The ability of a forest to buffer understory temperature extremes depends on the canopy structure, which is often measured from the ground. However, ground measurements provide only point estimates, ...which cannot be used for spatially explicit microclimate modeling. Canopy structures derived from airborne light detection and ranging (LiDAR) can overcome these limitations, but high point-density LiDAR is expensive and computationally challenging. Therefore, we explored whether unmanned aerial systems (UAS) processed with the structure-from-motion (SfM) algorithm could serve as an alternative source of canopy variables for forest microclimate modeling. Specifically, we compared the performance of the canopy cover and height derived from the ground measurements and passive (UAS-SfM) and active (UAS-LiDAR) remote sensing as predictors of air and soil temperature offsets (i.e. differences between the forest understory and treeless areas).
We found that the maximum air temperatures were substantially lower inside than outside the forest, with differences ranging from 9.0 to 12.5 °C. The soil temperatures under the canopy were also reduced, but the soil temperature offsets were lower and ranged from 1.1 to 2.8 °C. The air and soil temperature offsets both increased with increasing tree height and canopy cover. However, the prediction ability of tree height and canopy cover differed if they were ground-based or remotely sensed. The remotely sensed canopy indices explained air temperature offsets better (UAS-SfM: R2 = 0.59, RMSE = 0.75 °C; UAS-LiDAR: R2 = 0.57, RMSE = 0.76 °C) than ground measurements (R2 = 0.51, RMSE = 0.80 °C). Ground-based metrics explained soil temperature offsets better (R2 = 0.37, RMSE = 0.36 °C) than passive remote sensing approach (UAS-SfM: R2 = 0.27, RMSE = 0.39 °C), but comparably to active one (UAS-LiDAR: R2 = 0.35, RMSE = 0.37 °C).
Our results suggest that both UAS-SfM and UAS-LiDAR can substitute ground canopy measurements for air temperature modeling, but soil temperature modeling is more challenging. Overall, our results show that forest microclimate can be modelled at a very high spatial resolution using UAS equipped with inexpensive optical cameras. The increasingly available UAS-SfM approach can thus provide fine-resolution microclimatic data much needed for biologically relevant predictions of species responses to climate change.
•Forest temperature buffering increases with increasing canopy cover and tree height.•UAS remote sensing explains air temperature buffering better than ground measurements.•UAS-SfM predicts air temperature buffering as well as UAS-LiDAR.
This paper differs from conventional science and socially oriented studies of climate by integrating concepts derived from both approaches. Based on interdisciplinary, trans-disciplinary ...multidisciplinary literature review, it defines microclimate and its essences of including natural, social and interactive microclimate from tourism discipline context. For in-depth development of tourism in China under the pressure of tourism supply-side structure revolution, this paper proposes microclimate tourism and analyzes basic on-site microclimate tourism mechanism, basic tourists attractions supply mechanism, and dynamic flows and flexible organisation mechanism of microclimate tourism. For sustainable development, it explores tangible tourists attractions safety, tourists safety and industrial security of microclimate tourism as well as measurements and suggestions for mitigating relative security and safety issues.
•Defining climate and microclimate concept from tourism discipline perspective.•Analyzing microclimate tourism mechanisms in on-site, basic tourists attraction supply, dynamic flow situations.•Analyzing tangible tourists attractions, tourists and industrial security and safety of microclimate tourism.•Proposing measures and suggestions for sustainable development of microclimate tourism security and safety.
This paper discusses current state-of-the-art features of the “plant evaluation model”, a framework which, starting from the representation of vegetation and its effects in microclimate models, ...defines a number of indices which can be employed for the evaluation of outdoor microclimate in terms of thermal environment and comfort in the urban environment. The key point of taking into account the impact of vegetation on microclimate is to implement appropriate parameterizations of such impact in a microclimate model. The paper, based on a review of literature studies, thus illustrates the basic principle and technical path of the impact assessment model of vegetation on microclimate and introduces related software. The aim is to provide the scientific community with a summary of (i) the current definition of vegetation in models employed for the evaluation of the impact of vegetation on urban outdoor microclimate, (ii) main models and evaluation indices and (iii) main input, output, vegetation-related processes implemented, strengths and weaknesses of those models, with suggested measures for output improvement. This review is not exhaustive but may help the user to select the proper model, which takes into account the effects of vegetation on outdoor urban microclimate, depending on the specific objective.
