Silvics = knowledge of the life, development and environmental habitats of trees Silviculture = Managing the forest community to produce the maximum amount of usable timber in the shortest time Forest I. Tree crowns meet to produce certain amount of shade II. Some clear space above forest floor, resulting from natural pruning of lower tree branches III. Some accumulation of humus on top of mineral soil IV. Form of trees typical of forest rather than open grown tree form Importance of Forests I. Source of renewable wood products II. Habitat for animals III. Indirectly modify climate A. Insolation, convection reduced B. Humidity increased IV. Important storage place for water in watersheds V. Soil enrichment A. Draw nutrients from lower strata to subsoil and vegetation B. Roots increase porosity of soil matrix C. Humus Plant Ecology = Science dealing with dependence and adaptation of plants to their environment Different tree species react differently to various environments thereby producing different tree communities or forest stands Biotic Factors I. Competition for water and elemental nutrients II. Modification of soil structure and composition III. Modification of insolation IV. Herbivory V. Humal alteration Abiotic Factors I. Air A. Mostly O2 and N2 with smattering of CO2 & other gases B. Pollution such as sulfer dioxide (SO2) II. Light A. Intensity decreases with increasing latitude B. Intensity increases with increasing altitude C. Duration of light important since definite amount of energy and photosynthesis required for each species 1. Shade tolerant 2. Shade intolerant III. Heat A. Each species has specific range with minimum and maximum temperatures B. Temperature decreases with increasing latitutde and altitude C. Large bodies of water act as heat stores thereby modulating temperature fluctuations D. SW to SE facing slopes have higher mean annual temperatures than NW to NE slopes IV. Moisture A. Both soil ant atmospheric moisture can be important 1. Tsuga species inhabit sites with high soil and atmospheric moisture 2. Larix appears to require only high soil moisture B. Atmospheric moisture 1. Ultimate source of percipitation 2. Regulates rates of transpiration C. Soil moisture 1. Solvent for elemental nutrients 2. Regulates soil temperature through evaporation 3. Important for photosynthesis 4. Not all moistue is available to plants A. Ice B. High salt content D. Different species have different moisture requirements 1. Moisture requiring 2. Drought tolerant V. Soil A. Composed of three layers or horizons 1. Litter = slightly decayed plant material 2. Humus = much decayed plant material A. Most important, characteristics depend upon available fungi bacteria, heat, and mositure 3. Mineral = formed via disintegration of bedrock B. Soils are characterized by the relative abundance of particulate matter 1. Coarse sand = 200-2000 nm 2. Fine sand = 20-200 nm 3. Silt = 2-20 nm 4. Clay = >2 nm 5. Loam categories are good agricultural soils since these have pore spaces large enough to permit air and water movement but small enough to retain sufficient water for plant growth. VI. Exposure A. North slopes 1. No full sunlight, rays fall obliquely 2. Winds cool, but not drying 3. Snow melts slowly -> continuous moisture 4. Seed germination most favorable B. East slopes 1. Cool and moist fairly late in spring 2. Vegetation late in starting -> little late frost damage 3. Seed germinatin favorable C. South and West slopes 1. Ground parched by sun and wind 2. Least favorable D. Above generalities vary according to local geography