Specific Leaf Mass Research Articles

How the vertical gradient of light in the understorey and water seasonality affect leaf traits of Vanilla phaeantha (Orchidaceae), a crassulacean acid metabolism (CAM) hemiephyte.

Structural and physiological leaf traits and their plasticity were compared in the hemiepiphyte Vanilla phaeantha . This species grows along a phorophyte reaching different understorey positions and exhibiting diverse responses to environment changes. We analysed three height strata above the ground, establishing a light gradient, and considering seasonal water fluctuations. The upper leaves had higher area and mass and were less pigmented. The dry season induced a reduction of approximately 2h of stomatal opening over the diel 24h crassulacean acid metabolism (CAM) cycle in the leaves at all understorey positions. The leaves more exposed to sunlight were larger with higher titratable acidity during the rainy season, while the leaves near the ground maintained the same rates of stomatal conductance and nocturnal acidification between seasons, with lowest values of carbon isotopes in the rainy season. Our research showed that some structural leaf traits (such as specific leaf mass, biomass, and saturated water content) are sensitive to variation in understorey position. In contrast, other physiological traits (stomatal conductance, transpiration, and fluorescence parameters) are more sensitive to seasonal variations. The results are a novelty in assessing the variation of CAM along the same plant in a height gradient and under field conditions.

Characterization of light intensity and quality, vegetative, flowering and fruiting traits in high and super-high density olive hedgerows

Orchard design (intra- and inter-row distance) defines the space allotted to each tree and the light environment for growth in olive hedgerows. Shading between neighboring trees affects the light intensity and quality, modifying the tree vegetative, flowering and fruiting characteristics. In this study, the incident photosynthetically active radiation (PAR) was simulated and the red-to-far-red ratio (R/FR) reflected by neighboring hedgerows down the canopy walls was measured. An analysis is presented of the response of olive vegetative, flowering, fruiting and productive traits to hedgerows of high (HD) and super-high density (SHD) orchards. The study was carried out during the 2018–2019 and 2019–2020 seasons in two 10-year-old olive cv. Genovesa orchards, one in HD (7 x 3.5 m) and the other in SHD (4 x 1.5 m). In both systems, continuous rows were used for measurements of light environment and vegetative, flowering and fruiting characteristics. The R/FR ratio and mean daily horizontal incident PAR were significantly higher in HD than in SHD. One-year-old shoots of HD hedgerows had shorter internodes in L position than U, M and L positions of SHD. Inflorescence number per shoot in the M and L positions of HD were triple than those of corresponding positions of SHD hedgerows. The mean yield per ha for both seasons was similar between HD and SHD hedgerows (average 9.3 and 9.4 t/ha, respectively). A greater planting density in olive hedgerows reduces the R/FR ratio reflected by neighboring trees while reducing incident PAR with increases in the hedgerow height. As a result, more illuminate HD hedgerows have greater specific leaf mass, higher leaf area density and higher axis-order angle compared to SHD hedgerows. This study seeks a new way to understand and measure the suitability of an olive cultivar trained in hedgerows at different planting densities.

Rescuing the Brazilian Agave breeding program: morphophysiological and molecular characterization of a new germplasm

Agaves have been a valuable resource in dryland areas for centuries, providing fibers (sisal), food, and beverages. However, the advent of synthetic fibers has led to a decrease in research on Agave, resulting in the cessation of breeding programs in Brazil. With the rise of climate change, there is renewed interest in Agave for its potential as a biofuel feedstock in semiarid regions. Since 2016, we have been collecting Agave accessions throughout the country and retrieving what is left of Brazil’s original breeding program to establish a new germplasm bank. Here, we evaluated 21 of those accessions growing in the field. We used molecular markers and morphophysiological traits to characterize the plants. Based on the Mayahuelin molecular marker, we were able to reconstruct a phylogeny for the Brazilian accessions. The morphophysiological traits explained 34.6% of the phenotypic variation in the dataset, with physiological traits such as leaf water content, effective quantum efficiency of photosystem II (ΦPSII), and specific leaf mass (SLM) as the most significant traits. Specifically, we evaluated nine Agave species and found that the physiological traits, rather than the morphological ones, were the most significant. Leaf water content was negatively correlated with specific leaf mass, which could be used as a marker for selecting cultivars with higher biomass accumulation. Interestingly, ΦPSII and chlorophyll content were negatively correlated, suggesting photochemical adaptations throughout the rosette. Molecular and phenotypic data suggest that A. amaniensis, which is frequently considered a synonym of A. sisalana, is effectively another species. Overall, this study provides valuable information on the physiological traits of Brazilian Agave accessions and is a starting point for selecting more productive and climate-resilient cultivars for biorenewables production.

