Swanson 1988 - Landform effects on ecosystem patterns and processes Flashcards
What is the greatest influence of geomorphic processes operating before, or subtly coexisting w/ vegetation?
- Geo processes may have greatest influence on vegetation through controlling patterns of soil properties
Geomorphic processes over the long vs. short-term
- Long: create landforms
- Short: landforms are boundary conditions controlling the spatial arrangement and rates of geo processes
Example of a fine-spatial scale interaction of geo processes
Plants may restart soil erosion or may be damaged by earth movement
Example of broad-scale interaction of geo processes
- Distribution and height of landmasses control distributions of plans and animals through influences on environmental gradients of temp and moisture and on migration corridors during envr change
What does landscape commonly refer to?
- Form of the land surface and associated ecosystems at scales of hectares to many km
- Composed of landforms and ecological units such as patches
What does landform commonly refer to?
- ex. like a landform carved out by a landslide or created by sediment deposition forming a gravel bar
- Component of landscape
Geomorphic process refers to?
- Mechanical transport of organic and inorganic material
- or Transfer of material/disturbance of biota w/o regard to development of landforms or timescale in which that occurs
Effect of landforms on ecosystems: 4 classes
- Landforms and envr gradients
- Landforms and movement of material, organisms, propagules, and energy
- Landforms and nongeomorphically induced disturbances
- Interaction among landform, geomorphic processes and ecosystem
Class 1
- Landforms and envr gradients (elev, aspect, parent material, slope steepness) influence temp, moisture, nutrients available at sites w/in landscape
- Both simple and complex landform effects cannot easily be separated from effects of landforms on movement of materials and energy
Class 2
- Landforms affect/regulate flow of organisms, propagules, energy, and material through a landscape by defining gradients, influencing paths (wind), and forming barriers/corridors for movement
Class 3
- Landforms may influence frequency and spatial pattern of nongeomorphically induced disturbances by agents such as fire, wind, and grazing
Class 4
- Landforms constrain the spatial pattern/rate or frequency of geomorphic processes that alter biotic features/processes
How does Class 4 differ compared to Classes 1-3
- Classes 1-3 considered static
- Class 4 regards landforms and ecosystems as dynamic
Where is precipitation larger?
- Higher elevations from orographic effects
How do landforms influence the temporal/spatial patterns of fluxes of material carried across landscapes by surface water?
- Water quality can vary w/ lake position in landscape
- Lakes lower in landscape reflect proportionate increase of surface or groundwater contributed to lower lakes
- Lower lakes have higher conc’n of solutes due to water passing through more veg and soil
- Lakes high in system get more water by precip and more spring melt
How does water flow?
- Along gravitational gradients
What controls the dominant wind paths or animal migration paths?
- Controlled by landforms at broader scales
How do landforms affect some vertebrates?
- Delimit ranges
- Gullies, cliffs, streams may form physical barriers
- Or as convenient, but passable features that can mark home ranges of neighbouring animals
What are some examples of landforms affecting vertebrates in semi-arid landscapes?
- Size/abundance of cavities in outcrops and boulder piles control distribution of rodents
- Raptors use air space above cliffs to ride convective wind induced by heating of cliff and talus surfaces
- Birds prey on the rodents using the fine-scale landforms below
What is the relationship of grazing on the landscape?
- Forage may be better in lowlands due to influence of landforms on spatial patterns of soil moisture and nutrients
- Animals preferentially grazing may then redistribute nutrients on landscape
What is a known example of landforms controlling patterns of ecosystem disturbance across landscapes (nongeomorphically induced disturbances)
- Inundation of channels and floodplains by floodwaters
How do landforms increase frequency of disturbance?
- Channeling of things like fire and wind into areas
What can control patterns of snow distribution
- Topography, subtle ridges/depressions
- Can be redistributed by wind
What is the result of persistent snow accumulation? Class 3
- Suppression of vegetation
- Creation of bare soil
- Loose sediment associated with water source (snow bank)
- redistribution of water in form of snow (class 2 effect) leads to disturbances of veg by shortened growing season/establishment
- Disturbance of site/adjacent areas by erosion and sed transport (Class 4 effect) may follow
What is the distinction btwn landform effects of classes 3 and 4?
- In both classes, landforms constrain movement of agents that disturb ecosystem (fire, water, wind, animals)
- Class 3 disturbances operate through veg, which leads to secondary disturbance by accelerating geo processes
- Class 4 geo processes are the primary disturbances
- Emphasis on physical dynamics of the landscape in class 4
Which class focuses on the physical dynamics of the landscape?
- Class 4
- Geo processes are the primary disturbances
What are 2 examples of geomorphic disturbances in Class 4? What is the role of the landforms in this?
- Landslides
- Later shifts of river channels
- Landforms constrain the frequency and magnitude of change
What limits the lateral channel change in mountain streams? Class 4
- Steep channels, coarse beds and bank seds, and bedrock outcrops
- Floodplains experience more persistent migration and reconstruction of floodplains in valley floors than mnt streams
What dictates the vegetation in valley bottom vs. mountain channel streams? Class 4
- Valley bottom more adjusted to deposition of fine seds
- Mnt streams lack of fine sed restricts floodplain vegetation to species adapted to frequent minor deposition of fine seds
- Controls distribution of substrates available to plants and animals
How do landslides work?
- Hollows/ depressions in bedrock collect seds from surrounding hillslopes
- Landslide eventually moves this stored material
- Landslide potential increases w/ moisture, soil depth exceeding root depth (less anchoring), decomposition of veg after fire, logging or other disturbance causing mortality
Frequency/magnitude relationships of events
- Catastrophic more imp for some landforms more than others (landslides in bedrock hollows)
- Floodplains experience progressive resetting by frequent small events
- Some landforms and geoprocesses co-evolve and maintain a steady-state dynamic equilibrium along topo sequence
Describe the 4 Classes as they relate to a mountain like mount Rainier
- Class 1: Pattern of vegetation zones up elevation
- Class 2: Higher productivity of lakes in valley bottom due to downslope movement of moisture and nutrients
- Class 3: Ridges and valley bottoms are barriers to fire, avalanches move down bedrock defined paths that cut through veg
- Class 4: Valleys experience severe disturbance by mud-flows triggered high on the mountain
Landscape Ecology as defined by Risser
- The development and dynamics of spatial heterogeneity
- spatial and temporal interactions and exchanges across heterogeneous landscapes
- influences of spatial heterogeneity on biotic and abiotic processes
- and management of spatial heterogeneity
Knowledge of geomorphic underpinnings of ecosystems is essential to…?
- interpreting ecosystems in context of their landscapes
What class(es) influence occurs through the effects of landforms on envr gradients?
Class 1 and 2
What class(es) influence occurs through regulation by landform of the patterns and frequency of disturbance?
Class 3 and 4
