SUCCESSION Community & Ecosystem Change over time

Transcription

1 Schueller NRE 509: Lecture 23 SUCCESSION Community & Ecosystem Change over time 1. Forest study revisited 2. Patterns in community change over time: 3 cases 3. What is changing? 4. What determines the rate and direction of change?

2 Is Scio Woods changing or stable?

3 Time machine: A look at change over long time periods

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5 14kya present

6 Communities change over time How? What do we observe? What would we measure?

7 COMPOSITION Species list and counts of each: Are certain species or groups (guilds, taxa) present or absent? What is the relative abundance (proportion of total # individuals, biomass, or cover) of certain species? Are certain species dominant/rare? What is the diversity?

8 STRUCTURE Number of trophic levels Vegetation/ structures Height/density of layers, width of zones

9 Pollination NPP Biomass Available Nitrogen Nutrient outputs Leaf litter thickness Soil OM Microbial activity FUNCTION

10 Schueller NRE 509: Lecture 23 SUCCESSION Community & Ecosystem Change over time 1. Forest study revisited 2. Patterns in community change over time: 3 cases 3. What is changing?

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12 Exit Glacier, Alaska

13 Exit Glacier, Alaska

14 0 350 years

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16 Communities change over time How? Case 2: Abandoned agricultural field Old Field in Florida

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18 1 month after abandoned

19 5 years after abandoned

20 15 years after abandoned

21 40 years after abandoned

22 Western Pennsylvania field 1, 2, 5, 20 years

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24 Case 3: A walk to Lake MI sand dunes

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26 Cowles (1899). The ecological relations of the vegetation on the sand dunes of Lake Michigan. Botanical Gazette chronosequence

27 Communities change over time SUCCESSION = Non-seasonal, directional* process of one community replacing another * from early/ pioneer community to stable/ climax community Clements (1936)

28 Schueller NRE 509: Lecture 23 SUCCESSION Community & Ecosystem Change over time 1. Forest study revisited 2. Patterns in community change over time: 3 cases 3. WHAT is changing over time (from early/pioneer to late/climax community)?

29 Communities change over time General patterns observed? List the patterns of change in composition, structure & function

30 Plant community composition & structure dominant spp. & growth forms

31 What kind of species do you see in early vs. late succession? Early Late Small, short-lived Large, long-lived annuals perennials

32 Plant community composition

33 Animal community composition

34 Species richness 1 1. Plant species at Glacier Bay, Alaska 2. Plant species in Minnesota old fields 3. Woody plant species and 4. Bird species in Piedmont Plateau of North Carolina X = Years or Age of community

35 Ecosystem function - Old fields: Increase in depth of soil organic matter - Glaciers: Increase in soil OM, moisture, nitrogen

36 NPP (Mg ha -1 y -1 ) Ecosystem function 200 NPP Biomass Plant Biomass (Mg ha -1 ) Time (Yrs) 3

37 Schueller NRE 509: Lecture 23 SUCCESSION Community & Ecosystem Change over time 1. Forest study revisited 2. Patterns in community change over time: 3 cases 3. What is changing? 4. WHY is it changing (or not!) over time? Stability vs. change? What causes the direction and rate of change?

38 Communities change over time General patterns observed? What is different?: What initiates it? Two types of succession

39 Start from scratch: no developed soil no seed bank Primary Succession Very intense/prolonged disturbance (volcanic eruption, glaciation, etc.)

40 Secondary Succession Start with: soil structure & OM some plant life (resprout) and/or seed bank (germinate) Incomplete disturbance: hurricane, fire, grazing

41 Old Field Succession Primary or Secondary? For more on Old field succession (abandoned agriculture) in New Jersey, North Carolina, Australia, Puerto Rico,. See also:

42 Secondary succession of an urban ecosystem: 5 years of after abandonment Fukushima (2011)

43 Mt. St. Helens

44 Lessons from Mt. St. Helens Heterogenous disturbance Biological legacy effects What physical, biological, and human factors and interactions effect the outcome of succession at any one spot?

45 PREDICT how any two of the following species or events influence the rate/direction of succession of a field along the Huron River 1. Beaver 2. European Buckthorn (Nitrogen-fixing invasive plant) 3. Fruit-eating birds 4. Fire

46 What can you say about the ecological history of this place?

47 Ecosystem engineer - single species -> community change Beaver Eel grass

48 PREDICT how any two of the following species or events influence the rate/direction of succession of a field along the Huron River 1. Beaver 2. European Buckthorn (Nitrogenfixing invasive plant) 3. Fruit-eating birds 4. Fire

49 Invasion by non-native nitrogen-fixing tree in Hawaii (Myrica faya) Vitousek et al. a. Native plants limited by N, especially in early succession b. Soils with Myrica have more N c. So facilitation, but ecosystem process altered

50 PREDICT how any two of the following species or events influence the rate/direction of succession of a field along the Huron River? 1. Beaver 2. European Buckthorn (Nitrogen-fixing invasive plant) 3. Fruit-eating birds 4. Fire

