Leaf Carbon Content Research Articles

Leaf traits in dominant species from different secondary successional stages of deciduous forest on the Loess Plateau of northern China

AbstractQuestionsAre leaf traits related to plant growth efficiency different in different stages of forest succession on the Loess Plateau of northern Shaanxi, China? How do plant ecological strategies change with the progress of forest succession? Can a combination of some key leaf traits across species discriminate successional stages?LocationLoess Plateau region of northern Shaanxi, China.MethodsA set of 31 plots was established in the study area. Twenty‐two traits were measured in 31 dominant species representative of six succession stages: three pertaining to morphology, nine to stoichiometry and ten to physiological ecology. Six traits related to photosynthesis were measured in 15 species.ResultsEleven of 22 leaf traits differed significantly along the succession gradient. Early succession species had leaves with higher specific leaf area (SLA), higher leaf phosphorus (P) content (LPC) and lower N/P ratio, which assured higher growth rates and resource acquisition. Species from more advanced stages had a higher leaf dry mass content (LDMC), leaf carbon (C) content (LCC), leaf construction cost (CC) and C/P ratio, indicating improved competiveness through efficient nutrient conservation. None of the traits related to photosynthesis differed significantly among successional stages. Differences between traits among life forms also revealed that changes in traits with succession were due to the turnover of life forms in dominant species along the succession gradient.ConclusionsThe results provide clear evidence of functional links between leaf traits and forest succession in the Loess Plateau ecosystem, confirming trait‐based trade‐off of nutrient acquisition vs conservation during succession. We recommend using a combination of seven key leaf traits across species to discriminate between the succession stages.

Stoichiometry patterns of leaf carbon, nitrogen and phosphorous in aquatic macrophytes in eastern China

Ecological stoichiometry focuses on the balance of chemical elements and can enhance our understanding of the adaptive strategies of plants. However, few studies concerning the stoichiometry patterns of leaf carbon (C), nitrogen (N) and phosphorous (P) concentrations in aquatic macrophytes across latitudinal gradients have been reported. We collected 681 samples from 213 sites in eastern China, including 122 species from 55 genera and 35 families, to analyse variations in leaf C, N and P and their relationships with latitude, mean annual temperature and mean annual precipitation. The leaf C, N and P concentrations were significantly different among the four investigated life forms, but no significant differences were detected between seed plants and ferns. The N:P ratios were well constrained in different functional groups. The C:P and N:P ratios found in aquatic macrophytes in the present study were lower than previous findings, likely due to higher concentration of P in the surrounding environments. As the temperature increased, the leaf N concentration and leaf N:P ratio increased, whereas the leaf P concentration decreased. Furthermore, temperature was the key factor which can affect the stoichiometry patterns observed in widely distributed species directly and also indirectly at the community level. The slope of the regression line of the log10-transformed N concentrations against the log10-transformed P concentrations found in the seed plants of aquatic macrophytes was conserved and was greater than the slope of 2/3 reported for terrestrial plants, suggesting that the leaf N concentration increases faster relative to leaf P in aquatic than terrestrial plants.

Plant functional and phylogenetic turnover correlate with climate and land use in the Western Swiss Alps

Understanding the relative importance of historical and environmental processes in the structure and composition of communities is one of the longest quests in ecological research. Increasingly, researchers are relying on the functional and phylogenetic β-diversity of natural communities to provide concise explanations on the mechanistic basis of community assembly and the drivers of trait variation among species. The present study investigated how plant functional and phylogenetic β-diversity change along key environmental and spatial gradients in the Western Swiss Alps. Methods Using the quadratic diversity measure based on six functional traits: specific leaf area (SLA), leaf dry matter content (LDMC), plant height (H), leaf carbon content (C), leaf nitrogen content (N), and leaf carbon to nitrogen content (C/N) alongside a species-resolved phylogenetic tree, we relate variations in climate, spatial geographic, land use and soil gradients to plant functional and phylogenetic turnover in mountain communities of the Western Swiss Alps. Important findings Our study highlights two main points. First, climate and land use factors play an important role in mountain plant community turnover. Second, the overlap between plant functional and phylogenetic turnover along these gradients correlates with the low phylogenetic signal in traits, suggesting that in mountain landscapes, trait lability is likely an important factor in driving plant community assembly. Overall, we demonstrate the importance of climate and land use factors in plant functional and phylogenetic community turnover, and provide valuable complementary insights into understanding patterns of β-diversity along several ecological gradients.

