Variations In Microclimatic Conditions Research Articles

The effect of climate change and urbanization on outdoor microclimate: A case study in Berlin

The urban overheating phenomenon is becoming significant in cities, causing extreme weather conditions that negatively affect citizen comfort and health, and increase building energy consumption. This research, in line with the objective of reducing overheating in city centers, investigates a Berlin district, in Germany, which has undertaken consistent urban evolutions during the last few years. The area falls into the Mitte, Tiergarten, and Moabit quarters and is the site of several governmental and institutional buildings, which were mainly built after 2000. Through a numerical approach, the microclimatic conditions are studied, during a representative summer day, at 3 different times: a past time (2000) before the construction of the main government buildings, a current time (2022), and a future time (2035) taking into account the new building constructions already planned for that area. The urban simulations are performed in ENVI-met, employing, for the past and current climate, weather data registered from the nearest weather station, and for the future one, provisional weather conditions developed according to the RCP 4.5 as 50% warming scenario, and RCP 8.5 as a 95% most warming scenario. Finally, by investigating 7 scenarios, the study shows the weight of climate change and of urbanization on the variation in microclimatic conditions in the considered area of Berlin.

Community dynamics of bumblebee across elevation gradients and habitat mosaics in Chitwan Annapurna Landscape, Nepal

The species composition of bumblebees (Bombus species) across the elevation gradients in Chitwan-Annapurna Landscape (CHAL) was studied from April to November 2019. We performed opportunistic surveys to collect the bumblebee specimens. The walking transects were followed in the accessible places along the Kaligandaki, Marshyandi, and Budhigandaki river basins in different habitats (e.g., agricultural, forest, grassland and home garden). We identified 16 Bombus species from the sampling areas. The highest relative abundance was of B. haemorrhoidalis (20%), followed by B. festivus (20%) and B. eximius (19%). The least abundant species were B. branickii, B. miniatus, B. novus, and B. pressus with 1% relative abundance of each. We examined the effects of elevation on bumblebee richness and found a significant relationship. The Highest species richness was detected in the mid-elevation. Likewise, the highest species richness and diversity were found in the forest habitat in Gorkha site (n = 12, Shannon index H’ = 2.18) followed by the grassland habitat of the Mustang site (n = 11, Shannon index H’ = 2.10). Whereas, comparatively, species diversity was higher in habitats of the Gorkha site comparing Manang and Mustang. The elevation gradients create immense variations in microclimatic conditions and vegetation dynamics, which influence bumblebee abundance, species richness and diversities in different habitats in the study area. The mid-elevation range (2000–3000 m asl) of CHAL exhibited the highest species richness probably due to the higher availability of pollinator-dependent flowering plants in this range. The landcover composition and anthropogenic activities along the elevation gradient is the governing factor for the species composition, distribution and diversity of bumblebees in CHAL. We recommend to decision-makers for formulating their conservation strategies under a socio-ecological framework.

Microclimatic variation in tropical canopies: A glimpse into the processes of community assembly in epiphytic bryophyte communities

Abstract Epiphytic communities offer an original framework to disentangle the contributions of environmental filters, biotic interactions and dispersal limitations to community structure at fine spatial scales. We determine here whether variations in light, microclimatic conditions and host tree size affect the variation in species composition and phylogenetic structure of epiphytic bryophyte communities, and hence, assess the contribution of environmental filtering, phylogenetic constraints and competition to community assembly. A canopy crane giving access to 1.1 ha of tropical rainforest in Yunnan (China) was employed to record hourly light and microclimatic conditions from 54 dataloggers and epiphytic bryophyte communities from 408 plots. Generalized Dissimilarity Modelling was implemented to analyse the relationship between taxonomic and phylogenetic turnover among epiphytic communities, host‐tree characteristics and microclimatic variation. Within‐tree vertical turnover of bryophyte communities was significantly about 30% higher than horizontal turnover among‐trees. Thus, the sharp vertical variations in microclimatic conditions from tree base to canopy are more important than differences in age, reflecting the likelihood of colonization, area, and habitat conditions between young and old trees, in shaping the composition of epiphytic bryophyte communities. Our models, to which microclimatic factors contributed most (83–98%), accounted for 33% and 18% of the variation in vertical turnover in mosses and liverworts, respectively. Phylogenetic turnover shifted from significantly negative or non‐significant within communities to significantly positive among communities, and was slightly, but significantly, correlated with microclimatic variation. These patterns highlight the crucial role of microclimates in determining the composition and phylogenetic structure of epiphytic communities. Synthesis. The mostly non‐significant phylogenetic turnover observed within communities does not support the idea that competition plays an important role in epiphytic bryophytes. Instead, microclimatic variation is the main driver of community composition and phylogenetic structure, evidencing the role of phylogenetic niche conservatism in community assembly.

