Le pin maritime (Pinus pinaster Ait.) est l’une des principales espèces forestières en France, fournissant près d’un quart de la production nationale de bois. Un programme d’amélioration, mis en place dans les années 1960, propose des variétés génétiquement améliorées pour la croissance et la rectitude du tronc.Cette thèse explore la possibilité d’introduire les marqueurs moléculaires dans les stratégies d’amélioration génétique du pin maritime en Aquitaine. Les marqueurs sont utilisés afin de reconstituer a posteriori les pedigrees au sein d’un test de descendance « polycross », pour d’une part vérifier les hypothèses sur lesquelles repose la sélection backward, et d’autre part, pour proposer une stratégie de sélection innovante. Tout d’abord, la reconstitution du pedigree de 984 individus à l’aide de 63 marqueurs SNPs permet de valider les hypothèses de la sélection backward, et montre que les estimations des paramètres génétiques et des valeurs génétiques maternelles, basées sur l’information d’un pedigree partiel ou complet, diffèrent peu. Puis, les meilleurs descendants du test polycross sont présélectionnés et génotypés pour évaluer la faisabilité d’une stratégie de sélection forward. Enfin, des vergers à graines sont simulés selon différentes stratégies de sélection (backward, forward, mixte) afin de comparer les gains génétiques des variétés améliorées ainsi obtenues.Une stratégie de sélection forward chez le pin maritime permettrait d’accélérer les cycles de sélection et d’augmenter la fréquence des sorties variétales. De plus, le jeu de marqueurs SNPs développé dans cette étude est en cours de valorisation dans différentes étapes du programme d’amélioration. / Maritime pine (Pinus pinaster Ait.) is one of the main economical forest species in France, providing about twenty five percent of the national round wood production. A breeding program, implemented since the 60’s, offers genetically improved varieties for growth and stem straightness.This PhD explores the use of molecular markers in breeding strategies for maritime pine in Aquitaine. Molecular markers were used for pedigree recovery in a polycross progeny trial to test assumptions of backward selection on one hand, and to evaluate the feasibility of a new breeding strategy on the other hand. First, the pedigree of 984 progeny was recovered with 63 SNPs allowing to verify the assumptions of backward selection. We also showed that genetic parameters and maternal breeding value estimates were not much modified by inclusion of full pedigree information. Then, the best progenies in the polycross trial were preselected and genotyped to investigate the possibility of carrying out a forward selection strategy. Finally, establishment of clonal seed orchards were simulated from various breeding strategies (backward, forward, mixed) in order to compare genetic gains from the improved varieties obtained thereby.This study opens new perspectives towards an implementation of forward selection in the French maritime pine breeding program, to speed the selection cycles up and to increase the frequency of variety renewal. Moreover, the set of SNP markers developed is now used in different steps of the breeding program.

Recent climatic extreme events, such as the 2018-2020 drought period, demonstrate that ongoing climate change has a significant impact on our plant ecosystems, resulting in a variety of consequences such as temporal shifts in the growing season, biodiversity loss, and increased tree mortality. Forest ecosystems are especially endangered because the trees’ long lifecycles and their sessile nature impairs the potential to adapt or evade negative impacts in time. Nonetheless, forests are particularly essential because they accomplish key functions in our economic, ecological, and social lives, such as supplying timber, regulating carbon- and water cycling, or providing recreational benefits. Consequently, we need to investigate and comprehend the climatic impact on forest growth at both temporal and spatial scales. Additionally, we must examine the current state of forest vitality and productivity in order to make predictions about forest growth under changing climate. This thesis adds to our understanding of the climate-growth responses of two economically and ecologically important tree species in Central Europe within their low elevational and central distribution ranges: European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.). We examine patterns in climate-driven growth responses at different spatiotemporal scales, ranging from regional to site-specific extents, and from retrospective to near