scholarly journals Contrasting adaptation and optimization of stomatal traits across communities at continental-scale

2021 ◽  
Author(s):  
Congcong Liu ◽  
Lawren Sack ◽  
Ying Li ◽  
Nianpeng He
Keyword(s):  
Niche Differentiation ◽  
Relative Importance ◽  
Ecosystem Productivity ◽  
Weighted Mean ◽  
Continental Scale ◽  
Community Weighted Mean ◽  
Use Efficiency ◽  
Stomatal Traits ◽  
Mean Variance ◽  
Maximum Stomatal Conductance

The maximum stomatal conductance (g), a major anatomical constraint on plant productivity, is a function of the stomatal area fraction (f) and stomatal space-use efficiency (e). However, f and g have been considered as equivalents, with e rarely considered, and their adaptation to the environment and their regulation of ecosystem productivity are unclear. Here, we analyzed the community-weighted mean, variance, skewness, and kurtosis of stomatal traits from tropical to cold-temperature forests. The variance of g and f was higher for arid sites, indicating greater functional niche differentiation, whereas that for e was lower, indicating convergence in efficiency. Besides, when other stomatal trait distributions remained unchanged, increasing kurtosis but decreasing skewness of g would improve ecosystem productivity, and f showed the opposite patterns. These findings highlight how the relative importance and equivalence of inter-related traits can differ at community scale.

Late-summer carbon fluxes from Canadian forests and peatlands along an east–west continental transect

2006 ◽  
Vol 36 (3) ◽  
pp. 783-800 ◽  
Author(s):  
Carole Coursolle ◽  
Hank A Margolis ◽  
Alan G Barr ◽  
T Andrew Black ◽  
Brian D Amiro ◽  
...  
Keyword(s):  
Large Scale ◽  
Ecosystem Respiration ◽  
Late Summer ◽  
Ecosystem Productivity ◽  
Diurnal Courses ◽  
Continental Scale ◽  
Young Forest ◽  
C Cycle ◽  
Use Efficiency ◽  
East West

Net ecosystem productivity (NEP) during August 2003 was measured by using eddy covariance above 17 forest and 3 peatland sites along an east–west continental-scale transect in Canada. Measured sites included recently disturbed stands, young forest stands, intermediate-aged conifer stands, mature deciduous stands, mature conifer stands, fens, and an open shrub bog. Diurnal courses of NEP showed strong coherence within the different ecosystem categories. Recently disturbed sites showed the weakest diurnal cycle; and intermediate-aged conifers, the strongest. The western treed fen had a more pronounced diurnal pattern than the eastern shrub bog or the Saskatchewan patterned fen. All but three sites were clearly afternoon C sinks. Ecosystem respiration was highest for the young fire sites. The intermediate-aged conifer sites had the highest maximum NEP (NEPmax) and gross ecosystem productivity (GEPmax), attaining rates that would be consistent with the presence of a strong terrestrial C sink in regions where these types of forest are common. These results support the idea that large-scale C cycle modeling activities would benefit from information on the age-class distribution and disturbance types within larger grid cells. Light use efficiency followed a pattern similar to that of NEPmax and GEPmax. Four of the five recently disturbed sites and all three of the peatland sites had low water use efficiencies.

scholarly journals On estimating the shape and dynamics of phenotypic distributions in ecology and evolution

2021 ◽  
Author(s):  
Brian Maitner ◽  
Aud Halbritter ◽  
Richard Telford ◽  
Tanya Strydom ◽  
Julia Chacon-Labella ◽  
...  
Keyword(s):  
Intraspecific Variation ◽  
Evolutionary Biology ◽  
R Package ◽  
Sampling Unit ◽  
Weighted Mean ◽  
Central Moments ◽  
Community Weighted Mean ◽  
The Mean ◽  
Mean Variance ◽  
Skewness And Kurtosis

