Issue/Heft 12 (2011)

Details

© AFSV; Waldökologie, Landschaftsforschung und Naturschutz (Forest Ecology, Landscape Research and Nature Conservation) - Heft 12, 2011

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Impressum und Inhaltsverzeichnis

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SCHWÄRZEL, K., FEGER, K.-H., KÖSTNER, B., BERNHOFER, C.: Wasserhaushalt von Wäldern - Editorial

>> Volltextversion (pdf 561 K; Heft 12-Editorial; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01218)

GAUER, J., FEGER, K.-H., SCHWÄRZEL, K.: Erfassung und Bewertung des Wasserhaushalts von Waldstandorten in der forstlichen Standortskartierung: Gegenwärtiger Stand und künftige Anforderungen

(Measurement and assessment of water dynamics of forest sites within the framework of forest site mapping: current conditions and future requirements)

Abstract
Measuring and assessing water dynamics is crucial for site-adapted and sustainable management as well as for the multifunctionality of forests. This paper outlines the importance of a differentiated analysis of water conditions within the framework of applied forest site mapping in Germany. The differences and similarities that have evolved over time in the methodological approaches taken by the individual federal states are also presented. The limitations of current practices for the assessment of water dynamics are discussed in the context of future requirements related both to modifications in forest management and to the already-perceptible effects of climate change. Manifold challenges will result, related in particular to model-based enhanced quantification of the water regime and the integration of dynamic properties of climate, soils, and stands, as well as the regionalization and upscaling to the catchment level.

>> Volltextversion (pdf 868 K; Heft 12-Aufsatz 2; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01226)

BERNHOFER, C., GRÜNWALD, T., SPANK, U., CLAUSNITZER, F., EICHELMANN, U., FEGER, K.H., KÖSTNER, B., PRASSE, H., MENZER, A., SCHWÄRZEL, K.: Mikrometeorologische, pflanzenökologische und bodenhydrologische Messungen in Fichten- und Buchenbeständen des Tharandter Waldes

(Micrometeorological, plant-ecological, and soil-hydrological measurements in stands of spruce and beech in the Tharandt forest)

Abstract
This paper addresses micrometeorological, plant-ecological, and soil-hydrological measurements in stands of spruce and beech as a means to understand the processes. The long-term flux site Anchor Station Tharandt (dominated by 120-year-old spruce) shows the high dynamics of land surface- atmosphere interactions as well as the climatologically relevant effects on turbulent energy flux partitioning, carbon sequestration, and evapotranspiration (ET). Climate, phenology, and fluxes support the idea of dividing the year into an 'active phase' (April–September) and a 'dormant phase' (October-March); carbon sequestration, available energy (net radiation), and sensible heat flux are almost negligible in the dormant season. Only ET shows a significant contribution to the annual budget (25 % of the active phase) from interception (evaporation from wetted needles) driven by sensible heat flux from the atmosphere. The interannual variation of the fluxes is generally small (e. g., 500 to 650 gC m-2 yr-1 of C uptake) even for the severe drought year of 2003 (400 gC m-2) or with thinning in 2002. Compared to the beech site, the spruce site - at least in the active season - experienced similar rates of ET but smaller rates of C uptake. Canopy drip was 55 % of precipitation at the spruce site. Canopy drip (40 %) and stem flow (25 %) added up to 65 % of canopy precipitation at the beech site. This difference likely explains the generally higher soil moisture at the beech site. As a consequence of this study, models with sufficient complexity are recommended to represent the structural differences of different forest types including their phenophases. For a better representation of forests, e. g., in climate models, land surface-atmosphere interactions must be included.