real-time monitoring. In addition, we look at the possibility of employing tree-ring width (TRW) and remote-sensing (RS) data to assess forest vitality and productivity. A deeper knowledge of climate-growth responses in European beech and Scots pine will provide a foundation for decision making and forest management, assisting in the development of a resistant and resilient forest of the future. Chapter 1 provides an overview of the research objectives by situating them in the context of the present state of the art, framing the research objectives, introducing the study design, and finally formulating the research questions for this thesis. For that reason, we employ two tree-ring networks with varying spatial scales: the regional-scale Baltic Sea Network and the site-specific BDF-F-Network. The Baltic Sea Network includes TRW data from 119 pine and 55 beech study sites spread throughout the southern Baltic Sea region, which is distinguished by its predominantly medium nutritious soils, low elevation, and transitional climate ranging from maritime to more continental conditions. The BDF-F-Network, situated within the spatial extents of the Baltic Sea Network, spans along a precipitation gradient in northern Germany. It comprises 54 permanent monitoring plots with substantial information on soil and tree status dating back 40 years. During this PhD project, we extended the exhaustive data base of site-specific information by collecting TRW data for the entire network. As a result, the newly established BDF-F-Network acts as the thesis' centering point. In Chapters 2 and 3, we investigate the spatio-temporal growth responses of beech and pine in their low-elevational and central distribution ranges. Both species exhibit species-specific climate-growth responses with similar patterns at different spatial scales, i.e. when comparing the Baltic Sea and BDF-F-Network. While beech growth is predominantly impacted by summer drought conditions, winter temperature has the greatest impact on pine. We show that the main climatic drivers stay stable across spatial scales, whereas secondary climatic drivers, or climatic drivers with weaker correlations, may vary. Further, we investigate temporal instabilities in climate-growth responses for both networks by applying spatial segregation analyses and comparing growth responses for an early and a later period. We show that during the last few decades, both beech and pine have responded instable to their main climatic drivers, with increased sensitivity to summer drought and winter temperature, respectively. These temporal instabilities are visible at both regional and site-specific scales. Furthermore, Chapter 3 addresses how non-climatic and site-specific soil- and stand characteristics may influence tree growth across the BDF-F-Network's precipitation gradient. We use multilinear regression modeling to examine how stand parameters such as average tree height, diameter at breast height, and TRW differ across the gradient, and if they are impacted by soil water availability or soil type. However, our findings indicate no significant differences in site-specific soil- and stand-characteristics, with the exception of a minor effect on average tree height of European beech. In Chapter 4, we estimate the potential of TRW to assess long-term trends in beech vitality. At 9 sites, we compare the growth trends, climate sensitivities, and drought resistance of 10-20 pairs of vital and non-vital trees that are visually classified by crown condition. Moreover, we use individual heterozygozity as a proxy to determine if differences in growth behavior are caused by genetic predisposition. Surprisingly, growth responses and individual heterozygozity are similar in non-/vital trees. At several study sites, some as vital classified trees exhibit an even greater reduction in TRW than non-vital trees. In summary, we show that TRW is a better proxy for assessing long-term trends in tree vitality, compared to crown condition assessments that are defined by a high year-to-year dynamic. Similarly, Chapter 5 seeks to study the potential of satellite-derived leaf area index (LAI) series to monitor and evaluate forest productivity using European beech as an example. We employ an interdisciplinary approach by combining medium resolution LAI time series derived from two separate satellite sensors (SPOT-VGT/PROBA-V and MODIS), as well as long-term masting monitoring and TRW data from BDF-F-Network sites. By applying site-specific and across-network correlation analysis, we analyze the link between these three target parameters and identify common climatic drivers. While