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  • 1
    Language: English
    In: Plant and Soil, 2004, Vol.264(1), pp.13-24
    Description: Water-plant relations play a key role in the water cycling in terrestrial ecosystems. Consequently, changes in tree species composition may have distinct effects on the water retention capacity as well as on the pattern of streamflow generation. Such changes may result from modified interception properties and transpiration related to differences in canopy properties and root distribution. In order to evaluate the potential hydrological effects of the current silvicultural conversion from monocultural conifer stands into mixed or pure deciduous stands the hydrological model BROOK90 was applied to two forested upland catchments in Germany. The Rotherdbach catchment (9.4 ha, 93 yr-old Norway spruce) is situated in the Eastern Ore Mountains. The Schluchsee catchment (11 ha, 55-yr-old Norway spruce) is located in the higher altitudes of the Black Forest. The calibrated model is capable to describe rather well the temporal variation of streamflow but also the portions of the individual flow components. Data for a beech scenario were adapted for each site using a standard parameter set for deciduous trees provided by BROOK90 . The annual discharge in the fictional beech stand at Rotherdbach is 30 to 50% higher compared to spruce with an increase of soil moisture and especially the slow streamflow components. This mainly results from low interception rates during winter time. In contrast, the spruce stand has a permanently higher interception rate. Effects of tree species conversion are moderate at Schluchsee. The annual discharge of a fictional beech stand at Schluchsee is 7 to 14% higher compared to spruce. There in contrast to Rotherdbach, effects of tree species conversion on soil moisture dynamics are small since vertical percolation in the highly permeable soil dominates and precipitation is abundant. Practical forestry will favorably establish mixed beech–spruce rather than pure beech stands. However, it is critical to simulate mixed stands with BROOK90 . Therefore, a simple summation of model results from spruce and beech according to their respective area in a fictional mixed stand can only be a first approximation. Advanced hydrological simulation of mixed stand conditions should regard interactions of tree species and spatial parameter distribution. However, this is not yet feasible due to a distinct lack of information. As a consequence, there is a strong need to collect relevant hydrological and ecophysiological data in mixed stands in the future.
    Keywords: beech ; BROOK90 ; forest transformation ; model forecast ; spruce ; streamflow
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    Language: English
    In: Biogeochemistry, 2003, Vol.65(3), pp.341-368
    Description: The biogeochemical input-output fluxes of two forested catchments with contrasting levels of atmospheric deposition were investigated in Germany. This paper focuses on the effects of recent changes in atmospheric inputs on the chemical composition in the soil solution and stream. The catchment 'Schluchsee' (Black Forest; SW Germany) is characterized by relatively low atmospheric inputs whereas 'Rotherdbach' (Ore Mountains; E Germany) received significant amounts of acid deposition (mainly originating from SO 2 emissions) until recent years. Both sites reveal decreases in H + and S deposition during the 1990s. This pattern is typical when compared to trends in Europe. In response to the reduced S deposition, soil solution and streamwater SO 4 2− concentrations decreased significantly. A net release of SO 4 2− (output 〉 input) was observed at both sites due to the release of S previously stored in the soil. The level of N deposition was more or less constant at both sites. At Schluchsee, NO 3 − concentration in streamwater remained more or less unchanged, whereas a decrease at Rotherdbach was observed. A recovery from acidification was found in seepage water as indicated by increasing acid neutralizing capacity (ANC). Streamwater ANC increased only in the permanently acidified Rotherdbach. No change of ANC was observed in the Schluchsee stream, which was characterized by episodic acidification during high-flow conditions. Nevertheless, the key factor controlling the recovery from surface water acidification was the type, amount and distribution of stored S pools in the ecosystem. Thus, time series analysis of long-term data of input-output chemistry can be a valuable instrument in order to improve the understanding of linked terrestrial-aquatic systems and give useful clues for modeling efforts.