Strong leaf morphological, anatomical, and physiological responses of a subtropical woody bamboo (Sinarundinaria nitida) to contrasting light environments

Dwarf bamboos are an important understory component of the lowland and montane forests in the subtropical regions of Asia and South America, yet little is known about their physiology and phenotypic plasticity in response to changing light environments. To understand how bamboo species adapt to different light intensities, we examined leaf morphological, anatomical, and physiological differentiation of Sinarundinaria nitida (Mitford) Nakai, a subtropical woody dwarf bamboo, growing in open and shaded natural habitats in the Ailao Mountains, SW China. Compared with leaves in open areas, leaves in shaded areas had higher values in leaf size, specific leaf area, leaf nitrogen, and chlorophyll concentrations per unit area but lower values in leaf thickness, vein density, stomatal density, leaf carbon concentration, and total soluble sugar concentration. However, stomatal size and leaf phosphorus concentration per unit mass remained relatively constant regardless of light regime. Leaves in the open habitat exhibited a higher light-saturated net photosynthetic rate, dark respiration rate, non-photochemical quenching, and electron transport rate than those in the shaded habitat. The results of this study revealed that the bamboo species exhibited a high plasticity of its leaf structural and functional traits in response to different irradiances. The combination of high plasticity in leaf morphological, anatomical, and physiological traits allows this bamboo species to grow in heterogeneous habitats.

Intraspecific trait variability mediates the response of subalpine grassland communities to extreme drought events

Summary Climate change is expected to increase the magnitude and the frequency of extreme climatic events such as droughts. Better understanding how plant communities will respond to these droughts is a major challenge. We expect the response to be a shift in functional trait values resulting from both species turnover and intraspecific trait variability, but little research has addressed the relative contribution of both components. We analysed the short‐term functional response of subalpine grassland communities to a simulated drought by focusing on four leaf traits (LDMC: leaf dry matter content, SLA: specific leaf area, LNC: leaf nitrogen concentration and LCC: leaf carbon concentration). After evaluating species turnover and intraspecific variability separately, we determined their relative contribution in the community functional response to drought, reflected by changes in community‐weighted mean traits. We found significant species turnover and intraspecific variability, as well as significant changes in community‐weighted mean for most of the traits. The relative contribution of intraspecific variability to the changes in community mean traits was more important (42–99%) than the relative contribution of species turnover (1–58%). Intraspecific variability either amplified (for LDMC, SLA and LCC) or dampened (for LNC) the community functional response mediated by species turnover. We demonstrated that the small contribution of species turnover to the changes in community mean LDMC and LCC was explained by a lack of covariation between species turnover and interspecific trait differences. Synthesis. These results highlight the need for a better consideration of intraspecific variability to understand and predict the effect of climate change on plant communities. While both species turnover and intraspecific variability can be expected following an extreme drought, we report new evidence that intraspecific variability can be a more important driver of the short‐term functional response of plant communities.

Intra-Specific Leaf Trait Variation: Management and Fertility Matter More than the Climate at Continental Scales

Plant functional traits have contributed to the understanding of how vegetation responds to management, community assembly and how vegetation controls ecosystem processes. As traits are time consuming to measure – and it may not always be feasible or practical to measure all traits within a study – great reliance has been put on using trait values from databases. This ignores intraspecific trait variability and the traits’ responses to the environment. This study uses trait values measured as part of a large-scale investigation of land use impacts on vegetation to assess how environmental factors, specifically climate, soil and management, control inter-population level intra-specific variation in key traits. There was clear evidence that intra-specific variation in leaf carbon content, leaf dry matter content, leaf nitrogen content and specific leaf area were all sensitive to edaphic factors and to management, but only leaf dry matter content was linearly affected by the climate (rainfall). There were also significant interactions between climate and species identity for leaf dry matter content and leaf nitrogen content, suggesting that species responses to the climate are not uniform or simple. The results of this study suggest that site fertility and management ought to be associated with trait data in databases to allow for the incorporation of intra-specific variation in analyses and that more research is needed to identify the shape of trait:climate relationships.

