Mechanism of interaction pasture components. Division of Forage Science and Pasture Technology

Transcription

1 Mechanism of interaction pasture components Division of Forage Science and Pasture Technology

2 Interactions Negative Positive It Depends on.?

3 Type of interaction Competition: (-,-) interaction Mutualism: (+, +) interaction Commensalism: (+, 0) interaction Exploitation: (+, -) interaction

4 Ecological pyramid Remember scavengers and decomposers can enter at any level! Tertiary Consumers= CARNIVORE EATING OTHER CARNIVORES Secondary Consumers= CARNIVORES EATING HERBIVORES Primary Consumers= HERBIVORES PRODUCERS = Autotrophic Plants

5 Ecological Pyramids Relative amounts of energy are represented in an ecological pyramid: a diagram that shows the relative amounts of energy in different trophic levels in an ecosystem. An ecological pyramid can show energy, biomass, or the number of organisms in a food web.

6 Ecological Pyramid: Energy Shows the relative transfer of energy (joules) from one trophic level to the next.

7 Ecological Pyramid: Biomass Shows the relative amounts of organic matter (gram) from one trophic level to the next.

8 Ecological Pyramid: Number of Organisms Shows the relative number of organisms at each trophic level.

9 Relationships in the ecosystem Predator/Prey: One organism (predator) will actively hunt and consume another (prey). Competition: two or more organisms of same or different species compete to use the same limited resources or basic needs

10 Symbiotic Relationships Parasitism: an organism (parasite) lives in or on another (host) and feeds on it without immediately killing it Mutualism: a cooperative partnership between two species (both benefit) Commensalism: a relationship where one species benefits and the other remains unaffected

11 Competition When all necessary growth factors are in abundance, Low supply of one vital nutrient will cause competition among forage species

12 Competition Water Nutrients Light Carbon Dioxide Oxygen Environmental stressors Means of pollination/seed disbursal

13 Competition Success of a single plant depends on how well its characteristics: Match the demands of the environment Allow it to cope with stresses as compared to neighboring plants Increase the competitiveness of the desired species and/or decrease the competitiveness of the undesirable species

14 What makes a plant a successful competitor? The plant that can: Draw on the limited factor Do so quickly Usually able to grow more roots and leaves Adaptable to several environmental conditions

15 Grazing Habits Intensity and frequency can have a tremendous affect on competitive ability of many pasture plants Pasture species vary greatly in their tolerance to grazing

16 Grazing Animals more complex pasture Selective grazing Manure and urine Treading - Walking, running, jumping, lying down, scratching, pawing

17 Management Plant height especially during leaf development and elongation Grazing frequency Grazing intensity Soil fertility

18 Management Weedy pastures Understocked lax grazing Overgrazing

19 Management Clover and grass High N from urine and fertilizer grass growth, shading of clover More frequent grazing no shading of clover, increased competitive ability

20 Overgrazing Not necessarily number of animals More a function of the time that animals are exposed to plants An overgrazed pasture is one that grows from root energy rather than solar energy Continuous grazing or inflexible rotational grazing without enough paddocks

21 Weed-crop interaction When plants grow close to each other, they interact in various in ways. Interference: It is the detrimental effects of one species on another resulting from their interactions with each other. When plants are far apart they have no effect on each other. Interaction generally involves competition and amensalism. Commensalism: This is the relationship between unrelated organism (different species) in which one derives food or benefit from the association while the other remains unaffected.

22 Weed-crop interaction Competition (allelospoly): It is the relationship between two plants (weed/crop, crop/crop, weed/weed) in which the supply of a growth factor falls below their combined demand for normal growth and development. The growth factor competed for include water, nutrients, light, space and air/gasses (oxygen, carbon dioxide).

23 Types of competition Above-ground (Aerial) competition : Takes place in the leaves and the growth factors involve are light and carbon dioxide. Below-ground(Subterranean) competition: Takes place mainly in the roots while the growth factors involve are water, nutrients and oxygen. The perceived consequence of competition with crop is reduction in the economic yield of affected crop plants.

24 Forms of competition: Intraspecific competition: competition for growth factors among individuals of a plant species Interspecific competition: competition for growth factors between two different plant species i.e crop/weed, weed/weed,or crop/crop

25 Critical Period of Weed competition/interference This is the minimum period of time during which the crop must be free of weeds in order to prevent loss in yield, it represents the overlap of two separate components (a) the length of time weeds can remain in a crop before interference begins (b) the length of time that weed emergence must be prevented so that subsequent weed growth does not reduce crop yield.

