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 tim

Ungulate browsing in winter reduces the growth of Fraxinus and Acer saplings in subsequent unbrowsed years

ISSN:1385-0237ISSN:1573-505

Timing, light availability and vigour determine the response of Abies alba saplings to leader shoot browsing

ISSN:1612-4677ISSN:1612-466

Predicting decay and ground vegetation development in Picea abies snag stands

ISSN:1385-0237ISSN:1573-505

Browsing regime and growth response of Abies alba saplings planted along light gradients

Silver fir is a highly desirable species in European mountain forests from a management and conservation point of view, but it is also highly palatable for ungulates. We planted Abies alba saplings along natural light gradients to explore under natural browsing: (1) the light conditions under which saplings grow best in the absence of browsing; (2) when and by which ungulate species which saplings are browsed; and (3) under which conditions saplings react most vigorously to browsing. The experiment was carried out in a Swiss forest using four fenced plots each containing about 30 saplings planted in 2001, which were between 17 and 100 cm tall in 2009. For half of the saplings, browsing was allowed and filmed from April 2009 to January 2010. Saplings grew better with more light (13 % rather than 10 % canopy openness). Browsing was not a single event per sapling but a continuous process during the winter months. Almost all saplings exposed to browsing suffered heavy browsing by chamois and red deer, but no roe deer browsing was observed. The remainder of the browsed shoots were longer and contained more buds under 13 % canopy openness. The browsing-induced height differences between browsed and unbrowsed trees increased over time under all light conditions, and almost no diameter growth was measured in the years after browsing. In cases with severe browsing, management aimed at letting in more light does not lead to a substantially better tolerance of browsing. We thus recommend integrating the “feeding strength” in the assessment of browsing.ISSN:1612-4677ISSN:1612-466

Dispersal and microsite limitation in an abandoned calcareous grassland of the southern prealps

Dispersal limitation is often involved when the species composition of a dry abandoned grassland shows a slow response to resumed regular mowing. A seed-addition experiment, using 32 species which do not belong to the local species pool, was performed on Monte San Giorgio (southern Switzerland) to test whether the low recruitment success was due to dispersal limitation or due to unfavourable microsite conditions. In October 1997, 20 species were individually sown in six 3 × 4 m blocks of a 2 × 2 factorial “partial” split-plot design with treatments of abandonment vs. mowing and undisturbed vs. root-removed soil, this last being applied in small naturally-degradable pots. Moreover, 12 species were sown only in the treatments on undisturbed soil. Seedlings of sown and spontaneously germinating seeds were observed on 16 occasions over one 12-month period. Seeds of 31 out of the 32 species germinated. Twenty-four species showed germination rates higher than 5% and different seasonal germination patterns. Established vegetation, especially the tussocks ofMolinia arundinacea, reduced the quality of microsites for germination. Whereas a few species germinated better under the litter ofMolinia arundinacea, many more germinated better under the more variable microsite conditions of a mown grassland. Only a few seedlings of 25 species out of the 31 germinated species survived until October 1998. Seedling survival was negatively affected by litter, unfavourable weather conditions (frost and dry periods followed by heavy rains) and herbivory (slugs and grasshoppers). Tussocks ofMolinia arundinacea, however, tended to protect seedlings. The poor establishment success of “new” species observed in abandoned meadows on Monte San Giorgio after resumed mowing is due to dispersal and microsite limitations

Dispersal and microsite limitation in an abandoned calcareous grassland of the southern prealps. Folia Geobotanica

Abstract: Dispersal limitation is often involved when the species composition of a dry abandoned grassland shows a slow response to resumed regular mowing. A seed-addition experiment, using 32 species which do not belong to the local species pool, was performed on Monte San Giorgio (southern Switzerland) to test whether the low recruitment success was due to dispersal limitation or due to unfavourable microsite conditions. In October t997, 20 species were individually sown in six 3 x 4 m blocks of a 2 x 2 factorial "partial" split-plot design with treatments of abandonment vs. mowing and undisturbed vs. root-removed soil, this last being applied in small naturally-degradable pots. Moreover, 12 species were sown only in the treatments on undisturbed soil. Seedlings of sown and spontaneously germinating seeds were observed on 16 occasions over one 12-month period. Seeds of 31 out of the 32 species germinated. Twenty-four species showed germination rates higher than 5% and different seasonal germination patterns. Established vegetation, especially the tussocks of Molinia arundinacea, reduced the quality of microsites for germination. Whereas a few species germinated better under the litter of Molinia arundinacea, many more germinated better under the more variable microsite conditions of a mown grassland. Only a few seedlings of 25 species out of the 31 germinated species survived until October 1998. Seedling survival was negatively affected by litter, unfavourable weather conditions (frost and dry periods followed by heavy rains) and herbivory (slugs and grasshoppers). Tussocks of Molinia arundinacea, however, tended to protect seedlings. The poor establishment success of "new" species observed in abandoned meadows .on Monte San Giorgio after resumed mowing is due to dispersal and microsite limitations