Canopy Radiation Interception Research Articles

Photosynthetic temperature responses in leaves and canopies: why temperature optima may disagree at different scales.

Understanding how canopy-scale photosynthesis responds to temperature is of paramount importance for realistic prediction of the likely impact of climate change on forest growth. The effects of temperature on leaf-scale photosynthesis have been extensively documented but data demonstrating the temperature response of canopy-scale photosynthesis are relatively rare, and the mechanisms that determine the response are not well quantified. Here, we compared leaf- and canopy-scale photosynthesis responses to temperature measured in a whole-tree chamber experiment and tested mechanisms that could explain the difference between leaf and crown scale temperature optima for photosynthesis. We hypothesised that 1) there is a large contribution of non-light saturated leaves to total crown photosynthesis; 2) photosynthetic component processes vary vertically through the canopy following the gradient in incident light; and 3) seasonal temperature acclimation of photosynthetic biochemistry has a significant role in determining the overall temperature response of canopy photosynthesis. We tested these hypotheses using three models of canopy radiation interception and photosynthesis parameterized with leaf-level physiological data and estimates of canopy leaf area. Our results identified the influence of non-light saturated leaves as a key determinant of the lower temperature optimum of canopy photosynthesis, which reduced the temperature optimum of canopy photosynthesis by 6-8°C compared to the leaf scale. Further, we demonstrate the importance of accounting for within-canopy variation and seasonal temperature acclimation of photosynthetic biochemistry in determining the magnitude of canopy photosynthesis. Overall, our study identifies key processes that need to be incorporated in terrestrial biosphere models to accurately predict temperature responses of whole-tree photosynthesis.

Tailoring defoliation and nitrogen management for large canopy radiation use and biomass production of perennial systems destined for biorefinery

Perennial leafy grasses and legumes are promising for extraction of proteins with a green biorefinery amid increasing demand for local production. However, which defoliation strategy increases radiation-use efficiency and biomass production still needs to be determined. A multi-year field experiment started in 2019 in Denmark with fertilized grasses (perennial ryegrass, tall fescue), unfertilized legumes (alfalfa, red clover) and their fertilized mixture (grass-legume), each defoliated at 2-, 4- or 8- weeks interval, at either 7-9 or 12-14 cm defoliation height. The main aim was to quantify effects of species, defoliation height and frequency, and nitrogen application rate on canopy radiation interception, aboveground biomass and crude protein production, as well as aboveground radiation use efficiency (RUEA).The results showed that accumulated intercepted photosynthetically active radiation (AIpar) increased with increasing defoliation height and decreasing frequency for most systems, with the largest AIpar obtained seasonally by red clover (730-815 MJ m−2) and grass-legume mixture (790-826 MJ m−2) defoliated at medium to low frequency. Tall fescue defoliated at medium to low frequency yielded the highest aboveground biomass (10-14 Mg ha−1) and red clover defoliated at medium to high frequency yielded the most crude protein (2.5-2.9 Mg ha−1) compared to all other systems annually. RUEA decreased with increasing defoliation height and maximum values were achieved at medium frequency, with tall fescue having significantly higher RUEA (1.6-2.1 g MJ−1) than the other systems. Seasonally, RUEA was variable at high defoliation frequency, being consistently higher at the start and the end of the season for ryegrass and the mixture systems.This study pinpoints tall fescue and red clover as perennial crops with high agronomic productivity among tested species for green biorefinery and also concluded that red clover in temperate humid climate maximize productivity and sustainability for biorefining with defoliation at low height and medium frequency.

Relationships between canopy radiation interception and LiDAR-derived geometry features in pome and stone fruit

Relationships between canopy radiation interception and LiDAR-derived geometry features in pome and stone fruit

Effect of potassium rate on yield, potassium uptake and canopy radiation interception of direct-seeded winter canola

Direct seeded canola (Brassica napus L.) has become increasingly popular in China’s key canola-producing regions. The studies on the K response of direct-seeded canola performance are limited. This research aimed to investigate the K utilization efficiency and canopy radiation interception rate of direct seeded winter canola at various K application rates. Two seasons field trials were done with five K levels (0, 75, 150, 225, and 300 kg K2O ha-1) utilizing two key local cultivars (Huayouza no. 9 and Zhongshuang no. 11) in Southwest China. Canola yield rose by 17.9%-82.6% in 2017-2018 and 21.1%-73.6% in 2018-2019 when K was applied, compared to K-unfertilized. Canola yield go up rapidly at first and then gradually when K ingestion grew, demonstrating the phenomena of K luxury consumption. As K levels rose, internal utilization efficiency, agronomic efficiency, and physiological efficiency all decreased. In canola pod development and maturation period, 150 kg K2O ha-1 intercepted the most solar radiation (73.8%), while K-unfertilized treatment intercepted the least (61.6%) on average. The K supply rates had a significant effect on canopy radiation interception and K absorption in winter canola. When K application exceeded a specific rate, luxury consumption occurred. Canola’s luxury K consumption was mostly stored in the pericarp and plant stem.