>> Volltextversion (pdf 923 K; Heft 12-Aufsatz 3; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01230)

KÖSTNER, B., CLAUSNITZER, F.: Die Transpiration eines Fichten– und Buchenbestandes unter Bodentrockenheit im Tharandter Wald

(Transpiration of a spruce and beech stand under soil drought conditions in the Tharandt Forest)

Abstract
To evaluate the water balance of a site, requirements of the forest stand under changing environmental conditions have to be considered. Among the different components of the site water balance, stand transpiration represents the physiological response of the trees and can be taken as a link to carbon relations. A regulating and hence critical parameter mediating between water and carbon balance is canopy conductance. Water-use efficiency is an indicator of this relationship. At a spruce and beech site, xylem sap flow measurements were applied to estimate canopy transpiration (Ec) and canopy conductance (gc). During the growing season of 2006, Ec at the spruce site (161 mm season-1) was significantly lower than at the beech site (182 mm season-1) while the total-year balances were similar. This was related to a period of soil drought during summer which was more pronounced at the spruce site than at the beech site. In contrast to beech, canopy conductance of spruce was reduced to minimal values independent of atmospheric conditions, and water-use efficiency was increased. From the findings it can be concluded that site conditions and tree species lead to measurable differences in the water balance of sites which should accordingly be expressed in water-balance models. The presented measured data are fundamental to value transpiration-related indicators of water-balance models.

>> Volltextversion (pdf 554 K; Heft 12-Aufsatz 4; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01248)

MÜLLER, J.: Die Anwendung von Lysimetern zur Ermittlung des Wasserhaushaltes in Wäldern des nordostdeutschen Tieflands

(The use of lysimeters to determine the water balance in forests in northeastern Germany)

Abstract
The region of Eberswalde in northeastern Germany is amongst the driest and also most densely wooded regions in Germany. Low annual precipitation between 500 and 600 mm and the light sandy soils lead to limited water availability. Therefore the hydrological functions of forests play an important role in the regional water budget, water supply and water distribution. The aim of forest hydrologic research is to investigate the influence of the different types of forest structures on the water balance of the landscape and on the partial parameters of the water balance equation. Lysimeters are suitable measuring instruments to investigate evaporation and groundwater production in areas with granular soils and loose rocks. The use of lysimeters of different construction has a tradition of more than 100 years in this region. To investigate the water consumption of different tree species, lysimeters were installed in the lowlands at Britz near Eberswalde under comparable site conditions. In 1972 nine lysimeters with a surface of 100 m2 and a depth of 5 m were built. The stand development of Scots pine (Pinus sylvestris L.), common beech (Fagus sylvatica L.), larch (Larix decidua L.) and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) have been observed and recorded since planting with regard to growth course, net primary production and water fluxes. The choice of tree species is of critical importance for determining the amount of groundwater production below forests. The structural properties of the ground vegetation in terms of composition and coverage influence the soil available water content considerably with effects on tree growth of Scots pine forests during the vegetative period. These results were obtained with the use of specially developed weighable lysimeters.

>> Volltextversion (pdf 838 K; Heft 12-Aufsatz 5; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01254)
  

MORGENSTERN, Y., PUHLMANN, H., WILPERT, K. von: Erfassung und erste Analysen von räumlichen Mustern der Bodenfeuchte auf Waldstandorten

(Detection and first analyses of spatial patterns of soil moisture at forest sites)

Abstract
The measuring concept of randomised moving plots (RMP) is applied in four forest areas in Baden-Württemberg (southern Germany) to quantify the temporal and spatial variability of soil moisture and the parameters that influence it. Our investigations aim at (i) collecting data for the evaluation of a physically based, distributed water transport model, (ii) identifying influencing parameters and (iii) developing a transfer model which describes soil moisture as a function of time-constant but spatially variable site parameters on the one hand (e. g., terrain attributes, soil texture, forest stand structure) and time-dependent but spatially invariant global variables (e. g., air temperature, catchment runoff) on the other. The spatio-temporal variability of soil moisture (0–20 cm mineral soil depth) was measured simultaneously at 31 positions over a period of 14 days. Measuring positions were changed randomly every 14 days. The global variables were continuously measured at one or two positions within each investigation area. The site parameters were measured or described for each of the measuring positions. Using multivariate statistics methods, such as cluster analysis or classification and regression trees, the site parameters which influence the soil moisture dynamics were identified. This paper presents first results and discusses one landscape section in more detail.