Do Stimulate® and Ascophyllum nodosum seaweed promote the morphophysiological characteristics of Cordia alliodora seedlings?

Biostimulants in native forest seedlings, when absorbed and assimilated by plants, can function as activators or inhibitors of their metabolic and physiological processes. In view of the above, the present study establishes the following research problem: Can doses of Ascophyllum nodosum seaweed extract and Stimulate® be effective in the promotion of initial growth and morphophysiological indices of Cordia alliodora seedlings? The experimental design used was completely randomized, in a 4 x 2 factorial scheme, corresponding to four doses (0, 0.2, 0.4 and 0.6 ml L-1) and two hormones (Ascophyllum nodosum and Stimulate®), with five replicates, each of which composed of five seedlings (one in each container). The morphological variables evaluated were shoot height (H), stem diameter (SD), increments in stem diameter (ΔSD) and shoot height (ΔH), shoot dry mass (SDM, g plant-1), root dry mass (RDM, g plant-1), total dry mass (TDM, g plant-1), and Dickson Quality Index (DQI). Physiological variables were: net assimilation rate (EA, g.m-2.day-1), leaf relative growth rate (RA, g.m-2.day-1), leaf area ratio (FA, m2.g-1), specific leaf area (SA, cm2.g-1) and leaf mass ratio (Fw, g.g-1). The bioregulator Ascophyllum nodosum at dose of 0.2 ml L-1 promotes increments in height (ΔH) and stem diameter (ΔSD) of Cordia alliodora seedlings. Ascophyllum nodosum at dose of 0.2 ml L-1 has positive influence on the physiological indices studied in Cordia alliodora seedlings at 120 days after transplanting. The bioregulator Stimulate® at dose of 0.6 ml L-1 is not indicated to obtain Cordia alliodora seedlings with better quality and sturdiness and shorter nursery time. The bioregulator Ascophyllum nodosum at dose of 0.2 ml L-1 is recommended to obtain increments in height (ΔH) and stem diameter (ΔSD) in Cordia alliodora seedlings

Effect of seasonality on the leaf phenology and physiology of Byrsonima species (Malpighiaceae)

Introduction: Defined seasonality in savanna species can stimulate physiological responses that maximize photosynthetic metabolism and productivity. However, those physiological responses are also linked to the phenological status of the whole plant, including leaf phenophases. Objective: To study how physiological traits influence phenophase timing among congeneric and co-occurring savanna species. Methods: We evaluated the leaf phenology and physiological traits of populations of Byrsonima intermedia, B. coccolobifolia, and B. verbascifolia. Physiological measurements were performed at the onset of the dry and rainy seasons and again late in the season. Results: B. intermedia and B. coccolobifolia were classified as brevideciduous and B. verbascifolia as evergreen. The maximum quantum yield for B. intermedia and B. coccolobifolia were lowest during the dry season. At the onset of the dry period, the highest chloroplastidic pigment levels were observed, which decreased as the season advanced, total chlorophyll/carotenoid ratios were lowest, and carotenoid contents were highest. We detected low starch content values at the start of the rainy season, coinciding with the resumption of plant growth. Two months into this season, the leaves were at their peak structural and functional maturity, with high water-soluble polysaccharide values and photosynthetic rates, and were storing large amounts of starch. Conclusions: Physiological and leaf phenological strategies of the Byrsonima species were related to drought resistance and acclimatization to the seasonality of savanna water resources. The oscillations of the parameters quantified during the year indicated a strong relationship with water seasonality and with the phenological status of the leaves. Objective: We studied how physiological traits, and not only seasonality, influence phenophase timing among congeneric and co-occurring savanna species. Methods: We followed the leaf phenologies and physiological traits of populations of Byrsonima intermedia, B. coccolobifolia, and B. verbascifolia native to the Brazilian savanna. Analyses of specific leaf mass, relative water content, leaf phenology, leaf carbohydrate content, chloroplastidic pigments, and photosynthetic efficiency were performed at different times during both the dry and rainy seasons. Physiological measurements were performed at the onset of the dry season and again late in that season, as well as at the onset of the rainy season and again late in the rainy season. Results: Byrsonima intermedia and B. coccolobifolia were classified here as brevideciduous and B. verbascifolia as evergreen. Few variations in chlorophyll a fluorescence values were detected over the full year, with the lowest maximum quantum yield values (Fv/Fm) for B. intermedia and B. coccolobifolia occurring during the dry season. The deciduous species (B. verbascifolia) evidenced higher photosynthetic yields during periods of abundant water availability, mainly after its complete recovery after the start of the prolonged rainy period. The highest chloroplastidic pigment levels were observed at the onset of the dry period, although chlorophyll levels decreased as the dry season advanced. The lowest total chlorophyll/carotenoid ratios and the highest carotenoid contents observed at the onset of the dry season indicated that Byrsonima plants were still investing in mechanisms of photoprotection and the dissipation of excess energy from their photosynthetic systems even under water deficit conditions. We detected low starch content values at the onset of the rainy season, which coincides with the resumption of plant growth. At two months into the rainy season, the leaves were at their peak structural and functional maturity, exhibiting high water-soluble polysaccharide values and high photosynthetic rates, and were storing large amounts of starch. Conclusions: Our data evidenced that the physiological and foliar phenological strategies of the Byrsonima species studied here were related to drought resistance and to acclimatization to the seasonality of savanna water resources. The oscillations of the parameters quantified during the year in the three studied species indicated not only a strong relationship with water seasonality, but also with the phenological statuses of the leaves.

