Zur Genese der Marschböden. I. Der Einfluß von Sediment- und Bodengefüge

On the genesis of tidal marsh soils I. The influence of sediment- and soil-structure The significance of sediment structure for soil structure has often been disregarded when discussing the properties and genesis of tidal marsh soils. After defening several terms that are often misinterpreted, three types of tidal-marsh-soils with different structure are described: 1 . the typical clayey tidal-marsh-soils with very various aggregate structures: The well aired and permeable “SEEMARSCH” (marine-tidal-marsh-soil) with polyhedral and prismatic structure, which is formed from the flaky “card-house” structure of marine sediments rich on salt; the densely paked “BRACKMARSCH” (brackish-tidal-marsh-soil), whose moisture is due to perched water, which coarse prismatic to columnar structure, which is formed from the mainly horizontally orientet structure of brackish sediments due to dispersion; the moderately permeable “FLUSSMARSCH” (tidal-river-marsh-soil), whose wetness is often due to groundwater, with medium to coarse prismatic structure, which is formed from the finely aggregated structure of perimarine tidal-river sediments; 2 . the tidal marsh soils poor in clay, rich in silt and very fine sand with coherent structure and low air porosity, due to a strong tendency towards puddling of the top soil by raindrops, causes the formation of “HAFTNÄSSEMARSCH” (marsh soil whose moisture is due to capillar water); 3 . the tidal-marsh-soils rich in plant remains, clay and with a high level of groundwater often extremly acid, with coherent structure, which formed the generally highly permeable “ORGANOMARSCH”. The conditions of formation of these soils and the soil parameters are discussed also.     

Zur Pedogenese und Klassifikation von Marschböden des Unterweserraumes. II. Die Bedeutung von Schwefelmetabolismus,Methanproduktion und Ca/Mg-Verhältnis für die Marschen-Klassifikation

Development and Classification of Marsh Soils from the Unterweser Region, West Germany. II. Importance of Sulfur Metabolism, Methane Production and Ca/Mg Ratio for Classifying Marsh Soils The importance of sulfur metabolism in each step of marsh soil development (Brümmer, 1968) is also confirmed for the marsh soils of the Unterweser region. Sulfur contents and sulfur fractions indicate that soil development has advanced further in brackish marshes than in marine and river marshes. The results give additional evidence that the various properties of marsh soils are only partly caused by sedimentation conditions. – The sedimentation areas (Müller, 1954) apply only to small regions. Thus, methane production predominates in the freshwater area, while sulfate reduction predominates in the marine area. Both processes occur at high rates in the brackish area. Classifying soils on the basis of the Ca/Mg ratio gives the same soil groups as Brümmers classification. Consequently, classifying the marsh soils of Niedersachsen on the basis of Ca/Mg ratio is a suitable method, if the idea that sedimentation conditions cause soil properties – especially the contents of exchangeable Ca and Mg – and the present designations of the soil groups are rejected.     

Untersuchungen zur Gibberellin- und Cytokininaktivität in verschiedenen Entwicklungsstadien der Karottenwurzel

Investigations on gibberellin and cytokinin activity in carrot roots at various developmental stages In various developmental stages of carrot plants (Daucus carota L.) different ratios of cytokinin and gibberellin activities were observed in the storage root. In the mature carrot root cytokinin activity dominates gibberellin activity. In the storage root of the carrot two gibberellin-like, one gibberellin-antagonistic and four cytokinin-like components were found. One of the gibberellin-like components exists also in bound form.     

