Sunlit Areas Research Articles

Prime Basking Sites and Communal Basking in the Lizard, Lacerta bilineata; High Risk for Juveniles?

Sunlight and the heat it provides are important ecological resources for reptiles especially for those species living in temperate zones that bask extensively to maximize heat uptake. Sun basking has both benefits and costs for reptiles, giving heat that provides the energy to drive physiology but basking in open patches increases risk of predation due to higher visibility. Prime basking sites are believed to increase benefits for reptiles that include, in addition to open sunlit areas, facilitate detection of predators and prey and escape to nearby refuges. However, if such sites are limited, both inter and intra-specific interference may occur and this kind of competition may impact on a reptile’s ability to access prime basking sites, and as a consequence, its capacity to thermoregulate to optimum body temperatures. This may be especially important for juveniles, for whom rapid growth is a key factor in survivorship. We studied communal basking and interaction events at prime basking sites in the European green lizard, Lacerta bilineata, in a hedgerow in western France. We compared basking behaviour of adults and juveniles with sympatric adult wall lizards Podarcis muralis using non-invasive photographic-mark-recapture. Adult L. bilineata were more evenly distributed across basking sights compared to juveniles but significant differences were only detected between males and juveniles. Juvenile L. bilineata abandoned basking sites at the approach of both adult males and females and were aggressively removed by adult male L. bilineata. We found inter-specific communal basking between both adult and juvenile L. bilineata with adult wall lizards P. muralis. Communal basking was observed between male and female L. bilineata but not between adult males or between adult female L. bilineata. Communal basking was in proportionally greater frequency in juveniles compared to adult L. bilineata.

Simulation of light environments inside lunar holes and their associated subsurface caverns

Vertical holes of several tens of meters in diameter and depth have been discovered on the Moon, potentially serving as skylights into subsurface volcanic caverns resembling lava tubes. Because of their scientific importance and potential for use as future lunar bases, these lunar holes and caverns are expected to be targets of intensive exploration in the near future. Using numerical simulations, this study investigates the light environment within a directly and/or indirectly sunlit subsurface cavern accessed through a skylight hole. We specifically analyze the Mare Tranquillitatis Hole (MTH), one of the largest lunar vertical holes, situated near the Moon's nearside meridian. The floor and walls of the hole, and the walls and ceiling of its associated subsurface cavern are lit by reflected sunlight from other parts of the hole and cavern, such as the floors, depending on the solar elevation angle. Furthermore, this paper presents estimation results for camera imaging for a case in which solar elevation angle is 45° in the morning, which is appropriate timing for exploration. Assuming reflectance of 0.1 for the lunar hole and cavern surfaces, we estimate the incident energy onto each pixel of a camera as it descends to the hole's floor. We specifically simulate conditions for a camera with a 12-bit dynamic range, similar to the wide-angle optical navigation camera (ONC-W) onboard the Hayabusa 2 spacecraft. The results suggest that a camera with a fixed gain would struggle to capture both directly and indirectly sunlit areas simultaneously, without saturating bright areas and ensuring minimum incident energy resolution (say, a 10 digital number) for darker areas. To overcome this challenge, adjusting the camera gain based on the hole's and cavern's illumination conditions is necessary.Graphical abstract

Bark beetles on logging residues of European larch: Effects of shading and diameter of logging residues on infestation density

Abstract Ips cembrae, an important pest of European larch (Larix decidua), has caused local outbreaks in the last two decades and is becoming increasingly important as the proportion of European larch in forests increases. In 2021–2023, larch logs and piles of branches were placed into shaded forest and sunlit areas every month to study bark beetle species on logging residues. After adult emergence, the logs and branches were debarked, and the infestation density of bark beetles was analysed. The results indicate that shading, log diameter and top/bottom parts of log had a significant effect on infestation density of I. cembrae on logs. The infestation density of I. cembrae was higher on logs felled between December and June than on logs felled between July and November. Shading of branches was the most significant variable affecting the bark beetle species composition on branches. All four of the bark beetle species recorded were affected by diameter of the branches. Ips cembrae primarily infested sunlit branches while Cryphalus intermedius preferred shaded branches. In contrast, the infestation densities of Pityogenes chalcographus and Pityophthorus pityographus seemed to be affected primarily by moisture content of the branches.

