An experiment was done to find out whether there was a difference in the number of organisms in the coniferous and deciduous woodlands. A quadrat of 10m by 10m was used and co-ordinates 5,1 5,2 5,3 5,4 5,5 5,6 5,7 5,8 5,9 5,10 were used because these were exactly in the middle of the quadrat area. Ten samples of leaf litter and ten samples of humus was obtained from each woodland.
In the laboratory tullgren funnels were set up, the samples were tested and the organisms were collected. A results table was made to record the numbers of organisms in.
The results were displayed in graphs and tables. The graphs show the average number of each organism and the actual number of each organism in each of the woodlands. In the third graph five significant organisms have been picked out. This is because they have significant values and reasons for these values.
The tullgren funnel was set up using a certain amount of the leaf litter that acted as a sieve that the organisms could fall through from the humus that was placed on top of the leaf litter.
20g of humus and 10g of leaf litter was used in the tullgren funnel because only a small amount was needed. A 100w bulb was used in both experiments (for each woodland). The organisms were driven, by the drying effect of the bulb, down the tullgren funnel and eventually they fell into the 30cm3 of ethanol. The organisms died but their bodies were preserved so that at the end of five days the different organisms in the ethanol and the larger organisms in the dried up leaf litter could be identified and recorded using a microscope and a dichotomous key.
This method was used because it was the most reliable, and ensured that all organisms present were removed from the sample in the tullgren funnel. Some very small organisms that were not affected by the drying effect of the bulb were not counted. During the experiment predation between organisms were occurring, this was not accounted for.
The average test and the t-test were used, because two averages were being compared and there were less than 25 unmatched organisms in each sample. The value of t = 5.524 was greater than the value given for 22 points of freedom so that the Ho (null hypothesis) was rejected and the alternative hypothesis was accepted.
Therefore the assumption, that the number of organisms are greater in the deciduous woodland, can be made. So the number of organisms did differ in the deciduous and coniferous woodland.
The decomposition rate in the deciduous woodland is faster because organisms such as the earthworm can survive in this environment, because this environment is more alkaline than the coniferous woodland, which is more acidic. If conditions are less acidic then organisms such as the earthworm can survive and continue the fast decomposition, keeping the surrounding environment more alkaline. This is a negative feedback effect. So the number of species was greater deciduous woodland, with the exception of Springtails and small spiders. This is because these organisms have adapted to the acidic conditions of the coniferous woodland.
In the deciduous woodland where the experiment was done, many different species of trees were growing. These trees have large, thin green leaves, to absorb the maximum amount of sunlight available. When these leaves fall off the trees to the ground, detritivores such as the worm, start the chain of decomposition. Without the detritivores the saprophytes (bacteria) cannot continue the process, after the detritivores, of breaking down the complicated organic matter.
These leaves have a large surface area for detritivores to start the process of decomposition. Decomposition occurs relatively quickly therefore the layer of leaf litter will be thinner.
However, in the coniferous woodland where the experiment took place there was only one species of tree and that was the pine. The pine needles are long and thin which are thought to increase the surface area for the absorption of sunlight.
This surface area is also where, when the pine needles fall to the ground, the detritivores start the process of decomposition. Because of the conditions in the coniferous woodland the detritivores take longer to decompose the leaf litter. Therefore if the rate of decomposition is slow, and the rate of the pine needles falling are fast, then there will be more leaf litter on the ground of the coniferous woodland than on the floor of the deciduous woodland.
The exotic conifer grows at a faster rate than the native broardleaves. Because the conifer is exotic, there are few insects and birds associated with it and so the exotic conifer is useless for use by native organisms. Because conifers are planted as a monoculture they are easy to manage (i.e. planting, weeding, fertilising, etc). But each tree needs exactly the same amount of nutrients and water because they are of the same species. This causes a deficiency of nutrients in the soil and so fertilisers have to be used. This could eventually lead to pest epidemics and so pesticides may also be needed.
When a monoculture is planted, all the trees are of the same age and so are easily managed because there is little variation in height. The conifer woodlands and forests are planted in straight lines and are therefore easier to manage. However, this arrangement looks odd and unnatural because trees in a deciduous woodland are not planted in this way. If the conifers are planted densely then this ensures reduced side branch growth and increased height (therefore increasing the value of the timber). If all the trees are removed at the same time there will be a drastic change of the landscape which may result in a large amount of soil erosion.