Mary A HeskelMacalester College · Department of Biology
Mary A Heskel
Ph.D.
About
42
Publications
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Introduction
Additional affiliations
November 2014 - June 2018
June 2014 - November 2014
May 2013 - June 2014
Education
September 2008 - May 2013
June 2006 - May 2008
September 2002 - May 2006
Publications
Publications (42)
Leaf dark respiration (Rdark ) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of Rdark and associated leaf traits. Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. M...
Net ecosystem exchange (NEE) represents the difference between carbon assimilated through photosynthesis, or gross primary productivity (GPP), and carbon released via ecosystem respiration (ER). NEE, measured via eddy covariance and chamber techniques, must be partitioned into these fluxes to accurately describe and understand the carbon dynamics o...
![Figure 3: Shoot dark respiration at 20 °C [R, panel (a)], leaf fresh...](profile/Mary-Heskel/publication/260131601/figure/fig3/AS:267847259652104@1440871171081/Shoot-dark-respiration-at-20C-R-panel-a-leaf-fresh-mass-per-unit-leaf-area-FA_Q320.jpg)
Despite concern about the status of carbon (C) in the Arctic tundra, there is currently little information on how plant respiration varies in response to environmental change in this region. We quantified the impact of long-term nitrogen (N) and phosphorus (P) treatments and greenhouse warming on the short-term temperature (T) response and sensitiv...
Photosynthetic traits suggest that shade tolerance may explain the contrasting success of two conifer taxa, Podocarpaceae and Pinaceae, in tropical forests. Needle‐leaved species from Pinus (Pinaceae) are generally absent from tropical forests, while Pinus krempfii, a flat‐leaved pine, and numerous flat‐leaved Podocarpaceae are abundant. Respiratio...
Leaf-level gas exchange data support the mechanistic understanding of plant fluxes of carbon and water. These fluxes inform our understanding of ecosystem function, are an important constraint on parameterization of terrestrial biosphere models, are necessary to understand the response of plants to global environmental change, and are integral to e...
Two simplifying hypotheses have been proposed for whole‐plant respiration. One links respiration to photosynthesis; the other to biomass. Using a first‐principles carbon balance model with a prescribed live woody biomass turnover, applied at a forest research site where multidecadal measurements are available for comparison, we show that if turnove...
Warming-induced nutrient enrichment in the Arctic may lead to shifts in leaf-level physiological properties and processes with potential consequences for plant community dynamics and ecosystem function. To explore the physiological responses of Arctic tundra vegetation to increasing nutrient availability, we examined how a set of leaf nutrient and...
Two simplifying hypotheses have been proposed for whole-plant respiration. One links respiration to photosynthesis; the other to biomass. Using a first-principles carbon balance model with a prescribed live woody biomass turnover, we show that if turnover is fast, the accumulation of respiring biomass is low and respiration depends primarily on pho...
1.Nitrogen (N) and phosphorus (P) are essential nutrients for plant metabolism and their availability often limits primary productivity. Whereas the effects of N‐availability on photosynthetic capacity are well established, we still know relatively little about the effects of P availability at a foliar level, especially in P‐limited tropical forest...
Uncertainty in the estimation of daytime ecosystem carbon cycling due to the light inhibition of leaf respiration and photorespiration, and how these small fluxes vary through the growing season in the field, remains a confounding element in calculations of gross primary productivity and ecosystem respiration. Our study focuses on how phenology, sh...
The forests of the northeastern US are globally, one of the fastest growing terrestrial carbon sinks due to historical declines in large-scale agriculture, timber harvesting and fire disturbance. However, shifting range distributions of tree species with warming air temperatures are altering forest community composition and carbon dynamics. Here, w...
Changes in plant phenology affect the carbon flux of terrestrial forest ecosystems due to the link between the growing season length and vegetation productivity. Digital camera imagery, which can be acquired frequently, has been used to monitor seasonal and annual changes in forest canopy phenology and track critical phenological events. However, q...
Land-atmosphere exchanges influence atmospheric CO 2. Emphasis has been on describing photosynthetic CO 2 uptake, but less on respiration losses. New global datasets describe upper canopy dark respiration (R d) and temperature dependencies. This allows character-isation of baseline R d , instantaneous temperature responses and longer-term thermal a...
Temperature is a crucial factor in determining the rates of ecosystem processes, e.g. leaf respiration (R) − the flux of plant respired CO2 from leaves to the atmosphere. Generally, R increases exponentially with temperature and formulations such as the Arrhenius equation are widely used in earth system models. However, experimental observations ha...