TiP-Leaf: a dataset of leaf traits across vegetation types on the Tibetan Plateau

Abstract. Functional trait databases are emerging as a crucial tool for a wide range of ecological studies, including next-generation vegetation modelling across the world. However, few large-scale studies have been reported on plant traits in the Tibetan Plateau (TP), the cradle of East Asian flora and fauna with specific alpine ecosystems, and no report on plant trait databases could be found. In this work, an extensive dataset of 11 leaf functional traits (TiP-Leaf), mainly for herbs and shrubs and a few trees on the TP, was compiled through field surveys. The TiP-Leaf dataset, which was compiled from 336 sites distributed mainly on the plateau surface and the northern margin of the TP across alpine and temperate vegetation regions and sampled from 2018 to 2021, contained 1692 morphological trait measurements of leaf thickness, leaf fresh weight, leaf dry weight, leaf dry-matter content, leaf water content, leaf area, specific leaf area and leaf mass per area and 1645 chemical element trait measurements of leaf carbon, nitrogen and phosphorus contents. Thus, 468 species that belong to 184 genera and 51 families were obtained and measured. In addition to leaf trait measurements, the geographic coordinates, bioclimate variables, disturbance intensities and vegetation types of each site were also recorded. The dataset could provide solid data support to effectively quantify the modern ecological features of alpine ecosystems, thereby further evaluating the response of alpine ecosystems to climate change and human disturbances and improving the next-generation vegetation model. The dataset, which is available from the National Tibetan Plateau Data Center (TPDC; Jin et al., 2022a; https://doi.org/10.11888/Terre.tpdc.272516), can make a great contribution to the regional and global plant trait databases.

Efeito do desbaste das árvores de eucalipto sobre rendimento da soja em sistemas de integração lavoura-pecuária-floresta

ABSTRACT: The aim of the study was to evaluate the effects of integrated crop-livestock-forestry (ICLF) systems and the thinning of eucalyptus trees on the agronomical performance of soybean. Treatments consisted of cultivation under: crops under full sunlight (CFS) conditions; ICLF with triple-row tree configuration (ICLFT) in which trees were submitted to selective thinning in the fifth year after planting through removal of 50% of trees while maintaining triple-row bands; and ICLF with single-row tree band configuration (ICLFS) in which the lateral rows of the triple-row tree bands were subjected to systematic thinning at the fourth year after planting. The physiological and agronomical variables of the soybean crop were evaluated at the R5 and R8 reproductive stages during the eighth harvesting season (2018/2019). Soybean sampling was carried out at five random positions in the CFS and in four transects at distances of 3, 6, 10 and 15 m from the tree bands in both the north and south faces of the ICLF systems. There were no differences between soybean grown under the ICLF and CFS systems with respect to specific leaf area, plant density, lodging index and mass of a thousand grains. However, the ICLF increased dry leaf mass and leaf area index and reduced soybean plant heights. Soybean productivity was reduced by 26% in ICLF-T and 14% in ICLF-S, that is, a 12% reduction in the productivity loss with systematic thinning. It is concluded that ICLF reduces soybean productivity in the effective grain production area of the system, regardless of the degree of thinning, although systematic thinning by removing the lateral tree lines to conversion of triple-rows into single-rows minimizes the loss of soybean grain yield.

