A new one-dimensional heat conduction model for predicting stem heating during fires is presented. The model makes use of moisture and temperature dependent thermal properties for bark and wood. Also, the thermal aspects of the processes of bark swelling, desiccation, and devolatilization are treated in an approximate fashion. Simulation with a surface flux boundary condition requires that these phenomena be accounted for. Previous models have used temperature-time boundary conditions, which prevents them from being directly coupled to fire behavior models. This model uses a flux-time profile for its boundary condition, making it possible to eventually couple it to fire behavior models. Cambial mortality predictions are made through the incorporation of a cell mortality model. The model was developed and validated with laboratory experiments on four species.

We investigated how fire severity impacts the survival and response (sprouting/seeding) of multiple species in the Santa Cruz Mountains of coastal California, including coast redwood (Sequoia sempervirens), Douglas-fir (Pseudotsuga menziesii), tanoak (Lithocarpus densiflorus), and Pacific madrone(Arbutus menziesii). During August 2009 the Lockheed Fire burned nearly 3,160ha of mixed-conifer stands with variable severity. Data from 37 Continuous Forest Inventory (CFI) plots were collected immediately before and for 2 successive years following the 2009 Lockheed Fire. This research entails three objectives. First, we quantified post-fire mortality of trees that vary in species, size, and fire severity. Second, data was quantified for post-fire response (sprouting, seeding) of those three tree species in areas of varying fire severity. Third, we developed logistic regression models that predict post-fire mortality and response for each of the three species. Understanding the relationship between burn severity, mortality and regeneration can allow for better post-fire predictive services. This research can support forest managers in post-fire management decisions to facilitate long-term sustainability and protection of environmental infrastructure within coast redwood/Douglas-fir forests.

Yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) forests of coastal British Columbia are apparently experiencing decline in a manner similar to that observed in southeastern Alaska. In this pilot study, we collect tree-ring data from live and standing dead yellow-cedar trees from four declining sites on the North Coast of British Columbia. We use this data to compare growth patterns at our sites to those of yellow-cedar trees at non-declining and declining sites in southwestern British Columbia and southeastern Alaska and, in addition, to assess the possibility of reconstructing yellow-cedar population dynamics in declining stands using dendrochronology. We found coherent growth patterns (i.e. marker years and periods of suppression) among yellow-cedar chronologies from non-declining and declining sites across a broad geographic range as well as unique growth patterns between our chronologies from declining sites and those from declining sites in nearby Alaska. Using outer-ring dates of increment cores, we were able to estimate time since death of decade- to century-old standing dead yellow-cedar trees, although the precision of the estimates was influenced by partial cambial mortality and erosion of outer rings. Our results provide baseline dendrochronological information that will be useful for planning future studies that assess growth-climate relations and reconstruct the long-term population dynamics of yellow-cedar in declining stands.

No description available.

There is research of regularity of free tree mortality in various age pine stands, growing in Nbl places in master work. Presented this process’s characteristics- amounts of mortality by the number and volume of the tree. We used absolute and relational parameters of free tree mortality. An object of work- 20-140 years old pine stands, which is pure, conditionally average growing in Nbl places. Long-time investigation involved pine of the Jonava district and Berezina reserve (Belarus). Information involved free mortality from various literary sources. Aim- fined a regularity of free tree mortality. A method of work- Barrel method of forestry research was used in outdoor work’s. Inventory of barrel research was repeated 2-3 times in 4-7 years. Without our got information analyze from barrel research we used a method of met analyze, when various authors information of free tree mortality is united in one based object by the source of literature. Results of work- Tree mortality research involved 20-140 years old pine, growing in Nbl places. Our investigation and results analysis shows 2-5% trees mortality (per year) registered in pine samplings; 0,3-6% - in mide-aged pine stands; 1-5% - in premature stands; 5-6% trees mortality in mature stands. Average of size of trees mortality equal: in pine samplings- 4,2 m3/ha per year, in mide-aged stands - 2,7 m3/ha per year, in premature forests - 2,6 m3/ha per year, in mature stands - 2,7 m3/ha per year. Our appointed average and... [to full text]

