Landscape Ecology - Lecture Notes

Landscape Pattern and Ecosystem Processes

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[From Bailey 1996]

A. Major vectors
 
(1) Wind
- Carries heat energy, water, dust, pollutants, nutrients, propagules, organisms, etc.


(2) Water

- Carries mineral nutrients, seeds, insects, sewage, fertilizers, pollutants, etc.


(3) Flying animals (e.g., birds, bats, bees)

- Carry fruits, seeds, spores and insects in feathers, feet, and the gut


(4) Ground animals (e.g., mammals, reptiles)

- Carry seeds, fruits, spores, insects, etc.


(5) People (use of vehicles)

- Carry organisms, seeds, fruits, spores, insects, nutrients, etc.






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B. Main forms (or forces) of movement

(1) Diffusion

- Random movement of objects or materials

- Gradient-diffusion theory:

            Q = - K Grad C

            where K-diffusivity, Grad C - gradient in concentration (C).
 

(2) Mass flow
Water:
- Steams, rivers
- Surface runoff
- Subsurface flow
Wind:
- Caused by differences in atmospheric pressure due to differential heating of the earth's surface by solar energy
- Wind erosion, sand-dune movement, blowing materials across landscapes


(3) Locomotion:

- Movement of materials, energy and organism by animals and people
- Tend to highly aggregated

   

• The spatial distribution of biomass, ecosystem productivity, and biogeochemical processes are closely related to the spatial pattern of the landscape (e.g., vegetation types, hydrological regime, topographic variation, disturbance regime, climatic variation, etc.)

• Main causes:
• Climatic factors (temperature, precipitation)
• Soil heterogeneity
• Topographic variations
• Animal activities (e.g., selective foraging)


      

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• Example: Ecosystem properties and processes vary spatially across the landscape.


 

• Both the composition and configuration of landscapes (e.g., land cover types, diversity, connectivity, and boundary characteristics) affect flows of materials, energy, and organisms in landscape mosaics.
• Flows of different types affected by and affect landscape pattern

• Ecosystem processes: primary productivity, biogeochemical cycling, decomposition


  
 
Figure caption:  Movement of nutrients and major pathways between ecosystems on the Rhode River watershed, Maryland (Drawn based on data from Peterjohn and Correll 1984; cf. Turner et al. 2001)
 
 
• Margalef's (1963) hypothesis: In considering flows between adjacent ecosystems or elements, the younger may operate as a source of energy or material, and the more mature as a sink or recipient (also see Risser 1990).

• Example: Lateral flows in landscapes and effects on ecosystem processes
  
• Shen et al. 2011. Blowing litter across a landscape: effects on ecosystem nutrient flux and implications for landscape management. Landscape Ecology.

• Stury area and field sampling

 

 
• The universal soil loss equation (USLE):

A = f(R, K, L, S. C)    or:   A = f(R, K, L, S. C, P)

A - amount of soil eroded
R - rainfall intensity
K - soil erodability factor
L - length of the slope
S - angle of the slope
C - vegetation cover
P - supporting practices factor


The Universal Soil Loss Equation (USLE) does not account for landscape heterogeneity, a measure of spatial configuration or juxtaposition of landscape units needs to be incorporated (Risser 1990).  Efforts have been made to incorporate landscape heterogeneity into the universal soil loss equation, resulting in revised universal soil loss equations (RUSLE).



• Example: Land use and land cover change alters the spatiotemporal pattern of ecosystems (e.g., urbanization)

  

• Landscape phenology