Evergreen and deciduous tree species show distinct strategies to synchronize with seasonality in mid-elevational forests of central Himalaya

Synchronisation of the leaf phenological patterns with favourable environmental conditions and the variations in the leaf traits allow tree species to coexist, support biodiversity and maintain forest productivity with a larger implication on the global carbon cycle. However, within a forest whether plants with contrasting phenological attributes follow similar or distinct adaptive strategies for resource gain in response to seasonality and how they avoid niche-overlap to coexist is less clear. Further, whether the trade-offs between faster leaf growth within a shorter duration and vice-versa as proposed in the worldwide leaf economic spectrum (WLES) holds at the local scale remain inconclusive. Here, we aim to (1) describe patterns of temporal variation in leaf exposure (i.e. initiation, the peak of exposure, longevity, and expansion period) and leaf structural properties (i.e. area, dry mass, specific leaf area, dry-mass lost, construction cost, and mass acquired before the rainy season) among 12 coexisting evergreen and deciduous trees; and (2) explore whether the predictions of the WLES framework hold for evergreen and deciduous mid-elevation trees of the central Himalaya range. Results suggest that with an earlier leaf flush/leaf initiation and faster leaf recruitment in deciduous tree species, these plant species may maximize resource gains while investing less in structural parts of the leaves. In contrast, evergreens exhibit a higher investment in structural traits and retain leaves for a longer period and thereby maximizing resource gains from the growing season. The principal component analysis showed that PC-1 and PC-2 cumulatively explained 68.4% of the total variation in leaf traits. There was a distinct grouping of evergreen and deciduous species along the principal axis-1 for trait variation, suggesting a niche separation, which may allow species to coexist. When tested for the significance of differences in the average values of leaf traits, we found that deciduous trees had higher average values for mass before the rainy season (MRS), dry mass-loss (DML), specific leaf area (SLA), and leaf area (LA) than evergreens. The leaf life span of evergreens was significantly higher compared to the deciduous form which may allow evergreens to pay back the leaf construction cost which on average is higher than deciduous tree species. In a way, deciduous may adopt the resource acquisition strategy while evergreen exhibits a resource conservation strategy. The proposed generalized conservative-acquisitive traits axis of the world leaf economic spectrum thereby holds true for mid-elevational tree species in the central Himalaya.

The fern economics spectrum is unaffected by the environment.

The plant economics spectrum describes the trade-off between plant resource acquisition and storage, and sheds light on plant responses to environmental changes. However, the data used to construct the plant economics spectrum comes mainly from seed plants, thereby neglecting vascular non-seed plant lineages such as the ferns. To address this omission, we evaluated whether a fern economics spectrum exists using leaf and root traits of 23 fern species living under three subtropical forest conditions differing in light intensity and nutrient gradients. The fern leaf and root traits were found to be highly correlated and formed a plant economics spectrum. Specific leaf mass and root tissue density were found to be on one side of the spectrum (conservative strategy), whereas photosynthesis rate, specific root area, and specific root length were on the other side of the spectrum (acquisitive strategy). Ferns had higher photosynthesis and respiration rates, and photosynthetic nitrogen-use efficiency under high light conditions and higher specific root area and lower root tissue density in high nutrient environments. However, environmental changes did not significantly affect their resource acquisition strategies. Thus, the plant economics spectrum can be broadened to include ferns, which expands its phylogenetic and ecological implications and utility.

