Carbon exchange of an old-growth eastern hemlock (Tsuga canadensis) forest in central New England.

Carbon (C) exchange of an approximately 200-year-old eastern hemlock (Tsuga canadensis L.) forest in central Massachusetts, USA, was estimated from mid-October 2000 through October 2001 based on eddy covariance measurements and statistical modeling from microclimatic data. Measurements were made in 68% of the hours during the year of study, with > 50% coverage in all months except December and August. Data were filtered by wind direction and atmospheric turbulence to remove invalid measurements. Analysis of filtered data showed that photosynthetically active radiation (PAR) was significant in predicting C exchange, except during the winter. Daily minimum air temperature affected C exchange in autumn and winter, whereas time of day, water vapor pressure deficit and air temperature had significant effects on C storage in spring, summer and fall. Most C storage in the stand occurred in April through July and in October 2001, with maximum rates in April and May. Persistent cold weather prevented C storage in December through March. In early spring 2001, C uptake was sensitive to nocturnal frost: daily minimum air temperatures below 0 degrees C reduced C fixation, and minima below -5 degrees C caused its virtual cessation. Soil temperature was a poor predictor of C balance during this period. In August, high soil and air temperatures (averaging 16.7 and 21.1 degrees C, respectively) drove high ecosystem respiration, which approximately balanced C uptake. These patterns show potential for stimulated C storage in hemlock forests in a warmer climate with fewer spring and autumn frosts, but reduced C storage during warmer summers. Estimated annual C storage was 3.0 Mg ha(-1), which is higher than for younger coniferous and deciduous forests during earlier years in the northeastern USA. Long-term data are needed to determine if the estimated high C storage in this hemlock forest is a result of interannual climate variation or an effect of forest composition.

[1]  Carbon storage and fluxes in ponderosa pine forests at different developmental stages , 2001 .

[2]  T. Lundh,et al.  On boundary layers , 1996 .

[3]  E. DeLucia,et al.  Air and soil temperature limitations on photosynthesis in Engelmann spruce during summer , 1987 .

[4]  S. Pacala,et al.  Forest models defined by field measurements : Estimation, error analysis and dynamics , 1996 .

[5]  G. Berntson,et al.  Regenerating temperate forests under elevated CO2 and nitrogen deposition: comparing biochemical and stomatal limitation of photosynthesis , 2001 .

[6]  Nathan Phillips,et al.  Biophysical controls of carbon flows in three successional Douglas-fir stands based on eddy-covariance measurements. , 2002, Tree physiology.

[7]  J. Hadley.  Effect of Daily Minimum Temperature on Photosynthesis in Eastern Hemlock (Tsuga canadensis L.) in Autumn and Winter , 2000 .

[8]  G. Carter,et al.  Autumn stomatal closure in six conifer species of the Central Rocky Mountains , 1984, Oecologia.

[9]  D. Foster,et al.  Long-Term Vegetation Dynamics and Disturbance History of a Tsuga-Dominated Forest in New England , 1993 .

[10]  M. G. Ryan,et al.  Hydraulic Limits to Tree Height and Tree Growth , 1997 .

[11]  Xuhui Lee,et al.  On micrometeorological observations of surface-air exchange over tall vegetation , 1998 .

[12]  E. Davidson,et al.  Interannual variation of soil respiration in two New England forests , 2001 .

[13]  S. Bassow,et al.  Intra- and inter-specific variation in canopy photosynthesis in a mixed deciduous forest , 1997, Oecologia.

[14]  Eric A. Davidson,et al.  Seasonal patterns and environmental control of carbon dioxide and water vapour exchange in an ecotonal boreal forest , 1999 .

[15]  Corinna Rebmann,et al.  Productivity of forests in the Eurosiberian boreal region and their potential to act as a carbon sink –‐ a synthesis , 1999 .

[16]  David R. Foster,et al.  FOREST RESPONSE TO THE INTRODUCED HEMLOCK WOOLLY ADELGID IN SOUTHERN NEW ENGLAND, USA , 1998 .

[17]  J. William Munger,et al.  Measurements of carbon sequestration by long‐term eddy covariance: methods and a critical evaluation of accuracy , 1996 .

[18]  J. Etherington,et al.  Physiological Plant Ecology. , 1977 .

[19]  Richard H. Waring,et al.  Forest Ecosystems: Concepts and Management , 1985 .

[20]  Richard H. Waring,et al.  Evidence of Reduced Photosynthetic Rates in Old Trees , 1994, Forest Science.

[21]  H. Schmid.  Source areas for scalars and scalar fluxes , 1994 .

[22]  I. Fung,et al.  Observational Contrains on the Global Atmospheric Co2 Budget , 1990, Science.

[23]  L. M. Tritton,et al.  Biomass equations for major tree species of the northeast. General technical report (final) , 1982 .

[24]  J. Hadley.  Understory microclimate and photosynthetic response of saplings in an old-growth eastern hemlock (Tsuga canadensis L.) forest , 2000 .

[25]  J. William Munger,et al.  Exchange of Carbon Dioxide by a Deciduous Forest: Response to Interannual Climate Variability , 1996, Science.

[26]  Maurizio Mencuccini,et al.  Hydraulic conductance, light interception and needle nutrient concentration in Scots pine stands and their relations with net primary productivity. , 1996, Tree physiology.

[27]  S. Wofsy,et al.  Factors Controlling Long- and Short-Term Sequestration of Atmospheric CO2 in a Mid-latitude Forest , 2001, Science.