Peter Harley

• PhD
• NSF National Center for Atmospheric Research

Colorado was one of the first US states to legalize the industrial-scale cultivation of Cannabis spp. for recreational purposes. In March 2018, there were 609 indoor Cannabis cultivation facilities (CCFs) in operation in Denver County with a recorded 550,000 mature plants (higher than 8 inches) under cultivation at any given time. It is known that...

The legal commercialization of cannabis for recreational and medical use has effectively created a new and almost unregulated cultivation industry. In 2018, within the Denver County limits, there were more than 600 registered cannabis cultivation facilities (CCFs) for recreational and medical use, mostly housed in commercial warehouses. Measurement...

The legal commercialization of cannabis for recreational and medical use has effectively created a new and almost unregulated cultivation industry. In 2018, within the Denver County limits, there were more than 600 registered cannabis cultivation facilities (CCFs) for recreational and medical use, mostly housed in commercial warehouses. Measurement...

Xylem vulnerability to cavitation and hydraulic efficiency are directly linked to fine‐scale bordered pit features in water‐conducting cells of vascular plants. However, it is unclear how pit characteristics influence water transport and carbon economy in tropical species. The primary aim of this study was to evaluate functional implications of cha...

The legal commercialization of Cannabis for recreational and medical use in certain US states has effectively created a new and nearly unregulated cultivation industry. Within the city limits of Denver, Colorado, there are now more than 600 registered Cannabis spp. cultivation facilities (CCFs) for recreational and medical uses, each containing tho...

There is a spectacular variability in trichome types and densities and trichome metabolites across species, but the functional implications of this variability in protection from atmospheric oxidative stresses remain poorly understood. The aim of the present study was to evaluate the possible protective role of glandular and non-glandular trichomes...

Acute ozone exposure triggers major emissions of volatile organic compounds (VOC), but quantitatively, it is unclear how different ozone doses alter the start and the total amount of these emissions, and the induction rate of different stress volatiles. It is also unclear whether priming (i.e., pre-exposure to lower O3 concentrations) can modify th...

Light use efficiency (LUE) plays a vital role in determination of crop biomass and yield. Important com- ponents of LUE, i.e. canopy structure, nitrogen distribution, photosynthetic capacity and CO2 diffusion conductance were investigated in paddy rice grown under low, normal and high supplemental nitrogen (0, 115, and 180 kg N h...

New particle formation (NPF) is an important atmospheric phenomenon. During an NPF event, particles first form by nucleation and then grow further in size. The growth step is crucial because it controls the number of particles that can become cloud condensation nuclei. Among various physical and chemical processes contributing to particle growth, c...

Despite the known biochemical production of a range of aromatic compounds by plants and the presence of benzenoids in floral scents, the emissions of only a few benzenoid compounds have been reported from the biosphere to the atmosphere. Here, using evidence from measurements at aircraft, ecosystem, tree, branch and leaf scales, with complementary...

Considerable amounts and varieties of biogenic volatile organic compounds (BVOCs) are exchanged between vegetation and the surrounding air. These BVOCs play key ecological and atmospheric roles that must be adequately represented for accurately modeling the coupled biosphere-atmosphere-climate earth system. One key uncertainty in existing models is...

New particle formation (NPF) is an important atmospheric phenomenon. During a NPF event, molecular clusters first form by nucleation and then grow further by condensation of vapors. The growth step is crucial because it controls the number of particles that can become cloud condensation nuclei. In order to better understand the influence of biogeni...

Terpenoid emissions from ponderosa pine (Pinus ponderosa subsp. scopulorum) were measured in Colorado, USA over two growing seasons to evaluate the role of incident light, needle temperature, and stomatal conductance in controlling emissions of 2-methyl-3-buten-2-ol (MBO) and several monoterpenes. MBO was the dominant daylight terpenoid emission, c...

The Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen (BEACHON) project seeks to understand the feedbacks and inter-relationships between hydrology, biogenic emissions, carbon assimilation, aerosol properties, clouds and associated feedbacks within water-limited ecosystems. The Manitou Experimental Forest Obser...

