No description available.

4 pp. / This is part of a series on climate variability and forested ecosystems / Recent events in the forests of the Southwest have prompted scientists to consider the role of climate variability in insect and disease cycles. Over 70 million pine trees along with millions of other conifers died in 2002-03. Average temperature increases of 3°C enabled the MPB at those high elevations to achieve univoltine (having one generation per year) reproduction leading to previously unheard of outbreaks in white bark pine at high elevation sites in Idaho.Aspen defoliation in Arizona and New Mexico averaged ~ 20,375 acres from 1990 to 1997. A series of events has contributed to the decline of aspen since 1997.

Araucaria angustifolia é a única conífera nativa com importância econômica no Brasil. A espécie está incluída na lista oficial de espécies de plantas ameaçadas de extinção. A embriogênese somática é considerada como uma das ferramentas biotecnológicas mais promissoras na área de biotecnologia de plantas. A identificação de marcadores, que possam ser utilizados, para a seleção de genótipos aptos ao desenvolvimento do embrião somático é altamente desejável, uma vez que o desenvolvimento apropriado do embrião somático é extremamente dependente do genótipo. O presente trabalho teve como objetivo estudar e identificar marcadores bioquímicos e moleculares associados à competência para embriogênese somática em A. angustifolia. Culturas embriogênicas de genótipos com diferentes potenciais embriogênicos apresentaram diferenças nos parâmetros bioquímicos e moleculares avaliados (Poliaminas, expressão dos genes AaSERK1 e AaPP2C, proteoma). O presente trabalho propõe a utilização destes parâmetros como possíveis marcadores do potencial embriogênico no sistema A. angustifolia. / The Araucaria angustifolia is the only native conifer species with economical importance in Brazil. Recently, the species was included in the official list of endangered plant species. Somatic embryogenesis, i.e., in vitro asexual production of embryos is considered one of the most promising biotechnological tools in the area of plant biotechnology. Since the development of somatic embryos is dependent of the genotype, the identification of markers that could be used in the selection of genotypes which can develop somatic embryos is highly desirable. The main objective of the present work is to study and identify biochemical and molecular markers associated with competence for somatic embryogenesis in A. angustifolia. The evaluation of biochemical and molecular aspects (Polyamines, AaSERK1 and AaPP2C gene expression and proteome) indicated differences between embryogenic cultures of genotypes with different embryogenic potential. This work proposes the utilization of these parameters as possible markers of embryogenic potential in the system A. angustifolia.

Wood from coniferous trees is an important source of renewable biomass. It can contribute to provision of carbon neutral energy, biomaterials and housing for a growing population. Softwood is mainly composed of cellulose, galactoglucomannan, xylan and lignin. This thesis focuses on the biosynthesis and function of Glucuronic acid (GlcA) decorations on softwood xylan. Results demonstrate that this GUX (GlucUronic acid substitution of Xylan)-dependent xylan branching is critical for the maintenance of biomass recalcitrance in a model vascular plant Arabidopsis thaliana. Experiments employing in vitro and in planta activity assays show that conifer transcriptomes encode at least two distinct GUX enzymes which are active glucuronosyltransferases. Interestingly, these enzymes have different specific activities, with one adding evenly spaced GlcA branches and the other one being able to add consecutive decorations. It is possible that these different patterns of xylan branching may have an impact on ability of xylan to interact with cellulose fibrils. To investigate the role for xylan binding to cellulose, Arabidopsis mutant plants in which this interaction is lost were evaluated alongside transgenic mutant lines in which the interaction may be restored. Results of this analysis indicate that the presence of cellulose-bound xylan might have an influence on plant vasculature integrity and thus it may have an effect on plant growth and biomass properties. Moreover, further results indicate that some xylan cellulose interaction is likely to occur in cell wall macrofibrils which can be detected in softwood. Taken together, this thesis provides insights into the process of conifer xylan glucuronidation and the possible role these branches may be playing in the maintenance of softwood recalcitrance and mechanical properties. In addition to identifying potential mutagenesis targets for improving softwood processing, this work is a proof of concept for the use of GUX enzymes for in vivo and in vitro biosynthesis of novel xylan structures with potential industrial application.

No description available.

