Terms Of Microclimate Research Articles

Warming decreases thermal heterogeneity of leaf surfaces: implications for behavioural thermoregulation by arthropods

Summary Ectotherms rely heavily on the spatial variance of environmental conditions to thermoregulate. Theoretically, their fitness is maximized when they can find suitable microhabitats by moving over short distances – this condition is met when spatial variance is high at fine spatial scales. Strikingly, despite the diversity of organisms living in leaf microhabitats, little is known about the impact of warming on the spatial variance of climatic conditions at the scale of individual leaf surfaces. Here, we used experimental manipulation of ambient conditions to quantify the effects of environmental change on the thermal heterogeneity within individual leaf surfaces. We also explored the implications for behavioural thermoregulation by arthropods at a single leaf surface. Using thermography, we characterized the apple leaf microclimate in terms of span and spatial aggregation of surface temperatures across a range of air temperatures and relative humidities. Then, we assessed how thermal heterogeneity within individual leaves affected behavioural thermoregulation by the two‐spotted spider mite (Tetranychus urticae Koch) under both near‐optimal and sublethal conditions in this microhabitat. We measured the upper lethal temperature threshold of the mite to define sublethal exposure. Thermal heterogeneity of individual leaves was driven mainly by ambient air temperature. Higher air temperatures gave both smaller ranges and higher spatial aggregation of temperatures at the leaf surface, such that the leaf microclimate was homogenized. Tetranychus urticae used behavioural thermoregulation at moderate air temperature, when thermal heterogeneity was high at the leaf surface. At higher air temperature, however, heterogeneity declined and spider mites did not perform behavioural thermoregulation. Warming decreases thermal heterogeneity of leaf surfaces with critical implications for arthropods – behavioural thermoregulation alone is not sufficient to escape the heat in the leaf microhabitat. Information on spatial variance of microclimatic conditions is critical for estimating how readily organisms can buffer global warming by moving.

Evaluation of a microclimate model for predicting the thermal behavior of different ground surfaces

The microclimate model ENVI-met Version 4 was evaluated with field data in terms of the thermal behavior of different types of ground surface. A field experiment was conducted in a real construction project in Guangzhou, South China, from 29 August to 2 September in 2010. The surface types of concrete, tile, asphalt and grass were investigated. The comparison between observation and prediction was performed for both sub- and above-surface variables, including soil temperature at different depths, soil heat flux at the surface, surface temperature, and air temperature and humidity at different heights. The results show that the ENVI-met model is capable of reasonably modelling the diurnal thermal behavior of different ground surfaces and their effects on local air temperature and humidity. The comparison of spatial distributions of air temperature and humidity shows that the hotter/drier and cooler/wetter spots predicted by ENVI-met were generally consistent with the observations. The quantitative evaluation shows that the ENVI-met model is capable of predicting the microclimate in terms of different variables with good accuracy.

Forest fragmentation and matrix effects: the matrix does matter

Forest fragmentation and matrix effects: the matrix <i>does</i> matter

Effects of shoreline modification on a Northern Puget Sound beach: Microclimate and embryo mortality in surt smelt (Hypomesus pretiosus)

Human alteration of Puget Sound shorelines is extensive yet its ecological consequences are largely undocumented. This study evaluates differences between natural and heavily modified beaches in terms of microclimate and one aspect of biological condition. Electronic data laggers were placed at a tidal height of approximately 3.7 m (12 ft) above mean lower low water during July 16–20, 2001, to monitor light intensity, substrate and air temperatures, and humidity. Substrate samples were collected at the end of the monitoring period to evaluate condition and density of eggs from surf smelt (Hypomesus pretiosus), a forage fish species that spawns on gravel-sand beaches in the upper intertidal zone. The modified beach had significantly higher daily mean light intensity, air temperature and substrate temperature, and significantly lower daily mean relative humidity. Particularly striking were the differences in substrate temperature which, on the natural beach, ranged from 12.1°C to 18.2°C (mean=14.1°C) and on the modified beach ranged from 14.4°C to 29.4°C (mean=18.8°C). In addition to these different means and more extreme values, microclimate conditions on the modified beach were more variable, indicative of a less buffered environment. The proportion of smelt eggs containing live embryos on the altered beach was approximately half that of the natural beach.

