Seed survival on experimental dishes in a central European old‐growth mixed‐species forest – effects of predator guilds, tree masting and small mammal population dynamics

Abstract

Predation of tree seeds can be a major factor structuring plant communities. We present a three year study on tree seed survival on experimental dishes in an old-growth forest in central Europe in Austria. We addressed species specifi c, spatial and temporal aspects of post-dispersal seed predation. Seeds of Norway spruce Picea abies , European beech Fagus sylvatica , and silver fi r Abies alba were exposed on dishes in diff erent types of exclosures which allowed access only to specifi c guilds of seed predators. Removal experiments were carried out in two old-growth forests and a managed forest (macro-sites), including micro-sites with and without cover of ground vegetation. We conducted the experiment in three consecutive years with a mast year of beech and spruce before the fi rst year of the study. Th e seed removal experiments were combined with live trapping of small mammals being potential seed predators. Our experiments showed a distinctly diff erent impact of diff erent predator guilds on seed survival on the dishes with highest removal rates of seeds from dishes accessible for small mammals. We observed diff ering preferences of small mammals for the diff erent tree species. Seed survival in different macro-and micro-habitats were highly variable with lower seed survival in old growth forests. In contrast to our assumption, and in contrast to the satiation hypothesis which assumes higher seed survival in and directly after mast years, seed survival was lower in the year following the mast year of beech when a population peak of small mammals occurred and higher in intermast periods when subsequently small mammal population crashed. Th is suggests a higher importance of sporadic masting shortly after mast years in intermast periods for establishment of forest trees provided that pollination effi ciency is high enough in such years. Combined with the high seed mortality observed after the mast year, this corroborates the important role of seed predation for forest dynamics. An altered synchrony or asynchrony of masting of diff erent tree species and changed masting frequencies through climate change may thus lead to strong and non-linear eff ects on forest dynamics.

The synchronicity of masting and intermediate severity fire effects favors beech recruitment

“…Observed mean cupules (468 ±40 m -2 ) and seed (500 ±44 m -2 ) abundance in the intermediate and low fire severity were within the range of the unburnt sites. In addition, they were also consistent with reported production in mast years of European beech forests not affected by fire (Nilsson, 1985;Nilsson and Wastljung, 1987;Topoliantz and Ponge, 2000;Overgaard et al, 2007;Olesen and Madsen, 2008;Nopp-Mayr et al, 2012;Silva et al, 2012). Beech trees do not display traits of active fire resistance, such as a thick bark.…”

Challenges and science-based implications for modern management and conservation of European ungulate populations

“…The maintenance of sustainable wild, native ungulate populations is thus an important mechanism in both the conservation and restoration of forest ecosystems. However, many interacting factors affect forest composition besides browsing, and successful germination, survival and growth of seedlings are also influenced by seed predation, competition within and between tree species and weather conditions (Kuijper et al 2010;Nopp-Mayr et al 2012, Cailleret et al 2014, Leonardsson et al 2015. Effective and scientifically sound management of well-integrated ungulate-forest ecosystems should be based on inferences from welldesigned research and monitoring.…”

The effect of population density on gene flow between adult trees and the seedling bank in Abies alba Mill.

“…Gene transmission between the parent generation and its progeny is also strongly influenced by natural selection and environmental filtering. The reproductive success of adult individuals depends greatly on the coincidence of their seed crop years with the occurrence of disturbing events reducing canopy density (Beaudet et al 2007;Bladé and Vallejo 2008), environmental heterogeneity (Snyder and Chesson 2004;Buck and Clair 2014), and the dynamics of biotic factors affecting progeny survival (Nopp-Mayr et al 2012;Paluch and Stępniewska 2012). These factors could, by narrowing the recruitment windows or generating bottleneck effects, be a source of an imbalance in gene representation (Konnert and Hussendörfer 2001;Vranckx et al 2014).…”