe. Local discrepancies between MODIS EURO and NFI NPP can be related to differences in stand density due to forest management and the national carbon estimation methods. With this study, we provide a consistent, temporally continuous and spatially explicit productivity dataset for the years 2000 to 2012 on a 1-km resolution, which can be used to assess climate change impacts on ecosystems or the potential biomass supply of the European forests for an increasing bio-based economy. MODIS EURO data are made freely available at ftp://palantir.boku.ac.at/Public/MODIS_EURO.

Modeling the CO2-effects of forest management and wood usage on a regional basis

BackgroundAt the 15th Conference of Parties of the UN Framework Convention on Climate Change, Copenhagen, 2009, harvested wood products were identified as an additional carbon pool. This modification eliminates inconsistencies in greenhouse gas reporting by recognizing the role of the forest and timber sector in the global carbon cycle. Any additional CO2-effects related to wood usage are not considered by this modification. This results in a downward bias when the contribution of the forest and timber sector to climate change mitigation is assessed. The following article analyses the overall contribution to climate protection made by the forest management and wood utilization through CO2-emissions reduction using an example from the German state of North Rhine-Westphalia. Based on long term study periods (2011 to 2050 and 2100, respectively). Various alternative scenarios for forest management and wood usage are presented.ResultsIn the mid- to long-term (2050 and 2100, respectively) the net climate protection function of scenarios with varying levels of wood usage is higher than in scenarios without any wood usage. This is not observed for all scenarios on short and mid term evaluations.The advantages of wood usage are evident although the simulations resulted in high values for forest storage in the C pools. Even the carbon sink effect due to temporal accumulation of deadwood during the period from 2011 to 2100 is outbalanced by the potential of wood usage effects.ConclusionsA full assessment of the CO2-effects of the forest management requires an assessment of the forest supplemented with an assessment of the effects of wood usage. CO2-emission reductions through both fuel and material substitution as well as CO2 sink in wood products need to be considered.An integrated assessment of the climate protection function based on the analysis of the study’s scenarios provides decision parameters for a strategic approach to climate protection with regard to forest management and wood use at regional and national levels.The short-term evaluation of subsystems can be misleading, rendering long-term evaluations (until 2100, or even longer) more effective. This is also consistent with the inherently long-term perspective of forest management decisions and measures.

Land- und Forstwirtschaft, Fischerei

Land‐ und Forstwirtschaft sind zusammen mit der Fischerei ein wichtiger Wirtschaftsfaktor der Metropolregion Hamburg (MRH). In den dorflichen und weit von der Hansestadt entfernten Regionen ist die Landwirtschaft ein bedeutender Arbeitgeber (Schulze et al. 2011; Statistisches Amt fur Hamburg und Schleswig Holstein 2013; Statistische Amter des Bundes und der Lander 2015). Fischerei, Land‐ und Forstwirtschaft tragen etwa 1 % zur Bruttowertschopfung der MRH bei, wobei der Anteil in den Landkreisen Luchow‐Dannenberg und Ludwigslust‐Parchim bei uber 5 % liegt (Tab. 7.1). Die geringsten Beitrage zur Bruttowertschopfung (rund 0,1 %) werden in den kreisfreien Stadten Lubeck und Hamburg erzielt. In Hamburg werden rund 6 % der gesamten Bruttowertschopfung der Land‐ und Forstwirtschaft und Fischerei erzielt. Dieser im Vergleich zur forst‐ und landwirtschaftlichen Flache hohe Anteil an der Bruttowertschopfung ist auf die Ausrichtung auf den wenig flachenintensiven und hoch produktiven Gartenbau zuruckzufuhren. Aufgrund der Unterschiede zwischen terrestrischer und maritimer Biosphare sowie der dadurch bedingten unterschiedlichen Produktionsbedingungen werden im Folgenden Land‐ und Forstwirtschaft und Fischerei getrennt dargestellt. Im Gegensatz zum Klimabericht 2011 (von Storch und Claussen 2011) befasst sich der Teilbereich Land‐ und Forstwirtschaft intensiv mit Waldern, deren langfristige Produktionszeitraume eine besondere Herausforderung fur die Anpassung an erwartete zukunftige Klimaveranderungen darstellen.