Yield and canopy radiation interception of two blush pear selections in Australia

Yield and canopy radiation interception of two blush pear selections in Australia

Deficit irrigation maintains maize yield through improved soil water extraction and stable canopy radiation interception

AbstractDeficit irrigation (DI) is an effective way to save irrigation water while maintaining sustainable yield in irrigated crops. However, limited information is available related to canopy structure and solar radiation use under DI condition. In this study, our objective was to assess maize hybrids for leaf development, photosynthetically active radiation (PAR) interception and water use under DI condition. Field experiments were conducted in 2016 and 2017 in four maize hybrids at well‐watered (I100, referring to 100% evapotranspiration [ET] requirement) and DI (I75, referring to 75% ET requirement) water regimes. Compared to I100, I75 did not reduce maize biomass and grain yield. Although DI reduced the leaf appearance rates (1.5% in 2016 and 7.6% in 2017) and resulted in greater variations in leaf area index (LAI) among hybrids, the amount of PAR interception was not affected during the growing season. DI significantly reduced the seasonal ET in both years (19.8% in 2016 and 26.6% in 2017). All the hybrids extracted more soil water (29 mm in 2016 and 27 mm in 2017) at I75 than at I100. Maize plants at I75 had greater water use efficiency (WUE) (1.68 kg m−3) than those at I100 (1.41 kg m−3). However, DI did not affect radiation use efficiency (RUE). In conclusion, DI at I75 maintained grain yield through improved soil water extraction and WUE but stable canopy radiation interception and RUE.

Effects of Rootstock, Tree Density and Training System on Early Growth, Yield and Fruit Quality of Blush Pear

Vegetative growth, orchard productivity, fruit quality and marketable yield were evaluated for rootstock (D6, BP1 and Quince A), tree density (741–4444 trees/ha), and training system (Open Tatura trellis, two-dimensional vertical and three-dimensional traditional) effects on young trees of the blush pear cultivar ‘ANP-0131’. ‘ANP-0131’ is a vigorous scion and vegetative growth, precocity, and yield were influenced by the selected rootstocks. Tree density and training system treatments exerted a substantial effect on canopy radiation interception while increasing tree density improved yield. Increasing tree density from 2222 (high density) to 4444 (ultra-high density) trees/ha did not improve cumulative yield. Crop load affected fruit size, such that “marketable” yield (yield of fruit weighing between 150 and 260 g) was greatest for trees on D6 rootstock and trained to Open Tatura trellis at high and ultra-high densities.

Effects of leaf age and canopy structure on gross ecosystem production in a subtropical evergreen Chinese fir forest

Despite the advances in technologies to derive the maximum rate of Rubisco carboxylation (Vcmax) seasonality at large-scale, factors controlling the temporal dynamics of Vcmax is largely unknown without extensive field measurements at stand scale. In addition, state-of-the-art process-based terrestrial ecosystem models had not accounted the complex canopy structure for estimating radiation interception by vegetation. Both of which could lead to uncertainties in gross ecosystem production (GEP) estimations. Here, we examined the respective and combined effects of leaf age and canopy structure on GEP by integrating the Farquhar photosynthesis model with a two-leaf (sunlit and shaded) canopy radiation interception model based on the Geometric Optical and Radiative Transfer (GORT) theory. We observed that the Vcmax of new leaves was approximately 34.4% higher than that of mature leaves. Considering the seasonal dynamics of Vcmax caused by new leaf expansion, the average bias between the modeled GEP and that derived from the eddy covariance (EC) in the growing season at 8-day temporal scale was reduced from -8% to -1%, with slightly higher correlation (from 0.9 to 0.92) and reduction in root mean squared error (from 6.0 to 3.9 g C m−2 8d−1). Most importantly, the total effect of new leaf expansion and canopy gaps during the growing season was +322 g C m−2 yr−1 and -114 g C m−2 yr−1, which was approximately 22.5% and 8.1% of the total GEP, respectively. Thus, it is important to consider both leaf age and canopy structure when developing a robust terrestrial ecosystem model. We highlighted that Vcmax seasonality and realistic canopy radiation interception simulation are critical for accurate estimation of canopy GEP for evergreen forests.