Beitra¨ge zur allgemeinen geomorphologie der tropen und subtropen Geomorphodynamik und vegetation klimazyklische sedimentation panplain/pediplain-pediment-terrassen-treppen

Because of the high infiltration capacity in natural rain forests or dry forests, there is no essential surface runoff with soil erosion and soil dislocation. At extremely poor rain forest sites one must consider that the soil chemistry is likely to induce a natural thinning of vegetation, which will lead to moderate surface runoff and a selective removal of clay, silt and fine sand. Even smaller man-made changes will cause — because of positive feedback — a considerable decrease of infiltration, as well as a corresponding surface runoff with related soil erosion and soil dislocation. Only then the recent soil erosion may be accepted as natural and climate-specific, when vegetation analyses have proven that all layers of the vegetation are undisturbed.Frequently, man-made or climatically induced regressive successions will damage preferably shallow-rooting plants. Then trees and bushes will dominate the pollen spectrum. Older erosional phases without an extensive destruction of the vegetation can thus be hidden in pollen profiles. They can be evidenced, however, by discordances, respectively by the accumulation of fine and partly also of coarse materials.Soil sediment sequences occur in all studied areas of the tropics and subtropics. They can be mainly ascribed to climatic changes. More detailed evaluations would necessitate facies- as well as frequency-analyses of these soil sediment sequences. Layers of coarse material, which are found close to, or on steep slopes, or on level surfaces, can be related to haphazardly distributed individual events of increased surface runoff. In very flat areas with predominant dense vegetation, also individual layers of coarse material, as e.g. residual debris, or shortly transported slope- respectively pediment debris, can indicate climatic periods of distinctly disturbed vegetation.Such periods can be explained by an increased frequency of randomly distributed individual events of higher rainfall intensity. The stability of the ecosystem, which depends on the “general climate” determines the threshold value, at which these individual events (miniature catastrophes) become geomorphologically active.In the presence of extreme soil moisture even the — with regard to surface runoff — very stable rain forest ecosystem can be attacked by landslides. Secondarily, then also the surface runoff can lead to increased erosion, as e.g. by slope incision. In most cases, probably a previous weakening of the ecosystem's stability will have taken place, such as a higher biopedo-climatic aridity of the “general climate”, which in turn could lead to primarily active surface runoff.It takes, however, numerous strong individual events, not to stabilize an ecosystem by progressive succession, but to destabilize it by regressive succession, so that surface runoff and the dislocation of fine and coarse material will set in, because of repeated events of less intensive rainfall. This state of an ecosystem means geomorphodynamic activity, whereas the vegetation-stabilized ecosystem stands for geomorphodynamic stability with distinct soil development. Soils and soil sediments are thus important indicators for the reconstruction of geomorphological effects of paleoclimates on slopes without concentrated surface runoff.In dry areas, which are characterized by thinner vegetation, repeated events of higher rainfall intensity can lead to geomorphodynamic activity and to regressive succession, even without a change of the “general climate”. An increase of the amount of precipitation coupled with a decreasing rainfall intensity would provoke the opposite effect: a strengthening of the ecosystem, stronger vegetation growth, and soil development.In periods of geomorphodynamic activity slopes can be entirely flooded and eroded by surface runoff, provided there is a sufficient runoff divergence due to transported coarse materials, or, in other words, when there is a high load ratio. When the load ratio is too small, then under all climates and on all geomorphologic elements, which have been shaped essentially by surface runoff, a concentration of the runoff and incision will take place. This could be so, either because the erosion capacity under a given soil protection turns out too weak, or because of too steep slope gradients related to a given catchment area.When the incision speed of such a concentrated runoff channel exceeds the lowering speed of its base level — which is frequently the case — then the following will result: its gradient, which is determined by the erosion, will become smaller, a concave longitudinal profile will develop, and finally the transport capacity will decrease, which means an increase of the load ratio. This will in turn increase the runoff divergence, and will thus lead — on all relief elements with runoff concentration — to a channel widening by lateral erosion. This process can become accelerated, when a climatic change towards higher rainfall intensities sets in, which will in turn increase the runoff divergence. In southern Brazil runoff channels of remarkable width are noticeable, not only on valley floors of smallest catchment areas, but also on steep slopes. In both cases, the high runoff divergence can be demonstrated — either in drillings, or in natural exposures — by the occurrence of coarse materials under subsequently deposited, fine sediments.In all climatic zones, this development can proceed until the interfluves are completely eliminated by lateral erosion. Then relief elements with unconcentrated runoff will develop, or rather be restored at a lower elevation, i.e. smooth slopes, respectively smooth pediments (Abtragungsfußfla¨chen). The further development is, on the one hand, characterized by a retrogressive flattening of these relief elements, and, on the other hand, by their growth, as neighbouring forms will unite. The final morphology will be one of a huge, smooth plain with a relatively small longitudinal gradient, a panplain (CRICKMAY 1933). It will develop over every substratum, and in all climatic zones. The prerequisites for such a development are, on the one hand, at least a temporary dominance of climatic conditions with geomorphodynamic activity, and, on the other hand, a relatively smaller lowering of the base level, as compared with the slope denudation. Thus, the development of panplains is favoured by areas of long-lasting tectonic stability or subsidence, or by periods without lowering of the sea level or transgression. It is, in addition, favoured by a previous deep weathering, or by a deep weathering, which continues alternatingly in periods of geomorphodynamic stability, i.e. by the development of easily removable saprolite on all types of rock.The