Calcareous Alps Of Austria Research Articles

Erosion of a Jurassic ophiolitic nappe-stack as indicated by exotic components in the Lower Cretaceous Rossfeld Formation of the Northern Calcareous Alps (Austria)

Abstract The microfacies and biostratigraphy of components in mass-flow deposits from the Lower Cretaceous Rossfeld Formation of the Northern Calcareous Alps in Austria were analysed. The pebbles are classified into six groups: 1) Triassic carbonates (uppermost Werfen to basal Gutenstein Formations), 2) Upper Jurassic to lowermost Cretaceous carbonates (Oberalm Formation and Barmstein Limestone), 3) contemporaneous carbonate bioclasts (?Valanginian to ?Hauterivian), 4) siliceous pebbles (radiolarites, ophicalcites, siliceous deep-sea clays, cherts), 5) volcanic and ophiolitic rock fragments and 6) siliciclastics such as quartz-sandstones and siltstones. The radiolarites show three age groups: Ladinian to Early Carnian, Late Carnian/Norian and Late Bajocian to Callovian. The Middle Triassic radiolarites are interpreted as derived from the Meliata facies zone or from the Neotethys ocean floor, whereas the Late Triassic radiolarites give evidence of the sedimentary cover of the Neotethys ocean floor. During late Early to early Late Jurassic, the Triassic to Early/Middle Jurassic passive margin of the Neotethys attained a lower plate position and became obducted by the accreted ocean floor of the Neotethys Ocean. The accreted ocean floor was contemporaneously eroded and resedimented in different deep-water basins in front of the nappe-stack. These basin fills were subsequently incorporated in the orogen forming mélanges in this complex ophiolitic nappe-stack. The Middle Jurassic radiolarites are interpreted as the matrix of these mélanges. Together with the volcanic and ophiolitic material the siliceous rocks were eroded from this ophiolitic nappe-stack in Early Cretaceous times and brought by a fluvial system to the Rossfeld Basin within the Tirolic realm of the Northern Calcareous Alps. The different fining-upward sequences in the succession of the Lower Cretaceous Rossfeld Formation can be best explained by sea-level fluctuations and decreasing tectonic activity in the Jurassic orogen

Environmental changes across the Triassic–Jurassic boundary and coeval volcanism inferred from elemental geochemistry and mineralogy in the Kendlbachgraben section (Northern Calcareous Alps, Austria)

The end-Triassic extinction (ETE), one of the five largest Phanerozoic mass extinctions, is associated with rapid and severe environmental change, but existing data permit alternative models of causation. Volcanism in the Central Atlantic Magmatic Province (CAMP) has been proposed as the main trigger, but direct evidence for this linkage is scarce. To help constrain scenarios for the ETE and other Triassic–Jurassic boundary (TJB) events, we obtained a temporally highly resolved, multidisciplinary dataset from the Kendlbachgraben section in the Northern Calcareous Alps in Austria. The section belongs to the same paleogeographic unit (Eiberg Basin) and share similar stratigraphy with the recently selected base Jurassic Global Stratotype Section and Point at Kuhjoch.Micromineralogic study of the topmost bed of the Rhaetian Kössen Formation revealed pseudomorphs of altered, euhedral pyroxene and amphibole crystals. Their well-faceted morphology is consistent with their origin from distal mafic volcanic ash fallout. Spherical grains were also observed in the same bed, likely representing clay-altered volcanic glass. Clay minerals of this bed include low- to medium-charged smectite and Mg-vermiculite, both typical alteration products of mafic rocks. The same bed yielded a rare earth element pattern that differs from all other levels in an enrichment of heavy REEs, hinting at some minor contribution from mafic magmatic material. These features from a layer that was deposited very near to the TJB are interpreted as direct evidence of CAMP volcanism, coeval or immediately preceding the ETE and the initial negative carbon isotope anomaly.The kaolinite-dominated clay mineral spectrum of the overlying boundary mudstone records intensive weathering under hot and humid greenhouse conditions. Redox-sensitive minor and trace elements do not support the development of widespread anoxia in the studied section. Although pyrite is common in several layers, framboid size indicates formation within a reductive zone, below the sediment/water interface, rather than in an anoxic water column.Our data provide a direct link between uppermost Triassic marine strata and CAMP-derived material. They support scenarios where CAMP volcanism induced climate and other environmental change, which in turn triggered the ETE and that is also reflected in the carbon isotope anomalies.

