Forest Regeneration Chapters 7 & 10 Smith, et al. Forest Regeneration ! "Trees live long, but not forever so the time comes when they naturally are, or, must be, replaced by new ones. ! "Regeneration plays such a prominent role in silviculture that most silvicultural systems are named for their method of regeneration 2 Regeneration or Reproduction Method “ a process or procedure by which a stand is established or renewed ” ! "Two main objectives ! "Free up growing space (either partially or totally); translates into removing some of mature trees ! "Create environment for establishment of new ! "Other included considerations ! "Treatments of vegetation, slash, or soil to create and maintain conditions favorable to the establishment and early growth of regeneration 3 Two types of regeneration or reproduction ! "Natural ! "Establishing and releasing seed or vegetative sprouts (propagules) originating from sources within or adjacent to the stand being regenerated ! "Artificial ! "Regeneration is artificially seeded or planted, and planted trees can be either from natural origin dug from elsewhere in the forest or grown in seedling nurseries or greenhouses 4 Artificial Regeneration ! "Crucial decision and investment ! "Site preparation and species match ! "Planting / Direct seeding 5 Artificial Regeneration ! "Planting stock ! "bare-root seedlings ↑ light, easy transportation and cheaper ↓ planting can be done only in short periods of time ! "containerized seedlings ↑ quick root-soil contact, can be grown faster, greater uniformity makes planting cheaper, less seed is used ↓ more costly to transport ! "vegetative propagation ↑ genetic qualities are perpetuated, easier and faster establishment if species forms roots readily, reproduce several individuals from a single one ↓ no root system (some planting limitations), few species 6 Artificial Regeneration ! "Size of plants ! "“bigger is not necessarily better!” ! "large planting stock vs. small planting stock ! "Season of planting ! "Breaking of dormancy - Active root elongation period ! "Temperature and moisture ! "Site preparation for improvement of site ! "Reduction of competing vegetation ! "Drainage of water ! "Placement of seedlings 7 Methods of planting ! "Manual or hand planting ! "compression methods: bar-slit (sandy soils) , grub-hoe-slit (stony or clay soils) ! "dug-hole methods (when previous methods fail): side-hole, center-hole, wedge ! "uniform holes can be made using special devices for containerized seedlings (uniform size & shape) ! "Mechanized planting (mostly compression method) ! "flat or gently sloping sites, stump free (abandoned agricultural fields) ! "Usually more effective and cheaper ! "Afforestation 8 Density of plantations ! "Important decision ! "Good control of initial density and spatial arrangement ! "Best to envision the kinds of trees wanted in the stand late in the rotation and work backward from this goal - tendency to think how many trees will be needed to achieve early occupancy of the growing space ! "High density vs. low density → site and objective of production ! "Spatial arrangement: square, hexagonal, staggered, “random,” clumped 9 Plantation protection ! "Plantations require a large investment → losses represent a much larger waste of money compared to natural regeneration ! "Part of the cost of artificial regeneration goes towards protection ! "Damaging agents: wild animals (rodents, browsing, ants, etc) and competing vegetation (woody plants) 10 Direct seeding ! "Requires ! "Adequate seed supply ! "Seed treatment (often for germination) ! "Control of seed-eating animals ! "Favorable site and seedbed conditions ! "Moisture during germination (rain) ! "Site factors and site preparation define the feasibility of the method ! "Types: broadcast or strip and spot seeding 11 Natural regeneration and disturbance ! " Natural succession and development of new stands proceeds in one of two ways ! " Advance regeneration (already established survivors) ! " Germination of seeds ! " Once established, woody perennials usually command growing space so tenaciously that only the death of some of them can make vacancies large enough for the establishment of new ones ! " Disturbance, particularly lethal, figures prominently in the ecology of natural regenerative processes 12 Natural regenerative disturbance ! "Fire is most common natural disturbance ! "Ignited by lightning, volcanoes, spontaneous ! "Kills small trees most efficiently, so old stands are killed from the bottom upwards ! "Favors the return of two major categories of species ! "Those that sprout from roots or bases of fire girdled stems ! "Species germinating from small, wind-blown seeds adapted to germinate on mineral soil surfaces bared by fires 13 Adaptations to fire (more