An arrow in the quiver: evaluating the performance of Hyptis suaveolens (L.) Poit. in different light levels

BackgroundHyptis suaveolens (L.) Poit., native to the American tropics, is a pantropical annual plant and a major invasive species throughout India. It was anticipated that the availability of sunlight, coupled with its superior reproductive potential, persistent propagule bank, and dispersal ability, could lead to an increase in the growth and spread of this invader, thus potentially impeding herbaceous growth and diversity in non-native areas. Clarifying its ecological fitness and competitive performance will be useful to manage the spread of H. suaveolens in natural ecosystems that are facing a wide range of anthropogenic pressures.MethodsThe present study is a three-tier experiment. In the first tier, a field study was conducted to assess the patterns of H. suaveolens abundance and herbaceous species diversity in response to light availability (sun, 842–1072 µmol m–2 s−1 and shade 253–341 µmol m–2 s−1) in the tropical dry deciduous ecosystems in the Vindhyan highlands, India. Furthermore, the impact of H. suaveolens abundance on the resident native and non-native species abundance and diversity was also studied. In the second tier, a randomized common garden experiment was conducted to understand the trait fitness of H. suaveolens in sun (940 µmol m–2 s−1) and shade (300 µmol m–2 s−1) conditions. In the third tier, a plant growth chamber experiment with high-light (940 µmol m–2 s−1) and low-light (300 µmol m–2 s−1) treatments was done to learn how H. suaveolens partitions its biomass between aboveground and belowground plant parts.ResultsThe field study indicated that the sunlit areas had a higher abundance of H. suaveolens and a lower diversity of resident herbaceous species than the shaded areas. The common garden experiment showed that sun-dwelling H. suaveolens individuals performed better in germinative, vegetative, eco-physiological, and reproductive traits than the shade-dwelling individuals. The growth chamber experiment exhibited that plants grown in high-light environment had greater seed germination, seedling recruitment, and aboveground biomass than those grown in low-light environment, whereas plants grown in low-light environment exhibited a higher root mass ratio than the high-light individuals. These results suggest that H. suaveolens individuals mask the understory vegetation owing to higher seedling recruitment, relative growth rate, photosynthetic performance, resource acquisition-allocation, and reproductive output in response to high-light conditions.ConclusionsThe study concludes that light significantly controls the invasive population dynamics of H. suaveolens in dry deciduous forests. In high-light areas, H. suaveolens populations dominate the forest understory with suboptimal shade tolerance. In shade environment, H. suaveolens maintains a persistent soil seed bank along with ‘Oskar individuals’ that become active in response to high-light availability. The modus operandi is a ‘sit and wait’ strategy. The current study provides insights on prioritizing areas for H. suaveolens management that will potentially reduce the risk of biological invasions on the native species diversity of tropical regions.

Surface morphology inside the PSR area of lunar polar crater Shoemaker in comparison with that of the sunlit areas

Our study is based on a photogeological analysis of the hill-shade images produced from the LOLA digital terrain models and on a stereometric analysis of LROC NAC images. Our results demonstrate that surface morphology of the permanently shadowed floor of crater Shoemaker is nearly identical to that of the regularly illuminated mare surface at the Lunokhod-2 working area and the surface of the highland plain of the Apollo-16 landing site, being dominated by populations of craters smaller than 1 km in diameters. Craters on the Shoemaker floor have approximately the same depth-to-diameter ratios as those within the Lunokhod-2 and Apollo-16 areas. The observed surface morphology of the Shoemaker floor is the result of meteorite bombardment like in other areas of the Moon. Within the permanently shadowed surface areas we detected no morphological peculiarities that could result from the absence of the diurnal temperature variations that excludes the temperature-related creep component of the downslope material movement. This probably means that in the areas with regular solar illumination, the role of the downslope movement of debris by thermally induced creep mechanisms is secondary compared to shaking by close and distant meteorite impacts and locally by moonquakes.

