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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.

Giordani P.,University of Genoa | Stofer S.,Swiss Federal Institute of forest | Seidling W.,Thunen Institute of Forest Ecosystems | Granke O.,Institute For Digitale Systemanalyse And Landschaftsdiagnose | Fischer R.,Thunen Institute for World Forestry
Forest Ecology and Management | Year: 2014

Lichens are considered to be among the most sensitive organisms for several types of pollutants. In this work, we analyzed a dataset of 286 epiphytic lichen species observed on 1155 trees at 83 ForestBIOTA plots, which is a subsample of approx. 500 plots of the European ICP Forests Level II network. We aimed at examining the amount of nitrogen deposition for which a significant variation of the relative diversity of morpho-functional groups of epiphytic lichens in the sampled plots is expected. Moreover, the study aimed at determining how much variance of these diversity variables could be explained by nitrogen depositions only. We used correlation and multiple regression models as well as hierarchical partitioning to evaluate the relative importance of environmental predictors in explaining variation in lichen diversity descriptors. The analysis splits the variation explained by each variable into a joint effect together with the other explanatory variables, and into an independent effect not shared with any other variable. The percentage of macrolichens in the plots was shown to be the most important indicator, since 56.7% of its variation could be explained by deposition, particularly by nitrogen compounds. It was shown that approx. 75% of the ForestBIOTA plots are affected by an unsustainably high throughfall nitrogen deposition. Based on these outcomes, it was possible to determine a nitrogen critical load of 2.4kgha-1yr-1. © 2013 Elsevier B.V.

PubMed | Forstliche Versuchs und Forschungsanstalt Baden Wurttemberg and Thunen Institute of Forest Ecosystems
Type: Journal Article | Journal: Carbon balance and management | Year: 2016

The German greenhouse gas inventory in the land use change sector strongly depends on national forest inventory data. As these data were collected periodically 1987, 2002, 2008 and 2012, the time series on emissions show several jumps due to biomass stock change, especially between 2001 and 2002 and between 2007 and 2008 while within the periods the emissions seem to be constant due to the application of periodical average emission factors. This does not reflect inter-annual variability in the time series, which would be assumed as the drivers for the carbon stock changes fluctuate between the years. Therefore additional data, which is available on annual basis, should be introduced into the calculations of the emissions inventories in order to get more plausible time series.This article explores the possibility of introducing an annual rather than periodical approach to calculating emission factors with the given data and thus smoothing the trajectory of time series for emissions from forest biomass. Two approaches are introduced to estimate annual changes derived from periodic data: the so-called logging factor method and the growth factor method. The logging factor method incorporates annual logging data to project annual values from periodic values. This is less complex to implement than the growth factor method, which additionally adds growth data into the calculations.Calculation of the input variables is based on sound statistical methodologies and periodically collected data that cannot be altered. Thus a discontinuous trajectory of the emissions over time remains, even after the adjustments. It is intended to adopt this approach in the German greenhouse gas reporting in order to meet the request for annually adjusted values.

Seidling W.,Thunen Institute of Forest Ecosystems | Travaglini D.,University of Florence | Meyer P.,Northwest German Forestry Research Station | Waldner P.,Swiss Federal Institute of forest | And 4 more authors.
IForest | Year: 2014

Dead wood and stand structural parameters were sampled in eleven countries using standardized methods at about 90 intensive forest monitoring sites across large parts of Europe. Besides descriptions and correlation analyses of dead wood and stand structure parameters, a joint evaluation of both fields was performed by principal component analysis (PCA). The extracted principal components were subsequently regressed against important numerical and categorical site-related parameters like soil pH, altitude, or forest type. Dead wood volumes varied largely across plots, however, 77 percent of them had volumes below 25 cubic meter per hectare. While all fractions of dead wood - except cut stumps - reveal high intercorrelation, different aspects of stand structure varied more independently. Clark-Evans index, number of tree species and standard deviation of tree trunk diameters revealed as most selfcontained. The 1st PCA axis covered 46 percent of the total variance and was mostly loaded by total dead wood volume denoting it as the feature differentiating forests most. The 2nd axis was primarily loaded by tree species diversity together with stem density and the Clark-Evans index. On the 3rd axis diameter differentiation of trees together with the volume of cut stumps prevailed, while the 4th was mainly related to the decay class of woody debris. Bivariate ex post analyses revealed country as a significant predictor of all PCA axes, underlining national forest legislations and management rules as crucial for all investigated structural features of forests. Forest type was related only to the 3rd and 2nd axis. Only the 3rd axis revealed significant relationships with some ecological site factors (age, number of tree layers, latitude, altitude). The outcome underlines the significance of nationally enacted forest legislations for both important structural and biodiversity-relevant features of forest ecosystems and encourages similar approaches with data from national forest inventories or monitoring systems. © iForest - Biogeosciences and Forestry.