Organic peroxy (RO2) and hydroperoxy (HO2) radicals are key intermediates in the photochemical processes that generate ozone, secondary organic aerosol and reactive nitrogen reservoirs throughout the troposphere. In regions with ample biogenic hydrocarbons, the richness and complexity of peroxy radical chemistry presents a significant challenge to...

Biogenic volatile organic compound (BVOC) emissions are widely modeled as inputs to atmospheric chemistry simulations. However, BVOC may interact with cellular structures and neighboring leaves in a complex manner during volatile diffusion from the sites of release to leaf boundary layer and during turbulent transport to the atmospheric boundary la...

Total OH reactivity was measured during the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen-Southern Rocky Mountain 2008 field campaign (BEACHON-SRM08) held at Manitou Experimental Forest (MEF) in Colorado USA in August, 2008. The averaged total OH reactivity was 6.7 s−1, smaller than that measured in urban...

The Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen (BEACHON) project seeks to understand the feedbacks and inter-relationships between hydrology, biogenic emissions, carbon assimilation, aerosol properties, clouds and associated feedbacks within water-limited ecosystems. The Manitou Experimental Forest Obser...

Organic peroxy (RO2) and hydroperoxy (HO2) radicals are key intermediates in the photochemical processes that generate ozone, secondary organic aerosol and reactive nitrogen reservoirs throughout the troposphere. In regions with ample biogenic hydrocarbons, the richness and complexity of peroxy radical chemistry presents a significant challenge to...

We present the first eddy covariance flux measurements of volatile organic compounds (VOCs) using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) above a ponderosa pine forest in Colorado, USA. The high mass resolution of the PTR-TOF-MS enabled the identification of chemical sum formulas. During a 30 day measurement period...

Isoprene emission from plants accounts for about one third of annual global volatile organic compound emissions. The largest source of isoprene for the global atmosphere is the Amazon Basin. This study aimed to identify and quantify the isoprene emission and photosynthesis at different levels of light intensity and leaf temperature, in three phenol...

Conifers, especially pines, produce and store under pressure monoterpene-laden resin in canals located throughout the plant. When the plants are damaged and resin canals punctured, the resin is exuded and the monoterpenes are released into the atmosphere, a process that has been shown to influence ecosystem-level monoterpene emissions. Less attenti...

We present the first eddy covariance flux measurements of volatile organic compounds (VOCs) using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) above a ponderosa pine forest in Colorado, USA. The high mass resolution of the PTR-TOF-MS enabled the identification of chemical sum formulas. During a 30 day measurement period...

•We present a multidisciplinary biosphere-atmosphere field campaign.•We measured a gradient from semi-desertic shrublands to wet temperate forests.•A wide range of instruments and vertical platforms were used.•Land cover strongly influenced emissions of BVOCs and gas, energy and water exchange.•Vegetation has strong potential for feed-back to atmos...

Plants emit more than 30,000 different volatile organic compounds and the extent to which stomata exert control over the emissions of these compounds varies widely. Each of these compounds has unique physico-chemical characteristics, including volatility that characterizes the partitioning between water/air and water/lipid phases. For different vol...

The emissions of VOCs, including monoterpenes (MTs) and 2-methyl-3-buten-2-ol (MBO), from ponderosa pine can be important contributors to the regional production of ozone and secondary organic aerosols in the Western United States. The goal of this study was to better characterize the influences of biotic and abiotic factors on the emissions of the...

MEGAN and other biogenic emission models need to represent the major processes controlling biogenic volatile organic compound (BVOC) fluxes and provide accurate parameterizations in order to accurately estimate regional to global distributions of BVOC emissions. The development of these models previously relied on enclosure measurements to identify...

In 2010 leaf level gas exchange and VOC fluxes from switchgrass and corn grown at the CSU horticultural farm in Ft Collins (CO) were measured using a PTR-MS coupled to a modified Li6400 cuvette system. Both species are C4 plants with corn currently being the dominant biofuel crop in the USA whilst switchgrass being a promising candidate for cellulo...

