Gaps Of Different Sizes Research Articles

Can airborne laser scanning assist in mapping and monitoring natural forests?

Old-growth boreal forests display high within-stand structural variation, with large variation in tree sizes and age structure, a heterogeneous horizontal spatial pattern with gaps of different sizes and multi-layered canopies. Old managed forests, on the other hand, are characterized by more homogeneous structural patterns. In many parts of Europe, no true ‘virgin forests’ remains. Still, in many places forests previously influenced by selective logging have been abandoned, and is now developing towards a more natural forest structure. Such near-natural forest areas can be of special importance for forest biodiversity and related ecosystem services, and it is therefore important to map and monitor such forests. Recently, airborne laser scanning (ALS) has been applied to provide ecologically relevant information on forest structure. The advantage of ALS is that it can characterize three-dimensional forest structure in fine detail across broad areas, replacing more labour-intensive field-based measurements.In this study, we use ALS to compare the structural characteristics of 89 near-natural and 280 managed old forest stands in a 17,000ha boreal forest study site in southeastern Norway. For the study area, both maps of logging history separating old near-natural and old managed forests, and high-resolution ALS data was available.Our aim was to investigate if ALS data could be used to separate vertical and horizontal forest structure in old near natural versus old managed forests. We also wanted to compare different methods for classification, and to describe the potential for use of ALS in classification of forest naturalness for future mapping and monitoring purposes.We found that ALS data had a strong potential in separating stands of old near-natural forests from old managed stands. The most important metrics for classification were those reflecting canopy height, canopy density, variation in canopy height, number of trees per area and gap patterns. This fits well with ecological knowledge of relevant structural differences between forests of different degree of naturalness. Both vertical and horizontal metrics provided useful input to the classification, but the horizontal metrics performed slightly better on accuracy and were easier to interpret. Although the method has a good potential for wider use in boreal forest landscapes, the need for local reference data for calibration as well as the importance of ALS pulse density for precision of classification should be further investigated.Large-scale spatial information on remaining source areas of natural and near-natural forests will be essential in order to manage forests in a way that safeguards biodiversity and ecosystem services. We suggest that classification of forest naturalness based on ALS data can be a helpful tool in future forest mapping and monitoring.

Germination and establishment of natural red spruce (Picea rubens) seedlings in silvicultural gaps of different sizes

Red spruce (Picea rubens Sarg.) is difficult to regenerate from natural seeding following silvicultural treatment. In order to study its germination and establishment, we monitored the dynamics of new seedlings over 10 years in silvicultural gaps of different sizes (small: < 100 m2, medium: 100–300 m2, large: > 700 m2). Seedling density was higher in small gaps but survival rate did not exceed 40%, leaving few live seedlings after 10 years (< 200 ha-1). Mounds were the best microtopography for seedlings. Our results confirm the important role of decaying wood and moss for understory germination and establishment. Decaying wood was important for the establishment in large gaps while humus was more favourable in medium gaps. In small gaps, germinants and established seedlings were found as much on moss as humus and decaying wood. However, low observed densities suggest that planting in small or medium gaps should be explored for accelerating species renewal, especially if advance regeneration is deficient.

Effect of size and surrounding forest vegetation on chemical properties of soil in forest gaps

Abstract: Forest gaps have different microclimatic conditions as compared to the surrounding areas, depending on gap size and surrounding forest types and affecting the biological, chemical, physical, and hydrological processes in the forest openings. The objective of this study was to determine the effect of forest gap size and surrounding forest cover type (beech or mixed stands) on the soil of forest opening by analyzing several soil chemical soil properties (pH, electrical conductivity - EC, organic matter - OM, and nutrient content). The study was conducted in the Yuvacik watershed in Izmit (Turkey) and a total of 31 forest gaps of different size (1.44-37.33 ha) and elevations (848-1169 m a.s.l.) were studied. Gaps were divided into three groups with size 0-5 ha, 5-15 ha, and >15 ha. Results showed that forest gap size significantly affected all the investigated chemical properties of the soil, except for soil pH. As gap size increased, sodium (Na+) concentration in the soil decreased from 22.72 to 19.57 mg L-1 while potassium (K+) and magnesium (Mg+2) concentrations increased from 83.88 to 134.62 mg L-1 and from 59.46 to 123.96 mg L-1, respectively. Medium-sized gap soils had the lowest OM content, as well as the lowest calcium (Ca+2) and nitrogen (N+3) concentrations. Surrounding forest types significantly influenced soil chemical properties in the openings, except for EC, N+3, and phosphorus (P-PO4-3). Soils in the gaps surrounded by mixed forest had significantly lower pH but higher OM content, K+, Na+, Ca+2, and Mg+2 concentrations than soils in beech forest gaps.

