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  • 1
    Language: English
    In: Environmental monitoring and assessment, 2011, Vol.174(1), pp.65-89
    Description: This study evaluates the acidification status and trends in streams of forested mountain ranges in Germany in consequence of reduced anthropogenic deposition since the mid 1980s. The analysis is based on water quality data for 86 long-term monitored streams in the Ore Mountains, the Bavarian Forest, the Fichtelgebirge, the Harz Mountains, the Spessart, the Black Forest, the Thuringian Forest, and the Rheinisches Schiefergebirge of Germany and the Vosges of France. Within the observation period, which starts for the individual streams between 1980 and 2001 and ends between 1990 and 2009, trends in chemical water quality were calculated with the Seasonal Mann Kendall Test. About 87% of the streams show significant (p 〈 0.05) negative trends in sulfate. The general reduction in acid deposition resulted in increased pH values (significant for 66% of the streams) and subsequently decreased base cation concentrations in the stream water (for calcium significant in 58% and magnesium 49% of the streams). Reaction products of acidification such as aluminum (significant for 50%) or manganese (significant for 69%) also decreased. Nitrate (52% with significant decrease) and chloride (38% with significant increase) have less pronounced trends and more variable spatial patterns. For the quotient of acidification, which is the ratio of the sum of base cations and the sum of acid anions, no clear trend is observed: in 44% of the monitored streams values significantly decreased and in 23% values significantly increased. A notable observation is the increasing DOC concentration, which is significant for 55% of the observed streams. ; Includes references ; p. 65-89.
    Keywords: Water Quality ; Forested Watersheds ; Acidification ; Deposition
    ISSN: 0167-6369
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  • 2
    Language: English
    In: Forest Ecology and Management, 01 March 2014, Vol.315, pp.12-21
    Description: Knowledge gaps still exist concerning the resilience of Norway spruce growth to changing climate conditions especially outside their natural range. We used a dendroecological approach to assess growth resilience of Norway spruce to changing moisture availability on different sites in southwest Germany near the xerothermic range limits of this species. We described the temporal and spatial variation of Norway spruce tree-ring width, comparatively assessed the response of tree-ring width to changes in moisture availability between different study sites and assessed the capacity of Norway spruce growth to absorb disturbance by drought. To assess the capacity, we applied the concept of resilience and the concept of early-warning signals to tree-ring width data. The results indicated no adequate short-term adaptive capacity to changing climate conditions for the respective Norway spruce trees within the study period. Furthermore the results showed an enhancement of growth synchronicity among the trees at each study site which is highly correlated with changes in moisture availability. Critical slow down, loss of buffering ability and simultaneous increase in spatial correlation are indicative of a loss in growth resilience of Norway spruce. We assume that the capacity of Norway spruce trees to absorb disturbance in terms of their growth response to moisture deficits decreased presumably as a consequence of a series of drought events in the more recent past.
    Keywords: Norway Spruce ; Tree-Ring Width ; Moisture Availability ; Resilience ; Early-Warning Signals ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
    Source: ScienceDirect Journals (Elsevier)
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  • 3
    Language: English
    In: Environmental Monitoring and Assessment, 2011, Vol.174(1), pp.65-89
    Description: This study evaluates the acidification status and trends in streams of forested mountain ranges in Germany in consequence of reduced anthropogenic deposition since the mid 1980s. The analysis is based on water quality data for 86 long-term monitored streams in the Ore Mountains, the Bavarian Forest, the Fichtelgebirge, the Harz Mountains, the Spessart, the Black Forest, the Thuringian Forest, and the Rheinisches Schiefergebirge of Germany and the Vosges of France. Within the observation period, which starts for the individual streams between 1980 and 2001 and ends between 1990 and 2009, trends in chemical water quality were calculated with the Seasonal Mann Kendall Test. About 87% of the streams show significant ( p 〈 0.05) negative trends in sulfate. The general reduction in acid deposition resulted in increased pH values (significant for 66% of the streams) and subsequently decreased base cation concentrations in the stream water (for calcium significant in 58% and magnesium 49% of the streams). Reaction products of acidification such as aluminum (significant for 50%) or manganese (significant for 69%) also decreased. Nitrate (52% with significant decrease) and chloride (38% with significant increase) have less pronounced trends and more variable spatial patterns. For the quotient of acidification, which is the ratio of the sum of base cations and the sum of acid anions, no clear trend is observed: in 44% of the monitored streams values significantly decreased and in 23% values significantly increased. A notable observation is the increasing DOC concentration, which is significant for 55% of the observed streams.
