Montane Level Research Articles

Particularities of Grey Alder (Alnus incana) Stands in Riparian Galleries Along Streams of the Southern Transylvanian Tableland (Romania)

Abstract Grey Alder (Alnus incana (L.) Moench.) stands are distributed in the Carpathian area on alluvial deposits with sediments of different grain size as galleries along rivers and streams of the sub-montane to the middle montane level. The geological structure (Tertiary sedimentary deposits) in relation to the hydromorphological processes is the base for the structure of the stream valleys, which are in part very deep. Under the special microclimate of these deeper stream stretches with lower temperatures there are favourable conditions for the development of grey alder stands.

Analyse phytosociologique et phytoécologique des formations forestières à pin laricio de Corse (Pinus nigra J.F. Arnold subsp. laricio Maire) / Phytosociological and phytoecological survey of Corsican Pine forests

This phytosociological and phytoecological study considers the whole Corsican Pine (Pinus nigra J. F. Arnold subsp. laricio Maire) forest formations of the upper mesomediterranean to the alpine and subalpine levels. Bibliographical survey since the XIXth century, confronted with 2018 floristic-ecological analyses allows us to highlight the already described syntaxa status and to describe their internal variations. Three new sub-associations have been described at the supramediterranean level, and three others at the montane level. A new plant association is proposed at the mesomediterranean level. The respective place of the Corsican Pine and Beech is discussed as well as conservation issues of the Corsican Pine as an emblematic species for Corsica.

Composición vegetal de la estación biológica de la UCM ‘Finca de Ontalba’

Se ha llevado a cabo un estudio sobre la vegetación de la recientemente designada Estación Biológica Complutense ‘Finca de Ontalba’, localizada en la Sierra de Guadarrama (N Madrid). Identificamos 12 comunidades vegetales agrupadas en siete grandes tipos de vegetación: 1) Comunidades higrófilas y acuáticas; 2) Prados; 3) Comunidad pionera de suelos alterados; 4) Vegetación herbácea nitrófila de líndero de bosque; 5) Vegetación herbácea de lindero de bosque; 6) Comunidad arbustiva de orla de bosque; y 7) Vegetación forestal. Se señala el interés de la Estación para trabajos de investigación. Su campo de aplicación incluye sucesión primaria, ambientes anfibios, gradientes de humedad del suelo, ecotonos, y ambientes forestales. La Estación Biológica alberga, además, un tipo de hábitat listado en la Directiva 92/43/CEE que corresponde a cursos de agua de llanura o montanos con vegetación de Ranunculion fluitantis y Callitricho-Batrachion (hábitat 3260).

Humus Components and Soil Biogenic Structures in Norway Spruce Ecosystems

Whether the structure of Oa and A horizons varies according to animal activity is still a matter of conjecture, especially in amphi, a humus form with mixed features of mull and moder, which has been described in environments with strong seasonal contrasts. The Oa and A horizons of spruce [Picea abies(L.) Karst.] coniferous forests of the Province of Trento (Italy) were sampled in six sites with a total of 134 humus profiles along transect lines, embracing the variety of parent rocks, climate, and vegetation conditions that prevail at the upper montane level in this region. The distribution of humus components (plant debris, roots, animal feces, minerals) was assessed by an optical method and analyzed with correspondence analysis (CA). Moder humus forms were characterized by enchytraeid activity, with concomitant deposition of organic and mineral‐organic feces in Oa and A horizons, respectively. Conversely, amphis were characterized by the concomitant deposition of organic and mineral‐organic earthworm feces in Oa and A horizons, respectively. We conclude that Oa and A horizons of moders and amphis differed only quantitatively in the content of mineral matter in animal feces. The fine‐grained mineral‐organic structure that is mostly found in the A horizon of amphis results from the alimentary activity of small epigeic earthworms that mix organic matter with mineral matter, like anecic earthworms do in mulls.

Predicting tree regeneration in Picea abies snag stands

A bark beetle (Ips typographus) infestation caused the death of almost all Norway spruce (Picea abies) trees in a mountain forest in the Swiss Alps. We developed a tree regeneration model, ‘RegSnag’ (=REGeneration in a SNAG stand), to project the future amount and height of tree regeneration in these snag stands. The model combines a height-class structured tree module with a microsite-based module of snag decay and ground-vegetation succession. Microsite-specific rates of germination, mortality and height growth were modelled for four tree species (Picea abies, Sorbus aucuparia, Acer pseudoplatanus and Betula pendula) in eight height classes (from seedlings to saplings 5 m tall) and on 26 microsite types (e.g. moss, grass). Model tests with independent field data from 8 years after the Picea die-back demonstrated that microsites had a considerable effect on the development of tree regeneration on both the montane and the subalpine level. With microsite-specific parameters, the height and frequency of Picea in each microsite could be simulated more accurately than without considering microsite effects (e.g. bias of 8 vs. 119 saplings ha−1 on the montane level). Results of simulations 40 years into the future suggest that about 330–930 Picea saplings per ha out of those that germinated in 1994 and 1996 will reach a height of 5 m within 30–35 years after Picea die-back. This is due to differences in seed inflow and browsing intensities. Picea and not Betula or Sorbus trees will replace the current herbaceous vegetation in these snag stands.