examples) ! " Species w/hard-coated seeds that survive long periods in the forest floor, springing up after fires, such as Cherries and Ribes shrubs ! " Sprouting species, mainly angiosperms (broad- leaved trees) and some conifers such as pitch pine and coast redwood ! " Light-seeded species that thrive on seedbeds of bare mineral soil exposed by fire but not outstandingly resistant to fire (e.g., alder, cottonwood, poplar) 14 Adaptations to fire (some examples) ! " Closed-cone pines, such as jack pine in the Lake States, lodgepole pine and Monterey in the west – regeneration occurs after a crown fire has killed the old crop, exposed mineral soil, and opened the cones 15 Adaptations to fire (ya example) ! " Species with sufficiently fire-resistant bark to withstand burning at intervals throughout an entire single generation, like the hard pines of the South, such as longleaf, loblolly, and shortleaf, and ponderosa pine in the northwest and west 16 Kinds and severity of disturbances ! "Geologic, erosional events are the most severe kind of natural disturbance 17 Kinds and severity of disturbances ! "Geologic, erosional events are the most severe kind of natural disturbance ! "E.g., landslides, melting of glaciers, formation of new land by water, wind, volcanism ! "Ecologically, true primary succession occurs after these events ! "Ordinarily, herbaceous vegetation colonizes these areas, though some tree species can also, such as true poplars, alders, some others ! "SELDOM wise to imitate this with silviculture, but foresters are often called upon to re-vegetate these areas as well as strip mines, or such areas caused by other events 18 Kinds and severity of disturbances ! "Next most severe is a hot fire that burns large amounts of dead fuel created by blow-downs or pest outbreaks 19 Kinds and severity of disturbances ! "Next most severe is a hot fire that burns large amounts of dead fuel created by blow-downs or pest outbreaks ! "Some fires can burn so hot as to be almost as lethal as landslides, but after fire organic matter usually remains in the soil ! "A few silvicultural techniques artificially create similar disturbances, leaving mostly bare soil with organic matter intact, freeing all the growing space for establishment of new vegetation from seed or other methods 20 Kinds and severity of disturbances ! "Next most severe are “releasing disturbances” caused by wind or pests of large trees that kill forests from the top down, sparing most plants in lower strata ! "Species adapted to such disturbances have foliage constructed and displayed in ways that make them tolerant to shade ! "These species may exist as seedlings or saplings for many years beneath old stands, retaining the capacity for rapid height growth whenever some lethal event releases them ! "Tend to be limited to sites and regions that are continuously moist enough to reduce exposure to fire or drought stress 21 Kinds and severity of disturbances ! "Natural disturbances are not uniform in severity, type, or extent 22 Kinds and severity of disturbances ! "Natural disturbances are not uniform in severity, type, or extent ! "Differences are degree of exposure of mineral soil, extent of freedom from root competition, intensity of solar radiation ! "Pioneer communities are the result of catastrophic disturbances ! "Late-successional communities result from a long series of frequent, light, “releasing” disturbances 23 Environment of the microsite ! "The first few weeks in the life of a seedling are the most dangerous for its survival ! "Seedlings respond to light, water, carbon dioxide, chemical nutrients, and biotic influences (regardless of the name of any silvicultural treatments) 24 Environment of the microsite - Water loss ! "Water is lost to the atmosphere by direct evaporation from the uppermost layers of soil and organic material ! "Loose materials lose water so fast they are seldom hospitable for plants ! "Direct evaporation explains the loss of water from the top layers of soil when there are no roots (capillary action) ! "Shade and mulching can greatly slow down direct evaporation losses 25 Environment of the microsite - Surface Temperature ! " Survival of new unshaded seedlings depends heavily on physical processes dissipating solar energy load ! " Reflection, convection, conduction, evaporation, and outgoing re-radiation are the processes that take heat energy away from absorbing surfaces of plants ! " Shading is the most important physical process that is subject to silvicultural manipulation ! " Chlorophyll reflects heat energy (longwave infrared radiation) to some extent, but opaque objects like rocks and trees are most effective in reflecting harmful radiation away from seedlings 26 Environment of the microsite - Light ! " Light regimes beneath