SPOT-VGT/PROBA-V LAI is negatively correlated with masting and positively correlated with TRW, finer resolved MODIS data does not show any significant relationships. We show that RS data from the SPOT-VGT/PROBA-V sensor could be a useful tool for assessing forest vitality and productivity if the LAI time series are sufficiently long. Furthermore, our findings indicate that masting and TRW are both influenced by summer climate conditions, whereas RS LAI appears to be climatically de-coupled. Our findings suggest that RS data has the potential to explore masting and hence forest productivity, but it should always be evaluated in light of the restrictions of different RS products. Finally, Chapter 6 summarizes the preceding chapters' findings and discusses them in the context of the research questions provided at the beginning of the thesis. / Die jüngsten klimatischen Extremereignisse, wie die Dürreperiode 2018-2020, zeigen, dass sich der anhaltende Klimawandel erheblich auf unsere Pflanzenökosysteme auswirkt. Dies führt zu einer Vielzahl weitreichender Folgen, wie der zeitlichen Verschiebung von Wachstumsperioden, Verlusten in der Biodiversität oder einer erhöhten Waldsterblichkeit. Besonders gefährdet sind hierbei Waldökosysteme, da die langen Lebenszyklen von Bäumen eine schnelle Anpassung an sich ändernde Klimabedingungen stark beeinträchtigen. Jedoch erfüllen vor allem Wälder wichtige Funktionen in unserem wirtschaftlichen, ökologischen und sozialen Leben, z. B. als Holzlieferanten, Regulatoren des Kohlenstoff- und Wasserkreislaufs oder auch als Erholungsraum für die Menschen. Dementsprechend ist es unerlässlich die klimatischen Auswirkungen auf das Waldwachstum sowohl auf zeitlicher als auch auf räumlicher Ebene zu untersuchen und zu verstehen. Zudem müssen wir auch den aktuellen Zustand der Vitalität und Produktivität der Wälder überprüfen, um aussagekräftige Prognosen zum Waldwachstum unter dem Einfluss des Klimawandels treffen zu können. Diese Dissertation trägt zu unserem Verständnis der Klimawachstumsreaktionen zweier wirtschaftlich und ökologisch relevanter Baumarten in ihrem ökologisch optimalen Verbreitungsgebiet in Mitteleuropa bei: der Rotbuche (Fagus sylvatica L.) und der Waldkiefer (Pinus sylvestris L.). Hierbei werden die klimabedingten Wachstumsreaktionen auf verschiedenen räumlichen und zeitlichen Skalen untersucht, welchen von regionalen bis standortsspezifischen Ausmaßen und von retrospektiven Analysen bis nahezu Echtzeit-Monitoring reichen. Darüber hinaus erörtert diese Arbeit das Potenzial Jahrringdaten (TRW) als auch Fernerkundungsdaten (RS) zur Bewertung der Vitalität und Produktivität von Wäldern beispielhaft an der Rotbuche zu verwenden. Ein tiefreichendes Verständnis der Klima- Wachstumsreaktionen der Rotbuche und der Waldkiefer bietet somit eine gute Basis um bei Fragen zur zukünftigen Waldbewirtschaftung und der Entscheidungsfindung zu unterstützen, sodass wir einen widerstandsfähigen Wald der Zukunft aufbauen können. Kapitel 1 gibt einen Überblick über diese Dissertation, indem es Forschungsfragen in den Kontext des aktuellen Stands der Wissenschaft einordnet, die Forschungsziele erläutert, das Studiendesign vorstellt und schließlich die Forschungsfragen formuliert. Hierbei verwenden wir zwei Jahrringnetzwerke mit unterschiedlichen räumlichen Ausmaßen: das regionale Baltic Sea Netzwerk und das standortspezifische BDF-F-Netzwerk. Das Baltic Sea Netzwerk umfasst TRW-Daten von 119 Kiefern- und 55 Buchen-Standorten, welche sich über die gesamte südliche Ostseeregion erstrecken. Diese Standorte sind durch überwiegend mittelnährstoffreiche Böden, niedrige Höhenprofile und einem Übergangsklima von maritimen zu kontinentalen Bedingungen charakterisiert. Das BDF-F-Netz erstreckt sich entlang eines Niederschlagsgradienten in Norddeutschland und befindet sich somit innerhalb der geographischen Ausdehnungen des Baltic Sea Netzwerkes. Es umfasst 54 permanente Monitoring-Standorte zu denen umfangreichen Informationen zum Boden- und Baumzustand der letzten 40 Jahre vorliegen. Im Rahmen dieses Dissertationsprojektes wurden die umfassenden standortspezifischeren Informationen mit TRW-Daten für das gesamte Netzwerk ergänzt. Das daraus resultierende BDF-F-Netzwerk bildet somit den Dreh- und Angelpunkt der Dissertation. In den Kapiteln 2 und 3 werden die räumlichen und zeitlichen Wachstumsreaktionen von Rotbuche und Waldkiefer in ihren zentralen Verbreitungsgebieten untersucht. Unabhängig von der räumlichen Skala, sprich beim Vergleich von Standorten beider Netzwerke, zeigen beide Baumarten artspezifische Klimawachstumsreaktionen. Während die Rotbuche primär