University of Applied Forest science

Rottenburg, Germany

University of Applied Forest science

Rottenburg, Germany
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Hein S.,University of Applied Forest science | Hein S.,Forest Research Institute of Baden Wuerttemberg | Weiskittel A.R.,University of Maine, United States
European Journal of Forest Research | Year: 2010

Models of binary outcomes are commonly used in forestry, but the predictions errors of these types of models are difficult to present effectively. In addition, most studies generally use a fixed value of 0.5 as the separation between events and non-events. The use of cutpoint analysis has been widely utilized in the health sciences and other fields, while it is relatively uncommon in the forestry literature. Cutpoint analysis involves locating the optimal value that minimizes prediction errors associated with binary outcomes. This case study illustrates the use of cutpoint analysis to improve a dynamic model of individual branch mortality. In this study, the use of cutpoint analysis increased the model specificity (prediction of events) from 77.8% (standard cutpoint of 0.5) to 90.3% (optimal cutpoint of 0.672). At the same time, the sensitivity of the model decreased only slightly and the false positive rate (non-event predicted as an event) was greatly decreased from 22.2 to 9.7%. In addition, the use of receiver operating characteristics (ROC) curves was an effective approach for evaluating prediction errors of models of binary outcomes. Cutpoint analysis is a simple yet effective method for improving predictions of binary outcomes and should be used more regularly, particularly when modelling the binary outcome of rare events such as mortality. © 2010 Springer-Verlag.

Danescu A.,Forest Research Institute of Baden Wurttemberg | Ehring A.,Forest Research Institute of Baden Wurttemberg | Bauhus J.,Albert Ludwigs University of Freiburg | Albrecht A.,Forest Research Institute of Baden Wurttemberg | Hein S.,University of Applied Forest science
Forest Ecology and Management | Year: 2015

The production of defect-free, high quality stem wood may be promoted through pruning of branches in hardwood species, yet this practice may also lead to wood defects, such as stem discoloration.Here, models to predict stem discoloration and the time of branch occlusion were developed for Acer pseudoplatanus L. (sycamore maple) and Fraxinus excelsior L. (common ash) based on a pruning experiment in southwest Germany. The dataset consisted of 449 completely occluded branches originating from 115 destructively sampled sycamore maple and common ash trees that had been pruned either in late winter or summer, or had not been pruned and underwent natural branch shedding instead. We analyzed these data with linear and generalized linear mixed-effects models to predict (1) the time until branch occlusion, (2) the length of branch discolorations and (3) the occurrence of discolorations in the stem wood. For all treatments, the time until complete branch occlusion was negatively related to stem radial increment during branch occlusion and positively related to the branch diameter in case of green pruning or the length of the dead branch portion in case of natural branch shedding. The extent of branch discoloration was positively correlated with branch diameter (green pruning) or the dead branch length (natural shedding), which was itself correlated to branch diameter. The probability of stem discoloration after pruning increased with branch diameter and showed large interspecific differences, with a much higher risk for common ash. Thresholds for decay risk based on pruned branch diameters are reported for each species. In both branch and stem discoloration models, there was no evidence of significant effects related to the time of pruning.When analyzing a subset of the original data containing only branches with diameters up to 30. mm, we found that green pruning significantly reduced the duration of branch occlusion. The extent of branch discoloration was positively related to branch diameter and occlusion time and was not affected by pruning treatment or species.Our results indicate that pruning reduces the duration of branch occlusion and, hence, has the potential to increase the proportion of defect-free wood. Furthermore, the duration of branch occlusion after artificial pruning should be minimized in order to reduce the risk of discoloration and decay. Therefore, green pruning should start early in the life of a tree when its branches are still thin and be applied only to vigorous trees that can occlude the wounds rapidly. © 2014 Elsevier B.V.