鄱阳湖湿地两种优势植物叶片C、N、P动态特征

2011年2-6月在鄱阳湖南矶湿地国家级自然保护区逐月测定了灰化苔草(<em>Carex cinerascens</em>)、南荻(<em>Triarrhena lutarioriparia</em>)叶片C、N、P含量及其地上生物量,以阐明鄱阳湖湿地优势植物C、N、P含量及化学计量比动态特征与控制因子,探讨湿地养分利用与限制状况。结果表明:(1)两种优势植物叶有机碳含量变化范围分别为365.3-386.6 mg/g和352.6-393.2 mg/g,平均值(±标准差)分别为(375.5±17.4) mg/g和(371.7±12.5) mg/g;叶N含量分别为6.96-17.59 mg/g和5.50-20.68 mg/g,平均值分别为(11.35±1.40) mg/g和(11.54±0.84) mg/g;叶P含量变化范围为0.65-2.14 mg/g和0.57-2.25 mg/g,平均含量为(1.56±0.69) mg/g和(1.55±0.68) mg/g。两种植物C:N、C:P、N:P平均值分别为44.00、1068.46、21.30和47.90、1059.92、21.19,C、N、P及其化学计量比种间差异不显著(<em>P</em> > 0.05)。(2)气温与地上生物量是N、P及其化学计量比季节变化的主要控制因子,气温和生物量对两种优势植物叶片氮、磷含量的影响要高于对叶有机碳含量的影响。(3)植物C:N、C:P与地上生物量变化趋势基本一致,显示N、P养分利用效率随植物的快速生长而提高;根据两种优势植物及土壤N、P含量与化学计量比来判断,研究区植物更多地受氮限制。;Carbon(C), nitrogen (N) and phosphorous (P) stoichiometry are critical indicators of biogeochemical coupling in terrestrial ecosystems. Stoichiometric homoeostasis plays important role in modulating structure, functioning and stability of ecosystems. However, our current understanding of C:N:P stoichiometry is mainly derived from observations across space, and little is known about its dynamics through the time. Besides, stoichiometric researches have been carried out in various terrestrial ecosystems in China, but few data are available for wetland ecosystem. Wetland plants live in more fluctuant environments than terrestrial plants, and responses of wetland ecosystem to climate change are more sensitive than terrestrial ecosystem. The C:N:P stoichiometry for wetland plants may differ from terrestrial plants. Hence, more researches on dynamics of leaf carbon, nitrogen and phosphorus concentrations, as well as their stoichiometry for wetland plants are necessary. Poyang Lake is the largest fresh lake in China, with huge areas of wetland occurred in non-flood periods in a year. In this study, a wetland dominated by plant species of<em> Carex cinerascens</em> and <em>Triarrhena lutarioriparia </em>was selected in the national nature reserve, Nanji wetlands of Poyang Lake. Subsequently, carbon, nitrogen and phosphorus concentrations, as well as aboveground plant biomass were measured every month from February to June in 2011. The objectives of this study were as follows:(1) to clarify dynamics and control factors of the dominant plants' carbon, nitrogen and phosphorus concentrations, as well as their stoichiometric ratios, (2) to discuss the current status of wetland nutrient utilization and nutrient limitation. Results showed that leaf carbon ranged from 365.3 to 386.6 mg/g for <em>Carex cinerascens</em>, and 352.6 to 393.2 mg/g for <em>Triarrhena lutarioriparia</em>, respectively. Leaf nitrogen differed from 6.96 to 17.59 mg/g for <em>Carex cinerascens</em>, and 5.50 to 20.68 mg/g for <em>Triarrhena lutarioriparia</em>, respectively. Besides, the ranges of leaf phosphorus were 0.65 to 2.14 mg/g and 0.57 to 2.25 mg/g for the two species, respectively. The arithmetic means were (375.5±17.4) mg/g and (371.7±12.5) mg/g for carbon, (11.35±1.40) mg/g and (11.54±0.84) mg/g for nitrogen, (1.56±0.69) mg/g and (1.55±0.68) mg/g for phosphorus, respectively. The arithmetic means of C:N, C:P and N:P ratios were 44.00, 1068.46 and 21.30 for <em>Carex cinerascens</em> and 47.90, 1059.92 and 21.19 for <em>Triarrhena lutarioriparia</em>.There was no significant difference of carbon, nitrogen and phosphorus concentrations, as well as stoichiometric ratios between the two species (<em>p</em> > 0.05). Moreover, both leaf nitrogen and phosphorous showed clear dynamic patterns. Leaf nitrogen and phosphorus concentrations peaked at the early stage of growth, and then decreased substantially during the fast growth period, but increased a little by the end of the growing season. Temperature and aboveground biomass were the two main factors controlling the dynamic patterns of nitrogen, phosphorus concentrations and their stoichiometric ratios. C:N and C:P ratios were positively correlated with aboveground biomass, which suggested nutrient use efficiency of nitrogen and phosphorus were greatly affected by the growth rate. Additionally, according to nitrogen and phosphorus concentrations both in soil and the two dominant plants' leaves, as well as the stoichiometric ratios of nitrogen to phosphorus, the plants in the wetland were more limited by nitrogen, rather than by phosphorous.