von Sommertrockenheit beeinflusst wird, ist das Wachstum der Waldkiefer maßgeblich von den Temperaturen im Winter geprägt. Zudem zeigt diese Arbeit, dass die primären Klimatreiber über verschiedene räumliche Skalen hinweg stabil bleiben. Sekundäre Klimatreiber, welche durch schwächeren Korrelationen zwischen Klima und Wachstum charakterisiert sind, können jedoch über geographische Ausbreitungen hinweg variieren. Weiterhin wurden zeitliche Instabilitäten in den Klimawachstumsreaktionen für beide Netzwerke mittels räumlicher Segregationsanalysen und dem Vergleich einer frühen und einer späteren zeitlichen Periode untersucht. Die Ergebnisse zeigen, dass sowohl Rotbuche als auch Waldkiefer Instabilitäten in ihren Hauptklimatreibern aufweisen. In den letzten Jahrzehnten stieg die Sensitivität der Rotbuche auf Sommertrockenheit signifikant an, während die Waldkiefer immer stärker auf Wintertemperaturen reagiert. Diese zeitlichen Instabilitäten können in beiden Netzwerken, sowohl auf überregionalen als auch auf standortortsspezifischer Skala, nachgewiesen werden. Kapitel 3 beleuchtet den Einfluss nichtklimatischer und standortspezifische Merkmale des Bodens und Bestandes auf das Baumwachstum. Hierbei werden entlang des Niederschlagsgradienten des BDF-F-Netzwerks Unterschiede in der durchschnittlichen Baumhöhe, des Brusthöhendurchmesser und TRW mittels multilinearer Regressionsmodellierung untersucht. Zudem werden die Einflüsse der Bodenwasserverfügbarkeit als auch der Bodenart erörtert. Abgesehen von einem marginalen Einfluss auf die durchschnittliche Baumhöhe der Rotbuche bestehen keine signifikanten Unterschiede in den Bestands- und Bodencharakteristika des Standorts. Die zugrundeliegenden Ursachen werden in Hinblick auf Erkenntnisse der aktuellen wissenschaftlichen Literatur und des Studiendesigns des BDF-F-Netzwerkes besprochen. Kapitel 4 untersucht das Potenzial TRW-Daten zu verwenden, um langfristige Trends in der Vitalität der Rotbuche zu bewerten. Hierbei wurden in 9 Beständen 10-20 Baumpaare, bestehend aus je einem vitalen und einem nicht vitalen Baum, visuell nach Kronenzustand klassifiziert. Somit können Unterschiede in den langfristigen Wachstumstrends, der Klimasensitivität und der Trockenheits-resistenz zwischen nicht-/vitalen Individuen analysiert werden. Zudem wird die individuelle Heterozygotie als Proxy für genetische Vielfalt der Rotbuche herangezogen, um genetisch bedingte Unterschiede im Wachstumsverhalten zu beleuchten. Überraschenderweise unterscheiden sich weder die Wachstumsreaktionen noch die individuelle Heterozygotie bei nicht-/vitalen Rotbuchen. Zudem zeigen einige vitale Bäume eine höhere TRW-Reduktion im Vergleich zu nicht vitalen Bäumen. Dementsprechend zeigen die Ergebnisse, dass TRW ein guter Proxy für die Bewertung langfristiger Trends in der Vitalität von Bäumen zu sein scheint, wohingegen Vitalitätsansprachen mittels visueller Abschätzung des Kronenzustands aufgrund einer hohen Jahr-zu-Jahr-Dynamik eine Momentaufnahme der Baumvitalität darstellen. Kapitel 5 erörtert die Frage, inwieweit wir satellitenbasierte Daten (RS) mit mittlerer Auflösung zur Überwachung und Bewertung der Waldproduktivität verwenden können und untersucht dies am Beispiel der Rotbuche. In diesem interdisziplinären Ansatz werden Fernerkundungsdaten des Blattflächenindex (LAI) von zwei Satellitensensoren (SPOT-VGT/PROBA-V und MODIS) mit Daten zum Mastverhalten und der TRW der Rotbuche innerhalb des BDF-F-Netzwerks kombiniert. Durch standortspezifische und netzwerkweite Korrelationsanalysen wird der Zusammenhang dieser drei Zielparameter analysiert und anhand gemeinsamer klimatischer Treiber diskutiert. Während SPOT-VGT/PROBA-V LAI negativ mit Mast und positiv mit TRW korreliert, gibt es keine signifikanten Korrelationen in höher aufgelösten MODIS-Daten. Die Ergebnisse zeigen, dass bei ausreichend langen Zeitreihen SPOT-VGT/PROBA-V-Daten ein nützliches Werkzeug zur Bewertung der Waldvitalität und -produktivität sein können. Darüber hinaus scheint RS LAI klimatisch entkoppelt zu sein, während sowohl Mastverhalten als auch TRW hauptsächlich vom Sommerklima beeinflusst werden. Die Ergebnisse zeigen, dass satellitenbasierte LAI-Daten das Potential besitzen das Mastverhalten und somit die Waldproduktivität zu erfassen und zu analysieren. Jedoch sollten etwaige Interpretationen und Rückschlüsse immer in Bezug zu technologischen und methodologischen Limitationen verschiedener RS-Produkte bewertet werden. Abschließend fasst Kapitel 6 die Ergebnisse der vorherigen Kapitel zusammen und diskutiert sie im Zusammenhang mit den Forschungsfragen, die zu Beginn der Arbeit gestellt wurden.