Heuck C.,University of Marburg | Brandl R.,University of Marburg | Albrecht J.,University of Marburg | Gottschalk T.K.,University of Applied Forest science
Journal of Ornithology | Year: 2013

Central Europe has the responsibility to protect the Red Kite Milvus milvus as it holds the majority (>50 % of all breeding pairs) of the global population. This entails the need for comprehensive knowledge of the birds' ecology and distribution. Currently, only little is known about the factors limiting both the global occurrence of the Red Kite and its distribution on regional scales. In this study we analysed the effect of land use on the breeding distribution of Red Kites throughout Germany, the species' core distribution area, using a distribution model. For the first time, an extensive data set was used for modelling comprising a sample size of 2,625 Red Kite breeding sites, high-resolution land-use data (10 m × 10 m) and climatic as well as topographic variables. The model revealed a strong relationship between land-use patterns and the Red Kite's distribution. Furthermore, a comparison of the predicted habitat suitability map with the actual distribution of Red Kites showed that not all suitable habitats were occupied by the species and thus, the species' distribution seems not to be in equilibrium with its environment. The differences between actual and predicted distribution may stem from present or former high mortality rates which are not compensated for by current reproduction rates. Additionally, low juvenile dispersal of Red Kites reduces recolonisation of unoccupied patches. © 2013 Dt. Ornithologen-Gesellschaft e.V.

Aue B.,Justus Liebig University | Diekotter T.,Justus Liebig University | Gottschalk T.K.,University of Applied Forest science | Wolters V.,Justus Liebig University | Hotes S.,University of Marburg
Agriculture, Ecosystems and Environment | Year: 2014

Within the European Union, national approaches of a 'High Nature Value (HNV) farmland' indicator have been developed to inform about the potential of agricultural landscapes to maintain biodiversity. We assessed how bird species abundance, richness and community composition, particularly of specialist species, were associated with the German HNV farmland indicator as an area-based aggregate and with its particular components which were semi-natural landscape elements and agricultural patches with characteristic plant species mapped in representative sample plots. The aggregated HNV indicator score showed a weak but positive relationship with generalist bird species only, while specialist species were associated with individual HNV farmland features characterizing wet grasslands and open farmland. Bird community analysis revealed three groups of HNV farmland features representative of particular landscape types: (1) complex landscapes with vertical woody structures such as hedgerows or small woodlands, (2) wet grasslands and (3) open agricultural land of low land-use intensity. Large portions of unexplained variance, however, indicated that the small-scaled HNV farmland features recorded without considering the landscape context may not have fully captured all important drivers of bird diversity in agricultural landscapes.To achieve a better representation of habitat requirements particularly of specialist bird species we propose surveying HNV farmland in a landscape context and calculating landscape-specific scores for highly structured, wetland-dominated and open landscapes of low land-use intensity. As compared to the aggregated indicator, the small-scale HNV farmland survey data would more efficiently enfold its potential for tailoring conservation schemes specifically to a given landscape type and its associated bird species. © 2014 Elsevier B.V.

Dobrowolska D.,Forest Research Institute | Hein S.,University of Applied Forest science | Oosterbaan A.,Wageningen University | Wagner S.,Sudan University of Science and Technology | And 2 more authors.
Forestry | Year: 2011

European ash (Fraxinus excelsior L.) is common throughout much of Europe and is a valuable broadleaved tree due to its ecological characteristics, outstanding wood properties and high economic value. It is a fast growing species, associated with several forest types and with a scattered distribution in many different forest communities. In this review, we sum up essential characteristics of European ash, relevant to the further development of silvicultural practices. The paper covers site requirements, regeneration and stand establishment, growth dynamics and wood quality, and health and robustness. The review also highlights implications for silviculture and summarizes new information on ash dieback, a phenomenon which is observed in many European countries. Ash grows best on fertile, pH-neutral, deep, freely drained soils and such sites should be favoured if the aim is for high quality timber. Ash grows well at wide spacing which can result in enlarged ring width and increased latewood percentage, making the wood denser and stronger. Relatively short rotations may be recommended, depending on site, to avoid black heart: for example, a harvesting diameter of 60 cm can be reached within 60-75 years at 60-80 ash crop trees per ha. Universal recommendations are therefore for wide spacing with heavy, regular thinning in order to get a large diameter within a relatively short rotation. The necessity for pruning depends on the stand density at establishment and the subsequent thinning regime. © Institute of Chartered Foresters, 2010. All rights reserved.

