Dickinson Ch7, McComb Ch8 Notes
Dickinson Chapter 7
Managing Forests for Wildlife
Wildlife communities are influenced by abiotic conditions (climate, topography, soils) and habitat conditions at landscape and stand scales.
Species vary greatly in habitat use scale; some amphibians have restricted ranges, while large vertebrates like white-tailed deer have extensive home ranges.
Management options are presented at a broader scale (edge, streamside zones) but primarily focus on the stand level, which is the basic management unit.
Conditions favoring some species may be negative for others due to differing habitat requirements.
Pine plantations are a significant focus due to their increased extent in the South.
Edge
Edge, the juxtaposition of habitat types, is influenced by stand size and shape (small or complex stands have high edge-to-area ratios).
Historically recognized as positive for many species.
Most primary game species (e.g., white-tailed deer, wild turkey, American woodcock, ruffed grouse) thrive in forest edge and forest-field landscapes.
Forest interior birds, especially neotropical migrants, may be negatively affected by edge, potentially due to lower reproductive success or survival in edge-dominated forests.
The effects of edges created by timber harvest in predominantly forested landscapes are unclear.
Streamside Zones (SZ)
Definition: Strips of riparian and/or mature stands along streams.
Primary Purpose: Recommended in Best Management Practices to protect streams from logging impacts (sediment, nutrients, debris, temperature).
Wildlife Benefits:
Maintain wildlife diversity.
Provide unique, productive habitat (often riparian forests) in drier landscapes.
Function as travel corridors and enhance landscape connectivity.
Documented benefits for nongame birds, small mammals, herpetofauna, wild turkey, squirrels, and white-tailed deer.
Birds: Offer large trees, snags, multiple foliage layers, and foraging areas; species richness usually increases with SZ width. Forest-dwelling and interior species are more common in wider strips, but reproductive success data is lacking.
Game Species: Heavily used by deer (fall/winter, likely due to hard mast) and eastern wild turkeys. SZ at least 50 yards wide appear necessary for gray and fox squirrels.
Small Mammals: Microhabitat features (dense vegetation, fruits, seeds, down logs, logging slash) are important. Wider SZ may support mature forest communities, but some studies show similar or higher richness/diversity in narrow strips, suggesting microhabitat is more critical than width.
Herpetofauna: Offer pools, moist soils, down wood, leaf litter. Results vary; some studies show positive relation to closed-canopy conditions in wider strips, while others found greatest richness in open clearings.
Management: Retention is positive; SZ wider than 50 yards total width appear beneficial for forest interior species and several game species. Management should consider economics, adjacent land use, site-specific factors, and can involve silvicultural operations to enhance habitat (e.g., featuring mast trees, controlling pests).
Stand Structure and Composition
Key Factors: Overstory, understory, leaf litter, snags, and down wood.
Oak Mast: Important food for many species (deer, turkey, bear, squirrels), but production is highly variable annually.
Hardwood Overstories: Intercept sunlight, shading shrubs, limiting fruit production, and reducing herbaceous ground vegetation.
Harvest and Regeneration
Habitat Alteration: Can be drastic; e.g., forest canopy birds decrease, patchy/early successional birds increase after harvest.
Impact Varies: Depends on the extent of tree (especially overstory) removal, with more removal leading to more profound changes in vegetation, habitat, and wildlife.
Harvest Types:
Single-tree selection: Least impact on stands and wildlife, stand structure remains mostly intact.
Clearcutting: Alters habitat and wildlife most significantly, increasing ground forage and fruiting.
Group selection, shelterwood, seed tree cuts: Intermediate effects.
Site Preparation
Purpose: Reduce competition for pines shortly before or after regeneration.
Moderate Treatment: Can enhance vegetation diversity and wildlife habitat, especially for early-successional species (e.g., burning better for fruit production than KG-blading/chopping).
Severe Treatment: May be negative for many species; reducing hardwoods favors herbaceous vegetation and associated species, disfavoring those linked to hardwood components.
Stand Development
First 1-2 Years (Grass-Forb Dominated): Suitable for mourning doves, eastern meadowlarks, prairie warblers. Provides brood habitat for game birds (bobwhites, turkeys, grouse) and supports herbivorous/granivorous small mammals (cotton rats, Peromyscus spp.).
Young, Brushy Stands (up to ~8 years old): Diverse, lush herbaceous and woody vegetation. High forage (>2,000 lbs/acre) and soft mast production. Abundant and varied wildlife, including white-tailed deer, herbivorous small mammals, and various breeding birds (field sparrows, chats, vireos, warblers, buntings).
