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Haring T.,BASF | Haring T.,TU Munich | Dietz E.,Bavarian State Institute of Forestry | Osenstetter S.,Bavarian State Institute of Forestry | And 3 more authors.
Geoderma | Year: 2012

Detailed knowledge on the spatial distribution of soils is crucial for environmental monitoring, management, and modeling. However soil maps with a finite number of discrete soil map units are often the only available information about soils. Depending on the map scale or the detailing of the map legend this information could be too imprecise. We present a method for the spatial disaggregation of map units, namely the refinement of complex soil map units in which two or more soil types are aggregated. Our aim is to draw new boundaries inside the map polygons to represent a single soil type and no longer a mixture of several soil types. The basic idea for our method is the functional relationship between soil types and topographic position as formulated in the concept of the catena. We use a comprehensive soil profile database and topographic attributes derived from a 10. m digital elevation model as input data for the classification of soil types with random forest models. We grouped all complex map units which have the same combination of soil types. Each group of map units is modeled separately. For prediction of the soil types we stratified the soil map into these groups and apply a specific random forest model only to the associated map units. In order to get reliable results we define a threshold for the predicted probabilities at 0.7 to assign a specific soil type. In areas where the probability is below 0.7 for every possible soil type we assign a new class "indifferent" because the model only makes unspecific classification there. Our results show a significant spatial refinement of the original soil polygons. Validation of our predictions was estimated on 1812 independent soil profiles which were collected subsequent to prediction in the field. Field validation gave an overall accuracy of 70%. Map units, in which shallow soils were grouped together with deep soils could be separated best. Also histosols could be predicted successful. Highest error rate were found in map units, in which Gleysoils were grouped together with deep soils or Anthrosols. To check for validity of our results we open the black box random forest model by calculating the variable importance for each predictor variable and plotting response surfaces. We found good confirmations of our hypotheses, that topography has a significant influence on the spatial arrangement of soil types and that these relationships can be used for disaggregation. © 2012 Elsevier B.V.

Schumacher J.,Institute for Plant Protection in Horticulture and Forests | Kehr R.,University of Science and Arts of Iran | Leonhard S.,Bavarian State Institute of Forestry
Forest Pathology | Year: 2010

Ash dieback is an emerging disease of Fraxinus excelsior in Germany. To date, economical damage is significant in nurseries, which also contribute towards spread of the disease, but damage to forests is increasing. The study presents the results of mycological and histological investigations on three hundred 3-year-old nursery ash saplings. The infection rate by the causative pathogen was determined for bark, outer and inner xylem, the pith and also separately for the above-ground portion and root system of the plants. The invasion and colonization strategy of the fungus in the woody stem was examined. In addition, the presence of soil-borne Oomycetes as possible primary or accompanying causal organisms was investigated. The results verify the dominant role of Chalara fraxinea as a causal agent of ash dieback and rule out the role of Oomycetes in the disease process. We conclude that C. fraxinea is not primarily endophytic in nature and spreads very effectively in the central stem tissues, which enables colonization of the woody stem in all three dimensions. Infections arising in the upper part of plants can thus spread extensively to lower parts. © 2009 Blackwell Verlag GmbH.

Mellert K.H.,AGWA | Fensterer V.,Ludwig Maximilians University of Munich | Kuchenhoff H.,Ludwig Maximilians University of Munich | Reger B.,Weihenstephan-Triesdorf University of Applied Sciences | And 3 more authors.
Journal of Vegetation Science | Year: 2011

Question: What are the main drivers for tree species distribution in the Bavarian Alps? What are the species-specific habitat requirements? Are predictions in accordance with expert knowledge? Location: Bavarian Alps (Southern Germany). Methods: To describe tree species-environment relationships, we established species distribution models for the 14 most common tree species of the region. We combined tree species occurrence data from forest inventories and a vegetation database with environmental data from a digital elevation model, climate maps and soil maps. For modelling, we used generalized additive models (GAM) combined with techniques to account for spatial autocorrelation and uneven coverage of environmental gradients. We developed parsimonious models to judge whether statistical models correspond to models based on expert knowledge. Results: Conceptual models were generally in accordance with expectations. Variables based on average temperatures were the most important predictors in most models. Proxies for soil properties such as water and nutrient availability were statistically significant and generally plausible, but appeared largely redundant for model performance. Altitudinal limits of tree species were generally well represented by models. Most species responded differently to summer and January temperatures, indicating that temperature variables are proxies not only for energy balance, but also for frost damage and drought. Although model building benefits considerably from collation with expert knowledge, there are limitations. Conclusions: Meaningful species distribution models can be obtained from noisy data sets covering only a small fraction of species ranges. Models calibrated with such data sets benefit from hypothesis-driven model building rather than strict data-driven model building. Hence, misleading explanations and predictions can be avoided and uncertainties identified. Nevertheless, projections based on climate scenarios can be substantially improved only with models calibrated on a wider data set. Ideally, environmental gradients should cover the whole niche space of a species, or at least include regions with analogous climate. © 2011 International Association for Vegetation Science.

