Moisture, thermal inertia, and the spatial distributions of near-surface soil and air temperatures: Understanding factors that promote microrefugia

Abstract

, J. R. (2013). Moisture, thermal inertia, and the spatial distributions of near-surface soil and air temperatures: understanding factors that promote microrefugia. Agricultural and Forest Meteorology, Moisture, thermal inertia, and the spatial distributions of near-surface soil and air temperatures: understanding factors that promote microrefugia AbstractClimate change poses significant threats to biodiversity, but some species may be able to escape its effects in small locations with unusual and stable climates (microrefugia). However, there are still great uncertainties about where microrefugia are located, and the exact role that moisture plays in buffering extreme temperatures. In this study we quantified the effects of moisture on the distribution and variability of nearsurface soil and air temperatures. We collected hourly 1 cm soil and 5 cm air temperatures and humidities at 111 sites from May 2011 to March 2012. Sites were diverse in terms of elevation (2-1428 m), distance from coast (180 m-403 km), canopy cover (0-100%), topographic exposure, and susceptibility to cold air drainage. We found that variability (diurnal range) of both soil and air temperatures decreased under moister conditions. While air temperatures were related more strongly to humidity, soil temperatures were related more to vapour pressure deficit (VPD). That is, both high temperature and low humidity were required before the VPD was sufficient to dry out the soil and allow soil temperatures to vary. We then used a regional regression approach to model the spatial distribution of minimum and maximum air and soil temperatures for each day over the 10 months in terms of latitude, elevation, canopy cover, distance to coast, cold air drainage potential, and topographic exposure to the south and northwest. We found that elevation was the dominant factor explaining the distribution of soil and air temperatures under moist conditions. Other factors, such as canopy cover and topographic exposure, had a stronger influence on air temperatures whenever humidity was low. However, these factors only affected soil temperatures at times when higher temperatures combined with low humidity to produce higher VPD. Our results provide new insights into how moisture influences the spatial distribution of near-surface soil and air temperatures. Microrefugia will be more apparent under drier conditions, but climate change may affect refugia for soil and air temperatures differently. Higher temperatures will cause VPD to increase more than would be expected by any change in humidity, and refugia in terms of soil temperatures may therefore become increasingly apparent. AbstractClimate change poses significant threats to biodiversity, but some species may be able to escape its effects in small locations with unusual and stable climates (microrefugia).However, there are still great uncertainties about where microrefugia are located, and the exact role that moisture plays in buffering extreme temperatures. In this study we quantified the effects of moisture o...

The Short-Term Effects of Experimental Forestry Treatments on Site Conditions in an Oak–Hornbeam Forest

“…It is also noticeable that the VPD in the gap-cuts increases synchronously with that in the clear-cuts, but presumably because of enhanced evaporation of the moist soil surface and the transpiration of herbs, its value sinks to the level of the uncut control [26,82]. As Aschroft and Gollan demonstrated [111], moister conditions reduce the diurnal variability of soil and air temperature, and VPD more. This may be an additional explanation of the more stable microclimate in the gap-cuts.…”

“…In the clear-cuts, the T soil was much lower in the end of the growing season than that in the other treatments, suggesting that regenerating the vegetation may experience a more pronounced frost-exposure in this forestry system [21,33]. In general, the buffering capacity of the forests, concerning numerous microclimate variables (e.g., the diurnal variability of T air , RH, VPD, or T soil ) is related to the leaf area index and also to the soil water potential [22,26,111]. Gray and colleagues found similar annual pattern in the case of SWC means in the gaps vs. uncut control [81].…”

Monthly microclimate models in a managed boreal forest landscape

“…By modelling average extreme temperatures separately over 12 months, we could also study the temporal dynamic of the effects of landscape physiography and vegetation on near-ground temperatures. This temporal variation in effects and importance of microclimatic drivers seems to be common, and has been found when modelling seasonal, daily or hourly temperatures separately (Ashcroft and Gollan, 2013a;George et al, 2015;Maclean et al, 2016).…”

“…Fridley, 2009;Geiger et al, 2012;Lookingbill and Urban, 2003;Meineri et al, 2015), only few have considered also seasonal changes in climate-forcing factors and their relative influence on near-ground temperatures (e.g. Ashcroft and Gollan, 2013a).…”

Detecting microrefugia in semi-arid landscapes from remotely sensed vegetation dynamics

“…Water subsidies, such as from springs or runoff from rock outcrops and other areas with reduced infiltration, are likely to provide microrefugia from drought (McLaughlin et al, 2017;Reside et al, 2014). In addition, the moderating influence of moisture and humidity are related to the occurrence of thermal microrefugia buffering temperature extremes (Ashcroft and Gollan, 2013) and may provide microrefugia from fire disturbances as well (Ouarmim et al, 2014;Reside et al, 2014;Wilkin et al, 2016). There is limited spatial hydrologic data available for the study area, so only coarse proxies were possible.…”