Pole Stage (7-10 years old): Canopies close, shading drastically reduces understory vegetation and fruit production. Habitat suitability for wildlife substantially reduced; little low vegetation, bird and small mammal populations decline, and suitability for deer and wild turkeys diminishes.
Mature Stands: High suitability, especially with openings. Support deer, gray/fox squirrels, and high densities of breeding birds (yellow-billed cuckoo, tufted titmouse, red-eyed vireo, summer tanager in hardwoods; brown-headed nuthatch, pine warbler, red-cockaded woodpecker in pines).
Old Growth: Tree fall creates openings and diversity; increased tree decay provides cavities and foraging substrate; down material provides ground structure for small mammals, amphibians, and reptiles.
Thinning
Purpose: Remove trees to concentrate growth on remaining crop trees.
Effect: Opens canopies, allows light to understory, promotes non-pine vegetation growth and fruiting, which is positive for many species.
Snags and Down Wood
Snags (Dead/Partially Dead Trees):
Uses: Nesting, roosting, foraging, perching for various species.
Cavity Nesters: Woodpeckers are primary, creating cavities used by themselves and secondary nesters (flycatchers, wood ducks, some mammals).
Population Limits: Cavity availability can limit populations; creating snags or artificial structures can help.
Creation: Natural phenomena (insects, disease, lightning) or human methods (girdling, herbicides).
Negative Aspects: May be used as perches by brown-headed cowbirds and raptors; safety hazard for workers.
Down Wood (Woody Material on Ground):
Importance: Important structural feature.
Ecological Role: Instrumental in forest nutrient cycling, supports invertebrates.
Vertebrate Use: Harbors prey for larger species (e.g., black bears); small mammal populations (Peromyscus spp., eastern woodrats) use it for protection.
Fire (Prescribed Burning)
Mortality: Little evidence of significant direct vertebrate mortality from prescribed burning; what occurs is likely insignificant at a landscape scale.
Attraction: Some animals are attracted to heat/smoke or fresh burns for prey (raptors), exposed insects/seed (wild turkeys, mourning doves), or minerals (white-tailed deer).
Arthropods/Parasites: Fire affects arthropod populations; reduces parasites of wild turkey, bobwhite, and rabbits.
General Effects: Consumes forest floor litter, sets back succession, reduces smaller hardwoods in favor of pines and herbaceous vegetation. Effects are highly variable due to site conditions, fire intensity, periodicity, seasonality, and landscape context.
Hardwood Effects: Fire wounds can lead to decay and cavities for tree squirrels; severe fire can kill trees, creating snags (which can then be consumed by fire). Fires that produce woody debris favor small mammals, while those consuming it (like site preparation burns) decrease suitability.
Red-Cockaded Woodpeckers: Used to maintain pine savannah; surface fuel around cavity trees may need to be raked to prevent resin ignition and cavity damage.
Frequent/Intense Fire: Reduces small hardwoods and shrubs, which likely reduces small mammals, rabbits, and shrub-level birds (e.g., northern cardinal, Carolina wren, hooded warbler, Kentucky warbler).
Post-Fire Flush: Accompanied by a growth flush of herbaceous vegetation (grass-forb) that persists for a few years. This favors early successional breeding birds, herbivorous/granivorous small mammals, and provides brood habitat for game birds. Also benefits gopher tortoises.
Nutrient Content: Can temporarily increase nutrient content (protein, phosphorus) of post-fire vegetation, benefiting species like deer and rabbits.
Recovery: Herbaceous vegetation is gradually replaced by hardwood sprouts and shrubs, benefiting fruit-consuming species (deer, turkey, bobwhites, omnivorous furbearers).
Herbicides
Purpose: Control exotic, noxious, or competing plants to enhance crop tree growth.
Increasing Use: Due to more selective/environmentally compatible chemicals, rising costs/less labor for alternatives, and other considerations (liability, limited burning days).
Environmental/Health: Generally minor source of water contamination; not associated with cancers or genetic abnormalities in wildlife at normal rates. Acute/chronic doses affecting wildlife are well above normal applications, and low persistence prevents chronic levels.
Wildlife Habitat Effects:
Alter plant community structure and composition, impacting wildlife habitat.
Herbicide-created snags can increase bird diversity and abundance.
Increased understory vegetation complexity post-application may increase small mammal abundance.
Amphibians likely respond to microclimate changes (humidity, temperature).
Varying Effects: Depend on herbicide type, soil texture, precipitation, application rates, and methods (target-specific vs. broadcast).
Typical Vegetation Change: Usually woody vegetation reduced, herbaceous vegetation increased.