[pt] Este estudo teórico-experimental tem como objetivo a análise do comportamento até a ruptura de vigas de madeira da espécie Pinus oocarpa reforçadas externamente à flexão com compósitos de base epoxídica reforçados por fibras de vidro e juta. No programa experimental foi investigado o desempenho mecânico do Pinus Oocarpa quando submetido a temperaturas elevadas. Uma tendência à redução do módulo de elasticidade e da resistência à compressão foi verificada com o aumento da temperatura, fato que pode ser comprovado através de análises com difração de raios-x. Ensaios de tração nos compósitos reforçados com fibras de vidro e juta foram realizados demonstrando comportamento frágil, linear-elástico até ruptura. Além disso, vinte e duas vigas, com seção transversal de 10x15cm e 300 cm de comprimento foram ensaiadas à flexão. Essas vigas foram divididas em cinco séries, sendo cinco vigas de referência sem reforço, cinco reforçadas com uma camada de fibra de vidro, seis com três camadas de fibra de vidro, uma com uma camada de fibra de juta e, por fim, cinco com três camadas de fibra de juta. No estudo teórico foi aplicado o modelo básico de seção composta para o regime elástico e dois modelos bilineares elasto-plásticos. A partir dos resultados numéricos e para as considerações adotadas, comparou-se com os valores encontrados experimentalmente concluindo-se que o primeiro modelo é o melhor deles para o dimensionamento. Verificou-se que todas as vigas reforçadas apresentaram um acréscimo de força última variando de 16-26 por cento quando considerados os compósitos de juta e 54-81 por cento para os de vidro em relação às vigas de referência. Verificou-se, também, que, com o acréscimo das fibras ocorreu uma modificação no modo de ruptura, ou seja, as peças continuaram rompendo nas fibras tracionadas, só que com uma pequena plastificação nas fibras comprimidas. Observou-se, também, que os compósitos de fibra de juta alteram consideravelmente a rigidez das peças fletidas mesmo com ganho inferior na resistência. / [en] The work in hand aims the theoretical-experimental investigation of the mechanical behavior until rupture of Pinus oocarpa s wood beams reinforced externally for bending with glass and jute epoxy-based composites. In the experimental program, the mechanical behavior under elevated temperatures of Pinus oocarpa was investigated. A tendency to reduce the elastic modulus and the compressive strength was verified with the increase of the temperature, which was traced back to the x-ray diffraction analysis. Tension tests on glass and jute fiber reinforced composites were performed showing a brittle and linear elastic behavior until rupture. Beside this, twenty two beams, with cross section of 10x15cm and 300 cm of length, was tested. The beams were divided into five groups: five non-reinforced beams, five reinforced beams with one fiberglass layer, six with three fiberglass layers, one with one layer of jute fiber and five with three layers of jute fiber. In the theoretical study, a basic model of the composite section for the elastic range was applied and two bilinear elasto-plastic models. From the comparison of the experimental and theoretical results, it was concluded that the first model is the best one to be applied in project. It was verified that all the reinforced beams presented an increase of the ultimate force varying from 16 to 26 per cent when considering the jute composites and from 54 to 81 per cent for the glass ones. It has been found that, with the addition of glass fibers, a change in the mode of rupture was observed. Without the reinforcement, the beams fractured with pure tension. When the composites were used as external reinforcement, some beams presented a small plastification on the compression zone. It was also observed that the jute fiber composites considerably modified the stiffness of the beams even with a lower gain in the load bearing resistance.

A greenhouse experiment was conducted over a ninety day period to test the effect of different nitrogen fertilizer regimes and several application rates of compounds with gibberellin and cytokinin activity (GA4/7 and BA, respectively) on the growth and development of Pinus brutia var. eldarica. Nitrogen produced no significant effects and this was attributed to its abundance in the potting medium, to begin with. All levels of growth regulators used showed a highly significant effect on vegetative development. A reduction in root collar diameter, shoot elongation, needle nitrogen content and oven-dry weight, was observed, especially when the medium and high hormonal rates were used. Phytotoxicity increased with the increase in concentration of both chemicals. Ba induced a proliferation of adventitious buds along the stem of saplings, but this was accompanied with rapid new top growth and branching at the top only when BA was applied in conjunction with GA4/7.