Interactions of Spring Cereal Genotypic Attributes and Recovery of Grain Yield After Defoliation.

Dual-purpose crops are grazed during their vegetative phase and allowed to regrow to produce grain. Grazing slow-developing winter cereals (wheat, barley, and triticale) is common, but there is also potential to graze faster-developing spring cereals used in regions with shorter-growing seasons. Defoliation in faster-developing genotypes has risks of larger yield penalties, however, little is known about genotypic characteristics that may improve recovery after grazing. Four experiments examined 7 spring wheat and 2 barley cultivars with differing physiological attributes (phenological development rate, putative capacity to accumulate soluble carbohydrates, and tillering capacity) that may influence the capacity of spring wheat to recover after defoliation. Defoliated and undefoliated crops were compared to assess physiological differences between cultivars including recovery of biomass, leaf area and radiation interception at anthesis, and subsequent crop grain yield and yield components. All genotypes had similar responses to defoliation treatments indicating that the physiological attributes studied played little part in mitigating yield penalties after defoliation. Despite some differences in yield components amongst cultivars, defoliation did not adversely affect cultivars with different yield component combinations under non-water limited conditions. Later and intense defoliation (around GS30/31) resulted in large yield penalties (40%) which reduced both grain number and kernel mass. However, earlier defoliation (before GS28) induced small or insignificant yield penalties. Defoliation often reduced canopy radiation interception and crop biomass at anthesis but this rarely translated into large yield penalties. These studies further demonstrate that shorter season spring cereals can provide valuable forage (up to 1.2 t DM/ha) for grazing during early vegetative growth without inducing large yield penalties. This study suggests that beyond appropriate phenology, there were no other specific characteristics of cultivars that improved the recovery after grazing. Hence farmers don’t need specific dual-purpose cultivars and can still focus on those that optimize grain yield potential for a particular environment and sowing date. The timing and intensity of defoliation appear to be larger drivers of yield recovery in spring cereals and better understanding of these relationships are needed to provide grazing management guidelines that mitigate risk of yield penalties in dual-purpose cereal crops.

Modeling leaf area development in soybean (Glycine max L.) based on the branch growth and leaf elongation

ABSTRACT Several models have been proposed to simulate the leaf area index (LAI) in soybean (Glycine max L.); however, these models do not directly account for the effect of branch growth. Because the increases in branches and branch node vary with plant density, the evaluation of branch growth is necessary for the application of the LAI model at various plant densities. In this study, we developed an LAI model for soybean, considering the branch growth and leaf elongation at each node. To simplify this model, we estimated the rate of branch and branch node increase based on the rate of main stem node increase. Branch growth was assumed to be restricted when the fraction of canopy radiation interception was increased. Moreover, we calculated the leaf area growth at each node based on leaf elongation at each leaflet. This LAI model was validated using the data of different years and plant densities for model calibration, and it estimated the LAI with a root mean square error of 0.76, which accounted for 92% of the variation in the data. Although further evaluation is needed, the LAI model proposed in this study reveals a high potential for accurate estimation of LAI at various plant densities.

Irrigation management with saline groundwater of a date palm cultivar in the hyper-arid United Arab Emirates

The United Arab Emirates has a hyper-arid climate. Irrigation is essential for dates (Phoenix dactylifera L.), an important crop economically and culturally. Groundwater is relied on, yet it is a non-renewable resource at the rate it is being used. Furthermore, as the water-table drops, it is becoming more saline. Law no. 5 has been passed in Abu Dhabi to regulate the use of groundwater and set allocation limits for agriculture. For assessing the allocation of irrigation water to date farms under Law 5, we carried out measurements of tree water-use by the compensation heat-pulse method, complemented by measurements of the changing soil-water dynamics using time domain reflectometry and bulk soil electrical conductivity. Over four years we measured the hourly pattern of Lulu date-palm water use, ETc, at two levels of irrigation-water salinity: Treatment S1 at 5 dS m−1, and S3 at 15 dS m−1. The mid-summer ETc for the S1 Lulu trees is up to 190 L d−1, on average, whereas for the S3 trees ETc is lower at 130 L d−1 (68% of S1) because of the salt. Measurements of canopy radiation interception using a ‘light stick’ showed the S1 trees intercepted 26% of the incident radiation, whereas the S3 trees only intercepted 20% (ratio S3/S1 = 76%). The date yield of the S1 trees was 68 kg tree−1, but was 46 kg tree−1 for the S3 trees (ratio 68%). Current practice is to irrigate trees with 275 L d−1, irrespective of salinity. Our recommendation for Law 5 is to tailor irrigation to the seasonal demand in the reference evapotranspiration of ETo, and allow for a 25% factor-of-safety and a 25% salt leaching fraction. For S1 date palms this would mean an annual average of 210 L d−1, and for S3 just 137 L d−1. This represents savings of 25–50% from current practice.

