Leaf Tissue Density Research Articles

Effect of simulated warming on leaf functional traits of urban greening plants

BackgroundResponse and adaptation strategies of plants to the environment have always been the core issues in ecological research. So far, relatively little study exists on its functional traits responses to warming, especially in an urban environment. This information is the key to help understand plant responses and trade-off strategy to urban warming.ResultsWe chose the common greening trees of mature age in Beijing (Fraxinus pennsylvanica, Koelreuteria paniculata, and Sophora japonica) as the research subjects, and used infrared heaters to simulate warming for three gradients of natural temperature (CK), moderate warming (T1) and severe warming (T2). Results showed that:(1) Leaf dry matter content (LDMC), chlorophyll content (CHL), leaf tissue density (LTD), and stomatal density (SD) all increased with temperature warming. Specific leaf area (SLA), stomatal size (SS), and stomatal aperture (SA) decreased with simulated warming. (2) SLA was extremely significantly negatively correlated with CHL, LDMC, LTD and SD (P < 0.01), and was extremely significantly positively correlated with SS (P < 0.01). SA was extremely negatively correlated with SD (P < 0.01), and was extremely significantly positively correlated with SS (P < 0.01). There was a significant positive correlation between LDMC and LTD (P < 0.01). This showed that urban greening trees adapted to the environment by coordinating adjustment among leaf functional traits. (3) Under the T1 treatment, the R2 and slope among the leaf traits were higher than CK, and the significance was also enhanced. The correlation between leaf traits was strengthened in this warming environment. Conversely, it will weaken the correlation between leaf traits under the T2 treatment.ConclusionOur study demonstrated that there was a strong trade-off between leaf functional traits in the urban warming environment. Plants in the warming environment have adopted relatively consistent trade-offs and adaptation strategies. Moderate warming was more conducive to strengthening their trade-off potential. It is further verified that the global leaf economics spectrum also exists in urban ecosystems, which is generally tend to a quick-investment return type with the characteristics of thick leaves, strong photosynthetic capacity, low transpiration efficiency and long life in urban environments.

Traits and their plasticity determine responses of plant performance and community functional property to nitrogen enrichment in a boreal peatland

Nitrogen (N) enrichment is well-known to cause declines in plant diversity, yet it remains a challenge to predict which species would be winners or losers. Here, we examined whether traits and their plasticity could predict plant performance under N enrichment, and how changes in plant performance and trait expression could affect community functional property. Relative cover, six leaf traits, and maximum plant height of eight common vascular plants were measured after six-year N addition (0, 3, 6, 12 g N m−2 year−1) in a boreal peatland in Northeast China. Plant performance responding to N enrichment and trait plasticity were separately calculated as changes in relative cover and trait values between control and N addition treatments. Moreover, we quantified relative contributions of species turnover and intraspecific trait variation to changes in functional property. Changes in plant performance were significantly related to plasticity in specific leaf area (SLA) and leaf N concentration (LN) under low N addition, but to maximum plant height under high N addition. When scaled up to the community level, intraspecific trait variation significantly contributed to changes in community-weighted mean leaf area, SLA, leaf tissue density, and LN, and functional diversity of all six leaf traits. These findings highlight the significance of trait plasticity in predicting responses of plant performance and community functional property to N enrichment, and suggest that trait-based approaches are useful in predicting ecological consequences of environmental changes in boreal peatlands.

Analysis of mesophyll conductance in five understory herbaceous species.

Mesophyll conductance (g m) has received over time much less attention than stomatal conductance (g s), although it affects leaf photosynthesis to about the same extent as stomatal conductance does. The objective of this study was to analyze the g m trend in five understory herbaceous species growing in a close-canopy forest in the north-west of Italy. In particular, three of analyzed species were monocots: Carex brizoides Lam., Carex pilosa Scop., and Oplismenus undulatifolius P. Beauv and the others dicots species: Circaea lutetiana L., and Pulmonaria officinalis Ced. The results showed, on one hand, the absence of correlation between g m and the considered environmental variables in the forest understory (i.e. air temperature, photosynthetic photon flux density and carbon dioxide concentration). Moreover, we carried out a principal component analysis considering all the analyzed morphological and physiological variables for the five species. The following correlation between the first component, related to the leaf mass per unit of leaf area and the leaf tissue density, and g m seem to suggest a key role of the leaf structural features in determining g m variations across the five species.

