Bavarian State Institute of Forestry LWF

Freising, Germany

Bavarian State Institute of Forestry LWF

Freising, Germany
Time filter
Source Type

Hofmann N.,Bavarian State Institute of Forestry LWF | Schulmeyer F.,Bavarian State Institute of Forestry LWF | Borchert H.,Bavarian State Institute of Forestry LWF
Biomass and Bioenergy | Year: 2017

The storage of wood chips is important for the biomass supply chain as it compensates for temporal differences in production and consumption. Typical storage-related problems are dry matter and energy losses due to microbial activity.In extensive field trials, we investigated the storage of spruce wood chips from forest residues (FRC) and from energy roundwood (ERC) with and without rain protection under Central European conditions. Additionally, we examined the storage of unchipped piles.The results indicate that the investigated factors, i. e. storage duration, season, assortment and rain protection, have a statistically significant influence on moisture content and dry matter loss of wood chips. During five months of storage, the highest decline in moisture content was 22.6 %-points, the highest dry matter loss 11.1 %. In winter, energy losses reached up to 11.3 %. In summer, energy contents did not change or even increased slightly (max. 4.7 %). Pile temperature and dry matter losses were significantly positively correlated in FRC. Formation of different layers within the piles could be detected. Storage performance was better in unchipped than in chipped energy roundwood. Storage of unchipped forest residues was not beneficial concerning energy content, but fuel quality increased due to reduced ash and fine particle content.Clear best practice recommendations could be drawn regarding wood chip storage under Central European conditions. During winter, FRC should be stored with rain protection or as short as possible while during a dry and warm summer, wood chips can be stored with only few restrictions. © 2017 Elsevier Ltd.

Tian J.,German Aerospace Center | Schneider T.,TU Munich | Straub C.,Bavarian State Institute of Forestry LWF | Kugler F.,German Aerospace Center | Reinartz P.,German Aerospace Center
Remote Sensing | Year: 2017

Digital surface models (DSMs) derived from spaceborne and airborne sensors enable the monitoring of the vertical structures for forests in large areas. Nevertheless, due to the lack of an objective performance assessment for this task, it is difficult to select the most appropriate data source for DSM generation. In order to fill this gap, this paper performs change detection analysis including forest decrease and tree growth. The accuracy of the DSMs is evaluated by comparison with measured tree heights from inventory plots (field data). In addition, the DSMs are compared with LiDAR data to perform a pixel-wise quality assessment. DSMs from four different satellite stereo sensors (ALOS/PRISM, Cartosat-1, RapidEye andWorldView-2), one satellite InSAR sensor (TanDEM-X), two aerial stereo camera systems (HRSC and UltraCam) and two airborne laser scanning datasets with different point densities are adopted for the comparison. The case study is a complex central European temperate forest close to Traunstein in Bavaria, Germany. As a major experimental result, the quality of the DSM is found to be robust to variations in image resolution, especially when the forest density is high. The forest decrease results confirm that besides aerial photogrammetry data, very high resolution satellite data, such asWorldView-2, can deliver results with comparable quality as the ones derived from LiDAR, followed by TanDEM-X and Cartosat DSMs. The quality of the DSMs derived from ALOS and Rapid-Eye data is lower, but the main changes are still correctly highlighted. Moreover, the vertical tree growth and their relationship with tree height are analyzed. The major tree height in the study site is between 15 and 30 m and the periodic annual increments (PAIs) are in the range of 0.30-0.50 m. © 2017 by the authors.

Kuptz D.,Technology and Support Center | Dietz E.,Bavarian State Institute of Forestry LWF | Blum U.,Bavarian State Institute of Forestry LWF | Schulmeyer F.,Bavarian State Institute of Forestry LWF | And 2 more authors.
European Biomass Conference and Exhibition Proceedings | Year: 2016