A Comparative Study on the Selected Environmental Parameters Within the Cage, Pond and the Wild of Winam Gulf of L. Victoria

The main aim of this study was to compare the environmental variables between water inside the caged fish, open ponds and open waters of Winam Gulf. Selected water quality parameters from the 20 ponds, 30 cages and wild were measured in-situ using electronic meters. Water temperature, DO, pH and salinity did not differ significantly in the different study areas (p>0.05) while Total Dissolved Solids (TDS) registered a significant difference between the culture systems (pond and cage) and the wild (p<0.05). This was attributed to the fact that the study areas were all within the same geographical space and there was lack of variation in micro-climatic conditions during the study period, while the differences in TDS could be as a result of over fertilization of ponds, leading to algal bloom. The environmental variables were within the Food and Agricultural Organization (FAO) of the United Nations recommended limits for fish production.

Intra-annual variation in microclimatic conditions in relation to vegetation type and structure in two tropical dry forests undergoing secondary succession

Microclimate acts as a strong filter on species performance in restored and regenerating forests, particularly in seasonally dry tropical forests (SDTF). Yet few studies have measured microclimate patterns across succession in SDTF. Furthermore, although dynamic vegetation models simulate microclimate, evaluation of these simulated variables with field observations has been relatively uncommon. Here, we investigated the seasonal patterns of soil temperature and soil water in naturally regenerated and planted successional vegetation in SDTF in Costa Rica and Puerto Rico, using complementary approaches of intensive field observations and simulation modeling with the Ecosystem Demography model. We found that plots representing later successional stages were wetter on average, but only during the dry season. During the wet season, mean soil water did not differ across vegetation types, but open, early successional vegetation experienced more frequent extreme wet and dry conditions than older forest and plantations. Soil temperature tended to decline with forest structure, and later successional vegetation also experienced less extreme daily temperature fluctuations. Basal area and leaf area index were the best predictors of differences in soil water and temperature across plots. Model simulations were consistent with observations of wet season soil temperature and soil water, but the model failed to reproduce dry season soil moisture dynamics, suggesting that further work is needed to reduce model biases in microclimate variables. Collectively, our results imply that common assumptions about how microclimates influence successional processes in SDTF should be revisited.

Effect of seasonality and microclimate on the variation in bat-fly load (Diptera: Streblidae) in a cave bat assemblage in a dry forest

Abstract Seasonality causes fluctuations in the availability of resources, affecting the presence and abundance of animal species. These fluctuations can have an impact on parasite-host relationships, which in turn can be exacerbated by microclimatic changes to which bat-flies are exposed. We characterized the bat-fly load and evaluated the effect of seasonality on five bat species in a dry forest. We evaluated variations in microclimatic conditions inside the cave Cerro Huatulco between seasons and the response of the bat-fly load. We collected 1165 bat-fly specimens belonging to 16 species from 688 bats. The obtained results indicate that the mean abundance and infestation intensity exhibited changes between seasons in Artibeus jamaicensis, Desmodus rotundus, Glossophaga soricina, and Pteronotus parnellii. In the case of the effect of microclimate conditions, we observed that prevalence is negatively correlated with temperature in G. soricina, while mean abundance and mean infestation intensity were negatively related to temperature in A. jamaicensis and G. soricina. The present study provides significant information about host-parasite relationships in a dry forest and discusses the relevance of abiotic and biotic factors that could affect host-parasite interactions, as well as the importance of each parasite load parameter for the understanding of this interaction.

