Mycorrhizal networks (MNs) are fungal hyphae that connect the roots of at least two plants, potentially providing a conduit for interplant resource transfer. Interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) is an obligate ectomycorrhizal (EM) tree species that has high potential to form MNs with neighboring trees because of its receptivity to a diverse community of EM fungi. This MN potential is expected to be greatest among conspecific trees. In this thesis, I determined the influence of MNs formed by residual Douglas-fir trees on interplant carbon transfer and survival, growth, physiology, and EM status of neighboring naturally regenerated and planted Douglas-fir seedlings. To do this, I used MN-restricting treatments and isotope gas-labeling techniques on sites harvested with variable tree retention to investigate how varying: i) proximity to conspecific trees affects EM colonization and performance of planted seedlings; ii) ‘donor’ tree size affects seedling establishment and carbon or nitrogen transfer, and; iii) soil disturbance stress affects net carbon transfer between established seedlings. Because I used physical barriers (i.e., mesh bags) to control for the presence and characteristics of the MN, I also verified the effectiveness of different-sized mesh pores at reducing hyphal connections between plants in the greenhouse. In my experiments, I found that MN-mediated colonization was not the dominant mechanism responsible for EM colonization of planted seedlings; other sources of inoculm (e.g., spores, sclerotia, hyphal fragments) were more important. I found that mature trees not only competed for resources with seedlings but offered some facilitative effects at intermediate distances within their rooting zones. My key finding was that access to a MN with residual trees benefited seedling survival and that this corresponded with increased carbon and nitrogen transfer to seedlings. In addition, I found that there was consistently a net gain in carbon by one seedling in a MN and this net transfer increased with relative growth rate of the receiver seedling. These results indicate that MNs can facilitate interplant carbon transfer and be important in regeneration dynamics in dry Douglas-fir forests.

Proper management of uneven-aged interior Douglas-fir (Pseudotsuga menziesii var. glauca) stands is important for British Columbia’s central and southern interior. These stands constitute one of main components of the operable forest land in these areas, with easy access from main roads and towns. This study focused on the growth of uneven-aged Douglas-fir stands after pre-commercial thinning (spacing), with an impetus to improve upon current management practices. Data were collected from 24 permanent sample plots which were established near Williams Lake, British Columbia in 1989; thinning took place between 1990 and 1991. Three measurements have been made post-treatment: 1993, 1997 and 2004. The plot data were used to analyze different growth responses among three different spacing regimes (standard, 3 m clumped and 5 m clumped spacing) and a control. Analyses were performed at both the stand and tree level. The growth of basal area per ha, quadratic mean dbh, volume per ha and Lorey’s height were used for stand level analyses. At the tree level, dbh, height, basal area and volume were the variables of interest. At the stand level, mortality increased (7.1 to 107.1 stems/ha) and ingrowth decreased (2.4 to 8.6 stems/ha) for the second growth period (1997-2003), compared to the first growth period (5.8 to 107.1 stems/ha and 5.0 to 12.4 stems/ha, respectively). No significant differences in annual growth of quadratic mean dbh, basal area and volume per ha and Lorey’s height were noted between the different spacing regimes and the control. At the individual tree level, the 5 m clumped spacing regime usually had the highest dbh, basal area and volume growth for both growth periods. The one exception was for height growth, when analyzed using mixed-effects modeling, where no significant differences were found. Trees on the other two spacing regimes also had higher growth in dbh, basal area, and volume than trees on the control plots. The positive growth response to the spacing treatments at the single tree level was obtained without a reduction in growth at the stand level. This growth increase will result in the residual trees reaching larger sizes more quickly than they would have with no treatment, leading to improved mule deer winter range habitat and higher timber values.

Mycorrhizal networks (MNs) are fungal hyphae that connect the roots of at least two plants, potentially providing a conduit for interplant resource transfer. Interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) is an obligate ectomycorrhizal (EM) tree species that has high potential to form MNs with neighboring trees because of its receptivity to a diverse community of EM fungi. This MN potential is expected to be greatest among conspecific trees. In this thesis, I determined the influence of MNs formed by residual Douglas-fir trees on interplant carbon transfer and survival, growth, physiology, and EM status of neighboring naturally regenerated and planted Douglas-fir seedlings. To do this, I used MN-restricting treatments and isotope gas-labeling techniques on sites harvested with variable tree retention to investigate how varying: i) proximity to conspecific trees affects EM colonization and performance of planted seedlings; ii) ‘donor’ tree size affects seedling establishment and carbon or nitrogen transfer, and; iii) soil disturbance stress affects net carbon transfer between established seedlings. Because I used physical barriers (i.e., mesh bags) to control for the presence and characteristics of the MN, I also verified the effectiveness of different-sized mesh pores at reducing hyphal connections between plants in the greenhouse. In my experiments, I found that MN-mediated colonization was not the dominant mechanism responsible for EM colonization of planted seedlings; other sources of inoculm (e.g., spores, sclerotia, hyphal fragments) were more important. I found that mature trees not only competed for resources with seedlings but offered some facilitative effects at intermediate distances within their rooting zones. My key finding was that access to a MN with residual trees benefited seedling survival and that this corresponded with increased carbon and nitrogen transfer to seedlings. In addition, I found that there was consistently a net gain in carbon by one seedling in a MN and this net transfer increased with relative growth rate of the receiver seedling. These results indicate that MNs can facilitate interplant carbon transfer and be important in regeneration dynamics in dry Douglas-fir forests.