Thesis (PhD(For))--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Pinus patula is the most intensively planted conifer in the tropics and sub‐tropics. In South Africa Pinus patula plantations are the main saw‐log resource for structural lumber production. Improved intensive silvicultural practices and tree breeding have resulted in marked increases in the rate of growth. To reap the financial benefits of the faster growth, plantation managers are more and more inclined to reduce rotation ages, which inevitably results in the production of higher proportions of juvenile wood at final harvest, and lumber which often does not meet the minimum requirements for stiffness for structural lumber. Knowledge of the variation and the accurate prediction of the mechanical properties of the timber of standing trees can have various benefits for growers and processors of trees. It can be used for tree allocation to different processing facilities, for processing production planning, and to assist tree breeders to screen and select for superior breeding material. The objectives of this study were (1), to examine the within‐ and between‐tree variation in wood properties of young South African grown Pinus patula trees known to have important impacts on the suitability of sawn lumber for structural purposes and (2), to develop empirical prediction models for the flexural lumber properties from standing Pinus patula, based on variables that could be assessed non‐destructively from standing trees. Sample material was obtained from 170 trees (16‐20 years old) established in 17 compartments along the Mpumalanga escarpment of South Africa. A large number of variables which could be obtained non‐destructively from the trees while they were still standing, were measured. The trees were subsequently felled and two logs, 2.1 m in length, were extracted from each tree at two height positions. The 340 logs were processed into 1402 pieces of lumber for further measurements and destructive testing. Results showed that the mean modulus of elasticity measured on edge (MOEedge) was far below the limits set for structural grade softwood timber in South Africa. All the desirable properties for structural lumber improved with distance from the pith with the exception of the 5th percentile value for modulus of rupture (MOR), which was higher at the pith than for the boards processed adjacent to the pith. Boards processed from the lower part of the stem were superior in most of the important properties compared to those higher up in the stem. Separate multiple regression models for predicting the average dynamic MOE (MOEdyn) of individual boards, trees and compartments were developed. The models managed to explain 68%, 60% and 95% of the variation in MOEdyn respectively. The models developed for MOR explained 40% and 42% of variability at board and tree level respectively. At compartment level, 80% of the variation in the 5th percentile MOR value could be explained by the model. Sensitivity analyses showed that site index at base age of 10 years, acoustic time‐of‐flight, wood density and ring width were the most influential variables in the MOE models. The models indicated that tree slenderness during early growth seems to play a major role in determining the dynamic MOE and MOR of lumber. This is in agreement with Euler’s buckling theory and the bending stress theory. Microfibril angle (MFA) and density were measured on radial strips taken from a sub‐sample of trees with the Silviscan 3 technology. The mean microfibril angle per year ring in Pinus patula varied between 7o and 29o. In general MFA decreased with distance from the pith and height above ground level. A multiple regression model including microfibril angle, density and ring width explained 71% of the variation in the dynamic MOE of boards. Sensitivity analysis on the model showed that microfibril angle and density had roughly equal influences on predicting the MOEdyn of Pinus patula boards. / AFRIKAANSE OPSOMMING: Pinus patula is die mees aangeplante naaldhoutspesie in die tropiese en sub‐tropiese areas van die wêreld. Dit is die grootste bron van saagblokke vir die produksie van strukturele hout in SA. Intensiewe boskultuurpraktyke en boomteling het gelei tot ‘n merkbare verhoging in die groeitempo van die spesie. Plantasiebestuurders is gevolglik geneig om rotasie‐ouderdomme te verlaag, wat lei tot ‘n groter persentasie jeughout wat nie aan die minimum styfheidvereistes van strukturele hout voldoen nie. Kennis van die variasie en die akkurate voorspelling van die meganiese eienskappe van staande bome kan voordele inhou vir beide die verbouers en verwerkers van bome. Dit kan byvoorbeeld van hulp wees met die toewysing van bome aan verwerkingsfasiliteite, vir produksiebeplanning, en vir ondersteuning met die keuse van teelmateriaal vir boomtelers. Die doelwitte van hierdie studie was (1), om die binne– en tussenboomvariasie in die houteienskappe, wat ‘n bepalende invloed het op die geskiktheid van jong Suid Afrikaanse Pinus patula bome vir strukturele hout produksie, te ondersoek en (2), om empiriese modelle vir die voorspelling van die buigeienskappe van planke te ontwikkel, gebaseer op veranderlikes wat niedestruktief op staande Pinus patula bome ge‐evalueer is. Monsters vir die studie is verkry vanaf 170 bome (16‐20 jaar oud), geplant in 17 vakke op die Mpumalanga platorand van Suid Afrika. ‘n Groot aantal veranderlikes is nie‐destruktief gemeet op die staande bome waarna die bome gevel is en twee saagblokke, 2.1m in lengte, is op twee hoogte posisies uit elke boom verwyder. Die 340 blokke is verwerk tot 1402 planke vir verdere metings en destruktiewe toetse. Resultate het getoon dat die gemiddelde modulus van elastisiteit gemeet op die dwarskant (MOEedge) aansienlik laer was as wat vereis word vir strukturelegraad hout in Suid Afrika. Al die gewenste eienskappe het toegeneem met afstand vanaf die murg behalwe die 5de persentiel breekmodulus (MOR), wat hoër was vir murgplanke as vir aangrensende planke. Planke afkomstig van die laer dele van die stam het oor die algemeen beter eienskappe gehad as planke afkomstig van die hoër dele. Veelvuldige regressiemodelle kon 68%, 60% en 95% van die variasie in die gemiddelde dinamiese MOE (MOEdyn) op die vlak van onderskeidelik individuele planke, bome en vakke verklaar. Die modelle vir MOR kon 40% en 42% van die variasie op onderskeidelik plank‐ en boomvlak verklaar. Die model vir 5de persentiel MOR van vakke kon 80% van die variasie verklaar. ‘n Sensitiwiteitsanalise het aangetoon dat groeiplekindeks op ouderdom 10, akoestiese vlugtyd, digtheid en jaarringwydte die belangrikste veranderlikes was wat MOEdyn beïnvloed het. Die modelle het aangetoon dat die slankheid van bome tydens vroeë groei vermoedelik ‘n belangrike invloed op die MOEdyn en MOR van planke het. Dit is in ooreenstemming met Euler se knikteorie en die buigsterkteteorie. Die mikrofibrilhoek en digtheid van ‘n steekproef van die bome is gemeet met die Silviscan 3 apparaat. Die gemiddelde mikrofibrilhoek per jaarring het tussen 7 o en 29o varieer. Hierdie variasie was hoofsaaklik afhanklik van boomhoogte en aantal jaarringe vanaf die murg. ‘n Veelvuldige regressiemodel wat mikrofibrilhoek, digtheid en jaarringwydte insluit, kon 71% van die variasie in MOEdyn verklaar. ‘n Sensitiwiteitsanalise op die model het aangetoon dat mikrofibrilhoek en digtheid ongeveer ewe belangrik was wat betref hulle invloed op die voorspelde MOEdyn van Pinus patula planke.

