George R Hendrey

Queens College, CUNY | QC CUNY · School of Earth and Environmental Sciences

Terrestrial ecosystem respiration increases exponentially with temperature, constituting a positive feedback loop accelerating global warming. However, the response of ecosystem respiration to temperature strongly depends on water availability, yet where and when the water effects are important, is presently poorly constrained, introducing uncertai...

Several cotton experiments have been conducted at the University of Arizona’s Maricopa Agricultural Center from which datasets have been obtained documenting cotton responses to elevated CO2 concentrations, water supply, nitrogen fertilizer, and planting density. In particular, these experiments included FACE (free-air CO2 enrichment; CO2, water; 1...

This ERL focus collection has published 17 papers that have advanced our understanding of different dimensions of warming-induced tree mortality. Here we summarize these focus collection papers, organized by four topics related to tree mortality: pathogens, droughts/heat waves, fire/bark beetles, and teleconnections/air pollution. This focus collec...

A shift to higher temperatures has left the Mediterranean Europe and Northern Africa (MENA) region more vulnerable to drought and land degradation. We used MODIS LAI (leaf area index) and GPP (gross primary production) deficits, the differences between actual and historical-maximum values, to describe vegetation structural and functional changes an...

A shift to warmer temperatures has left the Mediterranean Europe and Northern Africa (MENA) region more vulnerable to drought and land degradation. We used LAI and GPP deficit, the difference between actual and historical-maximum values, to describe vegetation structural and functional dynamics and consequential landcover change in response to clim...

Here, we show a discernable increase in temperature variance before a glacial termination by both the Ansari-Bradley test and the moving variance methods plus introduce the idea that there is a correlation between the peak variance and peak temperature increase. The behavior of temperature variance shows potential as a useful tool in analyzing time...

We have integrated the observational capability of satellite remote sensing with plot-scale tree-ring data to upscale the evaluation of forest responses to drought. Satellite data, such as the normalized difference vegetation index (NDVI), can provide a spatially continuous measure with limited temporal coverage, while tree-ring width index (RWI) p...

How are the survival and growth of trees under severe drought affected by their size? While some studies have shown that large trees are more vulnerable to drought than smaller trees, others found that small trees are the more vulnerable. We explored the potential relationships between canopy height and forest responses to drought indicated by tree...

This study generated eddy covariance data to investigate atmospheric dynamics leeward of a small, forested hillside in upstate New York. The causes and effects of recirculation eddies were examined to support the larger goal of improving measurement of the exchange of energy, moisture, and trace gases between the terrestrial biosphere and the atmos...

Light-use efficiency (LUE) is at the core of mechanistic modeling of global gross primary production (GPP). However, most LUE estimates in global models are satellite based and coarsely measured with emphasis on environmental variables. Others are from eddy covariance towers with much greater spatial and temporal data quality and emphasis on mechan...

At biome-scale, terrestrial carbon uptake is controlled mainly by weather variability. Observational data from a global monitoring network indicate that the sensitivity of terrestrial carbon sequestration to mean annual temperature (T) breaks down at a threshold value of 16°C, above which terrestrial CO2 fluxes are controlled by dryness rather than...

Treatment and species differences in mean tree height through time. Figure S2. Mineral soil carbon pools in (a) the top 0.1 m of soil and (b) at 0.1–0.2 m in depth, relative to cumulative NPP. Figure S3. Leaf area index (LAI) through time. Table S1. Carbon pool sizes for each community and treatment. Table S2. Mineral soil C pool sizes by depth for...

Several lines of evidence suggest that the warming climate plays a vital role in driving certain types of extreme weather. The impact of warming and of extreme weather on forest carbon assimilation capacity is poorly known. Filling this knowledge gap is critical towards understanding the amount of carbon that forests can hold. Here, we used a perfe...

Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2) and tropospheric ozone (O3) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate...

Temperature sensitivity of soil respiration (Q10) is a critical parameter in carbon cycle models with important implications for climate-carbon feedbacks in the 21st century. The common assumption of a constant Q10, usually with a value of 2.0, was shown to be invalid by a previous model-data fusion study that reported biome-specific values of this...

The considerable interannual variability (IAV) (~5 PgC yr−1) observed in atmospheric CO2 is dominated by variability in terrestrial productivity. Among terrestrial ecosystems, grassland productivity IAV is greatest. Relationships between grassland productivity IAV and climate drivers are poorly explained by traditional multiple-regression approache...

