11/30/2010 1 Geography 1001: Climate & Vegetation Instructor: Dr. Holly Barnard Nov. 30th - Logistics 1. Scientific Method Papers DUE TODAY in class – no exceptions. 2. Exam results 3. Remaining lecture schedule. 4. Final Exam: Monday, December 13th, 4:30-7:00 pm 0510152025303535 40 45 50 55 60 65 70 75 80 85 90 95 100Frequency Grade in percent Midterm 3 grade distribution 051015202530354035 40 45 50 55 60 65 70 75 80 85 90 95 100Frequency Grade in Percentage Average Midterm Exam Grades for Semester11/30/2010 2 Definition (Pickett and White 1985) • “A relatively discrete event in time that disrupts ecosystem, community or population structure and changes resources, substrate availability, or the physical environment.” Ecological Importance of Disturbance • “Resets clock” • Mixes ages, composition, structure at multiple spatio-temporal scales • Provides diverse habitat and PATHCES – important to biodiversity • Ecosystems are dynamic – growth, death, replacement. Disturbance is a major change factor Types of Disturbance • Many different types, operating at many spatio-temporal scales • Different types produce divers results (over space and time) • Interactions can occur across scales • Type of disturbance present in an ecosystem often a function of components, structure of ecosystem as well as physical (climate, topography, etc.) factors. Studying Disturbance • Disturbance History, Behavior, Ecology • The reconstruction problem • The retrospective problem (natural experiments) • The replication problem11/30/2010 3 Vegetation Dynamics Concepts • Frequent disturbances promote spatial heterogeneity at different scales – Habitat and niches – Reset succession • Patch dynamics as constant change norm • Equilibrium toward a stable climax exception The role of disturbances across scales • Spatial heterogeneity: At a stand scale The role of disturbances across scales • Spatial heterogeneity: At a landscape scale Photo: D. Kulakowski Patch dynamics11/30/2010 4 Equilibrium, Stability & Diversity • Landscape heterogeneity most strongly influences those processes or organisms that depend on multiple patch types and are controlled by a flow of organisms, water, air, or disturbance among patches. Fire Ecology11/30/2010 5 Fire Ecology • Influences on fires • Types of fires • Plant adaptations to fires Fire • Major disturbance process in many forests • Important in grasslands also • Used by humans for millennia • Being introduced into tropical forest. Some Controls of Fire • Fuel Moisture content • Fuel Continuity • Ignition and heat spread • Fire triangle • Fire behavior triangle Influences on fires - Fuels Photo: D. Kulakowski11/30/2010 6 Influences on fires - Weather Influences on fires - Topography Fast Slow Types of fires (or fire regimes) • Severity – Surface fires, crown fires, mixed-severity • Frequency – Frequent and infrequent Fire Intensity • Fuel a major factor in intensity (size, shape, arrangement, moisture, continuity) • Patchiness of fuel adds to patchiness of fire (intensity) • Surface, understory, crown fires Crown fires release enormous amounts of E and can move very quickly11/30/2010 7 Fire Severity • Difficult to measure • Frequently Ordinal (L, M, H) • When quantified often a percent of crown burned/dead • Reconstruction very difficult, not standardized in fire history studies Severity MFRI: Fires in study area in 1555, 1849, 1871, 1882, 1891, and 1944 Intervals are 1849-1555=294; 1871-1849=22; 1882-1871=11; 1891-1882=9; 1944-1891=53 294+22+11+9+54=390 390/5=78 MFRI=78 years Multiple Sites or individual site? Record Erasure? Variation? NFR: Study Area total is 3500 km2 Study Time Frame from 1555 to 1998. 1555 Fire 949km2;1848 Fire 1876 km2; 1871 Fire 647km2; 1882 Fire 441 km2; 1891 Fire 498 km2; 1944 Fire 121 km2 . 949+1876+647+441+498+121=4532 km2 burned in (1998-1555=) 443 years 4532/3500=129% of study area burned in 443 years NFR= 443/1.29 = 343.4 Plant adaptations to fires • Avoid fire damage • Recover following fire damage • Colonize after fire11/30/2010 8 Avoid fire damage Recover following fire damage Photo: D. Kulakowski Colonize after fire Photo: D. Kulakowski Photo: D. Kulakowski11/30/2010 9 Photo: H. D. Grissino-Mayer -Biscuit Fire 2002 -500,000 acres (2000 km2) -Reflective of Present Fire Management Issues: Wilderness Fight or Leave Exurban Forest -Controversy Donato 2002 Science Paper: Salvage Logging reduces seedling regen and increases future fire risk OSU Dean, USFS and Timber Industry letter Issues of Academic Freedom http://upload.wikimedia.org/wikipedia/en/e/eb/NASA_Biscuit_fire.jpg Flood • High intensity flow of water in river/stream systems • Affects bed structure and composition, sediment deposition, inputs to streams. • Flood Hydrograph reflects intensity • Peak curve affected by humans, especially forest roads11/30/2010 10 A. Discharge Amount B. Time Lag C. Peak Discharge D. Zone of Flood Risk E. Normal Discharge F. Recession Limb G. Rising Limb Storm Rainfall event Hours from start of storm Landslide/Mass Wasting • Important input to streams • Synergy with rainfall, soil moisture content • Slope angle important (angle of repose) • Intensity a measure of volume of scar (inputs) • Course Woody Debris (CWD) also delivered • Roads affecting rate, amount of inputs11/30/2010 11 Snow Avalanche • Mass of snow flowing downslope • Enormous energies due to speed, mass • Controlled by many factors related to snowpack, especially stable slabs on unstable layers (not-bonded) • Triggered when stress applied to snowpack • Can focus in gulleys or cover large areas • Related patterns of vegetation Lahars/Debris Flows • Hot or cold mixture of water, rock, mud that flows down a slope of a mountain, generally due to volcano activity • Triggers: landslides (rain, earthquake, eruptions), glacial melting/serac failure, eruption. • Almost always on volcanoes11/30/2010 12 Windthrow • Trees uprooted during excessive wind events • Soil moisture content, topography, soil depth important considerations • Synergistic with fire, disease (supplies dead material, weakened trees susceptible to other disturbance) • Generally smaller areas than fires, other events • Provides small gaps for succession • Root-mound topography • Can be Isotropic (trees fall in one direction)