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Sky conditions play an important role in the Earth’s climate system, altering the solar radiation reaching the Earth’s surface and determining the fraction of incoming direct and diffuse radiation. Sky conditions dictate the radiation distribution inside plant canopies and also the carbon dioxide uptake by forests during the growing season. On the long term these diffuse conditions may have a positive influence on forest growth in Northern Britain during the last 50 years. We compared the quantity (amount) and quality (spectral distribution) of direct and diffuse radiation above, inside and below a forest stand under sunny, cloudy and overcast conditions in a thinned Sitka spruce [Picea sitchensis (Bong.) Carr.] forest (28 years, with an leaf area index (LAI) of around 5 m2m-2). Similar radiation properties (sky conditions) were used for analysis of light response and canopy conductance measurements in the same and also in a different spruce forest of the same species (33 years, LAI of around 7 m2 m-2) over the growing season 2008 in order to compare canopy activity under these conditions. In order to integrate short-term and longterm studies, we were looking at how far these conditions are influencing forest growth over several decades. To do so, we used freshly cut tree discs of Sitka spruce from a felled forest (planting year 1953) in southern Scotland and solar direct and diffuse radiation along with other meteorological data from the nearest meteorological station. Our analysis show that the amount and quality of solar radiation is distributed differently inside forest stands under various sky conditions, leading to an enhanced carbon dioxide uptake and canopy stomatal activity under diffuse cloudy and overcast conditions. Furthermore we demonstrated which factors have influenced diffuse radiation distribution over the past 50 years and how these are correlated with forest growth in southern Scotland.

A somatic embryogenic system was created using material from the British Columbia Ministry of Forests and Range’s Sitka Spruce (Picea sitchensis (Bong.) Carr) breeding program for resistance to the white pine weevil (Pissodes strobi Peck.). The goal was to provide a system that could aid in understanding the phenotypic and genotypic variation that exists in these traits. Embryogenic lines were derived from controlled crosses of parental genotypes previously ranked for the abundance of three physical bark traits: sclereid cells, constitutive resin canals and traumatic resin canals. The number of filled seeds per cone from controlled pollinations was low, with a mean of 9.4 ± 6.8 (mean ± SD), compared to open-pollinated material, which had greater than 40 seeds per cone. The mean induction rate (to embryogenic cultures) was 7 %, ranging from 0 % to 56 % by cross. Of 135 genotypes, 88.1 % produced mature embryos. The number of embryos produced varied by culture. Nearly all (44 of 45) genotypes germinated, with a mean germination rate of 80 %. The overall conversion rate of somatic embryos to plants was 5.5 %. A novel method of cryopreservation that used a temperature pretreatment but did not require dimethyl sulfoxide was tested. Embryogenic cultures were recovered from 31 % of genotypes (n = 112). Genotypic and phenotypic variation were observed during each stage of the somatic embryogenic process. This project demonstrated that somatic embryogenesis and cryopreservation can be used to create a system to study phenotypic and genotypic variation in Sitka spruce. / Graduate