Bringing together field-based empirical studies, a simulation modelling experiment, and a critical analysis of the natural disturbance emulation paradigm, this thesis evaluates partial harvesting in the black spruce boreal forest. Forest management in Ontario is required to emulate natural disturbances, but in regions of the boreal forest where fire cycles are long, regulated even-aged management by clearcutting has truncated forest age-class distributions. Partial harvesting has been proposed as a means to maintain the structural complexity and biodiversity associated with old forests while allowing continued timber production. Despite the potentially important role of partial harvesting in a strategy for sustainable boreal forest management, little research has examined post-harvest stand development, a critical determinant both of habitat and timber supplies.I used a chronosequence approach in combination with dendroecological techniques, a neighbourhood modelling framework, and maximum likelihood statistical methods to quantify stand dynamics over the first decade after partial harvest in the black spruce (Picea mariana) boreal forest of northeastern Ontario, Canada. Residual trees displayed large but time-lagged growth responses to partial harvest. The largest responses were found in young trees, while old trees were largely unable to react to improved post-harvest resource availability. Growth responses were offset by elevated rates of residual-tree mortality, which peaked in the first year after harvest at nearly 13 times the pre-harvest level. Proximity to harvest machinery trails severely escalated the risk of mortality for residual trees. Considering growth and mortality responses together in a forest simulator model, I found that stand development proceeded most rapidly where skidding intensity was reduced and retention areas were aggregated. Given appropriate prescriptions, my results indicate that partial harvesting can be a viable silvicultural option for black spruce boreal forests. However, the ability of partially harvested stands to emulate natural disturbance is questionable, particularly given the strong influence of harvest machinery impacts on post-harvest stand development. I argue that the natural disturbance emulation framework has important flaws and falls short of a justifiable approach for forest management in Ontario.

Bringing together field-based empirical studies, a simulation modelling experiment, and a critical analysis of the natural disturbance emulation paradigm, this thesis evaluates partial harvesting in the black spruce boreal forest. Forest management in Ontario is required to emulate natural disturbances, but in regions of the boreal forest where fire cycles are long, regulated even-aged management by clearcutting has truncated forest age-class distributions. Partial harvesting has been proposed as a means to maintain the structural complexity and biodiversity associated with old forests while allowing continued timber production. Despite the potentially important role of partial harvesting in a strategy for sustainable boreal forest management, little research has examined post-harvest stand development, a critical determinant both of habitat and timber supplies.I used a chronosequence approach in combination with dendroecological techniques, a neighbourhood modelling framework, and maximum likelihood statistical methods to quantify stand dynamics over the first decade after partial harvest in the black spruce (Picea mariana) boreal forest of northeastern Ontario, Canada. Residual trees displayed large but time-lagged growth responses to partial harvest. The largest responses were found in young trees, while old trees were largely unable to react to improved post-harvest resource availability. Growth responses were offset by elevated rates of residual-tree mortality, which peaked in the first year after harvest at nearly 13 times the pre-harvest level. Proximity to harvest machinery trails severely escalated the risk of mortality for residual trees. Considering growth and mortality responses together in a forest simulator model, I found that stand development proceeded most rapidly where skidding intensity was reduced and retention areas were aggregated. Given appropriate prescriptions, my results indicate that partial harvesting can be a viable silvicultural option for black spruce boreal forests. However, the ability of partially harvested stands to emulate natural disturbance is questionable, particularly given the strong influence of harvest machinery impacts on post-harvest stand development. I argue that the natural disturbance emulation framework has important flaws and falls short of a justifiable approach for forest management in Ontario.