Phenotypic plasticity of Platanus acerifolia (Platanaceae): morphological and anatomical trait variations in response to different pollution levels in Rome

Platanus acerifolia (Aiton) Willd was generated spontaneously around the beginning of the 1600s in Spain between Platanus orientalis L. and Platanus occidentalis L. The study was carried out on P. acerifolia trees in different sites in Rome in the period April-July 2019. Trees comparable for size were selected in A sites (historical parks), B sites (high traffic density streets) and in C sites (high traffic density avenues along the Tevere River characterized by a large water availability). At the morphological level, leaf area (LA) was significantly higher in A and C sites and leaf tissue density (LTD) in C sites. At anatomical level, the total leaf thickness (LT), the palisade parenchyma thickness (Pt), the spongy parenchyma thickness (St) and the abaxial epidermis thickness (Abet) were significantly higher in A sites, while the adaxial cuticle thickness (Adct) and the adaxial epidermis thickness (Adet) in B sites. The ratio between palisade and spongy parenchyma thickness (P/S) was significantly higher in C sites. The plasticity index (PI, 0.42) was calculated on all the considered leaf traits. Among the morphological traits, LTD had the highest plasticity (0.49) and among the anatomical traits, trichomes density (TD) and Adet (0.74 and 0.54, respectively). Overall, the results highlight the large adaptability of P. acerifolia to grow in different sites in Rome through several changes in leaf morphological and anatomical traits.

Effects of fire intensity on leaf functional traits and functional diversity of Larix gmelinii community

Fire is an important ecological factor in boreal coniferous forest, which directly affects plant taxonomic and functional diversity and consequently forest succession. We analyzed the changes of soil nutrient contents, leaf functional traits, taxonomic and functional diversity of a Larix gmelinii community under different fire intensity levels (low, medium, heavy). The forest stand had been naturally recovered for 12 years in Yakeshi area. The results showed that fire significantly reduced soil total nitrogen content, but did not affect soil total phosphorus content. Low and medium fire intensities could maintain higher species diversity and functional diversity of the community. Medium fire disturbance significantly increased species diversity of the community, with maximum species richness index, Shannon index, Simpson index and Pielou evenness index. Fire disturbance reduced functional richness and functional divergence of the community, which were the largest in medium and low fire intensity respectively (except unburned). Functional evenness and Rao qua-dratic entropy index increased after forest fire disturbance, and the largest was in the low intensity burned area. With the increases of fire intensity, leaf dry matter content, leaf tissue density and leaf total phosphorus content showed a significantly increased trend, while specific leaf area, leaf water content, leaf total nitrogen content and leaf N:P showed the trend unburned ＞ medium fire ＞ low fire ＞ heavy fire, leaf thickness increased first and then decreased. Fire intensity had significant effects on leaf functional traits and functional diversity of forest community. Moderate fire distur-bance could promote forest restoration.

Invasive Alien Vines Affect Leaf Traits of Riparian Woody Vegetation

The vines Echinocystis lobata and Parthenocissus quinquefolia are spreading over the natural vegetation in riparian zones, which may significantly affect riparian vegetation properties and the quality of litter for aquatic organisms. We examined leaf morphological, biochemical and optical traits of these invasive alien species, each paired with its host, the willows Salix caprea and S. fragilis, respectively. The vines altered the host radiation environment and the amount of photosynthetic pigments. Both vines had significantly higher specific leaf area and lower leaf tissue density compared to the willows, even though the leaves of P. quinquefolia were significantly thicker. Leaf optical properties varied significantly between vines and willows in some spectral regions. Compared to the willows, the vines reflected less light as UV, and more as green, and transmitted more light as green, yellow and red. The overgrowth of the willows with vines affected the reflectance of the willow leaves. Redundancy analysis of the relationships between leaf biochemical traits and reflectance spectra showed that chlorophyll a, anthocyanins, and UVB- and UVA-absorbing substances explained 45% of the reflectance spectra variability, while analysis with morphological traits revealed that specific leaf area, leaf thickness and upper cuticle thickness explained 43%. For leaf transmittance, UVB- and UVA-absorbing substances, carotenoids and anthocyanins explained 53% of the transmittance spectra variability, while analysis with morphological traits revealed that specific leaf area explained 51%. These data show that invasive alien vines can be discerned from each other and their hosts by their spectral signatures. In addition, the differences in the leaf functional traits between the vines and their hosts indicate significant differences in the quality of the plant litter entering the river.

