Variation in morphological, phenological, and physiological traits among southwestern ponderosa pine provenances: insights from field and greenhouse common gardens

Dixit, Aalap Himanshubhai (2021) Variation in morphological, phenological, and physiological traits among southwestern ponderosa pine provenances: insights from field and greenhouse common gardens. Doctoral thesis, Northern Arizona University.

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Abstract

Ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm.) forests of the southwestern U.S. are threatened by climate change. Drought-related tree mortality is already a matter of concern in southwestern ponderosa pine forests and this mortality is expected to intensify over the next century as atmospheric temperature and drought severity increase. In addition, droughts and wildfires have caused a reduction in seedling regeneration and establishment. These recent losses of southwestern ponderosa pine forests may be compensated through artificial regeneration by planting drought tolerant seed sources under increasingly arid conditions. We used field and greenhouse common gardens to investigate provenance variations in survival, growth, budburst phenology, and drought-adapted morphological and physiological traits in ponderosa pines seedlings. Twenty-one provenances from a range of elevations across Arizona and New Mexico were planted in three field common gardens across an elevation gradient: low elevation site in pinyon juniper woodland (1930 m), mid elevation site in ponderosa pine forest (2200 m), and high elevation site in aspen and mixed conifer forest (2780 m). Ten out of the 21 provenances from different elevations were planted in a greenhouse common garden at the Northern Arizona University Greenhouse Facility in Flagstaff, Arizona. We evaluated the overall hypothesis that seedlings traits would vary with provenance environmental characteristics and that low elevation, warmer provenances would have traits more conducive to dry and warm conditions than high elevation, cooler provenances. Results from field common gardens suggest that seedling survival and performance depends on planting location and that low elevation provenances should be considered for planting at trailing-edge and core sites. The importance of biotic agents of seedling mortality increased with elevation of the planting site suggesting that high mortality from biotic agents should be anticipated for plantings at high elevations during assisted migration. Results suggest adaptation of low elevation provenances to warm spring temperatures due to earlier budburst of provenances from low elevations under field and greenhouse conditions. Results from the mid-elevation site suggested a trade-off between growth and water use efficiency under unusually dry conditions. Results from greenhouse common garden suggest: adaptation of low elevation provenances to aridity (as indicated by a lower specific leaf area); faster growth of provenances from wet locations; and greater allocation to roots in western provenances. Such information about environmental and geographical patterns of provenance variation may be useful for developing specific seed transfer guidelines and effective assisted migration strategies to maintain ponderosa pine in a changing climate.

Item Type:	Thesis (Doctoral)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Ponderosa pine; Regeneration; Seedling survival; Seedling regeneration; Southwest (U.S.); Drought-tolerant seed;
Subjects:	S Agriculture > SD Forestry
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > School of Forestry
Date Deposited:	24 Feb 2022 15:53
Last Modified:	19 May 2022 08:30
URI:	https://openknowledge.nau.edu/id/eprint/5749

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