    Keywords: Water quality ; Acidification ; Forested catchments ; Deposition ; Germany
    ISSN: 0167-6369
    E-ISSN: 1573-2959
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  • 4
    Language: English
    In: Journal of Plant Nutrition and Soil Science, August 2016, Vol.179(4), pp.443-453
    Description: Phosphorus (P) is essential for sustainable forest growth, yet the impact of anthropogenic impacts on P leaching losses from forest soils is hardly known. We conducted an irrigation experiment with 128 mesocosms from three forest sites representing a gradient of resin extractable P of the A‐horizon. On each site we selected a and a managed subsite. We simulated ambient rain (AR), anthropogenic nitrogen input (NI) of 100 kg (ha · a) and forest liming (FL) with a dolomite input of 0.3 Mg (ha · a). Soil solution was extracted from the organic layer, 10 cm depth and 20 cm depth of the mesocosms, and analyzed for molybdate reactive phosphorus (MRP) and molybdate unreactive phosphorus (MUP). Additionally, we separated colloids from the soil solution using Asymmetric Field Flow Fractionation for assessing the colloidal fraction of total element concentrations. NI increased MRP and MUP concentrations for all plots with one exception, while FL decreased MRP and MUP with the exception of another plot. While the irrigation treatments had little impact on the P‐richest site, MRP and MUP concentrations changed strongly at the poorer sites. The colloidal fraction of P in the soil solution equaled 38–47% of the total P load. Nitrogen input and liming also affected the Fe, Al, Ca, and Corg contents of the colloidal fraction.
    Keywords: Phosphorus ; Mesocosm ; Random Forest Modelling ; Molybdate ; Soil Colloids
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 5
    Language: English
    In: Forest Ecology and Management, March 1, 2014, Vol.315, p.12(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.foreco.2013.12.015 Byline: Simon Boden, Hans-Peter Kahle, Klaus von Wilpert, Heinrich Spiecker Abstract: acents We described the temporal and spatial variation of Norway spruce tree-ring width. acents We assessed the response of tree-ring width to changes in moisture availability. acents Results indicated no short-term adaptive capacity to changing climate conditions. acents Results showed an enhancement of growth synchronicity among trees. acents Indicatives of a loss in growth resilience were found. Article History: Received 5 August 2013; Revised 9 December 2013; Accepted 14 December 2013
    ISSN: 0378-1127
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Journal of the American Statistical Association, 1 September 2009, Vol.104(487), pp.899-911
    Description: Forest health monitoring schemes were set up across Europe in the 1980s in response to concerns about air pollution-related forest dieback (Waldsterben) and have continued since then. Recent threats to forest health are climatic extremes likely due to global climate change and increased ground ozone levels and nitrogen deposition. We model yearly data on tree crown defoliation, an indicator of tree health, from a monitoring survey carried out in Baden-Württemberg, Germany since 1983. On a changing irregular grid, defoliation and other site-specific variables are recorded. In Baden-Württemberg, the temporal trend of defoliation differs among areas because of site characteristics and pollution levels, making it necessary to allow for space-time interaction in the model. For this purpose, we propose using generalized additive mixed models (GAMMs) incorporating scale-invariant tensor product smooths of the space-time dimensions. The space-time smoother allows separate smoothing parameters and penalties for the space and time dimensions and thus avoids the need to make arbitrary or ad hoc choices about the relative scaling of space and time. The approach of using a space-time smoother has intuitive appeal, making it easy to explain and interpret when communicating the results to nonstatisticians, such as environmental policy makers. The model incorporates a nonlinear effect for mean tree age, the most important predictor, allowing the separation of trends in time, which may be pollution-related, from trends that relate purely to the aging of the survey population. In addition to a temporal trend due to site characteristics and other conditions modeled with the space-time smooth, we account for random temporal correlation at site level by an autoregressive moving average (ARMA) process. Model selection is carried out using the Bayes information criterion (BIC), and the adequacy of the assumed spatial and temporal error structure is investigated with the empirical semivariogram and the empirical autocorrelation function.