Three-Dimensional Modeling of Maize Canopies Based on Computational Intelligence.

The 3-dimensional (3D) modeling of crop canopies is fundamental for studying functional-structural plant models. Existing studies often fail to capture the structural characteristics of crop canopies, such as organ overlapping and resource competition. To address this issue, we propose a 3D maize modeling method based on computational intelligence. An initial 3D maize canopy is created using the t-distribution method to reflect characteristics of the plant architecture. The subsequent model considers the 3D phytomers of maize as intelligent agents. The aim is to maximize the ratio of sunlit leaf area, and by iteratively modifying the azimuth angle of the 3D phytomers, a 3D maize canopy model that maximizes light resource interception can be constructed. Additionally, the method incorporates a reflective approach to optimize the canopy and utilizes a mesh deformation technique for detecting and responding to leaf collisions within the canopy. Six canopy models of 2 varieties plus 3 planting densities was constructed for validation. The average R2 of the difference in azimuth angle between adjacent leaves is 0.71, with a canopy coverage error range of 7% to 17%. Another 3D maize canopy model constructed using 12 distinct density gradients demonstrates the proportion of leaves perpendicular to the row direction increases along with the density. The proportion of these leaves steadily increased after 9 × 104 plants ha-1. This study presents a 3D modeling method for the maize canopy. It is a beneficial exploration of swarm intelligence on crops and generates a new way for exploring efficient resources utilization of crop canopies.

A dynamic-leaf light use efficiency model for improving gross primary production estimation

Accurate quantification of terrestrial gross primary production (GPP) is integral for enhancing our understanding of the global carbon budget and climate change. The light use efficiency (LUE) model is undoubtedly the most extensively applied method for GPP estimation. However, the two-leaf (TL)-LUE model using a ‘potential’ sunlit leaf area index (LAIsu) can separate a portion of LAIsu even when the canopy does not receive any direct radiation, leading to the underestimation of GPP under cloudy and overcast days. Here, we developed a dynamic-leaf (DL) LUE model by introducing an ‘effective’ LAIsu to improve GPP estimation, which considers the comprehensive contribution of LAIsu when the canopy does and does not receive direct radiation. In particular, the new model decreases LAIsu to zero when direct radiation reaches zero. Our evaluation at eight ChinaFLUX sites showed that (1) the DL-LUE model outperformed the most well-known BL-LUE (namely, the MOD17 GPP algorithm) and TL-LUE models in reproducing the daily in situ GPP, especially at four forest sites [reducing the root mean square error (RMSE) from 1.74 g C m−2 d−1 and 1.53 g C m−2 d−1 to 1.36 g C m−2 d−1 and increasing the coefficient of determination (R 2) from 0.74 and 0.79–0.82, respectively]. Moreover, the improvements were particularly pronounced at longer temporal scales, as indicated by the RMSE decreasing from 29.32 g C m−2 month−1 and28.11 g C m−2 month−1 to 25.81 g C m−2 month−1 at a monthly scale and from 231.82 g C m−2 yr−1 and 221.60 g C m−2 yr−1–200.00 g C m−2 yr−1 at a yearly scale; (2) the DL-LUE model mitigated the systematic underestimation of the in situ GPP by both the TL-LUE and BL-LUE models when the clearness index (CI) was below 0.5, as indicated by the Bias reductions of 0.25 g C m−2 d−1 and 0.46 g C m−2 d−1, respectively; and (3) the contributions of the shaded GPP to the total GPP from the DL-LUE model were higher by 0.07–0.16 than those from the TL-LUE model across the eight ChinaFLUX sites. The proposed parsimonious and effective DL-LUE model not only has great potential for improving global GPP estimations but also provides a more mechanism-based approach for partitioning the total GPP into its shaded and sunlit components.

