Contents lists available at ScienceDirect Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet Microclimate differences above ground-layer vegetation in lichen- dominated pine forests of north-central British Columbia Sean R. Haughian a, ⁎ , Philip J. Burton b a New Brunswick Museum, 277 Douglas Ave., Saint John, NB, E2 K 1E5, Canada b University of Northern British Columbia, 4837 Keith Avenue, Terrace, BC, V8G 1K7, Canada ARTICLE INFO Keywords: Reindeer lichen Feathermoss Ground cover Lodgepole pine Microclimate Water potential ABSTRACT Lodgepole pine forests of north-central British Columbia have patchy ground-layer vegetation, typically domi- nated by either fruticose lichens, feathermosses, or ericaceous vascular plants; this patchy structure has been shown to correspond with environmental variables that likely moderate the ground-layer microclimate. To in- vestigate the potential role of microclimate on patterns of dominance of ground-layer functional groups, we recorded temperature and relative humidity above the ground-layer vegetation during 25 summer days over patches dominated by mat-forming lichens, feathermosses, or vascular plants. Data were summarized for raw microclimate attributes and daily water potential of the air, and in terms of modelled equilibrium water content of moss or lichen thalli. Analysis of variance revealed significant differences in the water potential of air above the three patch types under sunny conditions, but not under overcast conditions. Differences in vegetation cover were only associated with differences in atmospheric moisture when using data from sunny periods during the daytime. These data confirm that lichens occupy microclimatic niches that are distinctly drier than those of feathermosses or vascular plants, and corroborate the suggested mechanism by which canopy or soil properties influence these types of ground-layer vegetation. 1. Introduction Many studies have described the influence of humidity, water po- tential, and other measures of atmospheric moisture on physiological activity in bryophytes and lichens under controlled conditions (Longton, 1988; Proctor, 2000). Because the greatest diversity of li- chens and mosses occurs in locations with exceptionally high rainfall, the greater importance of precipitation compared to other types of at- mospheric water is clear (Goward and Spribille, 2005; Hauck and Spribille, 2005; Radies et al., 2009; Turner et al., 2006). Nevertheless, when precipitation is limited, water supplied as condensate or vapour (e.g., dew or fog) may be an important mechanism of hydration, leading to rich and diverse communities on its own (Kidron et al., 2002; Lange et al., 1991). Studies that investigate the relationship between water availability and cryptogam dominance or distribution, should therefore incorporate both precipitation events and the various forms of water vapour. The frequency or duration of water supply can be affected by small- scale variation in vegetation cover or topography, particularly when this variation affects whether or not a given patch receives direct ir- radiance from the sun (Chen et al., 1993; Jones, 1983; Kidron, 2005). Such processes are thought to be responsible for much of the patchiness in understory (including field and ground-layer) vegetation of boreal regions (Kembel and Dale, 2006; Kuuluvainen and Hokkanen, 1993). For example, differing irradiance may be responsible for the differ- entiation of epixylic bryophyte communities on fallen logs between eastward-facing and westward-facing aspects (Jansová and Soldán, 2006), and the combination of differing irradiance and precipitation interception appear to be important controls on the small-scale patchiness of lichen and feathermoss-dominated ground layers of lod- gepole pine (Pinus contorta var. latifolia) forests (Haughian and Burton, 2015; Sulyma and Coxson, 2001). The associations between ground cover vegetation and micro- climate in lichen-dominated ecosystems have been studied intensively in parts of central Canada, but studies elsewhere have tended to con- sider the role of microclimate only indirectly, via the assumed effects of other habitat variables. For example, soil moisture conditions have been shown to coincide with both the growth rate and size of lichen thalli (Kershaw and Rouse, 1971), and with the overall community composition of ground layer vegetation over space and time (Kershaw, 1977; Rouse and Kershaw, 1973). Scientists in western Canada have also suggested that niche differentiation among ground-layer functional https://doi.org/10.1016/j.agrformet.2017.11.029 Received 11 June 2017; Received in revised form 21 November 2017; Accepted 26 November 2017 ⁎ Corresponding author. E-mail address: sean.haughian@unb.ca (S.R. Haughian). Agricultural and Forest Meteorology 249 (2018) 100–106 0168-1923/ © 2017 Elsevier B.V. All rights reserved. T