Reger B.,Weihenstephan-Triesdorf University of Applied Sciences | Kolling C.,Bavarian State Institute of Forestry | Ewald J.,Weihenstephan-Triesdorf University of Applied Sciences
Journal of Vegetation Science | Year: 2011

Question: Which thermal climate model performs best in predicting the combined effects of temperature and radiation on forest vegetation in the Bavarian Alps? Location: Bavarian Alps, Germany. Methods: In order to find the best model for effective thermal climate for the Bavarian Alps, we analysed models using the following predictors derived from climate data and/or a digital elevation model: (a) temperature variables only, (b) temperature plus slope aspect and inclination, and (c) temperature plus potential global solar radiation. Models were tested by linear regression against four response variables based on average Ellenberg indicator values for temperature (cover weighted/unweighted, with/without bryophytes), which were computed for 2280 georeferenced relevés from the vegetation database BERGWALD. We optimized (b) by empirically searching for thermally most favourable slope aspect and inclination. Results: Closest model fit was achieved for unweighted temperature values based on vascular plants without bryophytes. Model fit (adj. R 2) increased from using temperature alone to temperature-radiation, to temperature-aspect-inclination as predictors. The best spatially explicit model for predicting temperature values (adj. R 2=0.57) was based on the variable combination mean temperature in the growing season (May to September), slope aspect (optimal aspect 195°) and inclination (optimal slope 30°). Conclusion: Combining mean temperatures and relief variables in GIS allows creation of predictive maps of mountain forest response to thermal climate. Applied to climate change scenarios, our model can forecast potential vegetation distribution in the future. The superiority of simple empirical relief factors over a widely used model of potential radiation casts doubt on the meaningfulness of the latter for vegetation studies. © 2011 International Association for Vegetation Science.

Fischer A.,TU Munich | Blaschke M.,Bavarian State Institute of Forestry | Bassler C.,Bavarian Forest National Park
Waldokologie Online | Year: 2011

Mountains, with their isolated position and altitudinal belts, are hotspots of biodiversity. Their flora and fauna have been observed worldwide since the days of Alexander von Humboldt, which has led to basic knowledge and understanding of species composition and the most important driving forces of ecosystem differentiation in such altitudinal gradients. Systematically designed analyses of changes in species composition with increasing elevation have been increasingly implemented since the 1990s. Since global climate change is one of the most important problems facing the world this century, a focus on such ecosystem studies is urgently needed. To identify the main future needs of such research we analyze the studies dealing with species changes of diverse taxonomical groups along altitudinal gradients (0 to 6,400 m a.s. l.) on all continents, published during the past one to two decades. From our study we can conclude that although mountains are powerful for climate change research most studies have to face the challenge of separating confounding effects driving species assemblages along altitudinal gradients. Our study therefore supports the view of the need of a global altitudinal concept including that (1) not only one or a few taxonomical groups should be analyzed, but rather different taxonomical groups covering all ecosystem functions simultaneously; (2) relevant site conditions should be registered to reveal direct environmental variables responsible for species distribution patterns and to resolve inconsistent effects along the altitudinal gradients; (3) transect design is appropriate for analyzing ecosystem changes in site gradients and over time; (4) both the study design and the individual methods should be standardized to compare the data collected worldwide; and (5) a long-term perspective is important to quantify the degree and direction of species changes and to validate species distribution models. (6) Finally we suggest to develop experimental altitudinal approaches to overcome the addressed problems of biodiversity surveys.