We report the first observations of formaldehyde (HCHO) flux measured via eddy covariance, as well as HCHO concentrations and gradients, as observed by the Madison Fiber Laser-Induced Fluorescence Instrument during the BEACHON-ROCS 2010 campaign in a rural, Ponderosa Pine forest northwest of Colorado Springs, CO. A median noon upward flux of ~80 mu...

We report the first observations of formaldehyde (HCHO) flux measured via eddy covariance, as well as HCHO concentrations and gradients, as observed by the Madison Fiber Laser-Induced Fluorescence Instrument during the BEACHON-ROCS 2010 campaign in a rural, Ponderosa Pine forest northwest of Colorado Springs, CO. A median noon upward flux of ~80 μg...

The capacity for volatile isoprenoid production under standardized environmental conditions at a certain time (ES, the emission factor) is a key characteristic in constructing isoprenoid emission inventories. However, there is large variation in published ES estimates for any given species partly driven by dynamic modifications in ES due to acclima...

Ambient surface level concentrations of isoprene (C₅H₈) were measured in the major forest regions located south of Shanghai, China. Because there is a large coverage of broad-leaved trees in this region, high concentrations of isoprene were measured, ranging from 1 to 6 ppbv. A regional dynamical/chemical model (WRF-Chem) is a...

The capacity for volatile isoprenoid production under standardized environmental conditions (ES), the emission factor) is a key characteristic in constructing isoprenoid emission inventories. However, there is large variation in published ES estimates for any given species, and this variation leads to significant uncertainties in emission predictio...

Biogenic volatile organic compounds (BVOCs) are produced by plants and include monoterpenes, sesquiterpenes, and their oxygenated derivatives. These BVOCs are one of the principal factors influencing the oxidative capacity of the atmosphere in forested regions, and impact both ozone concentration and secondary organic aerosol formation. Under unstr...

The partitioning of evapotranspiration between evaporation from bare soil and transpiration by vegetation is not adequately represented in land surface models coupled to atmospheric models. In this work we present measurements of stable water vapor isotopes (deltaD and delta18O) in Manitou Experimental Forest. At an elevation of approximately 2,400...

Given the magnitude and spatial extent of recent forest mortality in the western U.S. there is a pressing need to improve representation of such influences on the exchange of energy, water, biogeochemical and momentum fluxes in land-atmosphere parameterizations coupled to weather and climate models. In this talk we present observational data and mo...

Unexplored BVOC and their oxidation products have been suspected as a main source of uncertainty for understanding tropospheric photochemical chemistry, controlling ozone and secondary organic aerosol formation on regional and global scales. For this reason, many studies have assessed the abundance of unexplored BVOC. One of the most effective ways...

Volatiles Versus Vegetation Plants act as both global sources and sinks of highly reactive volatile organic compounds (VOCs). Models typically treat the uptake and degradation of these compounds as if they are mostly unreactive, like other more commonly studied biogenic gases such as ozone. A study by Karl et al. (p. 816 , published online 21 Octob...

During two field campaigns (OP3 and ACES), which ran in Borneo in 2008, we measured large emissions of estragole (methyl chavicol; IUPAC systematic name 1-allyl-4-methoxybenzene; CAS number 140-67-0) in ambient air above oil palm canopies (0.81 mg m−2 h−1 and 3.2 ppbv for mean midday fluxes and mixing ratios respectively) and subsequently from flow...

Large quantities of volatile organic compounds (VOC) enter the atmosphere. The annual production of VOC (600 -2000 TgC/a) likely exceeds that of methane and CO (~500 TgC/a each). Together these gases fuel tropospheric chemistry. Oxidation of VOC leads to the formation of aerosol (Hallquist et al., 2009) via complex organic chemistry (e.g. Atkinson...

Pyruvic acid, central to leaf carbon metabolism, is a precursor of many volatile organic compounds (VOCs) that impact air quality and climate. Although the pathways involved in the production of isoprenoids are well-known, those of several oxygenated VOCs remain uncertain. We present concentration and flux measurements of pyruvic acid and other VOC...

