A highly controversial issue in global biogeochemistry is the regulation of terrestrial carbon (C... more A highly controversial issue in global biogeochemistry is the regulation of terrestrial carbon (C) sequestration by soil nitrogen (N) availability. This controversy translates into great uncertainty in predicting future global terrestrial C sequestration. We propose a new framework that ...
Although outdoor water use is thought to constitute a large fraction of urban water budgets in se... more Although outdoor water use is thought to constitute a large fraction of urban water budgets in semi-arid regions, the amount of water actually used by irrigated urban vegetation is not well quantified. In southern California, urban forests are very diverse, and general relationships between water relations parameters would simplify predictions of tree water use for a wide range of species. In this study, we measured sap flux and xylem vulnerability to cavitation of 16 commonly planted irrigated tree species in the Los Angeles Basin, in order to address the following questions: (1) Is stomatal sensitivity to atmospheric vapor pressure deficit systematically different between ring-porous and diffuse-porous trees, as has been previously reported? (2) Is stomatal sensitivity within species consistent across different sites? (3) Can stomatal sensitivity of irrigated trees be predicted based on their vulnerability to cavitation? Contrary to our expectations, we found that ring-porous and ...
Background/Question/Methods Trees in urban ecosystems provide valuable ecosystem services. Howeve... more Background/Question/Methods Trees in urban ecosystems provide valuable ecosystem services. However, in arid regions which are not naturally forested, the irrigation required to sustain urban trees constitutes an ecosystem disservice. A better understanding of the factors that control urban tree water use, growth, water use efficiency and drought resistance is necessary to maximize ecosystem services and minimize costs. To address this issue, a variety of physiological measurements were made (including sapflux, isotope, leaf level photosynthesis, growth rate, stem vulnerability to cavitation, water potential, and leaf nutrient measurements) spanning more than 35 species in the Los Angeles Basin. These data were used in combination with tree inventory data to examine patterns in urban tree and forest function. We wished to answer the questions: What is the relative importance of climate, species composition, and management in determining plant function? How do patterns of tree functio...
Where does all the water go? The ecohydrology of Los Angeles. Diane E. Pataki 1 , Chris Boone 2 ,... more Where does all the water go? The ecohydrology of Los Angeles. Diane E. Pataki 1 , Chris Boone 2 , Terri S. Hogue 3 , G. Darrel Jenerette 4 , Heather R. McCarthy 5 , Joseph P. McFadden 6 , Caroline Mini 3 and Stephanie Pincetl ...
In arid regions which are not naturally forested, urban trees are sustained through the redistrib... more In arid regions which are not naturally forested, urban trees are sustained through the redistribution of water resources as irrigation. Assessments of outdoor water use in Southwestern US cities have shown that not only is 30-75% of residential water use expended on outdoor landscapes, but that irrigation is frequently in excess of estimated plant demand. Thus, there is a need to understand the factors which influence the magnitude and variability of water use of urban trees. A complicating factor in assessing urban tree water use is the widely recognized heterogeneity of urban environments. Human choices and decision-making result in a landscape with significant variability in water and nutrient inputs, microclimate, biotic inputs and vegetation composition. In order to quantify urban tree water use and explain variation in water use resulting from variability in resource availability and species composition, we have conducted a combination of sapflux, growth and isotopic studies ...
Background/Question/Methods Coast redwood, a popular landscape tree in Southern California, is ex... more Background/Question/Methods Coast redwood, a popular landscape tree in Southern California, is exposed to altered environmental conditions compared to its native habitat, where precipitation and fog drip are essential sources of water. In the semi-arid climate of the Los Angeles Basin, where few tree species grow naturally, cultivated coast redwood trees are irrigated, yet exposed to unusually high atmospheric vapor pressure deficit (VPD). As coast redwood trees are reported to have poor stomatal regulation in their native habitat, high VPD may cause a loss of xylem hydraulic conductivity due to air embolism. Observations that irrigated coast redwood in the Los Angeles Basin are difficult to grow led to the following questions: Is VPD the major driver of sap flow rate in this species? Does weak stomatal regulation lead to excessive air embolism of xylem, and water stress? If so, what are the relative roles of atmospheric and soil water stress? To address these questions, we measured...