Patch configuration affects alpine plant distribution

The relative importance of niche requirements and dispersal limitation in controlling the landscape-scale distribution of plants is still contentious. Local occurrence and abundance of alpine plants are commonly thought to be driven by abiotic site conditions due to pronounced environmental gradients over short distances. However, explicit tests of the additional role of dispersal-related processes for alpine plant distribution patterns are lacking. Here, we combine niche-based species distribution models with variables describing patch size and connectivity to evaluate if, besides abiotic limitations, spatial habitat configuration affects the occurrence and abundance of six plant species inhabiting patchy snowbed mosaics of the northeastern Calcareous Alps in Austria. Moreover, we assess if eventual effects of spatial patch configuration are more clearly detectable when calculating connectivity based on parameterized mechanistic dispersal kernels for both wind and animal vectors instead of using nearest neighbour metrics. We show that patch size and connectivity are significantly correlated to the occurrence of all and to the abundance of four out of six study species, although the relative importance of these variables, as compared to niche constraints, varies among species. In addition, connectivity measures derived from parameterized dispersal kernels were more closely related to occupancy, and in particular to abundance patterns than a simple nearest neighbour metric. The fitted kernels also suggest that dispersal by alpine chamois plays an important role for inter-patch seed exchange. We conclude that, despite evident abiotic limitations, recurrent local extinctions and delayed re-colonizations indeed play a role for the distribution of our study species, and that alpine plants may hence be less in equilibrium with their abiotic environment than commonly thought. Moreover, the relatively high long-distance dispersal probabilities of animal kernels indicate that the ability of alpine plants to adapt their ranges to a rapidly warming climate may, among other factors, depend on the availability of dispersal services by large mammals.

A false aciculariacean alga and its origin: an example from the Late Jurassic of the Northern Calcareous Alps, Austria

Slightly curved calcitic plates with marginal pores recalling an aciculariacean alga are common in Late Tithonian reefal platform margin deposits of the Plassen Carbonate Platform of the Northern Calcareous Alps of Austria. Illustrated also from the Western Carpathians, these forms were assigned to the genus Acicularia, e.g., Acicularia elongata Carozzi. It is demonstrated that these algal parts are not reproductive caps of polyphysacean algae (formerly known as acetabulariaceans), but represent sections through scattered articles fragments of the dasycladalean alga Neoteutloporella socialis (Praturlon), more precisely the proximal parts of the laterals. This alga formed reefal bushes at the platform margin near-by to coral-stromatoporoid patches. The characteristic aciculariacean algae recalling fragments occur in bioclastic packstones, a facies adjacent to these dasycladalean algal microreefs.

Acicularia? weisswasserensis n. sp. and Terquemella? microsphaera n. sp., two new Dasycladales from the Upper Cretaceous (Late Turonian-Santonian) of the Northern Calcareous Alps (Gosau Group, Austria)

Two new dasycladalean algae are described from the Gosau Group of the Northern Calcareous Alps in Austria. The tiny spicules of Acicularia? weisswasserensis n. sp. were found in foraminiferal wacke- to packstones associated with rudist limestones of the Weisswasser locality (Middle Coniacian), Lower Austria. The small globulous Terquemella? microsphaera n. sp. occurs in marls to marly limestones of the Pletzachalm locality (Upper Turonian), Tyrol, and Russbach locality (Upper Santonian), Lower Austria. The Terquemella-Acicularia group requires taxonomic revision; the two forms described herein, however, are clearly distinct from other species, and belong to the smallest representatives of these genera. In addition, Acicularia? aff. magnapora Kuss and morphologically similar forms interpreted as gametophores of unknown larger dasycladales are described.

