Changes in Species Richness and Assemblage Due to Ecological Succession on Rangitoto Island 2012

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Successional sequence for flora species and changes in richness and assemblage due to ecological succession on Rangitoto Island, New Zealand

Successional sequence for flora species and changes in richness and assemblage due to ecological succession on Rangitoto Island, New Zealand

Abstract:
A survey of 12 different areas of various sizes was done in the study of whether or not species richness increased with ecological succession, using the areas of vegetation growth as a benchmark for stages of succession. The results proved inconclusive as to whether or not species richness increased indefinitely as succession progressed by proved that species richness and species density increased from early to mid-successional stages.

Introduction:
Rangitoto Island is geologically a young island, formed approximately 600 to 700 years ago due to volcanic eruptions. It is because of this, the island is still in various states of ecological succession and some areas have not even begun the process and remain broken fields of lava-rocks, which is why the island was chosen as a good idea to study ecological succession. The island is very dry as no streams or fresh water reservoirs are present on the island. Therefore, the series of succession being studied could be classified as a xerosere and a lithosere. (Department of Conservation, 2012) The study on how ecological succession changes the species richness and assemblage in the region is done to prove the hypothesis that there is a positive correlation between species richness and the progressing stages of ecological succession. Rangitoto Island was chosen due its relative young age in geographical terms providing a good comparison of different stages of succession within the same ecosystem environment. A successional sequence of plants found can be assembled using the compiled data. Figure 1 (Below): Picture shows the barren lava fields and the start of succession by herbs along the foot path and shrubs in sparse patches along with larger areas of both shrubs and trees in the background. Source: http://en.wikipedia.org/wiki/File:Rangitotolavapath.jpg Figure 2 (Above): Satellite picture of Rangitoto Island, the outlined route is the path taken during data collection, with the approximate areas for data collection highlighted as a grey box. Source: Google Earth

Figure 1 (Below): Picture shows the barren lava fields and the start of succession by herbs along the foot path and shrubs in sparse patches along with larger areas of both shrubs and trees in the background. Source: http://en.wikipedia.org/wiki/File:Rangitotolavapath.jpg Figure 2 (Above): Satellite picture of Rangitoto Island, the outlined route is the path taken during data collection, with the approximate areas for data collection highlighted as a grey box. Source: Google Earth

Method - Study Site Description:
The area on the island chosen is similar to the area pictured above in Figure 1 in the approximate area as highlighted in Figure 2. Such an area was chosen as it contains a variety of areas in various stages of succession as observed by noting that there are patches of vegetation of various sizes. This would give the study the scope it requires to test the hypothesis stated earlier. The general type of vegetation found were a combination of lichens, mosses, ferns, grasses (Astelia spp.), trees and shrubs. However, in this study, only ferns, trees and shrubs would be included in the quantitative analysis of data. The substrate of the surveyed areas seems to be composed of organic matter, such as dried leaves, sticks and soil. Qualitative observation shows the areas without vegetation show little organic matter deposits and remain barren rock, with occasional early succession by lichens evident in some areas. The nature of the vegetation patches being surveyed shows that larger patches of vegetation usually contain a larger variety of species but also plants that may belong to latter stages of...
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