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.

Spathelf P.,Eberswalde University for Sustainable Development | Bolte A.,Thunen Institute of Forest Ecosystems | Van Der Maaten E.,University of Greifswald
Landbauforschung Volkenrode | Year: 2015

Climate change projections for Europe suggest increases in temperature, changes in precipitation regimes as well as more frequent and severe weather extremes like heat waves, droughts and storms. As these changes may have a large impact on forest ecosystems, forest management should adapt to maintain vital and productive forests in the future. This review assesses how close-to-nature silviculture (CNS), which is a widespread silvicultural approach in Central Europe, may cope with projected changes in climate. First, a conceptual model of forest vulnerability is outlined, and used to describe climate change exposure, sensitivity and adaptive capacity of forests. Strategies and options for adaptation, and their compliance with the principles of CNS are then discussed. Modifications in CNS, such as using exotic tree species and provenances or the assisted migration of well adapted tree species from other climates can enhance adaptive capacity of forests. Moreover, the regeneration of stress-tolerant pioneer species can be supported by applying the whole range of silvicultural systems.

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 | Broadmeadow M.S.J.,Forestry Commission England
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.

Bolte A.,Thunen Institute of Forest Ecosystems | Bolte A.,University of Gottingen | Kampf F.,University of Gottingen | Hilbrig L.,Thunen Institute of Forest Ecosystems
Frontiers in Plant Science | Year: 2013

Scientists are currently debating the effects of mixing tree species for the complementary resource acquisition in forest ecosystems. In four unmanaged old-growth spruce-beech forests in strict nature reserves in southern Sweden and northern Germany we assessed forest structure and fine rooting profiles and traits (≤2 mm) by fine root sampling and the analysis of fine root morphology and biomass. These studies were conducted in selected tree groups with four different interspecific competition perspectives: (1) spruce as a central tree, (2) spruce as competitor, (3) beech as a central tree, and (4) beech as competitor. Mean values of life fine root attributes like biomass (FRB), length (FRL), and root area index (RAI) were significantly lower for spruce than for beech in mixed stands. Vertical profiles of fine root attributes adjusted to one unit of basal area (BA) exhibited partial root system stratification when central beech is growing with spruce competitors. In this constellation, beech was able to raise its specific root length (SRL) and therefore soil exploration efficiency in the subsoil, while increasing root biomass partitioning into deeper soil layers. According to relative values of fine root attributes (rFRA), asymmetric below-ground competition was observed favoring beech over spruce, in particular when central beech trees are admixed with spruce competitors. We conclude that beech fine rooting is facilitated in the presence of spruce by lowering competitive pressure compared to intraspecific competition whereas the competitive pressure for spruce is increased by beech admixture. Our findings underline the need of spatially differentiated approaches to assess interspecific competition below ground. Single-tree approaches and simulations of below-ground competition are required to focus rather on microsites populated by tree specimens as the basic spatial study area. © 2013 Bolte, Kampf and Hilbrig.

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.

Eickenscheidt N.,Thunen Institute of Forest Ecosystems | Wellbrock N.,Thunen Institute of Forest Ecosystems
Environmental Monitoring and Assessment | Year: 2014

The consistency of visual assessment of tree defoliation, which represents the most widely used indicator for tree condition, has frequently been in the focus of scientific criticism. Thus, the objective of the present study was to examine the consistency of the defoliation data from the annual national training courses for the forest condition survey in Germany from 1992 to 2012. Defoliation assessments were carried out in stands of beech (Fagus sylvatica), oak (Quercus robur and Quercus petraea), Norway spruce (Picea abies), and pine (Pinus sylvestris). Among the observer teams, the absolute deviation from the observer mean of all years was ±4.4 % defoliation and the standard deviation of defoliation was ±5.5 %. On average, 94 % of the assessments were located within the ±10 % interval of deviation from the mean. Tree species-specific differences did not occur when all years were considered. A trend towards increasing consistency was observed from 1992 to 2012, in particular for oak and spruce. The deviation of defoliation assessments depended non-linearly on the level of defoliation with highest deviations at intermediate defoliations. In spite of high correlations and agreements among observers, systematic errors were determined in nearly every year. However, within-observer variances were higher than between-observer variances. The present study applied a three-way evaluation approach for the assessment of consistency and demonstrated that the visual defoliation assessment at the national training courses in general produced consistent data within Germany from 1992 to 2012. © 2013 The Author(s).

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