Differences In Specific Leaf Area Research Articles

Gas exchange and phenotypic plasticity in three tree species in preserved and anthropized areas in a Tropical Dry Forest

Caatinga, the Brazilian tropical dry forest and source of endemic species, suffers anthropic disturbances that are responsible for affecting plants and their functional traits. Therefore, we aimed to evaluate the plasticity woody species’ leaf traits due to abiotic conditions of preserved and anthropized areas in Caatinga. The study took place in Vale do Riacho São José, in the municipality of Caetés, Pernambuco, Brazil. The selected species were Mimosa tenuiflora, Mimosa arenosa and Senna sp., all belonging to the Fabaceae family. We measured gas exchange, water content, specific leaf area and phenotypic plasticity index of all selected species in both areas. For all species, stomatal conductance was higher in preserved areas, but photosynthesis followed this pattern only for Senna sp. which also showed lower water use efficiency among all species. Furthermore, Senna sp. presented the highest relative water content in preserved areas, and showed no differences in specific leaf area between preserved and anthropized areas. The plasticity index showed that Senna sp. were the most plastic species, mainly adjusting water content and gas exchange parameters according to the area. The less plastic species was Mimosa arenosa. A principal component analysis showed a group formation due to anthropization, for all species. However, Senna sp. showed the largest distance among species. We conclude that all analyzed species respond to environmental conditions of preserved and anthropized areas, but this pattern cannot be related to the characteristics of the botanical family due to species-specific leaf traits’ variations.

Intra‐ and interspecific variability of specific leaf area mitigate the reduction of community stability in response to warming and nitrogen addition

Global environmental changes are reducing the diversity and affecting the functioning of natural ecosystems as well as their ability to reliably provide ecosystem functions and services to mankind. Many studies have shown that a greater plant diversity can stabilize community productivity against environmental fluctuations. However, most of these studies focused on plant species richness, thus overlooking the potential role of functional traits in stabilizing community productivity against environmental fluctuations. Whether and how functional trait mean and variability influence community stability in response to environmental changes and their relative contributions to community stability are largely unknown. Here, we used a 10‐year experiment to investigate the role of species richness, as well as functional mean and intra‐ and interspecific variability of specific leaf area (SLA) of plants within‐ and among communities in driving community stability in response to nitrogen (N) addition and warming. We found that both N addition and warming reduced the temporal stability of community productivity by reducing species richness and its contribution to species asynchrony and species stability. In contrast, changes in the mean and variability of SLA in response to N addition and warming mitigated the reduction of community stability. Specifically, N addition reduced variation in SLA both by reducing interspecific differences in SLA within communities and differences in mean values of SLA among communities. Warming increased intraspecific differences in SLA among communities, leading to higher species stability that partly buffered the reduction of community stability. Our study demonstrates the role of trait mean and variability in mitigating the reduction of community stability in response to two pervasive global environmental changes. Gaining a deeper understanding of the processes linking global changes and the stability of our ecosystems requires integrating both trait mean values and trait variability.

PM2.5 reduction capacities and their relation to morphological and physiological traits in 13 landscaping tree species

Fine particulate matter (PM2.5) is emerging as a serious environmental problem worldwide with the increase in anthropogenic emission sources, such as fossil fuels, transportation, and industries. In urban areas, where industrial complexes and human activities are concentrated, PM2.5 poses a threat to human health. Recently, because of their ability to reduce PM2.5, the introduction of landscaping trees as an environment-friendly solution has become popular; however, there remains a lack of research on the selection of species and their management. In this study, we quantified and compared the PM2.5 reduction capacities of 13 major landscaping tree species and analyzed their relationship with the morphological and physiological characteristics of each species. The results showed that the amount of PM2.5 reduction per leaf area differed among species and was the highest in Ginkgo biloba (28 165 ± 5353 # cm−2 min−1) and the lowest in Pinus strobus (1602 ± 186 # cm−2 min−1). Moreover, PM2.5 reduction by the broadleaf species (18 802 ± 1638 # cm−2 min−1) was approximately 8.6-fold higher than that of the needleleaf species (2194 ± 307 # cm−2 min−1). Correlation analysis revealed that differences in PM2.5 reduction were explained by differences in specific leaf area between species (P = 0.004) and by the length of margin per leaf area among individual trees (P < 0.05). Additionally, reduction in PM2.5 correlated with photosynthetic properties such as maximum assimilation and carboxylation rates (P < 0.001), indicating that PM2.5 is reduced not only by physical adsorption but also by physiological processes. These findings emphasize that for effective reduction in PM2.5 using landscaping trees, comprehensive consideration of the morphological and physiological characteristics of the species is essential during species selection, and that continuous management is also necessary to maintain the active physiological conditions of the trees.