During two field campaigns (OP3 and ACES), which ran in Borneo in 2008, we measured large emissions of estragole (methyl chavicol; IUPAC systematic name 1-allyl-4-methoxybenzene; CAS number 140-67-0) in ambient air above oil palm canopies (0.81 mg m−2 h−1 and 3.2 ppbv for mean midday fluxes and mixing ratios, respectively) and subsequently from flo...

The hydroxyl radical (OH) is well known to play a central role in initiating the oxidation of a number of atmospheric species. Measurement of total OH reactivity is important not only to understand mechanisms of oxidant formation in the troposphere but also to estimate the total amount of trace gas species, especially volatile organic compounds (VO...

A number of field, modeling and laboratory studies have reported that the presence of unidentified reactive organic volatile compounds (VOC) from biogenic sources potentially limit our understanding of photochemistry and secondary organic aerosol production. Discussion on the origin of unidentified VOC to date can be summarized in two sources-direc...

Two proton-transfer-reaction mass spectrometry systems were deployed at the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen-Southern Rocky Mountain 2008 field campaign (BEACHON-SRM08; July to September 2008) at the Manitou Forest observatory in a Ponderosa pine woodland near Woodland Park, Colorado USA to s...

Two proton-transfer-reaction mass spectrometry systems were deployed at the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen-Southern Rocky Mountain 2008 field campaign (BEACHON-SRM08; July to September 2008) at the Manitou Forest observatory in a Ponderosa pine woodland near Woodland Park, Colorado USA to s...

Although the emission of acetaldehyde from plants into the atmosphere following biotic and abiotic stresses may significantly impact air quality and climate, its metabolic origin(s) remains uncertain. We investigated the pathway(s) responsible for the production of acetaldehyde in plants by studying variations in the stable carbon isotope compositi...

Biogenic emission of sesquiterpene (SQT) and oxygenated SQT (OSQT) were measured from the dominant vegetation in a desert shrubland and urban area (Las Vegas, Nevada, U.S.A.), and at temperate forest sites at Niwot Ridge, Colorado, U.S.A., Tomakomai, Hokkaido, Japan and Tumbarumba, New South Wales, Australia. Additional measurements were conducted...

We deployed two proton-transfer-reaction mass spectrometry instruments (PTR-MS, IONICON ANALYTIK) for ambient and branch enclosure measurements at the Manitou Experimental Forest, located in the Southern Rocky Mountain area as a part of the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen (BEACHON) field cam...

Tropical landscapes have the most dynamic and yet most poorly understood biogeochemistry on earth. Biogenic Volatile Organic Compound (BVOC) emission models (e.g., Guenther et al. 1995) estimate that the tropics, which contain about 40% of the global land mass and account for about 60% of the global annual net primary productivity (NPP), contribute...

We quantified fine scale sources and sinks of gas phase acetaldehyde in two forested ecosystems in the US. During the daytime, the upper canopy behaved as a net source while at lower heights, reduced emission rates or net uptake were observed. At night, uptake generally predominated thoughout the canopies. Net ecosystem emission rates were inversel...

We quantified fine scale sources and sinks of gas phase acetaldehyde in two forested ecosystems in the US. During the daytime, the upper canopy behaved as a net source while at lower heights, reduced emission rates or net uptake were observed. At night, uptake generally predominated thoughout the canopies. Net ecosystem emission rates were inversel...

Methanol is found throughout the troposphere, with average concentrations second only to methane among atmospheric hydrocarbons. Proposed global methanol budgets are highly uncertain, but all agree that at least 60% of the total source arises from the terrestrial biosphere and primary emissions from plants. However, the magnitude of these emissions...

Diurnal branch-level emission rates of biogenic volatile organic compounds (BVOC) including isoprene, monoterpenes (MT), and sesquiterpenes (SQT) were determined at the University of Michigan Biological Station for the tree species red maple (Acer rubrum), red oak (Quercus rubra), paper birch (Betula papyrifera), white pine (Pinus strobus), and big...