previous stage of relief development with individual, associated plains — the pediplain, respectively the plain-facet-mosaic (Fla¨chenfacetten-Mosaik) — depends as associated form to a great extent on the former pattern of incision. This pattern depends, on the one hand, on a tectonic and petrographic weathering-conditioned differentiation, whereas on the other hand, there are distinct differences between zones of similar climate, respectively of a similar climatic sequence.In areas of the tropical savannas with wide-spread saprolite the stages of geomorpho-dynamic activity set in with a lowering of the river levels. The plains, however, are hardly dissected. When the load ratio grows because of climato-genetic reasons, then river bluffs will turn into independent slope pedimentation steps, which migrate uphill. But this will only be so, when the base level does not incise any stronger, because of the great speed of the slope denudation, which in turn results from the presence of easily removable substratum. The pediments of adjacent catchment areas will intersect near the interfluves, thus forming a pediplain. This process will be accelerated, as soon as the river incision reaches, at least in some places, the base of the saprolite. Then, any further linear erosion will be retarded.In areas of tropical savannas without saprolite, as well as in other arid areas with dominant coarse material, the slope denudation lags behind the linear incision. Incision of the rivers and dissection of older plains will be dominant. When, because of climato-genetic reasons, the load ratio grows, then relief elements with unconcentrated surface runoff will be restored, i.e. planation by lateral erosion will set in.In many areas of the nowadays perhumid tropics, the planation results from lateral erosion. At the beginning of a stage of geomorphodynamic activity, the ecosystem must probably have been stable to a great extent. Then, starting from disturbances, and also because of a low load ratio, the surface runoff must have initiated linear incision and a deep-reaching dissection of older plains.When the load ratio grows as a result of climato-genetic reasons, then new planation surfaces will develop by means of valley-floor-pedimentation processes, as in arid zones. These planation surfaces will, however, possess a much lower gradient, as there is — because of deep weathering — less coarse material involved, which consequently requires less transport work. Finally, the retrograding flattening of the longitudinal profile will also progress much faster. The system of plains consists of a mosaic of individual planation surfaces (plain-facets, Fla¨chenfacetten), which are generally sloping in the same direction. As it is an associated form of individual planation surfaces, it can be classified as a pediplain. Whereas pediplains still developed in the course of the younger Quaternary, or, respectively, developed again at lower elevations after a dissection, there is hardly any evidence of panplain development. In large parts of the world, especially in exhoric areas, a development towards increasing relief energy has occurred. The entire development can be characterized as a development sequence from panplain to pediplain, pediment, and terrace sequence. Depending on the tectonic conditions of any analysed area, on its petrographic and weathering-conditioned differentiation, and on its climate-zone-specific properties, this development has proceeded to different degrees. On the one hand, the entire development has been conditioned by the regression of the sea level since the Cretaceous period, which, although interrupted several times by transgressions, amounted up to several hundreds of meters. The development of panplains, respectively of very flat pediplains, during the older Tertiary was certainly favoured by either slow regression, or by transgression.On the other hand, a progressive planation development is possible, because of a clustering of periods of geomorphodynamic activity with especially high load ratios, i.e. with highly intensive planation processes, and with low tendencies towards dissection. The opposite is a sequence of periods of activity with small, respectively decreasing load ratios, which will favour the development of pediment sequences, and of terraces with decreasing extensions. The latter seems to be true for the younger Quaternary, which is characterized by a sequence of climatic cycles with a low potential for planation processes.With regards to the older development one must keep in mind that relief elements, which had developed during intermediate, less intensive periods of activity, were subsequently destroyed by periods with more intensive planation processes (principle of selection by intensity / Intensita¨tsausleseprinzip). Therefore, relief elements from older periods have only survived, when they either originated from very strong periods of activity, or from a sequence of equivalent periods of activity. This fact can lead to the deception that the climatic development has proceeded to ever weaker climatic cycles. The real relief development, however, can only be explained by the interference of tectonics, changes of the sea level, and the sequence of climates. The world-wide, parallel development was, to a great extent, controlled by the last two factors. A long-term shifting of the climatic zones has accelerated the relief development towards the formation of pediment-, respectively terrace sequences. Thus, for example, the Central European Quaternary valley incision can be traced to the regression of the sea level, as well as to the climatic change, which brought forth climatic cycles with less intensive processes of slope denudation, but with high intensities of linear erosion.The extremely deep-reaching weathering on panplains, respectively on pediplains, is not regarded to be responsible for planation processes, but, on the contrary, to be the result of too weak planation processes compared to the deep-reaching weathering. Very flat pediplains, but above all the panplains with their small gradients and extreme flatness are characterized — even in periods of stability with stable ecosystems — by far-reaching ground water currents and high ground water tables. Depending on the conditions of the catchment area, extreme concentrations of iron- and aluminium oxides and silica may result, whereas calcium carbonate may be deposited in arid areas. These deposits of oxides and carbonates are distinctly different from younger oxide- and carbonate concentrations, found at steeper, better-drained sites on younger surfaces. As in the case of the deep-reaching weathering, we do not regard this to be the expression of basically different process combinations, but to be the result of the different sites, which depend to a great deal on the existing relief and the relief development.     

