Microclimatic Differences Research Articles

Zonal classification of microclimates and their relationship with landscape design parameters in an urban park

Microclimates in urban areas arise through the interaction between prevailing weather conditions and landscape design parameters. A well-arranged landscape creates a pleasant outdoor environment. Additionally, the classification of microclimates helps to illustrate variations therein and analyze influencing factors. This study classified microclimate zones (MZs) based on a statistical method and identified influential landscape design parameters with the aim of enhancing human comfort. We conducted our study at Yeouido Park in Seoul, Korea, which has various landscape design parameters, including tree canopy cover and ground surface type. A novel MZ classification method was developed in this study, then stepwise regression was used to analyze the relationship between microclimate and landscape design parameters. It was found that the MZ classification effectively demonstrated spatial microclimatic differences and characteristics on a park scale. The efficiency with which trees improved the microclimate depended on the ground surface type. However, the significant effects of landscape design parameters on the microclimate and human comfort differed by season and time of day. This study provides a statistical method for analyzing an urban microclimate and serves as a reference regarding how to effectively modify the meteorological environment on a microscale via landscape design, in both summer and winter urban outdoor spaces.

Climate preconditions the Critical Zone: Elucidating the role of subsurface fractures in the evolution of asymmetric topography

Although it has been long understood that rock properties strongly modulate the chemical and physical transformation of rock to regolith, recent studies highlight the central role of mechanical fracturing in the shallow subsurface. Competing hypotheses for how fractures co-evolve with surface processes suggest either that topographic stresses enhance or dampen the potential for fracture propagation, or alternatively suggest that fracture growth depends on the coupling between subsurface hydrology and weathering reactions. Both end-member models produce predictable and systematic spatial patterns of subsurface fracture distributions.To elucidate the processes responsible for the development of asymmetric hillslope topography and critical zone structure, we combine direct observations of subsurface fracture distributions in boreholes, indirect measures of subsurface rock properties inferred from seismic refraction surveys, and geochemical variations from subsurface samples at a small, shale-underlain catchment in central Pennsylvania. Our results reveal that seismic P-wave velocity profiles are consistent with subsurface fracture densities and zones of chemical depletion observed in boreholes, but that these distributions co-vary with hillslope aspect. Simple models of frost cracking show that, while modern climates are not conducive to subsurface segregation ice growth, asymmetric fracture distributions could have been achieved by subtle differences in aspect-related microclimates driving freeze-thaw during past periglacial climates. The spatial co-variance among fracture density, hillslope gradient, regolith depth, and regolith transport efficiency is consistent with chemo-mechanical damage arising from microclimatic conditions governing the long-term architecture of this watershed. Thus, damage driven by climate could explain the asymmetric topography observed today.

The Iowa Atmospheric Observatory: Revealing the Unique Boundary Layer Characteristics of a Wind Farm

Abstract The Iowa Atmospheric Observatory was established to better understand the unique microclimate characteristics of a wind farm. The facility consists of a pair of 120-m towers identically instrumented to observe basic landscape–atmosphere interactions in a highly managed agricultural landscape. The towers, one within and one outside of a utility-scale low-density-array wind farm, are equipped to measure vertical profiles of temperature, wind, moisture, and pressure and can host specialized sensors for a wide range of environmental conditions. Tower measurements during the 2016 growing season demonstrate the ability to distinguish microclimate differences created by single or multiple turbines from natural conditions over homogeneous agricultural fields. Microclimate differences between the two towers are reported as contrasts in normalized wind speed, normalized turbulence intensity, potential temperature, and water vapor mixing ratio. Differences are analyzed according to conditions of no wind farm influence (i.e., no wake) versus wind farm influence (i.e., waked flow) with distance downwind from a single wind turbine or a large group of turbines. Differences are also determined for more specific atmospheric conditions according to thermal stratification. Results demonstrate agreement with most, but not all, currently available numerical flow-field simulations of large wind farm arrays and of individual turbines. In particular, the well-documented higher nighttime surface temperature in wind farms is examined in vertical profiles that confirm this effect to be a “suppression of cooling” rather than a warming process. A summary is provided of how the wind farm boundary layer differs from the natural boundary layer derived from concurrent measurements over the summer of 2016.