Biogenic volatile organic compound (BVOC) emissions were studied using vegetation enclosure experiments. Particular emphasis was given to sesquiterpene compounds (SQT), although monoterpenes (MT) were also characterized. SQT were detected in emissions from seven (out of eight) pine species that were examined. Thirteen SQT compounds were identified;...

A new facility has been developed to investigate the formation of new particles from the oxidation of volatile organic compounds emitted from vegetation. The facility consists of a biogenic emissions enclosure, an aerosol growth chamber, and the associated instrumentation. Using the facility, new particle formation events have been induced through...

Reactive gases and aerosols are produced by terrestrial ecosystems, processed within plant canopies, and can then be emitted into the above-canopy atmosphere. Estimates of the above-canopy fluxes are needed for quantitative earth system studies and assessments of past, present and future air quality and climate. The Model of Emissions of Gases and...

In order to parametrize a leaf submodel of a canopy level gas-exchange model, a series of photosynthesis and stomatal conductance measurements were made on leaves of white oak (Quercus alba L.) and red maple (Acer rubrum L.) in a mature deciduous forest near Oak Ridge, TN. Gas-exchange characteristics of sun leaves growing at the top of a 30 m cano...

Isoprene is the primary biogenic hydrocarbon emitted from temperate deciduous forest ecosystems. The effects of varying photon flux density (PFD) and nitrogen growth regimes on rates of isoprene emission and net photosynthesis in potted aspen and white oak trees are reported. In both aspen and oak trees, whether rates were expressed on a leaf area...

Cotton plants were grown in CO2-controlled growth chambers in atmospheres of either 35 or 65 Pa CO2. A widely accepted model of C3 leaf photosynthesis was parameterized for leaves from both CO2 treatments using non-linear least squares regression techniques, but in order to achieve reasonable fits, it was necessary to include a phosphate limitation...

Gas exchange characteristics of leaves of Vitis vinifera L. cvs Tinta Amarela and Periquita, two grapevine cultivars grown in distinct climatic regions of Portugal, were studied under natural and controlled conditions. Daily time courses of gas exchange were measured on both a hot, sunny day and a cooler, partly cloudy day. Responses of net photosy...

Increasing surface levels of UV-B resulting from stratospheric ozone reduction directly affect tropospheric photochemistry. There may also be indirect tropospheric effects due to changes in emission of organic compounds from vegetation. We treated woody and herbaceous isoprene-emitting species in the field with supplemental UV-B simulating 30% ozon...

Leaf and woody plant tissue (Pinus ponderosa, Eucalyptus saligna, Quercus gambelli, Saccharum officinarum and Oriza sativa) were heated from 30 to 300 degrees C and volatile organic compound (VOC) emissions were identified and quantified. Major VOC emissions were mostly oxygenated and included acetic acid, furylaldehyde, acetol, pyrazine, terpenes,...

The transition between wintertime net carbon loss and springtime net carbon assimilation has an important role in controlling the annual rate of carbon uptake in coniferous forest ecosystems. We studied the contributions of springtime carbon assimilation to the total annual rate of carbon uptake and the processes involved in the winter-to-spring tr...

Using new in-situ field observations of the most abundant oxygenated VOCs (methanol, acetaldehyde, acetone, C3/C4 carbonyls, MVK+MAC and acetic acid) we were able to constrain emission and deposition patterns above and within a loblolly pine (Pinus taeda) plantation with a sweetgum (Liquidambar styraciflua) understory. Canopy scale measurements sho...

The Ozarks Isoprene Experiment (OZIE) was conducted in July 1998 in Missouri, Illinois, Indiana, and Oklahoma. OZIE was designed to investigate the presumed strong isoprene emission rates from the Missouri Ozarks, where there is a high density of oak trees that are efficient isoprene emitters. Ground, balloon, and aircraft measurements were taken o...

Previous studies have found dramatic seasonal changes in both leaf level and whole system isoprene emission rates from tropical rainforests. Modeling these variations is crucial since the isoprene produced by tropical ecosystems accounts for a large fraction of the global budget. These studies found that basal isoprene emission rates increased by a...