Untersuchungen zur gezielten 15N-Substitution und -Akkumulation in der organischen Substanz ausgewählter Dauerversuchsböden

Investigation of specific ¹⁵N-substitution and accumulation in organic matter of soil from continuous fertilizer experiments Ray grass was grown in pots with upper layer substrates of longterm fertilizer experiments and fertilized with ¹⁵N labelled ammonium sulphate for three years. The ¹⁵N-labelled harvested mass was returned into the soil at the end of each year. Using the ¹⁵N tracer technique the accumulation of N in humic and nitrogen fractions was studied. After the first year, all fractions contained ¹⁵N. In sandy soil especially easily soluble compounds were formed and accumulated with ¹⁵N. On the contrary in loamy-soils more resistant fractions marked with the isotop were increased.     

Fluoreszenzmikroskopisch bestimmte mikrobielle Biomasse und deren Beziehung zum Gesamtkohlenstoffgehalt und zur Dehydrogenaseaktivität in ausgewählten Bodenproben

Microbial biomass measured by fluorescence microscopy and its relation to total organic carbon and dehydrogenase activity in selected soil samples Techniques for direct observation of microbial biomass with epifluorescence microscopy, which have proved reliable in aquatic microbiology, were applied for investigation of soils. The procedure for measurement of microbial biomass consisted of ultrasound treatment, filtration with nuclepore-filters, registration of cell-size classes and separate counting of small bacteria. Microbial biomass of an arable A_p (Slu = silty loamy sand) was nearly twice as high with ultrasonication as with untreated samples. In 16 root-free samples removed from different mineral soils, bacterial biomass ranged from 0,22 to 7,50 mg C/g soil, surpassing fungal biomass in general by the factor 2 to 35. Up to 98% of the total organic carbon (C_org) in soil was present in microbial biomass. In uncultivated topsoils dehydrogenase activity was highly correlated with C_org and microbial biomass (n = 7, r_mult. = 0,972, α = 0,001).     