呼伦贝尔草地植物群落与土壤化学计量学特征沿经度梯度变化

In large scale,plant stoichiometry is mainly affected by latitude and longitude.Many works has have been done to study the effects of temperature on plant stoichiometry along the latitude gradient,while researches on the precipitation along the longitude gradient are rare.In this research,we studied the stoichiometry characteristics of grassland communities along the longitude gradient in Hulunbeir.The results showed as follow: 1)the range of leaf carbon was 440.76—452.72 mg/g,leaf nitrogen was 17.79—30.88 mg/g,and leaf phosphorous was 1.31—1.71 mg/g.Both the leaf carbon and C/N ratio significantly increased with the increasing longitude.Leaf nitrogen significantly decreased with the increasing longitude,and leaf phosphorous showed an increasing tendency,however,the relationship between leaf phosphorous and longitude was not significant.The amount of carbon,nitrogen and phosphorous of grassland communities significantly increased with the increasing longitude.2)For the 0—10cm soil depth,total carbon,total nitrogen,total phosphorus and organic carbon were significantly affected by precipitation and increased with longitude;however,soil ammonium nitrogen(NH+4-N) and nitrate nitrogen(NH-3-N) were less affected by precipitation and didn′t change significantly with longitude.3)Soil total carbon,organic carbon,total nitrogen,total phosphorus and available phosphorus did not have significant effects on plant leave carbon,nitrogen and phosphorus,but had a significant effects on the amount of carbon,nitrogen and phosphorous of grassland communities.In this studied region,soil available phosphorus was 8.13 mg/ kg,which was higher than the Global Average Value(7.65 mg/kg),but the average leaf phosphorous was 1.5 mg/g and lower than the Global Average Value(1.77 mg/kg).Our research suggested that variation in leaf carbon,leaf nitrogen and leaf phosphorus concentration and its strong correlation with precipitation reveal that,to some extent,stoichiometry characteristics at the community level are adaptive to local precipitation condition.The amount of carbon,nitrogen and phosphorus of grassland communities have a high relationship with the local precipitation,and have a significant correlation with soil total carbon,total nitrogen,total phosphorus.The shortage in soil available phosphorus is not the major factor for the low plant leaf phosphorus concentration in our studied region,and the low plant leaf phosphorus is a result of adaptation.

Do warmer growing seasons ameliorate the recovery of mountain birches after winter moth outbreak?

Subarctic mountain birch (Betula pubescens ssp. czerepanovii) forests in northern Fennoscandia have shown a slight recovery from recent severe defoliation by the winter moth (Operophtera brumata). This development in trees is hypothesized to be a result of ameliorated growing conditions through increased summer temperatures. We examined if accumulated thermal sum affects the ability of mountain birches to tolerate foliage losses. We quantified the number of leaf-bearing short shoots, the emergence of inflorescences and the seasonal height growth of long shoots in both intact and defoliated trees. We also determined the concentrations of carbon and nitrogen in leaves and carbohydrates in roots. Our results show that defoliation constrained the growth of long shoots, as well as the emergence of inflorescences regardless of thermal sum accumulation. However, the number of leaf-bearing short shoots did not differ between intact and defoliated trees. In the both tree groups, the amounts of emerging leaves increased as a response to thermal sum accumulation. Also the leaf carbon concentration increased in defoliated trees at higher thermal sums, whereas it decreased in intact controls. Generally, the mean carbohydrate concentrations were greater in roots of defoliated than intact trees. However, with increased thermal sums, root carbohydrates increased in intact trees but remained the same in defoliated trees. We conclude that thermal sum accumulation does not greatly promote the recovery of mountain birches. Although the damaged trees produced more leaves at warmer growing sites, this did not increase their height growth or carbohydrate gain in roots.

