Conversion of natural forests to managed forest plantations impacts tree response to climatic variable and affects negatively tree resistance to prolonged droughts

  • Sites: US-Dk2
  • Publication Type: JOUR
  • Authors: Domec, J.C., Ward, E.J., Oishi, A.C., Palmroth, S., Radecki, A., Bell, D.M., Miao, G., Gavazzi, M., Johnson, D.M., King, J.S., McNulty, S.G., Oren, R., Sun, G., Noormets, A.

  • Throughout the southern US, past forest management practices have replaced large areas of native
    forests with loblolly pine plantations and have resulted in changes in forest response to extreme
    weather conditions. However, uncertainty remains about the response of planted versus natural
    species to drought across the geographical range of these forests. Taking advantage of a cluster of
    unmanaged stands (85–130 year-old hardwoods) and managed plantations (17–20 year-old loblolly
    pine) in coastal and Piedmont areas of North Carolina, tree water use, cavitation resistance,
    whole-tree hydraulic (Ktree) and stomatal (Gs) conductances were measured in four sites covering
    representative forests growing in the region. We also used a hydraulic model to predict the resilience
    of those sites to extreme soil drying. Our objectives were to determine: (1) if Ktree and stomatal
    regulation in response to atmospheric and soil droughts differ between species and sites; (2) how
    ecosystem type, through tree water use, resistance to cavitation and rooting profiles, affects the water
    uptake limit that can be reached under drought; and (3) the influence of stand species composition on
    critical transpiration that sets a functional water uptake limit under drought conditions. The results
    show that across sites, water stress affected the coordination between Ktree and Gs. As soil water
    content dropped below 20% relative extractable water, Ktree declined faster and thus explained the
    decrease in Gs and in its sensitivity to vapor pressure deficit. Compared to branches, the capability
    of roots to resist high xylem tension has a great impact on tree-level water use and ultimately had
    important implications for pine plantations resistance to future summer droughts. Model simulations
    revealed that the decline in Ktree due to xylem cavitation aggravated the effects of soil drying on tree
    transpiration. The critical transpiration rate (Ecrit), which corresponds to the maximum rate at which
    transpiration begins to level off to prevent irreversible hydraulic failure, was higher in managed forest
    plantations than in their unmanaged counterparts. However, even with this higher Ecrit, the pine
    plantations operated very close to their critical leaf water potentials (i.e. to their permissible water
    potentials without total hydraulic failure), suggesting that intensively managed plantations are more
    drought-sensitive and can withstand less severe drought than natural forests.

  • Journal: Forest Ecology and Management
  • Funding Agency: DOE, NSF, USDA FS, USDA NIFA, USFWS
  • Citation Information:
  • Volume: 355
  • No:
  • Pages: 58-71
  • Publication Year: 2015/11
  • DOI: 10.1016