Nitrogen (N) fertilization due to atmospheric deposition (NDEP ) may explain some of the net carbon (C) sink (0.6-0.7 Pg y-1) in temperate forests, but estimates of the additional C uptake due to atmospheric N additions (∆C/∆N) can vary by over an order of magnitude (5 to 200 ∆C/∆N). High estimates from several recent studies [e.g. Magnani (2007), Nature 447 848-850], deriving ∆C/∆N from regional correlations between NDEP and measures of C uptake (such as eddy covariance -derived net ecosystem production, or forest inventory data) contradict estimates from other studies, particularly those involving 15N tracer applications added as fertilizer to the forest floor. A strong ∆C/∆N effect requires nitrogen to be efficiently acquired by trees and allocated to high C:N, long-lived woody tissues, but these isotope experiments typically report relatively little (~ 20 %) of 15N added is found above-ground, with less than 5 % of the total 15N applied found in wood. Consequently the high correlation-derived ∆C/∆N estimates are often attributed to co-variation with other factors across the range of sites investigated. However, 15N-fertilization treatments often impose considerably higher total N loads than ambient NDEP , while almost all exclusively only apply mineral 15N treatments to the soil, often in a limited number of treatment events over relatively short periods of time. Excessive N deposition loads can induce negative physiological effects and limit the resulting ∆C/∆N observed, and applying treatments to the soil ignores canopy nitrogen uptake, which has been demonstrated in numerous studies. As canopies can directly take up nitrogen, the chronic, (relatively) low levels of ambient NDEP inputs from pollution may be acquired without some of the effects of heavy N loads, with trees obtaining this N before it reaches the soil, allowing canopies to substitute for, or supplement, edaphic N nutrition. The strength of this effect depends on how much N uptake can occur across the canopy under field conditions, and if this extra N supplies growth in woody tissues such as the stem, as well as the canopy. Similarly, such mineral fertilizer isotope trace experiments are also unable to trace N in the decomposing litter and humus layers of the soil, which even under heavy NDEP loading contribute most of the N utilised for forest growth. Recent literature suggests that some organic (early decomposition) forms of N may be taken up by roots. If this litter N is not retained or distributed in the same way as mineral fertilizers, its contribution to plant nutrition and ∆C/∆N may need to be reassessed under nitrogen deposition. We tested some of these assumptions in the nursery and the field. In order to facilitate litter 15N tracing, we conducted an experiment injecting large trees with 15N-NH4NO3 to create 15N-labelled litter, tracing the applied isotope into a full harvest of the canopy. Such labelled litter substitute was used to replace the litter layer in a Sitka Spruce plantation (Picea sitchensis L. (Bong.)), where the fate of this 15N from litter decomposition in the soil system was compared against the fate of 15N in deposition. Similarly, in potted Sitka Spruce saplings, we used combination treatments of 15N-labelled litter, soil-targeted 15N-deposition, and canopy targeted 15N-deposition, investigating 15N return in different age classes of above and below ground biomass. We found that i) 15N recovery in canopies (needles and branches) in our injected trees was almost all of the injected 15N five months after injection, ii) canopy application of NDEP led to 60 % 15N return in above-ground parts of saplings compared to 21 % in soil applications and iii) a litter-derived 15N source was retained 55 % more in topsoil, and 36 % more in roots, than a similar deposition 15N source applied as mineral fertilizer. We discuss the implications of such findings in the context of 15N return in different plant organs and ecosystem pools, seasonal variation in N content, and overall inferences of a forest ∆C/∆N effect. Our results suggest that the total ∆C/∆N effect driven by a high N sequestration from canopy uptake in wood is ~ 114:1, more than double that of 15N tracer experiments but not as high as upper estimates from correlative studies, and that litter-derived organic N is better retained in trees and soils in excess of similar amounts of mineral 15N from deposition. Existing forest 15N-fertilization experiments could under-estimate the overall ∆C/∆N effect of atmospheric N deposition.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 88-102).

Thesis (Ph. D.)--University of British Columbia, 1999. / Includes bibliographical references (leaves 172-180).

