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Ecology and Evolution

Rangitoto Island

Successional sequence of plants on the Rangitoto Island while testing the hypothesis of

species diversity increases with area of vegetation patch increases.

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Abstract 105

Rangitoto Island s is a volcanic island near Auckland which thrives in species richness. So we tested to see if there is a relationship between the number of species to the area of the vegetation patch. To gather results in most effective manner we formed groups of 4 and went out observing the amount of species in different sizes of vegetation patches in Rangitoto Island. Form the results we gathered we found that the number of species increases as the size of the vegetation patch increases. Therefore we conclude that there is a relationship between the numbers of species to the size of vegetation patch.

Introduction 129

When looking at forests the larger the area the more species that survive in the area. Using this theory we can assume that species richness depends on area size. Since Rangitoto is a volcanic island which is covered with lava rocks with very little water supply to the plant species, Rangitoto provides a good opportunity to test the theory if there is a relationship between the species and area. The relationship that could be noticed is a positive relationship between number of species and patch size. We can also test the ecological succession of Rangitoto and see if there is a trend with species after the volcanic eruption. Therefore the topic for this experiment is the Successional sequence on Rangitoto and the species diversity in relation with patch area.

Methods 216

Rangitoto is the youngest and the largest active volcanic island in Auckland. It is covered with regenerating bush and barren lava flows. The island has more then 200 vegetation species which grow in small to large area patches. This patches can be used to test the hypothesis of the relationship between the number of species and the vegetation size.To test if the hypothesis, we formed team of 4peopple from a group of 11people and selected 4 patches at random at a allocated part of the island with a help of our supervisor. The area of the patch was then measured either by measuring the radius of the patch or by taking the length and width of the patch. Using the mathematical formulas (Area= pie x radius squared or area= length x width)we calculated the patch areas. If the radius of the patch was less then 2m then it was a small patch, smaller then 6m it was a medium patch and if larger then 10m it was a large patch. This was recorded, with the number and type of different species in a table. Therefore a total of 12 patches of 3small, 6 medium and 3 large patches were observed. The results collected by the 3 teams were combined and used to prove the hypothesis.

Results 194

The aim of this experiment was to find if there is a relationship between species richness and area size and the ecological succession on Rangitoto. After collecting all the data from the area chosen at random, found that results of the experiment show that the hypothesis is correct, that the number of species does increase with the area size increases. The diversity of the species grew as the area of the vegetation patch increased, see figure 1 and in the Species Summary Table. The results also showed that there is a trend in the species of each data set from different teams and patch area. The results showed that the Dominant species was the Pohutukawa tree in almost very patch. The Pohutukawa tree was the biggest species

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in almost every patch. We also noticed that there were a lot of other common species that also grew near and under the Pohutukawa tree, see Species Summary Table. The species that grew around and under the Pohutukawa tree were smaller in size; this suggested that these species may have come after the growth of the Pohutukawa tree; refer to Early, Mid and Late Successional Species Table.

Discussion

When starting this experiment, the expectation for the experiment was that not a lot of species will be able to grow on Rangitoto after the volcanic disturbance and therefore the number of species will be low, but this was proven wrong with the results which were gathered. On the other hand the hypothesis of the number of species increases as the patch size increased was proved to be true with the data collected. There are many possible reasons for this, after the volcanic eruption disturbance on Rangitoto Island not a lot of species survived in the island, the ground was covered with lava rocks but this turned out to be a good for the Pohutukawa tree, as they only germinate in rocks. As said by Darden, D.(2004) “that Pohutukawa tree seeds will not grow if planted in your well prepared loamy garden soil, but must germinate in the crack of a rock”. As the Pohutukawa tree grew it formed a base for other plants to possibly grow underneath the Pohutukawa tree. This is because after the seed has germinated in the crack of a rock, it developed a “net” of roots for trapping debris and water and eventually for binding the rocks to hold its massive size and weight and in the jumble of scoria rocks on the volcanic island, Darden, D.(2004). The Pohutukawa tree grew many branches which it spread out to provide the beginnings of a humid soil with its leaf litter and shade for many smaller plants, and even some other species of trees which is why other species were able to grow on Rangitoto Island. The Pohutukawa tree is responsible for recreating forest ecosystems after volcanic cataclysms and therefore it has started the ecological succession on Rangitoto. In conclusion, the results collected for the experiment has proved the hypothesis made in the start. There is a relationship between species diversity and patch area and there is an ecological Succession on Rangitoto due to the Pohutukawa trees growth.

