Albrecht A.T.,Forest Research Institute Baden Wuerttemberg |
Fortin M.,Agro ParisTech |
Kohnle U.,Forest Research Institute Baden Wuerttemberg |
Ningre F.,French National Institute for Agricultural Research
Environmental Modelling and Software | Year: 2015
The purpose of this study was to develop, test and evaluate a software prototype capable of modeling forest growth in consideration of winter storm disturbance and to simulate storm damage in forests under different forest management regimes. The results of a test application showed that simulated storm damage was more strongly influenced by the input data (e.g. tree species and tree height) than by the different forest management regimes. However, early, intense thinnings as well as reducing target diameters by 10% led to reduced storm damage, with decreases as large as 50% of the damage in certain forest stands. The coupled modeling framework was able to simulate interactions between forest growth, storm damage and forest management regimes. Further testing of the prototype appears necessary to investigate a wider range of tree species, soil and site conditions. Also, the use of computational system resources needs improvement. © 2015 Elsevier Ltd.
PubMed | University of British Columbia, Albert Ludwigs University of Freiburg, Scion Research, Michigan State University and 7 more.
Type: Journal Article | Journal: Physical review. E | Year: 2017
Virot etal. [E. Virot et al., Phys. Rev. E 93, 023001 (2016)10.1103/PhysRevE.93.023001] assert that the critical wind speed at which 50% of all trees in a population break is 42 m/s, regardless of tree characteristics. We show that empirical data do not support this assertion, and that the assumptions underlying the theory used by Virot etal. are inconsistent with the biomechanics of trees.
Sucker C.,Forest Research Institute Baden Wuerttemberg |
Krause K.,Swiss Federal Institute of forest
IForest | Year: 2010
Since the beginning of the 1990s, an increase in dissolved organic carbon (DOC) has been observed in rivers and lakes in various parts of Europe and North America. The processes responsible for the increased DOC concentrations are complex and not entirely understood. The aim of this review is to provide an overview of the recent debate about increases in the DOC concentrations in surface water and their possible drivers. © iForest-Biogeosciences and Forestry.
Metzler B.,Forest Research Institute Baden Wuerttemberg |
Hecht U.,Forest Research Institute Baden Wuerttemberg |
Nill M.,Forest Research Institute Baden Wuerttemberg |
Bruchert F.,Forest Research Institute Baden Wuerttemberg |
And 2 more authors.
Forest Ecology and Management | Year: 2012
In order to compare Norway spruce (. Picea abies) and silver fir (. Abies alba) with respect to susceptibility to wound colonizing fungi, wood stains and rots, experimental cortical lesions were created in situ on mature trees. The study was performed with 40 Norway spruce and 39 silver fir. Two years after the infliction of the lesions the experiment was evaluated with respect to fungal colonization. The most common fungi isolated from xylem beneath the wound area of Norway spruce were Neonectria fuckeliana, Stereum sanguinolentum and Leptodontium beauverioides. Overall, fungal wound infection rate of Norway spruce was 4.6-fold higher compared to silver fir. Only 7% of the Norway spruce stems were sterile in opposite to 67% sterile silver fir trees. Wood decay fungi were isolated from 28% of Norway spruce trees compared to only 8% of silver fir. Accordingly, discolorations in the wood of Norway spruce were clearly larger in their extent. Silver fir mostly displayed only superficial discoloration. On the other hand, the impact on xylem of both tree species was only slightly influenced by the season of wounding (May versus October). Histological examination revealed that in Norway spruce fungal infections occurred through regular resin channels which appeared to be easily colonized by fungi facilitating long distance growth of fungal hyphae. In contrast, traumatic resin ducts formed by both tree species were not found to be infected by fungi. Very obviously, silver fir - being void of primary resin channels - was able to seal injuries by deposition of accessory substances close to the surface of the exposed xylem, thus inhibiting sapwood dehydration and impeding xylem colonization by fungi. For Norway spruce, computer tomography strongly indicated specific sapwood desiccation in the wound region, while in silver fir no such desiccation could be found. © 2012 Elsevier B.V..
Hagen R.,Forest Research Institute Baden Wuerttemberg |
Hagen R.,Albert Ludwigs University of Freiburg |
Heurich M.,Bavarian Forest National Park |
Kroschel M.,Forest Research Institute Baden Wuerttemberg |
And 2 more authors.