Quantifying morpho-physiological traits that describe canopy and biomass formation and partitioning processes for spring wheat genotypes grown under contrasting nitrogen supply

ABSTRACT Radiation interception, radiation use efficiency (RUE) and harvest index (HI) are the key determinants of grain yield in cereal species. However, little is known about how these traits affect grain yield among spring wheat genotypes grown under low and optimum nitrogen (N) fertiliser supply. We used two experiments, in a field (Experiment 1; 2017–2018) and glasshouse (Experiment 2; 2018–2019) to investigate the effects of these traits on grain yield. Grain yield increased by 35% with increasing N fertiliser supply to 8.80 t/ha in Experiment 1 and 151% to 8.33 t/ha in Experiment 2. Grain yield was lowest for ‘Reliance’ and highest for ‘Discovery’ in both experiments. Differences in grain yield were not associated with HI. As the RUE did not differ among genotypes, the yield differences were attributed to the different amounts of radiation intercepted; a result of the faster leaf area expansion rate (LAER) and subsequent higher maximum green leaf area index (GLAI), and a longer leaf area duration (LAD). The differences in LAER and maximum GLAI among the genotypes were associated with a differences in specific leaf area (cm2/g). Our results suggest that improved grain yields in spring wheat can be achieved by focusing breeding efforts on canopy characteristics to increase radiation interception.

Patterns and drivers of community specific leaf area in China

Specific leaf area (SLA), an important functional trait, reflects the abilities of light capture and adaption to environments of plants. Earlier spatiotemporal changes in SLA at the species level have been widely studied. However, changes at the community level, especially those associated with species abundance and coverage, remain poorly being understood. Using the community data of SLA, which based on field measured and literature, for 2104 plots from 212 forests and grasslands in China between 2007 and 2019, we found that (1) Both CWM SLA (Community-weighted mean SLA) and CNM SLA (Community-not weighted mean SLA) in western China was significantly lower than those in eastern China; (2) Spatial patterns of CWM SLA in different landscapes were significantly different CNM SLA; (3) Both CWM and CNM SLAs of herbaceous plants was significantly higher than those of trees in natural and planted forests, and CNM SLA of trees in planted forests is significantly higher than that in natural forests; (4) Both CWM and CNM SLA of trees in natural and planted forest significantly increase with forest age aging. Our results provided the evidence that climate and stand-driven changes strengthen differences in SLA among the species from different communities, which have important insights into species competition and coexistence in forest ecosystems.

The genetic architecture of leaf stable carbon isotope composition in Zea mays and the effect of transpiration efficiency on leaf elemental accumulation.

With increased demand on freshwater resources for agriculture, it is imperative that more water-use efficient crops are developed. Leaf stable carbon isotope composition, δ13C, is a proxy for transpiration efficiency and a possible tool for breeders, but the underlying mechanisms effecting δ13C in C4 plants are not known. It has been suggested that differences in specific leaf area (SLA), which potentially reflects variation in internal CO2 diffusion, can impact leaf δ13C. Furthermore, although it is known that water movement is important for elemental uptake, it is not clear how manipulation of transpiration for increased water-use efficiency may impact nutrient accumulation. Here, we characterize the genetic architecture of leaf δ13C and test its relationship to SLA and the ionome in five populations of maize. Five significant QTL for leaf δ13C were identified, including novel QTL as well as some that were identified previously in maize kernels. One of the QTL regions contains an Erecta-like gene, the ortholog of which has been shown to regulate transpiration efficiency and leaf δ13C in Arabidopsis. QTL for δ13C were located in the same general chromosome region, but slightly shifted, when comparing data from two different years. Our data does not support a relationship between δ13C and SLA, and of the 19 elements analyzed, only a weak correlation between molybdenum and δ13C was detected. Together these data add to the genetic understanding of leaf δ13C in maize and suggest that improvements to plant water use may be possible without significantly influencing elemental homeostasis.

