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Accueil du site → Doctorat → États-Unis → 2013 → Ecophysiology of Populus fremontii : Effects of inundation, and interactions among nitrogen form, nutrient level, and water availability

UNIVERSITY OF CALIFORNIA, DAVIS (2013)

Ecophysiology of Populus fremontii : Effects of inundation, and interactions among nitrogen form, nutrient level, and water availability

Auchincloss, Lisa Cutting

Titre : Ecophysiology of Populus fremontii : Effects of inundation, and interactions among nitrogen form, nutrient level, and water availability

Auteur : Auchincloss, Lisa Cutting

Université de soutenance : UNIVERSITY OF CALIFORNIA, DAVIS

Grade : Doctor of Philosophy (PhD) 2013

Résumé
As the climate changes and land continues to be developed for agricultural and urban use, ecosystems around the globe will experience shifts in hydrologic cycles, CO2 concentrations, water availability, and nutrient availability. Semi-arid riparian forests in the North American West will be particularly affected by these changes since establishment of riparian vegetation depends on the river hydrograph, urban and agricultural runoff, water and air temperature, CO2 concentration, and soil nutrient availability. Fremont cottonwood (Populus fremontii) is an early successional foundation species in these ecosystems that establishes along barren point bars and contributes many important ecosystem functions. Furthermore, the genus Populus is important as a model to study forest trees, a commercial crop, and a foundational component of many ecosystems throughout North America. Investigations of P. fremontii seedling establishment will prove useful not only in modeling riparian vegetation establishment and health, but also to help quantify responses of the genus to the far reaching effects of climate change and shifts in nutrient levels. The three chapters of this dissertation investigate responses of P. fremontii seedlings to 1) variation in inundation depth, duration, and temperature, 2) variation in atmospheric CO2 concentration and N form (NO3- and NH4+), and 3) variation in nutrient level, soil water availability, and N form. Investigations of seedling tolerance of inundation showed that mortality increased linearly with days of complete shoot submergence (mortality % = 4.6 + (2.5 × days)), resulting in greater than 60% mortality after four weeks of complete submergence. Cooler water temperature (18/11°C day/night) during complete submergence positively affected seedling dry weight and survival resulting in 25% greater seedling survival than at warmer water temperatures (25/18°C day/night). Results indicated that establishment of new P. fremontii populations in the riparian corridor will be more successful when flows do not completely cover the shoots of seedlings for more than two weeks and if water temperatures during inundation are cool.

Subject : Plant biology ; Ecology

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