Reversing legacy effects in the understory of an oak-dominated forest

Abstract

Current forests developed under conditions different from original forests, with higher deer densities, reduced fire frequency, denser canopies, and smaller canopy gaps. These alterations have led to understories dominated by species simultaneously browse tolerant, shade tolerant, and fire sensitive leading to difficulties in the regeneration of oak species (Quercus spp.) in some areas. We evaluated how three key processes -understory fire, canopy gaps, and browsing -influenced tree species in east central West Virginia. We were particularly interested in the response of oak species because they are the dominant overstory species and of maple species (Acer spp.), black birch (Betula lenta L.), and yellow-poplar (Liriodendron tulipifera L.) as these are likely to replace the current forest. Single-process effects were significant and significant interactions among processes were numerous. In general, fire caused significant reductions of seedlings and saplings of red maple (Acer rubrum L.) and striped maple (Acer pensylvanicum L.) and increased the seedlings of black birch and yellow-poplar. Canopy gaps increased the abundance of black birch and yellow-poplar seedlings and saplings. Gaps and fire together caused an increase in the relative abundance of yellow-poplar. Excluding browsers and creating canopy gaps together nearly doubled oak sapling importance values versus either treatment alone; however, oak importance values remained low. Given the significant interactions of browse control with the other two processes, browse control should be considered when planning oak regeneration treatments such as canopy gaps or prescribed fire. Résumé :Les forêts actuelles se sont développées sous des conditions différentes de celles des forêts d'origine, soit une densité plus élevée de cerfs, une fréquence de feu plus faible et un couvert forestier plus dense comportant de plus petites trouées. Ces modifications ont produit des sous-étages dominés par des espèces simultanément tolérantes au broutement, tolérantes à l'ombre et sensibles au feu, ce qui a causé des problèmes de régénération des espèces de chêne à certains endroits. Nous avons déterminé de quelle façon trois processus clés : les feux en sous-étage, les trouées dans le couvert forestier et le broutement, ont influencé la présence d'espèces d'arbre dans le centre-est de la Virginie occidentale. Nous étions particulièrement intéressés par la réaction des espèces de chêne, parce qu'elles sont les espèces dominantes du couvert, et par les érables, le bouleau noir et le tulipier de Virginie, parce que ces espèces remplaceront probablement les espèces dominantes actuelles. Les effets simples des processus étaient significatifs et les interactions significatives entre les processus étaient nombreuses. En général, le feu a significativement réduit le nombre de semis et de gaules d'érables rouge et de Pennsylvanie, et a augmenté le nombre de semis de bouleau noir et de tulipier de Virginie. Les trouées dans le couvert forestier ont causé une augmentation de l'abondance ...

Exclosures can favour natural regeneration of oak after conservation-oriented thinning in mixed forests in Sweden: A 10-year study

“…No tall oak saplings were recorded in controls. Our results are consistent with earlier studies of oak regeneration and effects of protection from browsing (Abrams, 2013;Bergquist et al, 2009;Jensen et al, 2012;Kelly, 2002;Pigott, 1983;Thomas-van Gundy et al, 2014). Exclosures were intentionally placed over relatively high density of oak seedlings and saplings; this was also true for controls, and the results of the BACI-test show that the density of oak seedlings and small oak saplings did not differ initially between controls and exclosures.…”

“…Mihók et al, 2009;Smit et al, 2012;Thomas-Van Gundy et al, 2014). Through their browsing preferences ungulates can reduce the abundance of some species, hence changing species composition of trees and other plants (Pellerin et al, 2010;Rooney and Waller, 2003).…”

Red oak seedlings as indicators of deer browse pressure: Gauging the outcome of different white‐tailed deer management approaches

“…We evaluated deer browse rate as a function of management regime and fencing (open or caged) with Cox proportional hazard models implemented in the R statistical (R Core Team, 2016) package "coxme" (Therneau, 2015). We included initial oak height at planting and average vegetation height (for 2010 only) as covariates.…”

“…These regeneration failures, as in many other woody species, occur despite abundant mature oak trees that mast frequently followed by successful acorn germination. However, seedlings are unable to advance to the sapling stage, a pattern that can be reversed through fencing, suggesting that deer play an important role in preventing this transition (Abrams & Johnson, ; Leonardsson, Lof, & Gotmark, ; Long et al, ; Long, Pendergast, & Carson, ; Schwartz & Demchik, ; Thomas‐Van Gundy, Rentch, Adams, & Carson, ). These patterns suggested that selecting Q. rubra was an appropriate and sensitive indicator for assessing the outcome of our different deer management approaches.…”

Tree-Level Harvest Optimization for Structure-Based Forest Management Based on the Species Mingling Index

“…Further, the case study stand contains a large number of generally non-merchantable trees (Ostrya virginiana) that may require removal to promote the regeneration of desirable tree species (e.g., oaks). Although one goal of management may be to promote higher quality deer habitat from the current mature forest, deer exclusion may also be necessary to control browsing on oak seedlings and saplings that are regenerating within canopy gaps [39]. Finally, small animal consumers of acorns produced by oak trees can complicate the desired goals associated with using silvicultural treatments that promote oak regeneration, particularly when the timing of harvest entries attempts to coincide with the periodicity of acorn production from mature trees [40].…”