Contents I. II. III. IV. V. VI. VII. VIII. References SUMMARY: It has been 75 yr since leaf respiratory metabolism in the light (day respiration) was identified as a low-flux metabolic pathway that accompanies photosynthesis. In principle, it provides carbon backbones for nitrogen assimilation and evolves CO2 and thus impacts on plant carbon and ni...
Rapid environmental change at high latitudes is predicted to greatly alter the diversity, structure, and function of plant communities, resulting in changes in the pools and fluxes of nutrients. In Arctic tundra, increased nitrogen (N) and phosphorus (P) availability accompanying warming is known to impact plant diversity and ecosystem function; ho...
High-temperature tolerance in plants is important in a warming world, with extreme heat-waves predicted to increase in frequency and duration, potentially leading to lethal heating of leaves. Global patterns of high-temperature tolerance are documented in animals, but generally not plants, limiting our ability to assess risks associated with climat...
How leaf respiration (Rd) is represented in leading terrestrial biosphere models (TBMs ) is reviewed, followed by an overview of how emerging global datasets provide opportunities to improve parameterization of leaf Rd in large-scale models. We first outline how TBMs have historically accounted for variations in respiratory CO2 release in mature le...
Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosy...
The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite consider- able scientific attention in recent decades, the overall response...
Using an empirical approach, we report that the slope of the short-term log-transformed leaf respiration (R)– temperature (T) curves declines with increasing leaf T in a manner that is uniform across biomes (1); the results have utility for modeling carbon fluxes in terrestrial biosphere models (TBMs). The use of an empirical approach reflects the...
Plant respiration constitutes a massive carbon flux to the atmosphere,
and a major control on the evolution of the global carbon cycle. It
therefore has the potential to modulate levels of climate change due
to the human burning of fossil fuels. Neither current physiological nor
terrestrial biosphere models adequately describe its short-term temper...
Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe its short-term temper...
Phenotypic plasticity is ubiquitous and generally regarded as a key mechanism for enabling organisms to survive in the face of environmental change. Because no organism is infinitely or ideally plastic, theory suggests that there must be limits (for example, the lack of ability to produce an optimal trait) to the evolution of phenotypic plasticity,...
Abstract Understanding the evolution of reaction norms remains a major challenge in ecology and evolution. Investigating evolutionary divergence in reaction norm shapes between populations and closely related species is one approach to providing insights. Here we use a meta-analytic approach to compare divergence in reaction norms of closely relate...
Direct measurements of foliar carbon exchange through the growing season in Arctic species are limited, despite the need for accurate estimates of photosynthesis and respiration to characterise carbon cycling in the tundra. We examined seasonal variation in foliar photosynthesis and respiration (measured at 20 C) in two field-grown tundra species,...
Direct and indirect effects of warming are increasingly modifying the carbon-rich vegetation and soils of the Arctic tundra, with important implications for the terrestrial carbon cycle. Understanding the biological and environmental influences on the processes that regulate foliar carbon cycling in tundra species is essential for predicting the fu...
This article comments on: Short‐term effects of CO2 and O2 on citrate metabolism in illuminated leaves
Laboratory studies indicate that, in response to environmental conditions, plants modulate respiratory electron partitioning between the 'energy-wasteful' alternative pathway (AP) and the 'energy-conserving' cytochrome pathway (CP). Field data, however, are scarce. Here we investigate how 20-yr field manipulations simulating global change affected...
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Premise of the study:
Consequences of global climate change are detectable in the historically nitrogen- and phosphorus-limited Arctic tundra landscape and have implications for the terrestrial carbon cycle. Warmer temperatures and elevated soil nutrient availability associated with increased microbial activity may influence rates...
Background/Question/Methods
Climate change is altering the terrestrial carbon cycle in Artic tundra through the direct and indirect effects of warming, including the lengthening of the growing season due to earlier snowmelt. To predict future responses of this vast carbon reservoir to environmental change, we must understand how the underlying bio...
Projects
Projects (8)
Day respiration or mitochondrial respiration in the absence of photorespiration (Rlight or Rday) is poorly understood, both in terms of underlying mechanisms as well as responses to changing environmental variables. However, it is an important variable in the photosynthesis biochemical model of Farquhar et al. (1980) and Rlight does not always have similar responses as Rdark.