Floristic and microclimatic features of the Sovljak doline (Mt. Velika Kapela, Croatia)

The relation between floristic composition, microclimate and geomorphology of a large-sized karst doline was analysed in the area of the Sovljak doline located on the Mt. Velika Kapela. Habitat conditions in various parts of the doline, due to its morphology, were described in this work. Geomorphological observations, microclimatic measurements (including air temperature, relative humidity and dew point temperature data) and flora inventory were carried out. Ellenberg’s indicator values, life forms, chorological and taxonomical analyses were performed, as well as the analysis of habitat similarity. The doline slopes (northern and southern) appeared to offer different habitat conditions than its bottom, due to their morphological and microclimatic differences, which resulted in high taxa variability along short distances in the doline. Furthermore, the presence of temperature inversion promoted the development of the vegetation inversion, which is common in such large dolines.

Seasonal microclimatic variation in a succession gradient of low thorn forest in Northeastern Mexico

Global increase in land cover change and deforestation bring about fragmentation of a high proportion of native vegetation areas. Microclimate is among the first modified factors after vegetation loss, effects of such disturbances are critical for species performance. However, both secondary succession and seasonality provoke further modifications in abiotic environment after disturbances. Although microclimate patterns during succession are well studied for several ecosystems, they are practically unknown for low thorn forests. In Northern Mexico, this is an endangered ecosystem characterized by harboring a high percentage of endemics. Measurement of microclimatic factors is crucial for understanding possible consequences of post-disturbance time on species inhabiting this ecosystem. This work aimed to assess seasonal variation of microclimatic patterns in a succession gradient of four categories (conserved areas, 31, 17 and four years of succession). The study area was delimited using Landsat satellite images (1973, 1986, 2000, 2005, and 2013) in a fragment of low thorn forest in Northeastern Mexico. For microclimate characterization we studied wind speed, temperature, relative humidity, heat index, dew point, and evapotranspiration. Variables were measured monthly on eight plots, in each of the four successional categories, during two different seasons: wet (May through October 2016) and dry season (November 2016 through April 2017). A multivariate discriminant function analysis showed that microclimate differs among successional stages. In the wet season, early succession areas were characterized by higher values of heat index and wind speed, contrary to conserved areas. In the dry season, successional differences were attributed to wind speed and relative humidity. Moreover, microclimate differences between categories and importance of variables measured were both higher only during the dry season. Our results show that seasonality influences greatly microclimatic patterns during secondary succession. In addition, each one of the successional categories exhibited unique microclimatic conditions. Remarkably, four, 17, and even 31 years succession categories differed from conserved areas. This work provides evidence on the great relevance of seasonality and microclimate for studying secondary succession. It is suggested to take both factors into consideration when implementing conservation programs concerning endangered habitats such as low thorn forests. As an ecosystem poorly studied, microclimate characterization provided herein, shall help to a better understanding and management of these areas.

Water use of Coffea arabica in open versus shaded systems under smallholder’s farm conditions in Eastern Uganda

