DROUGHT CONDITIONING CONIFER SEEDLINGS FOR POST-FIRE MANAGEMENT AND CLIMATE CHANGE ADAPTATION

Author

Anna C. Ross, University of Montana, MissoulaFollow

Year of Award

2024

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Systems Ecology

Department or School/College

W.A. Franke College of Forestry & Conservation

Committee Chair

Dr. Andrew J. Larson

Commitee Members

Dr. Cara R. Nelson, Dr. Anna Sala, Dr. Justin S. Crotteau, Dr. Jeremiah R. Pinto

Keywords

Conifer seedlings, Nursery experiment, Post-fire management, Regeneration, Climate change adaptation

Subject Categories

Natural Resources and Conservation

Abstract

Increased frequency, severity, and duration of drought and increased wildfire severity are together impacting forests of the western U.S. To encourage forest ecosystem resilience to these changing disturbance regimes, there is a need for novel silvicultural techniques that develop seedlings capable of establishing in hotter and drier climates. We evaluated the morphological and physiological effects of a drought conditioning treatment applied in a greenhouse on second- year ponderosa pine (Pinus ponderosa), western white pine (Pinus monticola), and western larch (Larix occidentalis) seedlings. Treatments included a well-watered control (75% of container capacity) and a water-limited (40% of container capacity) irrigation regime. Drought conditioning caused significant reduction of height and root-collar diameter for western larch, and reduction of root-collar diameter for western white pine. Drought conditioning treatments significantly reduced gas exchange rates for ponderosa pine and western larch at their target container capacities. Seedlings were outplanted in the spring of 2023 at two sites that burned with high severity in 2021. Observations of outplanted seedlings indicated no treatment effect on survival or on carbon isotope composition (δ¹³C), although there was some evidence of instantaneous acclimation of drought-conditioned seedlings provided by pre-dawn water potential measurements. Second-year stock of ponderosa pine proved extremely vigorous and capable of high survival on a site with soil matric potentials of -5 MPa during peak summer.

Recommended Citation

Ross, Anna C., "DROUGHT CONDITIONING CONIFER SEEDLINGS FOR POST-FIRE MANAGEMENT AND CLIMATE CHANGE ADAPTATION" (2024). Graduate Student Theses, Dissertations, & Professional Papers. 12312.
https://scholarworks.umt.edu/etd/12312