Reference:

Darden, D. (2004). Extraordinary Pohutukawa Trees. Adagio Journal. Retrieved September 18th, 2010, from http://adagiojournal.com/?p=484

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http://adagiojournal.com/

http://adagiojournal.com/?p=484

Data Sheets –

Team 1

Names Of Group Members-Bhavisha Singh, Maggie Sooalo, Logan

Name of your supervisor- Barack

Patch 1Patch Length (m):1.5m radius

Patch Area:7.07(m2)

Number of plant species:9

Species list patch 1Coprosma robustaAstelia banksiiGriselinia lucidaLeucopogon fasciculatusAsplenium oblongifoliumCyathodes juniperinaMyrsine australisOlearia furfuraceaCtenopteris heterophylla


Patch Area: 66.48(m2)


Species list patch 2Pohutukawa tree

Astelia banksiiLeucopogon fasciculatusGriselinia lucidaAsplenium flaccidumAsplenium oblongifoliumMicrosorum pustulatumTrichomanes reniformeMyrsine australis

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Patch Area:38.48(m2)

Number of plant species: 12

Species list patch 3Astelia banksiiAsplenium flaccidumPohutukawa treeMyrsine australisLeucopogon fasciculatusMicrosorum pustulatumTrichomanes reniformeBrachyglottis kirkiiAsplenium flabellifoliumAsplenium oblongifoliumCyathodes juniperinaGrammitis sp

Patch 4Patch Length (m):17.5m

Width (m):11.2m

Patch Area:196(m2)


Species list patch 4Pohutukawa treeAstelia banksiiLeucopogon fasciculatusGriselinia lucidaAsplenium flaccidumAsplenium oblongifoliumMicrosorum pustulatumTrichomanes reniformeMyrsine australisGrammitis sp G.givenii

G.poeppigianaCtenopteris heterophyllaCoprosma robustaCyathodes juniperinaOlearia furfuraceaHebe strictaPteridium esculentumPseudopanax arboreusAsplenium flabellifoliumGeniostoma rupestre

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Team 2


Patch Area: 8.0(m2)


Species list patch 1Astelia banksiiLeucopogon fasciculatusMetrosideros sp.Muehlenbeckia complexa

Patch 2Patch Length (m):6m radius




Astelia banksiiLeucopogon fasciculatusGriselinia lucidaAsplenium flaccidumMetrosideros sp.Microsorum pustulatumGeniostoma rupestreMyrsine australisAstelia solandriPomaderris phylicifoliaKnightia excelsaPterostylis sp.Olearia furfuracea

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Patch Area:16.6(m2)


Species list patch 3Astelia banksiiMyrsine australisAsplenium flabellifoliumAsplenium oblongifoliumGriselinia lucidaMetrosideros sp.Pomaderris phylicifoliaCyathodes juniperinaCoprosma robusta




Species list patch 4Astelia banksiiLeucopogon fasciculatusGriselinia lucidaAsplenium oblongifoliumMicrosorum pustulatumGrammitis spG.giveniiCoprosma robustaCyathodes juniperinaOlearia furfuraceaHebe strictaPteridium esculentumPseudopanax arboreusMetrosideros sp.Trichomanes reniformeThelymitra spPterostylis sp.Pomaderris phylicifolia

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Team 3


Patch Area:4.5(m2)


Species list patch 1Asplenium oblongifoliumMetrosideros sp.Leptospermum scoparium





Astelia banksiiGriselinia lucidaMicrosorum pustulatumMyrsine australisCoprosma robustaOlearia furfuraceaCoprosma lucidaMetrosideros sp.Leptospermum scopariumKnightia excelsa


Patch Area:19.6(m2)


Species list patch 3Astelia banksiiAsplenium flaccidumMyrsine australisMicrosorum pustulatumAsplenium oblongifoliumGrammitis spHebe strictaGriselinia lucidaOlearia furfuraceaMetrosideros sp.Leptospermum scoparium

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Patch 4Patch Length (m):12m radius



Species list patch 4Pohutukawa treeAstelia banksiiGriselinia lucidaAsplenium oblongifoliumMyrsine australisOlearia furfuraceaHebe strictaGrammitis spLeptospermum scopariumMetrosideros sp.Juvenile Microsorum pustulatum

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Tables and Figures

Species Summary Table Small Patch(Total Area: 6.52m2) (Total Species:13)

Medium Patch 1(Total Area:74.99m2)(Total Species:19)

Medium Patch 2(Total Area:24.89m2)(Total Species:19)

Large Patch(Total Area:276.62m2)(Total Species:25)

