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Kaiser K.,German Research Center for Geosciences | Heinrich I.,German Research Center for Geosciences | Heine I.,German Research Center for Geosciences | Natkhin M.,Thunen Institute of Forest Ecosystems | And 8 more authors.
Journal of Hydrology | Year: 2015

In the glacially formed landscape of north-eastern Germany pronounced hydrological changes have been detected in recent decades, leading to the general question how lake levels and related groundwater levels perform in a long-term perspective, i.e. during the last c. 100. years. But long-term lake-level records are rare; most observations do not start before the late 20th century. Therefore, the potential of historic hydrological data, comprising drowned trees (as a geo-/bioarchive) and aerial as well as map imagery (as a document archive) was tested in order to derive discrete-time lake-level stands. These data are contrasted with lake-level simulations, obtaining a continuous-time series.Two small glacial lakes without connection to the stream network (i.e. closed lakes) were investigated in the Schorfheide area, c. 70. km north of Berlin. Both are dominantly fed by groundwater and precipitation but differ in their hydrogeological and catchment characteristics. For one lake a c. 40. year-long gauging record is available, showing high lake levels in the 1980s followed by a lowering of c. 3. m till the mid-2000s. In both lakes submerged in situ tree remains were discovered and dated by dendrochronology, revealing low lake levels during the first half of the 20th century. One lake was almost completely dry until c. 1960. Aerial photos provided data on lake levels since the 1930s which are corroborated by evidence of topographic mapping. Combining the empiric data with retrograde lake-level modelling, a well-proven lake-level record can be established for one lake that covers the last c. 90. years. The same general lake-level dynamics could be reconstructed by means of proxy data for the other lake. In both cases climate has been the dominant driver of lake-level dynamics. Comparisons with other multi-decadal lake-level records from the region show that these differ, depending on the hydrological lake type which modifies water feeding and water level. The results clearly showed that lake levels exhibited substantial long-term changes that should be taken into account in future hydroclimatic and hydrological studies. © 2015 Elsevier B.V. Source


Baum S.,Thunen Institute of Rural Studies | Weih M.,Swedish University of Agricultural Sciences | Bolte A.,Thunen Institute of Forest Ecosystems
Landbauforschung Volkenrode | Year: 2013

In the near future an increase in Short Rotation Coppice (SRC) plantations is to be expected. The objective was to compare the recent vegetation and the soil seed bank in SRC plantations to reveal the functioning of the soil seed bank for phytodiversity and vegetation structure after reconversion of SRC plantations into arable land. For the analyses, above-ground vegetation surveys and soil seed bank samples of six German and four Swedish SRC plantations were used. Similarity in composition of soil seed banks and recent vegetation was low in terms of species, plant strategy types, species habitat preferences and seed longevity. On average, the proportion of common species of recent vegetation and soil seed bank was 8.4 % (± 6.7 % SD).The recent vegetation was dominated by competitive (c) plant species while in the soil seed banks highest proportions were detected for ruderals (r) and competitors (c). Species with long-term persistent seeds had the highest contribution to both the recent vegetation and the soil seed banks. Grassland species had highest species habitat preference proportion in the recent vegetation. The soil seed banks contained predominantly ruderal species and woodland species were almost absent. Due to the poor coherence of seed bank vs. recent vegetation, we conclude that the site history has only a minor influence on phytodiversity in SRC plantations, suggesting that recent vegetation composition is mainly due to the species pool of the adjacent vegetation and site conditions like below-canopy irradiance and site nutrition. Source


Winter S.,Eberswalde University Of Applied Sciences | Hofler J.,TU Munich | Michel A.K.,Eberswalde University Of Applied Sciences | Michel A.K.,Thunen Institute of Forest Ecosystems | And 2 more authors.
European Journal of Forest Research | Year: 2015