Multi-Year Monitoring of Deciduous Forests Ecophysiology and the Role of Temperature and Precipitation as Controlling Factors

Two deciduous forest ecosystems, one dominated by Fagus sylvatica and a mixed one with Quercus cerris and Quercus frainetto, were monitored from an ecophysiological perspective during a five-year period, in order to assess seasonal fluctuations, establish links between phenology and ecophysiology, and reveal climatic controls. Field measurements of leaf area index (LAI), chlorophyll content, leaf specific mass (LSM), water potential (Ψ) and leaf photosynthesis (Aleaf) were performed approximately on a monthly basis. LAI, chlorophylls and LSM fluctuations followed a recurrent pattern yearly, with increasing values during spring leaf burst and expansion, relatively stable values during summer and decreasing values during autumn senescence. However, pre-senescence leaf fall and chlorophyll reductions were evident in the driest year. The dynamically responsive Aleaf and Ψ presented considerable inter-annual variation. Both oak species showed more pronounced depressions of Aleaf and Ψ compared to beech, yet the time-point of their appearance coincided and was the same for all species each year. Spring temperature had a positive role in the increasing phase of all ecophysiological processes while rising autumn temperature resulted in retarded senescence. Precipitation showed asymmetric effects on the measured ecophysiological parameters. The between-species differences in responses, climate sensitivity and climate memory are identified and discussed.

The EICA is dead? Long live the EICA!

An important hypothesis for how plants respond to introduction to new ranges is the evolution of increased competitive ability (EICA). EICA predicts that biogeographical release from natural enemies initiates a trade-off in which exotic species in non-native ranges become larger and more competitive, but invest less in consumer defences, relative to populations in native ranges. This trade-off is exceptionally complex because detecting concomitant biogeographical shifts in competitive ability and consumer defence depends upon which traits are targeted, how competition is measured, the defence chemicals quantified, whether defence chemicals do more than defend, whether 'herbivory' is artificial or natural, and where consumers fall on the generalist-specialist spectrum. Previous meta-analyses have successfully identified patterns but have yet to fully disentangle this complexity. We used meta-analysis to reevaluate traditional metrics used to test EICA theory and then expanded on these metrics by partitioning competitive effect and competitive tolerance measures and testing Leaf-Specific Mass in detail as a response trait. Unlike previous syntheses, our meta-analyses detected evidence consistent with the classic trade-off inherent to EICA. Plants from non-native ranges imposed greater competitive effects than plants from native ranges and were less quantitatively defended than plants from native ranges. Our results for defence were not based on complex leaf chemistry, but instead were estimated from tannins, toughness traits and primarily Leaf-Specific Mass. Species specificity occurred but did not influence the general patterns. As for all evidence for EICA-like trade-offs, we do not know if the biogeographical differences we found were caused by trade-offs per se, but they are consistent with predictions derived from the overarching hypothesis. Underestimating physical leaf structure may have contributed to two decades of tepid perspectives on the trade-offs fundamental to EICA.

Plant traits affect vertical accretion of salt marshes

The current climate crisis is associated with rising sea levels, which raises the concerning prospect of losing coastal ecosystems, such as salt marshes. Where inland migration is impossible, salt marshes will only persist if their vertical accretion exceeds the rate of sea-level rise. Positive vertical accretion is mainly driven by sedimentation, whereas negative vertical accretion is driven by erosion and soil compaction, among others. These processes can be influenced by abiotic and biotic factors. The biotic factors, best described by plant functional traits of the salt-marsh vegetation, are, however, not well understood. We assembled a large dataset of 336 plots with vertical accretion time series and plant abundances and coupled it with trait data from salt marsh species of the German Wadden Sea, covering natural unmanaged, anthropogenic unmanaged, and grazed marshes. By using multiple logistic regression analyses, we studied the effects of plant functional traits and distance to the marsh edge on vertical accretion. Mean vertical accretion was in the range of recent sea level rise, except for plots on elevated grazed marshes. There were, however, pronounced local differences in vertical accretion. Positive accretion increased with distance to marsh edge and increasing leaf and stem roughness, described by specific stem length, canopy height, stem mass, leaf mass and leaf area. Except on grazed marshes, leaf traits contributed more strongly to the explanation of positive accretion than stem traits. Negative accretion by e.g., erosion was facilitated by low specific root length and low root and rhizome mass, i.e., lower anchoring capacity. To better assess coastal resilience to sea level rise, our findings suggest (i) to include these effect traits in models and experimental analyses of salt marsh vertical accretion and (ii) to consider effects of vegetation roughness on accretion in salt marsh management schemes.

Estimating Photosynthetic Attributes from High-Throughput Canopy Hyperspectral Sensing in Sorghum.

