Although boreal forest management typically results in an increased frequency of even-aged forest stands in managed landscapes, fire history research suggests that much of the natural forest mosaic is composed of stands characterised by multiple cohorts of trees. To aid in the development of multicohort management, I investigated stand structural characteristics and small mammal communities as a function of their tree cohort structures. I also tested key alternatives: stand age, productivity, and tree species composition, as correlates of structural variation and small mammal communities. Results reveal that in mixedwood and black spruce forests, three-dimensional structure of boreal forests is strongly correlated with small mammal community structure, and indicate that tree diameter distribution is a succinct descriptor of such structural variation, performing better than alternative stand characteristics. This represents a new approach to characterising habitat supply as a function of within-stand heterogeneity, contrasting with existing approaches that focus on among-stand characteristics.

Although boreal forest management typically results in an increased frequency of even-aged forest stands in managed landscapes, fire history research suggests that much of the natural forest mosaic is composed of stands characterised by multiple cohorts of trees. To aid in the development of multicohort management, I investigated stand structural characteristics and small mammal communities as a function of their tree cohort structures. I also tested key alternatives: stand age, productivity, and tree species composition, as correlates of structural variation and small mammal communities. Results reveal that in mixedwood and black spruce forests, three-dimensional structure of boreal forests is strongly correlated with small mammal community structure, and indicate that tree diameter distribution is a succinct descriptor of such structural variation, performing better than alternative stand characteristics. This represents a new approach to characterising habitat supply as a function of within-stand heterogeneity, contrasting with existing approaches that focus on among-stand characteristics.

Management and restoration of black oak dominated sand savannas often rely on historic vegetative descriptions (settler accounts, surveyor notes, aerial photographs). It is commonly assumed that fire alone maintains savanna structure and composition, however little information is known about the specific fire frequency needed to maintain these systems. The objective of this study was to quantify and correlate characteristics of stand structure with fire history of the Kankakee Sands savannas in northeastern Illinois. Fire history chronologies were determined through dendrochronological methods from 289 dated fire scars identified on 58 black oak (Quercus velutina) trees located throughout four wooded sites. Tree and woody structure was characterized in 30 circular plots (0.04 hectares) in three sites and 26 circular plots in one site that were placed at 25-meter intervals along randomly established permanent line transects in the summer of 2007. The structure analysis consisted of the development of tree age-size relationships among presently dominant and suppressed trees in relation to fire history. Variations in tree and woody structure were strongly related to fire dynamics among the four study sites. Specifically, components such as tree density (n = 114; r = 0.46; P < 0.0001), basal area (n = 114; r = 0.35; P < 0.0001), and total woody stem density (n = 114; r = 0.42; P < 0.0001) all increased as a function of fire-free interval. In addition, sites with shorter fire-free intervals were associated with a higher percentage of hollow tree boles (n = 104 r = -0.31 P < 0.0015) and visible fire scar wounds (n = 104 r = -0.43334 P < 0.0001). While the results of this study suggest fire had a significant role in structuring these four wooded sites, the data also indicated other historic disturbances coupled with individual site characteristics may be integral components in structuring these dynamic systems. For instance, fire-free intervals less than two years maintained conditions of openness, as was referenced to 1939 historic aerial photographs, but eliminated potential future canopy trees. Under these conditions, a dramatic shift in community structure toward prairie vegetation is likely, as no smaller trees were present to assume canopy dominance. Fire-free intervals greater than two years were associated with transition to closed canopy forests. Therefore, management considerations pertaining to fire with the addition of other historic disturbances, including grazing and or selective cutting, are proposed to balance historic canopy openness and promote regeneration of characteristic savanna species.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(地域研究) / 甲第22560号 / 地博第263号 / 新制||地||99(附属図書館) / 京都大学大学院アジア・アフリカ地域研究研究科東南アジア地域研究専攻 / (主査)教授 竹田 晋也, 教授 安藤 和雄, 准教授 古澤 拓郎, 准教授 小坂 康之 / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM

No description available.

No description available.

No description available.

The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old. Early regeneration failures followed slashburning and the planting of unsuitable species. Currently, the most successful and feasible option for reforesting cutovers is natural regeneration with a mix of the three main tree species, but uncertainties remain about the temporal and spatial pattern of regeneration, changes in species composition, and the time required for stand establishment after cutting. Our study addressed these concerns by examining regeneration patterns on 6 sites that were clearcut 11-12 years prior to sampling and left to regenerate naturally. The sites were located at the lower limits of the zone in the Tetrahedron Range, near Sechelt, at elevations from 1060-1100m.

Central to the issue of harvest feasibility on the outer BC coast (CWHvh) is the question of whether sites, once harvested, can be regenerated, and whether the time period for replacement and subsequent growth is economically and environmentally acceptable. Since low productivity sites have not been harvested in the past, there is a lack of data to answer this question. We tried to provide an answer by assessing regeneration following natural disturbances. Small scale gap disturbances are the norm within old-growth stands. If regeneration is not a problem in gaps, then we have some evidence that regeneration should not be a problem upon implementation of our management practices. The objectives of this study were: (1) to develop baseline information on the mechanisms and the patterns of regeneration across a sequence of forest types; (2) to assess regeneration success with respect to productivity; and (3) to estimate future growth and productivity.