Epibiont of venus clam (Gafrarium tumidum) shells: a study on Pari Island, Seribu Islands

Molluscs play a crucial role as ecosystem engineer by providing habitat for other organisms. However, little is known about the shells’ ability to host other species, especially in tropical ecosystems like Pari Island. In sandy locations, hard substrates are scarce, but clam shells introduce substrate heterogeneity. Our study focused on the Venus Clam (Gafrarium tumidum), prevalent in the seagrass bed ecosystem on Pari Island, to explore the epibiont species residing on its shells. Epibionts were examined through visual observation and microscopy analysis in a laboratory. We found the attached epibionts were categorized into three main groups. The first group was macroalgae, specifically Padina sp., which attached to the posterior part of the clam shell, relying on stable substrates to withstand waves. The second group encompassed microalgae, including Bacillaria, Nitzchia, Prorocentrum, Pseudo-nitzschia, Surirella, and Trichodesmium. These microalgae have diverse ecological roles, including causing harmful algal blooms and nitrogen fixation. The third group consisted of possibly cyanobacteria forming blue-green biofilms on clam shells, predominantly on recently deceased or living clams, mainly in exposed, sunlit areas. This research emphasizes the significant role of clam shells in supporting epibiont species richness in the ecosystem.

The effects of warm weather on children’s outdoor heat stress and physical activity in a preschool yard in Gothenburg, Sweden

Hot weather conditions can have negative impacts on the thermal comfort and physical activity of vulnerable groups such as children. The aim of this study is to analyze the effects of warm weather on 5-year-old children’s thermal comfort and physical activity in a preschool yard in Gothenburg, Sweden. In situ measurements were conducted for 1–1.5 h in the early afternoon on 8 days in May, June, and August of 2022. The thermal comfort and physical activity was estimated with GPS-tracks, heart rate monitors, and step counts and compared to observed weather conditions. Results show that physical activity decreases under warmer weather conditions, depicted by a decrease in distance moved, step counts, and highest registered pulse. Moreover, on warm days, the children avoid sunlit areas. For 50% or more of the time spent in sunlit areas, the children are exposed to cautious levels of heat. In shaded areas, on the other hand, the children are less exposed, with five out of 8 days having 50% or more of the time at neutral levels. The study demonstrates the importance of access to shaded areas in preschool yards where children can continue their active play while simultaneously maintaining a safe thermal status.

Sverdrup-Henson crater: A candidate location for the first lunar South Pole settlement

Robotic and manned exploration of the Moon is the next target in Solar System exploration. The availability of in situ resources such as water ice, iron oxides, helium-3, and rare earth elements, combined with permanently sunlit areas, provides the opportunity for the first settlement, either human or robotic, on the Moon. We used several selection criteria (abundance of water ice, the slope of terrain, usable energy sources, communications, and base expandability) to identify a suitable area for a future base in the southern polar crater Sverdrup-Henson. Due to the higher abundance of water ice, we found that the Sverdrup-Henson site is better suited to host a base than the nearby craters de Gerlache and Shackleton. The crater floor is partly in permanent shadow and exhibits numerous signatures of water ice. Since water ice is essential for rocket fuel production and human survival, its presence is necessary for a first settlement. Sverdrup-Henson has a flat floor ideal for building and safe traversing, is accessible from the surrounding intercrater plains, and has nearby locations suitable for communications and solar power production. Thus, the Sverdrup-Henson site holds great potential for future missions. We propose further exploration of this area through in situ measurements to better constrain available resources.

New Method for Fine Calculation of Bridge Temperature Field Based on BIM Solar Radiation Analysis

Fine calculation of bridge temperature fields is significant for accurately evaluating thermal actions in bridge structures. Determining thermal loads on bridge surfaces caused by solar radiation is the most challenging part of the numerical thermal analysis because the sunlit and shaded areas on bridge surfaces change continuously with the sun’s rotation. Existing methods have low accuracy in determining thermal loads and cannot be applied to complex bridges. This study presents a new method for calculating temperature fields based on the advantages of building information modeling (BIM) technology in solar radiation analysis (SRA) and information sharing. This method starts with obtaining an accurate hourly insolation distribution on bridge surfaces through SRA implemented in a BIM system. Then, a Python script seamlessly maps the insolation information to finite element surfaces as thermal loads. This paper details the new method’s implementation steps and technical details, and a practical application on a concrete box girder demonstrates its applicability and effectiveness. Compared with previous methods, the proposed method has significant advantages, such as a more accurate calculation for solar radiation, a lower technical threshold, a higher degree of automation, less computational time, and easier finite element modeling.