Klein D.,Bavarian State Institute of Forestry | Wolf C.,TU Munich | Schulz C.,Bavarian State Institute of Forestry | Weber-Blaschke G.,TU Munich
International Journal of Life Cycle Assessment | Year: 2015

Purpose: Life cycle assessment (LCA) techniques have been developed since the late 1960s in order to analyze environmental impacts of various products or companies. Although LCA techniques of forest production have been already conducted since the early 1990s, consistent and comprehensive LCA studies are still lacking for the forestry sector. In order to support better comparability between LCA studies, we analyzed the problems and differences by conducting a descriptive and quantitative analysis of existing LCA studies of forest production with special focus on Global Warming Potential (GWP). Methods: We analyzed 22 different peer-reviewed studies, four original reports and two databases. Important issues were, among others, the goal of the studies, system boundaries, functional units, impact categories and involved processes. In addition, a quantitative analysis was purchased where the results of the GWP of the reviewed studies were analyzed. Results and discussion: The studies showed large differences between methodical assumptions and their subsequent results. For the GWP, we found a range of 2.4–59.6 kg CO2-equiv.*m−3 over bark (ob; median = 11.8; n = 41) from site preparation to forest road and 6.3–67.1 kg CO2-equiv.*m−3 ob (median = 17.0; n = 36) from site preparation to plant gate or consumer. Results varied as a function of the included processes and decisive assumptions, e.g., regarding productivity rates or fuel consumption of machineries. Raw wood products are widely declared as “carbon neutral,” but the above-mentioned results show that absolute carbon neutrality is incorrect, although the GWP is low compared with the carbon storage of the raw wood product (range of C-emitted/C-stored in wood is 0.008–0.09 from forest to plant gate or consumer). Thereby, raw wood products can be described as “low emission raw materials” if long-term in situ carbon losses by changed forest management or negative direct or indirect land use change effects (LUC, iLUC) can be excluded. Conclusions: In order to realize improved comparisons between LCA studies in the forestry sector in the future, we propose some methodical approaches regarding the harmonization of system boundaries, functional units, considered processes, and allocation assumptions. These proposals could help to specify the description of the forest production outlined in existing Product Category Rules for Environmental Product Declarations (e.g., EN ISO 16485 2014 or EN ISO 15804 2012) following EN ISO 14025 (2011) and for carbon footprinting standards like the Publicly Available Specification (PAS) 2050 (2011) or the European Environmental Footprinting Initiative. © 2015, Springer-Verlag Berlin Heidelberg.

Pretzsch H.,TU Munich | Biber P.,TU Munich | Schutze G.,TU Munich | Uhl E.,TU Munich | And 2 more authors.
Nature Communications | Year: 2014

Forest ecosystems have been exposed to climate change for more than 100 years, whereas the consequences on forest growth remain elusive. Based on the oldest existing experimental forest plots in Central Europe, we show that, currently, the dominant tree species Norway spruce and European beech exhibit significantly faster tree growth (+32 to 77%), stand volume growth (+10 to 30%) and standing stock accumulation (+6 to 7%) than in 1960. Stands still follow similar general allometric rules, but proceed more rapidly through usual trajectories. As forest stands develop faster, tree numbers are currently 17-20% lower than in past same-aged stands. Self-thinning lines remain constant, while growth rates increase indicating the stock of resources have not changed, while growth velocity and turnover have altered. Statistical analyses of the experimental plots, and application of an ecophysiological model, suggest that mainly the rise in temperature and extended growing seasons contribute to increased growth acceleration, particularly on fertile sites. ©2014 Macmillan Publishers Limited. All rights reserved.

Prietzel J.,TU Munich | Zimmermann L.,Bavarian State Institute of Forestry | Schubert A.,Bavarian State Institute of Forestry | Christophel D.,TU Munich
Nature Geoscience | Year: 2016

Climate warming is expected to induce soil organic carbon losses in mountain soils that result, in turn, in reduced soil fertility, reduced water storage capacity and positive feedback on climate change. Here we combine two independent sets of measurements of soil organic carbon from forest soils in the German Alps-repeated measurements from 1976 to 2010 and from 1987 to 2011-to show that warming has caused a 14% decline in topsoil organic carbon stocks. The decreases in soil carbon occurred over a period of significant increases in six-month summer temperatures, with the most substantial decreases occurring at sites with large changes in mean annual temperature. Organic carbon stock decreases were largest-on average 32%-in forest soils with initial topsoil organic carbon stocks greater than 8 kg Cm-2, which can be found predominantly on calcareous bedrock. However, organic carbon stocks of forest soils with lower initial carbon stocks, as well as soils under pasture or at elevations above 1,150 m, have not changed significantly. We conclude that warming is the most likely reason for the observed losses of soil organic carbon, but that site, land use and elevation may ameliorate the effects of climate change. © 2016 Macmillan Publishers Limited.