>> Volltextversion (pdf 2.8 M; Heft 12-Aufsatz 6; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01266)
  

PUHLMANN, H., WILPERT, K. von: Test und Entwicklung von Pedotransferfunktionen für Wasserretention und hydraulische Leitfähigkeit von Waldböden

(Testing and development of pedotransfer functions for water retention and hydraulic conductivity of forest soils)

Abstract
The hydraulic properties of soils, i. e., their capability to store and to conduct water, largely regulate the availability of soil water for plants and the risk of water shortage in forests. To date, only a few systematic surveys on the hydraulic properties of forest soils have been done. We conducted multi-step outflow experiments to derive data on soil water retention and unsaturated hydraulic conductivity for 1504 undisturbed samples from forest soils in Baden-Württemberg. Using complementary measurements (fractions of fine and coarse soil, bulk density, organic carbon content), pedotransfer functions were developed for the prediction of the Mualem/van Genuchten model parameters. The predictions of the new pedotransfer functions were compared with various pedotransfer functions from the literature. An advantage of the new pedotransfer functions is that they provide an unbiased estimate of the hydraulic properties of the forest soils in Baden-Württemberg, and their predictive ability is comparable to those of published pedotransfer functions.

>> Volltextversion (pdf 2.1 M; Heft 12-Aufsatz 7; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01276)
  

ZIRLEWAGEN, D., WILPERT, K. von: Regionalisierung bodenphysikalischer Eingangsgrößen für bodenhydraulische Pedotransferfunktionen

(Regionalization of soil physical input variables for soil hydraulic pedotransfer functions)

Abstract
Many studies in soil science provide qualitative or (semi-) quantitative assessments of soil physical properties such as soil texture or percentage of soil skeleton (the >2 mm fraction). In this paper, we describe the process of upscaling soil physical properties measured during the second Forest Soil Monitoring Census (BZE II). In order to enhance the data basis for process-oriented hydrology models at the landscape level, the use of upscaling techniques based on point-related monitoring data is essential. The statistical methods used in this work included ordinary least square regression (OLS) and geostatistics. One aim of this study was to evaluate how the different spatial scales used for stratifying statistical approaches affect the quality of spatial estimates. When applied to soil physical properties, our evaluations showed that, by using a stratified modeling approach, the accuracy of the estimates could be improved compared to global modeling approaches. Thus the regression models displayed comparatively high coefficients of determination ranging from 0,59 to 0,7 (for soil skeleton), 0,52 to 0,65 (bulk density), 0,7 (depth of soil development) and 0,66 to 0,8 (soil texture). Only in the case of the response variable fine root density were the coefficients of determination markedly below 0,5 (0,2–0,4). One of the reasons for this could be the small-scale variation in silvicultural site conditions such as tree species distribution or stand density.

>> Volltextversion (pdf 695 K; Heft 12-Aufsatz 8; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01286)
  

RUSS, A., RIEK, W.: Methode zur Ableitung des Grundwasserflurabstandes aus Karten der forstlichen Standortskartierung und digitalen Geländemodellen in Brandenburg

(A method to estimate groundwater depth from forest site mapping data and digital elevation models)

Abstract
In this paper a new approach for estimating continuous groundwater depths using forest site mapping data of the federal state of Brandenburg and digital elevation models is presented. The underlying idea of this approach is to combine the upper and lower limits of the mapping units (groundwater depth classes of special site types and site type groupings) and the relative elevations inside each individual site type area calculated from the digital elevation model. By this means, consideration of the landscape morphology allows groundwater depths to be estimated continuously for grids with various resolutions. Depending mainly on the spatial and vertical resolution of the applied digital elevation model, the results are improved significantly compared to simply regionalizing site-type-specific mean values. The presented method was used to generate continuous groundwater depths based on the existing forest site maps of the federal state of Brandenburg for more than two-thirds of the forest area. The data obtained will be used in a larger research project, carried out at the Forestry Competence Centre, Eberswalde, to analyze regional and site-specific impacts of climate change.

