ECOLOGICAL SUCCESSION. Prof :DEEPAK SAINI HOD ZOOLOGY J.C.D.A.V. College,Dasuya

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1 ECOLOGICAL SUCCESSION Prof :DEEPAK SAINI HOD ZOOLOGY J.C.D.A.V. College,Dasuya

2 Primary succession: The gradual establishment, through stages, of a climax ecosystem, that has not been occupied before.

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4 Primary succession will occur after a volcanic eruption

5 Primary succession occurs after a glacier retreats Image source:

6 Primary succession occurs after a glacier retreats

7 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

8 Primary succession occurs after a glacier retreats

9 Glacier Bay, Alaska

10 Secondary succession: The reestablishment, through stages, of a climax ecosystem, that has been cleared by natural or human means.

11 Secondary Succession: A bare patch of ground covered in grasses two years later

12 Secondary Succession When natural vegetation has been disturbed, removed or destroyed. Abandoned farms Burned forests Heavy pollution Deforestation A huge storm

13 Some Definitions: Sere: Another name for succession. A set of stages of evolution of an ecosystem. Pioneer stage: First stage in a sere which is dominated by opportunist species. Climax community: Populations of organisms living together in the climax stage. Climax stage: Final stage in a sere where all species are in balance. For example: A mature forest

14 Pioneer Species

15 Short life span Small adult size Many small seeds Long distance dispersal Rapid reproduction Habitat patchy High density independent mortality Habitat temporary Pioneer species tend to be r-strategists

16 Climax Species tend to be K-strategists

17 K - strategists Large life span Large adult size Few large seeds Dispersal local Successful seeding establishment rare Habitat uniform High density dependent mortality Large adult size

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19 Sequoia (redwood) trees are K-strategists

20 Lithosere: Succession on land The evolution of bare ground to forest. Pioneer species Climax forest

21 Hydrosere: Succession of ponds and lakes to forests. Describe the changes that you see.

22 Hydrosere: The gradual conversion of ponds and lakes to forest ecosystems. With time ponds and lakes are gradually filled with eroded sediments. The sediments moves in the shorelines and eventually fills in the lake. The plant sequence is as follows: lake plants, reeds, grasses, shrubs, & trees.

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25 Succession along a beach: The gradual conversion of sandy beaches and desert margins to forest. Wind moves sand into dunes Organic material, seeds, and moisture are blown in behind the dune. Hardy salt tolerant grasses and vines establish themselves trapping more soil. Plant succession follows the lithosere.

26 Succession along a beach:

27 Succession along Lake Michigan

28 Halosere: The gradual conversion or reclamation of a salt flat to forest. Salt resistant grass species move in.

29 Halosere: Grass traps organic matter and seeds soil quality (nutrients) are improved.

30 Halosere: Plant cover traps moisture, causing salt to seep into the ground. Plant succession follows the lithosere.

31 Be able to describe and explain the changes during succession.

32 Exposed Lichens rocks and mosses Small herbs and shrubs Heath mat Time Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce climax community

33 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

34 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

35 Seral Stages: Mid to Late Successional Species After 100 s of years soil deep enough Moisture & nutrients Also called Seral Community 1. Shrubs then trees colonize 2. Trees create shade 3. Shade tolerant species establish

36 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

37 What changes occur through Succession? 1. 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 2. Mineral Cycling Pioneer, physical breakdown & make organic, Later processing increase cycles expand

38 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

39 Factors in Succession 1. Facilitation One species makes an area suitable for another in a different niche Legumes add nitrogen so other plants thrive 2. Inhibition Early species hinder establishment and growth of later species more disturbance needed to continue Allelopathy by plants is an example 3. Tolerance Late successors not affected by earlier ones Explains mixture of species in Climax Communities

40 Hydrosere

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42 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.

43 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 nonmaritime terrestrial eco-system.

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46 Changes during succession Pioneer species: lichens and mosses that extract nutrients from dust and bare rock. Then: Bacteria, fungi, insects, small worms add organics to the soil Early succession plants: grasses, herbs Midsuccessional plants: grass and low scrubs Late successional plants: trees Climax community: depends largely on climate and edaphic factors

47 Climatic factors Precipitation Temperature Insolation (Incoming Solar Radiation)

48 Edaphic Factors Factors having limiting affects on plant growth that are not climatic. Soil Factors Examples: Alkalinity of soil Extreme acidity Iron toxicity Zinc deficiency Low nutrients in soil

49 Rate of Primary Succession Primary succession is fastest in humid tropics. It is slowest in the dry polar areas. Why?

50 Succession after a forest fire

51 Secondary Succession after a fire Nutrient release to soil Regrowth by remnant roots and seeds Invasions from neighboring ecosystems Rapid restoration of energy flow and nutrient cycling

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53 Secondary succession after farming

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55 Changes during succession Biomass increases Resource allocation; nutrients initially stored in soils become stored in vegetation. Mineral cycling slows

56 Changes in Energy Flow Trophic levels increase from 2 levels to 4-5 levels. More trophic levels transfer more energy. Food webs become more complex. The total productivity of an ecosystem increases. Biomass and biodiveristy is maximized in a climax ecosystem.

57 Changes in Productivity

58 Abiotic Changes ph: N: increases C: increases Exchangeable ions decrease

59 Know the factors affecting the nature of climax communities.

60 The Nature of climax communities. The system is in a stable equilibrium Remember the system is open Matter and energy may cross system boundary. Inputs are in proportion to outputs. The system changes less thus keeping habitats intact over time.

61 The Climax Community: Specialization is encouraged as all niches are occupied. Each species must enhance competitive abilities and take care of young. High nutrients available (but used) due to large amounts of biomass. High moisture available as forests capture their own transpiration and encourage rain.

62 Climax Community: Mineralized nutrients (Nitrogen) increases. Organic matter in the soil increases Mineral cycling decreases as plants are adapted to maintaining themselves and not growing or establishing themselves. These nutrients become less available to plants as they adhere to soil particles or are stored as dead matter in ground.

63 Compare early to late succession Biomass Productivity Food chains Species diversity Niche specialization Feeding relationships Size of individuals Life cycles Population control mechanisms Fluctuation Mineral cycles Stability

64 Early succession Biomass Productivity Food chains Species diversity Niche specialization Feeding relationships Size of individuals Life cycles Population control mechanisms Fluctuation Mineral cycles Stability Late succession small High high Low Short Long, complex Low High Broad Narrow General Specialized Smaller Larger? Short Long Physical More Open Low Biological Less pronounced Tend to be closed High