Roost Selection and Roosting Behavior of Male Common Nighthawks

Many studies to date have documented clear energetic costs and benefits of avian roost selection. Male Common Nighthawks (Chordeiles minor) spend at least half of each day during the summer on a day-roost. Therefore selection of roost-sites likely has implications for survival and long-term fitness. Our objective was to identify characteristics of day-roosts used by male Common Nighthawks in Cypress Hills Provincial Park, Saskatchewan, Canada. We measured features of roost trees and monitored behavior of roosting birds. Nighthawks preferred trees situated on north facing slopes surrounded by trees with significantly lower canopy height compared to randomly measured trees. Roost trees were taller than random trees and occurred in less dense patches of forest. Birds always roosted parallel to branches and adopted a motionless posture. There was a non-significant trend for birds to roost on branches facing east. Birds typically roosted in a direction pointing away from the sun and away from the roost tree trunk. Roost trees emerging from the canopy may provide landmarks for birds as they search for suitable day-roosts, whereas a low tree density surrounding roost trees likely reduces flight costs associated with maneuvering. Our results suggest that roosts chosen by male nighthawks may provide selective benefits in terms of microclimate, energetics and predator avoidance, but further studies are needed to determine which is the most important.

Microclimatic interactions in agroforestry systems

The interaction of the components of an agroforestry system with elements of microclimate is presented in terms of the interception by foliage of radiant energy and of rainfall; and of the temperature, humidity and windspeed of air surrounding the foliage. Most of the measurements reported are from a trial in which pearl millet was grown at ICRISAT, Hyderabad, between hedges of Leucaena leucocephala Lam. In terms of microclimate, the main advantage of the alley system was to intercept more light throughout the year and therefore to produce more biomass. Temperatureand humidity within the alleys differed little from values in the open but windspeed was substantially less. The main disadvantage of the system in terms of pearl millet production was therefore competition below ground rather than above.

Temporal and microclimatic partitioning of the floral resources of Justicia aurea amongst a concourse of pollen vectors and nectar robbers.

The flowers of Justicia aurea, morphologically characteristic of ornithophily, attracted a diverse array of foragers where they occurred as a dense stand in the tropical forests at La Selva, Costa Rica, and so provided an arena for this study of competition and coexistence. Two hummingbird species (Phaethornis superciliosus and Campylopterus hemileucurus) visited the flowers legally early in the morning, and defended the nectar resource; a third smaller bird (P. longuemareus) foraged for nectar throughout the day but collected it illegally by piercing the corollas. In addition, nectar was harvested illegally by four species of stingless bee (Trigona) and by ants, creating a further drain on the limited floral resources.Consideration of the diurnal patterns of foraging activities in combination with a spatial axis (defined here in terms of microclimate and insolation) nevertheless showed a good separation of flower visits for the different nectarivores. Hummingbirds visited flowers in zones where the reward was highest, while insects foraged to minimise their energetic costs; each of these factors could in turn be related to microclimatic considerations. A comprehensive scheme of resource utilisation could therefore be extracted from the field observations and interpreted in these terms. The limited area of niche overlap thus revealed corresponded closely with the situations where direct interference competition was observed, between hummingbird species or between bees and aggressive ants.

Clay Minerals as Influenced by Environments of Their Formation

The potentiality of clay minerals as useful indicators of the environment of their formation is summarized from the published literature on the origin of clay minerals. Caution must be observed when drawing geologic inferences from a rock or mineral concerning its origin because the rock or mineral may not have been formed where it now is found (occurs). Clay minerals are products of parent materials responding to the energy present in the reaction under which they were formed. In the genesis of some minerals the effect of parent material is dominant; in others the controlling factor is environment. The environment of clay mineral formation may be described in part, or vaguely and broadly, in terms of climate as used in the usual sense. The environment is more clearly defined as a chemical micro-climate in terms of concentration of active ions, oxidation potential, and temperature of the reacting systems. This type of environmental description may be related to various geologic domains, such as in the ground-water zone, and under paludal, lacustrine, and marine conditions. The kaolin group of minerals is formed where aluminum silicate rocks react so that the Al to Si ratio is relatively high, H ions are gained, and monovalent and divalent ions are lost. The montmorillonite and illite groups of minerals are formed from aluminum silicate rocks where a relatively high concentration of appropriate metal cations and relatively lower concentration of H ions are maintained. A geologic illustration is cited where clay mineral facies in rocks of Pennsylvanian age in Missouri have been used to infer the geologic environments prevailing during the deposition of the clay minerals.