Refined 3D Solar Temperature Field and Effect Simulation of Ultra-High Steel Bridge Pylon

In order to accurately calculate the sunshine-induced temperature effect of an ultra-high bridge pylon, a refined numerical simulation model for the 3D bridge temperature field was established based on the proposed automatic sunshine shadow recognition method and pylon-height-related convection modification method. A suspension bridge H-shaped pylon with a height of 280 m was taken as an example, and the temperature field and corresponding thermal stress and deformation were calculated under typical meteorological conditions in spring, summer, autumn, and winter. The results show that the maximum temperature differences between the outer surfaces of the pylon can reach 19 °C and 16 °C for north–south walls and east–west walls, respectively, and exceed the recommended value of ±5 °C in the Chinese Specification. The maximum displacements can reach 370 mm and 110 mm at the top of the bridge pylon in the longitudinal and transverse directions of the bridge, respectively. After the modification of the convective coefficient of the outer surfaces with different wind speeds at different pylon heights, the temperature gradually decreased from the top to the bottom of the pylon, with a temperature difference of 8 °C. The significant influence of the sunshine shadow was shown on the temperature field and temperature effect of the bridge pylon. By considering the shadow effect, the maximum temperature difference can reach 12 °C between adjacent sunlit and shaded areas and can reach 14 °C between two pylon columns. A significant mutation of thermal stress existed in the shaded area, and the maximum stress could be reduced by 13 MPa compared with the adjacent sunlit area. Obvious asynchronous deformation was shown between two pylon columns, and the maximum asynchronous displacement at the top of the pylon can reach 18 mm and 45 mm in the longitudinal and transverse directions, respectively.

Illumination conditions near the Moon's south pole: Implication for a concept design of China's Chang’E−7 lunar polar exploration

Volatiles including water on the Moon has been one of the most interesting scientific objects for decades. In this study, we systematically introduced a concept for China's Chang’E−7 (CE-7) lunar polar exploration mission which consists of five elements, the orbiter, lander, rover, and leaper, and one relay satellite. The orbiter will provide a high-resolution image preparing for landing site selection. We also proposed three phases for in-situ investigation after landing. (1) The rover and leaper will jointly investigate the sunlit area; (2) the leaper will explore cold traps; and (3) the leaper will fly back to the sunlit area and continue an extended exploration mission. An experimental penetrator launched by the lander will penetrate permanently shadowed crater walls for water ice detection. Data will be transmitted to Earth through the relay satellite due to the limited Earth visibility. We also calculated the illumination rate within a 15 × 15 km area that partially covers the Shackleton crater at a high spatial resolution of 20 m/pixel during lunar southern summer. Specifically, we compared two potential landing sites with accumulated illumination at different altitude levels, slopes, and distances to the target. We found that one part of the Shackleton crater rim can be a primary landing site for CE-7's both sunlit areas and cold trap explorations.

A fully automatic method for segmentation of soccer playing fields

This paper proposes a strategy to segment the playing field in soccer images, suitable for integration in many soccer image analysis applications. The combination of a green chromaticity-based analysis and an analysis of the chromatic distortion using full-color information, both at the pixel-level, allows segmenting the green areas of the images. Then, a fully automatic post-processing block at the region-level discards the green areas that do not belong to the playing field. The strategy has been evaluated with hundreds of annotated images from matches in several stadiums with different grass shades and light conditions. The results obtained have been of great quality in all the images, even in those with the most complex lighting conditions (e.g., high contrast between sunlit and shadowed areas). In addition, these results have improved those obtained with leading state-of-the-art playing field segmentation strategies.