Process-orientated, unmanaged forest remnants are not sufficient for halting the loss of forest biodiversity. Thus, integrated biodiversity-promoting management for forest inhabitants is needed. Microhabitats, such as tree cavities or bark pockets, are essential for the preservation of saproxylic species and of critical importance for endangered ones. This study investigates (1) which factors trigger the formation of microhabitats at both the individual tree and aggregated plot level, and (2) whether the co-occurrence of microhabitats differs between managed (=logged) and unmanaged forests. Relationships between the occurrence of 17 microhabitat types and individual tree features (e.g. light availability, and tree vitality) and plot characteristics (e.g. stand density index and stand age) in 398 plots dominated by Fagus sylvatica or Pseudotsuga menziesii in Germany and the USA were studied using random-effects logistic and normal regression modelling. Separate analyses were performed for German beech forests, German Douglas-fir forests, and the US Douglas-fir forests. Our results show that (1) tree diameter in breast height (DBH), tree vitality and branchiness or epicormic branches are highly related with the occurrence of one or more microhabitats on individual trees in managed and unmanaged beech and US Douglas-fir forests. In managed German Douglas-fir forests, vitality is not a predictor for the occurrence of microhabitats on a tree, but tree density and the maximum age of trees in a stand in addition to DBH and branchiness have an effect. Time since last management is not a statistically significant predictor for the presence of microhabitats at the tree level, but it is for German beech at the plot level. In Douglas-fir-dominated forests both in Germany and in the USA, the stand density index was the only common predictor at the plot level. (2) Unmanaged German beech and Douglas-fir forests exhibit more statistically significant and positive correlations with microhabitat groups than managed stands, implying that the presence of one microhabitat group on a tree is associated with the presence of other microhabitat groups. We finally conclude that measures for supporting microhabitat inhabitants in managed forests are scale and species dependent (tree versus plot level; beech versus Douglas-fir-dominated forests). Trees that carry microhabitats seem to have similar features independently of forest management. At the plot level, density management may trigger the accumulation of microhabitats. Our results indicate that in forest management, it is possible to consider the factors influencing the formation of microhabitats and implement adequate forest practices to advance their formation. © 2014, Springer-Verlag Berlin Heidelberg. Source


Siegmund J.F.,Potsdam Institute for Climate Impact Research | Siegmund J.F.,University of Potsdam | Sanders T.G.M.,Thunen Institute of Forest Ecosystems | Heinrich I.,Helmholtz Center Potsdam | And 4 more authors.
Frontiers in Plant Science | Year: 2016

Observed recent and expected future increases in frequency and intensity of climatic extremes in central Europe may pose critical challenges for domestic tree species. Continuous dendrometer recordings provide a valuable source of information on tree stem radius variations, offering the possibility to study a tree’s response to environmental influences at a high temporal resolution. In this study, we analyze stem radius variations (SRV) of three domestic tree species (beech, oak, and pine) from 2012 to 2014. We use the novel statistical approach of event coincidence analysis (ECA) to investigate the simultaneous occurrence of extreme daily weather conditions and extreme SRVs, where extremes are defined with respect to the common values at a given phase of the annual growth period. Besides defining extreme events based on individual meteorological variables, we additionally introduce conditional and joint ECA as new multivariate extensions of the original methodology and apply them for testing 105 different combinations of variables regarding their impact on SRV extremes. Our results reveal a strong susceptibility of all three species to the extremes of several meteorological variables. Yet, the inter-species differences regarding their response to the meteorological extremes are comparatively low. The obtained results provide a thorough extension of previous correlation-based studies by emphasizing on the timings of climatic extremes only. We suggest that the employed methodological approach should be further promoted in forest research regarding the investigation of tree responses to changing environmental conditions. © 2016 Siegmund, Sanders, Heinrich, van der Maaten, Simard, Helle and Donner. Source


Sanders T.G.M.,Thunen Institute of Forest Ecosystems | Sanders T.G.M.,University of Greifswald | Pitman R.,Japan Forestry and Forest Products Research Institute | Broadmeadow M.S.J.,Japan Forestry and Forest Products Research Institute
IForest | Year: 2014

Oak forests play a major role in Britain due to their economic, social and historic value. Sudden oak death and general decline symptoms have therefore caused major concerns in the forestry sector over the past decade. Several strategies have been proposed to preserve the economic and social value of oak forests, including the planting of native species with more southerly origins, or non-native species of oak that may be better suited to the projected climate of the future. The Ovington research plots, established 50 years ago at the Bedgebury Pinetum in southeast England, provided the opportunity to compare annual growth rates and climate-growth relationships of five oak species growing adjacent to each other on the same soil type and under the same climatic conditions. Clear differences were evident in annual increment and climate- growth responses for the five Quercus species. Growth rates were significantly lower (p<0.05) for the two species native to the UK (Q. petraea and Q. robur) compared to the southern European and American species. A partitioning analysis using key climatic variables separates Q. coccinea from the other species due to its negative response to low temperatures. These results were confirmed by pointer year analysis. The analysis suggests that Q. robur is likely to be the more resilient of the two native species of oak to the future climate of southern Britain. Of the non-native species of oak evaluated, Q. coccinea represents an alternative species to Q. robur and Q. petraea on very dry, nutrient-poor sites. Q. palustris may also have some potential under current conditions for species diversification, but its requirement for higher summer precipitation than the other four species suggests that this potential may not be sustained as climate change progresses. However, if alternative species are selected as more resilient to climate change in terms of growth, it will be essential to consider a range of other issues including impacts on biodiversity, resilience to endemic tree pests and diseases, form and appearance, landscape and timber quality. © SISEF. Source

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