Physiological, morphological and anatomical leaf traits variation across leaf development in 'Corylus avellana'

The study analyzed the variations of physiological, morphological and anatomical leaf traits during its development in Corylus avellana L. saplings. Three different phases were identify during leaf development: the first phase (hereafter IP) considered in the developing leaves, the second phase (IIP) in the mature green leaves and the third phase (IIIP) in the senescent leaves. In particular, variations in parameters estimated from the photosynthetic light response curves, in chlorophyll fluorescence variables and in morphological leaf traits were analyzed during the three phases. The principal component analysis (PCA) carried out using all the considered morphological characters (leaf mass per area - LMA, and leaf tissue density - LTD) and physiological traits (the maximum net photosynthetic rates - ANmax, dark respiration rates - RD, light compensation point - LCP, light saturation point – LSP, maximum quantum yield - ɸmax, fluorescence-based maximum quantum yield of PSII photochemistry - Fv/FM and effective quantum yield of PSII photochemistry - ɸPSII) showed a complete separation among the considered phases. The results showed that the major differences occur between the phases IP and IIP. In particular, a greater variation was found for LMA, ANmax, RD. On the contrary a lower variation was observed for ɸmax which remain quite constant from IP to IIP indicating that chloroplasts present in juvenile leaves are fully functional.

Effect of rootstocks on morphological and physiological traits of Sultana grapevine under moisture stress conditions

The effects of two Iranian grape rootstocks namely Kaj Anguor Bojnord (KA) and Qare Gandomeh (QG) with scion Sultana were studied in 2015 for drought stress, leaf structural characteristics and gas exchange parameters. Greenhouse grown, grapevines of cv. Sultana (Vitis vinifera L.) grafted onto two rootstocks and on own roots, were subjected to three drought stress levels (NS: no-stress, MS: moderate stress and SS: severe stress). The results indicated that under SS, relative water content in KA-grafted was similar to that in un-grafted Sultana under MS. Moreover, leaf area decreased under SS compared MS. Furthermore, KA-grafted exhibited the highest value of leaf fresh mass. The leaf dry mass for un-grafted Sultana was significantly lower than grafted vines and, the values of leaf tissue density for the three rootstocks were lower than control. Under MS, the leaf thickness of Sultana on KA exhibited an increase, while the other rootstocks followed a decreasing trend under SS. Also un-grafted Sultana had a higher specific leaf area compared to grafted vines. The amounts of leaf chlorophyll in Sultana on KA and QG were significantly higher than un-grafted vines. KAgrafted improved photosynthesis rate of Sultana scion compared to the own-rooted plants in all experimental drought conditions. Additionally, the transpiration for Sultana scion leaves had declined compared to ungrafted plants. Significant interactions were observed between stress levels and rootstocks on the water use efficiency. Concluding, in his experiment KA rootstock could be better performance compared to QG and un-grafted Sultana to drought stress.

Covariation between leaf hydraulics and biomechanics is driven by leaf density in Mediterranean shrubs

Leaf density links the resistance to mechanical and hydraulic stress in Mediterranean shrubs as it is associated with the water potential at turgor loss and the moduli of elasticity and strength. Understanding the patterns of hydraulic and mechanical trait variation in vascular plants is critical to predicting species’ stress tolerance. Although previous work has shown that hydraulic and mechanical traits are decoupled in stems, there is little information available for leaves, which are organs more diversified in structure, function, and possibly drought tolerance strategies across habitats. We tested for coordination between leaf hydraulic traits related to drought tolerance and the mechanical resistance of leaves, for 17 shrub species from the arid and semiarid vegetation of the California Floristic Province. Bayesian and phylogenetic correlations showed that across species, hydraulic and mechanical traits both had strong associations with the water potential at turgor loss, and with leaf tissue density. However, leaf maximum hydraulic conductance and the water potential at 50% and 80% loss of hydraulic conductance were statistically independent of two key mechanical traits, the leaf modulus of elasticity and leaf structural strength. Our results suggest that leaf biomechanical traits, which reflect construction costs and contribute to leaf longevity, are decoupled from hydraulic capacity and safety. The independence of hydraulic and mechanical protection in leaves enables a wide range of trait combinations in leaves, which would increase their adaptive potential across ecosystems.

