Does the strength of facilitation by nurse shrubs depend on grazing resistance of tree saplings?

Abstract

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 ...

Shrubs protect oak seedlings against ungulate browsing in temperate broadleaved forests of conservation interest: A field experiment

“…Associational resistance may occur as a result of physical traits (e.g. thorns, height and density) or through chemical unattractiveness of the neighboring plants (García and Obeso, 2003;Iason and Villalba, 2006;Vandenberghe et al, 2009). For example, browsing frequency on birch (Betula pendula) and willow (Salix sp.)…”

Morphological adaptation of a palatable plant to long-term grazing can shift interactions with an unpalatable plant from facilitative to competitive

“…While the small plants experience reduced grazing damage, they tend to have reduced competitive abilities (Briske and Anderson 1992;Hartvigsen and McNaughton 1995;Osem et al 2004;McGuire and Agrawal 2005). Therefore, when both an unpalatable species and a palatable species are adapted to grazing in different ways, competitive rather than positive, facilitative interactions between them may be increased (Baraza et al 2006;Callaway et al 2005;Suzuki and Suzuki 2011a;Vandenberghe et al 2009). Our previous study demonstrated that a palatable species adapted to grazing by expressing a dwarf phenotype experienced little effects of facilitation by a large unpalatable species (Suzuki and Suzuki 2011a, b).…”

Moss is a key nurse plant for reintroduction of the endangered herb, Primulina tabacum Hance

“…There is still much room to develop better technologies to reduce the mortality of transplants; mortality could perhaps be reduced by irrigation, fertilization, protection against fungal pathogens and insects, and the identification and use of nurse plants. Periodic introductions of nursery-grown individuals could contribute to population stability (Vandenberghe et al 2009). …”