The thesis deals with the ecology of lichens in two contrasting types of forest, epiphytic lichens in old Picea abies forest of the fi re-refugia type and epigeic as well as epixylic lichens in a successional sequence of fire- susceptible Pinus sylvestris forests. Results in five separate papers form the basis for a discussion of general patterns of dispersal, succession and life strategies in lichens. The study sites were located in Medelpad and Väs­terbotten, in the central and northern part of Sweden, respectively. Special attention has been paid to the rare, pendulous, spruce-1ichen Usnea longissima and the coexisting lichen species. U. longissima is largely restricted to north-facing hill slopes covered with old, mesic spruce forest that is characterized by a very long continuity not disturbed by fire. A mar­ked decline in the number of sites with U. longissima was found. The decline was mainly due to the effect of different forestry practices as the species is very sensitive to environmental disturbances. The epiphytic lichen vegetation of six tree species occurring in the spruce forest is described. Clear successional trends with increasing tree size were • obtained for Alectoria sarmentosa, Bryoria fuscescens coll., B. nadvornikiana, Usnea filipendula' and U. subflorida'na, to a lesser extent for Bryoria capii-“" laris while U. longissima had no relationship to tree size or age. TTstudy of the litterfall of macrofragments of epiphytic lichens showed that thallus fragments were dispersed throughout the year with late autumn, winter and early spring as the most critical periods. It is suggested that dispersal through thallus fragmentation is more important in fruticose than in foliose species and that U. longissima has a shorter range of propagule transport than the other species of Alectoria, Bryoria and Usnea studied. The latter proposition was supported through a study of the horizontal patterns of lichen occurrence in the spruce forest. It is shown that the diversity in ground vegetation, after an initial in­crease, declines with succession in the pine forests. A mechanism of succes­sion in ground vegetation is presented which suggest that variations in habi­tat heterogeneity, i.e. the diversity of substrates caused by the initial dis­turbance and the stand development, largely determines diversity changes dur­ing succession. Trends of increasing thallus size, increasing size of asexual reproductive propagules and increased competitive ability with succession formed the basis for recognizing three types of strategies in Cladonia» It is concluded that lichens have features that are compatible with the r-K continuum and that they are variously adapted to both the stability of the substrates and that of the forest as a whole. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1983, härtill 5 uppsatser</p> / digitalisering@umu

This dissertation examined the impact of species, physiological age and spacing on tree form and branching at a Nelder experiment located near Rolleston, Canterbury. Two species were compared, Pinus radiata and Eucalyptus nitens, at a range of stockings from 271 stems/ha to 40,466 stems/ha. Within the P. radiata, two different physiological ages were compared. Stocking and species significantly affected (p-value <0.05) tree height, diameter at breast height (DBH), crown depth, branch mortality, branch angle, branch size and internode length. Only stocking was statistically significant for crown width, and height from the ground was also statistically significant for branch angle and branch mortality. DBH, crown width, crown depth, branch size and branch survival decreased with increasing stocking for both species. Branch angle and average internode length increased as stocking increased for both species, and branch angle and average internode length also increased as you moved away from the base of the tree. DBH, average internode length and branch size were significantly larger for P. radiata across all stockings, however branch mortality and branch angle were significantly larger for E. nitens. Physiological age was not statistically significant for any aspects of tree form or branching examined in this study.