Contrasting leaf-trait strategies in dominant liana and tree species of Indian tropical dry evergreen forest

Recent studies have revealed convergence in the variation of leaf traits across various plant life-forms on a global scale. This study aims to analyze and compare the leaf-trait strategies of dominant liana and tree species in Indian tropical dry evergreen forest (TDEF). The study also checks whether these life-forms differ in their resource acquisition strategies explained by the variance in their leaf functional traits. The present study was carried out in a permanent plot established in a TDEF site on the Coromandel Coast of India. We selected ten dominant species of lianas and trees to analyze and compare their leaf-trait strategies. For each species, we collected 30 healthy sun leaves from at least eight individuals. The collected leaf samples were analyzed for various leaf functional traits using standard protocol. Lianas had higher specific leaf area and mass-based leaf nitrogen than the trees. Trees had higher leaf lamina area, leaf thickness, leaf mass per area, leaf tissue density and C:N than the lianas. Lianas and trees in the studied site differed significantly in six out of seven leaf-functional traits analyzed. The observed leaf trait strategies of lianas in TDEF could offer competitive advantage for them over trees.

Inherent variation of functional traits in winter and summer leaves of Mediterranean seasonal dimorphic species: evidence of a 'within leaf cohort' spectrum.

The covariation pattern among leaf functional traits involved in resource acquisition has been successfully provided by the leaf economic spectrum (LES). Nevertheless, some aspects such as how the leaf trait variation sources affect LES predictions are still little investigated. Accordingly, the aim of this paper was to test whether leaf trait variations within different leaf cohorts could alter LES. Improving this knowledge can extend the potential of trait-based approaches in simulating future climate effects on ecosystems. A database on leaf morphological and physiological traits from different leaf cohorts of Cistus spp. was built by collecting data from literature. These species are seasonal dimorphic shrubs with two well-defined leaf cohorts during a year: summer leaves (SL) and winter leaves (WL). Traits included: leaf mass area (LMA), leaf thickness (LT), leaf tissue density (LTD), net photosynthetic rate on area (Aa) and mass (Am) base, nitrogen content on area (Na) and mass (Nm) base. The obtained patterns were analysed by standardized major axis regression and then compared with the global spectrum of evergreens and deciduous species. Climatic variable effect on leaf traits was also tested. Winter leaves and SL showed a great inherent variability for all the considered traits. Nevertheless, some relationships differed in terms of slopes or intercepts between SL and WL and between leaf cohorts and the global spectrum of evergreens and deciduous. Moreover, climatic variables differently affected leaf traits in SL and WL. The results show the existence of a ‘within leaf cohort’ spectrum, providing the first evidence on the role of leaf cohorts as LES source of variation. In fact, WL showed a high return strategy as they tended to maximize, in a short time, resource acquisition with a lower dry mass investment, while SL were characterized by a low return strategy.

Leaf Trait Variation with Environmental Factors at Different Spatial Scales: A Multilevel Analysis Across a Forest-Steppe Transition