Influence of low light intensity on growth and biomass allocation, leaf photosynthesis and canopy radiation interception and use in two forage species of Centrosema (DC.) Benth.

AbstractSustainable silvopastoral systems rely on the capacity of forage species to withstand shade, competition for soil resources and grazing. On a field‐plot experiment, we studied the effects of artificial shade on the performance of two tropical forage legumes: Centrosema molle (CIAT 15160) and C. macrocarpum (CIAT 5713). Acclimation to shade in these two species was investigated at individual leaf and whole canopies, to explain differences in the efficiency of radiation interception and use, and thus forage yield. Under 30% sunlight, midday leaf net photosynthesis (A) was reduced by 32%–44%, although instantaneous light use efficiency increased up to 44%–140%. Almost 50% increase in leaf specific area was accompanied by 61% in total chlorophyll content. From analysis of the light‐response curves, net photosynthesis at light saturation was only reduced (by 36%) in C. macrocarpum. Efficiency of chloroplast photosystem II (PSII) was unaffected by shade. Canopy structure for light interception was not modified by shade, although conversion into biomass and final yield were significantly reduced (40%–43%) in C. macrocarpum. Results are discussed in terms of factors affecting potential acclimation to shade and the agronomic implications of using both forage legumes in mixed pastures under tree canopies.

Disturbances in European beech water relation during an extreme drought

In the context of a probable increase in intensity and frequency of extreme summer drought events, a better understanding of the key processes involved in water relations is needed to improve the theoretical foundations of predictive process-based models. This paper aims to analyse how temperate deciduous trees cope with water shortage. The exceptional summer drought of 2003 in Europe provided an opportunity to monitor stomatal conductance and twig water potential in European beech (Fagus sylvatica L.) at predawn and midday and to analyse variations with respect to leaf height within the canopy. By comparing our field measurements of twig water potential to values found in the literature, we confirmed the strong impact of soil water shortage on crown water relations. This paper shows that (1) the vertical gradient of stomatal conductance within the crown disappeared under extreme soil water depletion; (2) at maximum drought intensity, predawn twig water potential (ψ pd) reached −2.3 MPa at a height of 14 m in the crown and −2.0 MPa at a height of 10 m. The significant differences in ψ pd between the two measurement heights in the canopy may be due to night transpiration; (3) there was a close relationship between predawn twig water potential and relative extractable soil water; (4) as drought conditions intensified, there was a close relationship between canopy radiation interception and predawn water potential, as estimated daily from relative extractable soil water.

RADIATION USE EFFICIENCY AND ABOVE-GROUND BIOMASS PRODUCTION OF SELECTED FOREST TREE SPECIES

Radiation use efficiency (RUE). defined as biomass produced per unit ofradiation intercepted. is considered a genotype-specific constant. Ifthe amountof radiation intercepted is known. RUE can be used to predict the potentialbiomass production o]'a given tree species. A comparative growth analysis wasdone on some selected species, with the objective of determining their lightinterception characteristics, biomass production, and RUE. Similar-agedseedlings of six forest tree species: Acacia mangium, Eucalyptus grandis,Leucaena leucoccphala, Swietenia macrophylla, Azadirachta indica, andTectono grandis, were planted at the university farm, Peradeniya, from July1995 to June 1996. Regular sampling was done to determine above-groundbiomass and leal area. Canopy radiation interception was estimated fromsimultaneous measurements of incident and transmitted radiation. by tubesolarimeters. In a/I six species, above-ground biomass production was found tvbe linearly related to cumulative intercepted radiation. The slopes of therelationships, which indicate R liE. showed significant inter-species variation.The greatest RUE was observed in E. gram/is (3.05 gA1fI) and the least inAzadarachta indica (0.296 gUfI). The differences in RUE were primarilyresponsible for the differences between species in above-ground biomassproduction. Radiation interception by the canopies ofthe different species wascharacterized by the light extinction coefficient, which showed significant interspeciesvariation. These parameters offer a promising approach Jill' modellingand prediction ofbiomass production by forest tree species.