Coprosma robusta Pohutukawa tree Astelia banksii Pohutukawa treeAstelia banksii Astelia banksii Asplenium

flaccidumAstelia banksii

Griselinia lucida Leucopogon fasciculatus

Pohutukawa tree Leucopogon fasciculatus

Leucopogon fasciculatus

Griselinia lucida Myrsine australis Griselinia lucida

Asplenium oblongifolium

Asplenium flaccidum

Leucopogon fasciculatus

Asplenium flaccidum

Cyathodes juniperina


Microsorum pustulatum


Myrsine australis Microsorum pustulatum

Trichomanes reniforme

Microsorum pustulatum

Olearia furfuracea Trichomanes reniforme

Brachyglottis kirkii Trichomanes reniforme

Ctenopteris heterophylla

Myrsine australis Asplenium flabellifolium

Myrsine australis

Metrosideros sp. Metrosideros sp. Asplenium oblongifolium

Grammitis sp: -G.givenii, -G.poeppigiana

Muehlenbeckia complexa

Geniostoma rupestre

Cyathodes juniperina

Ctenopteris heterophylla

Leptospermum scoparium

Astelia solandri Grammitis sp Coprosma robusta

Pohutukawa tree Pomaderris phylicifolia

Griselinia lucida Cyathodes juniperina

Knightia excelsa Metrosideros sp. Olearia furfuraceaPterostylis sp. Pomaderris

phylicifoliaHebe stricta

Olearia furfuracea Coprosma robusta Pteridium esculentumCoprosma robusta Hebe stricta Pseudopanax

arboreusCoprosma lucida Olearia furfuracea Asplenium

flabellifoliumLeptospermum scoparium

Leptospermum scoparium

Geniostoma rupestre

Hebe strictaMetrosideros sp.Thelymitra spPterostylis sp.Pomaderris

phylicifoliaLeptospermum scoparium

This table shows all the species observed in all the teams of the group combined in the total area combined for each patch. Each patch is combined to its size and all the common and uncommon species in the same patch size of each team in the group to

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see if there is a relationship between patch size and species diversity. The table proves that there is a positive relationship between patch size and species diversity. We also wanted to see is there is a sequence of species in the patch area and the table proves that there are common species in each table, therefore there could be a sequence of species that could prove there is a primary succession occurring in Rangitoto.

Data Summary Sheet

Group patch area species richness

1 7.1m2 9

66.5m2 9

38.5m2 12

196m2 20

2 8.0m2 4

16.6m2 9

113.1m2 14

181.5m2 18

3 4.5m2 3

45.4m2 10

19.6m2 11

452.4m2 10

This table gives the patch area and the number of species in the patch of the whole group.

Early, Mid and Late Successional Species TableEarly successional

speciesMid successional

speciesLate successional

speciesPohutukawa Tree Olearia furfuracea Juvenile Microsorum

pustulatumLeucopogon fasciculatus Myrsine australis Knightia excelsaAstelia banksii Griselinia lucida Brachyglottis kirkiiAsplenium oblongifolium Cyathodes juniperina Leptospermum scopariumAsplenium flaccidum Coprosma robusta Pomaderris phylicifoliaGriselinia lucida Metrosideros sp Muehlenbeckia complexaGrammitis sp. Ctenopteris heterophylla Pseudopanax arboreus

Microsorum pustulatum Geniostoma rupestreAsplenium flabellifolium Hebe stricta

Thelymitra sp

Pterostylis sp.Astelia solandriPteridium esculentumTrichomanes reniforme

This table shows species that may have come early, mid or late after the eruption of the volcano. It shows the species growth after the volcanic disturbance.

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Figure 1

Species Diversity vs Vegetation Patch Area

y = 0.0156x + 9.254

R2 = 0.1719

0

5

10

15

20

0 50 100 150 200 250 300 350 400 450

Vegetation Patch Area

Nu

mb

er o

f S

pec

ies

Species Diversity

Linear (SpeciesDiversity)

This chart shows and proves that the prediction that there is a relationship between patch size and species diversity. The graph shows that the relationship between patch size and species diversity is a medium, linear, positive relationship. There is a data point which is located at the (452m2, 10), this data is very far from the other data set, if this data was to be taken out there probability will change dramatically, which will suggest that there is a strong relationship between the patch size and species diversity. But this chart puts in prospective that even though the patch area is large it does not necessary mean there always will be a large number of different species.

Figure 2

Species richness vs Patch area

0

5

10

15

20

25

Patch area

Nu

mb

er o

f S

pec

ies

7.1m2

66.5m2

38.5m2

196m2

This graph shows the number of species for each team in the group. The graph also proves that number of species diversity grows as patch size grows.

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