Issue/Heft 19 (2020)

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© AFSV; Waldökologie, Landschaftsforschung und Naturschutz (Forest Ecology, Landscape Research and Nature Conservation) - Heft 19, 2020

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Impressum und Inhaltsverzeichnis

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HEINKELE, T., KNOCHE, D., GEMBALLA, R., PETZOLD, R.: Hydrologische Eigenschaften von Waldhumusformen: Wasserspeicherpotenziale, Wiederbefeuchtungs- und Versickerungsverhalten

(Hydrological Properties of forest humus layers: Water storage potential, rewetting and infiltration behaviour)

Abstract
As periods of drought will increase because of climate change, humus layers on top of mineral soils might provide additional soil water storage capacity especially at sites with limited available soil water capacity in mineral soils. However, information about hydraulic properties of humus layers of forest soils is scarce. Therefore, humus layers of 41 typical forest stands of the northeastern lowland and adjacent hilly and mountain areas in Saxonia, Germany were investigated. The results show that the Of and Oh layers have very high total pore volumes (> 80 % by volume), are characterized by high field capacity (> 40 % by volume) and high available water capacity (15–30 % by volume). Due to their limited thickness, their contribution to the available water storage capacity in the root area is low. The water storage potentials of humus layers derived from sessile or red oak (Quercus petraea, Quercus rubra) litter are slightly higher than those from Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). In addition, humus layers react strongly hydrophobic when dry. We measured the relation of water content versus hydrophobicity of Of and Oh layers systematically and found that pronounced hydrophobic features already occur at water contents far above the permanent wilting point. Of and Oh layers differ only slightly, as well as humus forms from different needle and leaf litter. The water-repellent properties of the humus layers strongly influence the process of rewetting and infiltration. Continuous water content measurements at five experimental plots show that precipitation events in summer do not rewet humus layers that were dried out and thus developed hydrophobic conditions during dry and warm periods. Nevertheless, the rainwater infiltrates unhindered and seeps into the upper mineral soil without delay. Dry humus deposits are not an infiltration inhibitor due to their extremely high coarse pore contents, at least not on flat sites. Their rewetting often requires longer periods of at least 4 weeks and persistent, evenly distributed rainfall. Therefore, especially during summer dry periods, they do not provide a buffer for precipitation, i.e. just when the greatest need for water exists.

>> Volltextversion (pdf 2.8 M; Heft 19-Aufsatz 1; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01910)

SIEBERT, I., JANSEN, M.: Waldvegetation, Bodenchemismus und Streuqualität auf zwei Eichenstandorten des Nordwestdeutschen Tieflands

(Forest vegetation, soil chemistry, and litter quality in two Oak stands in the Northwest-German Lowlands)

Abstract
The two oak stands “Harmbütteler Holz” (HH) and “Maaßel” (M), which are located close to each other in the area “Südheide”, show a distinctly different vegetation composition with the same geological sequence of glacial covering sand, loamy clay and marly clay. Previous soil chemical investigations have not given any explanations for the occurrence of typical herbs, normally existing on base-rich or carbonate sites. However, both locations have different tree species compositions. Common oak (Quercus robur), small-leaved linden (Tilia cordata) and hornbeam (Carpinus betulus) grow in the M, while common oak and beech (Fagus sylvatica) predominate in the HH. The aim of the study was to identify possible factors that can explain the differences in herbal ground vegetation between M and HH. Vegetation records from 2009 to 2015 were used for the data analysis. The topsoil was sampled in five and the deep drilling in three places on a small scale in 2.5 cm steps. In addition, five humus samples were taken and the nutrient concentrations of the tree litter were determined. A litter bag study provided data on litter decomposition. The results show that typical types of old forest species grow on both sites. Additionally, both stands have most likely been continuously forested since the late 18th century at the latest and can be characterized as ancient forest. The sequence of the geological substrates is very similar and does not provide an explanation, the deep drilling did not hit any calcareous Mesozoic bedrock. The soil chemical properties show that with the high spatial resolution, the pH values, the cation exchange capacity, and the base saturation are higher, especially in the top centimetres in the M than in the HH. Compared to HH, the litter of M has higher concentrations of base cations Ca, Mg and K (Mb) and a lower proportion of Al, Fe and Mn (Ma). The higher Mb-cation content leads to faster decomposition and improved humus form. In contrast, the slower litter decomposition of the HH releases relatively more Ma-cations. Especially the small-leaved linden and hornbeam show properties of an effective “base pump”. It seems that vegetation at the site M reflects the more favourable soil chemical state of the uppermost areas of the mineral soil and the better-quality humus form, which is due to the improved litter turnover.

