Remote Sensing

Landscape Ecology - Lecture Notes

Remote Sensing
&
Its Application in Landscape Ecology

I. What is Remote Sensing?

The acquisition of information by unattached means, such as aerial photography, satellite imagery, thermal imagery, and radar.

* How many satellites are there in space? [Local Link]

*Video: What is remote sensing?

Satellite sensors take a series of pictures which record reflectance intensity at different wavelengths of light.

Different land cover types have characteristic reflectance values or spectral signatures, so that they can be used to classify each pixel according to land cover type. The spectral information may be turned into false-color images that look like regular photographs.

Radar can image the earth's surface day and night and through clouds. Thus, radar remote sensing assures acquisition of land cover information for the moist tropics and northern latitudes where cloud cover seriously limits the coverage of other types of sensors.

For using remotely sensed digital data, digital image processing is usually necessary, which includes the following categories:

Image rectification and restoration (e.g., removing noise due to the sensor, replacing missing data, geometric correction of data)

Image enhancement (to increase the visual distinction between features in a scene, e.g. contrast or edge enhancement)

Image classification and modeling (using a series of mathematical and statistical algorithms to categorize pixels into land cover classes)

Boreal Ecosystem - Atmosphere Study (BOREAS)

2. Major Existing Satellites and Sensors:

- US Landsat Thematic Mapper (TM) --- Landsat was the 1st earth-observing civilian satellite launched in 1972.

- Advanced Very High Resolution Radiometer (AVHRR) -- NOAA

- Geostationary Operational Environmental Satellite (GOES) -- NOAA

- French Systeme Probatoire d'Observation de la Terre (SPOT)

- United States Defense Meteorological Satellite Program (DMSP)

- European Meteorology Satellite (METEOSAT)

[From: Groom, G., C. A. Mucher, M. Ihse, and T. Wrbka. 2006. Remote sensing in landscape ecology: experiences and perspectives in a European context. Landscape Ecology 21:391-408.]

Landsat Program Timeline

3. What Can Remote Sensors Measure?

Take Landsat Thematic Mapper (TM, with 7 bands) as an example (from Quattrochi and Pelletier 1991 p.59 in Turner and Gardner (eds) 1991):

Band	Ecological Use
1 (0.45-0.52 µm) [visible-blue region]	discrimination among water, soil & vegetation discrimination of deciduous from coniferous veg cultural feature identification
2 (0.52-0.60 µm) [visible-green region]	measuring green reflectance peak of vegetation cultural feature identification
3 (0.60-0.69 µm) [visible-red region]	chlorophyll absorption detection vegetation discrimination cultural feature identification
4 (0.76-0.90 µm) [reflective near-infrared]	vegetation types, vigor, biomass content water bodies & soil moisture
5 (1.55-1.75 µm) [reflective mid-infrared]	soil & vegetation moisture content differentiating snow from clouds
6 (10.4-12.5 µm) [thermal infrared]	vegetation stress analysis, soil moisture thermal mapping applications
7 (2.08-2.35 µm) [reflective mid-infrared]	discriminating mineral and rock types vegetation moisture content

Some biophysical measurements for use in ecosystem studies obtained from satellite remote sensing (Ustin et al. 1991):

Fractional cover of soil and vegetation

Crown spacing and variance

Crown height

Green biomass

Dead biomass

Vegetation indices

Phenologic state/seasonal growth

Total chlorophyll concentration

Canopy cellulose concentration

Canopy lignin concentration

Foliar water content

Canopy water potential

Soil moisture

Vegetative APAR (Absorbed Photosynthetically Active Radiation)

Non-vegetative APAR

Surface bidirectional reflectance distribution function

Evapotraspiration

4. Applications of Remote Sensing Techniques in Landscape Ecology

Major Advantages of Remote Sensing for Ecological Studies

Absence of observer interference because of the large distance between the sensor and the object;

Feasibility of repeated measurements at large (regional or even global) scales;

Availability of the wide variety of spectral ranges and sensors to provide remotely sensed data.

Major Types of Applications

Classification and mapping of landscapes (e.g., maps of vegetation, soils, habitat, and land use and land cover)
Measuring structural and functional properties of ecosystems and their spatial pattern in a landscape on different scales (e.g., leaf area index, plant density, canopy closure, dominant species, chlorophyll concentration, biomass, ecosystem productivity or crop yield, habitat condition)
Monitoring landscape change (e.g., disturbance regime, forest decline, urbanization, land use change, vegetation succession, and ecological responses of landscapes to human activities and global change).

Remote sensing for biodiversity and ecosystem dynamics (Turner et al. 2003)

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