Living in a Thermally Diverse Environment: Field Body Temperatures and Thermoregulation in Hermann’s Tortoise, Testudo hermanni, in Montenegro

Reptiles live in a range of different habitats from tropical forests to temperate zones where the climate may change on seasonal or a daily basis. The thermal environment is a major determinant of how efficiently they can achieve optimum or preferred body temperatures and, in terms of physiologically optimum body temperatures, these may not be possible in a natural environment. In this paper, null models have been employed to evaluate thermoregulatory efficiency in Hermann’s tortoise, Testudo hermanni, in high summer in central Montenegro when temperatures change on a daily basis. The study area is defined as a low-cost thermal environment and thus we assumed that tortoises should be able to achieve an efficient level of thermoregulation. However, the results varied and depended on where the tortoises operated and the weather conditions. High levels of efficiency were found during sunny weather in areas with abundant patches of shade and sunlit areas. These reflected the temperatures of models placed in these areas and in females during cooler cloudy weather when thermoregulatory effort increased. Model temperatures placed in partially shaded sunlit areas were in better agreement with tortoise body temperatures than models in other areas. Tortoise body temperatures were in closer agreement with set point temperatures than any of the null models placed in either open sunny, shaded or partially shaded areas, indicating that tortoise movement was non-random and due to active thermoregulation.

Thermal Infrared Radiative Transfer Modeling in Urban Areas by Considering 3-D Structures and Sunlit–Shadow Temperature Contrast

Land surface temperature (LST) is a crucial parameter needed to study the thermal environment in urban areas. Currently, it can be restored from thermal infrared (TIR) measurements based on various LST retrieval algorithms. But the expected urban LST retrieval accuracy of <1 K is difficult to achieve because knowledge is lacking on how to correct the impact from the surface 3-D structures and the sunlit-shadow temperature contrast. Although an Analytical TIR radiative transfer Model Over Urban area (ATIMOU) has been proposed, the temperature contrast between sunlit and shadowed areas has been not well managed yet, thus lead to its inapplicability in daytime TIR observations. This study develops an Extended ATIMOU (E_ATIMOU) that considers the impact from both 3-D structures and sunlit-shadow temperature contrast. According to the simulations based on E_ATIMOU, if such impact is not properly accounted for, a 4.43 K bias can be potentially introduced to the ground brightness temperature of a street canyon under the condition of wavelength of 10 μm, ratio “sunlit-road area/total-road area” of 0.5, shadowed wall and road temperature of 300 K, and the sunlit-shadow temperature contrast of 5 K, which emphasizes the necessity of addressing this impact during the LST retrieval in urban areas. Moreover, E_ATIMOU has also been validated by intercomparing with the discrete anisotropic radiative model (DART). The discrepancy between the two models for the calculated ground brightness temperatures is found to be <0.1 K for various urban scenarios, indicating that the E_ATIMOU is in good agreement with DART.

Giga-year dynamical evolution of particles around Mars

Particles of various sizes can exist around Mars. The orbits of large particles are mainly governed by Martian gravity, while those of small particles could be significantly affected by non-gravitational forces. Many of the previous studies of particle dynamics around Mars have focused on relatively small particles (radius of rp≲100μm) for ≲104 years. In this paper, using direct numerical orbital integration and analytical approaches, we consider Martian gravity, Martian J2, the solar radiation pressure (SRP) and the Poynting–Robertson (PR) force to study the giga-year dynamical evolution of particles orbiting near the Martian equatorial plane with radius ranging from micrometer to meter. We also newly study the effect of the planetary shadow upon the particle dynamics. Our results show that small particles (rp≲10μm) initially at ≲8 Martian radii (below the orbit of today’s Deimos) are quickly removed by the SRP due to eccentricity increase, resulting in a collision with Mars at the pericenter distance. The orbits of larger particles (rp>10μm) slowly decay due to the PR forces (timescale of >104 years). The planetary shadow reduces the sunlit area in the orbit and thus the efficiency of the PR drag force is reduced. However, we show that, even including the planetary shadow, particles up to ∼10 cm in radius, initially at ≲8 Martian radii, eventually spiral onto the Martian surface within ∼109 years. Smaller particles require less time to reach Mars, and vice versa. Our results would be important to better understand and constrain the nature of the remaining particle around Mars in a context of giant impact hypothesis for the formation of Phobos and Deimos.

