Advanced

Physiological responses to drought in healthy and stressed trees : a comparison of four species in Oregon, USA

Kelly, Julia LU (2016) In Student thesis series INES NGEM01 20161
Dept of Physical Geography and Ecosystem Science
Abstract
Four tree species in Oregon (USA) were studied to examine physiological and structural responses to drought stress: ponderosa pine (Pinus ponderosa) and western juniper (Juniperus occidentalis) in a semi-arid ecoregion, and Douglas-fir (Pseudotsuga menziesii) and white oak (Quercus garryana) in a mesic coastal ecoregion. This investigation compared the response of paired healthy and stressed (<10% and ≥10% canopy loss respectively) trees to drought using leaf and soil water potential as well as tree-ring width data. Stressed trees, as indicated by canopy condition, were expected to be more drought stressed but there was generally no significant difference in leaf water potentials between the two categories, although leaf water potentials... (More)
Four tree species in Oregon (USA) were studied to examine physiological and structural responses to drought stress: ponderosa pine (Pinus ponderosa) and western juniper (Juniperus occidentalis) in a semi-arid ecoregion, and Douglas-fir (Pseudotsuga menziesii) and white oak (Quercus garryana) in a mesic coastal ecoregion. This investigation compared the response of paired healthy and stressed (<10% and ≥10% canopy loss respectively) trees to drought using leaf and soil water potential as well as tree-ring width data. Stressed trees, as indicated by canopy condition, were expected to be more drought stressed but there was generally no significant difference in leaf water potentials between the two categories, although leaf water potentials did vary markedly among species. In some cases stressed trees showed more variable growth rates and more sensitive responses to climatic variables than healthy trees, suggesting they were predisposed to be more drought stressed than healthy trees. (Less)
Popular Abstract
Droughts limit tree growth, or can cause tree death, because hot and dry weather limits water availability and a tree’s ability to produce the sugars it needs for growth. This thesis compared how healthy trees and trees dying from drought responded to a drought in Oregon, USA, during summer 2015. Healthy and dying trees were paired according to size and height so ensure these factors did not influence the results. Healthy and dying trees were identified based on the amount of leaves they had lost due to drought (healthy trees had lost <10% and dying trees ≥10% of their leaves). Four tree species were investigated: ponderosa pine, western juniper, Douglas-fir and white oak.

The results showed that although the dying trees appeared to be... (More)
Droughts limit tree growth, or can cause tree death, because hot and dry weather limits water availability and a tree’s ability to produce the sugars it needs for growth. This thesis compared how healthy trees and trees dying from drought responded to a drought in Oregon, USA, during summer 2015. Healthy and dying trees were paired according to size and height so ensure these factors did not influence the results. Healthy and dying trees were identified based on the amount of leaves they had lost due to drought (healthy trees had lost <10% and dying trees ≥10% of their leaves). Four tree species were investigated: ponderosa pine, western juniper, Douglas-fir and white oak.

The results showed that although the dying trees appeared to be more drought-stressed (due to the large amount of leaves they had lost), there was little difference in the leaf water potential between healthy and dying trees. Leaf water potential is a measure of the water pressure in a leaf: the lower the water potential, the less water the tree is able to access, indicating drought stress. This suggests that by losing leaves, the dying trees were able to compensate for being water limited due to the drought. Measurements of past tree growth showed that in some species, the dying trees had previously grown less or had a stronger reaction to past droughts compared to the healthy trees. These previous patterns in tree growth suggest the dying trees were more likely to die during future droughts. (Less)
Please use this url to cite or link to this publication:
author
Kelly, Julia LU
supervisor
organization
course
NGEM01 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
tree-rings, water potential, geography, physical geography, drought
publication/series
Student thesis series INES
report number
395
funder
U.S. Department of Energy
funder
USDA National Institute of Food and Agriculture
language
English
additional info
External supervisor: Beverly Law (Oregon State University)

This research was supported by the U.S. Department of Energy (Grant #DE-SC0012194, and LBNL subcontract #7117975), and the USDA National Institute of Food and Agriculture (Grant numbers 2014-67003-22065 and 2014-35100-22066).
id
8886576
date added to LUP
2016-08-22 10:02:27
date last changed
2016-08-22 10:02:27
@misc{8886576,
  abstract     = {Four tree species in Oregon (USA) were studied to examine physiological and structural responses to drought stress: ponderosa pine (Pinus ponderosa) and western juniper (Juniperus occidentalis) in a semi-arid ecoregion, and Douglas-fir (Pseudotsuga menziesii) and white oak (Quercus garryana) in a mesic coastal ecoregion. This investigation compared the response of paired healthy and stressed (<10% and ≥10% canopy loss respectively) trees to drought using leaf and soil water potential as well as tree-ring width data. Stressed trees, as indicated by canopy condition, were expected to be more drought stressed but there was generally no significant difference in leaf water potentials between the two categories, although leaf water potentials did vary markedly among species. In some cases stressed trees showed more variable growth rates and more sensitive responses to climatic variables than healthy trees, suggesting they were predisposed to be more drought stressed than healthy trees.},
  author       = {Kelly, Julia},
  keyword      = {tree-rings,water potential,geography,physical geography,drought},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Physiological responses to drought in healthy and stressed trees : a comparison of four species in Oregon, USA},
  year         = {2016},
}