Simultaneous influence of canopy decline and deer herbivory on regeneration in a conifer–broadleaf forest

Abstract

Understanding how forests respond to multiple disturbances is becoming increasingly important under global change. We examined the simultaneous influence of canopy decline and deer browsing on regeneration in an old-growth reserve and surrounding managed forest dominated by Fagus sylvatica L. and Abies alba Mill. in Slovenia. We quantified both disturbance processes by measuring characteristics of canopy gaps and reconstructing historical deer densities. Forest response was assessed with repeated measurements of tree regeneration and regeneration patterns within deer exclosures. Most gaps were formed by mortality of A. alba (71%), and gapmaker characteristics suggest that gaps formed slowly and often expanded, resulting in a mosaic of openings covering 17% of the old-growth reserve. Fagus sylvatica dominated the regeneration layer throughout the reserve and recruited to taller height classes over the past 26 years. The recruitment failure of preferred browse species (A. alba and Acer pseudoplatanus L.) in the reserve and the successful recruitment of these species within exclosures indicate that selective browsing by deer has altered the successional response to A. alba decline, facilitating the dominance of F. sylvatica. Given that global change may increase forest decline worldwide and the ubiquitous nature of deer browsing in many temperate forests, understanding their combined effects on forests will become increasingly important.Résumé : Il devient de plus en plus important de comprendre comment les forêts réagissent aux perturbations multiples dans un contexte de changement global. Nous avons examiné les influences simultanées du dépérissement forestier et du broutement par le cerf sur la régénération dans une réserve de forêt ancienne et la forêt aménagée périphérique dominée par Fagus sylvatica L. et Abies alba Mill. en Slovénie. Nous avons quantifié les deux processus de perturbation en mesurant les caractéristiques des trouées dans la voûte forestière et en reconstituant l'historique des densités de cerf. La réponse de la forêt a été évaluée par des mesures répétées de la régénération arborescente et des patrons de régénération dans des exclos à cerf. La plupart des trouées résultaient de la mortalité d'A. alba (71 %) et les caractéristiques des arbres morts responsables de la création des trouées indiquent qu'elles se sont formées lentement et se sont souvent agrandies, engendrant une mosaïque de trouées couvrant 17 % de la réserve de forêt ancienne. Fagus sylvatica a dominé la strate de régénération dans toute la réserve et il s'est installé dans les étages supérieurs au cours des 26 dernières années. L'absence de recrutement des essences les plus broutées (A. alba et Acer pseudoplatanus L.) dans la réserve et le succès de recrutement de ces essences dans les exclos indiquent que le broutage sélectif par le cerf a changé la réponse successionnelle au dépérissement d'A. alba, facilitant du coup la dominance de F. sylvatica. Considérant que le changement global peut favoriser le dépérissement forestier ...

Sycamore maple (Acer pseudoplatanus L.) stands on former agricultural land in the Sudetes – evaluation of ecological value and production potential

“…Schulze et al (2014) reported that sycamore regeneration is damaged by red and roe deer to a greater extent than European beech regeneration. Similar findings were observed from stands under conversion or from stands with dominant Norway spruce where the number of juvenile sycamore individuals was low (Diaci, 2002;Nagel et al, 2015). In these cases, Mosandl & El Kateb (1988) and Ammer (1996) recommended the control and regulation of game stocks in order to provide for sufficient density of regeneration and its prosperity.…”

Cascading effects of canopy mortality drive long‐term changes in understorey diversity in temperate old‐growth forests of Europe

“…While there is no historical evidence that these stands have ever been managed, they have all been indirectly influenced by anthropogenic drivers, including air pollution that presumably played an important role in the dieback of A. alba , climate change, and high population densities of red deer. The latter has resulted in chronic browsing of palatable tree species, particularly A. alba , causing a pronounced recruitment failure across the region (Nagel et al., ). Both of these processes have been well documented during the time period of the study.…”

Influence of salvage logging on forest recovery following intermediate severity canopy disturbances in mixed beech dominated forests of Slovenia

“…The density of red deer in Slovenia is high, with more than 10 deer km -2 in some regions (Nagel et al 2014a). Moreover, compared to species of Fagus sylvatica and Carpinus betulus regeneration, many of the less shade tolerant tree species in the regeneration layer, particularly Acer pseudoplatanus, A. platanoides, Ulmus glabra, Fraxinus excelsior and F. ornus are highly preferred browse species (Gill 1992).…”