Leaf Nutrient Relations of Cycads in a Common Garden

Background and Aims Research required to clarify leaf nutrient relations of cycad species has been inadequate. Common garden studies are useful for determining the influence of genetics on leaf traits because of the homogeneous environment among experimental units. To date, there have been no common garden studies which included all ten genera of cycads. The full phylogenetic breadth has, therefore, not been included in this important area of study. Methods We examined macronutrient and micronutrient content of leaves from one representative species from each of the ten cycad genera at Nong Nooch Tropical Botanical Garden in Thailand. Nitrogen content was determined by dry combustion, and the remaining nutrients were quantified by spectrometry. Results The least variable elements were nitrogen and phosphorus, and the most variable elements were boron and sodium. Nutrient content based on leaflet area was more variable than based on leaflet mass, reflecting species differences in specific leaf area. There were no universal macronutrient or micronutrient signals indicating clear phylogenetic distinctions. Implications for Conservation: Active management of threatened cycad taxa requires research to develop the knowledge to enable evidence-based decisions. This common garden study inclusive of all 10 cycad genera creates a foundation to determine leaf nutrient sufficiency ranges to inform management decisions.

Increased Precipitation Shapes Relationship between Biochemical and Functional Traits of Stipa glareosa in Grass-Dominated Rather than Shrub-Dominated Community in a Desert Steppe.

Understanding the effects of precipitation variations on plant biochemical and functional traits is crucial to predict plant adaptation to future climate changes. The dominant species, Stipa glareosa, plays an important role in maintaining the structure and function of plant communities in the desert steppe, Inner Mongolia. However, little is known about how altered precipitation affects biochemical and functional traits of S. glareosa in different communities in the desert steppe. Here, we examined the responses of biochemical and functional traits of S. glareosa in shrub- and grass-dominated communities to experimentally increased precipitation (control, +20%, +40%, and +60%). We found that +40% and +60% increased plant height and leaf dry matter content (LDMC) and decreased specific leaf area (SLA) of S. glareosa in grass community. For biochemical traits in grass community, +60% decreased the contents of protein and chlorophyll b (Cb), while +40% increased the relative electrical conductivity and superoxide dismutase. Additionally, +20% increased LDMC and malondialaenyde, and decreased SLA and protein in shrub community. Chlorophyll a, Cb, carotenoids, protein and superoxide dismutase in the grass community differed with shrub community, while +60% caused differences in SLA, LDMC, leaf carbon content, malondialaenyde and peroxidase between two communities. The positive or negative linear patterns were observed between different functional and biochemical traits in grass- rather than shrub-community. Soil water content explained changes in some biochemical traits in the grass community, but not for functional traits. These results suggest that increased precipitation can affect functional traits of S. glareosa in the grass community by altering biochemical traits caused by soil water content. The biochemical and functional traits of S. glareosa were more sensitive to extreme precipitation in grass- than shrub-community in the desert steppe. Our study highlights the important differences in adaptive strategies of S. glareosa in different plant communities at the same site to precipitation changes.

Environmental explanation of maize specific leaf area under varying water stress regimes

Specific leaf area (SLA) is an essential functional trait and indicator for estimating plant strategies in response to environmental changes. Intraspecific and interspecific variations of SLA have been extensively studied, whereas the combined effects of soil water content and heat conditions on SLA dynamics have received little attention. Field experiments with different irrigation regimes for maize (Zea mays L.) were designed and conducted across two growing seasons during 2013–2014 in north China, which usually have onset of severe drought conditions. Our results showed that maize plant SLA decreased with effective accumulated temperature under both rain-fed and drought conditions. Different intensities of water stress beginning at the three-leaf stage (2014) and the seven-leaf stage (2013) resulted in significant decreases of leaf area and leaf dry mass, however, with no significant differences in SLA. It is the occurrence time rather than the intensity of water stress that significantly affected the scaling of SLA. Moreover, the total effect of soil moisture on SLA was much higher in 2014 than that in 2013, but it was the opposite for heat conditions. The results imply that there is a trade-off mechanism between soil water and heat conditions in shaping the dynamic characteristics of SLA. The results may give insights into the accurate simulation of SLA dynamic characteristic and guidance for the production and management of maize.

