ABSTRACT The effect of an elevated partial pressure of CO2 (pCO2) on carbohydrate concentrations ... more ABSTRACT The effect of an elevated partial pressure of CO2 (pCO2) on carbohydrate concentrations in source leaves and pseudo-stems (stubble) of Lolium perenne L. (perennial ryegrass) during regrowth was studied in a regularly defoliated grass sward in the field. The free air carbon dioxide enrichment (FACE) technology enabled natural environmental conditions to be provided. Two levels of nitrogen (N) supply were used to modulate potential plant growth. Carbohydrate concentrations in source leaves were increased at elevated pCO2, particularly at low N supply. Elevated leaf carbohydrate concentrations were related to an increased structural carbon (C) to N ratio and thus reflected an increased C availability together with a N-dependent sink limitation. Immediately after defoliation, apparent assimilate export rates (differences in the carbohydrate concentrations of young source leaves measured in the evening and on the following morning) showed a greater increase at elevated pCO2 than at ambient pCO2; however, replenishment of carbohydrate reserves was not accelerated. Distinct, treatment-dependent carbohydrate concentrations in pseudo-stems suggested an increasing degree of C-sink limitation from the treatment at ambient pCO2 with high N supply to that at elevated pCO2 with low N supply. During two growing seasons, no evidence of a substantial change in the response of the carbohydrate source in L. perenne to elevated pCO2 was found. Our results support the view that the response of L. perenne to elevated pCO2 is restricted by a C-sink limitation, which is particularly severe at low N supply.
Species composition of fish communities in northern Wisconsin lakes: Relation to pH. JG Wiener, P... more Species composition of fish communities in northern Wisconsin lakes: Relation to pH. JG Wiener, PJ Rago, JM Eilers 1984. Fish communities in circumneutral Wisconsin lakes contained significantly more species than did those in acidic lakes (pH 5.1-6.0). ...
As embedded communication networks pervade widely fielded safety-critical distributed systems, it... more As embedded communication networks pervade widely fielded safety-critical distributed systems, it is important to understand their robustness. Middleware fault injection offers advantages in flexibility and cost over adding specialized fault injecting network nodes. The research goal is accelerated testing of an automated vehicle system with respect to transient communication network faults.
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This research was performed under the auspices of the U.S. Department of Energy under Contract No. DE-AC02-76CH00016.
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereofl nor any of their employees, nor any of their contractors, subcontractors, or their employees makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usehlness of any information, apparatus, product or process disclosed, or represents that its use would not iniiinge privately owned rights. Reference herein to any s p d c commercial product, process, or service by trade name, trademark mandacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency, contractor, or subcontractor thereof. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor aiiy agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, mommend;ltion, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Temperature sensitivity of soil respiration (Q 10) is a critical parameter in carbon cycle models... more Temperature sensitivity of soil respiration (Q 10) 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 Q 10 , 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 parameter. We extend the previous analysis by demonstrating that these biome-level values of Q 10 also are a function of dryness (R 2 = 0.54). When tundra and cultivated lands are excluded, the correlation is much stronger (R 2 = 0.92). Therefore dryness is the primary driver for variability in respiration-temperature sensitivity in forest and grassland ecosystems. This finding has important implications for the response of the terrestrial carbon cycle to climate change, as it implies that the increasing dryness would potentially accelerate the respiration temperature sensitivity feedback.
Free-air CO{sub 2} enrichment (FACE) was used to expose an intact lobolly pine forest ecosystem t... more Free-air CO{sub 2} enrichment (FACE) was used to expose an intact lobolly pine forest ecosystem to elevated CO{sub 2}. Leaf conductance and canopy water flux measurements along with A{sub net}-C{sub i} curves were used to evaluate physiological responses of the dominant trees to elevated CO{sub 2}. CO{sub 2}-exposed trees showed minor (<7%) but significant reductions in sap flux density compared to trees under ambient CO{sub 2} conditions, but only when air saturation vapor pressure deficit (VPD) was low. Short-term (minutes) direct stomatal responses to elevated CO{sub 2} were also relatively weak. We observed no evidence of adjustments in stomatal conductance in current-year foliage grown under elevated CO{sub 2} for 80 days compared to foliage grown under ambient CO{sub 2}. Leaf net photosynthetic rate at 550 {mu}mol mol{sup {minus}1} CO{sub 2} was enhanced by more than 50% compared to the rate at ambient CO{sub 2}(350 {mu}mol mol{sup {minus}1}). Thus, leaf water-use-efficiency of loblolly pine at elevated CO{sub 2} was enhanced primarily by direct responses of photosynthesis to CO{sub 2} and was not mediated by stomata.
