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Title: Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Applachian forest in the USA

Abstract

Documentation of the degree and direction of effects of ozone on transpiration of canopies of mature forest trees is critically needed to model ozone effects on forest water use and growth in a warmer future climate. Patterns of sap flow in stems and soil moisture in the rooting zones of mature trees, coupled with late-season streamflow in three forested watersheds in east Tennessee, USA, were analyzed to determine relative influences of ozone and other climatic variables on canopy physiology and streamflow patterns. Statistically significant increases in whole-tree canopy conductance, depletion of soil moisture in the rooting zone, and reduced late-season streamflow in forested watersheds were detected in response to increasing ambient ozone levels. Short-term changes in canopy water use and empirically modeled streamflow patterns over a 23-yr observation period suggest that current ambient ozone exposures may exacerbate the frequency and level of negative effects of drought on forest growth and stream health.

Authors:
 [1];  [2];  [3];  [4]
  1. Oak Ridge National Laboratory (Retired)
  2. ORNL
  3. USDA Forest Service
  4. University of Calgary, ALberta, Canada
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931325
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: New Phytologist; Journal Issue: 174
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; CANOPIES; CLIMATES; DOCUMENTATION; DROUGHTS; FORESTS; MOISTURE; OZONE; PHYSIOLOGY; SOILS; TENNESSEE; TRANSPIRATION; TREES; WATER USE; WATERSHEDS