Organic matter accumulation following Pinus mugo Turra establishment in subalpine pastures

Background: Livestock reduction or abandonment has been common on the subalpine pastures of the Northern Calcareous Alps in Austria and Germany since the mid-nineteenth century. The mosaic of Pinus mugo scrub and grassland is being increasingly recolonised by P. mugo. Aims: In this study we focus on the accumulation rate of the organic layer associated with establishment and development of Pinus mugo in non-forest plant communities. Methods: Age determination of P. mugo is used in combination with soil and existing climatic data to describe the site-dependent accumulation rates of the organic layer by using generalised linear models. Results: Mean increase of the organic layer is 12.5cm during the first 100 years. Decomposition of fresh litter is retarded in the first 30–50 years after P. mugo establishment. The residual variation of the age–depth relationship can be explained satisfactorily by using climate and habitat descriptors. Temperature, site water balance, and the presence of a clayey soil are significantly related to the depth of the organic layer. Conclusions: Organic layer accumulation after P. mugo establishment in former pastures is a long-term process exceeding the investigated period of 100–150 years. Increased needle litter input as the prime factor, together with soil properties and particular microclimatic conditions under the P. mugo canopy all contribute to controlling accumulation rates.

Mating systems of snowbed plant species of the northeastern Calcareous Alps of Austria

Predicted climate warming will likely reduce the area and increase the fragmentation of alpine snowbed habitats. The ability of snowbed plants to cope with such fragmentation will, among other things, depend on their reproductive strategy. With respect to the mating system, as a key component of reproductive strategies, the environmental conditions in arctic and alpine snowbeds have been hypothesized to select for high selfing ability due to short growing seasons and unpredictable pollinator service. In this study we evaluate whether the mating system strategies of seven typical snowbed forbs of the northeastern Calcareous Alps in Austria are in line with this hypothesis. Field-pollination experiments were conducted in order to study the effects of pollinator exclusion (bagging; all study species), emasculation and manual self- and cross-pollination (subset of study species) on seed set. Additionally, data on floral traits associated with the reproductive system such as anther and ovule numbers and pollen:ovule ratios were collected. Results demonstrate that selfing is not uncommon but by no means obligatory for snowbed plants: the study species display a wide range of mating system types, from predominately outcrossing to predominately selfing. The different reproductive strategies of regional snowbed plants are discussed in relation to their ability to cope with climate warming induced habitat fragmentation.

Interactions among tree‐line conifers: differential effects of pine on spruce and larch

Summary Plant–plant interactions are increasingly considered as complex phenomena involving both negative and positive components. Within a community, the relative importance of these components is probably species‐specific and may also vary among life‐history stages and along environmental gradients. We used the tree line of the north‐eastern Calcareous Alps of Austria, composed of shrubby Pinus mugo and upright Picea abies and Larix decidua, as a simple system in which to investigate these interactions. We focused on the largely unknown effects of pines on spruce and larch, rather than on P. mugo, which is known to be competitively displaced by the two tree species. We used regression models on observational data to analyse the responses of the trees to a gradient of pine cover in terms of recruitment, growth, fecundity and browsing damage, and to determine whether effects involved both competitive and facilitative components, if they depended on the life‐history stage of the trees and if they were species‐specific. We detected a pronounced negative effect of pine cover on recruitment and growth of both spruce and larch, whereas seed production was unaffected. Larch turned out to be more sensitive to pine competition: its recruitment and growth are superior to that of spruce in open habitats but this advantage vanishes in dense pine thickets. Contrary to expectations, the effects of pine cover on growth rates of spruce and larch did not depend on the life‐history stage of the trees. Pine cover is a major determinant of browsing damage for both spruce and larch, indicating that it does have a positive effect in providing shelter against herbivores. The differential effects of pines on spruce and larch are likely to favour spruce at the expense of larch in realizing potential habitat expansion as a result of climate change. Disregarding the complex details of plant–plant interactions may thus result in unrealistic predictions of species responses to environmental changes.

Soil nematode communities of Alpine summits–site differentiation and microclimatic influences

Nematode communities and the differences in microclimatic conditions were studied on three summits (altitude 1900–2250 m a.s.l.) in the calcareous Alps of Austria (Styria). Family composition and trophic structure (feeding types) were assessed and were analysed for (1) between-summit variation, and (2) differences between summit plots facing the four compass directions, i.e. microclimate variation. Soil temperatures were recorded at all plots. The summits differed significantly in family composition in that the lowest summit strongly deviated from the other two summits similar in altitude. Total nematode abundance and diversity were similar, however, among summits (342–444 individuals per 100 g dry soil, 18–23 families per summit). Maturity indices (3.0–3.3) and the plant parasite indices (2.4–2.6) were also within a narrow range. The most pronounced result was that nematode abundances on the south or east facing side were higher, by a factor of 4, than on the northern and western sides. This pattern applied to most families and feeding types, albeit to varying degrees. Across all summits nematode diversity and family composition were correlated with winter temperature minima. Total nematode abundance, however, covaried with annual mean temperature and growing season duration within summits. We conclude that nematode assemblages are potentially good bioindicators of climate change. They reacted sensitively and predictably to microclimatic conditions, sampling techniques are inexpensive and well standardized. Furthermore, feeding types can be determined with minimal taxonomic skills and largely reflect results based on classification by family.