A severe wildfire burned 454 hectares of a second-growth Douglas-fir forest in 1977 on a north-facing slope in Pattee Canyon, near Missoula, Montana. The slope was aerially seeded with a grass mixture, from which Dactylis glomerata established best. Community structure, conifer regeneration, and the impact of the seeded grass on the plant community were evaluated with two data sets. One set tracked postfire vegetation development from 1979 to 1987 on permanent transects established on upland sites in areas of varying fire severity. The second data set was collected in 1989 on upland sites nearest to the bum edge where conifer regeneration was expected to be greatest. Most stands converged to a similar ordination space by 1987, showing that several key species which established in the initial postfire year determined community structure. These species were largely on-site survivors (including Calamagrostis rubescens, Physocarpus malvaceus, and Spiraea betulifolia) and the seeded grass, D. glomerata. The spread of this species by 1987 to stands that apparently escaped seeding in 1977 suggested that this species may persist at this site. Patterns of species abundance and distribution in 1989 were primarily controlled by factors summarized by a topographic-moisture index and by pre-burn disturbance history. Three general site types were described by an ordination. Areas that appeared as open woodlands in 1937 occurred on ridges and had more xerophytic vegetation in 1989, including native grasses. Conifer regeneration in this region was limited primarily to Pseudotsuga menziesii (Douglas-fir). Areas that appeared as an even, young forest in 1937 were on open slopes and were associated with Pinus contorta (lodgepole pine), Larix occidentalis (western larch), Vaccinum globulare, and Amelanchier alnifolia. Areas that appeared as an older, uneven-aged forest in 1937 were on open slopes near the upper burn edge and were characterized by Douglas-fir and Spiraea betulifolia in 1989. D. glomerata was more successful on the drier ridges and was negatively associated with Calamagrostis rubescens. Competition with C. rubescens, rather than differences in environmental tolerances, most likely restricted D. glomerata to the more xeric sites. An adverse effect of D. glomerata on conifer regeneration was most likely for western larch on xeric sites. Site factors and historical factors were most important in determining patterns of conifer regeneration. Regeneration was moderate on mesic slopes and sparse on xeric ridges. The extreme density of lodgepole pine regeneration (13,000 stems/hectare) in one mesic area reflected the importance of serotiny for post-fire regeneration of this species. Douglas-fir regeneration ranged from 370 stems/ha in a mesic area where no mature survivors were noted to 4045 stems/ha on a mesic slope near survivors. On mesic slopes near survivors, western larch regeneration was 857 stems/ha and was minimal elsewhere. A regression model confirmed the importance of site factors, site history, and availability of seed source for Douglas-fir and lodgepole pine. The model for western larch was only able to explain 14% of regeneration pattern, suggesting that microsite variation as well as other variables would be needed to predict regeneration for this species. / Graduation date: 1992

Magistro darbe tiriama paprastosios pušies (Pinus sylvestris L.) spyglių histologinės savybės pramoninės taršos poveikyje. Darbo objektas - paprastoji pušis (Pinus sylvestris L) auganti prie didžiausių Lietuvos gamyklų AB „Achema“, AB „Akmenės cementas“, AB „Mažeikių nafta“. Darbo tikslas - įvertinti spyglių histologines savybes priklausomai nuo pramoninės taršos. Darbo metodai - paprastosios pušies spyglių histologinės savybės tirtos mikroskopu. Išmatuoti paprastosios pušies spyglių audiniai: spyglio ilgis, skerspjūvio storis, skerspjūvio plotis, centinio cilindro storis, kutikulos storis, eridermio storis, hipodermos storis, adaksialinės laidžiosios parechimos storis, abaksialinės laidžiosios parencimos storis, adaksialinis mezofilo storis, abaksialinis mezofilo storis. Darbo rezultatai. Paprastosios pušies (Pinus sylvestris L.) spygliai tirti prie didžiausių Lietuvos gamyklų AB „Achema“, AB „Akmenės cementas“, AB „Mažeikių nafta“. Mezomorfine spyglių struktūra pasižymėjo pušys augančios arčiausiai AB „Mažeikių nafta“ gamyklos. Kseromorfinė struktūra pasireiškė spygliuose augančiuose AB „Akmenės cementas“ apylinkėse. / In the Science work of Master examined Scots pine (Pinus sylvestris L.) needles. Subject of research - Scots pine (Pinus sylvestris L.) Goal of the research - To evaluate histology of the needles of Scots pine growing at different distance from a nitrogen fertilizer factory, a cement factory, an oil refinery factory. Methodology - light microscopy of cross sections of the needles (needle thickness, needle width, adaxial mesophyll thickness, abaxial mesophyll thickness, epidermis, hypodermis, cuticle, central cylinder, parenchyma, needle lenght). Research results. Scots pine (Pinus sylvestris L.) needles were examined near the biggest technogenic polluters (cement factory, oil refinery, nitrogen fertilizer factory) in Lithuania. The most mesomorphic structure of the needles was registered for the pines growing close to the oil refinery and the most xeromorphic structure was characteristic for the pines near the cement factory.

The effects of lichen ground cover (predominantly Cladina stellaris) on the growth of Picea mariana at Schefferville, Quebec and Pinus sylvestris at Kevo, Finland, was investigated in situ. Effect on seedling establishment was inferred through examining status quo conditions. While contiguous mat cover precluded establishment, its margins provided ameliorated conditions suitable for establishment. Moss covered areas were the most preferred sites. At Schefferville, ten perturbations involving fertilization, lichen removal, polyethylene overlays, and aqueous lichen extract application were effected on sixteen experimental plots. Branch elongation, needle nitrogen and bole diameter were statistically analyzed as functions of various monitored edaphic conditions. Leader elongation and needle nitrogen was measured at Kevo. Lichen presence over the term of both studies showed net beneficial effect on the trees; lichen extracts had significant detrimental effects. Seed germination was suppressed by lichen presence but enhanced by lichen induced low soil pH when in contact with the soil.

Thesis (Ph. D.)--Ohio State University, 2009. / Title from first page of PDF file. Includes bibliographical references (p. 179-190).

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2010. / Härtill 3 uppsatser.