Microhabitats and canopy cover moderate high summer temperatures in a fragmented Mediterranean landscape

Abstract

Extreme heat events will become more frequent under anthropogenic climate change, especially in Mediterranean ecosystems. Microhabitats can considerably moderate (buffer) the effects of extreme weather events and hence facilitate the persistence of some components of the biodiversity. We investigate the microclimatic moderation provided by two important microhabitats (cavities formed by the leaves of the grass-tree Xanthorrhoea semiplana F.Muell., Xanthorrhoeaceae; and inside the leaf-litter) during the summer of 2015/16 on the Fleurieu Peninsula of South Australia. We placed microsensors inside and outside these microhabitats, as well as above the ground below the forest canopy. Grass-tree and leaf-litter microhabitats significantly buffered against high temperatures and low relative humidity, compared to ground-below-canopy sensors. There was no significant difference between grass-tree and leaf-litter temperatures: in both microhabitats, daily temperature variation was reduced, day temperatures were 1–5°C cooler, night temperatures were 0.5–3°C warmer, and maximum temperatures were up to 14.4°C lower, compared to ground-below-canopy sensors. Grass-tree and leaf-litter microhabitats moderated heat increase at an average rate of 0.24°C temperature per 1°C increase of ambient temperature in the ground-below-canopy microhabitat. The average daily variation in temperature was determined by the type (grass-tree and leaf-litter versus ground-below-canopy) of microhabitat (explaining 67%), the amount of canopy cover and the area of the vegetation fragment (together explaining almost 10% of the variation). Greater canopy cover increased the amount of microclimatic moderation provided, especially in the leaf-litter. Our study highlights the importance of microhabitats in moderating macroclimatic conditions. However, this moderating effect is currently not considered in species distribution modelling under anthropogenic climate change nor in the management of vegetation. This shortcoming will have to be addressed to obtain realistic forecasts of future species distributions and to achieve effective management of biodiversity.

Plant and ant assemblages predicted to decouple under climate change

“…The finding that ant species composition correlated more strongly with precipitation than temperature was contrary to our expectations that small ectotherms would be primarily temperature‐driven as found in other studies (Sanders, Lessard, Fitzpatrick, & Dunn, ; Tiede et al., ). However, the included temperature variables were modelled air temperature rather than ground surface temperature, the latter being likely to be more relevant for ants (Lessard, Dunn, & Sanders, ) and subject to small‐scale microclimatic variation (Keppel, Anderson, Williams, Kleindorfer, & O'Connell, ). The correlation of slope and aspect variables to ant assemblages (Table ) and the inclusion of those variables as predictors in our stepwise model building process (Table ) reflects the importance of insolation as a key driver of ant species composition (Andersen, ).…”

Changes in climate and vegetation with altitude on Mount Batilamu, Viti Levu, Fiji

“…Both canopy cover and microhabitats are known to moderate microclimate (Keppel et al . 2017 a , Scheffers et al . 2014).…”

A Common Yardstick to Measure the Effects of Different Extreme Climatic Events on Soil Arthropod Community Composition Using Time-Series Data

“…This can potentially be attributed to stress on stress effects, which are more apparent in this open vegetation type than in the more buffered vegetations of the other three location-vegetation type combinations. Vegetation can provide strong buffering effects on abiotic factors, creating micro-habitats that effectively lessen the effects of extreme events (Scheffers et al, 2014;Woods et al, 2015;Keppel et al, 2017;Franken et al, 2018). As such buffering vegetation is absent in the open vegetation type, this is already a more challenging place to inhabit compared to the vegetated sites, considering the more severe environmental conditions in green beach ecosystems (Bakker et al, 2005).…”

“…The arthropod communities were monitored for more than 2 years with frequent sampling intervals on two locations that differed in frequency of inundation with sea water. One of those locations was further subdivided in three vegetation types that differed in vegetation structure, plant height, and soil coverage, which may impact the effect of climate extremes on soil communities by providing micro-habitats (Scheffers et al, 2014;Woods et al, 2015;Keppel et al, 2017;Franken et al, 2018). Using species abundance of these natural communities over time, we could link the changes of community composition to events of abiotic stress in the field which allowed us to answer the following two main questions: (i) Which abiotic factors have the strongest influence on soil fauna community composition in vegetated beaches, and does this differ between the locations and vegetation types?…”