Effects of urban nighttime light on the growth of Cinnamomum camphora

To understand the effects of urban artificial nighttime light on the growth of evergreen trees, we conducted a field investigation in a typical urban street planted with Cinnamomum camphora (a common evergreen street tree species in eastern China) in the Nanjing City, China. Along the street, trees from two types of growing locations with contrasting distances from the street lamp (just under the lamp vs. between two adjacent lamps) were selected. The growth-related plant functional traits were measured and compared. The results showed that trees grown under the lamp had a mean diameter at beast height (DBH) of 16.8 cm, current-year branch productivity (CBP) of 309.4 g·m-2, current-year leaf productivity (CLP) of 241.5 g·m-2, and leaf relative chlorophyll content (LCC) of 34.6 SPAD. Trees grown between lamps had a mean DBH of 15.5 cm, CBP of 273.4 g·m-2, CLP of 212.8 g·m-2, and LCC of 33.1 SPAD. DBH, CBP, CLP and LCC of the trees under the lamp were significantly higher than those between lamps. There was no significant difference in specific leaf area between trees from the two locations. Our results suggested that urban artificial nighttime light could promote the growth of C. camphora, and alter sunlight-determined characteristics of canopy growth vigor.

Simulated projections of boreal forest peatland ecosystem productivity are sensitive to observed seasonality in leaf physiology†.

We quantified seasonal CO2 assimilation capacities for seven dominant vascular species in a wet boreal forest peatland then applied data to a land surface model parametrized to the site (ELM-SPRUCE) to test if seasonality in photosynthetic parameters results in differences in simulated plant responses to elevated CO2 and temperature. We collected seasonal leaf-level gas exchange, nutrient content and stand allometric data from the field-layer community (i.e., Maianthemum trifolium (L.) Sloboda), understory shrubs (Rhododendron groenlandicum (Oeder) Kron and Judd, Chamaedaphne calyculata (L.) Moench., Kalmia polifolia Wangenh. and Vaccinium angustifolium Alton.) and overstory trees (Picea mariana (Mill.) B.S.P. and Larix laricina (Du Roi) K. Koch). We found significant interspecific seasonal differences in specific leaf area, nitrogen content (by area; Na) and photosynthetic parameters (i.e., maximum rates of Rubisco carboxylation (Vcmax25°C), electron transport (Jmax25°C) and dark respiration (Rd25°C)), but minimal correlation between foliar Na and Vcmax25°C, Jmax25°C or Rd25°C, which illustrates that nitrogen alone is not a good correlate for physiological processes such as Rubisco activity that can change seasonally in this system. ELM-SPRUCE was sensitive to the introduction of observed interspecific seasonality in Vcmax25°C, Jmax25°C and Rd25°C, leading to simulated enhancement of net primary production (NPP) using seasonally dynamic parameters as compared with use of static parameters. This pattern was particularly pronounced under simulations with higher temperature and elevated CO2, suggesting a key hypothesis to address with future empirical or observational studies as climate changes. Inclusion of species-specific seasonal photosynthetic parameters should improve estimates of boreal ecosystem-level NPP, especially if impacts of seasonal physiological ontogeny can be separated from seasonal thermal acclimation.

