Effects of aspect and elevation on the distribution of Pinyon Pine and Juniper trees, along with ind

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Effects of aspect and elevation on the
distribution of Pinyon Pine and Juniper trees,
along with index of grass density within the Los
Pinos Mountains, New Mexico
Andrea C. Westerband Sevilleta National Wildlife
Refuge and LTER Station, New Mexico REU Summer
Program 2009
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Introduction

• Interest in distribution of vegetation within a
  mountain range
• Looking for differences between north vs. south
  facing slopes (aspect) and elevation in terms of
  abundance and size

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Objective

• The Los Pinos Mountains are a poorly studied
  area, and are dominated by the Pinyon-Juniper
  Woodland
• This study will allow for a better understanding
  of the distribution of two tree species that are
  dominant along the southwestern United States

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Hypothesis

• North face will have a higher abundance of trees
  because the south face gets more direct sunlight
  in a year
• Individuals on the north face will be larger and
  more individuals will be flowering
• Percent cover of grass will be greater on the
  south face
• More individuals at lower elevation and these
  would be larger compared to those at the top
• No difference between Pinyon or Juniper

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Sevilleta is located at 34N
Courtesy of http//www.avalanche.org/uac/encyclop
edia/aspect.htm
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Study Species

• Pinus edulis
• (Pinyon pine)
• Juniperus monosperma
• (One-seed juniper)

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Study Site

• Chose two areas within the Los Pinos Mountains
  South and North Site
• Found adjacent hills in each site with similar
  elevations and topography
• Used a Trimble GPS unit to find the correct
  elevation and face

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Study Site Los Pinos Mountains
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Topographic Map of the Los Pinos Mountains
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Methods and Materials

• Used a GPS unit to find four elevations 1945,
  1950, 1970 and 1975 meters.
• Two 50 meter transects per elevation, placed
  perpendicular to the hillside
• Measured
• canopy cover
• presence/absence of cones or berries

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Methods cont.

• Also measured grass density by placing one
  30x30cm plot every ten meters along the transect

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Parameters and Assumptions

• Used altered line intercept method
• within one meter of the transect tape
• Measured all individuals, including saplings
• Assumed that the presence or absence of
  cones/berries was a good index of drought

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Results
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• Face was statistically significant in relation to
  percent cover of tree species

• Distribution of grass was not dependent on site
  or face

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• Number of Individuals flowering did not depend on
  face or site
• Whether or not an individual was flowering
  depended on the species

There is a difference between pinyon and
juniperpinyon flowered more
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Statistical Results

• ANOVA
• Logistic Model
• Both done using SAS
• Verified our assumptions of normality, and log
  transformed percent cover data to enhance
  normality
• Hill and transect rarely had a statistical
  significance and were therefore averaged together

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Statistical Results cont.

• Abundance
• Face statistically significant
• Site also significant.
• Percent Cover explained by
• Face
• Species
• Site

• P value lt.0001
• P value 0.014
• P value lt.0001
• P value 0.008
• P value 0.009
• R2 0.68

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Statistical Results cont.

• Flowering depended on the species
• P value 0.0379
• Neither grass density nor average size was
  related to site or face in a statistically
  significant way

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Summary of Key Results

• No noticeable differences between the two
  elevations
• The north face always had higher abundance of
  trees
• Pinyon dominated the north site, while juniper
  dominated the south site regardless of aspect
• Pinyon also found flowering more often than
  juniper

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• Conclusions
• Found significant differences between the south
  and north facing slopes but no differences
  between the elevationsnot high enough?
• Average size did not depend on site or face
• Percent of ground covered by trees depended on
  the site and face
• Number of trees depended on the site and face
• Flowering depended on the speciesis one hardier?

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Further Research

• Study the soil texture, pH, and moisture
• Measure amount of incoming solar radiation
• Temperature (soil and air)
• Physiological capabilities of both species
• Preliminary findings suggest that pinyon and
  juniper are not equally codominant species

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• Thank you to the REU Summer Program at the
  Sevilleta LTER
• National Science Foundation
• Sevilleta National Wildlife Refuge
• Mentor Juliana Medeiros
• Giomara LaQuay
• Jennifer Johnson
• All the REUs who helped collect data
• U.S. Fish and Wildlife

Acknowledgements
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References
Rosette scrub occurrence and fog availability in
arid mountains of Mexico. Martorell, Carlos
Ezcurra, Exequiel. Journal of Vegetation Science
13 651-662, 2002 Grazing Intensity, Aspect, and
Slope Effects on Limestone Grassland Structure.
J Range Manage 57606612, November 2004 Amezaga,
I, Mendarte, S, Albizu, I, Besga, G, Garbisu, C
Onaindia, M. Spatial structure along an
altitudinal gradient in the Italian central Alps
suggests competition and facilitation among
coniferous species. Lingua, E Cherubini, P
Motta, R Nola, P. Journal of Vegetation
Science, March 2008 published online Photosynthes
is and water-use efficiency in pinyon-juniper
communities along an elevation gradient in
northern New Mexico. Lajtha, K and Getz, J.
Oecologia (1993) 9495-101 Plant Spatial
Pattern and Nutrient Distribution in
Pinyon-Juniper Woodlands Along an Elevational
Gradient in Northern New Mexico. Padien, D and
Lajtha, K. International Journal of Plant
Sciences, Vol. 153, No. 3, Part 1 (Sep., 1992),
pp. 425- 433
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Questions?
Questions?