Microclimatic conditions and water content fluctuations experienced by epiphytic bryophytes in an Amazonian rain forest

Abstract. In the Amazonian rain forest, major parts of trees and shrubs are covered by epiphytic cryptogams of great taxonomic variety, but their relevance in biosphere–atmosphere exchange, climate processes, and nutrient cycling is largely unknown. As cryptogams are poikilohydric organisms, they are physiologically active only under moist conditions. Thus, information on their water content (WC) as well as temperature and light conditions experienced by them are essential to analyze their impact on local, regional, and even global biogeochemical processes. In this study, we present data on the microclimatic conditions, including water content, temperature, and light conditions experienced by epiphytic bryophytes along a vertical gradient, and combine these with above-canopy climate data collected at the Amazon Tall Tower Observatory (ATTO) in the Amazonian rain forest between October 2014 and December 2016. While the monthly average of above-canopy light intensities revealed only minor fluctuations over the course of the year, the light intensities experienced by the bryophytes varied depending on the location within the canopy, probably caused by individual shading by vegetation. In the understory (1.5 m), monthly average light intensities were similar throughout the year, and individual values were extremely low, remaining below 3 µmol m−2 s−1 photosynthetic photon flux density more than 84 % of the time. Temperatures showed only minor variations throughout the year, with higher values and larger height-dependent differences during the dry season. The indirectly assessed water content of bryophytes varied depending on precipitation, air humidity, dew condensation, and bryophyte type. Whereas bryophytes in the canopy were affected by diel fluctuations of the relative humidity and condensation, those close to the forest floor mainly responded to rainfall patterns. In general, bryophytes growing close to the forest floor were limited by light availability, while those growing in the canopy had to withstand larger variations in microclimatic conditions, especially during the dry season. For further research in this field, these data may be combined with CO2 gas exchange measurements to investigate the role of bryophytes in various biosphere–atmosphere exchange processes, and could be a tool to understand the functioning of the epiphytic community in greater detail.

Taking into account climate change adaptation in urban area through the CFD FLUENT simulation model example: an urban sector of the ORAN agglomeration

Large cities cause microclimatic changes, the largest of which is known as the urban Heat Island Effect. The acceleration of urban development has caused variations in microclimatic conditions. Urban geometry and human activities in the urban environment interact with microclimatic parameters (wind speed and direction, air and surface temperature, solar radiation), also transforming the climate of our cities. It is for us to study the impact of climate change on urban environments and to understand the consequences of geometric and morphological factors on microclimatic conditions at the city scale, using tools called Computational Fluid Dynamics (CFD) model, we will try to show how urban geometry, in all its states interacts with microclimatic parameters (solar radiation, wind flows, air and surface temperature). Applied to the agglomeration of ORAN / ALGERIA on an existing urban sector (district HLM ),we will try to show the strong correlation between failures and errors of urban design and the increase and generalization of Heat Island Effect in urban area.

Microclimatic modelling in assessing the impact of urban geometry on urban thermal environment