•Benefits on the local microclimate of green roof retrofits are reviewed.•Building energy saving resulting with different extensive green roof retrofits are compared.•The case study of the main ...building of a university campus in Toronto, Canada, is considered.•Results confirm the potential of green roofs as urban heat island mitigation strategies.•Building energy demand reduction by 3% were obtained, mainly through a heating demand reduction.
This paper focuses on the benefits on the local microclimate and the building energy saving resulting from green roof retrofits. The research investigates a case study located in a university campus in Toronto, Canada. After completing a detailed energy audit of the building, an assessment of the benefits resulting from the installation of an extensive green roof was performed. A virtual model validated using multiyear data of a local network of different weather stations was used to simulate the effects of the green roof retrofit over the outdoor microclimate. Then, a building energy model was used to compare the energy saving of several green roof designs. Results indicate that increasing the leaf area index (LAI) would lead to an increased cooling effect of the air temperature up to 0.4°C during the day at pedestrian level, while a more significant temperature reduction would be obtained only at the rooftop level. This confirms the potential of green roofs as urban heat island mitigation strategy. The adoption of a green roof retrofit resulted in a building energy demand reduction by 3%, and in significantly improved indoor comfort levels in the floor below the green roof. Finally, the parametric analysis of different green roof options showed that for building energy savings, increasing the soil depth is more important than increasing the LAI.
► We compared temperature and humidity inside and outside of 14 forest ecosystems. ► Below-canopy microclimate was moderated by up to 5.1°C and 12.4% RH, respectively. ► Moderation depended on forest ...type, altitude, season and general weather situation. ► Below-canopy microclimate did not lag behind open-area microclimate. ► Regeneration in pine and high-altitude forests is most sensitive to climate change.
Forest canopy generally moderates below-canopy air temperature and relative humidity and thus creates a specific microclimate for tree seedling growth. Climate change will alter the moderating capacity, which may render the below-canopy conditions unsuitable for recruitment of the hitherto dominant tree species. We assigned long-term meteorological data (1997–2010) recorded inside and outside of 14 different forest ecosystems in Switzerland to three forest types (broadleaved, non-pine conifer, pine), two altitudinal levels (low, high), the four seasons and general weather situations (normal, hot/dry, cold/wet) to compare moderating capacity of each of these classifiers. Our results confirmed a general moderating effect of canopy on below-canopy microclimate with a decrease of daily maximum air temperature of up to 5.1°C (overall average: 1.8°C) and an increase of daily minimum relative humidity of up to 12.4% (overall average: 5.1%) in the long-term average, respectively. Broadleaved and non-pine conifer forests moderated daytime microclimate about twice as much as pine forests, while at nighttime considerably less cooling down and even negative effects on levels of relative humidity compared to the open area were recorded at the pine forest sites. Moderating capacity was stronger at low altitude than at high altitude. It was strongest during the growing season, particularly in summer, and depended in a complex way on the general weather situation. Deviations from the general seasonal and weather condition patterns most likely occurred when soil moisture pools were depleted. Despite the moderating capacity, below-canopy microclimate did not lag behind open area microclimate. Based on our results we conclude that natural recruitment in pine forests and high-altitude forests may respond most sensitively to climate change.
Forest canopies buffer climate extremes and promote microclimates that may function as refugia for understory species under changing climate. However, the biophysical conditions that promote and ...maintain microclimatic buffering and its stability through time are largely unresolved. We posited that forest microclimatic buffering is sensitive to local water balance and canopy cover, and we measured this effect during the growing season across a climate gradient in forests of the northwestern United States (US). We found that forest canopies buffer extremes of maximum temperature and vapor pressure deficit (VPD), with biologically meaningful effect sizes. For example, during the growing season, maximum temperature and VPD under at least 50% forest canopy were 5.3°C and 1.1 kPa lower on average, respectively, compared to areas without canopy cover. Canopy buffering of temperature and vapor pressure deficit was greater at higher levels of canopy cover, and varied with water balance, implying that buffering effects are subject to changes in local hydrology. We project changes in the water balance for the mid‐21st century and predict how such changes may impact the ability of western US forests to buffer climate extremes. Our results suggest that some forests will lose their capacity to buffer climate extremes as sites become increasingly water limited. Changes in water balance combined with accelerating canopy losses due to increases in the frequency and severity of disturbance will create potentially non‐linear changes in the microclimate conditions of western US forests.
