Thèse (M.Sc.)--Université Laval, 1997. / Bibliogr.: f. 87-92. Publié aussi en version électronique.

Patterns of woody-plant mortality have been linked to global-scale environmental changes, such as extreme drought, heat stress, more frequent and intense fires, and episodic outbreaks of insects and pathogens. Although many studies have focussed on survival and mortality in response to specific physiological stresses, little attention has been paid to the role of genetic heritability of traits and local adaptation in influencing patterns of plant mortality, especially in non-native species. Tamarix spp. is a dominant, non-native riparian tree in western North America that is experiencing dieback in some areas of its range due to episodic herbivory by the recently introduced northern tamarisk leaf beetle (Diorhabda carinulata). We propose that genotype x environment interactions largely underpin current and future patterns of Tamarix mortality. We anticipate that (i) despite its recent introduction, and the potential for significant gene flow, Tamarix in western North America is generally adapted to local environmental conditions across its current range in part due to hybridization of two species; (ii) local adaptation to specific climate, soil and resource availability will yield predictable responses to episodic herbivory; and (iii) the ability to cope with a combination of episodic herbivory and increased aridity associated with climate change will be largely based on functional tradeoffs in resource allocation. This review focusses on the potential heritability of plant carbon allocation patterns in Tamarix, focussing on the relative contribution of acquired carbon to non-structural carbohydrate (NSC) pools versus other sinks as the basis for surviving episodic disturbance. Where high aridity and/or poor edaphic position lead to chronic stress, NSC pools may fall below a minimum threshold because of an imbalance between the supply of carbon and its demand by various sinks. Identifying patterns of local adaptation of traits related to resource allocation will improve forecasting of Tamarix population susceptibility to episodic herbivory.

The invasive species Saltcedar is affecting water and land resources throughout the western states of America. Because of great water use capabilities and other ecosystem detriments, Saltcedar has been targeted for treatment. For successful management of Saltcedar, individual landowners need to be aware of the costs and benefits of treating Saltcedar. Eleven of the most commonly reported treatment methods were evaluated for firm level economic feasibility. Evaluated on the basis of treatment cost, treatment effectiveness, Saltcedar water-use, and re-vegetation water-use, a production plan of ten years was created for each treatment method. Some treatment methods required re-treatment and were evaluated with re-treatments most commonly found in the literature. Of the treatment methods evaluated, five treatment methods were determined to be most feasible. Landowner valuation of environmental changes in the ecosystem brought on by Saltcedar is very important in the decision of which treatment method to implement. Personal valuation, over a period of ten years, will often determine which treatment methods are most cost efficient.

The density, diversity, and nest-site selection of riparian breeding birds were studied from 1982 to 1985 in mesquite (Prosopis glandulosa) and tamarisk (Tamarix chinensis) communites along the Colorado River in northern Arizona. Avian density in tamarisk communities was significantly greater (P=0.052 and 0.024 in 1984 and 1985, respectively) than avian density in native mesquite communities with similar vegetative cover and height attributes. Avian diversity was similar in both communities. Breeding bird densities in tamarisk were higher than those reported from other geographic areas. Vegetation structure and shrub species composition were measured at nest sites of eleven species of riparian birds in a tamarisk community to examine avian habitat relationships. Riparian birds exhibited differences in their choice of nesting habitat. Discriminant analysis indicated that Bell's Vireo (Vireo bellii), Yellow Warbler (Dendroica petechia) and Yellow-breasted Chat (Icteria virens) were relative generalists in nest site selection, while Common Yellowthroat (Geothlypis trichas) and Northern Oriole (Icterus galbula) were relative habitat specialists. Bell's Vireo and American Coot (Fulica americana) nested in habitats that were the most different. Willow Flycatcher (Empidonax traillii) and Yellow Warbler nested in habitats that were the most similar. Willow Flycatcher and Yellow Warbler consistently used habitat most similar to that used by all other species. Nest placement preferences of six riparian passerines were examined in the tamarisk community to test the null hypothesis that nest placement in any given species of shrub was random. Ninety-five of 105 nests sampled were located in tamarisk. Five of the six species of passerines exhibited a significant preference for tamarisk for nest placement. A highly significant preference for tamarisk was shown by the four species with the smallest median frequency of tamarisk in their nesting habitat. The usefulness of tamarisk for nest placement was higher than that reported from other areas.