Coffee cultivation is a major source of income in East Africa. Increasing temperatures and water scarcity related to climate change are becoming major challenges for coffee production. Therefore, there is an urgent need for sound scientific understanding of the functioning of current coffee cultivation systems and the potential of agroforestry as an adaptation strategy to climate change. In a smallholder coffee farm on Mt Elgon, Uganda, we assessed the effect of three coffee cultivation systems (i.e., Coffee-Open, Coffee-Banana and Coffee-Cordia) on (i) the coffee cultivation environment (e.g. microclimate and soil moisture), (ii) water consumption of coffee, (iii) water consumption of banana (Musa sp.) and Cordia africana and (iv) water competition or complementary use between coffee and shade tree species. To this end, we monitored sap flux density (Js) (g cm−2 hour-1) of coffee, banana and C. africana from March 2015 to April 2016, using Granier thermal dissipation method, along with microclimate, soil moisture and rainfall. Shaded systems reduced irradiance by 70% in Coffee-Cordia system and 58% in Coffee-Banana system compared to Coffee-Open system. Maximum temperatures and daily temperature amplitude were on average reduced by 4 °C in both shaded systems compared to Coffee-Open system. Soil water content (SWC) in shaded systems was reduced by 59% in Coffee-Cordia and 6% in Coffee-Banana compared to Coffee-Open. Daily water consumption of coffee plants was 1.2 ± 0.64 l d-1 and did not differ between systems. Water use of banana was 3.1 ± 1.8 l d-1 and 42 ± 40 l d-1 by C. africana. Coffee-Banana system had the largest daily transpiration rate, 0.9 ± 0.4 mm d-1 per ground area and 0.6 ± 0.4 mm d-1 per unit leaf area, followed by Coffee-Cordia with 0.37 ± 0.1 mm d-1 (per ground area), 0.36 ± 0.1 mm d-1 (per leaf area) and Coffee-Open 0.24 ± 0.1 mm d-1 (per ground area), 0.27 ± 0.1 mm d-1 (per leaf area). Our results showed that differences in microclimate and SWC between cultivation systems did not influence coffee water use during the monitored year. However, water competition between coffee and shade trees could likely occur in drier years, due to the reduced SWC presently observed in shaded systems. Further research is needed to explore the performance of management practices (mulching, pruning and thinning) in interaction with seasonal weather forecast and appropriate selection of shade species (provision of extra products, reduced water use, fast growth and root zone below 80 cm depth) to match the systems’ water requirements with expected soil water availability.

Optimizing Design Layout of a Riverside Residential Settlement in terms of the Thermal Comfort

The thermal comfort of a riverside residential settlement differs from a non-riverside residential one, which might be caused by a microclimatic difference. Inducing wind from a river to cross the whole riverside residential settlement could improve the outdoor thermal comfort significantly. Such knowledge triggers a study of utilizing river wind to enhance thermal comfort to a riverside residential settlement in southern China. The study explores various possible layouts of a riverside residential settlement using Computational Fluid Dynamic (CFD) simulations. The thermal comfort index OUT_SET* (the Standard Effective Temperature) that combines effects of air temperature, radiation, wind velocity, and the water evaporation, has been used to evaluate thermal comfort of various riverside residential settlements due to different design layouts. The result showed that the loose enclosed layout is the best one for the thermal comfort whereas the back and front aligned determinant layout is the worst. In order to apply the results into a real world, a case study has been made to the Shenzhen Nan Hua Cun. The thermal environment of this Chinese southern riverside residential settlement has been researched. According to thermal problems revealed by CFD simulation, an optimization design layout was proposed by applying the study results. Eventually, the thermal comfort between the current situation and the optimization design has been compared.

Possibilities for improvement of environmental monitoring of precipitation in the city (a case of Lutsk)

Formulation of the problem. The environmental parameters of precipitation in the city often differ from the background values and require the special observations program. The existing state monitoring system does not reflect the spatial differentiation of such parameters in urban areas, so it needs to be improved. The purpose of the article: to find out the features of organization and implementation of rainfall environmental monitoring in urban areas, with the justification of the main parameters of observation and spatial placement of network points. Methods. The main results are based on the authors' experience in own observations on the amount, acidity and mineralization of precipitation in several quarters of Lutsk during 2015-2018. Results. Own observations and mapping of individual parameters of atmospheric precipitation in the city allowed to reveal the dependence of the indexes of acidity and mineralization on the amount of precipitation, air pollution, directions of air inflow, temperature, etc. The spatial differentiation of these indicators in the city is significant (the amplitude can reach up to 0.9 units of pH and 15-17 ppm of tds) and is related to the distribution of anthropogenic emissions and some microclimatic differences. Therefore, by organization the system of ecological monitoring of precipitation in the city it is necessary to focus on the definition of such basic parameters: pH, total mineralization, amount of precipitation, and also concomitant: water and air temperature, direction of airflows, carbon dioxide concentration, duration of the previous rainless period, etc. To select the representative locations for the control of precipitation in the city, it is necessary to analyze the following indicators: direction of prevailing winds, landscape and geomorphological features, the proximity of the most sources of anthropogenic contamination, building types etc. In this case, the minimum monitoring scheme should include such control points: the near and far outskirts (in relation to the arrival of prevailing air masses), the leeward sides of large industrial zones or transport interchanges, the largest green zone, area near the city water body, and several points (1-3) in residential areas. Scientific novelty and practical significance. The main parameters and principles of the spatial organization of environmental monitoring of rainwater in the city are identified. The algorithm for creation such network has been tested in Lutsk and can be used for realization in other cities. Automation of similar measurements based on microcontrollers will to create quality non-state monitoring networks with the display of data in real time.