Predicting decay and ground vegetation development in Picea abies snag stands

In a Picea abies (L.) Karst. (Norway spruce) mountain forest on the Gandberg site in the northern Swiss Alps, trees were killed by bark beetles in 1992–1997. A combination of field studies and dynamic modelling was used to project snag decay and future ground vegetation succession in these steep, unharvested stands. In permanent plots, ground vegetation cover and natural tree regeneration have been monitored annually since 1994. To obtain additional information on the abundance of snags, logs, boulders and other microsite types in these stands, the relative frequency of the microsite types was quantified along four strip transects on the montane and subalpine elevational levels. A dynamic model of snag decay and ground vegetation development was constructed (modified matrix model approach). Based on field data and literature values, the model was parameterised and initialised separately for the montane and the subalpine level. For model validation, microsite types were quantified in 2001 with the line-intercept method on both elevational levels. Starting from the conditions in the stands before the bark beetle attacks, it was possible to project short-term succession and to accurately simulate the decay and ground vegetation patterns eight years after tree die-back. Long-term simulations suggest that on the montane level, raspberries (Rubus idaeus L.) will be replaced by Picea abies, while on the subalpine level ferns will dominate for a long time.

Effect of microsites, logs and ungulate browsing on Picea abies regeneration in a mountain forest

Browsing by ungulates is often reported as one of the major hazards for tree regeneration, e.g. in sites disturbed by windthrow and bark beetles. As tree regeneration in mountain forests is typically concentrated on suitable microsite types, the question arises how browsing is distributed in snag stands (e.g. in standing dead Norway spruce stands), i.e. if browsing is reduced or even impeded in some microsites. Furthermore, we wanted to determine whether logs could be considered as obstacles for ungulates, and thus whether they could protect tree regeneration. The distribution of Picea abies saplings and the impact of browsing were investigated in snag stands on the Gandberg in the Swiss Alps. The frequency of microsite types was assessed along 128 m× 10 m long lines on four elevational levels. Around these lines, in 2 m wide strip transects the height and shoot lengths of P. abies saplings were measured, and the microsite type on which they occurred was noted together with the distance to the next log, and damage due to browsing. Microsite types had a large influence on the abundance of P. abies saplings on the snag stands in the Gandberg mountain forests, i.e. the following microsite types had, in comparison to their occurrence, disproportionately many P. abies saplings: coarse woody debris, roots and boulders covered with mosses on the subalpine level, and on the montane level Polytrichum and Hylocomium cushions, and moss covered by Rubus idaeus. In contrast, sites with ferns, grasses and dense Rubus cover were poorly regenerated. Browsing was higher on the montane than on the subalpine level, regardless of the microsite types and the proximity of logs. Shrubs and logs did not reduce the browsing intensity. In contrast, more Picea saplings were browsed close or under logs than far away from logs on the montane level. Hence, logs cannot be considered as obstacles for chamois in these snag stands.

Simulating radiation distribution in a heterogeneous Norway spruce forest on a slope

Simulating the dynamics of heterogeneous forests calls for spatially explicit radiation transmission models at the scale of individual trees and requiring only a short computing time. Such a model was developed for spatially heterogeneous coniferous forest canopies. Based on the interception of light rays by parabolic crowns, it simultaneously calculates the radiation intercepted by each tree and the distribution of irradiance on the ground. For every sky direction, parallel rays aim at ground cell centres and are intercepted by tree crowns on their way. Slope and exposure are taken into account eliminating rays coming from above the slope. Optimisation in computing time is obtained by pre-selecting for each ray direction a rectangular cell neighbourhood around the target cell in such a way that potentially intercepting trees can only be found in this neighbourhood. Model evaluation was done by comparing hemispherical photographs with model predictions in a spatially heterogeneous Norway spruce ( Picea abies, L. Karst) stand at the upper montane level in the Alps. Thanks to a satisfactory fit between model and data and a reasonably short computing time (about 2 min for 0.25 ha), the model can be considered for integration into a forest dynamics simulator. In the reference stand, 42% of incident radiation was intercepted by the highest trees (132 ha −1). Due to the clumped structure, 23% of incident radiation reached the soil. Interception by individual trees varied considerably as a function of tree size and location (from 0 to 60% of the potential interception of a tree growing in isolation). Irradiance at ground level was also extremely variable (between 0 and 50% of irradiance above the canopy), illustrating the need for spatial models in heterogeneous stands. The interception of radiation by trees was not affected by slope and exposure, unlike irradiance at ground level, which increased for southern exposures. Therefore, in terms of dynamics, regeneration should be the most sensitive to changes in these factors. Because the model produces precise radiation values at the ecosystem level, it allows analysis of the links between the structure of a forest stand and its energetic functioning synthetically.