Klein D.,Bavarian State Institute of Forestry | Hollerl S.,TU Munich | Blaschke M.,Bavarian State Institute of Forestry | Schulz C.,Bavarian State Institute of Forestry
Forests | Year: 2013

Forestry-based carbon sequestration projects demand a comprehensive quantification of the different climate change mitigation effects. In our study, we modeled a life cycle of managed pure stands consisting of the four main tree species in Bavaria (spruce, pine, beech and oak). For spruce and beech, an unmanaged stand was additionally integrated in order to analyze the differences in climate change mitigation effects compared to the managed stands. We developed a climate change mitigation model, where stand development and silvicultural treatments including harvested timber volumes were conducted using the tree growth model Silva 2.3. The harvested wood products (HWP), including their substitution effects were calculated with a subsequent model. For unmanaged beech forests, we compiled measured data from the literature, and Bavarian strict forest reserves for validating our model results. The results for the managed stands reveal that spruce provides the highest total climate change mitigation effects. After a simulation period of 180 years, one hectare leads to a mean mitigation benefit of 13.5 Mg CO2 ha-1 year-1. In comparison, results for pine, beech and oak reveal lesser benefits with 10.1 Mg CO2 ha-1 year-1, 9.1 Mg CO2 ha-1 year-1 and 7.2 Mg CO2 ha-1 year-1, respectively. However, these results assume current growing conditions. Considering climate change, it is very likely that spruce will not be suitable in several regions of Bavaria in the future. Furthermore, excessive disturbances could affect spruce more drastically than the other tree species. In that case, the order could change and beech could exceed spruce. Thus the results cannot be seen as a general recommendation to establish spruce stands in order to achieve optimal climate change mitigation benefits. Nevertheless, results for spruce illustrate that high increment and especially wood use in long-lived products is crucial for high climate change mitigation effects. Mitigation effects in unmanaged spruce and beech stands do not differ in the first decades from their managed counterparts, but are below them in the long term with a total climate change mitigation benefit of 8.0 Mg CO2 ha-1 year-1 and 7.2 Mg CO2 ha-1 year-1, respectively. These differences are mainly caused by the missing substitution effects in the unmanaged stands. However, the precise dimensions of substitution effects still remain uncertain and the lack of data should be reduced via additional life cycle assessments for more products and product classes. However, neglecting substitution effects in climate change mitigation models leads to severe underestimations of the mitigation effects in managed forests. © 2013 by the authors.

Wolf C.,TU Munich | Klein D.,Bavarian State Institute of Forestry | Weber-Blaschke G.,TU Munich | Richter K.,TU Munich
Journal of Industrial Ecology | Year: 2015

Environmental impacts of the provision of wood energy have been analyzed through life cycle assessment (LCA) techniques for many years. Systems for the generation of heat, power, and combined heat and power (CHP) differ, and methodological choices for LCA can vary greatly, leading to inconsistent findings. We analyzed factors that promote these findings by conducting a systematic review and meta-analysis of existing LCA studies for wood energy services. The systematic review investigated crucial methodological and systemic factors, such as system boundaries, allocation, transportation, and technologies, for transformation and conversion of North American and European LCA studies. Meta-Analysis was performed on published results in the impact category global warming (GW). A total of 30 studies with 97 systems were incorporated. The studies exhibit great differences in their systemic and methodological choices, as well as their functional units, technologies, and resulting outcomes. A total of 44 systems for the generation of power, with a median impact on GW of 0.169 kilograms (kg) of carbon dioxide equivalents (CO2-eq) per kilowatt-hour (kWhel), were identified. Results for the biomass fraction only show a median impact on GW of 0.098 kg CO2-eq * kWhel-1. A total of 31 systems producing heat exhibited a median impact on GW of 0.040 kg CO2-eq * kWhth-1. With a median impact on GW of 0.066 kg CO2-eq * kWhel+th-1, CHP systems show the greatest variability among all analyzed wood energy services. To facilitate comparisons, we propose a methodological approach for the description of system boundaries, the basis for calculations, and reporting of findings. © 2015 by Yale University.

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