In mountain areas, the distribution of plant communities is affected by both regional and microhabitat conditions. The degree to which these different spatial factors contribute to plant communities is not well understood, because few studies have used a uniform sampling methodology to measure trait variation across the range of ecological scales. In this study, a stratified sampling method was used to study community weighted leaf traits and environment factors at different spatial (transect and plot) scales. We measured 6 leaf traits (specific leaf area, leaf tissue density, leaf thickness, leaf carbon, nitrogen and phosphorus content) in 258 communities from 57 sites in 9 transects nested within 3 vegetation zones. These communities are located in the loess hilly and gully area of the Yanhe river watershed. We coupled climatic factors at the transect scale with topographic and edaphic factors at the plot scale using multilevel regression modeling to analyze the trait variation associated with spatial scales. At the transect scale, the mean annual rainfall showed a highly significant positive effect on the leaf nitrogen concentration (LNC) (p &lt; 0.01), while it had a highly significant negative effect on leaf thickness (LT) and leaf tissue density (LTD) (p &lt; 0.001) and a significant negative effect on leaf carbon concentration (LCC) (p &lt; 0.05), explaining 10.91%, 36.08%, 57.25% and 66.01% of LTD, LT, LCC and LNC variation at transect scale respectively. At a plot scale, the slope aspect showed a highly significant positive effect on specific leaf area (SLA) and LNC but a highly significant negative effect on LT and LTD. The soil water content had a significant negative effect on LT (p &lt; 0.05) and LTD (p &lt; 0.001) while soil organic matter showed a positive effect on SLA (p &lt; 0.001) and LNC (p &lt; 0.01). Totally, plot scale variables explained 7.28%, 43.60%, 46.43%, 75.39% and 81.17% of LCC, LT, LNC, LTD and SLA variation. The elevation showed positive effect only on LCC (p &lt; 0.05). The results confirmed the existence of consistent trait–environment relationships at both transect and plot scales. These trait–environment relationships at different spatial scales will provide mechanistic understanding on the vegetation community assembly in the study area. Practically, ignoring trait variation within transects will underestimate roles of microhabitat filters in community assembly, and leads to the homogenization of restoration species. This will be like the past restoration plans and programs, causing serious environmental problems such as dwarf trees and soil desiccation.

Relationships between leaf functional traits of Machilus pauhoi understory seedlings from different provenances and geographical environmental factors.

To understand the adaptation mechanism of Machilus pauhoi seedlings to environmental changes, leaf functional traits of M. pauhoi seedlings from nine provenances, as well as relationships between leaf traits and environmental factors were analyzed. The results showed that leaf functional traits of M. pauhoi seedlings from different provenances showed significant intraspecific variations, with the coefficient of variation ranging from 8.8% to 28.2%. Specific leaf area, leaf relative water content, leaf tissue density and leaf thickness differed significantly among seedlings from different provenances, implying high leaf morphological plasticity. Moreover, leaf tissue density was positively correlated to leaf dry matter content and leaf relative water content, but negatively correlated to specific leaf area and leaf thickness. Specific leaf area showed significantly negative correlations with leaf dry matter content and leaf area. The covariation among those traits examined here indicated that M. pauhoi seedlings could adjust and balance the combination of leaf traits in response to environmental changes. Longitude, latitude, >10 ℃ annual accumulated temperature and mean annual temperature contributed largely to the variation of leaf functional traits of M. pauhoi seedlings. Leaf thickness decreased with the increase of longitude, while leaf dry matter content and leaf relative water content increased with the increase of longitude. Leaf tissue density was positively correlated with longitude and mean annual temperature, suggesting that longitude rather than mean annual temperature had greater effects on it. Leaf area was positively correlated with >10 ℃ annual accumulated temperature and longitude, indicating that annual accumulated temperature rather than longitude had greater effects on the variation of leaf area.

Effects of alien species Robinia pseudoacacia on plant community functional structure in hilly-gully region of Loess Plateau, China.

To investigate the effects of the introduction of Robinia pseudoacacia on the functional structure of plant communities, we selected paired-plots of R. pseudoacacia communities and native plant communities across different vegetation zones, i.e., steppe zone, forest-steppe zone, forest zone in hilly-gully region of Loess Plateau, China. We measured several functional characteristics and then compared the functional structures of R. pseudoacacia and native plant communities in different vegetation zones. The results showed that the variation of the functional traits across different vegetation zones were consistent in R. pseudoacacia community and native plant community, including leaf carbon concentration, leaf nitrogen concentration, leaf phosphorus concentration, specific leaf area, and leaf tissue density. The leaf carbon concentration, leaf nitrogen concentration, and specific leaf area of the R. pseudoacacia community were significantly higher than those of the native plant community. The trend of change that the functional diversity indices, i.e., FRic, FEve, FDiv, FDis, Rao of the R. pseudoacacia community and the native plant community with vegetation zones were different. The introduction of R. pseudoacacia enhanced the plant community functional diversity in the forest zone but reduced community functional diversity in the steppe zone.