51 What would increase the rate of succession of an abandoned field in tropical rain forest? (Manioc in Suriname)

52 Case: Assisted Natural Regeneration (ANR) of Australian wet tropical forest Barriers to forest regeneration removed by 1) suppressing grass with herbicide, and 2) adding structures to attract seed dispersers. Relative to untreated pasture, seedling densities 20 months after treatments increased by: 50x for herbicide only, 800x for herbicide beneath perches, 1500x for herbicide beneath pre-existing small trees 0Fact%20Sheet_formatted_draft_v9_July14.pdf

53 PREDICT how any two of the following species or events influence the rate/direction of succession of a field along the Huron River? 1. Beaver 2. European Buckthorn (Nitrogen-fixing invasive plant) 3. Fruit-eating birds 4. Fire

54 Fire History and misconceptions

55 Fire Communities adapted to fire

56 Fire Prescribed burns reduce invasive shrubs, maintain a successional stage

57 Generally, what causes the direction and rate of change? 1. Species Interactions 2. Disturbance

58 Key drivers of succession: 1. Species interactions The first to arrive might: a. facilitate (+), b. inhibit (-), or c. not affect (0) the species that arrive later

59 Facilitation Alder and post-glacial succession Early species help later species.

60 Facilitation Example 2: Nurse plants in deserts Early species help later species.

61 Inhibition Coral reefs and intertidal shores Early species hinder later species.

62 Tolerance e.g. Shade tolerance Early species do NOT help or hinder later species. Late species tolerate & outcompete early species

63 3 species interaction models of succession: self-test 1. In facilitation, pioneers make the environment [more /less] favorable for later species, and later species [coexist with / outcompete] pioneers. 2. In tolerance, the first to arrive [help/hinder/neither] later immigrants, and later species [tolerate/outcompete] early species. 3. In inhibition, the first to arrive [assist/prevent] later immigrants by altering environment or [ ]. Species are replaced when there is death or [?]

64 When are facilitation, inhibition, or tolerance likely to be most important? 1. Primary vs. secondary succession? 2. Early vs. late succession?

65 What kind of species (life history traits) would you predict in early vs. late succession? Number of offspring Offspring size Growth rate Adult size Early r Late K When do you see better colonizers? Better competitors? Disturbance-adapted species? Lifespan Small, short-lived Large, long-lived annuals (pioneers) perennials

66 Generally, what causes the direction and rate of change? 1. Species Interactions 2. Disturbance

67 Key drivers of succession: 2. Disturbance How do different types of disturbance change species interactions? Which species are present? Diversity? Grazing by migrating bison Tree fall Hurricane Timber harvest Volcanic irruption Bulldozer Tilling

68 Key drivers of succession: 2. Disturbance How does the intensity, frequency, and scale of disturbance ( disturbance regime ) affect diversity?

69 Very intense/large disturbance: = Succession starts over (Primary Succession)

70 Less intense but repeated disturbance: = Early/mid secondary succession

71 Repeated but infrequent disturbance = Mostly late successional species Time

72 Repeated but small scale disturbance = Mix of successional stages Space

73 Key drivers of succession: 2. Disturbance How does the intensity, frequency, and scale of disturbance affect species richness? Early primary succession Early/mid secondary succession Mostly late successional species Mix of successional stages

74 Can intermediate disturbance (patches of different successional stages) really increase diversity? Intermediate Disturbance Hypothesis (Connell 1978) Frequently used in management (prescribed burns), but lots of empirical evidence does not support this hypothesis! Why not?

75 FLASH BACK Models Metapopulation proportion of patches occupied (p) is a balance between Extinction (e) and colonization rate (c) p = 1 e_ c So dynamics in patch occupancy: Proportion occupied Proportion unoccupied But this is not realistic other factors influence whether the species is there or not

76 Dynamics of patch occupancy (is the species there or not) is a balance between Extinction (e) and colonization rate (c) To explain theory & evidence mismatch add effect of: 1. Resources (productivity) - increases colonization 2. Disturbance increases extinction 3. Loss by competitive exclusion by another species k Likelihood that a species is there (it got there and it has resources) minus not there (it dies, gets disturbed, or is outcompeted by another species) Kondoh, M Unifying the relationship of species richness to productivity and disturbance. Proc. Roy. Soc. Lond. 268:

77 Implications: Intermediate disturbance will not always lead to higher diversity, and may lead to extinction! The effect of disturbance depends on productivity of a site (because changes who wins good competitors or good colonizers) Using a more realistic model: Can determine the ideal disturbance level from field data on P, m, and R Kondoh, M Unifying the relationship of species richness to productivity and disturbance. Proc. Roy. Soc. Lond. 268:

78 Self assess (take your time) How do primary and late successional sites differ? Early and late? What are some real world examples? How could you recognize that you were in an early primary succession site? How would this differ from an early secondary succession site? Late? List a variety species traits or soil characteristics you could use to distinguish them. How could you change the rate or direction of succession using a species that facilitates other species? How would introduction of an inhibitor species alter succession? Does intermediate disturbance always lead to more diversity? Why or why not?