Download presentation
Presentation is loading. Please wait.
1
Succession IB Syllabus: – 2.3.7 Ch. 8
2
Syllabus Statements 2.1.6: Define the terms species, population, habitat, niche, community, ecosystem with reference to a named example 2.6.5 – Describe the concept and process of succession in a named habitat 2.6.6 – Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stages of succession 2.6.7 – Describe the factors affecting the nature of climax communities
3
Vocabulary Climax Community Community Evolution K strategists
R strategists Sere Succession Zonation
4
Community A group of populations interacting in a particular area
The fish community of Ponce Inlet The plant community of the scrub habitat
5
Communities Change Ecological Succession: the gradual change in species composition of a given area over time Species do change spatially within an area at a certain point in time, this is zonation not succession 2 Types depending on start point Primary succession: gradual establishment of biological communities on lifeless ground Secondary succession: reestablishment of biotic communities in an area where they already existed
6
Zonation II Horizontal bands or zones of animals and organisms
Vertical layers in a rainforest Differing plant communities as you go up a mountain Created by physical and biological factors Change in these factors is called an environmental gradient In a rocky intertidal zone these would be Drying (tides), salinity, competition, grazing
12
So how could you measure changes in biota along an environmental gradient?
Biota = living organisms Change in benthic (bottom) community of rocky intertidal with increased depth Gradient in moisture or drying Use modified quadrat method run transect into deeper water At set depths place quadrat and sample organisms Do repeated transects along your sample area Calculate differences in communities with depth
14
Primary Succession Begins in area with no soil on land, no sediment in water Cooled lava, bare rock from erosion, new ponds, roads Must be soil present before producers consumers and decomposers can exist
15
Balsam fir, paper birch, and white spruce climax community Jack pine,
Exposed rocks Lichens and mosses Balsam fir, paper birch, and white spruce climax community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Time
16
Pioneer Communities Lichens and Mosses
Survive on nutrients in dust and rock Start soil formation Trap small particles Produce organic material - photosynthesis Chemically weather the rock Patches of soil form
17
Seral Stages: Early Successional Plant Species
Small perennial grasses and herbs colonize, wind blown seeds Grow close to the ground Est. large pop. quickly in harsh conditions Short lived Break down rock
18
Seral Stages: Mid to Late Successional Species
After 100’s of years soil deep enough Moisture & nutrients Also called Seral Community Shrubs then trees colonize Trees create shade Shade tolerant species establish
19
Seral stages A seral community (or sere) is an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community. An example of seral communities in secondary succession is a recently logged coniferous forest; during the first two years, grasses, heaths and herbaceous plants such as fireweed will be abundant, after a few more years shrubs will start to appear about six to eight years after clearing, the area is likely to be crowded with young birches. Each of these stages can be referred to as a seral community.
20
Climax community Characterized by K-selected species Determined by
climate in the area – temperature, weather patterns Edaphic factors – saturated wet, mesic, arid Climax community structure is in stable equilibrium for each area Humans & other factors may maintain an equilibrium below climax E.g. current warming trends make climax rainforest communities w/ softer wood, faster growing species
21
End Result = Complex Community
Complex community mix of well established trees shrubs and a few grasses Disturbance may change the structure Fire, Flood, Severe erosion, Tree cutting, Climate change, Grazing, habitat destruction Natural or Human processes Specific successional stage is dependent on the frequency of disturbance
22
Disturbance and Diversity
Disturbance = any change in conditions which disrupts ecosystem or community structure Catastrophic or Gradual Disturbance eliminates strong competitors allowing others a chance Promotes diversity Intermediate disturbance greatest diversity
23
The intermediate disturbance hypothesis
100 Percentage disturbance Species diversity
24
Townsend et al, cited in Begon Harper & Townsend, Ecology
25
Secondary Succession Begins when natural community is disturbed BUT soil & sediment remains Abandoned farms, burned forests, polluted streams New vegetation can germinate from the seed bank In both cases succession focuses on vegetation changes
27
Mature oak-hickory forest
Young pine forest Perennial weeds and grasses Shrubs Annual weeds Time Succession of Abandoned Farmland
28
Tropical Rainforest flower Newer flowers form at the bottom
Heliconia Bracts Tropical Rainforest flower Newer flowers form at the bottom As flowers form they fill with water Support aquatic communities Newly formed bracts early succession Nutrients and organics build up Over time succession occurs Higher bracts have climax communities
29
What changes occur through Succession?