    Keywords: Atmospheric deposition ; Forested catchments ; Norway spruce ; Recovery from acidification ; Soil leachate ; Streamwater
    ISSN: 0168-2563
    E-ISSN: 1573-515X
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  • 3
    Language: German
    In: Forstwissenschaftliches Centralblatt vereinigt mit Tharandter forstliches Jahrbuch, 1999, Vol.118(1), pp.345-354
    Description: Die Umsetzungen von Nitrat und Sulfat wurden im Hinblick auf die Bachwasserqualität in einem kleinen bewaldeten Wassereinzugsgebiet im Schwarzwald untersucht. Analysen von Saugkerzenwässern aus dem dauervernäßten Randbereich der Bäche geben Hinweise auf erhebliche reduktionsbedingte Nitratverluste. Dies deckt sich mit Ergebnissen eines Laborversuchs, bei dem nitrathaltige Lösungen durch Bodensäulen aus einem Quellmoorgley perkoliert wurden. Während die Nitrat-Verluste offensichtlich durch Denitrifikation bedingt sind, überlagern sich bei der Sulfat-Dynamik verschiedene Prozesse. Insgesamt werden die beobachteten Reduktionsprozesse durch höhere Temperatur und lange Kontaktzeit mit der Festphase begünstigt. Die Auswirkungen auf andere hydrochemische Parameter (insbesondere pH-Wert und Säureneutralisationskapazität) werden diskutiert. Transformations of nitrate and sulfate were investigated with respect to streamwater quality in a forested headwater catchment in the Black Forest (SW Germany). Analyses of seepage collected with ceramic cups in the waterlogged riparian zone provide evidence for a distinct removal of nitrate due to reduction processes. This is in accordance with results from a laboratory experiment. Solutions enriched with nitrate were percolated through soil columns from a histic gleysol. Apparently, nitrate removal results from denitrification, whereas in the dynamics of sulfate various processes appear to be superimposed. In total, the reduction processes observed are favoured by higher temperatures as well as by longer times of contact with the solid phase. The effects on other hydrochemical parameters (notably pH-value and acid neutralizing capacity) are discussed.
    Keywords: water quality ; water acidification ; nitrate ; sulfate ; denitrification ; riparian zone
    ISSN: 0015-8003
    E-ISSN: 1439-0337
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  • 4
    Language: German
    In: Forstwissenschaftliches Centralblatt vereinigt mit Tharandter forstliches Jahrbuch, 2000, Vol.119(1), pp.249-262
    Description: In zwei kleinen Wassereinzugsgebieten im Hochschwarzwald wurde im Zeitraum 1989–1998 die zeitliche Dynamik der Wasserqualität in Abhängigkeit von der Abflussmenge untersucht. In einem der Einzugsgebiete war 1990 eine forstübliche dolomitische Kalkung (4 t ha −1 ) erfolgt. Für eine episodische Versauerung bei hohen Abflüssen ist in erster Linie die Mobilisierung von Nitrat verantwortlich. Säurepufferung und Kationenzusammensetzung sind stark an die zeitlich variablen Fließwege im Einzugsgebiet gekoppelt. Die Bodenkalkung bewirkte nur verhältnismäßig geringe Veränderungen der Wasserqualität. Allerdings war die Säureneutralisationskapazität bei Spitzenwerten des Abflusses tendenziell leicht erhöht. Trotz kalkungsbedingter verstärkter mikrobieller Aktivität und Nitrifikation in den Oberböden blieben die Nitrat-Konzentrationen im Bachwasser nahezu unverändert. Angesichts der veränderten Depositionssituation, wonach der S-Eintrag in jüngster Vergangenheit stark zurückgegangen ist, der N-Eintrag aber anhält, ist mittel- bis langfristig mit einer weiteren Verbesserung der N-Verfügbarkeit in Wäldern zu rechnen. Somit besteht ein zunehmendes Risiko für NO 3 − -Auswaschung nach Kalkung. Diese Entwicklung ist bei der künftigen Planung großflächiger Waldkalkungen zu beachten. In two small watersheds in the upper Black Forest (SW Germany) the temporal variation of water quality in relation to runoff dynamics was investigated during the period of 1989 through 1998. In 1990, one of the two watersheds was limed according to forest management practice (4 t dolomite ha −1 ). Episodic acidification during high-flow conditions is primarily due to the mobilization of nitrate. Acid buffering and cation composition were related to the time-variable flow paths in the watershed. The effects of soil liming on water quality were relatively small. Nevertheless, the acid neutralizing capacity during peak runoff events tended to be slightly improved. Even though microbial activity and nitrification were enhanced in the top-soils as a result of liming, the nitrate concentrations in the stream increased only slightly. With regard to recent changes in the atmospheric deposition pattern (distinct decline in S while N endures) in the middle to long term a better availability of N in forests can be expected. As a consequence, there is an increasing risk of NO 3 − leaching after liming. This development should be taken into account when large-scale liming operations in forests are planned in the future.
    Keywords: Forested watersheds ; water quality ; water acidification ; nitrate ; sulfate ; runoff dynamics ; forest soil liming
    ISSN: 0015-8003
    E-ISSN: 1439-0337
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