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or b... more All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. M aintaining and increasing the organic matter in soils adds to its fertility and retention of water, and, hence, increases crop production. Carbon transport and retention in soil also is an integral part of the atmospheric-terrestrial C-exchange cycle mediated via photosynthesis. It was recognized that the terrestrial sequestration of C plays an important mitigating role in moderating the rise in global temperature thought to be caused by anthropogenic greenhouse gases that trap heat in the atmosphere and ultimately lead to changes in global climate patterns (Hasselmann, 1997). The rate of such change expected during the next 100 yr will be unprecedented in human history. Since the beginning of the 20th century, the mean surface temperature of the earth has increased by about 0.5°C (about 1.0°F). There is strong evidence that most of the warming during the last 50 yr is due to human activities that have altered the chemical composition of the atmosphere through the buildup of greenhouse gases, in particular by adding large amounts of CO 2 (United Nations Environment Programme, 2003, p. 3-7). The dramatic increase in atmospheric CO 2 concentrations from approximately 0.025% (w/w) in the pre-Industrial Revolution period, to about 0.036% (w/w) at present (Lal et al., 1998) is at the center of the climate debate about global warming. The main sources of CO 2 emissions are attributed to burning fossil fuels and biomass, and to changes in land use, deforestation, and soil-management practices (Bhatti et al., 2006). Less than half of the emissions has remained in the
At biome-scale, terrestrial carbon uptake is controlled mainly by weather variability. Observatio... more 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 temperature. Here we show that since 1948 warming climate has moved the 16°C T latitudinal belt poleward. Land surface area with T > 16°C and now subject to dryness control rather than temperature as the regulator of carbon uptake has increased by 6% and is expected to increase by at least another 8% by 2050. Most of the land area subjected to this warming is arid or semiarid with ecosystems that are highly vulnerable to drought and land degradation. In areas now dryness-controlled, net carbon uptake is ~27% lower than in areas in which both temperature and dryness (T < 16°C) regulate plant productivity. This warming-induced extensi...
Several lines of evidence suggest that the warming climate plays a vital role in driving certain ... more 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
Leaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides... more 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 Wisconsin, 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•6 and 2•9 m, respectively, by the end of the 1999 growing season. Daily integrated photon flux from cloudfree days (PPFD day,sat) around the lowermost branches was 16•8 ± ± ± ± 0•8 and 8•7 ± ± ± ± 0•2% of values at the top for the ambient and elevated CO 2 canopies, respectively. Elevated CO 2 significantly decreased leaf N on a mass, but not on an area, basis. N per unit leaf area was related linearly to PPFD day,sat throughout the canopies, and elevated CO 2 did not affect that relationship. Leaf Ps light-response curves responded differently to elevated CO 2 , depending upon canopy position. Elevated CO 2 increased Ps sat only in the upper (unshaded) canopy, whereas characteristics that would favour photosynthesis in shade were unaffected by elevated CO 2. Consequently, estimated daily integrated Ps on cloudfree days (Ps day,sat) was stimulated by elevated CO 2 only in the upper canopy. Ps day,sat of the lowermost branches was actually lower with elevated CO 2 because of the darker light environment. The lack of CO 2 stimulation at the midand lower canopy was probably related to significant down-regulation of photosynthetic capacity; there was no down-regulation of Ps in the upper canopy. The relationship between Ps day,sat and leaf N indicated that N was not optimally allocated within the canopy in a manner that would maximize whole-canopy Ps or photosynthetic N use efficiency. Elevated CO 2 had no effect on the optimization of canopy N allocation.
Soil carbon sequestration is a whole new area of energy related research that provides a fundamen... more 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 CO 2 concentration in the atmosphere. Carbon sequestration in soil is recognized to play a major role in allowing fossil fuels to remain a vital component of the national energy mix. At present soil carbon is measured by taking core samples and involves extensive laboratory work. We propose a novel nondestructive in situ method for carbon analysis using the Inelastic Neutron Scattering (INS) (n,n'() reaction. The feasibility of detecting carbon in soil was demonstrated using a clinical in vivo body composition facility, located in the Medical Department at BNL. A D-T generator, operated at 55 kV, irradiated 12"x12"x14" aluminum boxes filled with 70 lb. clean sand and mixtures of sand with 2%, 5% and 10% carbon powder by weight. The spectra were acquired for 1 hr and subsequently the carbon peaks were analyzed using the trapezoidal method for peak extraction. The results demonstrate that the proposed method is suitable for carbon analysis in soil, and it should allow sequential sampling of soil carbon within a soil volume of about 0.5 m 3 with an error of about 1% or less. It is expected that, with final optimization, changes of about 1% in the soil carbon content would be observable with sufficient confidence levels.