Extensive areas of Sitka spruce plantations established during the last 15 years on the CH-phase of the salal-moss ecosystem association on northern Vancouver Island are presently exhibiting symptoms of severe chlorosis and growth check. Investigations into the poor performance of these plantations are described in this thesis. Comparisons of the soil nutrient levels between this poorly productive CH-phase and the adjacent highly productive HA-phase were made. In addition, fertilization screening trials were established in order to identify possible limiting nutrients and determine the potential responsiveness of Sitka spruce to fertilization. Soil samples were collected over an age sequence of cutovers from both phases in order to compare differences in the soil nutrient status and to determine the effects of time since harvesting on N mineralization rates. Significantly greater amounts of total and available P and total, KC1 extractable, and mineralizable N (p=.01) were found in the mineral soil and humus of the HA-phase. The mineral soil of the HA-phase also had significantly higher (p=.05) concentrations of exchangeable K. In addition, this phase had a significantly lower (p=.01) C/N ratio. Although significant differences were noted in the mineral nutrient composition of the two phases, in all cases (with the possible exception of mineralizable N), the absolute differences between the two phases did not appear large enough to account for the dramatic differences in productivity. Harvesting plus slashburning appears to have had little effect on the rates of N mineralization in the humus or mineral soil of the HA-phase. However, in the CH-phase harvesting plus slashburning has had a significant influence on the mineralization rates of the humus but not of the mineral soil. Harvesting initially resulted in a significant (p=.05) increase in the mineralization rates, however, within five years they returned to levels comparable to that of the control. Fertilization screening trials were established in five Sitka spruce plantations ranging in age from 8 to 14 years. All plantations were growing on the CH-phase and were exhibiting symptoms of chlorosis and growth check. Changes in the first-year needle dry-weight, needle nutrient composition, and leader growth were monitored. Treatments for these trials consisted of a N, P, K factorial experiment, and one separate treatment of a complete nutrient mixture. Each treatment was replicated seven times in each of the five plantations. N or N plus K fertilization resulted in a 10% increase in needle dry-weight and a 25 to 30% increase in first-year leader growth response over that of the control. P fertilization had a strong synergistic effect and when added in combination with N or N plus K resulted in a needle dry-weight increase of 40 to 41% and a leader growth increase of 78 to 83%. A limited sample of naturally occurring hemlock in some of the plots exhibited similar trends, although leader growth increases were somewhat greater. Fertilization with P and K, alone or together, had no effect on leader growth or needle weight despite the severe deficiencies of these two elements. However, P had a positive influence on the uptake of N, K, Ca and Mg, whereas K positively affected Ca and depressed Mg. After N fertilization, foliar N concentrations increased dramatically, ranging from a mean of 3.2% for the lowest (200 kg N/ha) application rate to 4.1% for the highest (400 kg N/ha) application rate. The high foliar N concentrations had a significant negative influence on foliar K concentrations. This decline in K concentrations could only partially be attributed to a growth dilution effect and occurred whether or not K was added. A similar effect on P, Ca or Mg was not noted. The high N concentrations also appeared to have had a negative influence on both needle weight and leader growth as there was a tendency for the response of both to decline as N concentrations increased. There were significant differences in both leader growth and needle weight responses between some of the plantations, but treatments receiving both N and P fertilizers consistently gave the greatest responses. The individual treatment, however, which gave the greatest and most consistent overall response was that containing all macro- and micro-nutrients. Results from this study indicate that the poor performance of Sitka spruce plantations established on the CH-phase of the salal-moss ecosystem is partially due to a severe N and P deficiency. These deficiencies are associated with the complete invasion of these cutovers by salal. It has also been shown that the Sitka spruce in these plantations would be highly responsive to N and P fertilization. Although K does not appear to limit growth and no apparent benefits were gained from K fertilization, a severe N induced K deficiency is likely. / Forestry, Faculty of / Graduate

This thesis is a case study using paleoethnobotanical analysis of Kilgii Gwaay, a 10,700-year-old wet site in southern Haida Gwaii to explore the use of plants by ancestral Haida. The research investigated questions of early Holocene wood artifact technologies and other plant use before the large-scale arrival of western redcedar (Thuja plicata), a cultural keystone species for Haida in more recent times. The project relied on small-scale excavations and sampling from two main areas of the site: a hearth complex and an activity area at the edge of a paleopond. The archaeobotanical assemblage from these two areas yielded 23 plant taxa representing 14 families in the form of wood, charcoal, seeds, and additional plant macrofossils. A salmonberry and elderberry processing area suggests a seasonal summer occupation. Hemlock wedges and split spruce wood and roots show evidence for wood-splitting technology. The assemblage demonstrates potential for site interpretation based on archaeobotanical remains for the Northwest Coast of North America and highlights the importance of these otherwise relatively unknown plant resources from this early time period. / Graduate / cohenjenny2@gmail.com