Estimating the distribution of phenotypes in populations and communities is central to many questions in ecology and evolutionary biology. These distributions can be characterized by their moments: the mean, variance, skewness, and kurtosis. Typically, these moments are calculated using a community-weighted approach (e.g. community-weighted mean) which ignores intraspecific variation. As an alternative, bootstrapping approaches can incorporate intraspecific variation to improve estimates, and also quantify uncertainty in the estimate. Here, we compare the performance of different approaches for estimating the moments of trait distributions across a variety of sampling scenarios, taxa, and datasets. We introduce the traitstrap R package to facilitate inferences of trait distributions via bootstrapping. Our results suggest that randomly sampling ~9 individuals per sampling unit and species, focusing on covering all species in the community, and analysing the data using nonparametric bootstrapping generally enables reliable inference on trait distributions, including the central moments, of communities.

scholarly journals Physiological response of Swiss ecosystems to 2018 drought across plant types and elevation

2020 ◽  
Vol 375 (1810) ◽  
pp. 20190521 ◽  
Author(s):  
Mana Gharun ◽  
Lukas Hörtnagl ◽  
Eugénie Paul-Limoges ◽  
Shiva Ghiasi ◽  
Iris Feigenwinter ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Ecosystem Respiration ◽  
Coniferous Forest ◽  
Mixed Forest ◽  
Surface Conductance ◽  
Severe Drought ◽  
Ecosystem Productivity ◽  
Continental Scale ◽  
Use Efficiency

Using five eddy covariance flux sites (two forests and three grasslands), we investigated ecosystem physiological responses to the 2018 drought across elevational gradients in Switzerland. Flux measurements showed that at lower elevation sites (below 1000 m.a.s.l.; grassland and mixed forest) annual ecosystem productivity (GPP) declined by approximately 20% compared to the previous 2 years (2016 and 2017), which led to a reduced annual net ecosystem productivity (NEP). At the high elevation sites, however, GPP increased by approximately 14% and as a result NEP increased in the alpine and montane grasslands, but not in the subalpine coniferous forest. There, increased ecosystem respiration led to a reduced annual NEP, despite increased GPP and lengthening of the growing period. Among all ecosystems, the coniferous forest showed the most pronounced negative stomatal response to atmospheric dryness (i.e. vapour pressure deficit, VPD) that resulted in a decline in surface conductance and an increased water-use efficiency during drought. While increased temperature enhanced the water-use efficiency of both forests, de-coupling of GPP from evapotranspiration at the low-elevation grassland site negatively affected water-use efficiency due to non-stomatal reductions in photosynthesis. Our results show that hot droughts (such as in 2018) lead to different responses across plants types, and thus ecosystems. Particularly grasslands at lower elevations are the most vulnerable ecosystems to negative impacts of future drought in Switzerland. This article is part of the theme issue ‘Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale’.

scholarly journals Intraspecific trait changes have large impacts on community functional composition but do not affect ecosystem function

2021 ◽  
Author(s):  
Noémie A. Pichon ◽  
Seraina L. Cappelli ◽  
Eric Allan
Keyword(s):  
Global Change ◽  
Biomass Production ◽  
Aboveground Biomass ◽  
Belowground Biomass ◽  
Nitrogen Enrichment ◽  
Functional Composition ◽  
Relative Importance ◽  
Pathogen Removal ◽  
Weighted Mean ◽  
Community Weighted Mean

AbstractPlant functional traits can provide a more mechanistic understanding of community responses to global change and effects on ecosystem functions. In particular, nitrogen enrichment shifts trait composition by promoting dominance of fast growing, acquisitive plants (with high specific leaf area [SLA] and low leaf dry matter content [LDMC]), and such fast species have higher aboveground biomass production. Changes in mean trait values can be due to a shift in species identity, a shift in species relative abundance and/or a shift in intraspecific trait values. However, we do not know the relative importance of these three shifts in determining responses to global change and effects on function.We quantified the relative importance of composition, abundance and intraspecific shifts in driving variation in SLA and LDMC. We collected leaf samples in a large grassland experiment, which factorially manipulates functional composition (slow vs. fast species), plant species richness, nitrogen enrichment and foliar fungal pathogen removal. We fitted structural equation models to test the relative importance of abundance shifts, intraspecific shifts and sown trait composition in contributing to overall variation in community weighted mean traits and aboveground and belowground biomass production.We found that intraspecific shifts were as important as abundance shifts in determining community weighted mean traits, and even had large effects relative to a wide initial gradient in trait composition. Intraspecific trait shifts resulted in convergence towards intermediate SLA, in diverse communities, although convergence was reduced by nitrogen addition and enhanced by pathogen removal. In contrast, large intraspecific shifts in LDMC were not influenced by the treatments. Belowground biomass was reduced by SLA and increased by LDMC, while aboveground biomass increased in communities dominated by high SLA species. However, despite large intraspecific trait shifts, intraspecific variation in these traits had no effect on above or belowground biomass production.Our results add to a growing body of literature showing large intraspecific trait variation and emphasise the importance of using field sampled data to determine community composition. However, they also show that intraspecific variation does not affect ecosystem functioning and therefore trait response-effect relationships may differ between vs. within species.