Pinus radiata is the dominant species of the plantations forests in New Zealand. The forest industry in New Zealand is heavily dependant on it. However, Pinus radiata can develop wood quality flaw called 'intra-ring checking'. The checks or splits appear in wood during kiln drying and usually affect the earlywood region of the wood. It lowers value of appearance grade timber leading to huge economic loses for the forest industry. This thesis presents a study that was undertaken as a part of ongoing collaborative work that is being carried out to understand wood quality issues in Pinus radiata, with a vision of improving its wood quality. This study was a part of that effort and was conducted with an aim to gain an insight into intra-ring checking, and the process of xylogenesis in Pinus radiata. The investigations for this study were carried out in two steps. The first step was to understand intra-ring checking. The location of intra-ring checking was determined by observing the checks using various microscopy techniques. Scanning electron microscopy confirmed that checking was as an intercell failure that usually occurs at the cm1/S1 boundary. A comparative study was also conducted to see if the checked wood had some inherent properties that made it more susceptible to checking. It was found that checking could be influenced by tracheid geometry and cell wall thickness. If the wood had large tracheids with thin walls, it was more likely to develop checks during drying. Lignin distribution in the cell wall layers was also seen to play an important role in checking. Lower lignin levels and disruption in the pattern of lignification of the cell wall layers increased the tendency of the wood to develop checks. Similarly, it the tracheids have larger pits then their tendency to check increases. Structural features that disrupt the uniformity of the interlocking pattern of the tracheid such as rays and resin canals could also play a role in checking. Checked wood tends to have more surface area occupied by ray tissue. However, resin canals do not seem to be directly involved in checking, though their arrangement could indicate disturbances during xylogenesis. The second step was to understand the process of xylogenesis in Pinus radiata especially with respect to the influence of auxin and boron on it. Nutrient and organ culture methods were manipulated and successfully used to study xylogenesis. An exhaustive comparative study was carried out to observe and measure selected wood properties. Microscopy and image analysis revealed that auxin and boron changes in the medium led to the alterations in the cell division, expansion and lignification. However, the analysis of the measurements and the observations displayed complex 'between-tree' and 'within-culture variations'. Clear trends did not emerge from the analysis hence, a confident conclusion on the association between auxin, boron and lignification could not be drawn from this organ culture study. The study has added to the knowledge about checking and wood properties associated with it. A new tool of organ culture had been established that can hlep future research on the process of xylogenesis in Pinus radiata.

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.

Time domain properties of 23 tree-ring chronologies derived from a large sample of Douglas-fir and ponderosa pine trees growing in closed-canopy forests of Colorado and New Mexico were analyzed using Box-Jenkins models. A variety of statistical criteria were employed during the identification and validation stages for evaluating the performance of different significant models, and the "best" Box-Jenkins model and its immediate "competitor" were reported for each tree-ring chronology. All series were stationary, and only one was approximately a white noise series. Overall, the ARMA(1,1) model was judged the best for 11 series, and the second for 7 of the remaining 12 series. The AR(2) model was considered the best for 6 series, and the second for 4 of the remaining 17 series. No statistical evidence was found for moving average models, nor for models with more than three different parameters. However, both cyclical (or seasonal) models and third-order autoregressive models with a null second-order parameter were chosen for some series. Fitted models explained from 7 to 51% of the variance of the original ring-index series, with an average of about 22 %. All parameter estimates were positive, and they varied within a relatively small range. From a comparison of all employed criteria, Akaike's Information Criterion (AIC) was the one that performed best in identifying Box-Jenkins models for tree-ring chronologies. Possible distinctions were recognized that would separate the selected models according to species and /or standardization option. Among the 12 chronologies from Colorado sites, all derived using the same standardization option, most Douglas-fir series were best fitted by the ARMA(1,1) model, while most ponderosa pine series were best fitted by the AR(2) model, suggesting a difference in the biological persistence of the two species. On the other hand, most of New Mexico chronologies, developed using various standardization options, were best fitted by the ARMA(1,1) model, and no difference was found between Douglas-fir and ponderosa pine series. Also, models fitted to Colorado chronologies explained a lower amount of variance than those for New Mexico chronologies (averages of 17 versus 29% respectively), and cyclical models were mainly selected for New Mexico series. Although periodicities in Douglas-fir series were probably caused by western spruce budworm outbreaks, similar periodic patterns in ponderosa pine series were more difficult to explain because pine trees in the study area had not been defoliated by that insect. Compared to the original tree-ring chronologies, prewhitened series showed similar short-term growth patterns, reduced long-term growth fluctuations, lower standard deviations, and higher mean sensitivities. Also, cross-correlations between chronologies from the same area usually increased after prewhitening. Since the autocorrelation problem is crucial in analyzing the relationships between different time series, and in removing the biological persistence included in tree-ring chronologies, the Box-Jenkins approach should facilitate the analysis of the dynamic relationships between tree growth and environmental variables.