Climate-triggered forest disturbances are increasing either by drought or by other climate extremes. Droughts can change the structure and function of forests in long-term or cause large-scale disturbances such as tree mortality, forest fires and insect outbreaks in short-term. Traditional approaches such as dendroclimatological surveys could retrieve the long-term responses of forest trees to drought conditions; however, they are restricted to individual trees or local forest stands. Therefore, multitemporal satellite-based approaches are progressing for holistic assessment of climate-induced forest responses from regional to global scales. However, little information exists on the efficiency of satellite data for analyzing the effects of droughts in different forest biomes and further studies on the analysis of approaches and large-scale disturbances of droughts are required. This research was accomplished for assessing satellite-derived physiological responses of the Caspian Hyrcanian broadleaves forests to climate-triggered droughts from regional to large scales in northeast Iran. The 16-day physiological anomalies of rangelands and forests were analysed using MODIS-derived indices concerning water content deficit and greenness loss, and their variations were spatially assessed with monthly and inter-seasonal precipitation anomalies from 2000 to 2016. Specifically, dimensions of forest droughts were evaluated in relations with the dimensions of meteorological and hydrological droughts. Large-scale effects of droughts were explored in terms of tree mortality, insect outbreaks, and forest fires using field observations, multitemporal Landsat and TerraClimate data. Various approaches were evaluated to explore forest responses to climate hazards such as traditional regression models, spatial autocorrelations, spatial regression models, and panel data models. Key findings revealed that rangelands’ anomalies did show positive responses to monthly and inter-seasonal precipitation anomalies. However, forests’ droughts were highly associated with increases in temperatures and evapotranspiration and were slightly associated with the decreases in precipitation and surface water level. The hazard intensity of droughts has affected the water content of forests higher than their greenness properties. The stages of moderate to extreme dieback of trees were significantly associated with the hazard intensity of the deficit of forests’ water content. However, the stage of severe defoliation was only associated with the hazard intensity of forests’ greenness loss. Climate hazards significantly triggered insect outbreaks and forest fires. Although maximum temperatures, precipitation deficit, availability of soil moisture and forest fires of the previous year could significantly trigger insect outbreaks, the maximum temperatures were the only significant triggers of forest fires from 2010‒2017. In addition to climate factors, environmental and anthropogenic factors could control fire severity during a dry season. The overall evaluation indicated the evidence of spatial associations between satellite-derived forest disturbances and climate hazards. Future studies are required to apply the approaches that could handle big-data, use the satellite data that have finer wavelengths for large-scale mapping of forest disturbances, and discriminate climate-induced forest disturbances from those that induced by other biotic and abiotic agents. / Klimagbedingte Waldstörungen nehmen entweder durch Dürre oder durch andere Klimaextreme zu. Dürren können langfristig die Struktur und Funktion der Wälder verändern oder kurzfristig große Störungen wie Baumsterben, Waldbrände und Insektenausbrüche verursachen. Traditionelle Ansätze wie dendroklimatologische Untersuchungen könnten die langfristigen Reaktionen von Waldbäumen auf Dürrebedingungen aufzeigen, sie sind aber auf einzelne Bäume oder lokale Waldbestände beschränkt. Daher werden multitemporale satellitengestützte Ansätze zur ganzheitlichen Bewertung von klimabedingten Waldreaktionen auf regionaler bis globaler Ebene weiterentwickelt. Es gibt jedoch nur wenige Informationen über die Effizienz von Satellitendaten zur Analyse der Auswirkungen von Dürren in verschiedenen Waldbiotopen. Daher sind weitere Studien zur Analyse von Ansätzen und großräumigen Störungen von Dürren erforderlich. Diese Forschung wurde durchgeführt, um die aus Satellitendaten gewonnenen physiologischen Reaktionen der im Nordosten Irans gelegenen kaspischen hyrkanischen Laubwälder auf klimabedingte Dürren auf lokaler und regionaler Ebene zu bewerten. Auf der Grundlage der aus MODIS-Daten abgeleiteten Indizes wurden die 16-tägigen physiologischen Anomalien von Weideland und Wäldern in Bezug auf Wassergehaltsdefizit und Grünverlust analysiert und ihre Variationen räumlich mit monatlichen und intersaisonalen Niederschlagsanomalien von 2000 bis 2016 bewertet. Insbesondere wurden die Dimensionen der Walddürre in Verbindung mit den Dimensionen der meteorologischen und hydrologischen Dürre bewertet. Großräumige Auswirkungen von Dürren wurden in Bezug auf Baumsterblichkeit, Insektenausbrüche und Waldbrände mit Hilfe von Feldbeobachtungen, multitemporalen Landsat- und TerraClimate Daten untersucht. Verschiedene Ansätze wurden ausgewertet, um Waldreaktionen auf Klimagefahren wie traditionelle Regressionsmodelle, räumliche Autokorrelationen, räumliche Regressionsmodelle und Paneldatenmodelle zu untersuchen. Die wichtigsten Ergebnisse zeigten, dass die Anomalien von Weideland positive Reaktionen auf monatliche und intersaisonale Niederschlagsanomalien aufweisen. Die Dürren in den Wäldern waren jedoch in hohem Maße mit Temperaturerhöhungen und Evapotranspiration verbunden und standen in geringem Zusammenhang mit dem Rückgang von Niederschlägen und des Oberflächenwasserspiegels. Die Gefährdungsintensität von Dürren hat den Wassergehalt von Wäldern stärker beeinflusst als die Eigenschaften ihres Blattgrüns. Die Stufen mittlerer bis extremer Baumsterblichkeit waren signifikant mit der Gefährdungsintensität des Defizits des Wassergehalts der Wälder verbunden. Das Ausmaß der starken Entlaubung hing jedoch nur mit der Gefährdungsintensität des Grünverlustes der Wälder zusammen. Die Klimagefahren haben zu deutlichen Insektenausbrüchen und Waldbränden geführt. Obwohl Maximaltemperaturen, Niederschlagsdefizite, fehlende Bodenfeuchte und Waldbrände des Vorjahres deutlich Insektenausbrüche auslösen konnten, waren die Maximaltemperaturen die einzigen signifikanten Auslöser von Waldbränden von 2010 bis 2017. Neben den Klimafaktoren können auch umweltbedingte und anthropogene Faktoren den Schweregrad eines Brandes während einer Trockenzeit beeinflussen. Die Gesamtbewertung zeigt Hinweise auf räumliche Zusammenhänge zwischen aus Satellitendaten abgeleiteten Waldstörungen und Klimagefahren. Weitere Untersuchungen sind erforderlich, um Ansätze anzuwenden, die mit großen Datenmengen umgehen können, die Satellitendaten in einer hohen spektralen Auflösung für die großmaßstäbige Kartierung von Waldstörungen verwenden und die klimabedingte Waldstörungen von denen zu unterscheiden, die durch andere biotische und abiotische Faktoren verursacht werden.