Science of the Total Environment | Year: 2013
Human induced land use changes negatively impact the viability of many wildlife species through habitat modifications and mortality, while some species seem to benefit from it. Roe deer (. Capreolus capreolus), a wide spread ungulate increased both its abundance and range throughout Europe. This pattern is also reflected in the increasing hunting bags over the last 40. years. Such a development raises questions about the relationship between human hunting and population dynamics and, in particular, about the potential of human hunting to control related populations. We analysed and reconstructed annual hunting bags of roe deer for three federal states of northern Germany, Brandenburg, Lower Saxony and Mecklenburg West Pomerania for the years 1972 to 2011. Since 1992 the hunting bags from these three states are significantly higher than those reported for the years 1972-1991. Our reconstruction takes into consideration effects of climate variability, expressed by inter-annual changes in the North Atlantic Oscillation and impacts from rapeseed and wheat cultivation. We found that severe winters, which are indicated by negative values of the North Atlantic Oscillation during the months December-March, directly, or with a time lag of two years affect the number of deer shot. In contrast, an increase in the area used for rapeseed cultivation coincides with higher numbers of roe deer shot, with respect to the overall mean value. Consequently, we recommend that wildlife management addresses changes in large scale processes including land use pattern and climate variability. © 2013 Elsevier B.V.
Vonderach C.,Forest Research Institute Baden Wuerttemberg |
Voegtle T.,Karlsruhe Institute of Technology |
Adler P.,Forest Research Institute Baden Wuerttemberg
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2012
The importance of single trees and the determination of related parameters has been recognized in recent years, e.g. for forest inventories or management. For urban areas an increasing interest in the data acquisition of trees can be observed concerning aspects like urban climate, CO2 balance, and environmental protection. Urban trees differ significantly from natural systems with regard to the site conditions (e.g. technogenic soils, contaminants, lower groundwater level, regular disturbance), climate (increased temperature, reduced humidity) and species composition and arrangement (habitus and health status) and therefore allometric relations cannot be transferred from natural sites to urban areas. To overcome this problem an extended approach was developed for a fast and non-destructive extraction of branch volume, DBH (diameter at breast height) and height of single trees from point clouds of terrestrial laser scanning (TLS). For data acquisition, the trees were scanned with highest scan resolution from several (up to five) positions located around the tree. The resulting point clouds (20 to 60 million points) are analysed with an algorithm based on voxel (volume elements) structure, leading to an appropriate data reduction. In a first step, two kinds of noise reduction are carried out: the elimination of isolated voxels as well as voxels with marginal point density. To obtain correct volume estimates, the voxels inside the stem and branches (interior voxels) where voxels contain no laser points must be regarded. For this filling process, an easy and robust approach was developed based on a layer-wise (horizontal layers of the voxel structure) intersection of four orthogonal viewing directions. However, this procedure also generates several erroneous "phantom" voxels, which have to be eliminated. For this purpose the previous approach was extended by a special region growing algorithm. In a final step the volume is determined layer-wise based on the extracted branch areas Ai of this horizontal cross-section multiplied by the thickness of the voxel layer. A significant improvement of this method could be obtained by a reasonable determination of the threshold for excluding sparsely filled voxels for noise reduction which can be defined based on the function change of filled voxels. Field measurements were used to validate this method. For a quality assessment nine deciduous trees were selected for control and were scanned before felling and weighing. The results are in good accordance to the control trees within a range of only -5.1% to +14.3%. The determined DBH values show only minor deviations, while the heights of trees are systematically underestimated, mainly due to field measurements. Possible error sources including gaps in surface voxels, influence of thin twigs and others are discussed in detail and several improvements of this approach are suggested. The advantages of the algorithm are the robustness and simple structure as well as the quality of the results obtained. The drawbacks are the high effort both in data acquisition and analysis, even if a remarkable data reduction can be obtained by the voxel structure.
Enderle R.,Forest Research Institute Baden Wuerttemberg |
Peters F.,Forest Research Institute Baden Wuerttemberg |
Nakou A.,Forest Research Institute Baden Wuerttemberg |
Metzler B.,Forest Research Institute Baden Wuerttemberg
European Journal of Forest Research | Year: 2013
European ash (Fraxinus excelsior) is threatened by Hymenoscyphus pseudoalbidus, the agent of ash dieback disease. Beside ordinary ash dieback symptoms, collar rots have been reported on declining ashes as an additional problem of increasing severity. Since 2009, ash dieback has been surveyed annually in a provenance trial on four different sites in southwest Germany (Metzler et al. in Ger J For Res 183:168-180, 2012). The trial was established in 2005. Data of tree growth, ash dieback symptoms and collar rot prevalence were collected by surveying the trial in summer 2012 and compared with previously published data of the trial. Evaluations revealed a continuous and considerable increase in dieback severity since 2009. The results suggest that the infection process has not come to a standstill yet. Up to 2012, 6 % of the trees remained symptomless, whereas mortality added up to 9 %. There were significant differences in ash dieback severity between the investigated provenances. Collar rot prevalence ranged from 19 to 59 % between study sites. Moreover, high spatial dependency of collar rot prevalence could be detected within sites. Collar rots were more abundant on trees of severe ash dieback intensity, but could also be detected on 15 % of otherwise healthy trees. Mycelium from collar rots could be identified by means of RFLP analyses and sequencing of the ITS region as most likely belonging to Armillaria gallica. The possible roles of Armillaria spp. and H. pseudoalbidus in collar rot formation are discussed. © 2013 Springer-Verlag Berlin Heidelberg.