Diversity Starts very low in harsh conditions few species tolerate – r selected species types Middle succession mix of various species types – most diverse (role of disturbance) Climax – k selected species strong competitors dominate Mineral Cycling Pioneer, physical breakdown & make organic, Later processing increase – cycles expand
30
3. Gross productivity changes (total photosynthesis)
Pioneer = Low density of producers at first Middle & climax = high lots of producers and consumers 4. Net Productivity (G – R = N) Pioneer = little respiration so Net is large system is growing, biomass accumulating Middle & climax = respiration increases dramatically N approaches zero (P:R = 1) 5. Energy flow # of trophic levels increases over time Energy lost as heat increases with more transfers
31
Overview of Successional Changes
© 2004 Brooks/Cole – Thomson Learning Early Successional Species Rabbit Quail Ringneck pheasant Dove Bobolink Pocket gopher Ecological succession Midsuccessional Species Elk Moose Deer Ruffled grouse Snowshoe hare Bluebird Late Successional Species Turkey Martin Hammond’s flycatcher Gray squirrel Wilderness Species Grizzly bear Wolf Caribou Bighorn sheep California condor Great horned owl
32
Factors in Succession Facilitation Inhibition Tolerance
One species makes an area suitable for another in a different niche Legumes add nitrogen so other plants thrive Inhibition Early species hinder establishment and growth of later species more disturbance needed to continue Allelopathy by plants is an example Tolerance Late successors not affected by earlier ones Explains mixture of species in Climax Communities
33
Predictability of Succession
Generally predictable end of succession is a Climax community Only real rules are Continuous change, Instability, and unpredictability Ever changing mosaic of patches in different successional stages No real progression to an end, rather we see a reflection of an ongoing battle for resources and reproductive advantage
35
Aquatic Succession
36
Ecological Stability & Sustainability
Maintained by constant dynamic change Positive and Negative feedback systems Community may change but you will still recognize it as a particular type of community Inertia = The ability of a living system to resist disturbance Constancy = the ability of a system or population to keep its numbers within limits imposed by resources Resilience = the ability of a system to bounce back after a disturbance
37
Diversity vs. Stability
Once thought that higher diversity = more stability for a community or ecosystem Recent studies by D. Tilman on grasslands suggest More species higher NPP more stable Population #’s for individual species in diverse ecosystems fluctuate more widely Some level of diversity does provide insurance against disasters Nature is in a continual state of change
38
The Precautionary Principle
Human disturbances are disrupting ecosystem processes Our ignorance of long term effects means we should be cautious Thus, “When there is considerable evidence that and activity threatens human and ecosystem health, we should take precautions to minimize harm, even if the effects are not fully known.” Better safe than sorry…
39
Environmental degradation Vanishing biodiversity
Grizzly bear NORTH AMERICA Spotted owl Black- footed ferret Kemp’s ridley turtle California condor Golden toad Columbia has lost one-third of its forest Black lion tamarin SOUTH More than 60% of the Pacific Northwest coastal forest has been cut down 40% of North America’s range and cropland has lost productivity Hawaiian monk seal Half of the forest in Honduras and Nicaragua has disappeared Mangroves cleared in Equador for shrimp ponds Southern Chile’s rain forest is threatened Little of Brazil’s Atlantic forest remains Every year 14,000 square kilometers of rain forest is destroyed in the Amazon Basin Coral reef destruction Much of Everglades National Park has dried out and lost 90% of its wading birds ATLANTIC OCEAN PACIFIC Manatee Chesapeake Bay is overfished and polluted Fish catch in the north-west Atlantic has fallen 42% since its peak in 1973 Humpback whale St. Lawrence beluga whale Eastern cougar Florida panther Environmental degradation Vanishing biodiversity Endangered species 6.0 or more children per woman
