Tree mortality in mature riparian forest: Implications for Fremont cottonwood conservation in the American southwest

Western North American Naturalist
By:

Links

Abstract

Mature tree mortality rates are poorly documented in desert riparian woodlands. I monitored deaths and calculated annual survivorship probability (Ps) in 2 groups of large (27–114 cm DBH), old (≥40 years old) Fremont cottonwood (Populus fremontii Wats.) in a stand along the free-flowing Yampa River in semiarid northwestern Colorado. Ps = 0.993 year-1 in a group (n = 126) monitored over 2003–2013, whereas Ps = 0.985 year-1 in a group (n = 179) monitored over the same period plus 3 earlier years (2000–2003) that included drought and a defoliating insect outbreak. Assuming Ps was the same for both groups during the 10-year postdrought period, the data indicate that Ps = 0.958 year-1 during the drought. I found no difference in canopy dieback level between male and female survivors. Mortality was equal among size classes, suggesting Ps is independent of age, but published longevity data imply that either Ps eventually declines with age or, as suggested in this study, periods with high Ps are interrupted by episodes of increased mortality. Stochastic population models featuring episodes of low Ps suggest a potential for an abrupt decline in mature tree numbers where recruitment is low. The modeling results have implications for woodland conservation, especially for relictual stands along regulated desert rivers.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Tree mortality in mature riparian forest: Implications for Fremont cottonwood conservation in the American southwest
Series title Western North American Naturalist
DOI 10.3398/064.075.0204
Volume 75
Issue 2
Year Published 2015
Language English
Publisher Brigham Young University
Publisher location Provo, UT
Contributing office(s) Fort Collins Science Center
Description 13 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Western North American Naturalist
First page 157
Last page 169
Country United States
State Colorado
Online Only (Y/N) N
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details