Sorghum, a genetically diverse C4 cereal, is an ideal model to study natural variation in photosynthetic capacity. Specific leaf nitrogen (SLN) and leaf mass per leaf area (LMA), as well as, maximal rates of Rubisco carboxylation (Vcmax), phosphoenolpyruvate (PEP) carboxylation (Vpmax), and electron transport (Jmax), quantified using a C4 photosynthesis model, were evaluated in two field-grown training sets (n = 169 plots including 124 genotypes) in 2019 and 2020. Partial least square regression (PLSR) was used to predict Vcmax (R2 = 0.83), Vpmax (R2 = 0.93), Jmax (R2 = 0.76), SLN (R2 = 0.82), and LMA (R2 = 0.68) from tractor-based hyperspectral sensing. Further assessments of the capability of the PLSR models for Vcmax, Vpmax, Jmax, SLN, and LMA were conducted by extrapolating these models to two trials of genome-wide association studies adjacent to the training sets in 2019 (n = 875 plots including 650 genotypes) and 2020 (n = 912 plots with 634 genotypes). The predicted traits showed medium to high heritability and genome-wide association studies using the predicted values identified four QTL for Vcmax and two QTL for Jmax. Candidate genes within 200 kb of the Vcmax QTL were involved in nitrogen storage, which is closely associated with Rubisco, while not directly associated with Rubisco activity per se. Jmax QTL was enriched for candidate genes involved in electron transport. These outcomes suggest the methods here are of great promise to effectively screen large germplasm collections for enhanced photosynthetic capacity.

Successional and Intraspecific Variations in Leaf Traits, Spectral Reflectance Indices and Herbivory in a Brazilian Tropical Dry Forest

Leaf traits are good indicators of ecosystem functioning and can affect herbivory and leaf reflectance patterns, allowing a better understanding of changes in environmental conditions, such those observed during forest natural regeneration. The aim of this study was to evaluate the intraspecific variation in leaf traits and their influence on the pattern of herbivory and leaf reflectance in three species distributed along a successional gradient (early, intermediate and late stages) in a tropical dry forest (TDF) in northern Minas Gerais, Brazil. We sampled individuals of the following abundant tree species that occurred in multiple successional stages: Cenostigma pluviosum, Handroanthus ochraceus, and Tabebuia reticulata. We collected 10 leaves from each tree to determine the contents of chlorophyll a, b, and total, carotenoids and water, as well as the percentage of leaf area removed by herbivores and leaf specific mass (LSM). We also measured five spectral reflectance indices (Normalized Difference Vegetation Index-NDVI, Simple Ratio-SR, modified Normalized Difference-nND, modified SR-mSR and Water Index-WI) using a portable spectrometer. Our results showed intraspecific differences in most leaf traits along the successional gradient, suggesting that local adaptation may play an important role in plant community assembly. However, herbivory only differed for H. ochraceus in early and intermediate stages, but it was not affected by the leaf traits considered here. Spectral reflectance indices also differed among successional stage for all species together and for each species separately, except for T. reticulata in intermediate and late stages. Thus, leaf spectral signatures may be an important tool to the remote detection of different successional stages in TDFs, with implications for forest management.

Inter‐ and intraspecific spatial distributions, spatial segregation by dominants and emergent neutrality in understorey plants

Tradeoffs between intra and interspecific distances of individual plants determine the spatial distributions of local plant communities and small‐scale community assembly. Here we use an individual based approach and null model standardization to compare intra‐ and interspecific nearest neighbour distances of plant ramets as well as mean differences in functional trait expression to nearest heterospecifics within local communities of temperate forest understorey plants in northern Poland. We found a general tendency towards clustered intraspecific and segregated interspecific ramet distributions. Spatial distribution patterns of understorey plants differed considerably between two nearby forest sites that mainly differed in the age structure of trees. Individuals of clonal species tended to have significantly smaller intraspecific and larger interspecific nearest neighbour distances than seed dispersing species. Our results indicate a major influence of dominant plant species on the spatial distributions of subdominants. Trait expressions related to plant growth (specific leaf area and leaf mass) and reproduction (seed mass) were significantly segregated in comparison to the spatial distribution of conspecific individuals and less so in comparison to heterospecific individuals. We argue that spatially explicit analyses of plant community assembly need to consider respective distributions of important traits and that the tradeoffs of contrasting trait distributions trigger small scale plant community composition and species distributions. We present a general framework for the analysis of plant community assembly based on the spatial distributions of individual plants and functional traits.

