Measuring biotic components of a system Ecological Sampling Measuring biotic components of a system

Ecological Sampling What is a sample? “A portion, piece, or segment that is representative of a whole” Why do we sample? it is usually impossible to measure the whole

One big assumption… That the sample is representative of the whole It is necessary to take enough samples so that an accurate representation is obtained It is important to avoid bias when sampling

Sampling Methods Transects and Quadrants Lincoln Index Plants and Non-motile animals Lincoln Index Capture –Mark- Recapture Small animals Aerial observations Large trees and animals

Sampling along Transects Samples taken at fixed intervals Set up along an environmental gradient (e.g. high to low on a mountain)

Line transect method A measured line laid across the area in the direction of the environmental gradient All species touching the line are be recorded along the whole length of the line or at specific points along the line Measures presence or absence of species

Belt transect method Transect line is laid out and a quadrant is placed at each survey interval Samples are identified and abundance is estimated Animals are collected For plants an percent coverage is estimated Data collection should be completed by an individual as estimates can vary person to person

Quadrats Used to measure coverage and abundance of plants or animals A grid of known size is laid out and all the organisms within each square are counted.

Lincoln Index Capture-Mark-Recapture n1 x n2 n3 Animals are captured,counted, tagged and released. After a period of time another capture occurs. Previously tagged animals are counted and unmarked organisms are marked. Abundance is calculated using the following formula: n1 x n2 n3 n1=total marked after catch 1 n2=total marked after catch 2 n3=total caught in catch 2 but marked in catch 1

Measurements Sampling methods measure Density Coverage Frequency Biomass Diversity

Density (D) The number of individuals per unit area D=ni/A Eg. 10 dandelions/m2 Relative density i (Rdi) The Density of species i, Di, Divided by the sum of all the densities of the other species sampled Rdi=Di/S D Eg. 10/5+8+16 ni=number of individuals for species i A=the area sampled (could be the volume V)

Coverage (C) The proportion of ground that is occupied or area covered by the plant/species Ci=ai/A Relative coverage The Coverage of species 1, Ci, divided by the sum total of the coverage of the other species sampled ai=the area covered by species i A=the total area

Frequency (f) The number of times a given event occurs Eg. the number of quadrants that contain maple trees as a ration of all the quadrants fi=ji/k Relative frequency The frequency of species i relative to the sum total of the frequencies of the other species found ji=number of quadrants with species i k=total number of quadrants

Biomass (B) Can be calculated by measuring the mass of the individuals per unit area B= S W/A More appropriate measure than density or frequency when Number of individuals in hard to determine Photosynthesis and carbon fixation, energy and nutrient transfer are more dependent upon biomass than the total number of individuals

Biomass Measurement methods Fresh or wet weight Used when organisms are alive Dry weight Used when the water content varies greatly Oven dry at 105oC to remove water Ash-Free Weight Used when inorganic content varies greatly Oxidize at 500oC until only inorganic ash remains

Diversity The measure of variety of an ecosystem Consists of 2 components The number of different species or the richness of species in a specific area The relative abundance of the individuals of each species in a specific area

Simpson's Diversity (D) Measures species richness If D is high the area may be a stable ancient site. Low D may suggest pollution, recent colonization, or agricultural management D=N(N-1) S n(n-1) D=Diversity N=total number of organisms of all species found n=number of individuals of a particular species