Modelling climate change‐driven treeline shifts: relative effects of temperature increase, dispersal and invasibility

1 Global warming will probably shift treelines upslope in alpine areas and towards the pole in arctic environments. However, responses of regional treelines to climatic trends over the last century do not show any clear trends. We hypothesize that these equivocal responses may partly be caused by limitation of dispersal and/or recruitment that is species-specific to particular trees with potentially expanding ranges. 2 To test this hypothesis, we established and parameterized a temporally and spatially explicit model of plant spread and analysed its sensitivity to: (a) variation in predicted climatic trends; (b) the spatial distribution of recruits around a seed source; and (c) variation in the resistance of resident non-woody vegetation to invasion. We used data from a high mountain landscape of the Northern Calcareous Alps in Austria where the treeline is dominated by Pinus mugo Turra, a shrubby pine. 3 Low growth rates and long generation times, together with considerable dispersal and recruitment limitation, resulted in an overall slow range expansion under various climate-warming scenarios. 4 Running the model for 1000 years predicted that the area covered by pines will increase from 10% to between 24% and 59% of the study landscape. 5 The shape of the dispersal curve and spatial patterns of competitively controlled recruitment suppression affect range size dynamics at least as severely as does variation in assumed future mean annual temperature (between 0 °C and 2 °C above the current mean). Moreover, invasibility and shape of the dispersal curve interact with each other due to the spatial patterns of vegetation cover in the region. 6 Ambiguous transient responses of individual treeline systems may thus originate not only from variation in regional climatic trends but also from differences in species’ dispersal and recruitment behaviour and in the intensity and pattern of resistance of resident alpine vegetation to invasion.

A resampling approach for evaluating effects of pasture abandonment on subalpine plant species diversity

Abstract. The decline of species‐rich semi‐natural calcareous grasslands is a major conservation problem throughout Europe. Maintenance of traditional animal husbandry is often recommended as an important management strategy. However, results that underpin such management recommendations were derived predominantly from lowland studies and may not be easily applicable to high mountain areas. In this study we analyse the importance of traditional low‐intensity summer farming (cattle grazing) for vascular plant species diversity of a subalpine region in the northern calcareous Alps in Austria by resampling from an existing dataset on its vegetation. Results indicate a significant long term decline of plant species diversity following abandonment at the landscape scale. In contrast, within‐community effects of pasture abandonment on plant species diversity are equivocal and strongly depend on the plant community. We suppose these differences to be due to diet preferences of cattle as well as to the differential importance of competition for structuring the respective communities. From our results we infer that the main mechanism by which pasture abandonment affects vascular plant species diversity, at least during the first ca. 100 yr documented here, are not local‐scale competitive exclusion processes within persisting communities. Instead, post‐abandonment successional community displacements that cause a landscape scale homogenization of the vegetation cover seem to be primarily responsible for a decline of species diversity. We conclude, that successful management of vascular plant species diversity in subalpine regions of the Northeastern Calcareous Alps will depend on the maintenance of large scale pasture systems with a spatially variable disturbance regime.

A resampling approach for evaluating effects of pasture abandonment on subalpine plant species diversity

Abstract. The decline of species-rich semi-natural calcareous grasslands is a major conservation problem throughout Europe. Maintenance of traditional animal husbandry is often recommended as an important management strategy. However, results that underpin such management recommendations were derived predominantly from lowland studies and may not be easily applicable to high mountain areas. In this study we analyse the importance of traditional low-intensity summer farming (cattle grazing) for vascular plant species diversity of a subalpine region in the northern calcareous Alps in Austria by resampling from an existing dataset on its vegetation. Results indicate a significant long term decline of plant species diversity following abandonment at the landscape scale. In contrast, within-community effects of pasture abandonment on plant species diversity are equivocal and strongly depend on the plant community. We suppose these differences to be due to diet preferences of cattle as well as to the differential importance of competition for structuring the respective communities. From our results we infer that the main mechanism by which pasture abandonment affects vascular plant species diversity, at least during the first ca. 100 yr documented here, are not local-scale competitive exclusion processes within persisting communities. Instead, post-abandonment successional community displacements that cause a landscape scale homogenization of the vegetation cover seem to be primarily responsible for a decline of species diversity. We conclude, that successful management of vascular plant species diversity in subalpine regions of the Northeastern Calcareous Alps will depend on the maintenance of large scale pasture systems with a spatially variable disturbance regime.