Food Impacts: Some wildlife foods (shrub fruits) can be adversely affected, while others (grass seed) can be enhanced.
Canopy Closure: Increased pine growth due to herbicides can decrease time until canopy closure, reducing understory cover.
Specific Objectives: In mid-rotation/mature forests, herbicides can achieve structural/compositional objectives (e.g., reduce overstory, increase lower foliage cover, alter litter). Snags created by herbicides in the humid South usually deteriorate within several years.
Temporary Effects: Effects on plant communities often apparent for only a few growing seasons; treatment-related differences generally not evident after 5 years.
Fertilization
Purpose: Increase tree growth and yield in pine and hardwood forests, typically at stand establishment and mid-rotation.
Benefits: Improved pine seedling survival (up to 15%), greater growth responses with nitrogen and phosphorus combined. Rapid growth shortens rotation time by reducing time to canopy closure.
Wildlife Focus: Most investigations focus on deer forage.
Understory Effects: Generally increases biomass and nutrient content of understory vegetation, leading to higher diversity and fruit production for selected plant species.
Temporary Effects: Plant community responses are usually positive but temporary, lasting 2-3 growing seasons.
Mitigation: Gains in biomass and nutrient content may be offset by decreased time until canopy closure.
Conclusion
Southern forests have abundant and diverse wildlife communities.
Community composition and status are determined by habitat characteristics at landscape and stand levels, influenced by natural processes (succession) and human activities (affecting landscape composition and stand structure).
Both broad measures (e.g., streamside zone retention) and specific measures (e.g., species restoration) are important for conservation.
McComb Ch8
Silviculture and Habitat Management
Silviculture Defined: The art and practice of managing forest stands to achieve specific objectives for landowners or managers, including timber production, recreation, wildlife habitat, biodiversity, and aesthetics.
Silviculture as Forest Disturbance: Silvicultural activities are human-caused forest disturbances with specific sizes, severities, frequencies, and patterns that interface with natural disturbances. Managers can choose to emulate or depart from natural disturbance characteristics.
Impact on Habitat: Management decisions regarding silvicultural disturbances (size, frequency, severity, patterning) profoundly influence successional pathways, stand conditions, and plant communities, thereby supporting specific suites of species.
Even-Aged Systems
Even-Aged Stands: Characterized by trees that are approximately the same age. If single-species, trees often have similar diameter and height, forming a bell-shaped diameter distribution; mixed-species stands show more variation.
Stand Development Stages: Even-aged stands typically progress through stand initiation, stem exclusion, understory reinitiation, and shifting gap phase. Managers can truncate this sequence based on goals (e.g., pulpwood production).
Uneven-Aged Stands: Represented by three or more age groups simultaneously, with a higher number of small trees than medium or large trees. (Covered in Chapter 9).
Key Decisions in Forest Management (Figure 8.1)
Site Definition: Factors like size, shape, plant association, elevation, and natural disturbances (fire, wind, flood, insects, disease) must be considered.
Regeneration Method: Choices include clearcut, seedtree, shelterwood, deferred rotation, or none. The method influences early stand structure.
Legacy: Decisions on retaining live trees (conifer, hardwood, shrubs), snags, logs, or none.
Regeneration (Artificial/Natural): Involves choices of species, density, size, genetic modification, or relying on natural seed sources/advance regeneration.
Site Preparation: Methods include burning, herbicides, mechanical manipulation, or none. Intense preparation can reduce dead wood and affect burrowing species or plant communities.
Vegetation Management: Manual, herbicide, or browse control. Influences heterogeneity and future stand composition/structure.
Thinning: Decisions on density, spacing (uniform/variable), species, or crown class.
Even-Aged Regeneration Methods
Clearcutting: Most common method to initiate an even-aged stand, ensuring adequate growing space for regeneration. All commercial (and often noncommercial) trees are cut.
Size: Determined by ownership, economics (larger clearcuts are more efficient), laws, and habitat concerns (e.g., minimum opening sizes, edge conditions).
Seed-Tree Method: Leaves some trees after harvest to provide a seed source for natural regeneration. Effective for abundant, regularly seeding species like loblolly and shortleaf pines. Seed trees can be removed after regeneration or retained for habitat (e.g., red-cockaded woodpeckers).
Shelterwood Method: Leaves a sparse canopy cover to protect newly germinated seedlings from direct sunlight, desiccation, or frost. Used for species not too shade-intolerant, often in two to three steps: preparatory harvest, establishment/seed cut, and overwood removal.
Deferred Rotation Method (Clearcut with Reserves): Retains some trees through two complete growing cycles, providing structural complexity and benefiting species that use large, old, open-grown trees. This leads to more complex stand structure than traditional clearcuts.
