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Thiele J.C.,University of Gottingen | Nuske R.S.,Northwest German Forest Research Station

Climate change has altered and further will change the environmental conditions for many sectors. Whereas annual cropping systems can be adapted yearly, decisions in forest management usually have long-lasting effects. Depending on the region and tree species rotation periods range between 80 and 180 years in Central Europe. Therefore, todays tree species selection should also take into account the impacts of climate change in the future. Although many attempts have been made to understand single aspects of climate change impacts on forests, the available knowledge has to be conflated into an integrated assessment to support decision making. A comprehensive system comprising different impact models and an economic assessment suitable for Central European forests and driven by high-resolution temporal- and spatial data is currently missing. We present a conceptional design and a reference implementation of a Decision Support System (DSS) tailored to assess climate change impacts on German forests. To provide high ease-of-use, the system was implemented as a web application and offers information for single stands on-demand as well as interactive maps and preprocessed assessments on a coarser level for entire Germany. To create such a complex, integrated system from legacy models written in different programming languages the interfaces had to be developed carefully. The key of this DSS is its building blocks: established models describing different climate change impacts. Since the DSS is a very modular system, it is easy to replace submodels and to adapt it to other study areas, forest systems or research questions if suitable parameterized models and input data are available. The presented technical solution is adaptable to other systems integrating existing models and the source code is available. © DLV GmbH. Source

Petritan A.M.,Forest Research and Management Institute ICAS | Nuske R.S.,Northwest German Forest Research Station | Petritan I.C.,Forest Research and Management Institute ICAS | Petritan I.C.,Transilvania University of Brasov | Tudose N.C.,Forest Research and Management Institute ICAS
Forest Ecology and Management

In recent decades, natural forest remnants have become increasingly important as reference objects for maintaining or restoring old-growth characteristics in managed forests. Canopy gaps play an important role in forest regeneration, particularly for the establishment and development of tree species with different ecological recruitment patterns. Yet quantitative descriptions of such patterns are still scarce, particularly for oak-dominated forests. The old-growth sessile oak-European beech forest remnant in the Runcu-Grosi Natural Reserve provided a unique opportunity to study natural disturbance regimes with minimal human influence in an ecosystem type rarely investigated. The study site comprised the best preserved part of the Reserve. Its 32.3 ha are dominated by sessile oak. A complete gap survey was carried out. The size, shape, spatial pattern and traits of the gapmakers of all 321 gaps were recorded. Additionally, the gap age as well as the structure and composition of gapfillers were investigated in 70 randomly sampled expanded gaps.The canopy gaps and the expanded gaps covered 12.8% and 28.5% of the study site, respectively. The frequency distribution of the canopy gap sizes corresponded to the negative exponential distribution, with most of the gaps (60%) smaller than 100 m2, 34% between 100 and 300 m2 and only 2% larger than 500 m2. Canopy gaps smaller than 300 m2 were responsible for 71% of the total gap area, suggesting a dominance of small and intermediate gaps in this forest. The pattern of the canopy gaps is characterized by a pronounced soft-core effect, and in one part of the study area a tendency towards regularity. Most of the gaps (84%) were caused by more than one gapmaker and seemed to be created in more than one disturbance event since, in 72% of the gaps, gapmakers of at least two different decay classes were found. The disturbance regime was driven by the mortality of sessile oaks, the main gapmaker species, caused mostly by uprooting. The other main canopy tree species was European beech, which died often by snapping. It was less common as gapmaker (20%), but was the main gapfiller (91%). In contrast sessile oak was almost absent among the gapfillers.These results suggest that the current small-scale disturbance pattern dominating this old-growth forest is more suitable for shade-tolerant species such as European beech, accentuating the already steady decline of oaks in mixed sessile oak-European beech stands. © 2013 Elsevier B.V. Source

Bonten L.T.C.,Wageningen University | Groenenberg J.E.,Wageningen University | Meesenburg H.,Northwest German Forest Research Station | De Vries W.,Wageningen University
Environmental Pollution

Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well. © 2010 Published by Elsevier Ltd. Source

Legner N.,University of Gottingen | Fleck S.,University of Gottingen | Fleck S.,Northwest German Forest Research Station | Leuschner C.,University of Gottingen
Trees - Structure and Function

Key message: The relative shade tolerance of T. cordata, F. sylvatica, and C. betulus in mature stands is based on different species-specific carbon and nitrogen allocation patterns. The leaf morphology and photosynthetic capacity of trees are remarkably plastic in response to intra-canopy light gradients. While most studies examined seedlings, it is not well understood how plasticity differs in mature trees among species with contrasting shade tolerance. We studied light-saturated net photosynthesis (A max), maximum carboxylation rate (V cmax), electron transport capacity (J max) and leaf dark respiration (R d) along natural light gradients in the canopies of 26 adult trees of five broad-leaved tree species in a mixed temperate old-growth forest (Fraxinus excelsior, Acer pseudoplatanus, Carpinus betulus, Tilia cordata and Fagus sylvatica), representing a sequence from moderately light-demanding to highly shade-tolerant species. We searched for species differences in the dependence of photosynthetic capacity on relative irradiance (RI), specific leaf area (SLA) and nitrogen per leaf area (Na). The three shade-tolerant species (C. betulus, T. cordata, F. sylvatica) differed from the two more light-demanding species by the formation of shade leaves with particularly high SLA but relatively low Na and consequently lower area-based A max, and a generally higher leaf morphological and functional plasticity across the canopy. Sun leaf morphology and physiology were more similar among the two groups. The three shade-tolerant species differed in their shade acclimation strategies which are primarily determined by the species' plasticity in SLA. Under low light, T. cordata and F. sylvatica increased SLA, mass-based foliar N and leaf size, while C. betulus increased solely SLA exhibiting only low intra-crown plasticity in leaf morphology and N allocation patterns. This study with mature trees adds to our understanding of tree species differences in shade acclimation strategies under the natural conditions of a mixed old-growth forest. © 2013 Springer-Verlag Berlin Heidelberg. Source

Molder I.,Northwest German Forest Research Station | Molder I.,University of Gottingen | Leuschner C.,University of Gottingen | Leuschner H.H.,University of Gottingen
Trees - Structure and Function

We conducted dendroecological analyses in 80-year-long tree ring chronologies to detect neighborhood effects (competition intensity, species identity) on the δ13C signature of tree rings and radial stem increment of Fagus sylvatica trees growing either in monospecific or mixed patches of a temperate forest. We hypothesized that tree ring δ13C is a more sensitive indicator of neighborhood effects and the impact of climate variability on growth than is ring width. We found a closer correlation of summer precipitation to δ13C than to ring width. While the ring width showed a decline over the test period (1926-2005), the mean curve of δ13C increased until the mid of the 1970s, remained high until about 1990, and markedly decreased thereafter. Possible explanations related to ontogeny and environmental change ('age effect' due to canopy closure; elevated atmospheric SO2 concentrations in the 1960s-1980s) are discussed. Beech target trees surrounded by many allospecific trees had a significantly lower mean δ13C in the period 1926-1975 than beech with predominantly or exclusively conspecific neighborhood, possibly indicating a more favorable water supply of beech in diverse stands. Contrary to expectation, trees subject to more intense competition by neighboring trees (measured by Hegyi's competition index) had lower δ13C values in their tree rings, which is thought to reflect denser canopies being linked to increased shading. We conclude that tree ring δ13C time series represent combined archives of climate variability, stand history and neighborhood effects on tree physiology and growth that may add valuable information to that obtained from conventional tree ring analysis. © 2010 The Author(s). Source

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