Grassland Ecology

1
Grassland Ecology
Adequate, but not excessive rainfall
2
Biomes of the World
3
Grassland Ecosystems

• Herbaceous plants dominate
• Woody plants around streams
• Ecosystem in constant flux
• Balance
• Moisture
• lt30 precipitation
• soil types
• shrink/swell clays grass
• deep sands trees
• Defoliation
• Trees are defoliation intolerant
• Grasses are shade intolerant
• fire frequency is yield based
• grazing mammals, insects, etc
• nutrient cycling defoliation need
• fire Texas Gulf Coast
• dung Mesquite savannas

4
Man Made Grasslands

• Livestock vs.. forestry
• cash flow
• personal preference
• Environmental Remediation
• Key Erosion Control!!!
• Best Control
• Forest Full canopy and litter
• Problem Time to establish
• 8-50 years
• GClt60
• High erosion potential
• Good control
• Full canopy grassland
• Advantage Time to establish
• 0.2-10 years
• GCgt60
• low erosion potential

5
Ecosystem Manipulation

• Environmental
• Water
• Temperature
• Heat
• Cold
• Combined
• Perennial optimums
• warm, humid C4
• cool, humid C3
• Annual optimum
• hot, dry
• fast seeding annuals
• deep rooted perennial
• cold, dry
• hard seeded annuals
• macrobes, microbes

6
Temperature Moisture Influences on Biomes
7
Environmental Manipulation(Cont..)

• Defoliation define
• Natural
• Plains Bison, etc.
• Feast or famine
• Long undetermined rest periods based on animal
  migration, fires, weather, etc.
• Man made
• Long term, control patterns of defoliation
• shortened recovery periods
• Manipulations are/can be made to favor sward or
  animal performance

8
Defoliation Methods

• Grazing
• Livestock
• Wildlife
• Ungulates
• Vermin
• Insects
• Mechanical (Mowing)
• Forage Preservation
• Hay, Silage
• Weed Control
• Thatch
• Fire
• Natural Ecosystem Faction
• Nutrient cycling, etc.
• Inexpensive Tool
• Expensive Liability

9
Grassland EcologyEnergy flow
10
Plant Responses

• Plant height/defoliation intensity
• Taller plants are generally less tolerant of
  intense defoliation
• Apical meristem height
• lowest leaf determine grazing stubble and
  regrowth potential
• Rule of thumb Lots of exceptions
• General defoliation tolerance
• treeltshrubslttall bunchgrassltshort
  bunchgrassltshort sodgrass
• Frequency Intensity
• Frequency how often
• Intensity how much
• Note
• all plants can survive some defoliation
• all plants can be over defoliated

11
Plant Responses

• Plant Energy
• Total Nonstructural Carbohydrates (TNC)
• Chemical energy produced in leaves are stored in
  reproductive organs
• Annuals
• seeds
• tillers
• Perennials
• seeds
• tillers
• stolons
• rhizomes
• bulbs

12
Plant Responses

• Plant Energy
• TNC
• Defoliation depletes TNCs
• recovery follows leaf growth
• produce photosynthate
• store starch (energy)
• little or no leaf growth late in season
• continual clipping
• Total depletion
• Dead plant
• Early clipping
• TNC depletion
• Weak leaf growth
• Late clipping
• Weak plant before frost

13
Life cycle differences

• TNC depletion sensitivity overgrazing
• very late season
• very early season
• Annual
• Advantages
• limited old tissue
• high photosynthetic efficiency
• Single focus reproduction
• Make seeds
• usually more seeds per acre than perennial plants
  of the same species
• Overgrazing Comments
• Tolerates late season
• seed spread via manure
• VERY intolerant of early season overgrazing

• Perennial
• Advantages
• old plant tissue removal required
• Leaves increase photosynthetic efficiency
• Hormone organs
• Enhance tillering
• Other Repro. organs
• Greater TNC Storage
• Plant production greater
• Per plant
• Multiple season
• Storage
• more storage sites
• larger storage sites
• better physical barriers

14
Summary

• Grassland Ecology
• Constant Flux
• Always question relationships!
• Prairie Savannah Forest
• balanced via defoliation, moisture and soils
• energy/nutrient flow through system
• multiple uses
• erosion potentials
• Defoliation tolerance
• Frequency/intensity
• Overgrazing plant determined
• TNC flow
• Annuals seed
• Perennials storage sites
• All systems can be overgrazed

15
Suggested Internet Sites

• http//gened.emc.maricopa.edu/bio/bio181/BIOBK/Bio
  Bookcommecosys.html
• Outstanding site.
• http//gened.emc.maricopa.edu/bio/bio181/BIOBK/Bio
  BookTOC.html
• lots of topics

16
Mid Hour Assignment

• Teams and Biome
• Blackland Prairrie
• Post Oak Savannah (Graylands)
• East Texas Pineywoods
• Assignment
• Develop 10 minute presentation on the following

• Comments
• Nature Conservacy wants you to develop a
  natural system to control weeds, re-establish
  the native vegetation, and increase biome
  productivity, without chemicals.
• Develop a management plan.
• Focus on
• problem weeds
• crop (?)
• IPM principles used
• productivity issues
• logistics
• economics