Effects of Convex and Concave slopes on Vegetation

Effects of Convex and Concave slopes on Vegetation Characteristics Joe Persico

Introduction/Background Question: How could convex and concave slopes (both north and south) affect vegetation and soil characteristics in the high alpine? This may change the way that water flows from snowmelt and drainage and can help us understand the dynamics of this ecosystem (Aandahl, 1949) Looking at north and south facing slopes as well to affects the landscape on a larger scale J. E Pinder III worked in Lassen Volcanic National Park

Site Description #1 Just above cable gate near our alpine field day site. South west of Niwot Mountain South facing slope with both a concave and convex section Just above treeline Mostly small herbaceous vegetation with some willows and Krummholz Slope aspect: 150° S-SE Slope Angle: 9° Coordinates: 40° 03'04. 0"N 105° 35'04. 7"W

Site Description #2 Above Cable Gate and over Niwot Ridge Northwest facing slope Northwest of Niwot Mountain and just below Just above treeline with small Krummholz creeping in Concave and convex sections of the slope Mostly small herbaceous vegetation with some Krummholz and willows Slope Aspect: 320° N-NW Slope Angle: 6 -8° Coordinates: 40° 03'13. 9"N 105° 34'38. 0"W

Methods Walked past cable gate a south facing and north facing slope with concave and convex sections Each convex or concave section set a 30 m transect perpendicular to the aspect of the slope Record the angle and distance to center for concave and convex slopes Each transect had 3 Daubenmire plots Small sample of soil at each site at depth 10 cm was taken Line intercept method was also used along each transect within each plot Steps repeated along transects on our North facing slope Data recorded analyzed Anova-with replication and chi-squared

Results/Figures Frequency of Non-Herbaceous Cover 12 Site Frequency (12 sites) 10 Chi Squared Test: p=. 003 ** 8 6 4 2 0 Moss Lichen Rock Cover Type Site Freq (convex) Site Freq (concave) Bare/Litter

Results/Figures Frequency of Graminoids Chi squared test: p=. 178 12 Site Frequency (/12) 10 8 6 4 2 0 Alpine Sedge Alpine Rush Cover Type Site Freq (convex) Site Freq (concave)

Results/Figures Percent Cover of Moss & Lichen 50 Anova Test: Cover p-value: 0. 0496 * Concavity p-value: 0. 0003*** Interaction p-value: 0. 25 45 Avg Percent Cover 40 35 30 25 20 15 10 5 0 Moss Lichen Cover Type Avg % Cover Convex Avg % Cover Concave

Results/Figures Average % Cover of Sedges and Rushes 25 Anova Test: Cover p-value: 0. 117 Concavity p-value: 0. 0018** Interaction p-value: 0. 189 Avg Percent Cover 20 15 10 5 0 Alpine Sedge Alpine Rush Cover Type Avg % Cover Convex Avg % Cover Concave

Conclusions Significant difference in moss and lichen frequency between concave and convex slopes Graminoids do not show a significant difference in frequency Obvious differences in cover type Observationally more barren on convex slopes Not much difference between north and south facing Soils showed little differences (dry vs. wet) Steepness and angle create differences

Conclusions and Discussion Percent cover shows significant difference in terms of moss and lichen Also shows significant difference in graminoid cover between convex and concave More water loving plants reside in concave landscapes (Bridge and Johnson, 2009) Wind rain and other disturbances discourage plants from colonizing in convex slopes Concave have more protection from stressors Affects water runoff and fire patterns in the alpine regions (Pinder, et al. , 1997) Soils are drier and more prone to runoff on convex slopes (Gilbert, 1909)

Works cited Sakai, A. & Ohsawa, “Vegetation pattern and microtopography on a landslide scar of Mt Kiyosumi, central Japan. ” M. Ecol. Res. (1993) 8: Issue 1 pp. 47 -56. https: //doi. org/10. 1007/BF 02348606 Aandahl, Andrew R. “The Characterization of Slope Positions and Their Influence on the Total Nitrogen Content of a Few Virgin Soils of Western Iowa 1. ” Soil Science Society of America Journal, vol. 13, no. C, (1949) p. 449. , doi: 10. 2136/sssaj 1949. 036159950013000 c 0081 x. Bridge, S. r. j. and E. a. Johnson. “Geomorphic Principles of Terrain Organization and Vegetation Gradients. ” Journal of Vegetation Science, vol. 11, no. 1, (2000) pp. 57– 70. , doi: 10. 2307/3236776. Iii, J. E. Pinder, G. C. Kroh, J. D. White and A. M. Basham May, “The Relationships between Vegetation Type and Topography in Lassen Volcanic National Park. ” Plant Ecology Formerly `Vegetation', vol. 131, no. 1, (1997) pp. 17– 29. , doi: 10. 1023/a: 1009792123571. Gilbert, G. K. “The Convexity of Hilltops. ” The Journal of Geology, vol. 17, no. 4, (1909) pp. 344– 350. , doi: 10. 1086/621620.