Importance of secondary habitats and need for ecological management for the conservation of Diphasiastrum tristachyum (Lycopodiaceae, Pteridophyta) in the Vosges Mountains (France)

Diphasiastrum tristachyum, which is a rare Pteridophyte under national protection in France, has been discovered in several places in the Vosges Mountains during the last two decades. With its 20 currently existing populations in these mountains, it appears to be the Diphasiastrum species with the largest current distribution in the Vosges. This species mainly occurs on Vosgian sandstone substrate, in northern or northeastern exposures up to 600 m a.s.l., corresponding to the lower and middle montane levels in the Vosges Mountains. The main habitat (16 sites) are forest track borders. Only in single cases could D. tristachyum be found in other habitats such as a skiing track, a heath submitted to regular fire, an abandoned quarry and a limit of a forest plantation weeded with herbicides. All of these sites are secondary places of young anthropic origin. No really natural and primary habitats of D. tristachyum in the Vosges Mountains could be found. All localities show fragments or beginnings of heath communities belonging to the Genistion alliance. Because of the progressive succession of these communities towards forests if no human regulation occurs, D. tristachyum may have only ephemeral existence in such secondary Vosgian sites. This shows the need for a conservation and management programme which comprises measures like keeping open growing sites by the removal of invading trees, controlled pruning of dwarf shrubs and removal of the soil vegetation and the humus layer. A long-term stabilisation of the Vosgian populations of D. tristachyum may only be possible in this way.

The influence of altitude on the distribution of subterranean organs and humus components in Vaccinium myrtillus carpets

Abstract. Humus profiles were sampled along an altitudinal gradient in the Macot‐La‐Plagne Forest (France, northern Alps) to investigate variation occurring under carpets of Vaccinium myrtillus present within Picea abies forests. The vertical distribution of subterranean organs of V. myrtillus was compared with (1) that of P. abies roots and other accompanying vegetation and (2) other components of humus profiles, in particular humified organic matter mainly consisting of animal faeces. It was shown that V. myrtillus roots were mostly concentrated in mineral horizons, while P. abies roots and V. myrtillus rhizomes occupied litter horizons. This was interpreted in terms of competition for nutrient capture between P. abies and V. myrtillus. The effects of altitude were (1) a change in the vegetation accompanying V. myrtillus in dense V. myrtillus carpets, bryophytes at the montane level being replaced by forbs at the sub‐alpine level and (2) a decrease in the thickness of ecto‐organic horizons. This was interpreted as a shift from a moder system characterized by recalcitrant litter (moss) processed by an active faunal community (stabilized in the form of animal faeces) to a mor system characterized by low animal abundance but with litter of better quality which is easily leached in the absence of prominent faunal activity.

The influence of altitude on the distribution of subterranean organs and humus components in Vaccinium myrtillus carpets

Humus profiles were sampled along an altitudinal gradient in the Macot-La-Plagne Forest (France, northern Alps) to investigate variation occurring under carpets of Vaccinium myrtillus present within Picea abies forests. The vertical distribution of subterranean organs of V. myrtillus was compared with (1) that of P. abies roots and other accompany- ing vegetation and (2) other components of humus profiles, in particular humified organic matter mainly consisting of ani- mal faeces. It was shown that V. myrtillus roots were mostly concentrated in mineral horizons, while P. abies roots and V. myrtillus rhizomes occupied litter horizons. This was inter- preted in terms of competition for nutrient capture between P. abies and V. myrtillus. The effects of altitude were (1) a change in the vegetation accompanying V. myrtillus in dense V. myrtillus carpets, bryophytes at the montane level being replaced by forbs at the sub-alpine level and (2) a decrease in the thickness of ecto-organic horizons. This was interpreted as a shift from a moder system characterized by recalcitrant litter (moss) processed by an active faunal community (stabilized in the form of animal faeces) to a mor system characterized by low animal abundance but with litter of better quality which is easily leached in the absence of prominent faunal activity.

Altitudinal changes in humus form dynamics in a spruce forest at the montane level

An altitudinal transect was studied at the montane level in a spruce forest, in order to describe changes in humus form dynamics. Whatever the elevation, the periodicity of humus form changes is copied on forest dynamics. Spruce regeneration is restricted both in space and time to favourable micro-site conditions accompanying tree fall gaps. One of these conditions is a shift from moder to mull humus form. As a result, this forest ecosystem shows a space-time mosaic pattern. The recovery of mull humus form takes more time as elevation increases and thus the ratio mull:moder progressively decreases. Simultaneously, burrowing earthworms become scarce. Nevertheless mull humus form does not change basically at increased elevation. On the other hand, moder has little organic matter at the lower montane level. At the mid montane level, accumulation of holorganic faeces into OH horizon is maximum. A mor-moder (few faunal traces) is observed during tree growth phase at the upper montane level. Lack of nutrient availability was hypothesized to explain the observed shift from mull to moder or mor-moder during the phase of intense tree growth. An increased independancy between the building of a moder humus profile and the actual accumulation of organic matter was the main change occurring with elevation. The transition to the subalpine level may thus be defined as the highest elevation up to which the forest ecosystem is able to reverse the mor-building process produced by tree growth. The discoupling between primary producers, plant debris accumulation and decomposers observed in the subalpine spruce forest leads to a breaking point in the carrying capability of humus for spruce seedlings. At high elevation spruce seedlings are mainly observed on rotten wood.