A review of the roles of forest canopy gaps

Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to preserve bio- and pedo-diversity, influencing nutrient cycles, and maintaining the complex structure of the late-successional forests. Over the last 30 years, numerous reviews have been written describing gap dynamics. Here we synthesize current understanding on gap dynamics relating to tree regeneration with particular emphasis on gap characteristics considered critical to develop ecologically sustainable forest management systems and to conserve native biodiversity. Specifically, we addressed the question: how do gaps influence forest structure? From the literature reviewed, the size of gaps induces important changes in factors such as light intensity, soil humidity and soil biological properties that influence tree species regeneration and differ in gaps of different sizes. Shadetolerant species can colonize small gaps; shade-intolerant species need large gaps for successful regeneration. Additionally, gap dynamics differ between temperate, boreal, and tropical forests, showing the importance of climate differences in driving forest regeneration. This review summarizes information of use to forest managers who design cutting regimes that mimic natural disturbances and who must consider forest structure, forest climate, and the role of natural disturbance in their designs.

Effect of scarification on soil change and establishment of and artificial forest regeneration under Nothofagus spp. in Southern Chile

Soil scarification has been used as a silvicultura method to facilitate the regeneration of some forests, but it may have a negative impact on the properties of the soil. We evaluated the effect of a mechanized scarification on a volcanic soil after a shelterwood cutting in a Nothofagus spp. forest, located in the Andean region of southern Chile (39° 54 'S, 71° 56' 5 W, 970 m asl). A plantation of Nothofagus nervosa was established after scarification, and its physical (moisture content, bulk density, penetration resistance) and chemical (pH, organic matter, macro and microelements; saturation Al) soil properties were analyzed in scarified gaps and undisturbed forest. The size of N. nervosa planted trees was measured eleven months after their establishment (June 2010). The volumetric water content of the soil was similar with and without scarification (30-50%), regardless of the time of year. The bulk density was higher in the scarified soil when compared to the undisturbed forest. The soil nutrient supply in the gaps (0-20 cm) decreased when compared to the undisturbed forest (0-10 cm), but showed little difference between gaps and between locations within them. The N. nervosa plantation developed properly, with similar growth in gaps of different size. Scarification decreased soil quality; the effects on regeneration will need further evaluation throughout a longer period.

Plant diversity and seasonal dynamics in forest gaps of varying sizes in Pinus massoniana plantations

Aims Pinus massoniana is the major plantation tree species in the low hilly lands of the upper Yangtze river valley for commercial purpose. The large areas of plantations have caused serious ecological problems such as biodiversity decline and soil degradation. Our objectives were to study the dynamics of species composition and plant diversity in forest gaps, to test the hypothesis that forest gaps facilitate the regeneration and plant diversity in P. massoniana plantations, and to determine the size of forest gaps that harbors the most complex compositional structure and the greatest plant diversity. Methods We selected 39-year-old P. massoniana plantations with seven different gap sizes in the study, and used combination of systematic and representative sampling approaches. In the spring, summer, and autumn of 2013, sampling plots of the dimension 5 m × 5 m were laid out in the center of the forest gaps and under the canopy, and plants within each plot were surveyed for determination of their diversity and compositional structure. Important findings The understory of P. massoniana plantations were dominated by phanerophyte plants, followed by hemicryptophytes, geophytes, and therophyte plants. The phanerophyte plants were more abundant under the canopy than in forest gaps. The large gaps had more phanerophyte plants, while the geophytes and therophyte plants were less frequent under the canopy than in the small gaps. The species richness and diversity were significantly lower under the canopy than in the large forest gaps. Moreover, species richness, dominance, and diversity differed significantly among the forest gaps of different sizes. Seasonally, the highest diversity occurred in summer, followed by autumn, with the spring having the lowest diversity. The greatest diversity was found in the forest gaps of the size 1 225–1 600 m2, which could be the optimal gap size for facilitating plant diversity and regeneration of vegetation in P. massoniana plantations.

Positioning of cells flowing in a fluidic channel by negative dielectrophoresis

Control of the flow position of cells in a microchannel is useful for developing cell separation systems. We demonstrated that cells with different sizes were transported through different gaps by a repulsive force generated by negative dielectrophoresis (n-DEP). A device was fabricated by sandwiching a polyester film with a fluidic channel between upper and lower substrates with design same as that of navigator and separator electrodes which were used to concentrate the flowing cells in the center of the channel and to guide them to gaps of different sizes, respectively. The performance of the system was assessed using a human acute monocytic leukemia cell line (THP-1) and red blood cells (RBCs) from preserved equine blood as model cells. The cells flowed along the edges of navigator electrodes to concentrate in the center of the channel because of a strong repulsive force between the upper and lower substrates induced by the application of an AC electric field. THP-1 and RBCs passed through gaps of different sizes in a separator consisting of a microelectrode array. Passage efficiencies for THP-1 and RBCs through the desired gaps were found to be 88% and 44%, respectively. The results indicate the possibility of the continuous separation of cells with different sizes in the fluidic device based on n-DEP.

NATURAL REGENERATION OF GAPS IN A SELECTIVELY LOGGED AREA AT MORAPITIYA PROPOSED RESERVE.

Species composition and girth class distribution of pioneer (early successional) and climax (primary forest) tree species were investigated in gaps of different sizes created by selective logging in 1984-85 at Pitakele, Morapitiya proposed forest reserve, a lowland evergreen rain forest, in Ratnapura/ Kalutara districts.Eleven gaps of different sizes were selected for the study in 1992. In each gap, 9 plots of 2 by 2 metres, were demarcated along N-S and E-W directions. All species found in plots were recorded and identified. The height and girth of saplings and seedlings were also measured.There were 120 species, belonging to 84 genera and 44 families, found in all gaps. The ten dominant families were: Euphorbiaceae, Clusiaceae, Dipterocarpaceae, Melastomataceae, Myrtaceae, Sapotaceae, Lauraceae, Anacardiaceae, Annonaceae and Rubiaceae.There was a gradual increase in the number of pioneer species and their stem density from small to large gaps. However, this pattern was not shown by climax species. The number of climax species was higher at the periphery of large gaps than in the gap centre. The number of pioneer stems was higher at the centre of gaps. Light intensity (photosynthetically active radiation- PAR) varies within (centre and periphery) and between (small, medium and large) gaps.The gradual increase of number of pioneer species, which were not present before logging, is due to the increased light intensity and higher Red/ Far Red ratio. These conditions are essential for the germination of seeds of pioneer species in the soil seed bank. Seedlings and saplings of climax species found in undisturbed forest were found in all gaps (63- 620 m2 in size) selected for the present study. Further studies should investigate regeneration methods that allow fruit dispersal from a residual parent tree source, and that creates a below canopy radiation regime that initiates and then releases regeneration of tree species that ordinarily dominate the mature phase of a stand development. This needs partial opening of the canopy and sub-canopy which is banned at present under the moratorium on felling of natural forests.

A comparison of tree seedling growth in artificial gaps of different sizes in two contrasting forest types.

One of the major concerns in forestry in the tropics is the lack of information on the impact of canopy disturbance through logging. The degree of canopy opening that should be allowed during logging to enhance natural regeneration of timber tree species is not known. Information on the seedling ecology of individual species and ecological species groups on which to base management decisions are also lacking. Experiments to determine the ecophysiological responses of seedlings of timber tree species to different irradiances in two forest sites were carried out. The two forest reserves are Nkrabia and Tinte Bepo in the Moist Evergreen and Moist Semi-Deciduous Forest Types, respectively. Eight species, representing three Shade Bearers, four Non-Pioneer Light Demanders and one Pioneer species, were grown in a series of artificially-created gaps in two forest sites differing in annual rainfall. The forest shade received 1-2% irradiance, while the artificial gaps received 5, 10, 15, 30 and 65% irradiance. Seedling growth was greater at Nkrabia Forest Reserve (Moist Evergreen Forest Type) than at Tinte Bepo Forest Reserve (Moist Semi-Deciduous Forest Type). This is probably due to the lower soil moisture stress at Nkrabia as a result of more rainfall. Lower moisture stress at Nkrabia may also explain the greater leaf area and specific leaf area ratios, lower leaf turnover and lower number of small leaves on plants than those at Tinte Bepo. Response of height growth to irradiance of Shade Bearers and Non-Pioneer Light Demanders was similar but different from that of Pioneer species.

Long-period thermal oscillations in superfluid millisecond pulsars

In previous papers, we have shown that, as the rotation of a neutron star slows down, it will be internally heated as a consequence of the progressively changing mix of particles (rotochemical heating). In previously studied cases (non-superfluid neutron stars or superfluid stars with only modified Urca reactions), this leads to a quasi-steady state in which the star radiates thermal photons for a long time, possibly accounting for the ultraviolet radiation observed from the millisecond pulsar J0437-4715. For the first time, we explore the phenomenology of rotochemical heating with direct Urca reactions and uniform and isotropic superfluid energy gaps of different sizes. We first do exploratory work by integrating the thermal and chemical evolution equations numerically for different energy gaps, which uncovers a rich phenomenology of stable and unstable solutions. To understand these, we perform a stability analysis around the quasi-steady state, identifying the characteristic times of growing, decaying, and oscillating solutions. For small gaps, the phenomenology is similar to the previously studied cases, in the sense that the solutions quickly converge to a quasi-steady state. For large gaps ($\gtrsim 0.05$ MeV), these solutions become unstable, leading to a limit-cycle behavior of periodicity $\sim 10^{6-7} yr, in which the star is hot ($T_s\gtrsim 10^5$ K) for a small fraction of the cycle ($\sim 5- 20 %$), and cold for a longer time.

Effects of selective tree harvests on aboveground biomass and net primary productivity of a second-growth northern hardwood forest

Restoring structural features of old-growth forests, such as increased canopy gap sizes and coarse woody debris, is a common management goal for second-growth, even-aged stands. We experimentally manipulated forest structure by creating variable-size canopy gaps in a second-growth northern hardwood forest in north-central Wisconsin following two growing seasons of pre-treatment monitoring. The objectives of this study were to quantify the influence of canopy gaps of different sizes (50–380 m2) on aboveground biomass and productivity of each vegetation stratum two growing seasons following treatment. Two years after treatment, ground layer biomass in canopy openings increased significantly relative to surrounding undisturbed transition zones. The response of ground layer biomass was greatest in the large versus the medium and small gaps. Sapling aboveground net primary productivity was significantly greater in undisturbed transition zones than within gaps across gap sizes following the second post-treatment growing season. Annual stem diameter increment was greatest for trees along gap borders and was correlated with crown class, percentage of crown perimeter exposed, gap area, and shade tolerance. Total aboveground net primary productivity was significantly lower in the gap addition plots the first year but by the second post-treatment growing season no longer differed from that in the control plots.

Northward migrating trees establish in treefall gaps at the northern limit of the temperate–boreal ecotone, Ontario, Canada

Climate change is expected to promote migration of species. In ecotones, areas of ecological tension, disturbances may provide opportunities for some migrating species to establish in otherwise competitive environments. The size of and time since disturbance may determine the establishment ability of these species. We investigated gap dynamics of an old-growth red pine (Pinus resinosa Sol. ex Aiton) forest in the Great Lakes-St. Lawrence forest in northern Ontario, Canada, a transition zone between temperate and boreal forest. We investigated the effects of gaps of different sizes and ages on tree species abundance and basal area. Our results show that tree species from the temperate forest further south, such as red maple (Acer rubrum L.), red oak (Quercus rubra L.), and white pine (Pinus strobus L.), establish more often in large, old gaps; however, tree species that have more northern distributions, such as black spruce (Picea mariana Mill.), paper birch (Betula papyrifera Marsh.), and red pine show no difference in establishment ability with gap size or age. These differences in composition could not be attributed to autogenic succession. We conclude that treefall gaps in this forest facilitate the establishment of northward migrating species, potentially providing a pathway for future forest migration in response to recent changes in climate.