Critical chemical elements such as nitrogen (N), sulphur (S), chloride (Cl), potassium (K) or heavy metals might determine high temperature corrosion, emission behavior and slagging of solid biofuels during combustion. Recently developed biomass fuel indexes may help to pre-evaluate fuel behavior during combustion. In total, 92 samples of wood chips (n = 75), of unchipped material (n = 11) and of twigs and needles (n = 6) were collected and analyzed for elemental composition (As, Ca, Cd, Cl, Cr, Cu, Hg, K, Mg, N, Na, Ni, Pb, S, Si, Zn). Biomass fuel indexes were calculated from the results to pre-evaluate NOX and particle emissions, high temperature corrosion, K release and slagging behavior. Wood chips from natural wood showed low concentrations of critical chemical elements. With increasing shares of mineral soil, critical elements also increased. Biomass fuel indexes such as the sum of aerosol forming elements (K, Na, Pb, Zn) or the molar Si/(Ca+Mg) ratio for ash-melting behavior indicated that biomass fuels without contamination with mineral soil, road salt or other anthropogenic waste can be considered uncritical for combustion. © 2016 ETA-Florence Renewable Energies.

Dietz E.,Bavarian State Institute of Forestry LWF | Blum U.,Bavarian State Institute of Forestry LWF | Schulmeyer F.,Bavarian State Institute of Forestry LWF | Borchert H.,Bavarian State Institute of Forestry LWF
European Biomass Conference and Exhibition Proceedings | Year: 2016

Critical elements such as chloride (Cl), potassium (K), silicon (Si) or heavy metals might determine high temperature corrosion, emission behavior and slagging of solid biofuels during combustion. Using the fact that plant material contains distinctly less iron (Fe) than mineral soils and vice versa manganese (Mn) in plant tissue is significant higher than in soil material and that the Al-content of plant biomass is limited, indexes could be created to classify wood chips into “contaminated with soil” and uncontaminated “biomass” by building ratios of Fe/Mn and Al/200 Thus, “biomass fuel indexes for the contamination with mineral soil” (BFICS) were developed. Plausibility checks were carried out, using tree biomass of various species und soil datasets from other research projects. They showed that for Pinus sylvestris an adapted Al-index is necessary. 2.7 % of the tree samples, Pinus sylvestris excluded, exceed the threshold value of 1 for the Fe/Mn-index and only 3.3 % exceed 1 for Al/200. The newly developed BFICS are useful to determine the source of critical elements for combustion, for aerosol formation, to detect high shares of non-combustible material and to prove the effectivity of pre-treatments like screening. © 2016 ETA-Florence Renewable Energies.

Neuner S.,TU Munich | Albrecht A.,Forest Research Institute Baden Wurttemberg | Cullmann D.,Forest Research Institute Baden Wurttemberg | Engels F.,Research Institute for Forest Ecology and Forestry Rhineland Palatinate FAWF | And 8 more authors.
Global Change Biology | Year: 2015

Shifts in tree species distributions caused by climatic change are expected to cause severe losses in the economic value of European forestland. However, this projection disregards potential adaptation options such as tree species conversion, shorter production periods, or establishment of mixed species forests. The effect of tree species mixture has, as yet, not been quantitatively investigated for its potential to mitigate future increases in production risks. For the first time, we use survival time analysis to assess the effects of climate, species mixture and soil condition on survival probabilities for Norway spruce and European beech. Accelerated Failure Time (AFT) models based on an extensive dataset of almost 65 000 trees from the European Forest Damage Survey (FDS) - part of the European-wide Level I monitoring network - predicted a 24% decrease in survival probability for Norway spruce in pure stands at age 120 when unfavorable changes in climate conditions were assumed. Increasing species admixture greatly reduced the negative effects of unfavorable climate conditions, resulting in a decline in survival probabilities of only 7%. We conclude that future studies of forest management under climate change as well as forest policy measures need to take this, as yet unconsidered, strongly advantageous effect of tree species mixture into account. © 2014 John Wiley & Sons Ltd.