De Jaegere T.,University of Liège | Hein S.,University of Applied Forest science | Claessens H.,University of Liège
Forests | Year: 2016

Tilia cordata Mill. is a minor European broadleaved species with a wide but scattered distribution. Given its scarcity and low value in the wood market, it has received little attention from researchers and forest managers. This review summarizes the main aspects of T. cordata ecology and growth. Its main limiting factor is its need for warm summer temperatures to ensure successful seed production. It has a height growth pattern relatively similar to that of Acer pseudoplatanus L., with a slight delay in the early stages. Yield tables report great productivity, especially in eastern Europe. T. cordata used to be a major species in Europe, in contrast to its present distribution, but it is very likely to receive renewed interest in the future. Indeed, with the potential change of competition between species in some regions and the need for important diversification in others, T. cordata may play an important role in forest adaptation to climate change, especially owing to its wide ecological tolerance and its numerous ecosystem services. It is necessary to increase our knowledge about its regeneration and its responses to environmental and silvicultural factors, to establish clear management recommendations. © 2016 by the authors.

Kint V.,Catholic University of Leuven | Hein S.,University of Applied Forest science | Campioli M.,University of Antwerp | Muys B.,Catholic University of Leuven
Forest Ecology and Management | Year: 2010

The aim of this study was to develop statistical models for first order branchiness in young planted forest stands of pedunculate oak (Quercus robur L.) and European beech (Fagus sylvatica L.), and to give an ecological and silvicultural interpretation to these models. The reported models focus on the lower most-valuable stem part (i.e. until 6 m height), and cover different tree development classes to capture the development of branchiness over time. For each species 30 study plots were selected spread over two nearby forests in Flanders (northern Belgium), minimising site and genetic variability. Branches were counted on a total of 399 oak and 376 beech trees. On a subsample of 30 trees per species (one tree per plot), detailed non-destructive branch measurements were performed, yielding data for 555 oak and 438 beech branches. For both species, models for tree self-pruning (i.e. total branch number and dead branch portion), branch mortality and branch architecture (i.e. branch diameter and branch insertion angle) were built. A generalised linear mixed modelling approach was adopted. The models for total branch number and dead branch portion may be interpreted in terms of four processes contributing to self-pruning: (1) stand and tree development, (2) tree competitive status, (3) stand density and (4) site humidity. The reported models reveal similar self-pruning rates in oak and beech, but with different driving factors: early branch dying and slow shedding for oak and the other way around for beech. Mortality of individual branches is further determined by branch position and branch dimension. Branch diameter and branch insertion angle of both species are mainly related to branch cord length and relative branch position. All modelled effects are consistent with known ecological and ecophysiological processes. Silvicultural implications for stand establishment and early tree selection are discussed. The reported models can be used to fine-tune operational silvicultural choices for quality timber production. This is a first step towards the integration of branchiness models for oak and beech into forest growth simulators. © 2010 Elsevier B.V.

Gottschalk T.K.,University of Applied Forest science | Reiners T.E.,Senckenberg Institute
Annals of Forest Science | Year: 2015