Proper management of uneven-aged interior Douglas-fir (Pseudotsuga menziesii var. glauca) stands is important for British Columbia’s central and southern interior. These stands constitute one of main components of the operable forest land in these areas, with easy access from main roads and towns. This study focused on the growth of uneven-aged Douglas-fir stands after pre-commercial thinning (spacing), with an impetus to improve upon current management practices. Data were collected from 24 permanent sample plots which were established near Williams Lake, British Columbia in 1989; thinning took place between 1990 and 1991. Three measurements have been made post-treatment: 1993, 1997 and 2004. The plot data were used to analyze different growth responses among three different spacing regimes (standard, 3 m clumped and 5 m clumped spacing) and a control. Analyses were performed at both the stand and tree level. The growth of basal area per ha, quadratic mean dbh, volume per ha and Lorey’s height were used for stand level analyses. At the tree level, dbh, height, basal area and volume were the variables of interest. At the stand level, mortality increased (7.1 to 107.1 stems/ha) and ingrowth decreased (2.4 to 8.6 stems/ha) for the second growth period (1997-2003), compared to the first growth period (5.8 to 107.1 stems/ha and 5.0 to 12.4 stems/ha, respectively). No significant differences in annual growth of quadratic mean dbh, basal area and volume per ha and Lorey’s height were noted between the different spacing regimes and the control. At the individual tree level, the 5 m clumped spacing regime usually had the highest dbh, basal area and volume growth for both growth periods. The one exception was for height growth, when analyzed using mixed-effects modeling, where no significant differences were found. Trees on the other two spacing regimes also had higher growth in dbh, basal area, and volume than trees on the control plots. The positive growth response to the spacing treatments at the single tree level was obtained without a reduction in growth at the stand level. This growth increase will result in the residual trees reaching larger sizes more quickly than they would have with no treatment, leading to improved mule deer winter range habitat and higher timber values.

Mycorrhizal networks (MNs) are fungal hyphae that connect the roots of at least two plants, potentially providing a conduit for interplant resource transfer. Interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) is an obligate ectomycorrhizal (EM) tree species that has high potential to form MNs with neighboring trees because of its receptivity to a diverse community of EM fungi. This MN potential is expected to be greatest among conspecific trees. In this thesis, I determined the influence of MNs formed by residual Douglas-fir trees on interplant carbon transfer and survival, growth, physiology, and EM status of neighboring naturally regenerated and planted Douglas-fir seedlings. To do this, I used MN-restricting treatments and isotope gas-labeling techniques on sites harvested with variable tree retention to investigate how varying: i) proximity to conspecific trees affects EM colonization and performance of planted seedlings; ii) ‘donor’ tree size affects seedling establishment and carbon or nitrogen transfer, and; iii) soil disturbance stress affects net carbon transfer between established seedlings. Because I used physical barriers (i.e., mesh bags) to control for the presence and characteristics of the MN, I also verified the effectiveness of different-sized mesh pores at reducing hyphal connections between plants in the greenhouse. In my experiments, I found that MN-mediated colonization was not the dominant mechanism responsible for EM colonization of planted seedlings; other sources of inoculm (e.g., spores, sclerotia, hyphal fragments) were more important. I found that mature trees not only competed for resources with seedlings but offered some facilitative effects at intermediate distances within their rooting zones. My key finding was that access to a MN with residual trees benefited seedling survival and that this corresponded with increased carbon and nitrogen transfer to seedlings. In addition, I found that there was consistently a net gain in carbon by one seedling in a MN and this net transfer increased with relative growth rate of the receiver seedling. These results indicate that MNs can facilitate interplant carbon transfer and be important in regeneration dynamics in dry Douglas-fir forests. / Forestry, Faculty of / Graduate

