Slope aspect effects microclimate in desert environments

Slope aspect effects microclimate in desert environments (Monger and Bestelmeyer 2006)

• Slope aspect effects microclimate in desert environments (Monger and Bestelmeyer 2006)

• Vegetation composition changes as hill slope position changes (Bridge and Johnson 2000)

Do soil characteristics change as hill slope position changes?

• Do soil characteristics change as hill slope position changes?

• Does soil creep behave as predicted in a semi-arid climate? And what effect does vegetation community have on soil creep?

• How does vegetation community and soil formation interact at different hill slope positions?

34 22’ 6.78"N 106 32’ 11.83"W

• 34 22’ 6.78"N 106 32’ 11.83"W

• Slope sequences followed transects previously setup by Esteban Muldavin

• Bedrock

• schist
• gneiss
• vein Quartz
• quartzite

Hill Slope

• Hill Slope

• Soil Characteristics

• Vegetation Community

Slope Sequences

• Slope Sequences

• 5 different north and south facing slopes
• 4 soil pits dug on each slope
• Total of 40 pits
• Aspect of each slope was measured

Line Transects

• Line Transects

• 40 transects completed
• 11 m transects
• Parallel to slope position
• Basal area and Canopy measured

Graphed as a function of hill slope position:

• Graphed as a function of hill slope position:

• Soil depth
• Soil Texture
• Soil Color

• Compared soil depth and slope aspect to:

• % Grass Basal area
• % Canopy- Tree
• % Canopy- Shrub
• % Canopy- Grass

Two different soil types

• Two different soil types

• Both North- and South-facing slopes
• Slope Sequences 2 and 4
• Slope Sequences 3 and 6 (and possibly 1)

• Fine soil material from wind (eolian) source

• Leads to higher water holding capacity
• Enables establishment by vegetation

Primarily A horizons

• Primarily A horizons

• Soil very thin

• Textures

• Sandy Loam
• Loamy Sandy

• Soil likely wind blown deposits

Both North- and South-facing slopes

• Both North- and South-facing slopes

• Soil very deep (>25 cm)

• Well developed soil column
• Thin A horizon
• Thick B horizon
• Strong CaCO3 film and filament development

• Soil likely much older than soil on Slope sequences 2 and 4

“Soil horizon development as determined by landform age…” (McAuliffe 1994).

• “Soil horizon development as determined by landform age…” (McAuliffe 1994).

• Different soil horizons and types

• Landform same age over Los Piños
• How are there such distinctly different soil types?
• Change in climate
• Change in depositional regime
• Effect of grazing

The vegetation community may have an effect on the soil of both north and south facing slopes.

• The vegetation community may have an effect on the soil of both north and south facing slopes.

• % Grass Basal Area vs. Soil Depth

• May lead to deeper soils on South-facing slopes
• No correlation on North-facing slopes

• % Canopy of trees vs. Soil Depth

• May lead to deeper soils on North-facing slopes
• May lead to shallower soil on South-facing slopes

• % Grass Basal Area vs. Aspect

• Grass prefer to live on shallower slopes

Soil characteristics changed with respect to hill slope position

• Soil characteristics changed with respect to hill slope position

• Soil depth and aspect are likely linked to vegetation community

• Vegetation may have an effect on soil transport

• North and South facing slopes appear to behave differently, likely due to the differences in vegetation community, slope aspect, and microclimate.

Les McFadden, Esteban Muldavin

• Les McFadden, Esteban Muldavin

• Jennifer Johnson

• Amaris Swann

• Summer REUs: Shayla Burnett, Harmony Lu, Rick Duran, Mitch Nakai, Cynthia Malone, Natasha Ribiero, Melissa Shaginoff, Antonio Nevarez, Amanda Labrado, Elida Iniguez

• Summer Interns: Brenda Nieto

• National Science Foundation

McAuliffe RJ. (1994). Landscape Evolution, Soil Formation, and Ecological Patterns and Processes in Sonoran Desert Bajadas. Ecological Monographs, Vol. 64, No. 2: 111-148.

• McAuliffe RJ. (1994). Landscape Evolution, Soil Formation, and Ecological Patterns and Processes in Sonoran Desert Bajadas. Ecological Monographs, Vol. 64, No. 2: 111-148.

• Monger HC and Bestelmeyer BT. (2006). The soil-geomorphic template and biotic change in arid and semi-arid ecosystems. Journal of Arid Environments. 65: 207-218.

• Daniels RB and Hammer RD. Soil Geomorphology. Wiley (1992): New York.

• Bridge SRJ and Johnson EA. (2000). Principles of Terrain Organization and Vegetation Gradients. Journal of Vegetation Science, Vol. 11, No. 1: pp. 57-70

• Francis CF. Plants on Desert Hillslopes. Edited by: Athol D. Abrahams and Anthony J. Parsons. Geomorphology of Desert Environments. Chapman and Hall (1994): London.