Meta-analyses of oil yield in Cuphea PSR23

Oil content and composition of Cuphea seed are of special economic value as raw materials for industrial and food applications. The inherent unpredictability in determining and predicting Cuphea’s oil yield is attributed, in part, to the indeterminate growth habit and the persistence of the domestication syndrome of this semi-domesticated potential oilseed crop. Meta-analysis using multivariate statistical modeling, computer simulations, and custom profiling was carried out on a database collated from several studies carried out in growth chamber, greenhouse and field experiments. Meta-analyses identified the importance of, and quantified direct and indirect relationships and tradeoffs between and within functional traits classified within five interrelated plant modules. Several multivariate statistical analyses procedures were employed in predicting oil content and oil yield, as performance measures of Cuphea at the plant and population levels of integration. The most parsimonious partial least squares regression model identified plant-, capsule-, and seed-based traits that can be used in reconstructing the best configuration needed for high agronomic performance at the individual plant and population levels. Variance-based structural equation modeling suggested that the variation in relative growth rate was strongly linked to differences in specific leaf area and leaf mass ratio; both traits expressed large positive direct and indirect effects on oil yield, but not oil content. Results of custom profiling suggested that seed yield, oil% and oil yield can be optimized by trait adjustments within the phenotypic and metabolic modules. Adjustments to thousand-seed weight and protein content would influence seed yield, oil yield and oil%, in a decreasing order. Improvements in eco-physiological traits, nutrient ratios and structural traits would lead to a slightly higher oil% and eventually higher oil yield.

Genotypic variability in Populus tremula L. affects how anthropogenic nitrogen enrichment influences litter decomposition

Background and aimsBoreal forests can receive substantial nitrogen (N) enrichment via atmospheric N deposition and industrial forest fertilization. While it is known that N enrichment can impact ecosystem properties, such as litter decomposition, it remains poorly understood how genetic variability within plant species modifies these impacts.MethodsWe grew replicates of ten Populus tremula L. genotypes (GTs) under 3 N conditions; ambient, and levels representing atmospheric N deposition and industrial forest fertilization. We measured leaf and litter physical and chemical traits, and conducted a litter decomposition assay.ResultsLeaf traits varied due to N treatment, GT, and constitutive tannin levels. Leaf traits were in some cases correlated with litter traits, and decomposition was influenced by single and interactive effects of N and GT. Nitrogen addition unexpectedly decelerated decomposition, potentially due to changes in specific leaf area (SLA). Variation in decomposition rates among the GTs was best explained by their differences in SLA, and lignin:N ratio. Nitrogen addition also caused a shift in which traits most strongly influenced decomposition.ConclusionsOur findings highlight that the considerable diversity present in tree species can have a strong influence on ecosystem processes, such as decomposition, and how these processes respond to environmental change.

Inter-specific differences in the dynamics of water use and pulse-response of co-dominant canopy species in a dryland woodland

Differences in the magnitude and timing of rainfall pulse-response among plant species in dryland ecosystems may facilitate the maintenance of species diversity, but this hypothesis remains untested among species that appear to occupy the same ecological niche. Here, we examined the pulse-response of co-dominant Acacia species forming the canopy of a dryland woodland. Trees received natural precipitation and supplemental irrigation equivalent to a ∼105 mm rainfall pulse over four days. The pulse-response was large and rapid irrespective of species or differences in minimum water potential during drought. Branch water potential increased from ∼−8 MPa to > −1 MPa at pre-dawn and foliage relative water content increased from 43.4% to 98.6% within five days of drought-break. Differences in midday water potential among species following the water pulse reflected differences in rates of stomatal conductance (gs) and likely as a consequence of differences in specific leaf area (SLA). We conclude there is no temporal partitioning of resources among the canopy species in the study woodland. Instead, water relations in these three closely related species were anisohydric and tightly coupled to soil water availability.

Winners and losers among tree species in Xishuangbanna: which traits are most important?

Massive human interference in natural ecosystems is resulting in a few “winners” and many “losers”. However, the drivers of this winner–loser replacement pattern remain poorly understood. The aim of the study reported here was to identify winners among the tree flora of Xishuangbanna and compare their functional traits, specific leaf area (SLA), wood density (WD), seed mass (SM) and maximum height (MH) with previously identified losers (i.e., endangered species). Fifteen native tree species were identified as winners from expert opinion, plot-based surveys of secondary forests and plotless surveys along roads. Twelve endangered tree species for which trait information could be obtained were used for comparison. Traits were compared with a Wilcoxon rank-sum test. Winners had significantly higher SLA, but lower WD. SM and MH did not differ significantly between groups. When the effects of phylogeny were removed by using phylogenetic generalized least squares, the difference in SLA became marginally insignificant. Principal component analysis resulted in two overlapping groups, showing that the selected traits were insufficient to distinguish winners and losers. Our results suggest that the “few winners, many losers” paradigm applies to trees in Xishuangbanna, with 15 species accounting for most trees in the disturbed habitats sampled.

