Microclimate through space and time: Microclimatic variation at the edge of regeneration forests over daily, yearly and decadal time scales Thomas P. Baker a,⇑ , Gregory J. Jordan a , E. Ashley Steel c , Nicholas M. Fountain-Jones a , Timothy J. Wardlaw b , Susan C. Baker a,b a School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia b Forestry Tasmania, Research and Development Branch, GPO Box 207, Hobart, Tasmania 7001, Australia c Statistics, Paciﬁc Northwest Research Station, USDA Forest Service, 400 N34th Street, Suite 201, Seattle, WA 98103, USA article info Article history: Received 26 June 2014 Received in revised form 3 September 2014 Accepted 7 September 2014 Keywords: Disturbance Edge effects Forest inﬂuence Microclimate Recolonisation Variable retention abstract A major aim of sustainable forest management is the maintenance or recolonisation of harvested areas by species that were present pre-disturbance. Forest inﬂuence (a type of edge effect that focuses on the effect of mature forests on adjacent disturbed forest) is considered to be an important factor that contrib- utes to the ability of mature forest species to re-colonise disturbed areas. Forest inﬂuence occurs in two main ways by: (1) by providing a source of propagules or individuals for recolonisation; and (2) by its inﬂuence on the biotic and abiotic conditions of the disturbed forest. This study focuses on forest inﬂu- ence’s impact on microclimate conditions of adjacent disturbed areas regenerating after harvesting. In particular, the study investigates whether microclimate within a regenerating forest changes with increasing distance from a mature forest edge, and whether the magnitude of microclimatic change var- ies over diurnal, seasonal and successional time scales. Results of the study showed that the microclimate of regenerating forests is affected by the distance to a standing mature forest. Temperature, relative humidity, vapour pressure deﬁcit, and the short-term ﬂuctuations of these microclimate parameters were inﬂuenced by nearby mature forest. In addition, the study found that the magnitude of forest inﬂuence changes over diurnal, seasonal and successional time scales. For example, it was discovered that forest inﬂuence is greatest during the middle of the day, during the summer months when solar heating is greatest and on hot windy days. Critically, the impact of forest inﬂuence peaked around 27 years after disturbance in the areas studied, with less inﬂu- ence shortly after disturbance. We speculate this is due to lower levels of midday shading in the 7 year old forest. Forest inﬂuence on microclimate persisted in regeneration areas that were harvested 45 years ago, although the magnitude and importance of the effect was low. We conclude that proximity to mature forest stands (forests inﬂuence) impacts the microclimate of for- ests regenerating after disturbance, although the response is quite variable through time. Our results pro- vide insight into the role of microclimate on the ability of mature forest species to successfully re- colonise after disturbance. Management practices, such as aggregated retention and other forms of reten- tion forestry, which increase the proportion of harvested area under forest inﬂuence, may provide a mechanism to promote the re-colonisation of mature-forest species. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Sustainable forest management is increasingly focused on facilitating the survival and/or re-establishment of biodiversity in forests regenerating after disturbance (Franklin et al., 1997; Lindenmayer et al., 2012). Within disturbed landscapes, edges between disturbed and mature forest patches become prominent ecological features. These edges allow the ﬂow of energy, nutrients and species from one forest type to another (Murcia, 1995; Strayer et al., 2003; Hufkens et al., 2009). While almost all previous studies of edge effects have focused on the impact of disturbed forests on adjacent mature forest (e.g. Harper et al., 2005), it has recently become clear that the inverse edge effect (the impact of mature forest on adjacent disturbed forest or ‘forest inﬂuence’) affects the recolonisation of disturbed areas by mature-forest species. For- est inﬂuence includes biological processes, such as the distance that species can disperse from mature forest, as well as physical http://dx.doi.org/10.1016/j.foreco.2014.09.008 0378-1127/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +61 3 6226 2563. E-mail address: tpbaker@utas.edu.au (T.P. Baker). Forest Ecology and Management 334 (2014) 174–184 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco