Canopy Environment Research Articles

Effect of canopy condition on Machilus nanmu seedling configuration and biomass allocation

The adaptation strategy of seedlings plays a decisive role in population regeneration. Machilus nanmu is a tree species belonging to Lauraceae, which is national class Ⅱ protected species and one of the dominant species in the evergreen broadleaved forest in Jinyun Mountain, Chongqing. Therefore, it is of great significance to understand the adaptation strategies of M. nanmu seedlings to maintain population regeneration and protect the biodiversity of evergreen broadleaved forest. We studied the temporal dynamics of early adaptation strategy of M. nanmu in Jinyun Mountain in Chongqing and its response to heterogeneous habitats from the perspective of morphology and biomass allocation. The seedlings of M. nanmu were classified into different age stages (stage 1: 1-3 a; stage 2: 4-6 a; stage 3: 7-9 a) under different canopy environments (gap/understory). Stem configurations (except branch angle) and leaf inclination angle of M. nanmu seedlings in the gap were significantly greater than understory at stages 2 and 3. Root configurations (except root diameter) and leaf area were significantly greater than that in the understory at stages 1 and 2. Specific leaf area in the gap was significantly smaller than understory at all three stages. Across all the conditions, biomass distribution was dominated by leaves. From the stage 2, stem biomass distribution of M. nanmu seedlings in the gap was increased, while root biomass distribution was decreased. There was no significant variation in root biomass of M. nanmu seedlings in the understory. The coordination among different organs of M. nanmu seedlings would help their adaptation to different habitats. Root and leaf of M. nanmu seedlings in the gap were significantly correlated, with the correlation changing from positive to negative as the age increased. While in the understory, there was significant positive correlation between root and stem, but no correlation between root and leaf. The slope of SMA equation of branch weight and branch length had significant difference under different canopy environments only at stage 3, while the slope of SMA equation of leaf and root biomass and configuration had no significant difference. Most of the SMA equation intercepts between biomass and configuration differed significantly at stage 2.

The impact of logging on vertical canopy structure across a gradient of tropical forest degradation intensity in Borneo

Abstract Forest degradation through logging is pervasive throughout the world's tropical forests, leading to changes in the three‐dimensional canopy structure that have profound consequences for wildlife, microclimate and ecosystem functioning. Quantifying these structural changes is fundamental to understanding the impact of degradation, but is challenging in dense, structurally complex forest canopies. We exploited discrete‐return airborne LiDAR surveys across a gradient of logging intensity in Sabah, Malaysian Borneo, and assessed how selective logging had affected canopy structure (Plant Area Index, PAI, and its vertical distribution within the canopy). LiDAR products compared well to independent, analogue models of canopy structure produced from detailed ground‐based inventories undertaken in forest plots, demonstrating the potential for airborne LiDAR to quantify the structural impacts of forest degradation at landscape scale, even in some of the world's tallest and most structurally complex tropical forests. Plant Area Index estimates across the plot network exhibited a strong linear relationship with stem basal area (R2 = 0.95). After at least 11–14 years of recovery, PAI was ~28% lower in moderately logged plots and ~52% lower in heavily logged plots than that in old‐growth forest plots. These reductions in PAI were associated with near‐complete lack of trees >30‐m tall, which had not been fully compensated for by increasing plant area lower in the canopy. This structural change drives a marked reduction in the diversity of canopy environments, with the deep, dark understorey conditions characteristic of old‐growth forests far less prevalent in logged sites. Full canopy recovery is likely to take decades. Synthesis and applications. Effective management and restoration of tropical forests requires detailed monitoring of the forest and its environment. We demonstrate that airborne LiDAR can effectively map the canopy architecture of the complex tropical forests of Borneo, capturing the three‐dimensional impact of degradation on canopy structure at landscape scales, therefore facilitating efforts to restore and conserve these ecosystems.

Water stress modifies canopy light environment and qualitative and quantitative yield components in two soybean varieties

The influence of three levels of water supply (unlimited (WW); water stress during flowering (RO); rainfed (P)) on radiation properties and yield of two soybean varieties (Sinara, Sin; Sigalia, Sig) were evaluated. Sin is considered to be tolerant to water stress. The effect of leaf area index, year, variety, and meteorological variables on evapotranspiration (ET) was analysed by hierarchical regression. This study attempted to identify how water supply affects the crop–light relationship between photosynthetically active radiation (PAR) transmission and radiation use efficiency (RUE), which were involved in qualitative and quantitative traits related to soybean production (biomass and yield attributes: seed yield, 1000-grain weight, oil and protein content). Unstandardized coefficients of air temperature (Ta) showed that a 1 °C increase in daily mean Ta induced a higher ET, on average 0.16 mm day−1. Soil moisture strongly affected sowing time. When averaged across three seasons at flowering, 97.7, 95.1 and 97.3% of incoming PAR were intercepted by the canopies of plants in WW, RO and P, respectively. The average extinction coefficient (k) and RUE pooled across both varieties were 0.42 and 1.32 g MJ PAR−1 for WW, and 0.46 and 0.98 g MJ PAR−1 for RO, respectively, compared with 0.44 and 1.15 g MJ PAR−1 for P. As expected, water treatment significantly affected all yield traits: RO decreased yield whereas WW increased yield compared to P. Practically, both varieties are suitable for cultivation under water stress during flowering but Sin showed greater yield under unlimited watering and rainfed conditions.

Jeannine Cavender-Bares.

Jeannine Cavender-Bares.

Leaf trait co‐variation and trade‐offs in gallery forest C3 and CAM epiphytes

AbstractDespite their unique adaptations to thrive in canopy environments without access to soil resources, epiphytes are underrepresented in studies of functional traits and of functional composition of tropical plant communities. We investigated functional traits of spermatophytic (seed‐bearing) C3 and CAM epiphyte communities in flooded and non‐flooded gallery forests in Central Brazil. The two forest types differ in floristic, structure, microclimate, and edaphic conditions. We studied plant size, leaf thickness, leaf dry matter content (LDMC), leaf water content, leaf area (LA), specific leaf area (SLA), leaf C, N, P, K, Mg, and Ca, and stable isotope ratios (δ13C and δ15N). Because photosynthetic pathway (C3 or CAM) is an important aspect of ecological differentiation for spermatophytic epiphytes, we expected that functional trait syndromes in a multivariate space would be more associated with photosynthetic pathway than forest type, and changes in abundance of C3 and CAM epiphytes would drive functional trait composition at the community level. C3 and CAM epiphytes segregated in the multivariate trait space; however, more complex functional typologies were also evident. Despite lower light levels, CAM epiphytes were more abundant in the flooded gallery forest. There, they accounted for 80% of all individuals, whereas C3 epiphytes dominated in the non‐flooded forest. These large differences in the proportion of CAM and C3 epiphytes strongly affected functional trait values at the community level, despite very little intraspecific variation in trait values between forest types for species that occurred in both forests.Abstract in Portuguese is available with online material.

Investigation of the Factors Affecting Artificial Seed Sowing Success and Seedling Survival in Pinus brutia Natural Stands in Middle Elevations of Central Cyprus

The aim of this study was to analyze the germination of Pinus brutia Ten. seeds, in the field, in relation to factors such as period of sowing, light environment, and watering, in sites of different productivity in the middle elevations in central Cyprus. Two sowing experiments were conducted in three sites of different productivity. In the first experiment P. brutia seed sowing took place in February 2009 in two sowing environments which were gap and under canopy environments. The shade conditions in those environments were determined using hemispherical photographs. Also, the influence of watering on the seed germination was checked. In the second experiment, which was established in the same areas as in the first experiment, the seed sowing took place in December 2009. However, in this case, no watering was applied during the germination period. Moreover, the survival of the seedlings from both sowing periods were monitored up to the end of 2010. During the period of monitoring, the influence of watering was checked. The germination rates of seeds from the February sowing were very low. On the contrary, from the December sowing, the germination rates of seeds were very high in both sowing environments in all studied sites. In the case of seedling survival from the February and December sowing, mortality rates were relatively high in all sites except from the under-canopy sowing environment where watering was applied in the medium productivity site. From the December sowing, from a practical point of view, the number of survived seedlings, in all the plots of the three sites can be considered adequate for the successful regeneration of P. brutia.

A comparative gene co-expression analysis using self-organizing maps on two congener filmy ferns identifies specific desiccation tolerance mechanisms associated to their microhabitat preference

BackgroundFilmy-ferns (Hymenophyllaceae) are poikilohydric, homoiochlorophyllous desiccation-tolerant (DT) epiphytes. They can colonize lower and upper canopy environments of humid forest. Filmy-ferns desiccate rapidly (hours), contrasting with DT angiosperms (days/weeks). It has been proposed that desiccation tolerance in filmy-ferns would be associated mainly with constitutive features rather than induced responses during dehydration. However, we hypothesize that the inter-specific differences in vertical distribution would be associated with different dynamics of gene expression within the dehydration or rehydration phases. A comparative transcriptomic analysis with an artificial neural network was done on Hymenophyllum caudiculatum (restricted to lower canopy) and Hymenophyllum dentatum (reach upper canopy) during a desiccation/rehydration cycle.ResultsRaw reads were assembled into 69,599 transcripts for H. dentatum and 34,726 transcripts for H. caudiculatum. Few transcripts showed significant changes in differential expression (DE). H. caudiculatum had ca. twice DE genes than H. dentatum and higher proportion of increased-and-decreased abundance of genes occurs during dehydration. In contrast, the abundance of genes in H. dentatum decreased significantly when transitioning from dehydration to rehydration. According to the artificial neural network results, H. caudiculatum enhanced osmotic responses and phenylpropanoid related pathways, whilst H. dentatum enhanced its defense system responses and protection against high light stress.ConclusionsOur findings provide a deeper understanding of the mechanisms underlying the desiccation tolerance responses of two filmy ferns and the relationship between the species-specific response and the microhabitats these ferns occupy in nature.

Fungal diversity in canopy soil of silver beech, Nothofagus menziesii(Nothofagaceae).

Adventitious roots in canopy soils associated with silver beech (Nothofagus menziesii Hook.f. (Nothofagaceae)) form ectomycorrhizal associations. We investigated the extent to which canopy ectomycorrhizal communities contribute to overall diversity of ectomycorrhizal fungi associated with silver beech. Hyphal ingrowth bags were buried for 12 months in canopy and terrestrial soils of five trees at one site. We used amplicon sequencing of the nuclear ribosomal internal transcribed spacer 2 region (ITS2) to assess diversity of both ectomycorrhizal and non-ectomycorrhizal OTUs in hyphal ingrowth bags. There was a significant difference in ectomycorrhizal fungal community diversity between the terrestrial and canopy hyphal ingrowth bag communities. Ectomycorrhizal community composition of the terrestrial and canopy environments was also significantly different. Some ectomycorrhizal taxa were significantly differentially represented in either the terrestrial or canopy environment. The hyphal ingrowth bags also accumulated non-ectomycorrhizal species. The non-ectomycorrhizal fungi also had significantly different diversity and community composition between the canopy and terrestrial environments. Like the ectomycorrhizal community, some non-ectomycorrhizal taxa were significantly differentially represented in either the terrestrial or canopy environment. The canopy soil microhabitat provides a novel environment for growth of ectomycorrhizal adventitious roots and enables the spatial partitioning of ectomycorrhizal and non-ectomycorrhizal fungal diversity in the forest.

Canopy parkour: movement ecology of post-hatch dispersal in a gliding nymphal stick insect, Extatosoma tiaratum.

For flightless arboreal arthropods, moving from the understory into tree canopies is cognitively and energetically challenging because vegetational structures present complex three-dimensional landscapes with substantial gaps. Predation risk and wind-induced perturbations in the canopy may further impede the movement process. In the Australian stick insect Extatosoma tiaratum, first-instar nymphs hatch on the forest floor and disperse toward tree canopies in the daytime. Here, we addressed how their tactic responses to environmental cues and movement strategies are adapted to the canopy environment. Newly hatched nymphs ascend with high endurance, travelling >100 m within 60 min. Navigation toward open canopies is underpinned by negative gravitaxis, positive phototaxis and visual responses to vertically oriented contrast patterns. Nymphal E. tiaratum also use directed jumping to cross gaps, and respond to tactile stimulation and potential threat with a self-dropping reflex, resulting in aerial descent. Post-hatch dispersal in E. tiaratum thus consists of visually mediated displacement both on vegetational structures and in the air; within the latter context, gliding is then an effective mechanism enabling recovery after predator- and perturbation-induced descent. These results further support the importance of a diurnal niche, in addition to the arboreal spatial niche, in the evolution of gliding in wingless arboreal invertebrates.

Different community crown layer environment under purple ear arrow bamboo shoots of growth development research

<p>The Jinfo Mountain National Nature Reserve in 3A different type community (deciduous broad-leaved forest, Evergreen deciduous broad-leaved mixed forest, Evergreen broad-leaved forest) under purple ear fargesia (<em>Fargesia decurvata</em> J.L.Lu) Young are of Growth Development Research. Results display: (1) Deciduous broad-leaved forest and evergreen deciduous broad-leaved mixed forest under the purple ear fargesia shooting of early and long duration 110 d Shooting large shooting rate is high; evergreen broad-leaved forest under the shooting of late and short duration 88 D Shooting less shooting rate low; evergreen deciduous broad-leaved mixed forest in the shooting of maximum. (2) Shooting period is divided 3A stage: early stage and the end the community in purple ear fargesia into each period of time have difference evergreen deciduous broad-leaved mixed forest in the first to enter the shooting stage deciduous broad-leaved forest followed by evergreen broad-leaved forest. Shooting stage is also back are the peak back are rate of size for: evergreen deciduous broad-leaved mixed forest > Deciduous broad-leaved forest>Evergreen broad-leaved forest. (3) The same community crown layer environment under purple ear fargesia Different Period Unearthed of young are ground diameter no significant difference. In deciduous broad-leaved forest and evergreen deciduous broad-leaved mixed forest canopy environment in the Period Unearthed of young are ground diameter between no significant difference but were significantly greater than the evergreen broad-leaved forest (<em>P</em> < 0.05). (4) Purple ear fargesia young are unearthed after 80 d About complete high growth process and in line Logistic Equation was Slow-Fast-Slow Of growth trend. High growth rate for: evergreen deciduous broad-leaved mixed forest > Deciduous broad-leaved forest > Evergreen broad-leaved forest and difference significant (<em>P</em> < 0.05). (5) Purple ear understory of bamboo cloning reproduction and ramet density between have close relationship. With the ramets density of increase shooting quantity increase bamboo quantity reduce. This study show that different Community crown layer environment under purple ear bamboo growth development significant difference in evergreen deciduous broad-leaved mixed forest in development best evergreen broad-leaved forest in development worst, population density of bamboo of update development the important regulation role.</p>

Leaf reflectance spectroscopy captures variation in carboxylation capacity across species, canopy environment and leaf age in lowland moist tropical forests.

Understanding the pronounced seasonal and spatial variation in leaf carboxylation capacity (Vc,max ) is critical for determining terrestrial carbon cycling in tropical forests. However, an efficient and scalable approach for predicting Vc,max is still lacking. Here the ability of leaf spectroscopy for rapid estimation of Vc,max was tested. Vc,max was estimated using traditional gas exchange methods, and measured reflectance spectra and leaf age in leaves sampled from tropical forests in Panama and Brazil. These data were used to build a model to predict Vc,max from leaf spectra. The results demonstrated that leaf spectroscopy accurately predicts Vc,max of mature leaves in Panamanian tropical forests (R2 =0.90). However, this single-age model required recalibration when applied to broader leaf demographic classes (i.e. immature leaves). Combined use of spectroscopy models for Vc,max and leaf age enabled construction of the Vc,max -age relationship solely from leaf spectra, which agreed with field observations. This suggests that the spectroscopy technique can capture the seasonal variability in Vc,max , assuming sufficient sampling across diverse species, leaf ages and canopy environments. This finding will aid development of remote sensing approaches that can be used to characterize Vc,max in moist tropical forests and enable an efficient means to parameterize and evaluate terrestrial biosphere models.

Bryophytes in fir waves: Forest canopy indicator species and functional diversity decline in canopy gaps

AbstractAimsBryophytes can cover three quarters of the ground surface, play key ecological functions, and increase biodiversity in mesic high‐elevation conifer forests of the temperate zone. Forest gaps affect species coexistence (and ecosystem functions) as suggested by the gap and gap‐size partitioning hypotheses (GPH, GSPH). Here we test these hypotheses in the context of high‐elevation forest bryophyte communities and their functional attributes.Study SiteSpruce–fir forests on Whiteface Mountain, NY, USA.MethodsWe characterized canopy openness, microclimate, forest floor substrates, vascular vegetation cover, and moss layer (cover, common species, and functional attributes) in three canopy openness environments (gap, gap edge, forest canopy) across 20 gaps (fir waves) (n = 60); the functional attributes were based on 16 morphologic, reproductive, and ecological bryophyte plant functional traits (PFTs). We tested GPH and GSPH relative to bryophyte community metrics (cover, composition), traits, and trait functional sensitivity (functional dispersion; FDis) using indicator species analysis, ordination, and regression.ResultsCanopy openness drove gradients in ground‐level temperature, substrate abundance and heterogeneity (beta diversity), and understory vascular vegetation cover. The GPH was consistent with (a) the abundance patterns of forest canopy indicator species (Dicranum fuscescens, Hypnum imponens, and Tetraphis pellucida), and (b) FDis based on three PFTs (growth form, fertility, and acidity), both increasing with canopy cover. We did not find support for GPH in the remaining species or traits, or for GSPH in general; gap width (12–44 m) was not related to environmental or bryophyte community gradients.ConclusionsThe observed lack of variation in most bryophyte metrics across canopy environments suggests high resistance of the bryophyte layer to natural canopy gaps in high‐elevation forests. However, responses of forest canopy indicator species suggest that canopy mortality, potentially increased by changing climate or insect pests, may cause declines in some forest canopy species and consequently in the functional diversity of bryophyte communities.

Do genetically-specific tree canopy environments feed back to affect genetically specific leaf decomposition rates?

In forest ecosystems, trees may have genetically distinct patterns in leaf decomposition. Trees also can have genetically distinct canopy environments which modify temperature, moisture, and microbial communities on the forest floor. The interaction between these factors may result in underexplored interactions between microenvironment and leaf decomposition at the genotype level. We compare litter decomposition rates for distinct genotypes of Fremont cottonwood (Populus fremontii) grown in a common garden environment under three different riparian conditions: 1) under a 16-tree stand of the same genotype, 2) under a 16-tree stand of another genotype, and 3) under a 16-tree stand of 16 different genotypes. Genotypes differed in canopy size and phenology. While genotype exerted a strong effect on decomposition, this effect was most pronounced when litter was decomposed under a self-similar (“home”) canopy. The strongest driver of decomposition rates across all factors (including litter quality and environmental factors) was spring (leaf-out) and fall (leaf-drop) phenology, but responses were variable by genotype. The influence of genetics on litter decomposition, canopy environment, and tree phenology provides justification for the inclusion of stand-level traits like canopy cover into models of decomposition and complicates the results of studies that rely on litter quality traits alone.

Effects of bud-flushing strategies on tree growth.

Allocation of carbohydrates between competing organs is fundamental to plant development, growth and productivity. Carbohydrates are synthesized in mature leaves and distributed via the phloem vasculature to developing buds where they are consumed to produce new biomass. The distribution and mass-allocation processes within the plant remain poorly understood and may involve complex feedbacks between different plant functions, with implications for the emergent structure of the plant. Here, we investigate how the order in which dormant buds are flushed affects the development of tree size and reproductive output during the first 20 years of growth in full light and shaded canopy environments. We report the following findings: (i) Bud-flushing strategies strongly affect the temporal dynamics of height, mass and the size of reproduction pool, as well as the resulting architectures. (ii) Bud-flushing strategies affect tree growth by altering the rate of growth and final size of trees. (iii) No single bud-flushing strategy performs best when both the size and allocation for reproduction of the resulting trees are compared. However, we observe that the strategy that optimizes the net carbon gain for the entire tree architecture always results in a high reproduction output. (iv) Branch turnover and meristem regeneration enhance the performance of certain strategies with respect to the measured quantities. These results highlight the importance of employing generic models of architecture (i.e., non-species-specific) to identify general mechanisms of carbon allocation and the spatial distribution of newly formed biomass in growing trees.

Effects of bud-flushing strategies on tree growth.

Allocation of carbohydrates between competing organs is fundamental to plant development, growth and productivity. Carbohydrates are synthesized in mature leaves and distributed via the phloem vasculature to developing buds where they are consumed to produce new biomass. The distribution and mass-allocation processes within the plant remain poorly understood and may involve complex feedbacks between different plant functions, with implications for the emergent structure of the plant. Here, we investigate how the order in which dormant buds are flushed affects the development of tree size and reproductive output during the first 20 years of growth in full light and shaded canopy environments. We report the following findings: (i) Bud-flushing strategies strongly affect the temporal dynamics of height, mass and the size of reproduction pool, as well as the resulting architectures. (ii) Bud-flushing strategies affect tree growth by altering the rate of growth and final size of trees. (iii) No single bud-flushing strategy performs best when both the size and allocation for reproduction of the resulting trees are compared. However, we observe that the strategy that optimizes the net carbon gain for the entire tree architecture always results in a high reproduction output. (iv) Branch turnover and meristem regeneration enhance the performance of certain strategies with respect to the measured quantities. These results highlight the importance of employing generic models of architecture (i.e., non-species-specific) to identify general mechanisms of carbon allocation and the spatial distribution of newly formed biomass in growing trees.

Seed Germination Requirements of Ficus virens (Moraceae) as Adaptation to Its Hemi-Epiphyte Life Form

Epiphytes and hemi-epiphytes are important floristic, structural and functional components of tropical rainforests. Their specific responses to light, temperature and water conditions during seed germination allow them to coexist with tropical forest trees. Here we investigated the effects of temperature, red to far-red light ratio (R:FR ratio) and water stress on seed germination of Ficus virens in tropical seasonal rainforest in Southwest China. We used incubators to create required temperature regimes, polyester filters to produce R:FR ratio gradients and mannitol solutions to simulate water stress. It was found that seed germination of F. virens was inhibited in the simulated understory conditions, i.e., at lower temperature (22/23°C), especially when combined with the R:FR ratio of 0.25, for which the germination percentage was less than 20%. In contrast, the seed germination percentages in the simulated canopy environment (22/32°C) showed no significant difference between R:FR ratios, with an average seed germination percentage as high as 65.8%. Seed germination delayed and decreased along with increasing water stress and was completely inhibited at -2.5 MPa, which might suggest that it is a kind of adaptation for F. virens seeds to detect the rainy season as germination chance on the canopy. Therefore, our study revealed the physiological mechanism for F. virens to be able to adapt to canopy environment.

Isoprene emission potentials from European oak forests derived from canopy flux measurements: an assessment of uncertainties and inter-algorithm variability

Abstract. Biogenic emission algorithms predict that oak forests account for ∼ 70 % of the total European isoprene budget. Yet the isoprene emission potentials (IEPs) that underpin these model estimates are calculated from a very limited number of leaf-level observations and hence are highly uncertain. Increasingly, micrometeorological techniques such as eddy covariance are used to measure whole-canopy fluxes directly, from which isoprene emission potentials can be calculated. Here, we review five observational datasets of isoprene fluxes from a range of oak forests in the UK, Italy and France. We outline procedures to correct the measured net fluxes for losses from deposition and chemical flux divergence, which were found to be on the order of 5–8 and 4–5 %, respectively. The corrected observational data were used to derive isoprene emission potentials at each site in a two-step process. Firstly, six commonly used emission algorithms were inverted to back out time series of isoprene emission potential, and then an average isoprene emission potential was calculated for each site with an associated uncertainty. We used these data to assess how the derived emission potentials change depending upon the specific emission algorithm used and, importantly, on the particular approach adopted to derive an average site-specific emission potential. Our results show that isoprene emission potentials can vary by up to a factor of 4 depending on the specific algorithm used and whether or not it is used in a big-leaf or canopy environment (CE) model format. When using the same algorithm, the calculated average isoprene emission potential was found to vary by as much as 34 % depending on how the average was derived. Using a consistent approach with version 2.1 of the Model for Emissions of Gases and Aerosols from Nature (MEGAN), we derive new ecosystem-scale isoprene emission potentials for the five measurement sites: Alice Holt, UK (10 500 ± 2500 µg m−2 h−1); Bosco Fontana, Italy (1610 ± 420 µg m−2 h−1); Castelporziano, Italy (121 ± 15 µg m−2 h−1); Ispra, Italy (7590 ± 1070 µg m−2 h−1); and the Observatoire de Haute Provence, France (7990 ± 1010 µg m−2 h−1). Ecosystem-scale isoprene emission potentials were then extrapolated to the leaf-level and compared to previous leaf-level measurements for Quercus robur and Quercus pubescens, two species thought to account for 50 % of the total European isoprene budget. The literature values agreed closely with emission potentials calculated using the G93 algorithm, which were 85 ± 75 and 78 ± 25 µg g−1 h−1 for Q. robur and Q. pubescens, respectively. By contrast, emission potentials calculated using the G06 algorithm, the same algorithm used in a previous study to derive the European budget, were significantly lower, which we attribute to the influence of past light and temperature conditions. Adopting these new G06 specific emission potentials for Q. robur (55 ± 24 µg g−1 h−1) and Q. pubescens (47 ± 16 µg g−1 h−1) reduced the projected European budget by ∼ 17 %. Our findings demonstrate that calculated isoprene emission potentials vary considerably depending upon the specific approach used in their calculation. Therefore, it is our recommendation that the community now adopt a standardised approach to the way in which micrometeorological flux measurements are corrected and used to derive isoprene, and other biogenic volatile organic compounds, emission potentials.

Effect of micrometeorological parameters on aphid and white rust epidemiology under different row direction in oilseed Brassica

Globally rapeseed-mustard (Brassica spp.) is a major oilseed crop. India is the second largest cultivator of mustard followed by China. The oilseed production increased significantly after yellow revolution but increasing population made pressure on production. The major losses in mustard yield occurs due to the attack of different pest and diseases. An option to minimize the losses in production of oilseed Brassica can be the suppression of the pest and disease incidence through modification of microclimate by altering the crop row direction. This experiment was conductedto evaluate the impact of microclimate variability due to different crop row directions on pest and disease incidence. The pest and disease are highly sensitive to temperature and relative humidity (RH) within crop canopy environment. The two row direction treatment, i.e. North-South (N-S) and East-West (E-W) were studied at the experimental farm, ICAR-IARI, New Delhi during rabi season, 2013-14. Parameters like number of aphid per top 10 cm of main shoot, per cent disease index (PDI) of white rust, temperature and RH within crop canopy were recorded at regular interval. The result showed a significant higher value of mean profile temperature in N-S row direction as compared to E-Wrow direction and an opposite trend was found for RH. Aphid infestation and PDI for white rust infection in E-W direction were significantly higher by 36% and 11.44%, respectively over N-S direction. It was concluded that both aphid and white rust incidence were reduced in N-S direction due to microenvironment modification. Aphid population was found negatively correlated with mean profile temperature and positively correlated with RH..

Human bipedal instability in tree canopy environments is reduced by \u201clight touch\u201d fingertip support

Whether tree canopy habitats played a sustained role in the ecology of ancestral bipedal hominins is unresolved. Some argue that arboreal bipedalism was prohibitively risky for hominins whose increasingly modern anatomy prevented them from gripping branches with their feet. Balancing on two legs is indeed challenging for humans under optimal conditions let alone in forest canopy, which is physically and visually highly dynamic. Here we quantify the impact of forest canopy characteristics on postural stability in humans. Viewing a movie of swaying branches while standing on a branch-like bouncy springboard destabilised the participants as much as wearing a blindfold. However “light touch”, a sensorimotor strategy based on light fingertip support, significantly enhanced their balance and lowered their thigh muscle activity by up to 30%. This demonstrates how a light touch strategy could have been central to our ancestor’s ability to avoid falls and reduce the mechanical and metabolic cost of arboreal feeding and movement. Our results may also indicate that some adaptations in the hand that facilitated continued access to forest canopy may have complemented, rather than opposed, adaptations that facilitated precise manipulation and tool use.

Patterns of phylogenetic relatedness of angiosperm woody plants across biomes and life‐history stages

AbstractAimThe tropical niche conservatism (TNC) hypothesis predicts that species in colder or drier climates should on average be more closely related to each other (more phylogenetically clustered) than those in warmer or wetter climates, but a global test of this prediction for local forest communities is lacking. In this study, we test this prediction by analysing a comprehensive dataset of forest communities that covers all forest biomes across the world. Furthermore, within a forest community, vegetation layers from understorey to canopy could be considered a gradient of biotic interaction, on one hand, and an environmental gradient, on the other hand. We assess trends of phylogenetic relatedness of tree species across strata of forests in different forest biomes across the world.LocationGlobal.MethodWe analysed 186 forest plots, each being 0.1 ha in size. For each forest plot, we divided stems into three stem‐size classes. Net relatedness index (NRI) and nearest taxon index (NTI) for angiosperm woody plant assemblages were calculated for each forest plot and for each stem‐size class of the plot. NRI and NTI of forest plots were related to temperature and precipitation in the framework of Whittaker's biome system.ResultsWhen both deep and shallow evolutionary histories of woody species were considered, angiosperm woody plants tended to be more closely related in colder and/or drier climates. Phylogenetic relatedness was greater (i.e. more phylogenetic clustering) among trees with larger stems than among trees with smaller stems at the global scale.Main conclusionsOur finding that species are more closely related towards colder and/or dryer biomes is consistent with the prediction of the TNC hypothesis. The pattern of increasing phylogenetic relatedness towards the upper canopy layer of a forest is stronger in temperate compared to tropical regions, suggesting stronger environmental filtering in the more stressful canopy environment.