A new calculation method to estimate forest gap size

The distance and direction coordinates from the center of each canopy gap to its edge in sixteen compass directions were measured in the secondary forests. Total of 21 gaps of different sizes were measured. The gap size was determined using different calculation methods: octagon method (OM), which was applied with two compass directions (OM_1 and OM_2); sixteen-gon method (SM); and elliptical-sector method (ESM), a new calculation method proposed in this work, including 8-elliptical-sector (8ESM) with two different compass directions (8ESM_1 and 8ESM_2) and 16 elliptical sector (16ESM). The results indicated that within the same gap delimitation, the average estimated gap size varied from 122.0 to 164.4 m2 with different calculation methods. The estimated area of the same gap among all calculation methods and between pairs exhibited significant differences (p < 0.05). Particularly, the estimated area for the same gap was significantly different between OM_1 and OM_2 (p < 0.005), indicating that the starting direction of the OM significantly affected the gap size. However, there were no significant differences among applications of the new method. When SM is used as a standard, the gap size calculated by OM was 10.0% less but, by ESM, was 11.6% larger. Therefore, the new method is proposed for future research involving the gap size calculation. Finally, we concluded that a comparison of forest gap sizes, particularly using OM, should be conducted when discussing the effects of gaps on forest regeneration and succession.

Influence of Gap Size and Position within Gaps on Light Levels

The previous studies have reported maximum light levels at different positions within gaps but many of these studies are based on gaps of different size. The objective of this study is to evaluate the influence of gap size and position within gap on light distribution in gaps and under the canopy north of gaps in a mixedwood temperate forest. For three gap sizes, with gap widths ranging between 0.5 and 1.5 times the height of the surrounding stand, light was measured at different positions along the north-south axis in each gap using two different techniques (hemispherical photographs and instantaneous measurements). In small gaps, the position with the most light was close to the northern edge although not under the canopy north of the gap. For both methods, the position with the highest light level shifted from the north towards the center of gaps as gap size increased which clarifies some of the variability in light measurements previously observed in gap studies. Higher light levels in the northern part of small and medium gaps compared to the southern portion could allow management of a mixture of species with intolerant species in the northern portions of gaps and tolerant species to the south.

Quantification of annular flow in lined pipelines

This paper attempts to quantify the amount of flow within the annular space that could exist between a polymeric liner and a deteriorated host pipe. Inadequate fit of the liner within sewer line segments is likely to cause annular flow that will result in a higher flow rate within the wastewater collection system. The results of full-scale field tests performed by the authors on 12 pipelines lined with four different deformed/reformed or fold-and-form (DR/FF) and cured-in-place-pipe (CIPP) liner products indicated that gaps of different sizes existed in all of the tested pipelines. These gaps have resulted in variable annular flow in the tested pipelines. Based on the results of the full-scale tests, a mathematical relationship was established between the annular flow in a lined pipeline and the annular space. The relationship between the annular flow rate and the average annular gap size depends on the difference in head between the entry and exit points along the pipeline. In turn, the average annular gap size depends on many factors including tolerances and imperfections in the host pipe and liner, conditions of the host pipe and the quality of liner installation. A third-order polynomial equation was found to best describe the relationship between the annular flow and average gap size under high differential heads (up to 3.0 m or 10 ft); whereas, a logarithmic relationship fits best under low differential heads for wider range of annular gap sizes (up to 17.8 mm or 0.70 in.). Based on the results of the full-scale tests, this is believed to be more representative of typical liner installations.

Effects of gap size and within-gap position on seedlings establishment in silver fir stands

The conversion of pure conifer plantations into stands with heterogeneous structure and composition is a current silvicultural challenge in Italy. A silvicultural system aiming to the regeneration of natural forests by means of openings in the canopy cover is considered. The purposes of this study are: I) to evaluate if the creation of gaps is an appropriate way to transform homogeneous man-made stands of silver fir (Abies alba Mill.) into naturally regenerated stands; II) to analyse the influence of micro-environmental conditions in gaps of different size on the recruitment and establishment of natural regeneration of forest tree species. After three growing seasons silver fir seedlings recruitment was greater in small gaps and in the central-southern positions where PAR was lower and the shading influence of ground vegetation less relevant. The most suitable gap size for silver fir regeneration, in the southern Apennine, is 200 (300) m2, D/H = 0.5 and anyway <0.75. The silvicultural treatment proposed seems to foster natural regeneration of silver fir and other broadleaves, enhancing the development of a multi-layered forest structure and fulfilling timber production objectives without compromising ecosystem management principles.

From both sides now: crossover effects influence navigation in patients with unilateral neglect

Unilateral neglect is a challenging disorder that pervades a range of behaviours following stroke and hampers recovery. Although a preponderance of clinical studies measure performance on a range of bedside...