EFO-LCI: A New Life Cycle Inventory Database of Forestry Operations in Europe

Life cycle assessment (LCA) has become a common methodology to analyze environmental impacts of forestry systems. Although LCA has been widely applied to forestry since the 90s, the LCAs are still often based on generic Life Cycle Inventory (LCI). With the purpose of improving LCA practices in the forestry sector, we developed a European Life Cycle Inventory of Forestry Operations (EFO-LCI) and analyzed the available information to check if within the European forestry sector national differences really exist. We classified the European forests on the basis of “Forest Units” (combinations of tree species and silvicultural practices). For each Forest Unit, we constructed the LCI of their forest management practices on the basis of a questionnaire filled out by national silvicultural experts. We analyzed the data reported to evaluate how they vary over Europe and how they affect LCA results and made freely available the inventory data collected for future use. The study shows important variability in rotation length, type of regeneration, amount and assortments of wood products harvested, and machinery used due to the differences in management practices. The existing variability on these activities sensibly affect LCA results of forestry practices and raw wood production. Although it is practically unfeasible to collect site-specific data for all the LCAs involving forest-based products, the use of less generic LCI data of forestry practice is desirable to improve the reliability of the studies. With the release of EFO-LCI we made a step toward the construction of regionalized LCI for the European forestry sector.

Operational assessment of aboveground tree volume and biomass by terrestrial laser scanning

Biomass extraction from branches by TLS systems is not affected by scanning distance.A straightforward algorithm is presented that simplifies biomass measurements of complex branch geometries using TLS.The combination of biomass measurements from individual scan positions by averaging provides reliable biomass figures. The assessment of aboveground tree biomass (AGB) is essential to the evaluation of tree populations in forests, open landscapes, and urban areas. The predominant method used to determine AGB relies on error-prone functions derived from the statistical relationships of tree attributes and biomass. Terrestrial laser scanning (TLS) offers a new approach that replaces statistical AGB estimates with consistent measurements.Aboveground tree biomass (AGB) comprises stems and branches. While the biomass assessment of stems is straightforward, TLS measurements of tree crowns are far more complex because of branch overlapping. Because placing reflecting targets in the crowns of tall standing trees is impractical, yet necessary for merging the point clouds from different laser scan positions, TLS measurements often fail in operational applications.This study introduces a straightforward algorithm that simplifies biomass measurements of complex branch geometries using TLS and derives AGB by averaging measurements from individual scanning positions. We verified our approach through an experimental setup of branching systems with different complexities and known true biomass volumes. The results show that biomass extraction from branches by TLS systems is not affected by scanning distance. The combination of biomass measurements from individual scanning positions by averaging provides reliable biomass figures. Compared to the known true biomass figures, the overall accuracies achieved by our approach are 95% or higher, which brings the operational application of TLS for AGB measurements within tangible reach.

Effects Evaluation and Risk Assessment of Air Pollutants Deposition at European Monitoring Sites of the ICP Forests

The study presents modelled critical deposition load exceedances for over 4,700 representatively selected forest plots in 21 European countries. It is based on measured soil data, different deposition scenarios and an application of the Simple Mass Balance (SMB) model. Effects of climate change on critical loads and exceedances are presented for 108 intensive monitoring plots in 17 countries. Results suggest hardly any more exceedances of critical loads for acidity in the near future. In contrast, even a maximum feasible emission reduction scenario which will leave 10 % of the forest sites unprotected against nitrogen effects by the year 2020. Full implementation of existing clean air legislation will result in 20 % of unprotected forest sites. Forests are less sensitive compared to other ecosystems as for these areas with exceedances are up to 58 %. Under a climate change scenario, decreasing critical loads suggest increasing sensitivity towards nutrient nitrogen inputs. When comparing critical load exceedances over the period 2020–2100, the share of ‘safe’ sites is assumed to decrease from 60 % (constant climate) to 50 % (climate change).