Diversity in urban geometry can create significant variation in microclimatic conditions. Especially, in tropical warm-humid context, deep urban canyons with variable building heights perform better than uniform canyons, because taller buildings rising above those around them reduce solar gain and enhance wind speed at the pedestrian level. Field measurements in Dhaka comparing the varying traditional urban forms with the more regular formal residential areas have revealed an average air temperature (Ta) difference of 3.3°C and a maximum difference of 6.2°C, and a mean radiant temperature (Tmrt) difference of 10.0°C. The aim of this paper is to understand the responsiveness of the microclimate simulation tool ENVI-met V4 in identifying the variation in urban geometry as reported in the field measurements. The study aims to make specific comparisons between the measured and the simulated data by analysing a particular challenge in complex geometry. It attempts to demonstrate how ENVI-met could benefit from using the correct input as the boundary condition. While the modelling tool aims to produce good results by using synoptic weather information as boundary conditions, this study suggests that it is important to use representative data from the actual site and that hourly input of climatic variables as boundary information can produce the best results. Results show that modelling is able to predict the relative variations in Tmrt conditions between sites, although highly overestimated. However, in terms of Ta, modelling was unable to produce any variations between different urban geometry characteristics. This indicates that, although ENVI-met can produce sufficiently good results in predicting Ta when hourly forcing is used, it is unable to distinguish between the precise details in urban geometry features that can cause significant variations in microclimatic conditions in real situations. Therefore, further assessment of microclimatic variables is needed for using such modelling techniques in order to evaluate the impact of diversity in urban geometry.

Variations in chemical sexual signals of Psammodromus algirus lizards along an elevation gradient may reflect altitudinal variation in microclimatic conditions.

Chemical signals used in intraspecific communication are expected to evolve or to show phenotipic plasticity to maximize efficacy in the climatic conditions of a given environment. Elevational environmental gradients in mountains provide a good opportunity to test this hypothesis by examining variation in characteristics of signals in species found across different elevations with different climatic conditions. We analyzed by gas chromatography-mass spectrometry (GC-MS) the lipophilic fraction of the femoral gland secretions of male lizards Psammodromus algirus (Fam. Lacertidae) from six localities located along a 2200m elevational gradient at Sierra Nevada Mountains (SE Spain). There was elevational clinal variation in climatic variables, number of femoral pores and in the relative proportions of some classes of compounds (i.e., ethyl esters of fatty acids, waxy esters, and aldehydes) but not others. We discuss how this variation would result in different physicochemical properties of the entire femoral secretion, which might help optimize the efficacy of chemical signals under the particular microclimatic conditions at each elevation.

Epiphytic orchids in tropical dry forests of Yucatan, Mexico – Species occurrence, abundance and correlations with host tree characteristics and environmental conditions

Tropical dry forests have been less studied in terms of their resident epiphyte flora compared to wet forests. We studied five species of epiphytic orchids in two dry forest fragments differing in tree composition, stature and rainfall regime. We compared the vertical distribution within the host tree, epiphyte-host associations and seasonal variation in microclimatic conditions in a tropical dry deciduous (Celestún) and a semi-deciduous forest (Kaxil-Kiuic) of the Yucatan Peninsula, Mexico, during the wet, early dry and dry seasons. Light, vapor pressure deficit, air temperature, and dew were measured on two heights (1.5 and 3.5m) of the host with the highest abundance of orchids. Surprisingly, orchid abundance was higher in the Celestún deciduous forest, the site with low precipitation. High epiphyte abundance in the middle canopy stratum of the hosts in both forests was arguably related to a favorable combination of micro-environmental factors. In both forests, about 90% of all orchids grew on a single host tree species. Although bark roughness and the area of the substrate were the most important host characteristics that influenced the abundance of orchids in the Celestún deciduous forest, this did not explain this preference. Climatic variation was greater among seasons than between microenvironments in the host trees. The most abundant species, Encyclia nematocaulon, had a great capacity to occupy different strata in both forests, even in tree tops with very large micro-environmental fluctuations during the year.

Canopy position affects rind biochemical profile of ‘Nules Clementine’ mandarin fruit during postharvest storage