Gherghel F.,University of Marburg | Fussi B.,Bavarian Office for Forest Seeding and Planting ASP | Donges K.,University of Marburg | Haustein M.,University of Marburg | And 8 more authors.
Forest Pathology | Year: 2014

Ash dieback, caused by the pathogen Hymenoscyphus pseudoalbidus, is an emerging lethal disease of Fraxinus excelsior in large parts of Europe. To develop a method for the early detection of H. pseudoalbidus, we designed primers for 46 microsatellites (simple sequence repeats, SSRs) of the pathogen. Seven pairs of primers (SSR38, SSR58, SSR114, SSR198, SSR206, SSR211 and SSR212) were found to bind only to the genome of H. pseudoalbidus, but not to the genome of H. albidus or to 52 different fungal endophytes isolated from F. excelsior and F. angustifolia. Using these seven primer pairs, H. pseudoalbidus was identified in fruiting bodies and different types of ash tissues including dead leaves, dead petioles and discoloured or non-discoloured wood. Along one twig, H. pseudoalbidus was detected at different levels of intensity, which depended on the distance from symptomatic tissue. The detection limit was 0.9-1.8 pg of genomic DNA per PCR. Of 50 analysed commercially available seedlings, six were infected with H. pseudoalbidus. Two SSR loci (SSR198 and SSR211) showed fragment length polymorphism. Our results showed that the new primers not only provide an easy and inexpensive means of detecting H. pseudoalbidus in ash tissues, but can also provide information on the genetic heterogeneity of the species. © 2013 Blackwell Verlag GmbH.

Dolos K.,Karlsruhe Institute of Technology | Mette T.,Bavarian State Institute of Forestry LWF | Wellstein C.,Sudan University of Science and Technology
Forest Ecology and Management | Year: 2016

Forests of temperate Europe are climate sensitive ecosystems, and the current balance between the tree species will shift as climate becomes warmer and potentially drier. Especially changes in the dominant species have a strong impact on forest ecosystems because they fundamentally change life conditions of plants and animals living in the forest. Mette et al. (2013) introduced the climatic turning point (CTP) as a concept that marks the climatic conditions where such a change in species dominance is expected to occur. While they modelled the CTP for European beech (Fagus sylvatica) and sessile oak (Quercus petraea) from environmentally sensitive forest growth models, this study determined the CTP between beech and oak from national forest inventories in Western Europe. We ask (1) under which climate conditions the inventory-based CTP occurs, (2) whether it is modified by soil type and (3) how it differs from other CTP references like the Ellenberg quotient (Ellenberg, 1963).The CTP from beech to oak occurred approximately at mean annual temperatures above 8-9 °C if annual precipitation was below 600 mm and rose to 11-12 °C for annual precipitation exceeding 900 mm. This relation was strongly modified by soil type. Compared to Ellenberg (1963) and Mette et al. (2013), oak replaced beech at far more moderate climatic conditions (EQ 20-30). This can be attributed to the silvicultural history of forest stands: the inventory-based CTP signal carries the century old anthropogenic preference for oak.We expand the CTP concept that was until now based on natural competition by a "silvicultural" CTP that is contained in large-scale inventory data. It thereby implicitly incorporates the question how silviculture and social-cultural values impact the balance between species. Climate change projections indeed suggested that large parts of Western Europe will cross the silvicultural CTP. © 2016 Elsevier B.V..

Baumgarten M.,TU Munich | Baumgarten M.,Bavarian State Institute of Forestry LWF | Weis W.,Bavarian State Institute of Forestry LWF | Weis W.,TU Munich | And 3 more authors.
European Journal of Forest Research | Year: 2014

The assessment of forest transpiration rates is crucial for determining plant-available soil water consumption and drought risk of trees. Xylem sap flux measurements have been used increasingly to quantify stand transpiration in forest ecosystems. Here, we compare this empirical approach with hydrological modeling on the basis of a stand transpiration dataset of adult beech (Fagus sylvatica), which was acquired across Bavaria, Germany, at eight forest sites. Xylem sap flux sensors were installed in five dominant trees each. Two tree to stand upscaling approaches, related to site-specific (1) sapwood area or (2) to leaf area index, were compared. The outcome was examined each in relation to process-based stand hydrological modeling, using LWF-BROOK90. Distinct relationships between tree diameter at breast height (1.30 m) and sapwood area-weighted sap flux along the radial profile became apparent across the study sites, confirming a generic allometric basis for stand-level upscaling of transpiration. The two upscaling approaches did not differ in outcome, representatively covering stand structure for comparison with modeling. Differential analysis yielded high agreement between the empirical and modeling approaches throughout most of the study period, although LWF-BROOK90 tended to overestimate sap flux measurements under low soil moisture. The two empirical approaches proved reliable for even-aged beech stands, as performance under high stand-structural heterogeneity awaits clarification. Findings advance stand-level hydrological modeling regarding coverage of stomatal behavior during temporary limitation in water availability. © 2014 Springer-Verlag Berlin Heidelberg.

