How to Create Disturbance Patterns

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How to Create Disturbance Patterns?

• Alternative (Conservation) Grazing
• Why grazing?
• Historical ecological process that evolved with
  grassland ecosystems (along with fire)
• Increase in plant diversity

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Milchunas et al. 1988. Am. Nat. 13287-106
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How to Create Disturbance Patterns?

• Alternative (Conservation) Grazing
• Why grazing?
• Historical ecological process that evolved with
  grassland ecosystems (along with fire)
• Increase in plant diversity
• Selectivity promotes structural heterogeneity,
  increases microhabitat diversity
• Less labor intensive, cost intensive to natural
  resource managers
• Mutually beneficial to both managers and cattlemen

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Conservation Grazing Basics

• What is light, moderate, and heavy stocking?
• Variable, but consider some visual cues
• Light grazing effects may be difficult to
  distinguish
• lt 1.0 AUM, or about 1 cow/calf pair per 6-7 acres
  or more
• Kellerton area good example ( 0.6 0.7 AUM)

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Light Stocking Rate for Iowa lt 1.0 AUM, or 6-7
or more acres per pair
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Conservation Grazing Basics

• Moderate grazing effects noticeable, but not
  overly detrimental to pasture (50/50)
• Around 1.0 AUM, depending on general growing
  capability of local soils
• Patch-burn grazing pastures in the Grand River
  Grasslands are stocked at approximately 1.0 AUM

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Moderate Stocking Rate for Iowa 1.0 AUM, or
approximately 5 acres per pair
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Conservation Grazing Basics

• Heavy most or all of vegetation removed
• Around 2.0 AUM or greater (1 cow/calf pair for
  every 2 acres or less).
• Typical pasture in Iowa

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Heavy Stocking Rate in Iowa gt2.0 AUM, or less
than 2.5 acres per pair
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Conservation Grazing Basics

• What is an Animal Unit (AU)?
• 1,000 lb. cow with or w/o calf lt6 mos old
• Why use AUs?
• More easily adapted (standardized) than figuring
  out forage utilization or production in tons/ac

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Conservation Grazing Basics

• What is an Animal Unit Day (AUD)?
• Amount of forage an AU will consume in 1 day
  (26lbs DM).
• An Animal Unit Month (AUM)?
• Amount of forage an AU will consume in 1 month
• (780 lbs DM)

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Conservation Grazing Basics

• Basic calculation for Stocking Rate
• Acres x Rate
• Time of Animal Units
• Thus, 80 acres x 1.0 AU/M
• 5 months 16 Animal Units
• (16,000 lbs. of beef)

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Conservation Grazing Basics

• 16,000 lbs. of beef is then adjusted for type of
  animal and relative size
• Charlois gt Angus cross
• Yearling heifer lt Mature cow w/calf
• Adjust as Animal Unit Equivalent (AUE)
• Smaller and growing animals (lt900 lbs)
• Add 100 to the weight and divide by 1,000
• Larger animals (gt1,100 lb)
• Subtract 100 and divide by 1,000.

Example 850-lb bison cow is equivalent to 0.95
AU
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Considerations for Grazing

• Remember, always better to be conservative to
  begin with (start low, increase if needed)
• Realize trade-offs are involved
• Strategically locate sacrifice areas

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Considerations for Grazing

• Type of grazing system
• Continuous, rotational (traditional), patch-burn
  graze
• Rotational systems very high stocking rate,
  short duration on pasturestroublesome for many
  birds
• Each system results in different vegetation
  structure

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Iowa
Burn-no graze
Fuhlendorf and Engle 2001. BioScience 51 625-632
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Considerations for Grazing

• When to graze
• Trade-offs risks to birds
• Reduced nest success, altered nesting habitat
• Changes in food resource availability
• Potential increase in predation/parasitism risk
• Perimeter/area changes
• Creation of travel lanes, greater cone of
  vulnerability

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Considerations for Grazing

• Spring (typical)
• Good to get out onto pasture if objective is
  control of cool season species
• Takes advantage of new forage growth for
  livestock
• Can be detrimental to early-nesting birds

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Considerations for Grazing

• Summer
• Avoids the nesting season
• Benefits forbs and cool season grasses
• Provides cooperating livestock producer with
  forage in late summer slump

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