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Zonation and Succession
IB Syllabus: 2.4
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Vocabulary Climax Community Community Evolution K strategists
R strategists Sere Succession Zonation
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Community A group of populations interacting in a particular area
The marine life of Hoi Ha Wan reserve The forests along Shing Mun Valley
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Communities Change Ecological Succession: the change of species composition for a specified area over time. 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 Zonation: the change of species composition spatially within at a certain point of time
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Zonation Horizontal bands or zones of animals and organisms
Differing plant and animal communities as you go up a mountain Differing plant and sea life communities as you go deeper from shore. Created by abiotic and biotic factors Change in these factors is called an environmental gradient In a rocky intertidal zone these would be Exposure (tides), salinity, competition, hydraulic action
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Source: http://hoopmanscience.pbworks.com
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Altitudinal Zonation Occurs due to changes caused by altitude during an identified period of time. Every 100m in altitude = one degree temperature decrease. Drier air caused by cooler temperatures. Changes in biotic communities caused by abiotic factors.
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Measuring changes along an environmental gradient?
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
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1. Primary Succession Begins in area with no soil on land, no sediment in water Cooled lava, bare rock from erosion, new ponds, roads Img source:
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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
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Pioneer Communities Lichens and Mosses
Survive on nutrients in dust and rock Start soil formation Trap small particles Produce organic material through photosynthesis Chemically weathers the rock Patches of soil form
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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
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Seral Stages: Early Successional Plant Species
Small perennial grasses and herbs colonize, from wind blown seeds Small plants grow close to the ground R-strategists immigrate Short lived sere Break down of rock
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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
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Mid to Late Succession After 100’s of years, deep soil forms
Holds moisture & nutrients Shrubs then trees colonize Trees create shade Shade tolerant species establish
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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 exhausted cropland in tropical rainforests. during the first two years, grasses, herbs and softwood saplings will be abundant After many more years the saplings will start to form a canopy and shade tolerant shrubs will start to develop. Eventually hardwood epiphites like ficus and banyan will develop in tandem with lianas to form a thick canopy. Each of these stages can be referred to as a seral community.
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Climax community Characterized by K-selected species
Climax community structure is in stable equilibrium for each area
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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 Specific successional stage is dependent on the frequency of disturbance Silviculture and intercrops may maintain the plagio-climax sere.
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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
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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
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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
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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
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Table 8-1 Ecosystem Characteristics at Immature and Mature Stages of Ecological Succession
Table 8-1 Page 158 Characteristic Ecosystem Structure Plant size Species diversity Trophic structure Ecological niches Community organization (number of interconnecting links) Ecosystem Function Biomass Net primary productivity Food chains and webs Efficiency of nutrient recycling Efficiency of energy use Immature Ecosystem (Early Successional Stage) Small Low Mostly producers, few decomposers Few, mostly generalized High Simple, mostly plant herbivore with few decomposers Immature Ecosystem (Late Successional Stage) Large High Mixture of producers, consumers, and decomposers Many, mostly specialized Low Complex, dominated by decomposers
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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
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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
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Aquatic Succession
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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 Resilience = the ability of a system to bounce back after a disturbance
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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
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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
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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.
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Hydrosere
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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.
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Halosere
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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.
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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.
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