Effects of grazing exclusion on the spatial variability of subalpine plant communities: A multiscale approach

The fine-scale spatial structure of plant communities is a key component for understanding the dynamics in vegetation following changes in land management but needs to be assessed at an appropriate scale. We studied the response of plant diversity and spatial variability of species and trait composition to grazing vs. non-grazing (>20 years) using different grain sizes of sampling in three subalpine plant communities. Species composition, diversity, and the aggregated values of 4 leaf traits were assessed at 7 grain sizes (within quadrats ranging from 25 cm 2 to 1 m 2) in 9 grazed and ungrazed paired plots. Evenness and species richness showed a strongly community-dependent response as they increased following grazing exclusion in the less productive community and decreased in the two more productive ones. Although species richness was influenced by grazing exclusion at grains larger than 625 cm 2, evenness was affected at the finest grain investigated (25 cm 2). In contrast, spatial variability of species composition was similarly affected across the three plant communities and increased following grazing exclusion from the 100 cm 2-grain size. Grazing led to a sharper decline of spatial variability with increasing quadrat size revealing that the grain of spatial heterogeneity was finer in grazed plots relative to that in ungrazed ones. The response of spatial variability of aggregated trait values was less consistent, possibly because of functional redundancy between species. However, grazing exclusion increased the spatial variability of the aggregated values of leaf dry matter content and leaf carbon and nitrogen content. We suggest that spatial variability of species composition could be useful for detecting within-community changes in response to grazing management as it was detectable using a very fine scale of sampling and responded similarly to grazing treatment in every community. Such spatial variability in species composition can induce spatial organization of plant traits that may be important for community functioning.

The impact of climate change on the growth of tropical agroforestry tree seedlings

Several studies have been conducted on the response of crops to greater concentrations of atmospheric CO2 (CO2 fertilization) as a result of climate change, but only few studies have evaluated this effect on multipurpose agroforestry tree species in tropical environments. The objectives of this study were to quantify differences in growth parameters and in leaf carbon (C) and nitrogen (N) concentrations of Cedrela odorata L. and Gliricidia sepium (Jacq.) Walp. seedlings under current ambient temperature (32°C daytime, 22°C night time) and CO2 (360 ppm) (AMB); CO2 fertilization (800 ppm, 32°C daytime, 22°C night time) (fCO2); elevated ambient temperature (360 ppm, 34°C daytime, 25°C night time) (TEMP); and a combination of elevated temperature (32°C daytime, 22°C night time) and CO2 fertilization (800 ppm) (TEMPxfCO2). Results showed significant differences (P < 0.05) in seedling growth parameters (seedling height, number of stem leaves, leaf area ratio, shoot and root biomass, and shoot/root ratio) between treatments for both tree species. The greatest increases in growth parameters occurred in the TEMP and TEMPxfCO2 treatments compared to the AMB treatment for both tree species. However, growth parameters were significantly lower (P < 0.05) in the fCO2 treatment compared to that of the AMB treatment. Leaf N concentration was 1.1 to 2.1 times lower (P < 0.05) in all treatments when compared to current ambient conditions (AMB) in both tree species, but no significant changes in leaf C concentrations were observed. Results from our study suggested that fCO2 had the greatest negative impact on tree growth parameters, and leaf N concentrations were affected negatively in all treatments compared to current ambient conditions. It is expected that such changes in growth parameters and plant N content may impact the long-term cycling of nutrients in agroforestry systems.