Climatic Conditions of Steppe and Tundra Formations in the Altai Highland Depressions

«Вестник Санкт-Петербургского университета. Науки о Земле» — научно-теоретический рецензируемый журнал, обобщающий результаты исследований в области геологии, гидрогеологии и геохимии, петрологии и экологии, ландшафтного планирования и геоморфологии, экономической и социальной географии.

Phenological synchrony between eastern spruce budworm and its host trees increases with warmer temperatures in the boreal forest.

Climate change is predicted to alter relationships between trophic levels by changing the phenology of interacting species. We tested whether synchrony between two critical phenological events, budburst of host species and larval emergence from diapause of eastern spruce budworm, increased at warmer temperatures in the boreal forest in northeastern Canada. Budburst was up to 4.6 ± 0.7 days earlier in balsam fir and up to 2.8 ± 0.8 days earlier in black spruce per degree increase in temperature, in naturally occurring microclimates. Larval emergence from diapause did not exhibit a similar response. Instead, larvae emerged once average ambient temperatures reached 10°C, regardless of differences in microclimate. Phenological synchrony increased with warmer microclimates, tightening the relationship between spruce budworm and its host species. Synchrony increased by up to 4.5 ± 0.7 days for balsam fir and up to 2.8 ± 0.8 days for black spruce per degree increase in temperature. Under a warmer climate, defoliation could potentially begin earlier in the season, in which case, damage on the primary host, balsam fir may increase. Black spruce, which escapes severe herbivory because of a 2‐week delay in budburst, would become more suitable as a resource for the spruce budworm. The northern boreal forest could become more vulnerable to outbreaks in the future.

The impact of local variations in a temperate maritime climate on building energy use

ABSTRACTWe investigate the impact of local climatic variations on the energy performance of buildings by conducting simulations using weather files generated from high-resolution measurements covering 33 stations within a 77 km2 area in southern Vancouver Island, British Columbia, Canada. Weather files were created by resampling the data and applying appropriate models to obtain unmeasured values. The difference in microclimate has been analysed statistically and graphically; average annual temperature varies by around 1°C, and at certain times there is a 6°C variation across the (very small) region.Building energy simulations of a small naturally ventilated office building and a larger air-conditioned building were performed using EnergyPlus for all weather files. Significant variation is found spatially and temporally which would have substantial implications for building design and energy use. The variation in annual heating energy use is ±5% of the mean, equivalent to 18 kWh/m2/a, with even greater relative variation in cooling energy use.

Lower temperatures decrease worker size variation but do not affect fine-grained thermoregulation in bumble bees