Proper management of uneven-aged interior Douglas-fir (Pseudotsuga menziesii var. glauca) stands is important for British Columbia’s central and southern interior. These stands constitute one of main components of the operable forest land in these areas, with easy access from main roads and towns. This study focused on the growth of uneven-aged Douglas-fir stands after pre-commercial thinning (spacing), with an impetus to improve upon current management practices. Data were collected from 24 permanent sample plots which were established near Williams Lake, British Columbia in 1989; thinning took place between 1990 and 1991. Three measurements have been made post-treatment: 1993, 1997 and 2004. The plot data were used to analyze different growth responses among three different spacing regimes (standard, 3 m clumped and 5 m clumped spacing) and a control. Analyses were performed at both the stand and tree level. The growth of basal area per ha, quadratic mean dbh, volume per ha and Lorey’s height were used for stand level analyses. At the tree level, dbh, height, basal area and volume were the variables of interest. At the stand level, mortality increased (7.1 to 107.1 stems/ha) and ingrowth decreased (2.4 to 8.6 stems/ha) for the second growth period (1997-2003), compared to the first growth period (5.8 to 107.1 stems/ha and 5.0 to 12.4 stems/ha, respectively). No significant differences in annual growth of quadratic mean dbh, basal area and volume per ha and Lorey’s height were noted between the different spacing regimes and the control. At the individual tree level, the 5 m clumped spacing regime usually had the highest dbh, basal area and volume growth for both growth periods. The one exception was for height growth, when analyzed using mixed-effects modeling, where no significant differences were found. Trees on the other two spacing regimes also had higher growth in dbh, basal area, and volume than trees on the control plots. The positive growth response to the spacing treatments at the single tree level was obtained without a reduction in growth at the stand level. This growth increase will result in the residual trees reaching larger sizes more quickly than they would have with no treatment, leading to improved mule deer winter range habitat and higher timber values. / Forestry, Faculty of / Graduate

Paleoecological analyses of an alkaline fen in the southern Interior Plateau of British Columbia, Canada were undertaken in association with ancient earth ovens. Local and regional vegetation and natural disturbance regimes were reconstructed using pollen, plant macrofossils and macroscopic charcoal. At White Rock Springs, Artemisia-Poaceae steppe occurred in the early Holocene and the inferred climate from this period was warmer and drier than present. Increasing moisture at 6000 14C yr BP fostered development of open Pinus ponderosa forests surrounding the fen, with Pinus contorta var. latifolia expanding at higher elevations. A slope-wash event likely resulting from root processing activities occurred in the late Holocene that resulted in 13% Asteraceae Tubuliflorae pollen at 2200 ± 80 14C yr BP. Macroscopic charcoal concentrations increased following this disturbance. Shortly after this time a modern open mixed conifer forest with Pseudotsuga menziesii was likely established. A second major ecological disturbance perhaps occurred within the last 200 years as indicated by fluctuating pollen values of P. ponderosa, Poaceae, Asteraceae Liguliflorae and wetland species. The fen’s vegetation history is consistent with regional records, but rapid changes during the late Holocene apparently occurred in response to disturbances. These disturbances are most likely linked to human root food harvesting and earth oven use, and later to ranching. Differentiation of P. ponderosa and P. contorta pollen types reveals intervals of local forest change that were not detected in previous studies. This study is part of a larger research project at Upper Hat Creek Valley including lithics, phytoliths, and patterns of earth oven structure. / Graduate

Western larch (Larix occidentalis Nutt.) is an important component of the montane forest in southeastern British Columbia. It grows in cool-temperate (IDF and ICH zones) and boreal climates (MS zone and, occasionally, ESSF zone). Larch is considered a very shade-intolerant species which can tolerate low light (partial shading) only during the seedling stage (the first 5 growing seasons). Typically, it regenerates after fire in the open on seedbeds exposed by burning. However, to what extent it tolerates low light and how various light environments affect its survival and growth is not known. The objective of our study was to determine the variation in survival and growth of western larch seedlings in relation to light availability and site conditions.

A silviculturist needs to know how productivity of all tree species under management varies with the ecological determinants of site quality, i.e., the environmental factors that directly affect the growth of plants - light, heat, soil moisture, soil nutrients, and soil aeration. A good understanding of this variation is necessary for making biologically viable, speciesand site specific silvicultural decisions. Productivity of a given species is usually measured by site index (top tree height at 50 years at breast height age). Quantified relationships between site index of a given species and ecological measures of site quality provide predictive models for estimating site index for all sites on which the species may grow. Western larch (Larix occidentalis Nutt.) is an important tree species in southern central and eastern British Columbia. It grows mainly in the IDF, ICH, and MS zones on moderately dry through very moist sites and on poor through very rich sites. In view of this relatively wide ecological amplitude, a large variation in productivity could be expected. In the study summarized here, relationships between larch site index and selected ecological measures of site quality were examined, and a site index model using these measures as predictors was developed.

This study examines the influence of climate on tree-ring properties of several major tree species: Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Forbes), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and lodgepole pine (Pinus contorta var. latifolia Dougl. ex Loud.). Our three objectives were to determine how (1) tree-ring properties change along an elevation gradient, (2) short-term climatic influences are correlated with tree-ring properties, and (3) long-term climatic influence on tree-ring properties.