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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. Source

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. Source

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. Source

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. Source

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. Source

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