Differential Response to Salt Stress Within and Among Iranian Melilotus Species

ABSTRACTThis paper explores the salt-tolerance response of Melilotus species, a forage legume, based on tolerance/susceptibility indices, leaf water relations, leaf/root ion concentrations and multivariate (factor and function discriminate) analyses. In a greenhouse experiment, salinity-susceptibility of 12 accessions of Melilotus (M. albus, M. indicus, M. officinalis) in addition, two controls (alfalfa and Persian clover) were evaluated at 0 mM, 100 mM, 200 mM, and 300 mM of sodium chloride (NaCl). The experiment was conducted in a split plot design with two replications. Stress tolerance score (STS) was calculated based on tolerance/susceptibility indices. Salt-tolerant accessions were identified. An extracted bi-plot based on factor analysis confirmed the results of tolerance/susceptibility indices. There were significant correlations between STS and multivariate statistics. Root potassium cation (K+) concentration was higher in Melilotus species than the control species in all the salinity treatments. STS, root K+ concentration, leaf turgidity, and leaf succulence characteristics can be used for screening salinity-tolerance in Melilotus accessions. In all treatments, M. officinalis, M. indicus, and M. albus were salinity-tolerant species in descending order.Abbreviations: Total biomass yield under control (Yp) and stress (Ys) mediums, geometric mean productivity (GMP), leaf area (LA), leaf tissue density (LTD), linear regression coefficient (b), mean productivity (MP), relative water content (RWC%), Succulence (S), specific leaf area (SLA), stress susceptibility index (SSI), stress tolerance index (STI), tolerance (TOL), water content at saturation (WCS), water saturation deficit (WSD), sodium chloride (NaCl), potassium cation (K+), sodium cation (Na+), analysis of variance (ANOVA), least significant difference (LSD), alfalfa control accession (CHA), Persian clover control accession (CHC), coefficient of variation (CV), statistics of factor (F) and discriminate function (D)

Variable Response of Leaf Temperature, Tissue Density and Greenness of 'Michele Palieri (Vitis vinifera L.) to Water Stress Under Different Rootstock Effects

Most vineyards around the world are established in regions with seasonal drought where soil and atmospheric water deficits, together with high temperatures, exert large constraints on grapevines. The increasing demand for vineyard irrigation requires an improvement in the efficiency of water use, such as deficit irrigation to allow plants withstand mild water stress. The present study was performed to understand certain leaf physiological bases of grapevine responses to mild water deficits under various rootstock effects. Two irrigation levels (field capacity and 50% of field capacity) were applied to two years old vines of Michele Palieri table grape cultivar, using 5 different rootstock, including own rooted vines. Investigations revealed that rootstocks have remarkable effects on leaf greenness (estimation of leaf chlorophyll content by SPAD meter readings) and slight effects on leaf temperature. Leaf tissue density was also changed according to the rootstock use. Overall, deficit irrigation at 50% of field capacity may be a potential deficit irrigation program for grapevines when accurately optimized according to specific requirements of different grapevine genotypes.

Leaf thickness and density drive the responsiveness of photosynthesis to air temperature in Mediterranean species according to their leaf habitus

The responsiveness of net photosynthetic rate (Aa) to mean monthly air temperature (TM) of eight Mediterranean evergreen species was investigated by analyzing the inter-annual changes in leaf mass area (LMA), leaf tissue density (LTD) and leaf thickness (LT). We wanted to test if species leaf habitus affected this response. To hit the goal, a multi-year dataset from our previously published papers was used. The inter-annual variability in LMA, LTD and LT was assessed by their coefficients of variation (CVs). Aa sensitivity to TM (SAa) was quantified by the slope of the species-specific relationships Aa-TM. A Principal Component Analysis (PC) was carried to identify the leaf morphological variation patterns across species. SAa was affected by the coordination of LTD and LT across species and this coordination depended on leaf habitus. The relationship between CVs and SAa revealed that only evergreen sclerophyllous with a longer leaf life-span rely on the inter-annual changes in LTD and LT to modulate their SAa. Overall, the results showed that the inter-annual LTD and LT variability affected the responsiveness of net photosynthetic rate of the selected species according to their leaf habitus.