Impact of elevated atmospheric CO2 on radiation utilization and related plant biophysical properties in pigeon pea (Cajanus cajan L.)

An open top chamber (OTC) study was conducted with two replications to investigate the impact of elevated CO2 (580ppm) on canopy radiation interception and its use in relation to yield components of two pigeon pea (Cajanus cajan L.) cultivars Pusa-992 and PS-2009. Two OTCs with ambient CO2 of 380ppm were used as control. The LAI and above ground biomass were significantly higher during most of the growth stages for plants exposed to higher CO2 concentration. The canopy radiation extinction coefficient (k) values for both the cultivars were lower for plants exposed to elevated CO2 than for control plants, indicating a more erect structure of these plants. However, the radiation use efficiency (RUE) was 52.3% higher for plants grown under elevated CO2 than for plants grown under ambient CO2 for both the cultivars. The canopy temperature of plants grown under elevated CO2 was found to be lower throughout the growing period. Correspondingly, these plants were supported by higher soil moisture depletion from deeper soil layers. In cultivar Pusa-992, seed yield increased by 12.0% under elevated CO2 because of increase in pod numbers and weight. But in this cultivar, the significant increase (40.6%) in biomass under elevated CO2 did not translate into a corresponding increase in seed yield due to lower harvest index and less numbers of seed per pod. Under elevated CO2, the other cultivar PS-2009 became indeterminate and did not mature, resulting in undeveloped pods. Hence in PS-2009, elevated CO2 resulted in poor seed yield, pod numbers and pod weight even though the biomass produced was higher. Elevated CO2 in the future may result in higher biomass production and higher RUE in pigeon pea due to carbon fertilization, but may not cause a corresponding gain in grain yield because it may lower harvest index.

Nitrogen Uptake by Rice (Oryza sativa L.) Exposed to Low Water Temperatures at Different Growth Stages

AbstractThe responses of nitrogen (N) uptake by rice (Oryza sativa L.) to low water temperatures at different growth stages were examined during a 3‐year field trial in northern Japan. Cool irrigation water was applied at two to three temperature levels (16–25 °C) for 20–34 days during the vegetative stage and then during reproductive growth. We measured the N uptake rate, N content and canopy radiation interception during both growth stages. Exposure to low water temperature during either the vegetative or the reproductive growth stage slowed N uptake, and the magnitude of the decrease differed between the growth stages; the decrease was greater during vegetative growth than during reproductive growth. Consequently, total N uptake at maturity was most strongly reduced by low water temperature during vegetative growth and was not affected by low water temperature during reproductive growth, even though N distribution to the panicle was greatly reduced. The variations in N uptake during the growing season among growth stages and years were explained better by the amount of canopy radiation capture than by the number of degree‐days based on water temperature. This strong dependency on canopy radiation capture improves our understanding of the factors responsible for variations in N uptake under different levels of water temperature, and this knowledge will provide an opportunity to simplify the modelling of N uptake.

Effects of cover diffusive properties on the components of greenhouse solar radiation

This study deals with the characterization and analysis of the components of solar radiation under a highly diffusing cover material. Measurements of outside and inside global (Go and Gi, respectively) and diffuse (Do and Di, respectively) radiation were carried out over the course of several years (2000–2004) under a plastic greenhouse. It was shown that the cover diffusive properties can be characterized in situ through sound physically-based parameters. We suggested the use of two specific greenhouse transmittances (direct-to-direct, τb-b, and direct-to-diffuse, τb-d, transmittances), or alternatively, the use of greenhouse diffuse ratio (ρ = Di/Do) and its derivate, the enrichment coefficient (ɛ). The transmittances were primarily dependent on the diffusive properties of the cover, with a seasonal modulation due to the influence of the beam incidence angle. We found that τb-d was significantly less sensitive to the incidence angle than τb-b. Our results also evidenced that extrinsic factors, such as condensation events and dust deposition, might have significant non-permanent effects on both τb-b and τb-d during some periods of the year. Finally, we proposed a straightforward means to obtain a quantitative estimate of the amount of inside diffuse radiation through the relationship (power function) between ρ and the outside diffuse-to-global fraction, fo. Importantly, the value of the exponent of the power function could be used to characterize and quantify the diffusive power of greenhouse cover materials. Overall, the results stressed the significant impact of the cover diffusive properties on inside solar radiation partitioning, as well as the need to account for these changes in models aimed to estimate the direct and diffuse components, canopy radiation interception and yield in greenhouse agrosystems.