The temperature sensitivity of soil respiration (Q10) is a critical parameter in carbon cycle models that has important implications for climate-carbon feedbacks in the 21st century. The common assumption of a constant Q10, usually with a value of 2.0, was shown to be invalid by a previous model-data fusion study that reported biome-specific values...

The surface and outlets of two headwater lakes acidified during the 1978, 1979, and 1980 spring snowmelt periods. The decrease in pH was accompanied by an increase in nitrate whereas the other strong acid anion, SO42−, remained relatively constant. Chemical mass-balance calculations, using data from the Integrated Lake–Watershed Acidification Study...

Three watershed–lake systems of the Integrated Lake–Watershed Acidification Study (ILWAS) were investigated to determine the effects of atmospheric deposition on the chemical compositions of oligotrophic lakes in the Adirondack Mountains of New York. Using the principles of watershed mass balance and electroneutrality of solutions, the following co...

Current forest Free Air CO(2) Enrichment (FACE) experiments are reaching completion. Therefore, it is time to define the scientific goals and priorities of future experimental facilities. In this opinion article, we discuss the following three overarching issues (i) What are the most urgent scientific questions and how can they be addressed? (ii) W...

Global warming is promoted by anthropogenic COâ emissions into the atmosphere, while at the same time it is partially mitigated by carbon sequestration by terrestrial ecosystems. However, improvement in the understanding and monitoring of below ground carbon processes is essential for evaluating strategies for carbon sequestration including quantif...

Carbon is an essential component of life and, in its organic form, plays a pivotal role in the soil's fertility, productivity, and water retention. It is an integral part of the atmospheric-terrestrial C exchange cycle mediated via photosynthesis; furthermore, it emerged recently as a new trading commodity, i.e., "carbon credits." When carefully ma...

A rising global population and demand for protein-rich diets are increasing pressure to maximize agricultural productivity. Rising atmospheric [CO(2)] is altering global temperature and precipitation patterns, which challenges agricultural productivity. While rising [CO(2)] provides a unique opportunity to increase the productivity of C(3) crops, a...

The present study analyzes features of nocturnal low-level jets observed at the Florida AmeriFlux site and their influence on CO2 flux measurements over a tall forest canopy. At that location, two categories of nocturnal flow are commonly observed, one with a strong low-level jet throughout the night and the other without. Jets of diverse speed and...

This paper documents the historical developments of free-air CO2 enrichment (FACE)systems, describes seven FACE systems that are currently studying impacts of greenhouse gases on forest ecosystems, and outlines major remaining research questions in which FACE studies can help provide insights into future forest ecosystems under elevated greenhouse...

Nocturnal eddy-covariance carbon dioxide fluxes have uncertainties arising from non-stationary atmospheric processes. Low-level jets (LLJ) are one of the prominent nocturnal boundary-layer phenomena observed over non-mountainous terrain, and are capable of generating shear and turbulence close to the ground. The influence of intermittent LLJ activi...

ABSTRACTA new technique, called Free Air Temperature Increase (FATI), was developed to artificially induce increased canopy temperature in field conditions without the use of enclosures. This acronym was chosen in analogy with FACE (Free Air CO2 Enrichment), a technique which produces elevated CO2 concentrations [CO2] in open field conditions. The...

Lolium perenne and Trifolium repens were grown in a Free Air CO2 Enrichment (FACE) system at elevated (600 μimol mol-1) and ambient (340 μmol mol-1) carbon dioxide concentrations during a whole growing season. Using a root ingrowth bag technique the extent to which CO2 enrichment influenced the growth of L, perenne and T. repens roots under two con...

Free-air CO2 enrichment (FACE) in the Duke Forest provides a whole-ecosystem arena in which to examine the response of a temperate coniferous forest to high, future levels of atmospheric CO2. At the end of 8 years of the experiment, we conclude: Photosynthetic rates by canopy foliage have increased up to 50 % over controls. Basal area increment has...

Concentrations of atmospheric CO(2) and tropospheric ozone (O(3)) are rising concurrently in the atmosphere, with potentially antagonistic effects on forest net primary production (NPP) and implications for terrestrial carbon sequestration. Using free-air CO(2) enrichment (FACE) technology, we exposed north-temperate forest communities to concentra...

