Submitted to: Canadian Journal of Forest Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2004
Publication Date: 7/30/2004
Citation: Rowland, D., Sher, A.A., Marshall, D.L. 2004. Inter- and intra-population variation in seedling performance of rio grande cottonwood under low and high salinity. Canadian Journal of Forest Research. 34:1458-1466.
Interpretive Summary: The health of the Rio Grande ecosystem is being threatened by dam construction and high salinity levels in the water and soil. Adult cottonwood trees are known to differ in their tolerance of salt and mortality rates are highest where trees are less tolerant. We measured whether these salt tolerant traits could be passed on to seedling offspring by measuring the stunting effects of salt as the seedlings grew. We also compared the maternal tree's physiology with her seedling's growth to see if these traits were passed on to offspring. We found large stunting effects of salt on almost all growth characteristics including root mass, shoot mass, and plant height. Some seedlings were more tolerant than others to high salt. When we compared the maternal tree physiology with seedling growth under low and high salt, there were several important relationships that demonstrated salt tolerance could be passed on to seedlings.
Technical Abstract: The Rio Grande watershed ecosystem is becoming increasingly threatened due to the construction of dams and severe channelization over the past century. Rio Grande cottonwood (Populus deltoides var. wislizenii (S.Wats.) Eckenwalder) has been suffering stress and high mortality rates with decreased water availability and increased salinity levels. Genetic variation in salt tolerance has been documented in adult cottonwoods and we hypothesized that these traits might be heritable. This potential heritable genetic variation in seedling offspring might be advantageous in seedling reforestation efforts along the Rio Grande. We screened four New Mexican Rio Grande populations for seedling genotypes that might be salt tolerance and correlated seedling performance under both high and low salt treatments with the physiological performance of their maternal tress. We found significant stunting effects of high salt for all populations on mean leaf size, plant height, total plant mass, root mass, and shoot mass, with no effects on SPAD chlorophyll content or root to shoot ratio. While there were no significant differences among the four populations, there were highly significant differences among maternal trees within each site. In addition, genetically based maternal physiology, as measured in a common garden, was significantly correlated with seedling performance especially under low salt conditions. This indicates these traits are heritable and adult salt tolerance may convey an advantage in offspring establishment under high salt conditions.