Citation Formats

McLaughlin, Samuel B., Wullschleger, Stan D, Sun, G., and Nosal, M. Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Applachian forest in the USA. United States: N. p., 2007. Web. doi:10.1111/j.1469-8137.2007.01970.x.
McLaughlin, Samuel B., Wullschleger, Stan D, Sun, G., & Nosal, M. Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Applachian forest in the USA. United States. doi:10.1111/j.1469-8137.2007.01970.x.
McLaughlin, Samuel B., Wullschleger, Stan D, Sun, G., and Nosal, M. Mon . "Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Applachian forest in the USA". United States. doi:10.1111/j.1469-8137.2007.01970.x.
@article{osti_931325,
title = {Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Applachian forest in the USA},
author = {McLaughlin, Samuel B. and Wullschleger, Stan D and Sun, G. and Nosal, M.},
abstractNote = {Documentation of the degree and direction of effects of ozone on transpiration of canopies of mature forest trees is critically needed to model ozone effects on forest water use and growth in a warmer future climate. Patterns of sap flow in stems and soil moisture in the rooting zones of mature trees, coupled with late-season streamflow in three forested watersheds in east Tennessee, USA, were analyzed to determine relative influences of ozone and other climatic variables on canopy physiology and streamflow patterns. Statistically significant increases in whole-tree canopy conductance, depletion of soil moisture in the rooting zone, and reduced late-season streamflow in forested watersheds were detected in response to increasing ambient ozone levels. Short-term changes in canopy water use and empirically modeled streamflow patterns over a 23-yr observation period suggest that current ambient ozone exposures may exacerbate the frequency and level of negative effects of drought on forest growth and stream health.},
doi = {10.1111/j.1469-8137.2007.01970.x},
journal = {New Phytologist},
number = 174,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Summary: {sm_bullet}Documentation of the degree and direction of effects of ozone on transpiration of canopies of mature forest trees is critically needed to model ozone effects on forest water use and growth in a warmer future climate. {sm_bullet}Patterns of sap flow in stems and soil moisture in the rooting zones of mature trees, coupled with late-season streamflow in three forested watersheds in east Tennessee, USA, were analyzed to determine relative influences of ozone and other climatic variables on canopy physiology and streamflow patterns.{sm_bullet}Statistically significant increases in whole-tree canopy conductance, depletion of soil moisture in the rooting zone, and reduced late-seasonmore » streamflow in forested watersheds were detected in response to increasing ambient ozone levels. {sm_bullet}Short-term changes in canopy water use and empirically modeled streamflow patterns over a 23-yr observation period suggest that current ambient ozone exposures may exacerbate the frequency and level of negative effects of drought on forest growth and stream health.« less
  • Spraying a 16 meter tall stand of red pine (Pinus resinosa Ait.) with 10/sup -3/ M phenylmercuric acetate in early June and again in mid-July resulted in the water use between June 1 and October 25 being reduced by almost 10%. It was demonstrated that this was caused by an increase in the leaf resistance with partial stomatal closure, which reduced absolute water potential in the needles by 1 to 3 bars in the middle of the day. Smaller demands were made upon the reserves of water in the bole of the tree as shown by the smaller bole contractionmore » in the treated trees. Although needle length and dry weight were unaffected by the spray, radial growth was reduced by approximately 32%. The dependence of leaf resistance on light intensity is shown, and its independence from leaf water potential discussed.« less
  • The effect of forest disturbance on C cycling has become an issue, given concerns about escalating atmospheric C content. The authors examined the effects of harvest intensity on in situ and laboratory mineral soil respiration in an East Texas bottomland hardwood forest between 6 and 22 mo after harvesting. Treatments included a clearcut, a partial cut wherein approximately 58% of the basal area was removed, and an unharvested control. The soda-lime absorption technique was used for in situ respiration (CO{sub 2} efflux) and the wet alkali method (NaOH) was used for laboratory mineral soil respiration. Soil temperature and moisture contentmore » were also measured. Harvesting significantly increased in situ respiration during most sampling periods. This effect was attributed to an increase in live root and microflora activity associated with postharvesting revegetation. In situ respiration increased exponentially (Q{sub 10} relationship) as treatment soil temperatures increased, but followed a parabolic-type pattern through the range of soil moisture measured (mean range 10.4--31.5%). Mean rates of laboratory mineral soil respiration measured during the study were unaffected by cutting treatment for most sampling sessions. Overall, the mean rate of CO{sub 2} efflux in the clearcuts was significantly higher than that in the partial cuts, which in turn was significantly higher than that in the controls. Mass balance estimates indicate that these treatment differences will have little or no long-term effect on C sequestration of these managed forests.« less
  • A large portion of terrestrial carbon (C) resides in soil organic carbon (SOC). The dynamics of this large reservoir depend on many factors, including climate. Measurements of {sup 13}C:{sup 12}C ratios, C concentrations, and C:N ratios at six forest sites in the Southern Appalachian Mountains (USA) were used to explore several hypotheses concerning the relative importance of factors that control soil organic matter (SOM) decomposition and SOC turnover. Mean {delta}{sup 13}C values increased with soil depth and decreasing C concentrations along a continuum from fresh litter inputs to more decomposed soil constituents. Data from the six forest sites, in combinationmore » with data from a literature review, indicate that the extent of change in {delta}{sup 13}C values from forest litter inputs to mineral soil (20 cm deep) is significantly associated with mean annual temperature. The findings support a conceptual model of vertical changes in forest soil {delta}{sup 13}C values, C concentrations, and C:N ratios that are interrelated through climate controls on decomposition. We hypothesize that, if other environmental factors (like soil moisture) are not limiting, then temperature and litter quality indirectly control the extent of isotopic fractionation during SOM decomposition in temperate forest ecosystems.« less
  • A large portion of terrestrial carbon (C) resides in soil organic carbon (SOC). The dynamics of this large reservoir depend on many factors, including climate. Measurements of {sup 13}C:{sup 12}C ratios, C concentrations, and C:N ratios at six forest sites in the Southern Appalachian Mountains (USA) were used to explore several hypotheses concerning the relative importance of factors that control soil organic matter (SOM) decomposition and SOC turnover. Mean {delta}{sup 13}C values increased with soil depth and decreasing C concentrations along a continuum from fresh litter inputs to more decomposed soil constituents. Data from the six forest sites, in combinationmore » with data from a literature review, indicate that the extent of change in {delta}{sup 13}C values from forest litter inputs to mineral soil is significantly associated with mean annual temperature. The findings support a conceptual model of vertical changes in forest soil {delta}{sup 13}C values, C concentrations, and C:N ratios that are interrelated through climate controls on decomposition. The authors hypothesize that, if other environmental factors are not limiting, then temperature and litter quality indirectly control the extent of isotopic fractionation during SOM decomposition in temperate forest ecosystems.« less