Leaf attributes and tree growth in a tropical dry forest

Questions: How are leaf attributes and relative growth rate (RGR) of the dominant tree species of tropical deciduous forest (TDF) affected by seasonal changes in soil moisture content (SMC)? What is the relationship of functional attributes with each other? Can leaf attributes singly or in combination predict the growth rate of tree species of TDF? Location: Sonebhadra district of Uttar Pradesh, India. Methods: Eight leaf attributes, specific leaf area (SLA); leaf carbon concentration (LCC); leaf nitrogen concentration (LNC); leaf phosphorus concentration (LPC); chlorophyll concentration (Chl), mass-based stomatal conductance (Gsmass); mass based photosynthetic rate (Amass); intrinsic water use efficiency (WUEi); and relative growth rate (RGR), of six dominant tree species of a dry tropical forest on four sites were analysed for species, site and season effects over a 2-year period. Step-wise multiple regression was performed for predicting RGR from mean values of SMC and leaf attributes. Path analysis was used to determine which leaf attributes influence RGR directly and which indirectly. Results: Species differed significantly in terms of all leaf attributes and RGR. The response of species varied across sites and seasons. The attributes were positively interrelated, except for WUEi, which was negatively related to all otherattributes. The positive correlation was strongest between GsmassandAmass and the negative correlation was strongest between Gsmass and WUEi. Differences in RGR due to site were not significant when soil moisture was controlled, but differences due to season remained significant. The attributes showed plasticity across moisture gradients, which differed among attributes and species. Gsmass was the most plastic attribute. Among the six species, Terminalia tomentosaexhibited the greatest plasticity in six functional attributes. In the stepwise multiple regression, Amass, SLA and Chl among leaf attributes and SMC among environmental factors influenced the RGR of tree species. Path analysis indicated the importance of SLA, LNC, Chl and Amass in determining RGR. Conclusion: Amass, SMC, SLA and Chl in combination can be used to predict RGR but could explain only three-quarters of the variability in RGR, indicating that other traits/factors, not studied here, are also important in modulating growth of tropical trees. RGR of tree species in the dry tropical environment is determined by soil moisture, whereas the response of mature trees of different species is modulated by alterations in key functional attributes such as SLA, LNC and Chl.

Taller and larger: shifts in Arctic tundra leaf traits after 16 years of experimental warming

AbstractUnderstanding plant trait responses to elevated temperatures in the Arctic is critical in light of recent and continuing climate change, especially because these traits act as key mechanisms in climate‐vegetation feedbacks. Since 1992, we have artificially warmed three plant communities at Alexandra Fiord, Nunavut, Canada (79°N). In each of the communities, we used open‐top chambers (OTCs) to passively warm vegetation by 1–2 °C. In the summer of 2008, we investigated the intraspecific trait responses of five key species to 16 years of continuous warming. We examined eight traits that quantify different aspects of plant performance: leaf size, specific leaf area (SLA), leaf dry matter content (LDMC), plant height, leaf carbon concentration, leaf nitrogen concentration, leaf carbon isotope discrimination (LCID), and leaf δ15N. Long‐term artificial warming affected five traits, including at least one trait in every species studied. The evergreen shrub Cassiope tetragona responded most frequently (increased leaf size and plant height/decreased SLA, leaf carbon concentration, and LCID), followed by the deciduous shrub Salix arctica (increased leaf size and plant height/decreased SLA) and the evergreen shrub Dryas integrifolia (increased leaf size and plant height/decreased LCID), the forb Oxyria digyna (increased leaf size and plant height), and the sedge Eriophorum angustifolium spp. triste (decreased leaf carbon concentration). Warming did not affect δ15N, leaf nitrogen concentration, or LDMC. Overall, growth traits were more sensitive to warming than leaf chemistry traits. Notably, we found that responses to warming were sustained, even after many years of treatment. Our work suggests that tundra plants in the High Arctic will show a multifaceted response to warming, often including taller shoots with larger leaves.

Are temporal variations of leaf traits responsible for seasonal and inter‐annual variability in ecosystem CO2 exchange?