ABSTRACT The effect of an elevated partial pressure of CO2 (pCO2) on carbohydrate concentrations ... more ABSTRACT The effect of an elevated partial pressure of CO2 (pCO2) on carbohydrate concentrations in source leaves and pseudo-stems (stubble) of Lolium perenne L. (perennial ryegrass) during regrowth was studied in a regularly defoliated grass sward in the field. The free air carbon dioxide enrichment (FACE) technology enabled natural environmental conditions to be provided. Two levels of nitrogen (N) supply were used to modulate potential plant growth. Carbohydrate concentrations in source leaves were increased at elevated pCO2, particularly at low N supply. Elevated leaf carbohydrate concentrations were related to an increased structural carbon (C) to N ratio and thus reflected an increased C availability together with a N-dependent sink limitation. Immediately after defoliation, apparent assimilate export rates (differences in the carbohydrate concentrations of young source leaves measured in the evening and on the following morning) showed a greater increase at elevated pCO2 than at ambient pCO2; however, replenishment of carbohydrate reserves was not accelerated. Distinct, treatment-dependent carbohydrate concentrations in pseudo-stems suggested an increasing degree of C-sink limitation from the treatment at ambient pCO2 with high N supply to that at elevated pCO2 with low N supply. During two growing seasons, no evidence of a substantial change in the response of the carbohydrate source in L. perenne to elevated pCO2 was found. Our results support the view that the response of L. perenne to elevated pCO2 is restricted by a C-sink limitation, which is particularly severe at low N supply.
Species composition of fish communities in northern Wisconsin lakes: Relation to pH. JG Wiener, P... more Species composition of fish communities in northern Wisconsin lakes: Relation to pH. JG Wiener, PJ Rago, JM Eilers 1984. Fish communities in circumneutral Wisconsin lakes contained significantly more species than did those in acidic lakes (pH 5.1-6.0). ...
As embedded communication networks pervade widely fielded safety-critical distributed systems, it... more As embedded communication networks pervade widely fielded safety-critical distributed systems, it is important to understand their robustness. Middleware fault injection offers advantages in flexibility and cost over adding specialized fault injecting network nodes. The research goal is accelerated testing of an automated vehicle system with respect to transient communication network faults.
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This research was performed under the auspices of the U.S. Department of Energy under Contract No. DE-AC02-76CH00016.
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereofl nor any of their employees, nor any of their contractors, subcontractors, or their employees makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usehlness of any information, apparatus, product or process disclosed, or represents that its use would not iniiinge privately owned rights. Reference herein to any s p d c commercial product, process, or service by trade name, trademark mandacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency, contractor, or subcontractor thereof. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor aiiy agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, mommend;ltion, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Temperature sensitivity of soil respiration (Q 10) is a critical parameter in carbon cycle models... more Temperature sensitivity of soil respiration (Q 10) 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 Q 10 , 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 parameter. We extend the previous analysis by demonstrating that these biome-level values of Q 10 also are a function of dryness (R 2 = 0.54). When tundra and cultivated lands are excluded, the correlation is much stronger (R 2 = 0.92). Therefore dryness is the primary driver for variability in respiration-temperature sensitivity in forest and grassland ecosystems. This finding has important implications for the response of the terrestrial carbon cycle to climate change, as it implies that the increasing dryness would potentially accelerate the respiration temperature sensitivity feedback.
Free-air CO{sub 2} enrichment (FACE) was used to expose an intact lobolly pine forest ecosystem t... more Free-air CO{sub 2} enrichment (FACE) was used to expose an intact lobolly pine forest ecosystem to elevated CO{sub 2}. Leaf conductance and canopy water flux measurements along with A{sub net}-C{sub i} curves were used to evaluate physiological responses of the dominant trees to elevated CO{sub 2}. CO{sub 2}-exposed trees showed minor (<7%) but significant reductions in sap flux density compared to trees under ambient CO{sub 2} conditions, but only when air saturation vapor pressure deficit (VPD) was low. Short-term (minutes) direct stomatal responses to elevated CO{sub 2} were also relatively weak. We observed no evidence of adjustments in stomatal conductance in current-year foliage grown under elevated CO{sub 2} for 80 days compared to foliage grown under ambient CO{sub 2}. Leaf net photosynthetic rate at 550 {mu}mol mol{sup {minus}1} CO{sub 2} was enhanced by more than 50% compared to the rate at ambient CO{sub 2}(350 {mu}mol mol{sup {minus}1}). Thus, leaf water-use-efficiency of loblolly pine at elevated CO{sub 2} was enhanced primarily by direct responses of photosynthesis to CO{sub 2} and was not mediated by stomata.
