1. Ecological Succession

2. Natural Changes in Ecosystems 1.Natural selection - species change (adapt) to their environment 2.Adaptive radiation - new species arise. 3.Ecological succession – changes the types of organisms that live in an ecosystem. Slide 1

3. Ecological Succession Two Types of Succession: 1.Primary Succession 2.Secondary Succession Changes in the types and amount of species in an ecosystem over time. Changes in biodiversity in an ecosystem over time. Slide 2

4. Primary Succession Change in community composition on a site which previously has had no living organisms. Very gradual, species introduced slowly. Slide 3

5. Example: Colonization following a large scale disturbance (volcanic eruption) time Slide 4 Primary Succession

6. Example: Glacial Retreat Slide 5

7. Lichen Lichens are an example of Mutualism 2 organisms, both benefit fungus and algae Lichens secrete (release) chemicals that break down rock. This type of weathering (plus wind, rain and freezing) helps produce soil. Pioneer species: organisms like lichen and plants that are the first organisms to survive and reproduce in an area. Pioneer species: change environment by producing soil and providing food for other organisms. Slide 6

8. Pioneer Species First plants to colonize an area: mosses, lichens & herbs Rapid colonizers Rapid growth (opportunistic) Relatively poor competitors in established environments Due to symbiotic relationship (algae use photosynthesis), they can survive in low nutrient environments. Slide 7

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11. Climax communities = a mature community Tropical rainforests, grasslands and deserts are all examples of climax communities. Appear to be unchanged but this is a mistaken assumption. HOW MIGHT CLIMAX COMMUNITIES CHANGE OVER TIME? Slide 10

12. Climax community?? May take 100’s or 1000’s of years to reach this stage Stage at which system has reached steady state equilibrium Most permanent of all the stages Determined by climatic or soil factors unless humans interfere (e.g. poor soil quality, grazing, preventing forest fires, selective logging) Difficult to identify Slide 11

13. Secondary Succession Succession in an area that has been cleared or modified by a disturbance and already has a soil base in place Slide 12

14. An example of secondary succession Slide 13

15. Oldfield (farming) succession Slide 14

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18. Changes During Succession Graphs showing changes in biomass and species composition with succession. Slide 17

19. Other Ecological Pyramid Changes during Succession Slide 18

20. Include events such as storms, fires, flooding, Tsunamis, droughts, overgrazing, and human activities –They damage biological communities –They remove organisms from communities –They alter the availability of resources How Natural Events Affect Ecosystems Slide 19

21. Succession due to Natural Events Slide 20

22. How Natural Events Affect Ecosystems Read p. 115 – 116 List at least one affect of each of the following on an ecosystem 1.Flooding 2.Tsunamis 3.Drought

23. Mountain Pine Beetle Insect Infestations

24. Insect Infestations Read the article on the mountain pine beetle and complete the attached assignment.

25. Insect Infestations The mountain pine beetle is a small insect, less than a centimetre long, which lives most of its life under the bark of pine trees, including lodgepole, ponderosa and western white pine. Normally these insects play an important role in the life of a forest. They attack old or weakened trees, speeding the development of a younger forest. However, unusual hot, dry summers and mild winters in central British Columbia during the last few years, along with forests filled with mature pine trees, have lead to an epidemic. To date, beetles have destroyed millions of lodge-pole pine in BC – the province’s most commercially harvested tree.

26. How Does the Beetle Damage the Pine Tree? The mountain pine beetle is as small as a grain of rice, but in large numbers it can take down the pine from the inside.It accomplishes this by attacking the trees in large groups. A female beetle starts the process by licking trees until it finds a pine mature enough — at least 80 years old. Once it has located the tree, the female begins boring through the bark, while at the same time secreting a pheromone that attracts male beetles to the site. When the males join in the attack, they too release a pheromone to attract more females, who in turn attract more males until a large enough population descends on the tree. The tree, however, is far from helpless. In response, it secretes a highly toxic resin similar to pitch to kill the beetles. Should the number of beetles attacking the tree be too few, the tree can usually withstand it.

27. But swarming isn't the only tactic the beetle has: a symbiotic relationship with a blue-stained fungus also gives it another advantage over the trees. The beetles carry spores of this fungus in compartments in their mouths, and as they tunnel their way underneath the bark of the tree, they release these spores into the tree. As the fungus spreads through the tree, it stops the spread of the toxic resin and lets the beetles continue tunnelling. The fungus and the beetles work their way through the tree, with the beetles laying their eggs in hollows created underneath the bark. The larvae born from these eggs feed on the fungus as part of their development into adults and in the process, carry away spores from the fungus inside their mouths. When the beetles emerge from the now-dead tree in search of a new host, they'll be armed with their symbiotic partner. "They are more of a complex than two separate organisms," said Allan Carroll, a research scientist with the Canadian Forest Service. "The beetle needs the fungus to feed and to stop the resin and the fungus couldn't get anywhere without the beetles." An example of mutualism.

28. Why has the beetle spread? The spread of the beetle can be traced to two separate issues: forest management and climate change. Forest management practices designed to limit forest fires have inadvertently supplied the beetles with an overabundance of mature pine to feast on. As part of an evolutionary tactic to spread at the expense of other trees, pine cones don't release their seeds until heated by fire. When other trees begin crowding a pine stand, the dense forest becomes more susceptible to forest fires. When fires do happen they clear out the old forest but leave behind the released pinecone seeds, allowing a new stand of pine tree to grow where the old one existed, unimpeded by other trees. But forest management practices geared towards preventing forest fires has allowed the trees to mature beyond their expected age, making the forests older and thus more desirable to the beetles. Carroll estimates that less than one per cent of the pine that would have historically burned from forest fires burns today. While the abundance of food is behind the population explosion, a lack of cold winters to wipe out the beetles and curb the infestations is also to blame. Pine beetles die when temperatures get below -30 C. Warming of the region brought on by climate change has also helped the beetles survive in climates it would normally find inhospitable, such as forests east of the Rockies like the Peace River valley.