scholarly journals Urban Environments Aid Invasion of Brown Widows (Theridiidae: Latrodectus geometricus) in North America, Constraining Regions of Overlap and Mitigating Potential Impact on Native Widows

2021 ◽  
Vol 9 ◽  
Author(s):  
Melissa Sadir ◽  
Katharine A. Marske
Keyword(s):  
North America ◽  
Ecological Niche Modeling ◽  
Climatic Factors ◽  
Ecological Impact ◽  
Niche Differentiation ◽  
Urban Environments ◽  
Geographic Ranges ◽  
Native Communities ◽  
Continental Scale ◽  
Latrodectus Geometricus

Urbanization is a major cause of biotic homogenization and habitat fragmentation for native communities. However, the role of urbanization on the success of biological invasions on a continental scale has yet to be explored. Urbanization may facilitate the establishment success of invasive species by minimizing niche differentiation between native and invaded ranges. In such cases, we might expect anthropogenic variables to have stronger influence on the geographic distribution of invasive compared to native populations. In this study, we use ecological niche modeling to define the distribution of non-native brown widow spider (Latrodectus geometricus) and three native black widows (L. hespersus, L. mactans, L. variolus) in North America and gauge the importance of urbanization on the geographic ranges of widows at a continental scale. We also quantify the geographic overlap of L. geometricus with each native widow to assess potential species and regions at risk of ecological impact. Consistent with our hypothesis, we find that the distribution of L. geometricus is strongly constrained to urban environments, while native widow distributions are more strongly driven by climatic factors. These results show that urbanization plays a significant role in facilitating the success of invasion, weakening the significance of climate on the realized niche in its invaded range.

Photosynthesis and Transpiration in Dicotyledonous Plants. I. Expanding Leaves of Tobacco and Sunflower.

1976 ◽  
Vol 3 (2) ◽  
pp. 247 ◽  
Author(s):  
HM Rawson ◽  
RG Woodward
Keyword(s):  
Growth Conditions ◽  
Relative Reduction ◽  
Co2 Uptake ◽  
Relative Importance ◽  
Tobacco Leaves ◽  
Leaf Emergence ◽  
Good Nutrition ◽  
Dicotyledonous Plants ◽  
Use Efficiency ◽  
Limited Period

The aims of this paper were (1) to determine if irradiance and nutrition influence the timing of peak photosynthesis (Fmax) in expanding tobacco Ieaves and (2) to assess the relative importance of stomatal (rs) and mesophyll (rm) resistances to CO2 uptake as leaves expand. Growth conditions affected rates of leaf expansion and final leaf areas (Amax) but not the time from leaf emergence to Amax (25 days). Patterns of photosynthesis with time were similar in all treatments-F rose rapidly to Fmax and then declined, and Fmax occurred on day 13 when the areas of leaves in different treatments were from 65-80 % Amax. We suggest that temperature may determine the timing of Fmax. Changes in both rs and rm were associated with changes in F prior to Fmax. Although changes in rm were up to five times greater than in rs during this period, the relative reduction in the two resistances was similar. Absolute changes in rs and rm were similar immediately after Fmax, and during this period of 7 days F declined by almost 50%. Thereafter, relative changes were closely matched. Possible mechanisms for the control of the resistances by the plant are discussed. We discuss the hypothesis that Fmax was maintained for only a limited period in expanding tobacco leaves because of the lack of a sink for assimilate. Expanding sunflower leaves maintained Fmax for a much longer period and reasons are presented for this different behaviour. Water use efficiency (ω) of tobacco leaves changed as they expanded and was greatest under good nutrition and poorest under low irradiance. Maximum ω for tobacco and sunflower was similar.

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