No description available.

The purpose of this study was to determine whether defoliation, a condition of stress caused by Choristoneura fumiferana herbivory, induces a disturbed pathologic condition in presumably normal tissue produced by the affected balsam fir trees. Techniques used in this investigation included dry weight determination, light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and biochemical and physical analyses. Terminal branch sections that contained shoots with buds and needles were cut from the upper crown on opposite sides of the tree. Collections were made from several previously selected trees in Vermont during April, June and July. The collected materials were labelled, placed in plastic bags and returned to the laboratory for histological and electron microscopic studies. The shoots derived from buds of stressed trees were shorter and produced fewer needles than shoots derived from equivalent position in nondefoliated buds. Unlike July-collected buds, the April buds did not exhibit distinct apical meristem zonation. The ultrastructural study of defoliated April-collected buds differed from nondefoliated buds, in that nondefoliated buds, were very active prior to bud burst and shoot elongation. This activity was indicated by the substantial increase in the number of Golgi-associated vesicles, several large vacuoles with heavy electron dense granular inclusions, abundant rough endoplasmic reticulum, proplastids and cell plate formation. Defoliated bud cells, unlike the nondefoliated bud cells did not contain a high population of cells exhibiting Golgi-associated rich regions, mitochondria, and apparent ce 11 p 1 ate formation. The absence or reduced presence of these metabolic indicators, in defoliated Aprilcollected buds suggest that the defoliated buds are metabolically disturbed. The eventual elongation of shoots of reduced length and number of needles as observed in June-collected buds indicates that activity was not completely inhibited in defoliated buds. The smaller bud size in defoliated balsam fir could also mean that prior accumulation of substances by the bud was effectua1 in that bud development may have been delayed. These findings indicate that Choristoneura fumiferana herbivory alters bud development.

Graduation date: 1952

Understanding the underlying genetic causes of adaptation to local conditions is one of the main goals of population genetics. A strong latitudinal cline in the phenotypic trait of bud set is observed in present day populations of Norway spruce (Picea abies (L.) Karst). The first step towards determining how this strong selection on adaptive traits translates at the loci underlying the trait was to use multilocus sequence data to gain information on the fundamental population genetic properties of Norway spruce. We determined that the level of LD was low and genetic diversity was in the low range. Coalescent simulations revealed a demographic scenario of a fairly old and severe bottleneck as consistent with the observed data. To examine the role of selection at genes putatively involved in the control of bud set we, again, used a multilocus data set to test for deviations from neutrality and demographic scenarios inferred from background loci. Different candidate genes were identified by using different approaches, highlighting the difficulty in predicting how local adaptation will manifest itself on different time scales and in rangewide samples. When examining properties important in the design of association studies, the inevitable next step in identifying genes involved in local adaptation, we found that previous estimates of a low level of LD were highly influenced by the joint analysis of several loci over a large distribution range and that estimates of LD was in fact heterogeneous across loci and increased within populations. In addition, we found that within species tests for deviations from neutral expectations were highly sensitive to sample size. Additional genomic sequence characterization in Norway spruce is necessary to provide more comprehensive sets of markers for association studies, also including gene promoters and non-genic regions of the genome. In the final paper we show that the HMPR method is effective in constructing libraries enriched for the single copy fraction of the genome when applied to the large and dominantly repetitive genome of Norway spruce. In summary, the studies presented in this thesis together constitute a foundation for future studies on adaptive evolution in Norway spruce.

Thesis (M.S.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references (leaves 126-143). Also available on the World Wide Web.

Les hêtraies-sapinières-pessières de montagne paraissent particulièrement menacées par le réchauffement climatique. Pour appréhender la dynamique future de ces forêts et adapter la sylviculture à ces nouvelles conditions, il est important de mieux connaître les facteurs environnementaux impactant la démographie de ces espèces. Nous avons abordé cette problématique en combinant des données historiques de gestion, le modèle de dynamique forestière Samsara2 et une méthode de calibration basée sur le Calcul Bayésien Approché. Nous avons ainsi pu étudier conjointement les différents processus démographiques dans ces forêts. Nos analyses montrent que la démographie forestière peut varier fortement entre les parcelles et que le climat n'est pas toujours déterminant pour expliquer ces variations. Ainsi, malgré les changements climatiques attendus, la gestion irrégulière pratiquée actuellement devrait permettre de maintenir les services rendus par les peuplements mélangés situés en conditions mésiques. / The spruce-fir-beech mountain forests could be particularly threatened by the global warming. To better understand the future dynamics of these forests and adapt the silviculture to these new conditions, a better knowledge of the environmental factors affecting the species demograhics is needed. We studied this issue by combining a historical management data set, the forest dynamics model Samsara2 and a calibration method based on Approximate Bayesian Computation. We were able thus to study jointly the different demographic process in these forests. Our analysis show that the forest demographics can strongly vary between stands and that climate is not always determining to explain these variations. The unven-aged management currently applied seem adapted for the mixed stands located in mesic conditions, but the pure spruce forests and the low elevation stands could be highly impacted.

No description available.

No description available.

No description available.