Phenotypic variation within biological systems is ubiquitous and often assumed to be adaptive in social insects. Local environmental factors, such as temperature, may affect the phenotypic variation produced, and yield insights into the mechanisms that generate this group-level outcome. For instance, fine-scale heterogeneity in temperature across the nest may generate phenotypic variation by affecting larval development directly, or indirectly by inducing changes in the behavior of group members. To understand the role of temperature in producing phenotypic variation, we studied whether microclimatic differences within the nest could produce the worker size variation commonly observed in bumble bee (Bombus impatiens) colonies. We also tested if changes to the ambient temperature that colonies are exposed to influences the size variation they produced. We recorded brood temperature via thermal imaging and measured thorax widths of workers produced by colonies kept at ambient temperatures of 30 and 20 °C. Overall, average brood temperature did not differ across the nest even while the average temperature of non-brood structures (i.e., honeypots) interspersed among the brood decreased towards the periphery, demonstrating that bees were able to regulate brood temperature at a fine scale. However, we found that the size variation produced was sensitive to ambient temperature and increased under warmer temperatures. These results demonstrate that bumble bees have a unique method of fine-grained thermoregulation, where they regulate brood temperature but not the regions between brood. Additionally, while temperature is not the mechanism that produces size variation, it indirectly influences the mechanism that does. Morphological variation among group members affects group performance. We studied how the thermal environment experienced by developing workers, i.e., brood, influences the between-worker size variation produced within B. impatiens colonies. We found that temperature only indirectly influences size variation, as size variation increased under warmer nest temperatures, yet the temperature of brood did not differ across the nest. Our finding that workers maintain a uniform environment for the brood differs from previous results examining feeding rates across the nest and suggests that while the same workers tend to feed and thermoregulate the brood, they do so according to different rules and that by influencing worker behaviors, such as feeding rate, temperature affects size variation.

Sun and shade leaf variability in Liquidambar chinensis and Liquidambar formosana (Altingiaceae): implications for palaeobotany

Many factors influence leaf anatomy and morphology in the crown of a tree, particularly those resulting from microclimatic differences between the periphery and the interior of the crown. These influences can be so strong that single species can produce different leaf forms in which shade and sun leaves exhibit consistently distinctive morphological and epidermal character sets. Here we show, using Liquidambar as a model system, that the principal morphological characters for distinguishing shade and sun leaves in two modern Liquidambar spp. with different lamina types (entire in L. chinensis and lobate in L. formosana) are the leaf lamina length to width ratio, the degree of development of venation networks, tooth size and tooth shape. The main epidermal characters are ordinary cell size and anticlinal wall outlines. Many fossils, however, are only preserved as impressions and morphological characters alone have been used to distinguish shade and sun leaf morphotypes. To evaluate the utility of our approach, populations of fossil Liquidambar leaves from the Eocene of southern China, preserved only as impressions, were categorized into sun and shade morphotypes. Recognition that sun and shade leaf morphological diversity exists in fossil populations will enable palaeobotanists to identify more reliably foliar polymorphisms that would otherwise be used to describe, incorrectly, different species.

Assessing spider diversity in grasslands – does pitfall trap color matter?

We analyzed effects of pitfall trap color on spider catches using four different pitfall trap colors (white, yellow, green, brown). For each color, we installed 17 pitfall traps at two grassland sites, respectively, and sampled 77 species from 6,202 individuals. Number of species showed no significant differences but Shannon- and Simpson-diversity were significantly higher in green and brown traps while number of individuals increased in white ones. Species inventories were not complete in the different pitfall trap colors but species accumulation increased significantly slower in white and brown traps. Trap color significantly affected hunting type with ground hunters being associated with bright and web-builders associated with dark colors. Attractiveness of different trap colors may arise due to differences in biological preconditions, albedo and microclimate which in turn can affect diversity and community structure of spiders. Trap color has a significant impact on spider catches and should be considered when planning surveys. We recommend the use of a combination of white and brown (or transparent) pitfall traps to gain complete and diverse species inventories in spiders.

Water- and Nitrogen-Use Efficiencies of Hemp (Cannabis sativa L.) Based on Whole-Canopy Measurements and Modeling.