This study was conducted to investigate the effects of preharvest canopy position and bagging treatments on rind physiological and biochemical properties of ‘Nules Clementine’ mandarin (Citrus reticulata Blanco) fruit. Before storage, the respiration rate of unbagged outside fruit was significantly higher (21.6mLCO2kg−1h−1) than of bagged inside fruit (16.3mLCO2kg−1h−1). Unbagged fruit outside the canopy had 1.4-fold higher carbohydrates, and 1.1-fold higher dry matter (DM) content than bagged inside fruit. Bagged fruit inside the canopy had higher (24%) weight loss than outside sun-exposed fruit (14%). This corresponded with a higher rind breakdown (RBD) index for bagged inside fruit, compared to sun-exposed fruit which did not develop the disorder. During postharvest storage, rind fructose levels of bagged fruit inside the canopy increased from 62.4mg/g DM at harvest to 81.3mg/g DM after 8 weeks, while those of unbagged outside fruit increased from 97.9 to 108.4mg/g DM. Concomitant with the increase in fructose, sucrose in rind tissue of bagged inside fruit decreased from 42.6 to 27.7mg/g DM and from 49.3 to 33.4mg/g DM for unbagged outside fruit. Rind glucose of unbagged inside fruit decreased from 90.6 to 76.2mg/g DM. Ascorbic acid concentrations remained almost constant during storage, with levels between 3.3 and 6.7mg/g DM for inside bagged and unbagged outside fruit, respectively. Hesperidin was the major flavanone detected, with concentrations between 35 and 45mg/g DM followed by narirutin (1.1–2.8mg/g DM). At harvest, rind of fruit harvested from outside the canopy had lower hesperidin concentration (38.1mg/g DM) compared to shaded fruit (44.2mg/g DM). Overall, the results suggest that variations in microclimatic conditions inside the tree canopy during the growing season affect the biochemical profile of the fruit rind, which in turn influences fruit response to postharvest stresses associated with senescence and susceptibility to RBD.

Variations in dung beetles assemblages (Coleoptera: Scarabaeidae) within two rain forest habitats in French Guiana

The structure of dung beetle communities inhabiting tropical forests are known to be sensitive to many kinds of environmental changes such as microclimate related to vegetation structure. I examined Scarabaeinae assemblages in two sites of undisturbed high forest and two sites of low forest forming a transitional zone with the open habitat of an inselberg in French Guiana. Sampling was made with pitfall and flight interception traps during 2003 and 2004. The driest and warmest conditions characterized the low forest sites. Across two years we obtained 2 927 individuals from 61 species with pitfall traps and 1 431 individuals from 85 species with flight interception traps. Greater species richness and abundance characterized all sites sampled with pitfall traps during 2003 more than 2004. In 2003 no differences were detected among sites by rarefaction analyses. In 2004 the species richest high forest site was significantly different from one of the low forest sites. For both years Clench model asymptotes for species richness were greater in high forest than in low forest sites. For both years, mean per-trap species richness, abundance and biomass among high forest sites were similar and higher than in low forest sites, especially where the lowest humidity and the highest temperature were recorded. Within the two low forest sites, species richness and abundance recorded during the second year, decreased with distance to edge. Different dominant roller species characterized the pitfall samples in one site of low forest and in other sites. Small variations in microclimatic conditions correlated to canopy height and openness likely affected dung beetle assemblages but soil depth and the presence of large mammals providing dung resource may also play a significant role.

Effects of environmental heterogeneity on species diversity and composition of terrestrial bryophyte assemblages in tropical montane forests of southern Ecuador

Background: Most studies on tropical bryophytes deal with epiphytic species. This is the first ecological study of tropical forests that focuses specifically on terrestrial bryophytes. Aim: To investigate the differences between slope and ridge environments in upper montane forests of southern Ecuador in terms of species diversity (richness, abundance), species composition and life forms of terrestrial bryophytes. Methods: We used Non-metric Multidimensional Scaling (NMDS) to group bryophyte relevés by study location, habitat type and exposure class. Species indicator values were calculated and compared for different habitats. Results: In total, 140 species were recorded, the majority being liverworts. NMDS analyses and Mantel correlations clearly separated between slope and ridge relevés, and between sunny and shaded microhabitats on ridges. Bryophyte life forms also showed different distribution patterns in slope and in ridge habitats. Mosses were more prominent in sunny than in shaded microhabitats. Conclusions: Environmental differentiation between ridges and slopes, and small-scale variation in microclimatic conditions caused by differences in exposure, were stronger predictors of species richness and composition than geographical distance between study sites.