Leaf isoprene emission rates (Fiso) were studied in 2-year old trees of live oak (Quercus virginiana Mill.) during two drying–rewatering cycles. During the first drying–rewatering cycle, photosynthesis (A) and stomatal conductance (gs) decreased by 92%(±7%) and 91%(±8%), respectively, while Fiso remained essentially constant for 8 days of treatment...

As part of the Large Scale Biosphere–Atmosphere Experiment in Amazônia (LBA), we have developed a bottom‐up approach for estimating canopy‐scale fluxes of isoprene. Estimating isoprene fluxes for a given forest ecosystem requires knowledge of foliar biomass, segregated by species, and the isoprene emission characteristics of the individual tree spe...

Organic emissions from vegetation are important inputs for global atmospheric chemistry models that simulate the processes controlling oxidant, CO, aerosol, and organic acid evolution, as well as the contribution of reactive carbon to global carbon cycles and budgets. Regional air quality policy decisions, which have large environmental and socio-e...

The Chemical Emission, Loss, Transformation and Interactions within Canopies (CELTIC) study was conducted from June 30 to July 25, 2003 at the Duke Forest FACTS-1 Site. The primary objective of CELTIC is to improve our ability to predict regional air quality (e.g., particulates and ozone) and climate through a quantitative understanding of the proc...

Isoprene is the most abundant biogenic hydrocarbon released from vegetation and plays a key role in the chemistry of the lower atmosphere. Isoprene is produced and emitted by many plant species, yet the reason plants produce this seemingly wasteful carbon compound is still in debate in the plant physiology community. It has been proposed that isopr...

Improved vegetation distribution and emission data for Africa south of the equator were developed for the Southern African Regional Science Initiative ( SAFARI 2000) and were combined with biogenic volatile organic compound (BVOC) emission measurements to estimate BVOC emissions for the southern African region. The BVOCs are estimated to total 80 T...

We evaluated the hypothesis that CO2 uptake by a subalpine, coniferous forest is limited by cool temperature during the growing season. Using the eddy covariance approach we conducted observations of net ecosystem CO2 exchange (NEE) across two growing seasons. When pooled for the entire growing season during both years, light-saturated net ecosyste...

As part of the EXPRESSO program (EXPeriment for the REgional Sources and Sinks of Oxidants), biosphere-atmosphere exchanges of trace gases were investigated in a ground-based forest site of the Republic of Congo. Experiments were carried out in March and November-December 1996. A 60-meter walkup tower was erected in an undisturbed mixed tropical fo...

Biogenic VOC have an important role in determining the chemical composition of atmosphere. As a result, these compounds are important for visibility, biogeochemical cycling, climate and radiative forcing, and the health of the biosphere. Tropical landscapes are estimated to release about 80% of total global biogenic VOC emissions but have been inve...

[1] In February 2001, as part of the Southern African Regional Science Initiative (SAFARI 2000), isoprene fluxes were measured for 8 days using the relaxed eddy accumulation technique from a 21-m tower in a Combretum-Acacia savanna in Kruger National Park, 13 km from Skukuza, RSA. Despite warm and sunny conditions, midday isoprene concentrations we...

Biogenic volatile organic compound (BVOC) emissions were measured in a mopane woodland near Maun, Botswana in January-February 2001 as part of SAFARI 2000. This landscape is comprised of more than 95% of one woody plant species, Colophospermum mopane (Caesalpinaceae). Mopane woodlands extend over a broad area of southern Africa. A leaf cuvette tech...

Oxygenated VOC fluxes were investigated in leaves of deciduous trees and grasses, and needles of conifers, using a temperature-controlled leaf cuvette and a proton transfer reaction mass spectrometer. Two alcohols, 2-methyl-3-buten-2-ol (MBO) and methanol, emitted by these plants, illustrate two contrasting patterns of oxygenated VOC emissions. MBO...

The temperature dependence of C3 photosynthesis is known to vary with growth environment and with species. In an attempt to quantify this variability, a commonly used biochemically based photosynthesis model was parameterized from 19 gas exchange studies on tree and crop species. The parameter values obtained described the shape and amplitude of th...