Beiträge zur Kenntnis der Vaucheriaceen XIII. Über undulierte und pseudo-undulierte Thalli beiVaucheria

Ohne Zusammenfassung     

Bodenphysikalische Untersuchungen zum Nachweis der spätpleistozänen Bodenbildung in rheinisch-westfälischen Lößgebieten

Soil physical investigations proving the late pleistocene pedogenesis in loess areas of Northrhine-Westfalia Balancing the structure of typical Braunerde- and Parabraunerde-profiles in the loess-regions of Northrhine-Westfalia soil physical investigations had confirmed that the biggest part of the solum has been clearly compacted als related to parent material. Above C-horizon there has been found a small part of Bv-horizon without compaction, characterized by distinctly increasing pore volume, especially by that of the 10–50 μm fraction, following the carbonate losses. This horizon represents an important mark in soil genesis, probably dating the border between preholozene and holozene soil forming processes. Because the disturbing effects of permafrost conditions the preholozene soil genesis is of definite importance in soil mapping and describing properties of the soils.     

Die Böden von Wallhecken in Schleswig-Holstein I. Klassifikation und Genese

Soils of Mound Hedges in Schleswig-Holstein I. Classification and Genesis In typical landscapes of Schleswig-Holstein soils of mound hedges were investigated (FAO (1989): Cumulic Anthrosol). New soils have been developed from the deposit of the mound hedge in less than 250 years. A classification with regard to the German classification of natural soils is suggested. The soil genesis from sandy deposits has reached the step of Dystric Regosols, groundwater has induced gleyic features. Soil genesis could be described chronologically, if time of deposition of these mound hedges is known. Some of the natural soils are conserved below the deposit. Pedogenesis in an area, changed by man, could be reconstructed. This is why systematic, scientific soil investigations of mound hedges may be very interesting.     

Kommentar zum Diskussionsbeitrag zur Ermittlung der effektiven Durchwurzelungstiefe für geschichtete Profile von T. Tenholtern und S. Seiffert

Tenholtern and Seiffert (this issue) improved the calculation of the effective rooting depth of laminated soils after Mueller (1197). The new procedure remains however a heigh weighting of subsoil, opposing extensive results of plant cultivation. The calculation after Schrey (1996) follows better the results from plant cultivation and should therefore be used if – with the exception of the textural composition – all factors of influence of rooting depth are sufficiently uniform. Instead of calculated root depths the following generalized values proved to be acceptable in water supply and distribution as well as in plant cultivation: 4 dm for grassland (meadow and pasture) 10 dm for arable land (without special cultures) 15 dm for forests and woodland. Viewing individual cultures the usable capacity should be calculated as sum curve in steps of one dm over the depth of profile and combined as static value to time‐dependent root growth and weather‐dependent water requirement of the culture.     

Nitrat‐Austräge auf intensiv und extensiv beweidetem Grünland,erfasst mittels Saugkerzen‐ und Nmin‐Beprobung I Einfluss der Beweidungsintensität