Nest-site Selection in a Postfire Landscape: Do Parents Make Tradeoffs between Microclimate and Predation Risk?

ABSTRACT. Maternal preference for nest sites is predicted to be an adaptive consequence of selective pressures acting on parents and young at the nest site. Nest predation risk has been linked to nest-site placement in birds, but microclimatic extremes can impose fitness costs on both adults and young, and these two factors may conflict. I used the temporal and spatial variation in microclimatic conditions and nest predation risk generated by variation in wildfire severity to examine the relationship between nest-site preference, nest microclimate, and fitness costs to parents and young in the Dark-eyed Junco (Junco hyemalis), a facultative cavity-nester. Adults preferred to select exposed nest sites oriented toward the north—sites that consistently had the most moderate thermal regimes. Nestlings reared in burrow-type nests gained mass more slowly and experienced retarded skeletal growth compared with exposed nests, but slower growth was not explained by suboptimal nest temperatures, nestling provisionin...

Seasonal variations of microclimatic conditions in domestic and peridomestic habitats of Triatoma infestans in rural northwest Argentina

Our objectives were to describe and compare the seasonal variations in microclimatic conditions in domestic and peridomestic ecotopes infested by Triatoma infestans, the main vector of Chagas disease, in rural northwestern Argentina. Using data loggers for 4–7 consecutive days in October 2000, February, May and August 2001, microsite (interior of thatched roofs) and ambient temperatures or relative humidity (RH) were recorded simultaneously and compared with an external reference. The damping effects on microsite temperature and ambient RH increased successively from the goat corral to the chicken coop or pig corral, to the storeroom or human habitation. In the interior of the thatched roofs of the habitation and storeroom, average external minima were increased by +5.0 to +5.6 °C in all seasons, and average external maxima were decreased by −4.3 to −5.6 °C in October–May and −10.6 °C in August. On average, the human habitation damped extreme temperatures by 8 °C over a wider range than previously reported. The interior of the thatched roofs of the pig corral and chicken coop exerted intermediate damping effects that varied over seasons, whereas the goat corral's thatch showed little or no damping effects at all. The adobe-and-thatch habitation and storeroom presented nearly optimal and more suitable conditions for T. infestans populations than other open structures housing animals. Global climate changes are expected to affect peridomestic populations of T. infestans much more than domestic bug populations, provided other local conditions are held constant. Heterogeneous habitat conditions are expected to affect T. infestans population parameters, dispersal, control and infection with Trypanosoma cruzi.

The Soil Fauna of an Alpine Glacier Foreland: Colonization and Succession

We investigated the development of soil macrofauna and mesofauna in the successional chronosequence of an Alpine glacier foreland located above the treeline. Sampling transects 10 m long were established at eight successional stages from 4 to 150 yr of age since deglaciation, and in addition two reference sites in front of the terminal moraine. Within the first 50 yr, macrofauna biomass and mesofauna abundance increased rapidly, attaining levels typical for all older stages (macrofauna 0.5–7 g m–2, microarthropods 50–120 103 ind. m–2). Among the macrofauna nematoceran Diptera were dominant at most sites, only the early colonizing stages being dominated by carabid and lepidopteran larvae and enchytraeids. Acari were more abundant than Collembola. Temporal sequences of occurrence were documented for macrofauna families and for collembolan species. Successional age was the major determinant of community composition, additional influences being local variations in microclimatic conditions and soil properties. Biomass increased over the short alpine summer, but community composition remained largely constant. The high aggregation of soil fauna affected the precision of abundance estimates. An outline of the trophic structure of evolving soil communities is presented.