26 Factors affecting weed-crop competition Competitiveness of weed species Weed density and weight Onset and duration of weed-crop association Growth factors Type of crop and seeding rate Spatial arrangement of crops Plant architecture Growth factors availability Cropping patterns Crop type (C3 or C4 plants) Crop variety( tolerance, resistance, aggressiveness)

27 Factors affecting weed-crop competition (contd.) Environmental factors Climatic factors e.g. rainfall, temperature, wind, light etc Tillage Ground water management Soil (Edaphic)

28 Amensalism (Allelopathy) Allelopathy is the production of chemical(s) or exudates by living and decaying plant species which interfere with the germination, growth or development of another plant species or microorganism sharing the same habitat. There are two types of allelopathy:(true and Functional ) True allelopathy involves the release into the environment compounds that are toxic in the form they are produced. Functional allelpathy involves the release into the environment substances that are toxic as a result of transformation by microorganism.

29 Amensalism (allelopathy) (contd.) Examples of allelopathic plants: 1. Black walnut (Juglans nigra) 2. Gmelina arborea 3. Soghum bicolor 4. Casuarina 5. Lantana camara 6. Imperata cylindrica is allelopathic on tomato, cucumber, maize rice, glnut, olera, cowpea, pepper. 7. Cyperus esculentus is allelopathic on rice, maize 8. C. rotundus is allelopathic on barley.

30 Allelochemical complex 1. coumaric acid, 2. terpenoids, 3. - syringic acid, 4. butyric acid, 5. flavonoids, 6. phenolic compounds.

31 Plant interfere

32 Parasitism Parasitism It is a relationship between organisms in which one lives as a parasite in or on another organism. Parasitic weeds are plants that grow on living tissues of other plants and derive part or all of their food, water and mineral needs from the plant they grow on (host plants) Hemi parasite (Semi parasite) a plant which is only partially parasitic, possessing its own chlorophyll (green colour) and photosynthetic ability (may be facultative or obligate). E.g Striga hermonthica

33 Parasitism Holo parasite a plant which is totally parasitic, lacking chlorophyll thus unable to synthesize organic carbon. E.g Orobanche spp Obligate parasite a plant which cannot establish and develop without a host Facultative parasite a plant which can grow independently but which normally behaves as a parasite to obtain some of its nutrition.

34 Predation: It is the capture and consumption of organisms by other organisms to sustain life. Mutualism:it is an advantageous relationship between two organismsof different species that benefits both of them. It is obligatory and the partners are mutually dependent. Both partners are stimulated when the interaction is on. Example is the case between fungus and algae. The fungus protects the algae while the algae provide carbohydrate for the fungus. Neutralism: This is the situation where plant exert no influence on one another. Protocooperation: This is a condition whereby two plants interact and affect each other reciprocally. Both organisms are stimulated by the association but unaffected by its absence.

35 Potential Positive Impacts Proper management Maintain water quality Improve forage quality for wildlife Manage habitat and cover for wildlife Increased wildlife populations NRCS photo For further reference: NRCS photo

36 Potential Positive Impacts Water quality Riparian and meadow communities considered critical habitat in temperate zones Available drinking water High quality forages Well-managed livestock grazing can be compatible with good water quality Light or moderate grazing = no impact

37 Potential Positive Impacts Improved forage quality Small mammal & upland game birds Energy-rich seeds Vegetation Cover Forbs Grasshoppers

38 Potential Positive Impacts Improved Habitat Grazing patchy, mosaic pattern Feeding, nesting, and hiding sites Encouraged establishment of shrubs Ground squirrels and small rodents Birds of prey Selective grazing Create travel corridors Remove old grass growth

39 Potential Negative Impacts Improper Grazing Reduced nest sites for upland game and waterfowl Decreased water quality Trampled nests for waterfowl Disturbed big game during fawning Reduced cover that permits wildlife to hide from predators Reduced native fish populations

40 Potential Negative Impacts Disease transmission Animal health is important to agricultural industry and wildlife conservation

41 Properly Managed Grazing Create patchy habitat with high structural diversity Open up dense vegetation canopies Reduce coarse grass & improve quality Stimulate browse production by reducing grass biomass Use livestock to manage weeds and fire risk Create bare ground for feeding, dusting, and display areas

42 Irresponsible Grazing Reduce nest sites for upland game birds & wildlife Trample nests Disturb big game during fawning Reduce wildlife hiding cover Reduce forage for ungulates Reduce floral diversity Attract predators, parasites, or disease

43 Effects of Ranches on Wildlife Water Water sources for cattle provide water for wildlife Fences Can provide perches for birds, but also barriers of ungulates and low-flying birds Large blocks of land Areas without roads and development is generally good for wildlife Weed control Ranchers control weeds and benefit habitat Disturbance Ranching activities can disturb wildlife

44 Grazing systems can: Use strategic rest or deferment to improve nesting cover Remove livestock from fawning areas to reduce disturbance patches Stocking other pastures with moderate rates to create high quality regrowth

45 Any question?