Brandl S.,Bavarian State Institute of Forestry LWF | Falk W.,Bavarian State Institute of Forestry LWF | Klemmt H.-J.,Bavarian State Institute of Forestry LWF | Stricker G.,Ludwig Maximilians University of Munich | And 3 more authors.
Forests | Year: 2014

Combining national forest inventory (NFI) data with digital site maps of high resolution enables spatially explicit predictions of site productivity. The aim of this study is to explore the possibilities and limitations of this database to analyze the environmental dependency of height-growth of Norway spruce and to predict site index (SI) on a scale that is relevant for local forest management. The study region is the German federal state of Bavaria. The exploratory methods comprise significance tests and hypervolume-analysis. SI is modeled with a Generalized Additive Model (GAM). In a second step the residuals are modeled using Boosted Regression Trees (BRT). The interaction between temperature regime and water supply strongly determined height growth. At sites with very similar temperature regime and water supply, greater heights were reached if the depth gradient of base saturation was favorable. Statistical model criteria (Double Penalty Selection, AIC) preferred composite variables for water supply and the supply of basic cations. The ability to predict SI on a local scale was limited due to the difficulty to integrate soil variables into the model. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

Falk W.,Bavarian State Institute of Forestry LWF | Mellert K.H.,Agwa Umweltberatung
Journal of Vegetation Science | Year: 2011

Questions: How can SDMs be adopted as a tool for forest management planning? Based on presence-absence data, which modelling techniques are appropriate to determine species potential distribution for forest management planning under climate change? Do species distribution models (SDMs) agree with expert knowledge about species distribution and species traits? How can forest researcher deal with distribution data of a species whose distribution is heavily affected by human impacts? Location: Bavaria (Southern Germany). Methods: We used SDMs based on the Second National Forest Inventory from 2002 (4 × 4km grid) containing presence-absence data of tree species to identify species environment relationships ('Grinnellian niche'). As an example, the distribution of silver fir (Abies alba Mill.) was modelled. Site condition data of the plots were derived from solar radiation, climate and soil maps. Models applied were boosted regression trees (BRT) and generalised additive models (GAM). Model predictions were compared with an expert based evaluation of the potential natural vegetation and were run with a climate change scenario (WETTREG B1) to project future distribution of silver fir. Results: Both models discriminated well between presence and absence of silver fir but underestimated the potential distribution. The BRT model was more sensitive to local site conditions in the present data, but the GAM showed more generality. The truncated response curves and high uncertainties of predictions at the edge of the site spectrum indicated a low data density and that the data did not cover the whole niche space of silver fir. As indicated by validation with expert knowledge, the model output approached potential distribution by optimizing true positive predictions. The classification of SDMs output into risk classes allowed model evaluation and interpretation. Predictions of GAM and BRT under the climate change scenario showed high accordance and therefore, low uncertainty. Finally, large areas of Bavaria are described to have a high risk of silver fir cultivation in future. Conclusions: SDMs are especially interesting as a decision basis for forest management because some of the general limitations of static modelling approaches are not relevant in this context. Limitations of forest inventory data can be partially overcome by using information on the potential distribution of species. The transferability of the models to future scenarios strongly depends on the spectrum and range of the training data sets and the depicted functional relationships. In order to improve the models and reduce the uncertainties, we need to improve the soil data and cover the whole niche space of silver fir. © 2011 International Association for Vegetation Science.

Loading Bavarian State Institute of Forestry LWF collaborators
Loading Bavarian State Institute of Forestry LWF collaborators