The light, temperature and stomatal conductance dependencies of volatile organic compound (VOC) emissions from ten plant species commonly found in the Mediterranean region were studied using a fully controlled leaf cuvette in the laboratory. At standard conditions of temperature and light (30degreesC and 1000 mumol m(-2) s(-1) PAR), low emitting sp...

We studied net ecosystem CO2 exchange (NEE) dynamics in a high-elevation, subalpine forest in Colorado, USA, over a two-year period. Annual carbon sequestration for the forest was 6.71 mol C m−2 (80.5 g C m−2) for the year between November 1, 1998 and October 31, 1999, and 4.80 mol C m−2 (57.6 g C m−2) for the year between November 1, 1999 and Octo...

Canopy scale emissions of isoprene and monoterpenes from Amazonian rainforest were measured by eddy covariance and eddy accumulation techniques. The peak mixing ratios at about 10 m above the canopy occurred in the afternoon and were typically about 90 pptv of α-pinene and 4–5 ppbv of isoprene. α-pinene was the most abundant monoterpene in the air...

We studied net ecosystem CO2 exchange (NEE) dynamics in a high-elevation, subalpine forest in Colorado, USA, over a two-year period. Fundamental features of forest structure and turbulence are reported, including an estimated leaf area index of 4.2 m2 m-2, canopy gap fraction of 17%, canopy height of 11 m, displacement height of 7.6 m, and roughnes...

Three years of continuous measurements of net ecosystem exchange of CO2 over a high elevation coniferous forest at Niwot Ridge, Colorado have indicated the importance of wintertime snowpack to annual carbon uptake by the ecosystem. The snowpack provides the key trigger for initiation of plant photosynthesis by providing water via the beginning of t...

Volatile organic carbon (VOC) emissions from vegetation account for approximately 95% of the global VOC budget, with the tropical regions producing the largest amounts. Emission estimates have been modeled for many regions including the tropical regions of Africa, but there are few emissions data for the African region south of the equator. During...

Isoprene emission capacity measurements are presented from 18 North American oak (Quercus) species and species from six other genera previously found to emit significant quantities of isoprene. Sampling was conducted at physiographically diverse locations in North Carolina, Central California, and Northern Oregon. Emissions from several sun leaves...

Isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperature dependent. The influence of long-term variations in growth temperature on isoprene emission rates from bur oak (Quercus macrocarpa) leaves was investigated under controlled environmental conditions. Trees were installed in a growth chamber and exposed to a series of daytim...

The magnitudes, distributions, controlling processes and uncertainties associated with North American natural emissions of oxidant precursors are reviewed. Natural emissions are responsible for a major portion of the compounds, including non-methane volatile organic compounds (NMVOC), carbon monoxide (CO) and nitric oxide (NO), that determine tropo...

Many plants emit isoprene, a hydrocarbon that has important influences on atmospheric chemistry. Pathogens may affect isoprene fluxes, both through damage to plant tissue and by changing the abundance of isoprene-emitting species. Live oaks (Quercus fusiformis (Small) Sarg. and Q. virginiana Mill) are major emitters of isoprene in the southern Unit...

This paper presents an overview of the Experiment for Regional Sources and Sinks of Oxidents (EXPRESSO) including the objectives of the project, a detailed description of the characteristics of the experimental region and of field instrumentation deployed, and a summary of the main results of all components of the experiment. EXPRESSO is an interna...

A global three-dimensional (3-D) chemistry and transport model was used to demonstrate that a factor of 2 decrease in isoprene and monoterpene emissions results in significant (10-30%) changes in predicted concentration distributions of compounds such as OH, MPAN, NOx, H2O2, O-3, and CO. Isoprene and monoterpenes were predicted to have a particular...

We present a physiological model of isoprene (2-methyl-3-butadiene) Emission which considers the cost for isoprene synthesis, and the production of reductive equivalents in reactions of photosynthetic electron transport for Liquidambar styraciflua L, and for North American and European deciduous temperate Quercus species, In the model,,ve different...