Le phénomène naturel d’érosion des berges peut menacer des infrastructures humaines. Des protections végétales peuvent être installées afin de mimer les dynamiques de végétation et armer la berge grâce aux racines. Cependant, les changements climatiques globaux sont susceptibles d’entraîner et d’aggraver les sécheresses, ce qui va stresser les végétaux présents et compromettre la bonne réussite des ouvrages de génie végétal. La principale question est donc « Quelles sont les caractéristiques biotechniques et les facultés d’acclimatation à la sécheresse de boutures de Salicaceae et Tamaricaceae, espèces utilisées ou potentiellement utilisables en génie végétal ? ». L’étude de différentes populations d’espèces classiquement utilisées que sont les saules démontre une résistance à la sécheresse plus efficace des populations méridionales tandis que les productions de biomasses restent plus élevées chez les populations septentrionales. L’étude des traits biotechniques et du comportement racinaire d’espèces potentielles appartenant aux Tamaricaceae (Tamarix gallica et Myricaria germanica) montre un taux élevé de reprise au bouturage, une forte production de biomasses et une stratégie de prospection racinaire différente des saules, ce qui leur confère une résistance à la sécheresse accrue. Ceci confirme une utilisation possible de ces espèces dans des ouvrages de génie végétal soumis à sécheresse. / The natural phenomenon of riverbank erosion can threaten human stakes. Vegetative bioengineering protections can be installed to imitate the vegetation dynamics and anchor the soil bank thanks to roots. However, global climate change could induce and increase droughts, what is going to stress plants and to compromise the bioengineering works success. The main question is thus " what are the biotechnical capabilities and the drought acclimatization faculties of cuttings of Salicaceae and Tamaricaceae, species used or potentially useful in bioengineering? ". The study of different populations of species such as willows demonstrates a more effective drought resistance of the Southern populations whereas the biomass productions remain higher with the Northern populations. The study of the biotechnical traits and the root behavior potentially useful species such as Tamaricaceae (Tamarix gallica and Myricaria germanica) show a high resprouting rate, a high biomass production and a prospecting root strategy different from willows. This results confer them a better drought resistance. This confirms a possible use of these species in vegetative bioengineering works subjected to drought.

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Le phénomène naturel d'érosion des berges peut menacer des infrastructures humaines. Des protections végétales peuvent être installées afin de mimer les dynamiques de végétation et armer la berge grâce aux racines. Cependant, les changements climatiques globaux sont susceptibles d'entraîner et d'aggraver les sécheresses, ce qui va stresser les végétaux présents et compromettre la bonne réussite des ouvrages de génie végétal. La principale question est donc " Quelles sont les caractéristiques biotechniques et les facultés d'acclimatation à la sécheresse de boutures de Salicaceae et Tamaricaceae, espèces utilisées ou potentiellement utilisables en génie végétal ? ". L'étude de différentes populations d'espèces classiquement utilisées que sont les saules démontre une résistance à la sécheresse plus efficace des populations méridionales tandis que les productions de biomasses restent plus élevées chez les populations septentrionales. L'étude des traits biotechniques et du comportement racinaire d'espèces potentielles appartenant aux Tamaricaceae (Tamarix gallica et Myricaria germanica) montre un taux élevé de reprise au bouturage, une forte production de biomasses et une stratégie de prospection racinaire différente des saules, ce qui leur confère une résistance à la sécheresse accrue. Ceci confirme une utilisation possible de ces espèces dans des ouvrages de génie végétal soumis à sécheresse.