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Population and community-level consequences of fragmentation. interrupts ecological patterns and processes reduced habitat patch area edge effect increased patch isolation decreased successful movement (immigration and emigration) increased likelihood of local extinction. - PowerPoint PPT Presentation
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Population and community-level consequences of fragmentation
• interrupts ecological patterns and processes• reduced habitat patch area• edge effect• increased patch isolation
– decreased successful movement (immigration and emigration)– increased likelihood of local extinction
Processes operating between fragments
• dispersal– increasing fragmentation decreasing colonization rates– leads to decreasing # of species within patch– increasing risk of local extinction of species within patch
Processes operating between fragments
• dispersal• matrix
– disturbed/converted habitat surrounding fragments– potential roles?
matrix
Persistence of populations• In which directions would you predict net movement of
individuals? • Which populations are more likely to persist? why? Disappear?• What are the factors most important in determining a
population’s likelihood to persist?• Which populations, if they disappear, are most likely to be
recolonized?
Grizzly bear
• 50,000 historic estimate• Persecution and habitat
changes == about 1,200 wild grizzlies remain in lower 48
Grizzly bear ecosystems
http://www.fws.gov/mountain-prairie/species/mammals/grizzly/
<20
0? >500
40-50 30-40 ?
Y2YYukon to Yellowstone Conservation Initiative
• Goal: maintain and sustain region to allow wilderness, wildlife, native plants, and natural processes to function as an interconnected web of life
• Partnerships of NGOs, businesses, foundations, concerned citizens, scientists
• Based on science• Balance area needs
Cascade Land Conservancy
In conjunction with members of communities, work toward large-scale conservation
• Habitat Lands• Farmland• Working Forests• Parks, Trails and Open Spaces• Shorelines and Estuaries
Natural Landscapes are also heterogeneous
Why?
Natural Landscapes are also heterogeneous
Why?
Topography and climate
How Rain Shadows Formwet W sides, dry E sides
OlympicsPuget Trough
CascadesEllensburg
North BendPpt 100-200” Ppt 10-12”
Ppt 36”
Seattle
Ppt 100”
Ppt 10-12”
Rainshadows
PacificOcean
Air mass
Generalized Forest Zones of the Washington Cascades
Cross-section of Cascades
Western hemlock
Pacific silver fir
Mountain hemlock
Alpine
Alpine
Spruce-fir
Douglas-fir
Ponderosa pine
Shrub-steppe
WEST EAST
Structural diagram for successional seresin Douglas-fir forests(Franklin and Spies 1991)
Natural succession
Structural diagram for successional seresin Douglas-fir forests(Franklin and Spies 1991)
Succession from different sources of disturbance: fire, cutting
Natural succession
• Disturbance: an event that causes a change to resource availability, substrate, or the physical environment
– Fire, wind storm, insect outbreak, floods• Disturbance regime: spatial and temporal dynamics of
disturbances over a longer time period– Defined by frequency, intensity, severity, size
Natural Disturbances
Regional & landscape
scale patterns of forest
disturbance
Turner et al. 2001
from Turner, et al (2001)
from Turner, et al (2001)
Patch Dynamics: over space and time, disturbances create a mosaic of patches of various sizes, shapes, and successional stages across an area
Role of Fire
Habitat diversity:• landscape mosaics• uneven-aged stands
(in most cases)• dead and dying trees
Nutrient release
Leads to a greater diversity of wildlife
Landscape mosaic created by the 1988 Yellowstone fires
• Remain after disturbance• Influence ecological effects of disturbance and patterns of
succession• Snags, logs, roots, seeds
Ecological Legacies
Scrub Oak: Survive fires only by resprouting
Wildlife Responses to Fire
Serotinous Cones
• Sealed by resin• Opened by fire• A new generation grows
(ex Jack Pine)
Winners and Losers
• Disturbances change habitat naturally• Some wildlife increase = “winners”• Some wildlife decrease = “losers”• Some generalists show little change• Disturbance is not “good” or “bad” for all wildlife
How Did Fire Affect PNW Forests?
Historical Fire Regimes• High Severity
– Infrequent (100+ yrs) and stand-replacing• Mixed Severity
– Less frequent (25-75 yrs) and a mix of severities• Low Severity
– Frequent (5-15 yrs) but low intensity
• Stimulates new growth• Higher protein• Higher digestibility
• Attracts moose, elk, deer, and their predators (wolves) plus bears
Fire improves browse quality
Pyrophilic Insects
Barbeque Beetle• Infrared sensors on abdomen to detect fire from a distance• With predators and sticky tree resin gone after fire, good conditions for mating
Xenomelanophila miranda beetle• Mate on charred trees soon after fire
Black-backed Woodpecker
• Nearly restricted in its habitat distribution to standing dead forests created by stand-replacement fires
• Feed on larvae of the black fire beetle
Longleaf Pine of the Southeast
• Fire-dependent ecosystems• Historically, surface fires every 3-5 years
– Ignited by lightning and Native Americans• Now maintained by prescribed burning
Red-cockaded Woodpecker
• Endangered (SE)• Requires large, live
longleaf pine trees• Longleaf is a fire-adapted
species
Lives in large LIVE longleaf pine
• Drills holes around the cavity
• Resin flows – defense against snakes
• Longleaf pine type one of most endangered forest types in world – 99% gone
Prescribed burning used to maintain Longleaf Pine savanna
There is no ecological equivalent to fire
Kirtland’s Warbler
• Endangered species • In danger of extinction until an
out-of-control fire triggered a population revival
• Nests in young Jack Pine, a fire-dependent species with serotinous cones
Wildlife Management
• Stand-replacement fires may be necessary for long-term maintenance of many pyrophilic wildlife populations
• Such fires are controversial due to human safety
Wildlife Management• Salvage cutting may reduce the suitability of burned-
forest habitat by removing the most important element-standing: fire-killed trees needed for foraging and nesting (ecological legacies)
• Prescribed burning becoming more accepted as a tool to reduce fuel loads
Persistenceof
Change
Similarity of Alteration to Natural HabitatHigh Low
Low
High
Agriculture
TimberHarvest
Urbanization
High
Low
Effect ofFragmentation
Landscape Alterations Can Profoundly Affect Natural Ecological Systems