40
Many parts of former Soviet Union are polluted with industrial and radio- active waste ASIA Poland is one of the world’s most polluted countries Central Asia from the Middle East to China has lost 72% of range and cropland Imperial eagle Giant panda EUROPE Japanese timber imports are responsible for much of the world’s tropical deforestation Area of Aral Sea has Shrunk 46% Snow leopard Mediterranean 640,000 square kilometers south of the Sahara have turned to desert since 1940 Saudi Arabia Asian elephant Deforestation in the Himalaya causes flooding in Bangladesh Liberia Oman Kouprey Mali AFRICA Eritrea Yemen 90% of the coral reefs are threatened in the Philippines. All virgin forest will be gone by 2010 Burkina Faso India and Sri Lanka have almost no rain forest left Niger Benin Ethiopia Chad Golden tamarin Sierra Leone Nigeria Togo Congo Rwanda Burundi Uganda Sao Tome Somalia In peninsular Malaysia almost all forests have been cut 68% of the Congo’s rain forest is slated for cleaning Queen Alexandra’s Birdwing butterfly Angola Indonesia’s coral reefs are threatened and mangrove forests have been cut in half Zambia INDIAN OCEAN Nail-tailed wallaby Fish catches in Southeast Atlantic have dropped by more than 50% since 1973 Aye-aye AUSTALIA Black rhinoceros Madagascar has lost 66% of its tropical forest Much of Australia’s range and cropland have turned to desert Blue whale A thinning of the ozone layer occurs over Antarctica during summer ANTARCTICA
42
Hydrosere A hydrosere is simply a succession which starts in water. A wetland, which is a transitional area between open freshwater and dry land, provides a good example of this and is an excellent place to see several stages of a hydrosere at the same time. In time, an area of open freshwater such as a lake, will naturally dry out, ultimately becoming woodland. During this process, a range of different habitats such as swamp and marsh will succeed each other. This succession from open water to climax woodland is likely to take at least two hundred years (probably much longer). Some intermediate stages will last a shorter time than others. For instance, swamp may change to marsh within a decade or less. How long it takes will depend largely on the amount of siltation occurring.
43
Hydrosere
45
Halosere The term Halosere is an ecological term which describes succession in a saline environment. An example of a halosere would be a salt marsh. In river estuaries, large amounts of silt are deposited by the ebbing tides and inflowing rivers. The earliest plant colonizers are algae and eel grass which can tolerate submergence by the tide for most of the 12-hour cycle and which trap mud, causing it to accumulate. Two other colonisers are salicornia and spartina which are halophytes -i.e. plants that can tolerate saline conditions. They grow on the inter-tidal mudflats with a maximum of 4 hours' and exposure to air every 12 hours. Spartina has long roots enabling it to trap more mud than the initial conlonizing plants and salicornia, and so on. In most places this becomes dominant vegetation. The initial tidal flats receive new sediments daily, are waterlogged to the exclusion of oxygen, and have a high pH value. The sward zone, in contrast, is inhabited by plants that can only tolerate a maximum of 4 hours submergence everyday (24 hours). The dominant species here are sea lavender and other numerous types of grasses.
47
Halosere
48
Xerosere Xerosere is a plant succession which occurs in conditions limited by water availability or the different stages in a xerarch succession. Xerarch succession of ecological communities originated in extremely dry situation such as sand deserts, sand dunes, salt deserts, rock deserts etc. A xerosere may include lithoseres and psammoseres.
49
Psammoseres In geography, a psammosere is a sand sere - an environment of sand substratum on which ecological succession occurs. In a typical succession on a sea-coast psammosere, the organisms closest to the sea will be salt tolerant species such as littoral algae and glasswort. Progressing inland the succession is likely to include meadow grass, sea purslane, and sea lavender eventually grading into a typical non-maritime terrestrial eco-system.
Similar presentations