Carbon acquisition strategies uncoupled from predictions derived from species life-cycle

We compare carbon use strategies of congeneric annual (P. gracilis and P. angustifolia) and perennial (P. mendocina and P. pinetorum) Physaria (Brassicaceae), to evaluate the relevance of eco-physiological traits as determinants of differences in growth and to add information on the current debate on the agro-ecological suitability of perennial species for grain production in low resource ecosystems. Because of differences in growth and in seed-output previously found within this genus, we hypothesized that C acquisition strategies would not be fully coupled with predictions derived from a species life-cycle. Further, we expected to find different suites of traits related to C-acquisition among perennial species of Physaria. We found species with high (P. gracilis and P. pinetorum) and low (P. mendocina and P. angustifolia) relative growth rate (RGR) and biomass. The variation in RGR was linked to differences in specific leaf area (SLA) and allocation to leaves (leaf mass ratio, LMR) and roots (root mass ratio, RMR), but not to the species life-cycle. Physaria gracilis had high allocation to leaf area (leaf area ratio, LAR), LMR, high SLA, and low RMR and carbohydrates reserves. The slow-growth strategy found in P. mendocina was linked to low LAR, low SLA and large below-ground allocation. The other species showed intermediate strategies between these two. The sets of traits present in P. gracilis and in P. mendocina are extremes in the C acquisition–conservation trade-off, and may allow them to cope with low resource environments in different ways. SLA, LMR and RMR were the main determinants of RGR, while total non-structural carbohydrates (TNC) and leaf longevity were linked to the life-cycle. Taken together these characters define the intermediate growth strategies of P. angustifolia and P. pinetorum. These intermediate strategies were not dependent on the species life cycle and support the hypothesis of uncoupled relationships between growth, C acquisition strategies and life-cycle.

Explaining within‐community variation in plant biomass allocation: a balance between organ biomass and morphology above vs below ground?

AbstractQuestionsIt remains unresolved why, despite the obvious functional importance of leaves and roots, co‐existing plant species can display highly contrasting biomass distributions of these organs. Building on the ‘functional equilibrium’ hypothesis, we hypothesize that co‐existing species can each achieve balanced resource acquisition above vs below ground by trading off the biomass vs morphology of structures responsible for resource acquisition, i.e. leaves and fine roots.MethodsWe tested this hypothesis in a natural field setting by measuring plant above‐ and below‐ground biomass and morphological traits associated with resource uptake – specific leaf area (SLA) and specific root length (SRL) – of 18 dominant angiosperm species from a sub‐alpine plant community.LocationNew Zealand South Island.ResultsWe found a significant negative relationship between the species leaf mass to fine root mass ratio and the SLA to SRL ratio when we considered eudicot species only. The SLA to SRL ratio and plant size explained 31% and 34% of the total variation in the species leaf to fine root mass ratio respectively, and 45% when used in combination (P &lt; 0.05 in all cases). Within a given plant size, 90% of the variation among species in total leaf area was due to differences in SLA, whereas variation in the fine root mass fraction was responsible for 71% of the variation among species in fine root length.ConclusionsIn support of our hypothesis, part of the difference between co‐occurring species in leaf and fine root biomass distribution could be explained by the variable morphologies of these organs as well as variation in plant size, independent of the plant economic strategy. We expect that this outcome may result from environmental and evolutionary constraints on plant species‐average traits, as well as plastic responses to local environmental conditions. These findings help explain why a diversity of strategies for achieving balanced resource acquisition can co‐exist within a single plant community.

