Ecosystems

, Volume 14, Issue 4, pp 658–671

Carbon, Water, and Energy Exchanges of a Hybrid Poplar Plantation During the First Five Years Following Planting

  • Tiebo Cai
  • David T. Price
  • Alberto L. Orchansky
  • Barb R. Thomas
Article

DOI: 10.1007/s10021-011-9436-8

Cite this article as:
Cai, T., Price, D.T., Orchansky, A.L. et al. Ecosystems (2011) 14: 658. doi:10.1007/s10021-011-9436-8
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Abstract

Eddy covariance was used to measure above-canopy exchanges of CO2 and water vapor at an operational plantation of hybrid poplar (variety “Walker”) established on marginal agricultural land in east central Alberta, Canada. Winter ecosystem respiration (Re) rates were inferred from seasonal changes in the normalized respiration rate at 10°C (R10) for the growing season and observations of soil CO2 concentration measured with solid-state probes. Over five consecutive growing seasons following planting, gross ecosystem production (GEP) increased each year, ranging from 21 g C m−2 y−1 in year 1 to 469 g C m−2 y−1 in year 5. During this period, the annual carbon balance shifted from a net source of greater than 330 g C m−2 in year 1 to approximately C-neutral in year 5. Total carbon (C) release over 5 years likely exceeded 630 g C m−2. Intra- and interannual variations in temperature and soil water availability greatly affected annual C balance each year. GEP and Re were particularly sensitive to temperature during spring and to soil water availability in summer: year 5 was notable because a cold spring and accumulating drought caused growth and carbon uptake to fall well below their potential. Annual evapotranspiration (ET) increased slightly with leaf area, from 281 mm in year 1 to 323 mm in year 4, but in year 5 it declined, while exceeding total precipitation (P). This trend of increasing annual ET/P suggests that annual GEP could become increasingly water-limited in years with below normal precipitation, as the plantation achieves maximum leaf area. Measured canopy albedos did not change appreciably over three winters, suggesting that estimates of increased radiative forcing resulting from afforestation in high latitudes could be exaggerated in regions where fast-growing deciduous plantations are managed on short (~20-year) rotations.

Key words

plantationhybrid poplarnet ecosystem exchangechronosequencecarbon sequestrationdroughtland-use change

Copyright information

© Her Majesty the Queen in right of Canada 2011

Authors and Affiliations

  • Tiebo Cai
    • 1
  • David T. Price
    • 1
  • Alberto L. Orchansky
    • 2
  • Barb R. Thomas
    • 3
    • 4
  1. 1.Natural Resources CanadaNorthern Forestry CentreEdmontonCanada
  2. 2.Micrometeorology ConsultantEdmontonCanada
  3. 3.Alberta-Pacific Forest Industries IncBoyleCanada
  4. 4.Department of Renewable ResourcesUniversity of AlbertaEdmontonCanada