NITROGEN LEACHING FROM FOREST SOIL CORES AFTER AMENDING ORGANIC RECYCLING PRODUCTS AND FERTILIZERS

Many alpine forests are severely depleted of nutrients by extensive logging and by grazing of cattle and wildlife. Fertilization may be a remedy, but nitrate leaching may pose problems for the groundwater. However, use of slow-release fertilizers may avoid this problem, whilst improving the Ca, Mg, K, and P status of these soils. Intact soil cores (11 cm diameter, 40 cm depth) from a mixed forest and a Norway spruce stand in the Northern Calcareous Alps of Austria were used in a laboratory experiment to study the effects of adding organic fertilizers and recycling products on patterns of nitrate and ammonium release. The amended (corresponding to 300 kg N ha−1) and control cores were incubated for 29 weeks at 15°C. Soil water (retrieved 5 cm below the soil surface) and leachate were analysed for nitrate and ammonium in regular intervals. After the incubation, soil microbial biomass, basal respiration and nitrogen mineralization were determined. Some of the organic fertilizers, especially those that had undergone composting processes (compost of organic waste, compost of bark+sewage sludge, compost of sawdust+sewage sludge, Biovin®) and Biosol®, caused only minor increases of nitrate and ammonium in the soil water and leachate. Others, like uncomposted sewage sludge products (Primafert® and sewage sludge+shale), resulted in elevated (up to 150 mg nitrate-N l−1) nitrate concentrations in the soil water and in the leachate. Fertilization with N-rich fertilizers (Biosol®, Primafert®, sewage sludge+shale) resulted in significant decreases in microbial biomass and basal respiration at the end of the 6-month incubation. Microbial biomass and basal respiration were not affected by the other organic fertilizers.

Effects of forest fertilization on nitrogen leaching and soil microbial properties in the Northern Calcareous Alps of Austria

Several boreal and alpine forests are depleted in nutrients due to acidification. Fertilization may be a remedy, but rapidly-soluble salts (N, P, K, Mg) may pose nitrate problems for the groundwater or decrease microbial activity. With the aim to investigate potential nitrogen leaching after fertilization we set up an experiment employing intact soil cores (11 cm diameter, 20–40 cm long) from a mixed forest and a Picea abies stand (soil type Rendsina) in the Northern Calcareous Alps of Austria. The cores were fertilized with a commercial NPK fertilizer or a methylene-urea-apatite-biotite (MuAB) fertilizer at a rate corresponding to 300 kg N ha-1 and incubated for 28 weeks together with unfertilized controls. Both soil water (retrieved 5 cm below the soil surface) and leachate were analyzed for nitrate and ammonium in regular intervals. After the incubation, soil microbial biomass and basal repiration were determined and a nitrogen mineralization assay was performed. For the control, in the soil water and leachate maximum NH4 + and NO3 - concentrations of 5 and 11 mg N L-1, respectively, were found. Compared to that, MuAB fertilizer resulted in a slow increase of NH4 + and NO3 - in the soil water (up to 11 and 35 mg N L-1 respectively) and in the leachate (4 mg NH4 +-N L-1 and 44 mg NO3 --N L-1). Highest nitrogen loads were found for the fast release NPK fertilizer, with NH4 + and NO3 - concentrations up to 170 and 270 mg N L-1, respectively, in the soil water. NH4 +-N levels in the leachate remained below 5, while NO3-N levels were up to 190 mg L-1. Fast- release NPK caused a significant decrease of microbial biomass and basal respiration. These parameters were not affected by MuAB fertilizer. The results suggest that the MuAB fertilizer may be an ecologically appropriate alternative to fast-release mineral fertilizers for improving forest soils.