Hydrodynamics affect plant traits in estuarine ecotones with impact on carbon sequestration potentials

Estuaries are highly productive ecosystems that play an important role in carbon fixing. The amount of carbon fixed by temperate brackish marshes depends, among others, on the biomass produced, its decomposition and the organic carbon stored in the soil. Here, we assumed that the functional trait composition of the vegetation both responded to environmental drivers and affected production, decomposition rate of native biomass and soil organic carbon, in addition to direct links between environmental drivers and these ecosystem properties. We tested a set of detailed hypotheses with a partial least squares structural equation model and quantified wave height, inundation period, salinity, soil nutrients, species abundances and as traits the leaf area, specific leaf area, stem bending properties and investment per plant organ, as well as above-ground standing biomass, decomposition rates of native and control biomass (hay) and soil organic carbon (SOC).There was no direct relationship between environmental drivers and ecosystem properties, except with the decomposition of control hay. All other linkages involved the functional composition of the vegetation. Increasing inundation period simultaneously decreased plants traits like stem stiffness, leaf area, specific leaf area and mass fraction of stems and leaves, which were aggregated in a new trait ‘aboveground module’. Total plant biomass decreased in communities on higher elevations with reduced wave height. Here, increased investment in the aboveground trait module resulted in higher aboveground community biomass and SOC but decreased the decomposition of native plant material, which in turn was higher in the low lying vegetation zones. Increasing total plant biomass also increased SOC, but not aboveground community biomass. Both the aboveground trait module and total plant biomass were response and effect traits, by responding to the environmental drivers and affecting carbon related ecosystem properties.At lower elevation with higher inundation and higher wave height, SOC was lower than the product of standing biomass and decomposition rate, which could be a proxy of the expected SOC. This may indicate an export of dead plant material to higher elevations or further downstream.Due to sea level rise, the area of estuarine vegetation may decrease because a fixed dike line along the river prevents landward migration, which can reduce the amount of biomass produced and with it the potential to store SOC. Restoration of the tidal marshes or realignment of the dikes may be necessary to protect the ecosystem properties and services of estuarine vegetation.

Effect of applying a calcined kaolin-based particle film on the photosynthetic capacity and growth of young eucalyptus plants

In scenarios of climatic change when increased global temperatures can be expected, it is essential to search for technologies that favor sapling survival and growth after planting and increase yield in the field. Kaolin-based particle films (KBPF) have been applied as barriers against the deleterious effects of high levels of solar radiation. The objective of the present study was to assess the effects of applying purified calcined kaolin-based particle film to young eucalyptus plants. Five treatments were carried out: 0% (just water), 3%, 5%, 7%, and 10% calcined kaolin applied to the adaxial part of the leaves. A complete randomized block design was used with five treatments and ten replicates. The plants were assessed for height, diameter at ground level, gas exchanges (net photosynthetic CO2 assimilation, stomatal conductance and transpiration), instantaneous (WUE) and intrinsic water use efficiency (IWUE), chlorophyll a fluorescence (maximum quantum yield of photosystem II (PSII) (Fv/Fm), concentration of active reaction centers in relation to the quantity of photons absorbed (RC/ABS) and the maximum ratio of quantum yields of photochemical and concurrent non-photochemical processes in PSII (Fv/F0), SPAD reading and leaf ontogeny. The 3% KBPF concentration showed the best responses in biometric assessments 80 days after planting (DAP) and were corroborated by the responses of the leaf, stem and shoot dry matter production as a whole. The leaf ontogeny assessments showed positive responses following KBPF application when considering leaf development, with 7% KBPF concentration resulting in the highest mean values. The mean specific leaf mass had negative response to high KBPF concentrations. At 60 DAP, the gas exchange variables during both assessment periods declined with an increase in KBPF concentration. Significant differences as a result of KBPF applications were found only at the start of the assessments (34 DAP) for both WUE and for IWUE. Leaf ‘greenness’ (SPAD reading) at 47 days showed a quadratic relationship in both periods. The variables of chlorophyll fluorescence showed a linear response at 34 DAP and a quadratic response 60 DAP. KBPF application increased height and diameter growth in plants treated with 3% KBPF but this response was not associated with photochemical efficiency and photosynthetic carbon assimilation values on a single-leaf basis. The best performance among the variables was provided by 3% KBPF application.