The paper presents the results of a thermal comfort analysis which was carried out in order to investigate the parameters that influence thermal comfort conditions in urban canyon environment. A ...special computational tool was used for the parametric analysis, so that the degree of influence of each parameter could be examined. Also, a thermal comfort analysis was carried out in order to compare conditions in streets in two different sites, a traditional and a contemporary settlement, using input data from experimental measurements carried out in the two sites. The results are compared to shading simulations and thermal analysis results, as well as to experimental measurements results which have been carried out in urban canyons in the two sites.
► We perform a parametric analysis to investigate thermal comfort in urban canyons. ► We investigate the effect of different parameters on thermal comfort outdoors. ► We investigate the differences between a traditional and a contemporary site.
•Drought inhibition on deadwood CO2 efflux increased with drought intensity.•Drought-induced decrease in wood decay is primarily controlled by wood microbes.•Microbial community shifts from bacteria ...to fungi as drought intensity increases.
Climate change has significantly increased the frequency and intensity of drought events in recent decades, which may affect the decomposition of organic matter such as deadwood. Previous studies have examined the impacts of microclimate and wood traits on deadwood decomposition, but how wood microbes regulate effects of drought intensity on deadwood decomposition remains unclear. In this study, a field drought experiment was conducted with three throughfall exclusion levels (i.e., control, −35% and −70% rainfall treatments) in a subtropical forest to probe relative importance of microclimate, wood traits, and microbial biomass on wood decomposition. Our results showed that the −35% and −70% rainfall treatments significantly decreased wood CO2 efflux by 28.27% and 47.49%, respectively. Drought-induced decreases in wood CO2 efflux were mainly mediated by wood microbial biomass, particularly wood fungi biomass. The structural equation modelling indicated a shift in the dominant wood microbial communities in regulating wood CO2 efflux from bacteria to fungi as drought intensities increased. Our findings highlight the crucial role of wood microbial community with the trade-off between fungi and bacteria on deadwood decomposition under drought, which should be taken into account to decode forest carbon cycle − climate feedback in the future research.
Forest canopies buffer macroclimatic temperature fluctuations. However, we do not know if and how the capacity of canopies to buffer understorey temperature will change with accelerating climate ...change. Here we map the difference (offset) between temperatures inside and outside forests in the recent past and project these into the future in boreal, temperate and tropical forests. Using linear mixed-effect models, we combined a global database of 714 paired time series of temperatures (mean, minimum and maximum) measured inside forests vs. in nearby open habitats with maps of macroclimate, topography and forest cover to hindcast past (1970–2000) and to project future (2060–2080) temperature differences between free-air temperatures and sub-canopy microclimates. For all tested future climate scenarios, we project that the difference between maximum temperatures inside and outside forests across the globe will increase (i.e. result in stronger cooling in forests), on average during 2060–2080, by 0.27 ± 0.16 °C (RCP2.6) and 0.60 ± 0.14 °C (RCP8.5) due to macroclimate changes. This suggests that extremely hot temperatures under forest canopies will, on average, warm less than outside forests as macroclimate warms. This knowledge is of utmost importance as it suggests that forest microclimates will warm at a slower rate than non-forested areas, assuming that forest cover is maintained. Species adapted to colder growing conditions may thus find shelter and survive longer than anticipated at a given forest site. This highlights the potential role of forests as a whole as microrefugia for biodiversity under future climate change.
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•Temperature differences inside vs. outside forests were mapped across the globe.•Forest canopies buffer minimum (Tmin), mean (Tmean) and maximum (Tmax) temperatures.•In the future, buffering for Tmean and Tmax may increase, but may decrease for Tmin.•Refugial capacity of forests might last longer than anticipated in a warming world.
