Seasonal trends in leaf-level photosynthetic capacity and water use efficiency in a North American Eastern deciduous forest and their impact on canopy-scale gas exchange.

Vegetative transpiration (E) and photosynthetic carbon assimilation (A) are known to be seasonally dynamic, with changes in their ratio determining the marginal water use efficiency (WUE). Despite an understanding that stomata play a mechanistic role in regulating WUE, it is still unclear how stomatal and nonstomatal processes influence change in WUE over the course of the growing season. As a result, limited understanding of the primary physiological drivers of seasonal dynamics of canopy WUE remains one of the largest uncertainties in earth system model projections of carbon and water exchange in temperate deciduous forest ecosystems.

The effect of the vertical gradients of photosynthetic parameters on the CO assimilation and transpiration of a Panamanian tropical forest.

Terrestrial biosphere models (TBMs) include the representation of vertical gradients in leaf traits associated with modeling photosynthesis, respiration, and stomatal conductance. However, model assumptions associated with these gradients have not been tested in complex tropical forest canopies. We compared TBM representation of the vertical gradients of key leaf traits with measurements made in a tropical forest in Panama and then quantified the impact of the observed gradients on simulated canopy-scale CO and water fluxes.

Short-term variation in leaf-level water use efficiency in a tropical forest.

The representation of stomatal regulation of transpiration and CO assimilation is key to forecasting terrestrial ecosystem responses to global change. Given its importance in determining the relationship between forest productivity and climate, accurate and mechanistic model representation of the relationship between stomatal conductance (g ) and assimilation is crucial. We assess possible physiological and mechanistic controls on the estimation of the g (stomatal slope, inversely proportional to water use efficiency) and g (stomatal intercept) parameters, using diurnal gas exchange surveys and leaf-level response curves of six tropical broadleaf evergreen tree species.

Late-day measurement of excised branches results in uncertainty in the estimation of two stomatal parameters derived from response curves in Populus deltoides Bartr. × Populus nigra L.

Many terrestrial biosphere models depend on an understanding of the relationship between stomatal conductance and photosynthesis. However, unlike the measurement of photosynthetic parameters, such as the maximum carboxylation capacity, where standard methods (e.g.

An improved representation of the relationship between photosynthesis and stomatal conductance leads to more stable estimation of conductance parameters and improves the goodness-of-fit across diverse data sets.

Stomata play a central role in surface-atmosphere exchange by controlling the flux of water and CO between the leaf and the atmosphere. Representation of stomatal conductance (g ) is therefore an essential component of models that seek to simulate water and CO exchange in plants and ecosystems. For given environmental conditions at the leaf surface (CO concentration and vapor pressure deficit or relative humidity), models typically assume a linear relationship between g and photosynthetic CO assimilation (A).

Rapid estimation of photosynthetic leaf traits of tropical plants in diverse environmental conditions using reflectance spectroscopy.

Tropical forests are one of the main carbon sinks on Earth, but the magnitude of CO2 absorbed by tropical vegetation remains uncertain. Terrestrial biosphere models (TBMs) are commonly used to estimate the CO2 absorbed by forests, but their performance is highly sensitive to the parameterization of processes that control leaf-level CO2 exchange. Direct measurements of leaf respiratory and photosynthetic traits that determine vegetation CO2 fluxes are critical, but traditional approaches are time-consuming.

Detection of the metabolic response to drought stress using hyperspectral reflectance.

Drought is the most important limitation on crop yield. Understanding and detecting drought stress in crops is vital for improving water use efficiency through effective breeding and management. Leaf reflectance spectroscopy offers a rapid, non-destructive alternative to traditional techniques for measuring plant traits involved in a drought response.

A best-practice guide to predicting plant traits from leaf-level hyperspectral data using partial least squares regression.

Partial least squares regression (PLSR) modelling is a statistical technique for correlating datasets, and involves the fitting of a linear regression between two matrices. One application of PLSR enables leaf traits to be estimated from hyperspectral optical reflectance data, facilitating rapid, high-throughput, non-destructive plant phenotyping. This technique is of interest and importance in a wide range of contexts including crop breeding and ecosystem monitoring.

The recent and future health burden of the U.S. mobile sector apportioned by source.

Mobile sources emit particulate matter as well as precursors to particulate matter (PM) and ground-level ozone, pollutants known to adversely impact human health. This study uses source-apportionment photochemical air quality modeling to estimate the health burden (expressed as incidence) of an array of PM- and ozone-related adverse health impacts, including premature death, attributable to 17 mobile source sectors in the US in 2011 and 2025. Mobile sector-attributable air pollution contributes a substantial fraction of the overall pollution-related mortality burden in the U.