Hartmann P.,University of Kiel |
Hartmann P.,Forest Research Institute Baden Wuerttemberg |
Zink A.,University of Kiel |
Fleige H.,University of Kiel |
Horn R.,University of Kiel
Soil and Tillage Research | Year: 2012
In this study we determined wheeling (external loads of 6.3. Mg by 10 times wheeling) and tillage effects (conventional and conservation tillage) on the soil hydraulic properties of Stagnic Luvisols in Northwest Germany and modeled the soil water balance's reaction on both loading and changing climatic conditions. Due to the mechanical stress applied by loading, physical properties changed distinctly in the top Ap-horizons and the subsequent Eg-horizons at both tillage systems. Especially pore size distributions and soil hydraulic conductivities were affected. The Btg horizons did not show changes due to loading. Soil water balance was measured with soil tensiometers during one growing period and the following autumn and was modeled with Hydrus 1D for loaded and unloaded conditions under winter wheat for three different periods (1991-2000; 2051-2060; 2091-2100) based on a regional A1B climate scenario. At the loaded sites we found an increase of actual transpiration rates in the growing period. As a consequence of stronger drying and changed hydraulic properties, rewetting in autumn and winter was retarded and less complete on average. Furthermore, simulations indicated an increase of the variability of matric potentials. Consequently, compaction might result in a higher drought risk and a higher susceptibility for water logging in spring, which may result in less favorable soil conditions and plant growth. Reactions of soil water balance on changing climatic conditions were comparable for all loading variants and tillage systems. Predicted changes in precipitation (in general: summer -, winter +) and temperature (+) would result in a reduction of transpiration rates in the growing period while the climatic water balance in autumn and winter would increase distinctly. © 2012 Elsevier B.V.
Nakou A.,Forest Research Institute Baden Wuerttemberg |
Sauter U.H.,Forest Research Institute Baden Wuerttemberg |
Kohnle U.,Forest Research Institute Baden Wuerttemberg
Annals of Forest Science | Year: 2016
Key message: We provided a precise quantitative analysis of the factors at the origin of bark damage during harvesting operations and developed a model able to predict them accurately. The major factors were the distance of trees to skid trails, the intensity of removals, the harvesting system as well as the interactions between the distance of trees to skid trails with harvesting systems, the average skidding distance, the tree species and tree height. • Context: During timber harvesting, trees in the remaining stand may suffer bark damage resulting from tree-felling or log manipulation. Although a multitude of case studies and empirical observations provide qualitative and quantitative information with respect to the potential causal factors, the basic quantitative relationship between major factors of influence and the resulting degree of bark damage remains largely unclear. • Aims: The objective was to provide a precise quantitative analysis of impact factors explaining the occurrence of bark damage during harvesting operations. • Methods: Three different modelling approaches were tested: boosted regression tree (BRT), a generalised linear mixed effects model (GLMM) and Bayesian Markov chain Monte Carlo generalised linear mixed models (MCMCglmm). • Results: The major factors with a significant impact on the occurrence of bark damage were the distance of trees to skid trails, the intensity of removals, the harvesting system and the interaction term between the distance of trees to skid trails with harvesting systems, average skidding distance, tree species and tree height. • Conclusion: The final model includes the relevant major factors impacting on the infliction of bark damage during practical harvesting operations. Furthermore, it discriminates well with respect to the occurrence of bark damage, and it provides managers with a rational and conclusive tool for optimising harvesting operations. © 2015, INRA and Springer-Verlag France.
Schumacher J.,Forest Research Institute Baden Wuerttemberg
EPPO Bulletin | Year: 2011
Ash dieback is currently one of the most important tree diseases in Germany. A countrywide distribution is already assumed. Trees of all ages on various site types are affected in forests and the landscape, as well as in nurseries and urban plantings. Initially economic losses were most severe in Northern Germany, but damage has increased in all regions. In several parts of Germany, surveys have been started during the past few years. In North-East Germany, where the disease was first observed, conditions on various sites were compared to identify the characteristics which influence the disease occurrence and severity. In addition, laboratory investigations were carried out with a large number of coeval ash saplings to study the infection rate, invasion and spread strategy of the causal agent inside plant tissues, as well as the role of soil-borne Oomycetes as possible primary or accompanying organisms in the disease process. The experiments presented here show that the fungus is able to spread very effectively in wood as a parasite and does not originate from the root system. The results confirm the dominant role of Chalarafraxinea and rule out the importance of pathogenic Oomycetes. © 2011 The Author. Journal compilation © 2011 OEPP/EPPO.