Nitrate leaching from intensively and extensively grazed grassland measured with suction cup samplers and sampling of soil mineral‐N I Influence of pasture management Leaching of nitrate (NO₃^—) from two differently managed cattle pastures was determined over four winters between 1993 and 1997 using ceramic suction cup samplers (with min. 34 cups ha^—1); additionally, vertical soil mineral‐N content in 0—0.9 m (N_min) was measured at the beginning and end of two winters (with min. 70 different sample cores ha^—1). The experimental site in the highlands north‐east of Cologne, Germany, is characterized by high annual precipitation (av. 1,362 mm between 1993 and 1996). An intensive continuous grazing management (1.3 ha, fertilized with 250 kg N ha^—1 yr^—1, average stocking density 4.9 LU ha^—1, = [I]) was tested against an extensive continuous grazing system (2.2 ha, av. 2.9 LU ha^—1; no N‐fertilizer but an estimated proportion of Trifolium repens up to 15 % of total dry matter in the final year, = [E]). The results can be summarized as follows: (1) Mean leaching losses of NO₃‐N, estimated from suction cup sampling and balance of drainage volume, were 85 kg NO₃‐N ha^—1 [I] and 15 kg NO₃‐N ha^—1 [E] during three wet winters with drainage volumes between 399 and 890 mm; in a dry winter with 105 mm calculated percolation, nitrate leaching decreased by a factor of 5 for both grazing treatments. (2) Although the amount of mineral N in soil (N_min) sampled in late autumn showed differences between intensive and extensive grazing, the N_min method permits no certain indication of the risk of NO₃ leaching. For example, during the winter period 1994/95 a reduction of mineral N in the soil (0—0.9 m) in both grazing treatments was found (—33 [I] / —8 [E] kg NO₃‐N ha^—1 and —26 [I] / —21 [E] kg NH₄‐N ha^—1) whereas during the winter 1996/97 an increase in almost all mean mineral N values occurred (+10 [I] / +2 [E] kg NO₃‐N ha^—1 and +10 [I] / —10 [E] kg NH₄‐N ha^—1). (3) In spite of the differences between both methods, the experiment shows that NO₃‐N leaching under extensive grazing could be reduced almost to levels close to those under mown grassland.     

EDV-gestütztes Meß- und Auswerteverfahren zur Bestimmung der ungesättigten Wasserleitfähigkeit nach der Verdunstungsmethode

A Computer-aided Measuring and Evaluation Method for the Determination of the Hydraulic Conductivity in the Unsaturated State according to the Evaporation Method Multiple methods for the determination of the unsaturated flow depend on the water content or the soil-moisture tension have been published by so far. Their major drawback is the large consumption of time for the measuring and/or for the evaluation. The here presented combination of devices for the application of the evaporation method including its software permit a faster determination of parameters and a presentation in an analytic mode.     

Pflanzenverfügbarkeit der Phosphatvorräte ackerbaulich genutzter Böden. -Langfristige Feldversuche zur Nutzbarkeit des Bodenphosphors und zur Bewertung der Bodenuntersuchung -

Availability of Phosphate Reserves in Arable Soils - Long Term Field Experiments for Assessing Soil P Reserves and Critical Soil Test Values - The objective of this work is to quantify the plant availability of soil P reserves accumulated by former fertilizer applications, the possibility of utilizing them by arable field crops and to determine critical soil test values. For this purpose several long term field experiments with large plots without replicates were initiated in 1977 on luvisols from loess (pH 6.8 – 7.4) in Lower Saxony with a sugar beet - winter wheat - winter barley/winter wheat crop rotation. Annual P applications were 0, 45, 90, 135 and 180 kg P₂O₅/ha as triple phosphate. Application of other fertilizers and plot management were according to farmer's practice. Despite of high yield levels phosphate response of plants was only 2 % at its maximum in the average of all crops in 15 years. This was confirmed by small plot experiments with four replicates placed into the large plots after 9 years, when soil P levels had been differentiated under the influence of plant P removal and P application. Herewith in agreement, shoot P concentration was found within the range generally regarded sufficient. It is therefore concluded that plant P demand has been fully satisfied by soil P reserves. Soil P test values, monitored by the P(H₂O) method of Sissingh, decreased markedly in 15 years, when no P was applied, they remained approximately constant when P application was equal to P removal and they increased when P addition was higher than P removal. Plants on a site with 4 mg P(H₂O)/L initially had severe P deficiency. Maximum yield was obtained when the soil P level was raised to 11 mg P(H₂O)/L. It is concluded that P reserves, which are often high in German arable soils, can be utilized by field crops and thus be lowered to about 10 mg P(H₂O)/L by reducing or omitting P dressings. For practical purposes it is suggested to restrict P application, if necessary at all, to the sugar beet crop in the rotation because they often respond more than small grain.