Terrestrial Lab I - TERRESTRIAL LAB 1 FOREST STRUCTURE In...

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TERRESTRIAL LAB 1: F OREST S TRUCTURE In the two Terrestrial Labs you will consider several aspects of terrestrial ecosystem structure and function. In this week's lab we want to examine a forest attribute called ecosystem structure . Forest community "structure" may be defined in many terms. One might describe spatially the vertical or horizontal distribution of plant or animal biomass, the total plant species present in a community, or spatially the vertical or horizontal distribution of plant or animal species, etc. During today's lab, we will concentrate on different methods of assessing plant community composition . Concepts such as species richness , species diversity , and measures of the dominance of different species are frequently used descriptors of community composition. Various indices have been used to quantify these factors. You will also be introduced to an index that is used to quantify how similar different communities are in species composition. The concept of " species diversity " incorporates both the concept of species richness (the number of species present per unit land area) and the relative abundance of those species. In general, a community with 3 species would be considered more diverse than one with two species. For two communities with equal numbers of species, however, a community in which all species are equally represented would be considered more diverse than a community dominated by a single species in which other species were represented by only one or two individuals. Species " evenness " represents how equally species are represented in a community. Indices of evenness are often simply measures of species diversity that are compared to the maximum diversity that the community would attain if all the species in it were equally represented. One analysis that is often found useful in forest structure studies is the "species-area curve". This analysis may be carried out for two reasons: to determine the appropriate plot size for sampling and to get a sense of the pattern of diversity within the larger plant community. For researchers who wish to characterize vegetation using plot methods, it is important to determine the appropriate plot size to use at the beginning of the study. For an annual grassland, plots that measure 10 x 10 cm may be appropriate. Smaller plots may not adequately sample the vegetation; larger plots may simply require that the researcher spend more time and effort on the plot without gaining much additional information on species composition, species abundance, etc. For a redwood forest, a 10 x 10 cm plot is clearly inadequate. The basal area (area of tree trunk) of a single tree would not fit in the plot. To determine appropriate plot size, researchers frequently sample sequentially larger areas, noting the total number of plant species they encounter as they increase the area sampled. Frequently, the plot of total number of species encountered vs. total area sampled plateaus. At
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This note was uploaded on 04/29/2008 for the course PCB 4044 taught by Professor Osenberg,mack during the Spring '08 term at University of Florida.

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Terrestrial Lab I - TERRESTRIAL LAB 1 FOREST STRUCTURE In...

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