    Keywords: Biological sciences -- Ecology -- Applied ecology ; Physical sciences -- Astronomy -- Astrophysics ; Applied sciences -- Research methods -- Modeling ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences ; Information science -- Information analysis -- Data analysis ; Biological sciences -- Biology -- Botany ; Mathematics -- Mathematical objects -- Tensors ; Mathematics -- Pure mathematics -- Linear algebra ; Mathematics -- Applied mathematics -- Statistics
    ISSN: 01621459
    E-ISSN: 1537274X
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  • 7
    Language: English
    In: Ecological Modelling, 10 October 2016, Vol.337, pp.48-62
    Description: Accurate and reliable predictions of the future development of forest site productivity are crucial for the effective management of forest stands. Static models which simply extrapolate productivity into the future are inappropriate under conditions of environmental change since they lack a close link between fundamental environmental drivers and forest growth processes. Here we present a dynamic environment-sensitive site index model formulated in the framework of a nonlinear state space approach based on longitudinal data from long-term experimental plots. Estimation of the model parameters was carried out using the prediction error minimization method. Our aim was to identify dynamic relationships between site index and environmental variables and to make conditional predictions of the future development of site index under climate change scenarios. Nonlinear, interactive, as well as accumulative effects of environmental factors (climate/weather and nitrogen influx) on the growth response were considered in the model. In the study, we estimated the dynamic environment-sensitive site index model using data from 604 Norway spruce ( [L.] Karst.) long-term experimental plots in southwest Germany with measurement data covering a period of more than 100 years from the end of the 19th century until today. We used the calibrated model to project future site index changes under increasing growing season temperature scenarios. Conventional climate change impact studies usually utilize a gradient approach and apply space-for-time substitution for the parameterization of models that are calibrated using spatial variability in the data. In contrast, the approach presented here utilizes the longitudinal data structure of multiple real growth time series to simultaneously exploit spatial and temporal variation in the data to provide more reliable and robust projections. Limitations of the space-for-time substitution approach in forest growth modelling are discussed.
    Keywords: Norway Spruce ; Space-for-Time Substitution ; Nonlinear State Space Approach ; Longitudinal Data Structure ; Prediction Error Minimization Method ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 8
    Language: English
    In: Ecological modelling, 2016, Vol.337, pp.48-62
    Description: Accurate and reliable predictions of the future development of forest site productivity are crucial for the effective management of forest stands. Static models which simply extrapolate productivity into the future are inappropriate under conditions of environmental change since they lack a close link between fundamental environmental drivers and forest growth processes. Here we present a dynamic environment-sensitive site index model formulated in the framework of a nonlinear state space approach based on longitudinal data from long-term experimental plots. Estimation of the model parameters was carried out using the prediction error minimization method. Our aim was to identify dynamic relationships between site index and environmental variables and to make conditional predictions of the future development of site index under climate change scenarios. Nonlinear, interactive, as well as accumulative effects of environmental factors (climate/weather and nitrogen influx) on the growth response were considered in the model. In the study, we estimated the dynamic environment-sensitive site index model using data from 604 Norway spruce (Picea abies [L.] Karst.) long-term experimental plots in southwest Germany with measurement data covering a period of more than 100 years from the end of the 19th century until today. We used the calibrated model to project future site index changes under increasing growing season temperature scenarios. Conventional climate change impact studies usually utilize a gradient approach and apply space-for-time substitution for the parameterization of models that are calibrated using spatial variability in the data. In contrast, the approach presented here utilizes the longitudinal data structure of multiple real growth time series to simultaneously exploit spatial and temporal variation in the data to provide more reliable and robust projections. Limitations of the space-for-time substitution approach in forest growth modelling are discussed. ; p. 48-62.