Under elevated CO2, the enhancement in the amount of carbon (C) sequestered in woody biomass of f... more Under elevated CO2, the enhancement in the amount of carbon (C) sequestered in woody biomass of forests is controlled by availability of other resources that influence growth, such as nutrients and water. At the Duke Forest FACE site, a large growth response of woody tissue in a loblolly pine forest was transient, settling after three years at a marginal gain.
Orthonormal wavelet transformation (OWT) is a computationally efficient technique for quantifying... more Orthonormal wavelet transformation (OWT) is a computationally efficient technique for quantifying underlying frequencies in nonstationary and gap-infested time series, such as eddy-covariance-measured net ecosystem exchange of CO2 (NEE). We employed OWT to analyze the frequency characteristics of synchronously measured and modeled NEE at adjacent pine (PP) and hardwood (HW) ecosystems. Wavelet cospectral analysis showed that NEE at PP was more correlated to light and vapor pressure deficit at the daily time scale, and NEE at HW was more correlated to leaf area index (LAI) and temperature, especially soil temperature, at seasonal time scales. Models were required to disentangle the impacts of environmental drivers on the components of NEE, ecosystem carbon assimilation (Ac) and ecosystem respiration (RE). Sensitivity analyses revealed that using air temperature rather than soil temperature in RE models improved the modeled wavelet spectral frequency response on time scales longer tha...
Proceedings of The National Academy of Sciences, 2006
Net primary productivity (NPP) is enhanced under future atmospheric [CO₂] in temperate forests re... more Net primary productivity (NPP) is enhanced under future atmospheric [CO₂] in temperate forests representing a broad range of productivity. Yet questions remain in regard to how elevated [CO₂]-induced NPP enhancement may be affected by climatic variations and limiting nutrient resources, as well as how this additional production is distributed among carbon (C) pools of different longevities. Using 10 years of
A highly controversial issue in global biogeochemistry is the regulation of terrestrial carbon (C... more A highly controversial issue in global biogeochemistry is the regulation of terrestrial carbon (C) sequestration by soil nitrogen (N) availability. This controversy translates into great uncertainty in predicting future global terrestrial C sequestration. We propose a new framework that ...
Although outdoor water use is thought to constitute a large fraction of urban water budgets in se... more Although outdoor water use is thought to constitute a large fraction of urban water budgets in semi-arid regions, the amount of water actually used by irrigated urban vegetation is not well quantified. In southern California, urban forests are very diverse, and general relationships between water relations parameters would simplify predictions of tree water use for a wide range of species. In this study, we measured sap flux and xylem vulnerability to cavitation of 16 commonly planted irrigated tree species in the Los Angeles Basin, in order to address the following questions: (1) Is stomatal sensitivity to atmospheric vapor pressure deficit systematically different between ring-porous and diffuse-porous trees, as has been previously reported? (2) Is stomatal sensitivity within species consistent across different sites? (3) Can stomatal sensitivity of irrigated trees be predicted based on their vulnerability to cavitation? Contrary to our expectations, we found that ring-porous and ...
Background/Question/Methods Trees in urban ecosystems provide valuable ecosystem services. Howeve... more Background/Question/Methods Trees in urban ecosystems provide valuable ecosystem services. However, in arid regions which are not naturally forested, the irrigation required to sustain urban trees constitutes an ecosystem disservice. A better understanding of the factors that control urban tree water use, growth, water use efficiency and drought resistance is necessary to maximize ecosystem services and minimize costs. To address this issue, a variety of physiological measurements were made (including sapflux, isotope, leaf level photosynthesis, growth rate, stem vulnerability to cavitation, water potential, and leaf nutrient measurements) spanning more than 35 species in the Los Angeles Basin. These data were used in combination with tree inventory data to examine patterns in urban tree and forest function. We wished to answer the questions: What is the relative importance of climate, species composition, and management in determining plant function? How do patterns of tree functio...
