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Fundamental Degradation Terminology NREM 612 Structure Function Initial state Degr. state lowhigh low high.

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Presentation on theme: "Fundamental Degradation Terminology NREM 612 Structure Function Initial state Degr. state lowhigh low high."— Presentation transcript:

1 Fundamental Degradation Terminology NREM 612 Structure Function Initial state Degr. state lowhigh low high

2 2 I. Ecosystem Stability Ecosystem stability is primarily a function of: Sensitivity & Resilience to change. A.Sensitivity – defined as (in Barrow 1991) “the degree to which a given environment undergoes change due to natural forces, human action, or a combination of both.” B.Resilience – defined as (in Barrow 1991) “ the way in which the ecosystem can withstand use.” C.Matrix of sensitivity and resilience can form the basis for land classification (Blaikie & Brookfield 1987)

3 3 Sensitivity ResilienceHighLow High Low Sensitivity ResilienceHighLow Higheasy to degrade easy to restore Low Think of ecosystems that would fit into each quadrat the matrix? With a partner, fill in the tables below hard to degrade easy to restore easy to degrade hard to restore hard to degrade hard to restore Sensitivity & Resilience Matrix

4 4 Sensitivity ResilienceHighLow HighMangrove Tidal salt marsh Temperate forest LowTropical rain forest Dry forest Coral reef Herbaceous wetland Rangeland

5 5 Stability Terminology II. Stability terminology A. General 1. Constancy: lack of variation in some property of a system, ability of pop. to preserve its #s 2. Persistence: survival time of a system or come component of a system

6 6 B. Terms to evaluate response to disturbance: 1. Resistance: ability to resist displacement from initial state, syn. w/ inertia 2. Resilience: ability to recover to an initial state after disturbance 3. Elasticity: speed of recovery to initial state after disturbance 4. Hysteresis: path of recovery differs from path of degradation (process or time) 5. Malleability: degree to which post-disturbance state differs from initial state Illustrate terms in figure below: Structure Function Initial state Degr. state new. state lowhigh low high Stability Terminology, con’t

7 7 II. Succession 1. From Barrow 1991: “An ecosystem returns to a climax state via a series of successional stages – which are equilibrium points reached after disturbance A.Primary succession – establishment of plants and an ecosystem on land not previously vegetated “from scratch” B. Secondary succession – recolonization of previously vegetated land following disturbance, soil remains intact

8 8 2. r-selected species: early-successional, adapted to disturbance, good dispersal capabilities, large #s of offspring, generalist, shorter lifespan 3. k-selected species: later-successional, better competitors, smaller # of offspring w/ higher survival rates, specialist, longer lifespan Succession, con’t

9 9 4. Facilitation: early successional spp. alter env. to make it more favorable for estab. of later- successional spp. 5. Inhibition: early successional spp. alter env. to make it less favorable to estab. of later- successional spp. 6. Tolerance: early spp. neither help nor hinder later spp. Succession, con’t Structure Function Initial state Degr. state new. state lowhigh low high

10 10 Relationship between stability and diversity Are diverse systems more stable than simple systems? Pimm et al. (1995)? III. Stability-Diversity Relationship A. Species Richness: # of different species in a particular area B. Evenness: relative abundance of each species represented in a particular area

11 11 Q: Which site has greater evenness? Site 1 Site 2 Q: What is the species richness (SR) for site 1 & site 2? SR for site 1 & 2 = 4 Site 1 = highSite 2 = low Q: Which site do you consider more diverse? Site 1

12 12 C. Diversity: not just richness or abundance, but relationship between richness & abundance Define these terms quantitatively: s = # of species Pi = proportion of individuals belonging to ith species Diversity s Shannon’s Diversity Index = H’ = -  P i * lnP i i=1 H’ ranges from ~ 1 – 3.5, usu. not > 4.5 Evenness = E = H’ ln(s) E ranges from 0-1

13 13 Example calculation: How to calculate H’ & E given data Site 1 Site 2 s H’ = -  Pi * lnPi i=1 E = H’ ln(s) Species  ni Pi lnPi Pi*lnPi Species  ni Pi lnPi Pi*lnPi E=

14 14 Q: Relationship between stability and diversity Are diverse systems more stable than simple systems? Pimm et al. (1995)? Stability-Diversity Relationship 1. Species Diversity: Eveness, richness, H’, etc. 2. Functional Diversity: The range and value of traits that influences ecosystem functioning; “the component of diversity that influences ecosystem dynamics, stability, productivity, nutrient balance, and other aspects of ecosystem functioning” from Tilman, D “Functional Diversity” in the Dictionary of Biodiversity

15 15 Additional Materials

16 16 D. Successional Theories 1. Clementian: holistic approach, sees succession as orderly, directional, predictable, system proceeds towards stable climax community a. autogenic-internal A B C D F. Clements

17 17 2. Gleasonian: individualistic approach, sees succession as disorderly, stochastic, unpredictable, determined by chance events, no climax community b. allogenic-external B A D C H. Gleason

18 18 Which theory is correct? Relationship of succession with stability? Relationship w/ current restoration practices? Neither, examples for which each theory works Gleasonian probably closer to reality than Clementian Clements argue that climax community = evidence of stability Gleason would discount stability altogether Self-design – Clementian Designer theory - Gleasonian

19 19 II. Sustainability Terminology A. Basic Definitions 1. Primary (1 o ) Productivity: increase in biomass of green plants over a given period 2. Sustainable Yield: fraction of net 1 o prod removed on a continuous basis w/o destroying/  1 o prod 3. Carrying Capacity: max. # of individuals supported by a given env. 4. Sustainable Development (SD): Any activity that raises social welfare w/ maximum amount of resource conservation & minimum amount of environ. degr. allowable w/i given econ, social, technical constraints a. Implies anticipate & avoid rather than react & cure mentality

20 20 a. Alpha (α) Div: w/i site or habitat b. Beta (β) Div: from site to site or along transect, gradient c. Gamma (γ) Div: diversity of a larger geographical unit, i.e. landscape or region; γ div. =  (α & β) Which site has highest α diversity? Which region has highest β diversity? Which region has highest γ diversity? Sites 1 & 3 Region Y, higher species turnover Region Y w/ higher total # of species


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