Environmental Systems Measuring Biotic and Abiotic Factors of an Ecosystem Topic 3: A-J

Biotic vs Abiotic (ie physical) factors of an ecosystem Examples: Abiotic = Examples

Describe and use methods for estimating abundance of non-mobile organisms Quadrats - A quadrat is a frame of any shape that can be placed over vegetation so that species can be listed or counted, and population density, percent frequency and percent cover can be estimated.

Quadrats Method: Random Sampling vs Systematic Sampling: Evaluation: Strengths: Limitations:

Describe and use methods for estimating abundance of mobile organisms Capture-Mark-Release-Recapture Method: Random Sampling: Evaluation: Strengths: Limitations:

Capture-Mark-Release-Recapture (Lincoln Index) N= the estimated population (what you are looking for) T1: total organisms you caught and marked in 1st sample T2: total organisms you captured in 2nd sample M: the number that were marked in the 2nd sample. (meaning they have been recaptured) N = T1 x T2 M Example… So, do you have a larger population if you have a large or small “M”? Why?

Measuring Diversity 2 components of Diversity: 1. Richness = # of different species in an area 2. Evenness = a measure of relative abundance of each species in an area. (number of organisms of each type of specie) A community that is dominated by one or two species is less diverse than one that has several different species with a similar abundance, even if they have the same richness amount. Ex?

Simpson’s Diversity Index A measure of species richness of an area. A high value suggests a stable, climax community. What would a low value indicate? Abundance, using quadrats or mark-capture-release, must be done first.

Calculation D= Simpson’s Diversity Index N = TOTAL # of organisms of all species found. n = number of individuals of a particular species. D = N(N-1) Σ[n(n-1)]

Example Species N A 3 B 4 C 2 D 2 E 4 Total = N = 15 N(N-1) = 15(15-1) = 210 (210 is your top number!) n(n-1) 6 12 2 Σ[n(n-1)] = 34 (34 is your bottom number!)

Example Con’t Is this area diverse? Here is the problem: You CAN’T tell from this equation. All you can do is tell relative diversity when compared to another area/Diversity number ie: This area would be less diverse than an area whose Simpson’s Index number is 10. Only used for comparative purposes Simpson’s Index: D = N(N-1) Σ[n(n-1)] D = 15(14) = 210 34 34 D = 6.17

Identifying Organisms What could we use to identify unknown organisms? Dichotomous Keys: When making one: How many clues per number? What clues be about? Objective or Subjective?

List the variable abiotic (physical) factors of different ecosystems Terrestrial Marine Freshwater

Describe & Evaluate methods for measuring abiotic factors Precipitation: rain gauge Temperature: thermometer pH: pH strip or pH probe wind speed: aerovanes Dissolved Oxygen: DO Probe or chemical test Salinity: Hydrometer Turbidity: Secchi Disk or Secchi Tube Soil Testing: chemical tests

Environmental Gradient What is a gradient? Therefore an environmental gradient is a change in abiotic or biotic factors over an area, causing Zonation. Changes in a community along an environmental gradient due to abiotic factors. Where you can see this? How should you measure this?

Application of Measurements Both the biotic and the abiotic factors we have discussed can be measured: over time along environmental gradients and to show the effects of human impacts Through the use of __________________ All of these would need a baseline study done first!