**Investigating Ecosystems**A transect is a line placed across a community of organisms. Transects are usually carried out to provide information on the distribution of species in the community. This is of particular value in situations where environmental factors change over the sampled distance (environmental gradient) or in the transition area between one ecosystem and another (ecotone). The usual practice for small transects is to stretch a string between two markers. The string is marked off in measured distance intervals, and the species at each marked point are noted. The sampling points along the transect may also be used for the siting of quadrats, so that changes in density and community composition can be recorded. Belt transects are essentially a form of community composition but can be difficult to carry out. Some transects provide information on the vertical, as well as horizontal, distribution of species (e.g., tree canopies in a forest).**Point Sampling**A simple line with marked points where samples are taken at intervals. The diagram shows evenly spaced sample points along the transect.**Continuous Belt Transect**Quadrats are placed along the transect continuously, providing a more comprehensive sample. The diagram shows a continuous set of quadrats lined up end-to-end along the transect.**Interrupted Belt Transect**Quadrats are placed at intervals along the transect. The diagram shows quadrats with gaps between them, indicating sampling at regular intervals along the transect.1. Belt transect sampling uses quadrats placed along a line at marked intervals. In contrast, point sampling transects record only the species that are touched or covered by the line at the marked points. (a) Describe one disadvantage of belt transects: _____________________________ (b) Explain why line transects may give an unrealistic sample of the community in question: _____________________________ (c) Explain how belt transects overcome this problem: _____________________________ (d) Describe a situation where the use of transects to sample the community would be inappropriate: _____________________________2. Explain how you could test whether or not a transect sampling interval was sufficient to accurately sample a community: _____________________________© 2007-2013 BIOZONE International ISBN: 978-1-927173-55-8 Photocopying Prohibited

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transect is a line placed across a community of organisms. Transects are usually carried out to provide information on the distribution of species in the community. This is of particular value in situations where environmental factors change over the ampled distance (environmental gradient) or in the transition area between one ecosystem and another (ecotone). The usual ractice for small transects is to stretch a string between two markers. The string is marked off in measured distance intervals, Point sampling Sample Sample Sample point point point Continuous belt transect Interrupted belt transect Sample point Sample point Continuous sampling and the species at each marked point are noted. The sampling quadrats, so that changes in density and community composition points along the transect may also be used for the siting of can be recorded. Belt transects are essentially a form of continuous quadrat sampling. They provide more information on community composition but can be difficult to carry out. Some transects provide information on the vertical, as well as horizontal, distribution of species (e.g. tree canopies in a forest). (c) Explain how belt transects overcome this problem: 2007-2013 BIOZONE International ISBN: 978-1-927173-55-8 Sample point Sample Sample point point Quadrats are placed adjacent to each other in a continuous belt Sample point 4 quadrats across each sample point 1. Belt transect sampling uses quadrats placed along a line at marked intervals. In contrast, point sampling transects record only the species that are touched or covered by the line at the marked points. (a) Describe one disadvantage of belt transects: Line of transect (b) Explain why line transects may give an unrealistic sample of the community in question: ILL Some sampling procedures require the vertical distribution of each species to be recorded (d) Describe a situation where the use of transects to sample the community would be inappropriate: Explain how you could test whether or not a transect sampling interval was sufficient to accurately sample a community: Investigating Ecosystems