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or b... more All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. M aintaining and increasing the organic matter in soils adds to its fertility and retention of water, and, hence, increases crop production. Carbon transport and retention in soil also is an integral part of the atmospheric-terrestrial C-exchange cycle mediated via photosynthesis. It was recognized that the terrestrial sequestration of C plays an important mitigating role in moderating the rise in global temperature thought to be caused by anthropogenic greenhouse gases that trap heat in the atmosphere and ultimately lead to changes in global climate patterns (Hasselmann, 1997). The rate of such change expected during the next 100 yr will be unprecedented in human history. Since the beginning of the 20th century, the mean surface temperature of the earth has increased by about 0.5°C (about 1.0°F). There is strong evidence that most of the warming during the last 50 yr is due to human activities that have altered the chemical composition of the atmosphere through the buildup of greenhouse gases, in particular by adding large amounts of CO 2 (United Nations Environment Programme, 2003, p. 3-7). The dramatic increase in atmospheric CO 2 concentrations from approximately 0.025% (w/w) in the pre-Industrial Revolution period, to about 0.036% (w/w) at present (Lal et al., 1998) is at the center of the climate debate about global warming. The main sources of CO 2 emissions are attributed to burning fossil fuels and biomass, and to changes in land use, deforestation, and soil-management practices (Bhatti et al., 2006). Less than half of the emissions has remained in the
At biome-scale, terrestrial carbon uptake is controlled mainly by weather variability. Observatio... more 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 temperature. Here we show that since 1948 warming climate has moved the 16°C T latitudinal belt poleward. Land surface area with T > 16°C and now subject to dryness control rather than temperature as the regulator of carbon uptake has increased by 6% and is expected to increase by at least another 8% by 2050. Most of the land area subjected to this warming is arid or semiarid with ecosystems that are highly vulnerable to drought and land degradation. In areas now dryness-controlled, net carbon uptake is ~27% lower than in areas in which both temperature and dryness (T < 16°C) regulate plant productivity. This warming-induced extensi...
Several lines of evidence suggest that the warming climate plays a vital role in driving certain ... more 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
Leaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides... more 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 Wisconsin, 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•6 and 2•9 m, respectively, by the end of the 1999 growing season. Daily integrated photon flux from cloudfree days (PPFD day,sat) around the lowermost branches was 16•8 ± ± ± ± 0•8 and 8•7 ± ± ± ± 0•2% of values at the top for the ambient and elevated CO 2 canopies, respectively. Elevated CO 2 significantly decreased leaf N on a mass, but not on an area, basis. N per unit leaf area was related linearly to PPFD day,sat throughout the canopies, and elevated CO 2 did not affect that relationship. Leaf Ps light-response curves responded differently to elevated CO 2 , depending upon canopy position. Elevated CO 2 increased Ps sat only in the upper (unshaded) canopy, whereas characteristics that would favour photosynthesis in shade were unaffected by elevated CO 2. Consequently, estimated daily integrated Ps on cloudfree days (Ps day,sat) was stimulated by elevated CO 2 only in the upper canopy. Ps day,sat of the lowermost branches was actually lower with elevated CO 2 because of the darker light environment. The lack of CO 2 stimulation at the midand lower canopy was probably related to significant down-regulation of photosynthetic capacity; there was no down-regulation of Ps in the upper canopy. The relationship between Ps day,sat and leaf N indicated that N was not optimally allocated within the canopy in a manner that would maximize whole-canopy Ps or photosynthetic N use efficiency. Elevated CO 2 had no effect on the optimization of canopy N allocation.
Soil carbon sequestration is a whole new area of energy related research that provides a fundamen... more 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 CO 2 concentration in the atmosphere. Carbon sequestration in soil is recognized to play a major role in allowing fossil fuels to remain a vital component of the national energy mix. At present soil carbon is measured by taking core samples and involves extensive laboratory work. We propose a novel nondestructive in situ method for carbon analysis using the Inelastic Neutron Scattering (INS) (n,n'() reaction. The feasibility of detecting carbon in soil was demonstrated using a clinical in vivo body composition facility, located in the Medical Department at BNL. A D-T generator, operated at 55 kV, irradiated 12"x12"x14" aluminum boxes filled with 70 lb. clean sand and mixtures of sand with 2%, 5% and 10% carbon powder by weight. The spectra were acquired for 1 hr and subsequently the carbon peaks were analyzed using the trapezoidal method for peak extraction. The results demonstrate that the proposed method is suitable for carbon analysis in soil, and it should allow sequential sampling of soil carbon within a soil volume of about 0.5 m 3 with an error of about 1% or less. It is expected that, with final optimization, changes of about 1% in the soil carbon content would be observable with sufficient confidence levels.
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