Competitive effects of herbaceous vegetation on tree seedling emergence, growth and survival: Does gap size matter?

Abstract

Question:What is the effect of gap size on the seedling emergence, growth and survival of four common tree species in wooded pastures? Location: A pasture in the Jura mountains, Switzerland. Methods: Seeds were sown in a complete three-way factorial design with eight blocks in May 2003. Each block consisted of a competition treatment (four gap sizes including zero) and a mowing treatment (mown and unmown). Emergence, survival and total biomass of tree seedlings of three species (Picea abies, Acer pseudoplatanus and Fagus sylvatica) were measured. A fourth species (Abies alba) failed to germinate. Results: Gaps had a positive influence on the early stages of tree development for all species. Larger gaps favoured growth and survival more than small gaps. Seedling growth was higher when vegetation around the openings was mown. Mowing the vegetation at gap size zero enhanced both growth and survival compared to unmown vegetation. Mown gaps larger than zero had increased seedling desiccation but decreased seedling predation. Species showed similar trends in their emergence and growth responses to gap size and mowing treatments but for Picea emergence rate was higher and survivorship was lower than for Acer and Fagus. Conclusions: Gap size does matter for tree seedling success but even in more favourable large gaps only a small percentage of seedlings emerged and survived. The effects of gaps on tree seedling establishment are complex as a result of interactions between biotic and abiotic changes caused by gaps.

Restoration of woodpasture on former agricultural land: The importance of safe sites and time gaps before grazing for tree seedlings

“…In natural and semi-natural circumstances, these stress factors were found to be equally or even more important than grazing (Frost and Rydin, 1997;Pé pin et al, 2006). In woodpastures in the Swiss Jura, desiccation of seedlings was the most common cause of seedling death (Vandenberghe et al, 2006). In the same area, Smit et al (2006) found that grazing was the major cause of death, except for saplings planted near unpalatable Gentiana species.…”

Sustainable Land Use in Mountain Regions Under Global Change: Synthesis Across Scales and Disciplines

“…At an intermediate scale, i.e., a few square meters, cattle choose those plant communities that are easiest to forage and that feature the best pastoral value (Kohler et al 2004a). At the finest scale, i.e., within a given vegetation community, cattle avoid dung pats and unpalatable plants (Smit et al 2005), create disturbances that promote species turnover (Kohler et al 2006b, Gillet et al 2010, and determine tree regeneration (Vandenberghe et al 2006). Thus, management alternatives focusing on just one of these dimensions, e.g., cattle management, will fail to properly address issues related to vegetation dynamics and thus EGS provision.…”

“…Second, we evaluate the results of the project with Buttler et al 2009 Fine-scale monitoring and manipulative field experiments to improve the understanding of environmental determinants of tree establishment, growth, and mortality as well as the impact of cattle activities on vegetation, habitat use, and soils. x x Kohler et al 2004a,b, 2006a,b, Smit et al 2005, Vandenberghe et al 2006, 2007, 2008, 2009, Gillet et al 2010 Assessment of carbon fluxes, soil respiration, aboveground and belowground biomass, community structure, & dynamics under climate change.…”

A Contextual Analysis of Land-Use and Vegetation Changes in Two Wooded Pastures in the Swiss Jura Mountains

“…Nevertheless, pasture and forest management have significantly influenced the local patterns of tree dynamics. Besides logging activities, managing the cattle behavior with fences and watering points strongly impacted the potential for tree regeneration (Kohler et al 2006, Vandenberghe et al 2006). Yet, extensification seems to have been difficult to avoid in the last 30 years of the twentieth century in Rionde.…”