Old-growth forest floor richness increases with red deer herbivory intensity

Abstract

Denne fila er lasta ned frå Høgskulen i Sogn og Fjordane sitt institusjonelle arkiv, Brage, http://brage.bibsys.no/hsf/ Dette er forfatterens aksepterte versjon av artikkelen som originalt er publisert i Forest Ecology and Management (Elsevier): Hegland, S. J., Lilleeng, M. S. & Moe, S. R. (2013). Old-growth forest floor richness increases with red deer herbivory intensity., 310, 267-274.Abstract: Herbivory is one of the most important biotic disturbance types globally and is important for community structure and composition through species filtering. In northern forest ecosystems the population densities of wild-ranging ungulates, which are managed through hunting, have reached historically high numbers. Conservation concerns frequently arise, both in media and scientific literature. One key question is whether increased deer densities negatively affect biodiversity and whether management should implement reduction in deer densities. Few studies have addressed wild herbivores-plant richness relationships using a full length gradient of herbivory. Such gradient approach where herbivory is studied from very low to very high intensity, may enable us to develop operational management guidelines for deer densities We recorded the ungulate herbivory intensities on the island Svanøy in west Norway across ten years and related this to the present plant richness of an old-growth pine-forest system, recording all plant species groups of the forest understory. The herbivory intensity-plant richness relationship followed a unimodally peaked curved, but plant richness was lower only at forest sites with artificially high red deer herbivory. Overall, the herbivoryrichness relationships of functional groups fitted expectations in that the richness of low-growing functional groups as forbs, graminoids and mosses all increased within natural levels of herbivory intensities, whereas the richness of the taller growing woody species of the forest understory, dwarfshrubs and young trees, decreased along the intensity gradient. We validated the gradient approach by experimental exclosure data. Management for relatively high deer densities may benefit the overall understory plant richness of such forest ecosystems at the expense of richness of woody plants. We suggest that the herbivory-induced reduction of the understory woody layer is the key to understand the overall increase in plant species richness. On behalf of the authorsStein J. Hegland Sogndal, Norway, 13 august, 2013 Covering letter HighlightsDoes increased herbivory by red deer harm boreal forest floor richness?We examine this by relating a herbivory intensity gradient to plant species richness.Increasing herbivory intensity enhance richness except at artificially high herbivory levels.Low-growing species groups benefit at the expense of taller growing woody species.Boreal forest floor richness may benefit from relatively high red deer herbivory intensity. *Highlights (for review) Dear ReviewersWe are grateful for the constructive comments to our manuscript. We do believe ...

Understory vegetation dynamics and tree regeneration as affected by deer herbivory in temperate hardwood forests

“…Graminoids and ferns, therefore, benefitted from browsing pressure, a result which has also been found in other studies (Rooney 2001, Hegland et al 2013. Likewise, the competitive ability of beech saplings was detrimental to plant community richness and diversity at site 1 in agreement with the results of other studies (Boulanger 2010).…”

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Can browsing by deer in winter induce defence responses in bilberry (Vaccinium myrtillus)?

“…Since the 1990s, there has been an annual cull of 20 000-40 000 red deer in Norway (Statistics-Norway 2014) and given current numbers, the cull corresponds to >1 deer per km 2 forest area in the study county of Sogn og Fjordane (Solberg et al 2012). Such harvest numbers reflect densities at intermediate European level (e.g., Milner et al 2006;Hegland et al 2013). In the seasonal climate of the boreal forest, the winter range of red deer may be strongly limited by snow, resulting in locally very high densities as indicated by the increased risk of vehicledeer collisions in the western Norwegian lowlands in winter (Meisingset et al 2014).…”