Initial understory response to slash arrangements and treatments in the pinyonjuniper woodlands of n

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Initial understory response to slash arrangements
and treatments in thepinyon-juniper woodlands of
northern Arizona
Maria Irwin1, John Bailey2 and Alex
Finkral31,3Northern Arizona University,
Flagstaff, AZ 86001, 2Oregon State University,
Corvallis, OR 97331
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PJ Introduction

• Variable species composition
• Dry, Abundant and Understudied
• Managed for livestock grazing, recreation, fuel
  wood cutting and wildlife habitat
• Utterly fascinating and inhospitable ecosystem to
  work in

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Objectives

• 1. Explore the details of implementing thinning
  prescriptions in PJ woodlands, over the three
  soil types.
• 2. Use the slash created by thinning to conduct
  an experiment testing the effects of slash
  arrangement and treatments on understory (grass,
  forb, and shrub) response.

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Experimental Design
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Four Slash Arrangements
Cluster
Broadcast
Pile
No Thinning
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Four Treatments
Burn and Seed
Seed only
Burn only
No treatment
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Methods

• Vegetation Sampling in 2005
• Thinning with chainsaws
• Browns Fuel Transects
• Pyrometers
• Prescribed Fire
• Hand Seeding
• Vegetation Sampling in 2006

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Results- Thinning
Left trees in a clumpy arrangement to mimic
pre-settlement spacing
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Results- Thinning
Site C forest structure before and after thinning
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Results- Burning
Different slash arrangements create different
fuel loads, before and after burning
Average pyrometer reading for each slash
arrangement, averaged over all three stands
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Results- Seeding
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Results- Vegetation Before

• Identified 150 species in the understory,
  averaged 10 cover
• All three sites different from each other in
  richness (p0.001), and in abundance (p0.0287 )

Groups not connected by the same letter are
significantly different. n 193
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Climatic Variability

• Significant difference in richness between 2005
  and 2006 (p0.0001).
• In 2006 there was a 67 decrease in species
  richness compared to 2005

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Results- Vegetation After Abundance

• Site 1- no factors were significant
• Site 2- no factors were significant
• Site 3- no factors were significant

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Results- Vegetation After Richness
Site 1 Nothing was significant
Site 3 Significant slash arrangement factor
Site 2 treatment x slash arrangement factor was
significant
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Discussion

• Other studies (Brockway et al. 2002) have shown
  broadcasting slash benefits the understory
  community
• Understory VARIABLITY within sites, between
  sites, and between years!
• We must understand variability of PJ understory
  to interpret success or failure of management
  actions
• Thinning to pre-settlement conditions maintains
  the woodland character within the historical
  range of variability while reducing tree density

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Acknowledgements

• Dr. Alex Finkral and Dr. John Bailey
• All my field crews
• Diablo Trust
• RMRS and Carl Edminster

Check out more at http//pine.ucc.nau.edu/mri4