Sampleing Under Pressure - Assignment Example

Sampling Under Pressure Sampling Under Pressure Understanding ecological diversity constitutes vital aspect of social economic development. This is evidenced by the increasing amount of ecological data collected, analyzed and discussed in the recent past (Yankelevich 2008). Empirical evidence in ecological phenomena requires field measurements that can be validated and standardized. The sampling strategy employed in these studies is critical in determining the validity and usefulness of the evidence obtained.

In this lab, different sampling strategies were tested to determine their suitability in sampling a recently discovered stretch of habitat. A simple randomized sampling strategy was used to provide an estimate of the total number of species inhabiting the ecosystem. Table 1 below shows the summary of the number of species discovered from the forest and their exact population in the sample areas. According to this data, the total number of species identified is 42 % lower than the expected number, which is 42, according to the lab manual.

Table 1: Total number of species discovered and their populationSpeciesPopulationAmargosa Niterwort4Beach Jecquemontia1Big Leaved Crown Beard2Blue Tailed Mole Skink3Carters paniograss4Cave Crayfish1Chinook Salmon3Concho Water Snake3Ewa Plains Akoko2Few Flowered Navarretia3Locklomond Coyote Thistle1Lost River Sucker1Many Flowered Navarretia1Mission Blue Butterfly3Moapa Dace3Oach Tree Snail1Ouachita Rock Pocketbook1Red Cockaded Woodpecker2Rough Rabbits Foot1Sea beach Pigweed1Slender Chub 3Socorro Springsnail1Southern Combshell2Tipton Kangaroo Rat1The data also shows that more than a half of the total number of species discovered has a population of greater than three in the whole sampling area.

This low frequency number may be accounted by the nature of sampling strategy used, which aimed at getting a diverse and species rich data. To provide an estimated number of the species present in the habitat a cumulative number of new species discovered in each sample was recorded. This cumulative number was plotted against the number of samples as shown in figure 1 below.Figure 1 Cumulative frequency of new species found.The slope of the graph shows an increasing number of new species discovered with an increase in the number of the samples collected.

This association is not observed after the tenth sample where further increase in the number of samples has insignificant effect on the number of new species found. This is perhaps at this point the number of new species is nearly exhausted. A general rule to determine the total number of species can be formulated from the shape of the plot. For instance, the total number of species can be determined by taking ten samples, doubling the cumulative number of new species and subtracting 10 (the number of samples taken).

This rule however, has an error margin of 4.7 percent and still needs further validation. When applied in this lab, the rule gives an estimated number of 40 species, which is relatively closer to the exact number of species in the habitat. There are several sampling schemes that can be used to collect data in different case studies of this nature. For instance, sample random sampling would be ideal in determining the diversity of species present in this forest (Cochran, 1977), while a stratified approach would provide quality data on the distribution of species.

The advantage of using random sampling is that every point in the habitat has equal chance of being sampled. Another technique that can be employed in this case is the common non-random approach where sample sites are subjectively selected. The disadvantage of this technique is that it is prone to investigator bias and therefore may not produce reliable and generalizable data (Cochran, 1977). According to this experimental model therefore, a random and diversified sampling approach is vital in obtaining vital primary data of a newly discovered habitat.

ReferencesYankelevich S.N. (2008). What do we mean by biodiversity? Ludus Vitalis XV, 28Cochran W.G. (1977). Sampling techniques. (3rd Ed.). New York: Wiley.