Uniformity of Soil-Plant-Atmosphere-Research Chambers

Uniformity of plant responses and gas exchange calculations within and among Soil-Plant-Atmosphere Research (SPAR) chambers was evaluated using 12 SPAR chambers located at Beltsville, Maryland. Periodic non-destructive and destructive measurements were conducted at the same locations within each chamber using wheat (Triticum aestivum L. cv. USU-Apogee) as the crop. Identical experimental protocols were applied to each chamber. Analysis of variance indicated significant location effects within chambers at three different harvest dates. The patterning of variation within the SPAR chambers was primarily south to north and appeared to be a response to wind speed, radiation gradients, and soil media settling. Analysis of canopy radiation interception and photosynthetic responses indicated differences in early leaf area establishment among chambers. This result can be attributed primarily to variations in emergence rate, irrigation delivery, and media settling. However, no significant differences among final chamber means for any plant growth response were found, and most values were within 95% confidence limits of the pooled chamber mean. Overall, this study indicated that although differences in among-chamber and within-chamber variability were present, when appropriate experimental protocols are followed and within-chamber positional effects are taken into account during sampling, effects of inherent differences in chamber performance on plant responses can be reduced.

Growth and evapotranspiration of groundnut (Arachis hypogaea) in a transitional humid zone of Nigeria

This experiment was conducted in the transitional humid zone of Nigeria to examine crop evapotranspiration and growth characteristics of groundnut (Arachis hypogaea L.) for that ecological zone. The crop was grown in and outside a drainage lysimeter for two years. Mean total water used (Evapotranspiration) by the crop during the 105 days from sowing to harvest was 302.5 mm. More water was used between the vegetative and reproductive growth stages of the crop, that is, between 20 and 60 days after planting DAP. The highest mean leaf area (LAI) obtained was 7 at 75 DAP. Lysimeter mean grain yield was 940 kg/ha while mean yields in rainfed plots was 1511 kg/ha. Yield from the rainfed plot was significantly different (p = 0.01) from yields from the lysimeter plot. There was high positive correlation (p = 0.01) between growth parameters and water use. Dry matter accumulation was highest between 75 and 90 DAP when canopy radiation interception was between 70 and 80 percent. Key words: Drainage lysimeter, crop evapotranspiration, leaf area index, dry-matter accumulation, yield, canopy radiation interception.

Regional climate modulates the canopy mosaic of favourable and risky microclimates for insects

1. One major gap in our ability to predict the impacts of climate change is a quantitative analysis of temperatures experienced by organisms under natural conditions. We developed a framework to describe and quantify the impacts of local climate on the mosaic of microclimates and physiological states of insects within tree canopies. This approach was applied to a leaf mining moth feeding on apple leaf tissues. 2. Canopy geometry was explicitly considered by mapping the 3D position and orientation of more than 26 000 leaves in an apple tree. Four published models for canopy radiation interception, energy budget of leaves and mines, body temperature and developmental rate of the leaf miner were integrated. Model predictions were compared with actual microclimate temperatures. The biophysical model accurately predicted temperature within mines at different positions within the tree crown. 3. Field temperature measurements indicated that leaf and mine temperature patterns differ according to the regional climatic conditions (cloudy or sunny) and depending on their location within the canopy. Mines in the sun can be warmer than those in the shade by several degrees and the heterogeneity of mine temperature was incremented by 120%, compared with that of leaf temperature. 4. The integrated model was used to explore the impact of both warm and exceptionally hot climatic conditions recorded during a heat wave on the microclimate heterogeneity at canopy scale. During warm conditions, larvae in sunlight-exposed mines experienced nearly optimal growth conditions compared with those within shaded mines. The developmental rate was increased by almost 50% in the sunny microhabitat compared with the shaded location. Larvae, however, experienced optimal temperatures for their development inside shaded mines during extreme climatic conditions, whereas larvae in exposed mines were overheating, leading to major risks of mortality. 5. Tree canopies act as both magnifiers and reducers of the climatic regime experienced in open air outside canopies. Favourable and risky spots within the canopy do change as a function of the climatic conditions at the regional scale. The shifting nature of the mosaic of suitable and risky habitats may explain the observed uniform distribution of leaf miners within tree canopies.