Summary 1. Seasonal and inter‐annual variability in ecosystem carbon dioxide (CO2) exchange is attributed to numerous climate drivers. However, climate effects on metabolism often override ecological functions. This study seeks insight into which biological and ecological processes influence temporal patterns of ecosystem productivity in natural ecosystems. 2. The specific objectives of this study are to (i) identify seasonal and inter‐annual patterns of ecosystem‐level photosynthesis in relation to climatic conditions, (ii) examine and compare seasonal and inter‐annual variations in leaf traits for annual grasses and oak trees across multiple years, and (iii) explore interactions among leaf traits and ecosystem‐level photosynthesis across multiple seasons and years. 3. We conducted this study in a woody savanna and open grassland in California, USA. Ecosystem‐level photosynthetic rates of annual grasses (Agrass) and oak tree canopy (Acanopy) were deduced from eddy covariance measurements over a 7‐year period (2001 and 2007). In conjunction, we sampled grass and oak leaves at weekly to monthly intervals and constructed a multi‐year time series of leaf nitrogen concentration (N), leaf mass per unit area (LMA), leaf carbon concentration (C), and leaf carbon stable isotope discrimination (Δ). 4. Given the same grass community age or tree canopy age, inter‐annual variations of the photosynthetic rates were up to 1–2 gC m−2 day−1 for annual grasses and oak trees while the two types of vegetation were exposed to different, wide ranges of inter‐annual climate fluctuations: up to 5 °C in daily mean soil temperature, 15% in soil moisture, and 10 mol m−2 day−1 in photosynthetically active radiation. 5. While both grass and oak leaf traits varied seasonally and inter‐annually, they experienced temporal patterns and seasonal peaks that were distinct from one another. Multi‐year means of grass leaf N, C, Δ, and LMA were 2·3%, 40·8%, 22·6‰ and 71·3 g m−2, respectively; multi‐year means of oak leaf N, C, Δ, and LMA were 1·9%, 45·1%, 20·5‰ and 132 g m−2, respectively. 6. Based on the analysis of variance, seasonal and inter‐annual terms were associated with Agrass or Acanopy up to 90% or 81%. On the other hand, variations in leaf N, LMA, C, Δ, and their interactions could statistically explain about 53% and 26% of variations in Agrass and Acanopy, respectively. 7. We discussed possible biological and ecological processes involved in regulating seasonal and inter‐annual variability in ecosystem‐level photosynthesis. Clearly, seasonal and inter‐annual variation in ecosystem photosynthesis was strongly associated with the dynamics of leaf traits.

Linking post-fire regenerative strategy and leaf nutrient content in Mediterranean woody plants

Abstract We explored differences in leaf nutrient contents between species from Mediterranean shrublands with the ability to resprout after disturbances such as fire (resprouters) and others without this capacity (non-resprouters). Since it is to be expected that resprouting capacity is related to a more conservative use of nutrients, we hypothesize that resprouter and non-resprouter species will differ in their leaf nutrient concentrations. We measured the following leaf traits: leaf carbon content (LCC), leaf nitrogen content, leaf phosphorous content (LPC), leaf potassium content, leaf calcium content (LCaC), leaf magnesium content and leaf sodium content, in 30 woody species coexisting in a coastal shrubland. We also considered the influence of species’ taxonomic affiliation in our analysis. Non-resprouters had higher LPC and LCaC than resprouter species, and lower LCC, which could be related to their cell and life-history properties. This study also suggests that non-resprouter species have more P in their leaves and are less limited by P than resprouter species. Overall, the differences in leaf nutrient contents suggest that shifts in the proportion of resprouter and non-resprouter species resulting from changes in the fire regime may have effects on the functional properties of the ecosystem.

Latitudinal Variation in Leaf and Tree Traits of the Mangrove Avicennia germinans (Avicenniaceae) in the Central Region of the Gulf of Mexico

ABSTRACTThe variation in leaf mass per area, leaf nutrients (% carbon, nitrogen and phosphorus), and the allometric relation between tree height and diameter of the black mangrove, Avicennia germinans, were explored in nine mangrove forests in similar environments along a 5° latitudinal gradient in the central region of the Gulf of Mexico, as indicated by a southward increase in temperature and precipitation. There was no correlation between leaf nitrogen or phosphorus content and latitude. Leaf mass per area and leaf carbon content were positively correlated with latitude and negatively correlated with temperature and annual rainfall, whereas asymptotic tree height and maximum diameter showed the opposite trend. Such patterns suggest a trade‐off between leaf traits and tree size which may be constrained by the same environmental factors along a dry‐cold to humid‐warm latitudinal gradient.

Altitudinal differences in the leaf fitness of juvenile and mature alpine spruce trees (Picea crassifolia)