Interest in hemp (Cannabis sativa L.) as a crop for the biobased economy is growing worldwide because hemp produces a high and valuable biomass while requiring low inputs. To understand the physiological basis of hemp's resource-use efficiency, canopy gas exchange was assessed using a chamber technique on canopies exposed to a range of nitrogen (N) and water levels. Since canopy transpiration and carbon assimilation were very sensitive to variations in microclimate among canopy chambers, observations were adjusted for microclimatic differences using a physiological canopy model, with leaf-level parameters estimated for hemp from our previous study. Canopy photosynthetic water-use efficiency (PWUEc), defined as the ratio of gross canopy photosynthesis to canopy transpiration, ranged from 4.0 mmol CO2 (mol H2O)−1 to 7.5 mmol CO2 (mol H2O)−1. Canopy photosynthetic nitrogen-use efficiency (PNUEc), the ratio of the gross canopy photosynthesis to canopy leaf-N content, ranged from 0.3 mol CO2 d−1 (g N)−1 to 0.7 mol CO2 d−1 (g N)−1. The effect of N-input levels on PWUEc and PNUEc was largely determined by the N effect on canopy size or leaf area index (LAI), whereas the effect of water-input levels differed between short- and long-term stresses. The effect of short-term water stress was reflected by stomatal regulation. The long-term stress increased leaf senescence, decreased LAI but retained total canopy N content; however, the increased average leaf-N could not compensate for the lost LAI, leading to a decreased PNUEc. Although hemp is known as a resource-use efficient crop, its final biomass yield and nitrogen use efficiency may be restricted by water limitation during growth. Our results also suggest that crop models should take stress-induced senescence into account in addition to stomatal effects if crops experience a prolonged water stress during growth.

Comparative Assessment of Tundra Vegetation Changes Between North and Southwest Slopes of Changbai Mountains, China, in Response to Global Warming

Vegetation in high altitude areas normally exhibits the strongest response to global warming. We investigated the tundra vegetation on the Changbai Mountains and revealed the similarities and differences between the north and the southwest slopes of the Changbai Mountains in response to global warming. Our results were as follows: 1) The average temperatures in the growing season have increased from 1981 to 2015, the climate tendency rate was 0.38°C/10yr, and there was no obvious change in precipitation observed. 2) The tundra vegetation of the Changbai Mountains has changed significantly over the last 30 years. Specifically, herbaceous plants have invaded into the tundra zone, and the proportion of herbaceous plants was larger than that of shrubs. Shrub tundra was transforming into shrub-grass tundra. 3) The tundra vegetation in the north and southwest slopes of the Changbai Mountains responded differently to global warming. The southwest slope showed a significantly higher degree of invasion from herbaceous plants and exhibited greater vegetation change than the north slope. 4) The species diversity of plant communities on the tundra zone of the north slope changed unimodally with altitude, while that on the tundra zone of the southwest slope decreased monotonously with altitude. Differences in the degree of invasion from herbaceous plants resulted in differences in species diversity patterns between the north and southwest slopes. Differences in local microclimate, plant community successional stage and soil fertility resulted in differential responses of tundra vegetation to global warming.

Physiological Responses of Species to Microclimate Help explain Population Dynamics along Succession in a Tropical Dry Forest of Yucatan, Mexico

We investigated relationships between population dynamics and microclimate, physiology, and the degree of mycorrhizal colonization, for three species (Piscidia piscipula L.(Sarg.)) (Fabaceae), Bunchosia swartziana Griseb. (Malpighiaceae) and Psidium sartorianum (Bergius) Nied. (Myrtaceae)) of a tropical sub deciduous forest in Yucatan, Mexico that were growing in plots of different successional ages. We hypothesized that abundance and persistence were related to increased plasticity in CO2 assimilation. We found that Piscidia piscipula had greater abundance in intermediate plots (18 to 21 years), presented higher levels of plasticity in CO2 assimilation (greater variability among individuals, plots, and seasons), presented the highest CO2 assimilation rates, and presented greater drought resistance (higher water potentials and capacitance). Conversely, Psidium sartorianum had greater abundance in older plots (more than 50 years of secondary succession), lower assimilation rates, and low levels of plasticity in CO2 assimilation. Bunchosia had intermediate values. Locally, the degree of mycorrhizal colonization was consistent with abundance across plots. Regionally (but not locally), plasticity in CO2 assimilation was consistent with abundance. We found differences in microclimates among plots and within plots among species. Physiological adjustments appeared to play an important role in the capacity to regenerate and in the successional persistence of these species in this tropical dry forest.