Leaf silicification provides herbivore defence regardless of the extensive impacts of water stress

AbstractAltered precipitation patterns due to climate change are likely to impose water‐deficit stress in plants resulting in changes to specific leaf mass, leaf water content and chemical defences that may impact herbivorous arthropods. Grasses, in particular, accumulate large concentrations of silicon (Si) which provides physical defence against herbivores. Although Si uptake by plants may be affected by water availability, very few studies have investigated the combined effect of water‐deficit stress and Si on insect herbivore performance.We grew tall fescueFestuca arundinaceaSchreb. hydroponically, with and without Si, and half of the plants were treated with 20% polyethylene glycol (PEG) to impose osmotic stress. In all, 11 leaf traits (physiological, chemical and structural) were measured, silicified phytoliths on the leaf surface were visualised using scanning electron microscopy (SEM) in conjunction with X‐ray mapping, and plants were exposed to a chewing insect herbivore [Helicoverpa armigeraHübner (Lepidoptera: Noctuidae)].Although osmotic stress was associated with changes to leaf physiological and chemical traits, including increased specific leaf mass, decreased leaf relative water content and increased leaf nitrogen (N), there was no significant effect onH. armigerarelative growth rate (RGR). However, Si reduced RGR ofH. armigeraby 80%–98% while generating few changes to physiological and chemical leaf traits. Instead, the decline in RGR with Si was associated with changes to leaf structural traits, in particular, a greater density of silicified phytoliths on the leaf surface.Comparison of effect sizes indicated that leaf traits were primarily affected by osmotic stress but not Si, and that herbivore RGR was strongly negatively affected by Si but not osmotic stress. There was no interactive effect between the osmotic stress and Si treatments onH. armigeraRGR or plant traits except for leaf nitrogen and phenolic concentrations. This study provides further support that Si may prove to be beneficial to plants against chewing insect pests and remains robust regardless of water‐deficit stress conditions.A freePlain Language Summarycan be found within the Supporting Information of this article.

Soil resource availability, plant defense, and herbivory along a successional gradient in a tropical dry forest

Tropical dry forests (TDFs) usually occur as mosaics at different stages of natural regeneration, along which variations in soil attributes (fertility and texture) can affect plant growth and leaf traits and, consequently, leaf herbivory. In the present study, we used a chronosequence approach to determine the variations in plant growth, leaf defense, and insect herbivory in different successional species groups, following the predictions of the resource availability hypothesis: plants at early successional stages would grow faster, have lower specific leaf mass (SLM), and suffer higher herbivore damage than late successional plants. For this purpose, we measured plant diameter and collected leaves at the end of the rainy season (April) during three consecutive years in three different successional stages (early, intermediate, and late). In total, we sampled 38 plant species, from which 31 species were exclusive to a single successional stage (10 early, 13 intermediate, and eight late species). Our results did not conform to the resource availability hypothesis, as plants growing in early successional stages had higher growth rates and SLM, and lower leaf damage by herbivores. Soil fertility and texture did not affect plant growth or SLM, but leaf damage was negatively affected by SLM. Apart from being a defensive trait, SLM is also involved in the conservation of water and nutrients and photoprotection, and its variation along successional gradients in TDFs conforms to a continuum from conservative traits in hot and dry, early successional stages, to acquisitive traits in more humid late stages. Although other plant defenses must be considered, our three-year study indicates that the resource availability hypothesis, which was formulated for wet forests, should be adapted to deciduous TDFs where water availability is the main environmental filter along succession.

Morphological traits and yield in common bean

It is necessary to explore the relationship between yield-related traits to define the appropriate selection procedures to improve bean yield. The relationships between yield and its components have been extensively investigated by common bean breeding programs. However, less attention has been given to morphological and physiological traits. This study evaluates the effects of morphological traits of bean plants on their yield. Forty-one carioca genotypes were evaluated in a randomized block design with three replicates. The abscission of flowers, flower buds, and newly formed pods was monitored and specific leaf mass, leaflet area, average length and thick­ness of racemes and peduncles, 100-grain weight, number of pods per plant, and yield were determined. Yield responded negatively to increases in raceme and peduncle length and number of pods per plant and positively to increases in peduncle thickness and grain weight. Genotypes differed regarding yield and grain weight and were divided into two groups by the Scott-Knott’s test considering yield. The most productive group showed increased abscission of flowers and newly formed pods, decreased number of pods, and increased grain weight. The most productive genotypes were those that remobilized photoassimilates more easily for having shorter racemes and peduncles, thicker peduncles, and decreased expenditure of structural carbohydrates with malformed pods and other structures required for conditioning grains in the plant, compensating with greater grain weight.