In many plant species, leaf morphology varies with altitude, an effect that has been attributed to temperature. It remains uncertain whether such a trend applies equally to juvenile and mature trees across altitudinal gradients in semi-arid mountain regions. We examined altitude-related differences in a variety of needle characteristics of juvenile (2-m tall) and mature (5-m tall) alpine spruce (Picea crassifolia Kom.) trees growing at altitudes between 2501 and 3450 m in the Qilian Mountains of northwest China. We found that stable carbon isotope composition (delta(13)C), area- and mass-based leaf nitrogen concentration (N(a), N(m)), number of stomata per gram of nitrogen (St/N), number of stomata per unit leaf mass (St/LM), projected leaf area per 100 needles (LA) and leaf mass per unit area (LMA) varied nonlinearly with altitude for both juvenile and mature trees, with a relationship reversal point at about 3100 m. Stomatal density (SD) of juvenile trees remained unchanged with altitude, whereas SD and stomatal number per unit length (SNL) of mature spruce initially increased with altitude, but subsequently decreased. Although several measured indices were generally found to be higher in mature trees than in juvenile trees, N(m), leaf carbon concentration (C(m)), leaf water concentration (LWC), St/N, LA and St/LM showed inconsistent differences between trees of different ages along the altitudinal gradient. In both juvenile and mature trees, delta(13)C correlated significantly with LMA, N(m), N(a), SNL, St/LM and St/N. Stomatal density, LWC and LA were only significantly correlated with delta(13)C in mature trees. These findings suggest that there are distinct ecophysiological differences between the needles of juvenile and mature trees that determine their response to changes in altitude in semi-arid mountainous regions. Variations in the fitness of forests of different ages may have important implications for modeling forest responses to changes in environmental conditions, such as predicted future temperature increases in high altitude areas associated with climate change.

Non-Destructive Assessment of Arundo donax (Poaceae) Leaf Quality

ABSTRACT Leaf carbon (C) content, leaf nitrogen (N) content, and C:N ratio are especially useful for understanding plant-herbivore interactions and may be important in developing control methods for the invasive riparian plant Arundo donax L. We measured C content, N content, C:N ratio, and chlorophyll index (SPAD 502 reading) for 768 leaves from A. donax collected over a five year period at several locations in California, Nevada, and Texas. Leaf N was more variable than leaf C, and thus we developed a linear regression equation for estimating A. donax leaf N from the leaf chlorophyll index (SPAD reading). When applied to two independent data sets, the equation (leaf N content % = −0.63 + 0.08 x SPAD) produced realistic estimates that matched seasonal and spatial trends reported from a natural A. donax population. Used in conjunction with the handheld SPAD 502 meter, the equation provides a rapid, non-destructive method for estimating A. donax leaf quality.

Genetic Architecture of Leaf Ecophysiological Traits in Helianthus

We investigated quantitative trait loci (QTLs) for several leaf chemistry traits in early-generation hybrids between Helianthus annuus and Helianthus petiolaris, the parental species of the ancient diploid hybrid sunflower species Helianthus anomalus, Helianthus deserticola, and Helianthus paradoxus. We grew individuals of a second-generation backcross (BC(2)) toward H. petiolaris under optimum conditions in a glass house experiment. Trait values were measured once for each individual. In addition, genotypic data previously determined for each individual were employed for composite interval mapping of QTLs. We detected QTLs for leaf carbon concentration, leaf nitrogen concentration, leaf nitrogen per unit area, and photosynthetic nitrogen use efficiency. Leaf carbon isotope discrimination (delta(13)C) and leaf nitrogen isotopic composition (delta(15)N) were analyzed, but no significant QTLs were found for these traits. Interestingly, two neighboring loci explained a relatively large percentage of the variation in leaf nitrogen per unit area. This was notable because leaf nitrogen has been shown to strongly affect the fitness of early-generation sunflower hybrids in the H. anomalus habitat, and QTLs of large effect are expected to respond relatively quickly to selection. We speculate that the genetic architecture underlying leaf nitrogen may have facilitated the colonization of active desert sand dunes by H. anomalus.

Genetic variation of leaf traits related to productivity in aPopulus deltoides×Populus nigrafamily

In breeding and selection, two of the main goals of hybridization are to combine favourable traits from different species and to obtain high hybrid vigor (or heterosis). The objectives of our study were (1) to determine which leaf traits are most closely linked to growth in a cross between Populus deltoides Bartr. ex Marsh. and Populus nigra L. and (2) to estimate the relevance of this cross for selection of highly productive genotypes. To achieve these objectives, 26 poplar F1hybrids and their parents were studied during their second growing season in central France. Tree growth (i.e., growth rates of stem height, circumference, and volume) was monitored during 1 month, and leaf traits (i.e., increases in number of leaves, maximum individual leaf area, specific leaf area, petiole length, and dry mass, leaf carbon and nitrogen contents, and internode length) were estimated at the end of the 1-month period. Growth traits were tightly correlated to most of the leaf traits. More precisely, it appeared that stem volume growth rate can be decomposed into two single leaf characteristics: maximum individual leaf area and leaf increment rate. All traits showed moderate values of broad-sense heritability. Heterosis as well as coefficients of genetic variation were also modest.