The relationships between leaf economics and hydraulic traits of woody plants depend on water availability

Leaf economics and hydraulic traits are simultaneously involved in the process of trading water for CO2, but the relationships between these two suites of traits remain ambiguous. Recently, Li et al. (2015) reported that leaf economics and hydraulic traits were decoupled in five tropical-subtropical forests in China.We tested the hypothesis that the relationships between economics and hydraulic traits may depend on water availability. We analysed five leaf economics traits, four hydraulic traits and anatomical structures of 47 woody species on the Loess Plateau with poor water availability and compared those data with Li et al. (2015) obtained in tropical-subtropical regions with adequate water.The results showed that plants on the Loess Plateau tend to have higher leaf tissue density (TD), leaf nitrogen concentrations and venation density (VD) and lower stomatal guard cell length (SL) and maximum stomatal conductance to water vapour (gwmax). VD showed positive correlations with leaf nitrogen concentrations, palisade tissue thickness (PT) and ratio of palisade tissue thickness to spongy tissue thickness (PT/ST). Principal component analysis (PCA) showed a result opposite from those of tropical-subtropical regions: leaf economics and hydraulic traits were coupled on the Loess Plateau.A stable correlation between these two suites of traits may be more cost-effective on the Loess Plateau, where water availability is poor. The correlation of leaf economics and hydraulic traits may be a type of adaptation mechanism in arid conditions.

Succession of plant community composition and leaf functional traits in responding to karst rocky desertification in the Wushan County in Chongqing, China

Karst rocky desertification (KRD) is a process of soil desertification, which leads to the decline of soil quality and biomass. We conducted a plant community survey in KRD areas in Chongqing, China. Our aims were to determine key soil properties that shape plant communities and to identify essential leaf functional traits (LFTs) in responding to the progression of KRD. The vegetation survey was carried in a total of twenty study sites (five replicates for four stages of KRD) in the Wushan County in Chongqing, China. Leaves were collected from all the species in every site and measured/calculated for five LFTs, namely, specific leaf area, leaf area, leaf thickness, leaf tissue density, and leaf dry matter content. Soil samples were collected in triplicates in each site to measure soil properties. We found that the overall richness and diversity of community decreased along with the progression of KRD. Phanerophytes predominated in all the KRD areas. Soil pH was the main determinant of vegetation structure. Leaves with lower area yet higher density had the optimal adaptability in KRD regions, which can be planted as pioneer vegetation to restore land in KRD regions.

Comparative leaf growth strategies in response to low-water and low-light availability: variation in leaf physiology underlies variation in leaf mass per area in Populus tremuloides.

Developmental phenotypic plasticity can allow plants to buffer the effects of abiotic and biotic environmental stressors. Therefore, it is vital to improve our understanding of how phenotypic plasticity in ecological functional traits is coordinated with variation in physiological performance in plants. To identify coordinated leaf responses to low-water (LW) versus low-light (LL) availability, we measured leaf mass per area (LMA), leaf anatomical characteristics and leaf gas exchange of juvenile Populus tremuloidesMichx. trees. Spongy mesophyll tissue surface area (Asmes/A) was correlated with intrinsic water-use efficiency (WUEi: photosynthesis, (Aarea)/stomatal conductance (gs)). Under LW availability, these changes occurred at the cost of greater leaf tissue density and reduced expansive growth, as leaves were denser but were only 20% the final area of control leaves, resulting in elevated LMA and elevated WUEi. Low light resulted in reduced palisade mesophyll surface area (Apmes/A) while spongy mesophyll surface area was maintained (Asmes/A), with no changes to WUEi. These leaf morphological changes may be a plastic strategy to increase laminar light capture while maintaining WUEi. With reduced density and thickness, however, leaves were 50% the area of control leaves, ultimately resulting in reduced LMA. Our results illustrate that P. tremuloides saplings partially maintain physiological function in response to water and light limitation by inducing developmental plasticity in LMA with underlying anatomical changes. We discuss additional implications of these results in the context of developmental plasticity, growth trade-offs and the ecological impacts of climate change.