Management Practices & Habitat Effects
Legacy Elements: Retaining structural components (snags, logs, living trees, shrubs) from the previous stand adds complexity, creating conditions similar to those after natural disturbances and supporting more complex animal communities. Legacy trees differ from seed trees as they are retained for structure, not just seed.
Artificial Regeneration (Plantations): Ensures desired species are regenerated.
Monocultures: Economically efficient for timber but may lack habitat elements for some species.
Mixed-Species Plantations: Becoming more common, offer less risk from insects/diseases, and provide greater plant/vertical profile diversity.
Planting Density: Wide spacing can prolong the grass-forb-shrub phase and lead to deeper crowns. Variable density planting creates horizontal and vertical complexity.
Vegetation Management:
Chemical vs. Manual: Spot control creates heterogeneity; manual control can proliferate sprouts.
Herbicides: Can temporarily decrease shrub availability. Effects vary by species; some decline, others increase. They are important for controlling invasive species.
Prescribed Burning: Used for site preparation, reducing competing vegetation, and fuel reduction. Can harm forest floor amphibians/mammals but enhance forage quality for herbivores.
Herbicides and Pesticides:
Direct Effects: Chemical exposure can be lethal or sublethal (altering behavior, hormones, nervous system). Larval amphibians are vulnerable.
Indirect Effects: Primarily by changing habitat, affecting food and cover availability. Changes in plant composition often have a greater effect than direct spraying.
Ethical Concerns: Society often finds direct harm from chemicals less acceptable than habitat changes or natural succession leading to local extinction, partly due to perceived risks to human health.
Integrated Pest Management: Growing acceptance to reduce reliance on chemicals due to health risks and economic costs (e.g., public health, pest resistance, crop losses, bird losses, groundwater contamination).
Precommercial Thinning: Cutting or killing trees early in stand development (before commercial value) to promote growth of residual trees, increase spacing, and prolong the grass-forb-shrub stage, benefiting early successional species. Effects vary by species (e.g., increases habitat for Sitka black-tailed deer, decreases for snowshoe hare).
Commercial Thinning: Harvesting trees that can be sold to manipulate stand density, provide income, and concentrate growth on fewer, larger trees. Reduces basal area, which recovers as residual trees grow.
Stocking Charts/Density Management Diagrams: Tools for silviculturists and biologists to design stands, estimate stocking levels, and understand competition-induced mortality.
Benefits: Can create openings, enhance understory vegetation, benefit species like Hammond's flycatchers, and improve habitat for various mammals and birds. Can also accelerate development of late forest structure or restore fire-excluded functions.
Adverse Effects: Some species, like northern flying squirrels, may be negatively affected for years.
Site Index: An indicator of a site's potential to grow trees in height, which is less dependent on stand density than diameter growth. Higher site index means faster diameter growth and basal area increase.
Fertilization: Increases diameter growth of dominant trees and nutrient content in browse/forage. Benefits forage for herbivores (moose, hares, deer, elk) and can increase bird species/individuals.
Rotation Length:
Economic Rotation Age: The point at which mean annual increment (MAI) of volume peaks, maximizing profit. Varies with site quality, product values, and interest rates.
Ecological Rotation Age: Average interval between stand replacement disturbances. Often much longer than economic rotation.
Trade-offs: Maximizing profit (shorter economic rotation) can reduce habitat for species needing older stands. However, complexity elements (variable density, legacy, mixed species) can be incorporated into younger stands.
Case Study: Douglas-Fir Plantation (Western Cascades, WA)
Traditional Management: Clearcut, site preparation, vegetation management, plant 750 seedlings/ha (single species). At age 30, commercial thin, grow to age 50. Results in uniform stands with low structural complexity.
Enhanced Complexity Management: Clearcut, retain 25 legacy trees/ha (multiple species), careful site preparation (retaining advance regeneration), plant 750 seedlings/ha (mixed species). At age 30, commercial thin, underplant with new species for a second age class, grow to age 50. Results in greater tree/species diversity, broad range of diameters, and more structural complexity. Economic profit is less than traditional but still positive, allowing for habitat complexity development.
Guidelines for Increasing Complexity in Even-Aged Stands (Hartley 2002)
Retain dead and living trees (snags, reserve trees) in the stand or in retention islands/strips.
Favor polycultures over monocultures (plant multiple species or leave native trees).
Favor native species over exotics.
Site preparation methods should reflect natural disturbances and conserve dead wood.
Thin early and frequently to maintain horizontal complexity.
Extend rotations as long as possible.
Grow some crop trees through two rotations.