Open habitats increase vulnerability of amphibian tadpoles to climate warming across latitude

AbstractAimGlobal warming and deforestation are pushing species closer to their physiological limit, especially for species with habitat‐restricted life stages because sunlit areas have higher maximum temperatures. Here, we examined the critical thermal maximum (CTmax), and maximum environmental water temperature (Tmax) of larvae from 29 anuran species across a latitudinal gradient (22–43° N) to test how latitude and habitat type (open or closed‐forest ponds) affected warming tolerance, an index of vulnerability to climate change.LocationTaiwan, Korea, Japan.Time periodPresent.Major taxa studiedAnurans.ResultsWe showed that open ponds lowered warming tolerance, regardless of latitude and phylogenetic clustering, contrasting the established literature that warming tolerance is lower at tropical latitudes, which only applied to species in forest ponds in this study. Importantly, biophysical models at the local scale suggest that increasing deforestation will exacerbate the effects of climate warming on warming tolerance.Main conclusionsLocal effects of accelerated warming and habitat modification mean that species with range‐restricted life stages will become more vulnerable to anthropogenic change.

Locating trees to mitigate outdoor radiant load of humans in urban areas using a metaheuristic hill-climbing algorithm – introducing TreePlanter v1.0

Abstract. Mean radiant temperature (Tmrt) is a frequently used measure of outdoor radiant heat conditions. Excessive Tmrt, linked especially to clear and warm days, has a negative effect on human wellbeing. The highest Tmrt on such days is found in sunlit areas, whereas shaded areas have significantly lower values. One way of alleviating high Tmrt is by planting trees to provide shade in exposed areas. Achieving the most efficient mitigation of excessive Tmrt by tree shade with multiple trees requires optimized positioning of the trees, which is a computationally extensive procedure. By utilizing metaheuristics, the number of calculations can be reduced. Here, we present TreePlanter v1.0, which applies a metaheuristic hill-climbing algorithm on input raster data of Tmrt and shadow patterns to position trees in complex urban areas. The hill-climbing algorithm enables dynamic exploration of the input data to position trees, compared with very computationally demanding brute-force calculations. The hill-climbing algorithm has been evaluated with a static greedy algorithm that positions trees one at a time based on ranking and is expected to always find relevant locations for trees. The results show that the hill-climbing algorithm, in relatively low model runtime, can find positions for several trees simultaneously, which lowers Tmrt substantially. TreePlanter, with its two algorithms, can assist in optimization of tree planting in urban areas to decrease thermal discomfort.

Characterizing spatiotemporal variations of forest canopy gaps using aerial laser scanning data

Spatiotemporal variations of forest canopy gaps are essential indicators for both forest dynamic monitoring by capturing their size and location variations and forest ecosystem management for tree seedling regeneration through altering the radiation regime within and under forest canopies. To differentiate the effects of forest canopy gaps on forest three-dimensional (3-D) structure and direct incoming solar radiation, we proposed two novel concepts named physical forest canopy gap (PCG) and physiological forest canopy gap (POCG). Using aerial laser scanning (ALS) data, this study developed ALS-based methods of extracting and characterizing spatiotemporal variations of the PCG and POCG in a natural homogeneous forested area. The ALS-based PCG and POCG results were validated using visual-based interpretation and field-measured data, respectively. The overall accuracy was all over 0.80 and Kappa coefficients all over 0.70 for PCG extraction. The coefficient of determination between the ALS-based POCG area and field-based one was 0.86 (n = 16, p < 0.01), and the root mean square error was 16.28 m2. Spatiotemporal variations of forest canopy gaps included variations of their sizes and locations and the sunlit areas within them. This study provided a solid foundation for forest dynamic monitoring and forest ecosystem management.