Field Course Results Paper.doc

sarah pellkoferyu-chuan wangsidrah irshad24.7.2011masters field course 2011 project summaryabstracttheintermediate disturbance hypothesis predicts that species diversity in a local environment will be higher in a moderately disturbed environment than in one that has very high or very low levels of disturbance. (dial 1988). we tested this theory near the village of gwest and gschenenralp at the 2011 masters field course by sampling both invertebrate and plant biodiversity levels at four sites; each site being characterized by their distinguishable levels of disturbance through human-induced management practices. sites ranged from completely unmanaged to highly managed and the local environmental conditions of each site, including soil ph, temperature, relative humidity, and soil conductivity were also taken into account as explanatory variables in the study. after comparing all of our results we found that, in line with the intermediate disturbance hypothesis, the site that had a mid-level amount of human induced disturbance had the greatest total species abundance and species diversity. the positively sloped confidence intervals in our study show that the number of sites sampled was too low, therefore we suggest that future studies include more sample sites in order to capture a picture of the true number of species present. introductionfigure 1: the intermediate disturbance hypothesis (idh) (a) competitive exclusion causes species diversity to be low when there is a small amount of disturbance. (b) an intermediate amount of disturbance results in a greater amount of diversity because of the presence of a good colonizer and competitor species. (c) species diversity is low again with a large amount of disturbance because only the most tolerant species and strong colonizers can survive (hughes, 2010)the intermediate disturbance hypothesis(idh) is a theory that states that “local species diversity is maximized when ecological disturbance is neither too rare nor too frequent” (dial, 1988). the explanation given for this is that at low levels of disturbance only the most competitive species will be present because they will outcompete and push all other species to extinction. when the disturbance levels are too high most species will face extinction. according to idh a happy median between these two extremes is where species diversity will be maximized (figure 1). this is due to the coexistence it allows between the species that specialize in competition and those that are more opportunistic. this coexistence is possible due to the varying life history strategies that the species employ. species that are more competitive over time, called k-selected species, tend to invest more resources into long term growth and competition in stable ecosystems. the more opportunistic species, called r-selected species, conversely invest their resources into being able to quickly colonize recently disturbed areas (macarthur and wilson, 1967). therefore, in line with the idh, an area that has a mid-frequency of disturbance occur allows both species to share dominance in the same location over time.the noted disturbance that was taken into account in this experiment was human-induced. this is becoming more commonly the case with ecosystems around the world due to increases in human population and the human environmental footprint (rees, 1992). human-induced local environmental disturbances can include but are not limited to farming, forest fires, livestock-grazing, and deforestation. the local environmental disturbances that our study took into account were due to the intensity of current farming or the amount of time since the cessation of past farming practices on the local site.methodsthere are 4sites, intensive, extensive, goat, each side we have different data, air humidity of ground and 2m above ground, insects tracker, plants around the track, soil ph, conductivity and par (phototosnythetically active radiation).1. each site has 5 tracks and 30 meter between each track (figure 2,3) for catching insects. dig a hole, which allow fitting the pipe and installing alcohol, funneling.pipealcoholsoilfunnelroofsurfacefigure 2figure 32. collecting plants from two 1m*2 areas, which one meter away from each track.(figure 4)right side of the track called a or 1, left side called b or 2 and cut as much vegetation as possible.figure 43. par (phototosnythetically active radiation) , gps and air humidity. results1. insect diversity depending on siteinsectdiversitysitesdat$site dat$trap boxplot(dat$div_totdat$site) m m m 1 2 3 4 3.6 4.4 3.0 3.6 s s 1 2 3 4 2.607681 3.209361 1.581139 1.516575 b b ,11, 0.72, 1.93, 3.14, 4.3 s s 1 2 3 4 2.607681 3.209361 1.581139 1.516575 segments(b,m+s,b,m-s) tapply(dat$div_tot,dat$site,mean) 1 2 3 4 3.6 4.4 3.0 3.6 m m2 summary(m2) df sum sq mean sq f value pr(f) dat$site 3 746.15 248.717 5.1444 0.01321 *ph 1 28.72 28.717 0.5940 0.45370 conductivity 1 125.23 125.226 2.5902 0.12984 residuals 14676.86 48.3473. from 1.and2. shows that site 2 has the most species in both insect and plant compare to others.conclusionthe ecological communities, diversity of species and there richness depend on two major determinants productivity and disturbance. the results and theoretical models in our experiments show that species richness shows a peak at intermediate levels of both factors. our experimental results and responses show patterns of disturbance and attributed differences among species richness and productivity which can be explained by simple unimodal where all species are ecologically identical. our findings suggest that the current neutral theory can be used to explain patterns of species responses to the major determinants.bibliographydial