Where does all the water go? The ecohydrology of Los Angeles. Diane E. Pataki 1 , Chris Boone 2 ,... more Where does all the water go? The ecohydrology of Los Angeles. Diane E. Pataki 1 , Chris Boone 2 , Terri S. Hogue 3 , G. Darrel Jenerette 4 , Heather R. McCarthy 5 , Joseph P. McFadden 6 , Caroline Mini 3 and Stephanie Pincetl ...
In arid regions which are not naturally forested, urban trees are sustained through the redistrib... more In arid regions which are not naturally forested, urban trees are sustained through the redistribution of water resources as irrigation. Assessments of outdoor water use in Southwestern US cities have shown that not only is 30-75% of residential water use expended on outdoor landscapes, but that irrigation is frequently in excess of estimated plant demand. Thus, there is a need to understand the factors which influence the magnitude and variability of water use of urban trees. A complicating factor in assessing urban tree water use is the widely recognized heterogeneity of urban environments. Human choices and decision-making result in a landscape with significant variability in water and nutrient inputs, microclimate, biotic inputs and vegetation composition. In order to quantify urban tree water use and explain variation in water use resulting from variability in resource availability and species composition, we have conducted a combination of sapflux, growth and isotopic studies ...
Background/Question/Methods Coast redwood, a popular landscape tree in Southern California, is ex... more Background/Question/Methods Coast redwood, a popular landscape tree in Southern California, is exposed to altered environmental conditions compared to its native habitat, where precipitation and fog drip are essential sources of water. In the semi-arid climate of the Los Angeles Basin, where few tree species grow naturally, cultivated coast redwood trees are irrigated, yet exposed to unusually high atmospheric vapor pressure deficit (VPD). As coast redwood trees are reported to have poor stomatal regulation in their native habitat, high VPD may cause a loss of xylem hydraulic conductivity due to air embolism. Observations that irrigated coast redwood in the Los Angeles Basin are difficult to grow led to the following questions: Is VPD the major driver of sap flow rate in this species? Does weak stomatal regulation lead to excessive air embolism of xylem, and water stress? If so, what are the relative roles of atmospheric and soil water stress? To address these questions, we measured...
Under elevated CO2, the enhancement in the amount of carbon (C) sequestered in woody biomass of f... more Under elevated CO2, the enhancement in the amount of carbon (C) sequestered in woody biomass of forests is controlled by availability of other resources that influence growth, such as nutrients and water. At the Duke Forest FACE site, a large growth response of woody tissue in a loblolly pine forest was transient, settling after three years at a marginal gain.
Orthonormal wavelet transformation (OWT) is a computationally efficient technique for quantifying... more Orthonormal wavelet transformation (OWT) is a computationally efficient technique for quantifying underlying frequencies in nonstationary and gap-infested time series, such as eddy-covariance-measured net ecosystem exchange of CO2 (NEE). We employed OWT to analyze the frequency characteristics of synchronously measured and modeled NEE at adjacent pine (PP) and hardwood (HW) ecosystems. Wavelet cospectral analysis showed that NEE at PP was more correlated to light and vapor pressure deficit at the daily time scale, and NEE at HW was more correlated to leaf area index (LAI) and temperature, especially soil temperature, at seasonal time scales. Models were required to disentangle the impacts of environmental drivers on the components of NEE, ecosystem carbon assimilation (Ac) and ecosystem respiration (RE). Sensitivity analyses revealed that using air temperature rather than soil temperature in RE models improved the modeled wavelet spectral frequency response on time scales longer tha...
Proceedings of The National Academy of Sciences, 2006
Net primary productivity (NPP) is enhanced under future atmospheric [CO₂] in temperate forests re... more Net primary productivity (NPP) is enhanced under future atmospheric [CO₂] in temperate forests representing a broad range of productivity. Yet questions remain in regard to how elevated [CO₂]-induced NPP enhancement may be affected by climatic variations and limiting nutrient resources, as well as how this additional production is distributed among carbon (C) pools of different longevities. Using 10 years of
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Papers by Heather McCarthy