Herbivory and plant competition reduce mountain beech seedling growth and establishment in New Zealand

Abstract

The effect of herbivory and resource availability on the competitive ability of different plant species has been an area of intense debate amongst plant ecologists for at least two decades, but the interactive effects of herbivory and plant competition between woody and herbaceous plants are rarely studied and theory is poorly developed. This study used experimental manipulations on transplanted and naturally occurring mountain beech (Nothofagus solandri var. cliffortioides) seedlings to show the effects of deer browsing and competition from deer-induced, herbaceous turf communities on mountain beech regeneration in New Zealand. Differences in the species composition of these turfs had little effect on mountain beech seedling establishment, but turf removal increased seedling growth and survivorship, showing that competition with other plants had direct effects on mountain beech regeneration. Deer browsing reduced the establishment and growth of seedlings, but the size of this effect did not vary with light and nutrient availability. There was no immediate compositional response of turf communities following the removal of deer browsing. The addition of nutrients appeared to reduce the intensity of belowground competition (stem growth increased relative to root growth) and increase seedling mortality, but there was no effect of changing levels of light. These results showed simple and direct negative effects of deer browsing on mountain beech regeneration. Indirect negative effects on regeneration were caused by deer-induced turf communities. We found little evidence for interactive effects between herbivory, plant competition and the availability of light or nutrients on seedling regeneration, which suggests that these factors acted independently.

Environmental context determines within- and potential between-generation consequences of herbivory

“…Deer-browsed plants were over 4 times more likely to die in light gaps than in the understory. In contrast, tree seedlings have been shown to have lower survival in response to clipping or mammalian browsing in understory habitats in many species (Blundell and Peart 2001;Milbrath 2008;Norghauer et al 2008) but not all (Husheer et al 2006). The diVerence in survival found here was caused by disparities in the extent of deer-inXicted damage to lightgap and understory plants.…”

White‐tailed deer (Odocoileus virginianus) positively affect the growth of mature northern red oak (Quercus rubra) trees

“…Those studies mainly show that herbivory by deer and other large mammalian herbivores have strong negative effects on plant growth, reproduction, survival, and terrestrial carbon storage (Crête et al 2001, Russell et al 2001, Côté et al 2004, Knight et al 2009, MacDougall et al 2010. Herbivory on younger life cycle stage trees will eventually influence the structure of the future mature forest (Husheer et al 2006, Long et al 2007 Effects of deer on the growth of mature canopy trees have rarely been reported. The few studies showing impacts of deer on larger tree species include in their definition of mature individuals from young life stages or from smaller size classes with which deer can interact directly through browsing or other means.…”

“…In recent years, deer (Cervidae) populations have increased dramatically throughout many areas of the world, including North America (Horsley et al 2003), Europe (Apollonio et al 2010), Asia (Tsujino andYumoto 2004, Suzuki et al 2008), and Oceania (Platt et al 2004, Husheer et al 2006. Population increases have been driven primarily by forest clearing (Dale 1997), reduction of predator populations (Mladenoff et al 1999), and milder winter temperatures (Dumont et al 2000).…”

Interaction between large herbivore activities, vegetation structure, and flooding affects tree seedling emergence

“…Below-ground competition was probably low due to the nutrient rich seed-bed plots and permanent water supply in our experiment. Under such reduced stress conditions, enhanced shoot or stem growth is to be expected (Davis et al 1999;Husheer et al 2006). However, the positive effect of a low surrounding grassland vegetation in our experiment may not be equally present in permanently grazed, natural conditions due to associated palatability (i.e.…”