Many uncertainties remain regarding how climate change will alter the structure and function of forest ecosystems. At the Aspen FACE experiment in northern Wisconsin, we are attempting to understand how an aspen/birch/maple forest ecosystem responds to long-term exposure to elevated carbon dioxide (CO2) and ozone (O3), alone and in combination, fro...

This study investigates effects of climate warming (+ 2.5°C ubove ambient) and elevated CO2 concentration (600 μmol mol−1) on the stomatal functioning and the water relations of Lolium perenne, using Free Air Temperature Increase (FATI) and Free Air CO2 Enrichment (FACE). Compared to growth at ambient temperature, whole-season temperature increase...

Monte Carlo codes are extensively used for probabilistic simulations of various physical systems. These codes are widely used in calculations of neutron and gamma ray transport in soil for radiation shielding, soil activation by neutrons, well logging industry, and in simulations of complex nuclear gauges for in soil measurements. However, these ca...

Our need for a non-destructive, precise, and rapid determination of the soil's elemental composition poses special challenges because of the complexity of the soil matrix and lack of instrumentation for such belowground measurements. Although the availability of such instrumentation would significantly promote our understanding of subsurface proces...

We compared the value of using a digital signal processing unit for gamma-ray spectroscopy with that of an analog one for in situ measurements of gamma-rays generated by inelastic neutron scattering reactions with soil elements. A large cylindrical NaI(Tl) scintillation detector, 15.24 cm high by 15.24 cm diameter was used to measure carbon (C) and...

Stably stratified nocturnal boundary layers are often associated with Low Level Jets (LLJ) formed due to either one or a combination of mechanisms such as inertial oscillations, horizontal temperature gradient associated with weather patterns or sloping terrain, land and sea breezes and advective accelerations. LLJs appear to play an important role...

The International Panel of Climate Change (IPCC) has concluded that the greenhouse gases, carbon dioxide (CO2) and tropospheric ozone (O3), are increasing concomitantly globally. Little is known about the effect of these interacting gases on growth, survival, and productivity of forest ecosystems. In this study we assess the effects of three succes...

To determine whether elevated CO2 reduces or exacerbates the detrimental effects of O3 on aspen (Populus tremuloides Michx.). Aspen clones 216 and 271 (O3 tolerant), and 259 (O3 sensitive) were exposed to ambient levels of CO2 and O3 or elevated levels of CO2, O3, or CO2 + O3 in the FACTS II (Aspen FACE) experiment, and physiological and molecular...

The impacts of elevated atmospheric CO 2 and/or O 3 have been examined over 4 years using an open‐air exposure system in an aggrading northern temperate forest containing two different functional groups (the indeterminate, pioneer, O 3 ‐sensitive species Trembling Aspen, Populus tremuloides and Paper Birch, Betula papyrifera , and the determinate,...

Human activity causes increasing background concentrations of the greenhouse gases CO2 and O3. Increased levels of CO2 can be found in all terrestrial ecosystems. Damaging O3 concentrations currently occur over 29% of the world's temperate and subpolar forests but are predicted to affect fully 60% by 2100 (ref. 3). Although individual effects of CO...

Leaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides trees in a developing canopy under free-air CO 2 enrichment in Wis-consin, USA. After 2 years of growth, the trees averaged 1·5 and 1·6 m tall under ambient and elevated CO 2 , respectively , at the beginning of the study period in 1999. They grew to 2...

Rising atmospheric CO2 may stimulate future forest productivity, possibly increasing carbon storage in terrestrial ecosystems, but how tropospheric ozone will modify this response is unknown. Because of the importance of fine roots to the belowground C cycle, we monitored fine-root biomass and associated C fluxes in regenerating stands of trembling...

Northern mid-latitude forests are a large terrestrial carbon sink. Ignoring nutrient limitations, large increases in carbon sequestration from carbon dioxide (CO2) fertilization are expected in these forests. Yet, forests are usually relegated to sites of moderate to poor fertility, where tree growth is often limited by nutrient supply, in particul...

Human actions are causing declines in plant biodiversity, increases in atmospheric CO2 concentrations and increases in nitrogen deposition; however, the interactive effects of these factors on ecosystem processes are unknown. Reduced biodiversity has raised numerous concerns, including the possibility that ecosystem functioning may be affected nega...