Seasonal trends in photosynthesis and leaf traits in scarlet oak.

Understanding seasonal variation in photosynthesis is important for understanding and modeling plant productivity. Here, we used shotgun sampling to examine physiological, structural and spectral leaf traits of upper canopy, sun-exposed leaves in Quercus coccinea Münchh (scarlet oak) across the growing season in order to understand seasonal trends, explore the mechanisms underpinning physiological change and investigate the impact of extrapolating measurements from a single date to the whole season. We tested the hypothesis that photosynthetic rates and capacities would peak at the summer solstice, i.

The "one-point method" for estimating maximum carboxylation capacity of photosynthesis: A cautionary tale.

The maximum carboxylation capacity of Rubisco, V , is an important photosynthetic parameter that is key to accurate estimation of carbon assimilation. The gold-standard technique for determining V is to derive V from the initial slope of an A-C curve (the response of photosynthesis, A, to intercellular CO concentration, C ). Accurate estimates of V derived from an alternative and rapid "one-point" measurement of photosynthesis could greatly accelerate data collection and model parameterization.

Monetized health benefits attributable to mobile source emission reductions across the United States in 2025.

By-products of mobile source combustion processes, such as those associated with gasoline- and diesel-powered engines, include direct emissions of particulate matter as well as precursors to particulate matter and ground-level ozone. Human exposure to fine particulate matter with an aerodynamic diameter smaller than 2.5 μm (PM) is associated with increased incidence of premature mortality and morbidity outcomes.

Vapor pressure deficit predicts epiphyte abundance across an elevational gradient in a tropical montane region.

Premise Of The Study: Tropical Montane Cloud Forests (TMCFs) are important ecosystems to study and preserve because of their high biodiversity and critical roles in local and regional ecosystem processes. TMCFs may be particularly affected by changes in climate because of the narrow bands of microclimate they occupy and the vulnerability of TMCF species to projected increases in cloud base heights and drought. A comprehensive understanding of the structure and function of TMCFs is lacking and difficult to attain because of variation in topography within and across TMCF sites.

Internalized Homonegativity, Sense of Belonging, and Depressive Symptoms Among Australian Gay Men.

Internalized homonegativity has been directly linked to depression among gay men. The aim of the study was to test whether internalized homonegativity is indirectly related to depressive symptoms via a sense of belonging to the broad gay community, gay groups, gay friends, and the general community. A sample of 246 self-identified Australian gay men, aged 18-82 years, completed the Internalized Homophobia Scale, the Psychological subscale of the Sense of Belonging Instrument, the Sense of Belonging Within Gay Communities Scale, and the Centre for Epidemiological Studies Depression Scale.

Sexual satisfaction and sexual health among university students in the United States.

Despite the World Health Organization's definition of sexual health as a state of well-being, virtually no public health research has examined sexual well-being outcomes, including sexual satisfaction. Emerging evidence suggests that sexual well-being indicators are associated with more classic measures of healthy sexual behaviors. We surveyed 2168 university students in the United States and asked them to rate their physiological and psychological satisfaction with their current sexual lives.

Virginity lost, satisfaction gained? Physiological and psychological sexual satisfaction at heterosexual debut.

Despite the literature's focus on (hetero)sexual initiation, little is known about the degree to which young people are satisfied by their first vaginal intercourse experience, let alone the factors that predict satisfaction. This study analyzed data from a cross-sectional survey of 1,986 non-Hispanic White and Black 18- to 25-year-old respondents from four university campuses. Respondents were asked to rate the degree to which their first vaginal intercourse was physiologically and psychologically satisfying.

The Language of Love?-Verbal versus Implied Consent at First Heterosexual Intercourse: Implications for Contraceptive Use.

Background: Little is known about how young people communicate about initiating intercourse.

Purpose: This study was designed to gauge the prevalence of implied versus verbal consent at first intercourse in a U.S.

Sexual attitudes and behavior at four universities: do region, race, and/or religion matter?

This study sought to ascertain any differences in sexual attitudes, levels of premarital sexual involvement, and risk-taking sexual practices of college students at four distinctly different universities: a historic Black public university; a predominately white, Southern private university with a religious heritage; a Southwestern public university; and a Midwestern public university. An anonymous questionnaire was administered to a volunteer sample of 1,915 never-married women and 1,111 never-married men in select upper and lower division classes. Numerous significant differences among campuses were found regarding sexual history, first sexual intercourse, and sexual risk-taking.

Analysis of PM2.5 using the Environmental Benefits Mapping and Analysis Program (BenMAP).

As epidemiological work from around the world continues to tie PM2.5 to serious adverse health effects, including premature mortality, the U.S.