The Short-Term Effects of Experimental Forestry Treatments on Site Conditions in an Oak–Hornbeam Forest

Forest management alters forest site; however, information is still limited about how different silvicultural treatments modify abiotic conditions. We compared the effects of four treatments from three different forestry systems on forest microclimate, litter, and soil conditions. The clear-cutting, retention tree group, preparation cutting, and gap-cutting treatments were experimentally established in a European oak-dominated forest, following a complete block design with six replicates. In this study, we show the results of the quantitative analyses of 21 variables, one year after the interventions. Strong treatment effects were observed for the microclimate and litter variables, whereas the soil characteristics remained similar. The increase in light was the highest in the clear-cuts with intermediate effects in the gap-cuts. The means and variances of the air and soil temperature as well as the vapor pressure deficit were the highest for the clear-cutting treatment. An increase in soil moisture, litter pH, and litter moisture was significant in the gap-cuts and, to a smaller extent, in the clear-cuts. The soil pH increased in the retention tree groups. Microclimatic differences between the treatments were the largest during the summer, which demonstrates the buffering effect of the canopy. Our study confirms that less intensive and more spatially heterogeneous silvicultural treatments (e.g., gap-cutting) preserve a stable below-canopy microclimate more effectively. These results can support and might be useful for both forest management and conservation planning.

Should we use meshes or solid tube shelters when planting in Mediterranean semiarid environments?

Tree shelters in Mediterranean environments have a two-sided effect. They not only protect seedlings from browsing but also ameliorate microclimatic conditions, improving post-planting survival and growth. However, the ecophysiological basis of these effects are poorly understood. A factorial experiment combining light transmissivity and shelter type (solid tube vs. mesh wall) was carried out to assess the impact of contrasting microclimatic characteristics on seedling performance and physiological stress levels of shelters in two Mediterranean shrubland species (Quercus coccifera and Rhamnus lycioides) planted in a semiarid site. Even though seedlings in solid tube shelters experienced higher temperature and were slightly more photoinhibited, they had higher predawn water potential and, in general, better survival and growth than in mesh wall shelters. However, these effects were species-specific, with Rh. lycioides more favoured by solid wall shelters than Q. coccifera. However, root growth cannot explain these interactions between species and shelter type on seedling survival. Since light transmission had a marginal effect compared with wall type, we proposed that the observed effects and interaction with species are not dependent on light intensity or temperature but on other microclimatic differences like air velocity or light quality and distribution. Further studies should assess the importance of these factors on post-planting growth and physiological stress levels, which can be critical for matching the correct tree shelters type for each species in plantations in semiarid environments.

Alternaria and Fusarium Fungi: Differences in Distribution and Spore Deposition in a Topographically Heterogeneous Wheat Field.

Fusarium spp. and Alternaria spp., two genera of filamentous fungi, are common colonizers of the wheat phyllosphere. Both can be pathogenic and produce mycotoxins that are harmful to consumers. Their in-field infection dynamics have been a focus for the development of new control strategies. We analysed the abundance on plant ears and spore deposition patterns of Fusarium spp. and Alternaria spp. in a topographically heterogeneous field. Abundances were assessed genetically, using qPCR-based techniques, and passive spore traps were installed for quantifying the spore deposition at different plant heights. Data loggers were placed to measure the differences in microclimate across the field. Results indicate different distribution and spore deposition patterns for the two fungi. Fusarium spp. spore and genetic abundances were higher in spots with a more humid and colder under-canopy microclimate. Alternaria spp. showed the opposite trend for genetic abundance, while its spore deposition was not correlated to any of the microclimatic conditions and was more uniform across the field. Our study extends the knowledge on the dispersal and in-field infection dynamics of Fusarium spp. and Alternaria spp., important for a better understanding of the epidemiology of these wheat pathogens. It also illustrates that topographically heterogeneous fields are a suitable environment for studying the ecology of phyllosphere-colonizing fungi.