>> Volltextversion (pdf 4.2 M; Heft 19-Aufsatz 3; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01931 )
  

MELLERT, K.H., GÖTTLEIN, A., WELLBROCK, N.: Die Bedeutung des Bodens für die Standortbindung von Baumarten in Deutschland

(The relevance of the soil for the habitat specificity of tree species in Germany)

Abstract
In ecological niche models (ENM), the soil regularly plays a subordinate role compared to the climate. The German Forest Soil Inventory (BZE II) offers an ideal database for the realistic assessment of the contribution of soil properties to the habitat specificity of tree species. The factors of soil chemistry were the C/N ratio and the base saturation (BS), the available water capacity (AWC) as soil physical parameters, the average temperature in the vegetation period (Tmp) and the climatic water balance (CWB) as climate and water budget parameters. Among the possible modeling techniques, Maxent proved to be particularly suitable, since this machine learning method requires only a few observations and the aim was to analyze the habitat specificity of as many tree species as possible. Only for eight out of 40 tree species too few observations were available for modeling. In 20 cases, the overall model quality was low, especially because of a weak limitation of tree species due to the climate (period 1970–2000) and the prevailing soil conditions within Germany (soil indifferent tree species). According to the models, there is a strong dependency on soil chemistry for 17 tree species. The soil was hardly relevant for three tree species compared to the climate. The impact of AWC was generally small. For most tree species, the occurrences were more determined by the C/N ratio than by BS. For the tree species most dependent on the soil, however, the variable importance of the BS was similarly large. The strong influence of the C/N ratio is also due to the recycling of nutrients to the soil humus via the litter and is therefore not a purely soil-based effect. The results are fundamentally in line with previous assessments of tree species requirements. However, deviating findings as well as diverging expert opinions on habitat specificity underscore the need for data-based methods to objectify and readjust our knowledge. With the help of databased ecograms, the site-specific preferences and tolerances of rare and interesting alternative tree species in climate change could be estimated, for which there are hardly any relevant references available in Central Europe.

>> Volltextversion (pdf 1.6 M; Heft 19-Aufsatz 4; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-01946)

SIEMONSMEIER, A., FÖRSTER, B., BLASCHKE, M.: Forest structures and carbon storage in managed and unmanaged forests along an altitudinal gradient in a central European low mountain range

(Waldstrukturen und Kohlenstoffvorräte in bewirtschafteten und unbewirtschafteten Wäldern entlang eines Höhengradienten in einem mitteleuropäischen Mittelgebirge)

Abstract
Along an altitudinal gradient in the Bavarian Forest, a German low mountain range, forest structures on 144 sampling plots located in eight strict forest reserves and nearby managed forest stands were investigated. Live woody biomass volumes increased with decreasing altitude, whereas deadwood volumes did not show a dependency on elevation. Mean wood volumes were on average around 40 % higher in strict forest reserves than in managed forest stands, with decreasing discrepancies at higher altitudes. Silvicultural management had a strong impact on deadwood volumes, leading to higher mean deadwood volumes in the strict forest reserves than in managed forests. Probability of presence models for the main tree species indicated shifts of the curve maxima towards higher altitudes for beech and silver fir in the strict forest reserves, when data from 2009 and 2018 were compared. Total carbon stores in the strict forest reserves increased from the first survey in 2009 to 2018 in most cases, on average by around 40 to/ha. The two reserves at the highest altitudes (1,174 and 1,211 m a .s. l.), however, suffered from recent storm damages and severe spruce bark beetle outbreaks, which led to decreased above ground carbon stores but increased coarse woody debris carbon stores.

>> Volltextversion (pdf 3.6 M; Heft 19-Aufsatz 2; Original paper; Language: English; urn:nbn:de:0041-afsv-01924)