MODULE 5

• Plant ecologists


  Study the reciprocal arrangements between plants and their environment
• Ecology


  The study of the interactions between individuals and their environment
• Weed ecology


  • Gives special emphasis to the adaptive mechanisms that enable weeds to survive and prosper under conditions of maximum disturbance
  • Studies the growth and adaptations that enable weeds to exploit niches in environments disturbed by people who must practice agriculture
• Aldrich's (1984) interpretation of the weed-crop ecosystem suggests that weed management must deal with interaction of all factors rather than just two
• 3 Important weed-environment interactions


  • Climate
  • Soil
  • Biota or living organisms
• Association of weeds and crops

  Determined largely by the degree of competition offered by a particular crop and weed
• Important factors that determine a weed's ecological interactions

  • Light
  • Temperature
  • Water
  • Wind
  • Humidity
  • Their seasonal aspects – the climate
• Purple nutsedge


  Thrives in humid tropics and subtropics with some into sub-humid temperate regions
• Light intensity, quality, and duration

  • Affect weed presence and survival
  • Photoperiodic responses govern flowering and determine the time of seed maturation
  • If light is too intense or days too long or short, particular weeds won't flower and a species may not endure
• Temperature, particularly soil temperature

  • A primary determinant of seed germination and survival
  • Air and soil temperature are important determinants of species distribution and ecological interactions
• Weeds are found in the environment they prefer, and weed control or weed management often may be aided with changing the environment
• Edaphic


  Comes from the Greek edaphos, meaning "soil" or "ground"
• Soil pH


  An important determinant of what plants grow in an area, but no generalizations can be made about the influence of pH on weeds
• Field topography


  Such as altitude, slope that determines sun exposure also determine of what weeds grow
• Species


  Basic unit of classification; organisms capable of exchanging genes or interbreeding which ace fertile and able to produce as well
• Population


  Basic unit of organization; organisms that belong to an identical species that occupy an identical environment
• Species


  Group of organisms that share similar characteristics and can live within many different areas
• Population


  Group of one species that live within a particular area
• Community


  Populations of different species that live in the same area and interact with one another
• Community Assembly


  Branch of ecology that studies how plant communities are assembled over time
• Niche


  Describes species place within the community, its place in space, time, and function AKA organism's role in the environment
• Habitat


  Where the organism lives; defines the interaction of organisms with other factors (can be living or non-living)
• Weed-Crop Ecology Diagram by Aldrich (1984)

  
• Biotic Factors


  Plants composition

  Diseases

  Toxins

  Animals (insects, soil fauna, man)
• Association of weeds and crops is determined largely by

  the degree of competition offered by a particular crop and weed
• Biotic factors that affect the degree of competition

  Plant composition

  Disease occurrence

  Toxins release

  Animals (insects, soil fauna, man)
• Important factors that determine a weed's ecological interactions

  Light

  Temperature

  Water

  Wind

  Humidity

  Climate
• Photoperiodic Responses


  Govern flowering and determine the time of seed maturation