    Keywords: Forests ; Environmental Factors ; Time Series Analysis ; Site Index ; Norway Spruce ; Prediction ; Growing Season ; Climate Change ; Temporal Variation ; Temperature ; Nitrogen ; Models ; Forest Management ; Prediction Error Minimization Method ; Longitudinal Data Structure ; Forest Stands ; Weather ; Space-For-Time Substitution ; Picea Abies ; Nonlinear State Space Approach ; Forest Growth ; Climate
    ISSN: 0304-3800
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 9
    In: Canadian Journal of Forest Research (Revue canadienne de recherche forestière), 2009, Vol.39(11), pp.2047-2058
    Description: Soil compaction caused by forest machinery changes the basic conditions for root propagation below skid trails. In consequence, lower fine-root densities have to be expected under wheel tracks compared with other skid trail strata that experience no direct traffic. Explorative data analysis of fine-root densities below a skid trail revealed that the fundamental assumptions for linear modelling were violated. Using a generalized linear model following a Poisson distribution with a log link function for the predictor variables together with an exponential covariance function to cope with spatial autocorrelation, the formal model criteria were met. In contrast to the linear models, generalized additive models provide flexible surface estimators that enable us to model continuous response surfaces. In addition, generalized additive models allow for the calculation of confidence intervals for the estimated density surface and for the use of inferential statistics, such as comparisons between depth gradients of fine rooting at distinct transect locations or depth layers. These model characteristics improve the possibility to recognize differences and to evaluate fine-root disturbances below skid trails without integrating uncertain strata information. They also enhance the options for determining the duration of time that is necessary to restore the rooting capacity on formerly compacted soils.
    Description: La compaction du sol cause par la machinerie forestire modifie les conditions essentielles la propagation des racines sous les sentiers de dbardage. Par consquent, on doit sattendre une plus faible densit de racines fines sous les ornires comparativement aux autres strates des sentiers de dbardage qui ne subissent pas de trafic direct. Lanalyse de donnes exploratoires de densit des racines fines sous un sentier de dbardage rvle que les hypothses de base de la modlisation linaire ne sont pas respectes. Les critres formels du modle ont t respects en utilisant un modle linaire gnralis qui suit une distribution de Poisson avec un lien logarithmique pour les variables indpendantes et une fonction exponentielle de covariance pour tenir compte de lautocorrlation spatiale. Contrairement aux modles linaires, les modles linaires additifs gnraliss fournissent des estimateurs de surface flexibles qui permettent de modliser des surfaces de rponse continue. De plus, les modles linaires additifs gnraliss permettent de calculer les intervalles de confiance pour la surface de densit estime et de faire des statistiques dductives, telles que des comparaisons entre des gradients de profondeur des racines fines diffrents endroits dun transect ou pour diffrentes couches de profondeur. Ces caractristiques des modles augmentent la possibilit de dtecter les diffrences et dvaluer les perturbations des racines fines sous les sentiers de dbardage sans intgrer de linformation incertaine au sujet des strates. Elles amliorent aussi les possibilits de dterminer le temps ncessaire la restauration de la capacit denracinement dans les sols qui ont t compacts.
    Keywords: Forest Soils -- Research ; Roots (Botany) -- Research ; Soil Science -- Research;
    ISSN: 0045-5067
    E-ISSN: 1208-6037
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  • 10
    Language: English
    In: Canadian journal of forest research =, 2013, Vol.44(1), pp.71-81
    Description: Fine-root distributions (FRDs) of forest stands are hypothesized to be a reflection of the influence of site properties on the intrinsic rooting strategies of trees. Based on forest soil survey data, we present a multivariate approach to identify the main parameters of FRD patterns of Central European forests, compare them with the FRD model according to Gale and Grigal (1987), and aim to detect the decisive site and soil properties. Two main parameters for the description of FRDs were found: one describes “shallowness” and the other additionally characterizes “divergence” from an evenly decreasing FRD with depth. With these two parameters, distinct FRD patterns could be described better than with absolute values of depth-dependent fine-root densities or with the compared FRD model. Comparing all sites, no significant differences occurred regarding stand types for most of the analysed fine-root parameters. Specific site and soil properties were seemingly more responsible for the expression of FRD. Results of multivariate analyses suggest that the shape of FRDs is mainly a reflection of the trees’ strategy to optimally adapt to the local soil physical and hydrological conditions. Soil chemical properties were of increased relevance when sites with either spruce or beech were analysed and for the prediction of uneven FRDs. The applied soil survey design enabled us to identify parameters, which can describe FRD patterns and how they are influenced by several soil and site properties in general. These multivariate relationships should be considered and discussed in the context of ecological forest models in further research. ; p. 71-81.
    Keywords: Forest Soils ; Forests ; Hydrology ; Rooting ; Fine Roots ; Fagus ; Prediction ; Models ; Soil Chemical Properties ; Multivariate Analysis ; Picea ; Soil Surveys ; Forest Stands ; Trees
    ISSN: 1208-6037
    ISSN: 00455067
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