Key message: We forecasted the effects of climate change and forest conversion options on common forest bird species by employing nation-wide high-resolution models. The results give details on how, where, and for which species forest conversion can mitigate climate change effects. Context: To mitigate effects of climate change on forests, alterations are required to convert forests into less vulnerable forest types. Coniferous forest that has been cultivated extensively outside its natural range has been identified as being more vulnerable to climate change effects than deciduous forest. Aims: The aim is to evaluate the effect of climate change mitigation measures on biodiversity due to forest conversion. Methods: We generated five forest scenarios for Germany in which we systematically replaced coniferous with deciduous forest types. We forecasted the effects of climate change and forest conversion options on 25 forest bird species by employing high-resolution models to predict their current and future ranges and population size. Results: Our simulations and modeling approach clearly predicted that climate change has a stronger impact on populations compared to distribution areas of common forest bird species. Forest conversion was predicted to amplify (15 species) and to weaken (10 species) the predicted gains and losses of species’ population size due to climate change. Using the total bird population size to evaluate the mitigation effect of the different forest scenarios, forest conversion below an elevation of 500 m a.s.l. was predicted to mitigate climate change effects by 0.3 million breeding pairs (−10 %). The relatively weak mitigation effect was mainly due to few generalist species that inhabit coniferous forests in large abundances and did not profit from a conversion to deciduous forests. Conclusion: The results of the study give details on how, where, and for which species forest conversion can mitigate the anticipated effects of climate change. © 2015, INRA and Springer-Verlag France.

Sauerbrei R.,Justus Liebig University | Ekschmitt K.,Justus Liebig University | Wolters V.,Justus Liebig University | Gottschalk T.K.,University of Applied Forest science
GCB Bioenergy | Year: 2014

Producing energy crops as an alternative to fossil fuels in order to reduce CO2 emissions will lead to large-scale changes in agricultural landscapes. Here, we quantify the potential impact of an increase in maize fields on the diversity of farmland birds by means of high resolution (25 × 25 m) land-use scenarios. We generated scenarios in which the area of maize production in Germany increases from presently 2.6 to 2.9, 3.6 and 4.3 million ha, corresponding to the energy crop production targets of the German Renewable Energy Act for the years 2020, 2035 and 2050. To test the mitigating potential of conservation measures, each scenario was generated in a standard version and a landscape protection version, with the latter excluding valuable farmland areas from being converted into maize fields. Nine species of farmland birds belonging to the governmental indicator scheme for sustainable land-use in Germany were modelled for the six nation-wide scenarios. The models predicted that only the Northern Lapwing and the Little Owl might profit from extended maize production. Despite this, the total number of breeding pairs of the indicator species was predicted to decline by about 0.4 million breeding pairs in the most intensive scenario. Protection of valuable farmland did not mitigate these negative effects in the models. Our findings suggest that increased production of energy crops conflicts with conservation of biological diversity. © 2013 John Wiley & Sons Ltd.

Scheuber M.,University of Applied Forest science
European Journal of Forest Research | Year: 2010

The k-nearest-neighbour (knn) method is known as a robust nonparametric method. It is used to estimate unknown values of data sets by means of similarity to reference data sets with known values. The spectral information of satellite remote sensing data can be used to provide the common characteristics in the knn estimation process. In forest sciences, the knn method is studied for its application potential. Some application examples are: (1) the estimation of parameters such as basal area, stem volume, number of trees per diameter class and tree species; (2) the estimation of forest debris and non-wood goods and services; (3) the production of wall-to-wall information for modelling, risk management and logistics. On the other hand, different limitations with respect to methodological characteristics as well as the selection of suitable parameters must be taken into consideration. The scope of this article concentrates on the discussion of the application potential and limits of the knn method in forestry with particular emphasis on management planning needs. The study is based on data taken from a forest inventory (FI) covering a test site near Rottenburg, in southwest Germany. Analysis results are compared with the traditional outcome of inventory data analysis and partly presented in thematic maps, which show identical spatial distribution patterns. For the map of six tree species, a map accuracy of 52.2% was found. The user's accuracy for the prevailing tree species was between 52.6% for Picea abies and 69.4% for Quercus sp. A timber volume map for Quercus sp. clearly visualises the bias at the extreme ends of the volume distribution. The root mean square error (RMSE) for the total timber volume estimate was 30.9% for k = 5 and could be reduced to 22.6% for k = 20. For Quercus sp., however, the respective RMSE values were between 106.5 and 84.8%. Significant differences between FI and knn estimates were mainly found for rare classes with minor representation in the reference data. © 2009 Springer-Verlag.

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