The Intergovernmental Panel of Climate Change (IPCC) has concluded that the greenhouse gases carbon dioxide (CO2) and tropospheric ozone (O3) are increasing concomitantly globally. Little is known about the effect of these interacting gases on growth, survival, and productivity of forest ecosystems. In this study we assess the effects of three succ...

To determine whether elevated CO2 reduces or exacerbates the detrimental effects of O3 on aspen (Populus tremuloides Michx.). aspen clones 216 and 271 (O3 tolerant), and 259 (O3 sensitive) were exposed to ambient levels of CO2 and O3 or elevated levels of CO2, O3, or CO2 + O3 in the FACTS II (Aspen FACE) experiment, and physiological and molecular...

Atmospheric chemical composition affects foliar chemical composition, which in turn influences the dynamics of both herbivory and decomposition in ecosystems. We assessed the independent and interactive effects of CO2 and O3 fumigation on foliar chemistry of quaking aspen (Populus tremuloides) and paper birch (Betula papyrifera) at a Free-Air CO2 E...

Free-air carbon dioxide enrichment (FACE) provides a realistic, cost-effective method for evaluating the effects of supra-ambient CO2 concentrations on growth, development, yield, and water use of agricultural crops and natural ecosystems with very few of the problems normally associated with glasshouse or chamber type research. There are no walls...

Soil carbon sequestration is a whole new area of energy related research that provides a fundamentally new approach for dealing with climate change resulting from the substantial increase in CO₂ concentration in the atmosphere. Carbon sequestration in soil is recognized to play a major role in allowing fossil fuels to remain a vital comp...

Prediction of global energy use in this century suggest a continued increase in carbon emissions and rising concentrations of carbon dioxide (CO 2) in the atmosphere. This represents a serious environmental problem and contributes significantly to greenhouse gases that affect global warming. Terrestrial ecosystems are a huge natural biological scru...

Long-term airport weather observations, calibrated by on-site measurements, were used to create a footprint climatology for the Forest Atmosphere Carbon Dioxide Transfer and Storage-1 (FACTS-1) site in the Duke Forest, NC. The footprint was centered over each 30-m diameter control ring to estimate potential contamination from four CO2-enriched ring...

Arid and semiarid climates comprise roughly 40% of the earth’s terrestrial surface. Deserts are predicted to be extremely responsive to global change because they are stressful environments where small absolute changes in water availability or use represent large proportional changes. Water and carbon dioxide fluxes are inherently coupled in plant...

The concentration of atmospheric carbon dioxide was increased by 200 microliters per liter in a forest plantation, where competition between organisms, resource limitations, and environmental stresses may modulate biotic responses. After 2 years the growth rate of the dominant pine trees increased by about 26 percent relative to trees under ambient...

A free-air CO2 enrichment (FACE) system was designed to permit the experimental exposure of tall vegetation such as stands of forest trees to elevated atmospheric CO2 concentrations ([CO2]a) without enclosures that alter tree microenvironment. We describe a prototype FACE system currently in operation in forest plots in a maturing loblolly pine (Pi...

Carbon sequestration in soil plays a critical role in helping the world meet the challenges of climate change by reducing the atmospheric carbon dioxide. At present soil carbon is measured by taking core samples and involves extensive laboratory work. We propose a novel non-destructive in situ method for carbon analysis using the Inelastic Neutron...

Previous studies of photosynthetic acclimation to elevated CO2 have focused on the most recently expanded, sunlit leaves in the canopy. We examined acclimation in a vertical profile of leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO2 partial pressure of 55 Pa within a replicated field experiment using f...

A maturing loblolly pine (Pinus taeda L.) forest was exposed to elevated COâ in the natural environment in a perturbation study conducted over three seasons using the free-air COâ enrichment (FACE) technique. At the time measurements were begun in this study, the pine canopy was comprised entirely of foliage which had developed under elevated COâ c...

In a FACE experiment, one year old alder, ash, beech, and oak seedlings were planted together in tubs containing calcareous sandy alluvial soil with or without a slow release NPK-fertilizer, and exposed to ambient and elevated CO2 concentrations (360 and 600 μl mol−1) for 20 weeks. In addition to the fertilizer, all tubs received 15N-ammonium nitra...

In the Swiss grassland FACE experiment, we measured the effect of elevated CO2 on the shoot necromass production and quality of Lolium perenne in 1995. Dead stubble of reproductive tillers and dead leaf sheaths were the main components of necromass. Elevated CO2 did not significantly change the amount and the nitro