Tree growth is generally limited by temperature in cold climates and by water availability in arid zones. Establishment in altitudinal treeline ecotones depends on the temperature, but may be very sensitive to water availability as well. We studied the effect of climate and land use on the colonization and growth of Pinus cembra in the treeline ecotone of the dry Central Swiss Alps; one site was influenced by timber harvest and cattle activity and another one was undisturbed. Stands were sampled at three elevations: in the forest and the lower and upper parts of the treeline ecotone. The age structure was similar in all sites, ranging from uneven-aged (forest) to more even-aged, with recent densification and upslope expansion of the treeline ecotone. However, recruitment started at the treeline around 1850 (the end of the Little Ice Age) in the undisturbed site, simultaneously with an increase of tree-ring growth, but about 60 years later at the other site, after cattle grazing decreased. These results, and the positive correlation of radial growth with summer and previous autumn temperatures indicated that, in this altitudinal treeline ecotone, growth and establishment are mainly linked to temperature. However, drought stress was visible in the lowest stands, with a positive correlation of growth with rainfall during the previous autumn and December, and in August of the growing season. This could limit growth in a future warmer climate.

Browsing by livestock has been identified as an important factor preventing tree regeneration in wooded pastures. Two field experiments were performed to investigate the effects of cattle browsing on tree sapling growth in a mountainwooded pasture. Two size classes (ca. 12-17 cm and 41-59 cm) of each of 4 species (Picea abies, Abies alba, Acer pseudoplatanus and Fagus sylvatica) were exposed to zero, low and high grazing intensities. We measured the proportion of saplings browsed and the effect of browsing on growth. A mowing treatment within the zero grazing intensity treatment showed no significant effect on sapling growth. One percent of the large saplings but 25% of the small saplings escaped browsing. Saplings were better protected when surrounded by taller vegetation. The proportion of saplings browsed was not significantly different among species although evergreen tree saplings lost a larger proportion of biomass than deciduous species when browsed. Under grazing, average current-year shoot production and total aboveground biomass of all species were significantly reduced. Browsing effects tended to be smaller at the lower grazing intensity. Because the deciduous species were least reduced in aboveground growth, especially under the low grazing intensity, we conclude that at least in short-term, deciduous species are less affected by cattle browsing.

A description of bog pine stands (Pinus uncinata Ramond var. rotundata (Link) Antoine) on uncut oligotrophic mires affected by drainage and nearby peat cuttings at three sites of the Jura Mountains (Switzerland) is given. In all sites, three situations were chosen: (i) central parts of the bogs, (ii) surfaces near cutting walls and bog margins, and (iii) intermediate situations. Population structures were characteristic for each situation. In the open and wet central parts of the bogs, trees were scattered, small, and uneven aged. In the intermediate situations, tree density was higher, and the stand was multilayered with taller and uneven-aged individuals. Near the edges of the bogs or close to the peat cutting walls, the trees were tall, even-aged, and younger with a high growth rate. The nonsynchronous colonization of the bog pine trees on the three sites indicates that local factors such as drainage and peat cuttings in the vicinity of the uncut surfaces were more influential than climate factors. Radial growth patterns, very similar between the sites and the various pinewood stands, and the numerous common pointer years reflect local and regional climate fluctuations. The pinewood development on uncut bogs in the Jura Mountains thus represents a recent dynamics, which is strongly linked to human activities.

Facilitation of tree regeneration by nurse shrubs that offer protection against large herbivores is an important driver of wood-pasture dynamics. Here we asked whether the response to facilitation by nurse shrubs depends on the grazing resistance of the prote´ge´saplings. We experimentally tested the protective effects of the thorny Rosa rubiginosa on browsing frequency, survival, and biomass change of saplings of two species-groups, presumably differing in grazing resistance: the coniferous Abies alba and Picea abies and the deciduous Acer pseudoplatanus and Fagus sylvatica saplings. The saplings were planted under and outside (1.5 m) planted nurse shrubs, under zero, low and high grazing intensity. In total, 1920 young saplings were transplanted to 60 blocks and followed for 1 year.Although the number of saplings browsed did not differ between species-groups, the coniferous saplings showed lower resistance to cattle browsing (i.e. lower survival and growth rates) than the deciduous saplings. The less resistant coniferous saplings benefited significantly more from nurse shrubs than the more resistant deciduous species in terms of growth of the surviving saplings, but not in terms of overall survival. This was likely due to herbivory on the nurse shrubs causing incidental browsing on prote´ge´saplings and differences in biomass off-take. At high grazing intensity facilitative effects of the nurse shrubs decreased, especially for the coniferous species.These results have important management implications for the endangered wood-pastures in Western Europe. For a sustainable management and conservation that allows tree recruitment, grazing intensity should remain low to best promote facilitation processes for all tree species, but in particular for the less resistant conifer saplings. die Fo¨rderung durch Ammengebu¨sch von der Beweidungsresistenz der geschu¨tzten Scho¨sslinge abha¨ngt. Wir untersuchten den schu¨tzenden Effekt der dornigen Rosa rubiginosa auf die Beweidungsfrequenz, die Ü berlebensrate und die Vera¨nderungen in der Biomasse fu¨r Scho¨sslinge aus zwei Artengruppen experimentell, von denen wir annehmen, dass sie sich in der Beweidungsresistenz unterscheiden: die Nadelba¨ume Abies alba und Picea abies und die Laubba¨ume Acer pseudoplatanus und Fagus sylvatica. Die Scho¨sslinge wurden unter die und außerhalb (1,5 m) der gepflanzten Ammengebu¨sche bei fehlender Beweidung, geringer und hoher Beweidungsintensita¨t gepflanzt. Insgesamt wurden 1920 junge Scho¨sslinge in 60 Blo¨cken verpflanzt und u¨ber ein Jahr beobachtet. Obwohl sich die Anzahl der beweideten Scho¨sslinge nicht zwischen den Artengruppen unterschied, zeigten die Nadelbaumscho¨sslinge eine geringere Resistenz gegenu¨ber der Rinderbeweidung (d. h. geringere Ü berlebens-und Wachstumsraten) als die Laubbaumscho¨sslinge. Die weniger resistenten Nadelbaumscho¨sslinge profitierten signifikant mehr von den Ammengebu¨schen als die resistenteren Laubbaumscho¨sslinge in Bezug auf das Wachstum der u¨berlebenden Scho¨sslinge, aber nicht in Bezug ...