Dl. Rowland et Nc. Johnson, Sexual demographics of riparian populations of Populus deltoides: Can mortality be predicted from a change in reproductive status?, CAN J BOTAN, 79(6), 2001, pp. 702-710
Citations number
30
Categorie Soggetti
Plant Sciences
Journal title
CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE
Populus deltoides var. wislizenii (S. Wats.) Eckenwalder (cottonwood) fores
ts along the Rio Grande drainage are predicted to disappear within this cen
tury. We evaluated stand health over 3 years by examining the sex ratio, si
ze, and spatial distribution of male, female, and nonreproductive trees in
six even-aged stands of P. deltoides spanning 280 km along the Rio Grande d
rainage. There was no evidence of biased sex ratios or spatial segregation
of sexes; however, tree mortality was strongly related to reproductive stat
us. In the most stressed population, over half of the mature trees remained
nonreproductive and a substantial number switched from reproductive to non
reproductive status. Logistic regression revealed that over all populations
, tree size, reproductive status in previous years, and population were sig
nificant factors affecting reproduction. By considering physiological and e
nvironmental differences, we determined two groups of nonreproductive indiv
iduals: those previously reproductive that became nonreproductive and those
that remained nonreproductive over the 3 years. The former group appeared
to be under greater physiological and environmental stress. Monitoring the
rate at which individuals change reproductive status provides an effective
and simple measurement that can predict survival of riparian cottonwood pop
ulations.