The Soil Fauna of an Alpine Glacier Foreland: Colonization and Succession

We investigated the development of soil macrofauna and mesofauna in the successional chronosequence of an Alpine glacier foreland located above the treeline. Sampling transects 10 m long were established at eight successional stages from 4 to 150 yr of age since deglaciation, and in addition two reference sites in front of the terminal moraine. Within the first 50 yr, macrofauna biomass and mesofauna abundance increased rapidly, attaining levels typical for all older stages (macrofauna 0.5–7 g m–2, microarthropods 50–120 103 ind. m–2). Among the macrofauna nematoceran Diptera were dominant at most sites, only the early colonizing stages being dominated by carabid and lepidopteran larvae and enchytraeids. Acari were more abundant than Collembola. Temporal sequences of occurrence were documented for macrofauna families and for collembolan species. Successional age was the major determinant of community composition, additional influences being local variations in microclimatic conditions and soil properties. Biomass increased over the short alpine summer, but community composition remained largely constant. The high aggregation of soil fauna affected the precision of abundance estimates. An outline of the trophic structure of evolving soil communities is presented.

Productivity, microclimate and water use in Grevillea robusta-based agroforestry systems on hillslopes in semi-arid Kenya

This paper describes a multi-disciplinary project to examine the changing interactions between trees and crops as the trees in semi-arid agroforestry systems establish and mature; the project is one of the most detailed and highly instrumented long-term studies of tree and crop growth, system performance, resource capture, hydrology and microclimate ever carried out within an agroforestry context. Its primary objective was to compile a comprehensive experimental database to improve the mechanistic understanding of tree/crop interactions and support the development and validation of process-based simulation models describing resource capture and tree and crop growth in semi-arid agroforestry systems. Grevillea robusta A. Cunn. (grevillea) trees were grown as mono-cultures or in mixtures with cowpea ( Vigna unguiculata L.) or maize ( Zea mays L.) over a 68-month period. Allometric approaches were used to determine seasonal and annual growth increments for leaf area and leaf, branch and trunk biomass in grevillea. Crop performance was examined during each growing season, while the spatial distribution of tree and crop roots was established during the latter stages of the experiment using coring and mini-rhizotron approaches. Detailed hydrological studies examined effects on the soil water balance and its components (precipitation, interception, runoff and soil moisture status); equivalent measurements of spatial and temporal variation in microclimatic conditions allowed the mechanistic basis for beneficial and detrimental effects on understorey crops and the influence of proximity to trees on crop performance to be examined. Transpiration by grevillea and water movement through lateral and tap roots were measured using sap flow methodology, and light interception by the tree and crop canopies was routinely determined. This multi-disciplinary study has provided a detailed understanding of the changing patterns of resource capture by trees and crops as agroforestry systems mature. This paper provides an overview of the underlying rationale, experimental design and core measurements, outlines key results and conclusions, and draws the attention of readers to further papers providing more detailed consideration of specific aspects of the study.

Complex edge effects on soil moisture and microclimate in central Amazonian forest

ABSTRACTWe investigated the influence of a four-year-old forest edge near Manaus, Brazil, on soil moisture and vertical profiles of air vapour pressure deficit (VPD) within the forest. Soil moisture was measured (with a neutron probe) 0, 5, 10, 20, 40, 60, 80, 100, 150 and 200 m into the forest from the edge, in undisturbed control areas, and in the pasture. Control soil moisture was better explained by rainfall in the previous 2 or 10 days than by longer-term totals. Soil water potentials ≤ – 1.5 MPa occurred at some forest locations during the driest period. The variation in soil moisture with distance from the forest edge was complex, with higher values just inside the edge and depleted zones at the edge and 40–80 m inside it. At a given height, VPD (standardized relative to measurements in the open) was not related to distance from the edge, but VPD increased more with height near the edge than in control areas. The complexity of the edge's influence and the contrast with earlier data from the same edge can be explained by the changing vegetation structure near the edge. Regrowth ‘seals’ the edge with more leaves that transpire and deplete soil moisture, while protecting the understorey just inside the edge from desiccating conditions. A mosaic of gaps of differing ages develops behind the edge, increasing the variation in microclimatic conditions near the ground and consequently in evapotranspiration and soil moisture.