>> Volltextversion (pdf 2.9 M; Heft 12-Aufsatz 9; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01293)
  

FALK, W., OSENSTETTER, S., DIETZ, E.: Konzept für ein quantitatives Verfahren zur Kennzeichnung des Lufthaushaltes von Waldböden in Bayern

(A concept for quantitative characterization of the air balance in Bavarian forest soils)

Abstract
Site-specific descriptions of soil water balance and soil air balance are important for tree species selection in forestry. We present a concept for describing the soil air balance for Bavaria. It is an enhancement of an empirical multiple linear regression model that explains soil oxygen deficiency in terms of topographic, climate and soil parameters. We modelled numerous combinations of site conditions with the hydrologic model LWF-Brook 90 to determine an estimator for soil oxygen deficiency. This estimator reflects water logging that persists for a certain length of time. In a second step we will develop a new regression model and combine this information with topographical information about additional water fluxes in a GIS. We aim to combine both steps in order to describe the air balance of forest soils for the entirety of Bavaria.

>> Volltextversion (pdf 540 K; Heft 12-Aufsatz 10; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-012102)
  

PETERS, R., CLAUSNITZER, F., KÖSTNER, B., BERNHOFER, C., FEGER, K.H., SCHWÄRZEL, K.: Einfluss von Boden und Bestockung auf den Standortswasserhaushalt

(Impact of soil and stand properties on soil water conditions)

Abstract
As an objective water balance classification is lacking for forest sites, efforts were made to develop a model-based site classification system taking into account the effects of relief, soil and stand type on soil water conditions. As a first step, this paper displays the results of a BROOK 90 application evaluating the influence of these three factors on soil water balance with a strong emphasis on drought conditions. Model runs have been carried out for four different soil types, four stand types and a meteorological input covering the range of typical forest sites in the Tharandt Forest as a testing area. Concepts of drought stress quantification help to point out the effects of stress on the sites. In drought years, deciduous trees and soils with limited water retention properties show the effects of drought stress more strongly. The effects of both soil and stand properties were of the same magnitude as the influence of the conventionally considered relief-based meteorological variation at the site.

>> Volltextversion (pdf 633 K; Heft 12-Aufsatz 11; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-012117)  

PETERS, R., SCHWÄRZEL, K., FEGER, K.H.: Fuzzy-Inference-Systeme zur Regionalisierung des Standortswasserhaushaltes von Wäldern

(Regionalization of the site water balance in forests using fuzzy inference systems)

Abstract
Relief-dependent variations in micro-climatic parameters control evaporation and soil water conditions of forests. Therefore, mapping of soil water conditions in mountainous terrain requires that model computations have a high spatial resolution. Unfortunately, highly sophisticated, physically based modeling in combination with a large number of model runs leads to demanding computation costs. To overcome these shortcomings, a physically and physiologically based water balance model was combined with fuzzy inference systems. Grid-point-specific factors representing the systematic alteration of the station data due to the topography are the basis for the parameterization of the antecedent side of the fuzzy system. Model outputs of the water balance model BROOK 90 were used directly as parameters of the consequents of the fuzzy rules. Thus, the parameterization of the fuzzy inference system is model-based and objective, and parameter training is not required. The validation of the method shows only small differences between fuzzy system outputs and BROOK 90 results.

>> Volltextversion (pdf 913 K; Heft 12-Aufsatz 12; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-012128)  

SCHWÄRZEL, K., PETERS, R., PETZOLD, R., HÄNTZSCHEL, J., MENZER, A., CLAUSNITZER, F., SPANK, U., KÖSTNER, B., BERNHOFER, C., FEGER, K.H.: Räumlich-differenzierte Berechnung und Bewertung des Standortswasserhaushaltes von Wäldern des Mittelgebirges

(Spatially differentiated modeling and evaluation of soil water conditions in forest sites of low mountain ranges)

Abstract
The forest hydrological model BROOK 90 was integrated into a GIS framework to calculate and evaluate soil water conditions in forest sites based on climate, topography, soil, and tree species. Model results are visualized in a novel forest site map using indicators for soil drought, soil water excess, and transpiration constraints. Based on knowledge of the number of days in which thresholds of these indicators were exceeded, an evaluation framework for soil water conditions was developed. The model was tested at the Tharandt Forest for an area with varying soil conditions and different tree species. Results can be used to derive and test new forest management strategies. For instance, recommendations for achieving optimum growth based on tree species or stand structure choices can be derived. Further research should focus on relating soil water indices with growth indices.

>> Volltextversion (pdf 1.9 M; Heft 12-Aufsatz 13; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-012139)