Fine-Scale Microclimate Pattern in Forest-Steppe Habitat

Abstract

Microclimate and vegetation architecture are interdependent. Little information is available, however, about the fine-scale spatio-temporal relationship between the microclimate and herb layer of forest-steppe mosaics. In 2018 a three-season-long vegetation sampling and measurements of air temperature and air humidity were performed along 4 transects (44 m long each) in the herb layer with 89 dataloggers in the sandy region of Central Hungary, in a poplar grove and the surrounding open grassland. In order to improve data analysis, we introduced the use of a duration curve widely used in hydrology and proved to be useful in the processing of intensive climatic data. We analysed the effect of the direction and altitude of the solar irradiation and the edge effect on the microclimatic pattern. We also surveyed, seasonally, the spatial pattern of the exceedance rate for the vapour pressure deficit (VPD) in relation to the transect direction and to the edge of the grove. The exceedance rate for the VPD indicated considerable seasonal differences. The VPD exceedance rate indicates the stress effect for the vegetation. The moderating effect of the grove was small at 1.2 kPa VPD, but at 3.0 kPa—stronger stress—it was considerable. On the warmer side of the transects, mostly exposed at the south-eastern edge, the exceedance rate rose abruptly with distance from the edge compared to the gradual increase on the colder side. The cardinal and intercardinal directions as well as the altitude of the Sun all had influences on the moderating and shading effects of the grove. The southern edge was not always consistently the warmest. The distribution of the VPD values above the 3.0 kPa threshold varied within a seemingly homogeneous grassland, which highlights the importance of fine-scale sampling and analysis. This knowledge is valuable for assessing the dynamics and spatio-temporal patterns of abiotic factors and physiognomy in this type of ecosystem.

How climate, topography, soils, herbivores, and fire control forest–grassland coexistence in the Eurasian forest‐steppe

“…Trees of the forest‐steppe have strong feedbacks on local conditions beneath their canopy. Tree canopies intercept solar radiation, leading to low light availability, cooler diurnal temperature and higher relative air humidity at the forest floor, and the canopy reduces heat loss at night compared to the steppes (Breshears et al ., 1997 ; D'Odorico et al ., 2013 ; Tölgyesi et al ., 2018 , 2020 ; Süle et al ., 2020 ). Microclimatic extremes are also tempered within forest patches by the edges acting as wind breaks and thus attenuating evaporation compared to adjacent grasslands (Davies‐Colley, Payne & van Elswijk, 2000 ).…”

Microclimatic buffering in forest, agricultural, and urban landscapes through the lens of a grass‐feeding insect

“…On the one hand, nearby woodlots may provide microclimatic conditions that protect larval stages and grass blades from heat stress, regardless of the nature of the wider landscape. At the level of the host plant, even small nearby woodlots could provide shade, block wind, and retain outgoing radiation (Geiger et al, 2003; Süle et al, 2020). However, on a landscape scale, forest, agricultural, and urban climatic conditions differ significantly: forests typically buffer fluctuations in temperature and humidity with effects gradually diminishing toward the forest edges (Lin et al, 2020) and cause sub‐canopy cooling during summer (Haesen et al, 2021).…”

“…Although the measurement of VPD has gained much more attention in studies on plant microhabitats (Aguirre et al, 2021; Davies‐Colley et al, 2000; Süle et al, 2020; von Arx et al, 2013), it may also matter for microclimates that affect small organisms like insects. VPD is exponentially related to changes in temperature under constant humidity and is regarded as the “drying power” of the air on wet surfaces (Monteith & Unsworth, 2013).…”

Ecotones in Central European forest–steppe: Edge effect occurs on hard rocks but not on loess

“…The forest–steppe ecotone is partially shaded, which limits the adverse effects of direct sunlight, but still ensures sufficient light for species that are generally considered light‐demanding to thrive (see Roleček et al, 2017). Partial shading and lower wind speeds also buffer climatic extremes and reduce evaporation and transpiration, which promote water retention (De Frenne et al, 2019; Süle et al, 2020). Leaf litter is partially blown away from ecotones, resulting in less nutrient enrichment than in the forest interior (Gonschorrek, 1977).…”