Phenotypic plasticity and ecophysiological strategies in a tropical dry forest chronosequence: A study case with Poincianella pyramidalis

The plasticity of functional attributes is an important strategy for the acclimation and establishment of plants in areas that undergo natural regeneration. The irregular rainfall of the Brazilian tropical dry forest is an important environmental filter for the determination of the set of species that can successfully establish in different stages of the regeneration process and influences the plant acclimation responses to the environmental conditions at each stage of ecological succession. In order to test the hypothesis that pioneer plants which can establish themselves, at the same time, in areas at different stages of regeneration have high phenotypic plasticity, we investigated the endemic tree species Poincianella pyramidalis Tull., which can be found in all stages of the regeneration process in the Brazilian tropical dry forest. Three areas were selected at different successional stages (early, intermediate and late), and the functional attributes of water status, gas exchange, leaf nutrients, specific leaf area, leaf construction costs and payback time were assessed. In the three successional stages all individuals had similar age. Measurements were taken in April, for two consecutive years, a dry and a wet. The evaluated parameters in this study showed changes according to successional stage. The highest leaf water potential was found in the late stage in the rainy year and lowest in the dry year. This behavior may be related, in addition to soil water availability, to a stronger competition for resources in these areas. Gas exchange and nutrient use efficiency were higher in 2013 and in the late successional stage, which exhibited higher soil moisture, a lower vapor pressure deficit and higher nutrient mobilization. There were no differences in the construction cost per unit mass between the stages, but differences in specific leaf area led to changes in cost per area. The payback time was shorter in the wettest year. For the driest year, the late stage showed greater energy use efficiency. The results show that the P. pyramidalis’ attributes varies according to the successional stage, showing phenotypic plasticity. However, the strongest differences are observed between years, demonstrating that water is the main factor that coordinates the functional changes that confers its ability to acclimatize.

Effects of salinity on growth of plant species from terrestrializing fens

Terrestrializing lowland fens may be temporarily exposed to elevated surface water salinity, which may have serious consequences for nature conservation. We investigated the response of five fresh water fen plant species to elevated salinity.In a controlled greenhouse experiment, these species were exposed to salt concentrations up to 3000mg Cl− l−1.Total biomass of the five species together was significantly reduced for salinity levels from 200mg Cl− l−1. Four individual species showed leaf death and relative growth rate reduction, with effects at 1000mg Cl− l−1 for Succisa pratensis, Thelypteris palustris and Viola palustris, and 3000mg Cl− l−1 for Myosotis scorpioides. Comarum palustre showed no significant (.05 level) sensitivity.Biomass distribution was investigated as well. Root-shoot ratio of four species was affected by salinity, which in at least two cases seemed to be related to leaf death. Differences in specific leaf area as a result of salinity were only observed for C. palustre. Dry matter content increased in four species as a result of salinity.Salinity tolerance did not correspond to the environmental distributions of the species, nor could species traits be related to tolerance.Surface water salinity may affect vegetation development in terrestrializing fens at low concentrations. A reduction of plant growth would cause reduced fitness of some species and may lead to reduced root mat growth. Exposure to higher concentrations could eventually lead to a decrease of species richness.

Difference in shade tolerance affects foliage–sapwood response to thinning by two eucalypts

In eucalypt plantations in subtropical Australia, Eucalyptus dunnii exhibits greater diameter increment after thinning than more shade-tolerant Corymbia citriodora. To elucidate the mechanism underlying this difference, we investigated relationships between tree leaf area and sapwood area following thinning in 11-year-old E. dunnii and C. citriodora plantations. There was no significant difference in specific leaf area (SLA) between thinned and unthinned stands in E. dunnii and C. citriodora, whereas crown zone significantly affected SLA in the two eucalypts. At the whole-tree level non-linear leaf area (Al)–sapwood area (As) relationships were measured in both eucalypts by thinning treatment. A significant increase in Al/As ratio was only observed at the upper crown in thinned E. dunnii. The present results suggested the plastic nature of response of leaf characteristics in both eucalypts grown in different light environments and the species-specific pattern of crown-zone leaf responses to thinning in the two species, i.e. the top of the canopy appears to be driving greater growth response to thinning in the less shade tolerant E. dunnii compared with the more shade-tolerant C. citriodora. It is concluded that different thinning regimes should be applied in shade-tolerant and shade-intolerant eucalypt forests.