Growth in supplementarily planted Picea abies regenerations

An experiment was established in 1978 in two Norway spruce [Picea abies (L.) Karst.] plantations in southern Sweden to study yield after mortality in patches with and without supplementarily planted (SP) seedlings. Gaps of different sizes were created by removing the originally planted seedlings. The gaps were either left unplanted or a supplementary planting was performed with one of four species [Norway spruce, Scots pine (Pinus sylvestris L.), lodgepole pine (Pinus contorta Dougl.) or hybrid larch (Larix deciduas Mill×L. Leptolepis Gord.)] 2 (at Knäred) or 6 years (at Ullasjö) after the original plantation. In 2002, most of the SP Scots pine, lodgepole pine and hybrid larch seedlings were dead or severely damaged by roe deer and moose. Survival was high among SP Norway spruces, but they had slower growth than the originally planted spruces. Growth was lower at Ullasjö than at Knäred. In Ullasjö, growth was lower in small gaps than in large gaps. Trees in original regeneration in areas surrounding unplanted gaps were larger than trees surrounding gaps with SP seedlings, which in turn were larger than originally planted trees in plots without gaps. In conclusion, because the original plantation surrounding unplanted gaps used a large part of the open space and growth of SP seedlings was slow, supplementary planting resulted in an insignificant growth increase. However, supplementary planting may increase the timber quality of trees surrounding the gaps, although this effect remains to be quantified.

Influence of gap size on organic matter decomposition, microbial biomass and nutrient cycle in Calabrian pine ( Pinus laricio, Poiret) stands

The present study aimed to examine the impacts of small (380 m 2), medium (855 m 2) and large (1520 m 2) gaps on microclimate, soil properties and microbial biomass, a ‘sink’ and ‘source’ of plants nutrients, in Pinus nigra ( Pinus laricio Poiret) stands in Calabrian Apennine Southern Italy. PAR transmittance significantly increased with increasing size of the gaps, consequently an effect of gaps size was found on microclimate: soil moisture and temperature were different among the gaps of different size showing the highest values of temperature in the large gaps and the highest values of moisture in the small gaps. Within small gaps the greatest amount of organic matter, humic matter and microbial biomass, and the highest C/N value were observed. The highest values of phosphatases, urease and FDA activities were detected in small gaps. An impact of gap size on C, N and P cycles was significant in small gaps in terms of higher availability of these nutrients and greater amount of humic matter, suggesting that small gaps may be important from an ecosystem perspective representing the appropriate management procedures for an adequate conservation of ecological functions, capable to preserve soil properties and favour Pinus laricio natural regeneration.

A bounded null model explains juvenile tree community structure along light availability gradients in a temperate rain forest

Ecologists have proposed that tree species may coexist by specialising on light environments associated with gaps of different sizes. Remarkably few community‐level studies, however, have actually examined juvenile tree distributions along light availability gradients. Here we describe distributions of juvenile trees in relation to canopy openness in a temperate rainforest, and test the hypothesis that competitive sorting causes coexisting species to overlap less in light environment occupancy than would be expected by chance. Average overlap of species’ interquartile ranges on the canopy openness gradient was tested against a bounded domain null model of community structure which used range‐size criteria to constrain random placement of species optima. Microsite availability was strongly skewed towards low light, with 43% of microsites occurring at &lt;5% canopy openness. We therefore transformed canopy openness values to ranks, so that equal intervals on the transformed gradient represented equal areas of microsite availability. We then calculated the interquartile range (25–75%) of sample ranks occupied by juveniles of each species. About half the assemblage was non‐randomly distributed in relation to canopy openness, providing evidence of niche expression. Average overlap of species’ interquartile ranges did not depart significantly from that predicted by the bounded null model, indicating that community structure in relation to canopy openness was mainly explained by a mid‐domain effect. As predicted by the null model, species’ interquartile range mid‐points were concentrated in the centre of the rank‐transformed gradient, and species richness (overlap of interquartile ranges) peaked close to the median light environment. Most species therefore had intermediate light requirements. The apparent lack of constraints on pairwise overlap suggest that differences in light use are not a prerequisite for tree species coexistence. As far as we are aware, this is the first study to identify a mid‐domain effect on a resource availability axis.