Ecological Succession In Grassland And Tropical Rainforest 1e3b2i

ECOLOGICAL SUCCESSION IN THE TROPICAL RAINFOREST AND TROPICAL GRASSLAND

Bernice P. Serquina Group 1 X-1L

April 19, 2016

1

A scientific paper submitted in partial fulfillment of the requirements in BIO 150: Principles of Ecology laboratory, 2nd Semester, 2015-2016

ABSTRACT In this scientific paper, evidences of ecological succession was investigated in the tropical rainforest and tropical grassland. The chosen sites of tropical forest study site and tropical grassland is the forest in the College of Forestry, University of the Philippines Los Baños, and the grassland in Putinglupa, Calamba City, respectively. The experiment showed that secondary growth or secondary succession can be observed in the tropical rainforest due to the presence of grass and small-statures species along the trail, as well as due to historical evidence. The rainforest is the climax community while the tropical grasslands consist of the pioneer community. Using the values obtained from the Shannon and Simpson’s Indices, it is also seen that the tropical rainforest has higher species diversity than the tropical grasslands.

INTRODUCTION

A population is a group of the same kind of organisms that live in the same place and in the same time. Populations that live together form communities. Communities on a global scale are called biomes (Boundless, 2016). Similarities in vegetation type, climate, geographic location and other features, classify the biological communities into biomes. The physical environment has a strong influence on organisms that thrive in it, hence organisms that experience the same environmental conditions often have similarly evolved characteristics. Differences in vegetation due to variations in climate and environment can be used to distinguish biomes (McGinley, 2014). The physical conditions heavily dictates the different species that can thrive in an environment to form a community. Species diversity is essential in comparing communities. It is a measure of diversity which is influenced by species richness, which is the number of species in a community, and the abundance of individuals per species (McGinley, 2014).

The Shannon and Simpson's indices are among the most widely used diversity indices. Both indices considers the contribution of each species to a community, the main difference is that the Shannon index estimates the 'uncertainty' in randomly selecting a species from a community, while the Simpson’s index takes into consideration the dominance of a species in the community (Cuevas, et al., 2012). Found near the equator and known by having the greatest diversity of species are the tropical rainforests (University of California Museum of Paleontology, 2013). The Philippines is naturally covered by tropical rainforests due to the climate in the country and its location near the equatorial region. The first stage of community development or succession can be seen in the appearance of tropical grasslands, which came in existence in the country due to events, either natural or caused by humans that led to the ruin of some areas of the forest. The last stage or the climax community, is the forest. The organisms that thrive in the grasslands greatly differ to those that thrive in the forest, as they are adapted to be able to survive the open area of the grasslands. These organisms are called pioneer species, where a community consisting of these species can take an extremely long period of time before reaching the climax stage (Cuevas, et al., 2012). In determining the species contribution to a community, density, ‘the number of individuals per unit area’, can be considered useful when it comes to forests, where individuals are easily distinguishable. As for grasslands, individuals of grass species are harder to distinguish, and so, cover, which is ‘the space subtended by the modules’, is employed, as it also signifies the ability of the species to obtain resources (Cuevas, et al., 2012).

The chosen sites of tropical forest study site and tropical grassland is the forest in the College of Forestry, University of the Philippines Los Baños, and the grassland in Putinglupa, Calamba City, respectively. This exercise has the following objectives; it aims to: 1. infer stages of ecological succession after the study of grassland and forest communities; and 2. describe the structures of tropical forest and tropical grassland communities through measures of species diversity and dominance indices.

MATERIALS AND METHODS

In the experiment, the tropical rainforest was investigated first. While approaching the main forest study site, vegetation on either side of the road was observed and recorded in Table 4C. 1, noting the presence of grasses, herbaceous vegetation, vines, shrubs and tree saplings. The approximate distance of the vegetation from the forest study site was also recorded. Upon reaching the forest, an area within was located where topography was relatively flat. A transect belt was laid out, measuring 10 x 20 m. All plant species found within the transect belt was identified and recorded. The number of individuals of each species present in the transect belt was also counted, excluding seedlings of tree species that were shorter than 30 cm. The population and relative densities of the species per area observed using the following formula were also obtained and recorded in Table 4C.2:

Population density=

number of individuals of a species∈thebelt transect area of thetransect belt

Relative density ( pi ) =

number of individuals of a species total number of individuals for all species

In the second part of the experiment, a tropical grassland was investigated. While approaching the grassland study site, the vegetation on either side of the trail was observed, noting the presence of trees or shrubs. The names of some of the species were recorded in Table 4C.1. Indicators of agricultural activities in the area close to the study site were also observed and recorded. Upon reaching the grassland study site, an area was selected were the vegetation was least disturbed, taking note of its topography. A 30-m transect line was laid out in the area. All plant species intercepted by the transect line was identified and recorded in Table 4C.3. The horizontal cover of each species encountered along the transect line was also determined using the Line Intercept Method. The following parameters were calculated for each species: cover =

Total intercept length for a species x 100 Total transect length

Relative Cover ( p i )=

Total intercept length for a species Total intercept length for all species

The indices of diversity of organisms in the tropical forest and the tropical grassland were also computed, using the formulas found below: Index Shannon Index of Diversity (H’)

Formula s

H ' =−∑ p i x p i t =1

Descriptions S = species richness = number of species

Shannon Index of Evenness (J) Simpson Index of Dominance (D) Simpson Index of Diversity

J=

H' lnS s

D=∑ pi2 t =1

Pi = proportion of total sample belonging to the ith species (using relative density or relative cover for TRF or grassland, respectively)

SID=1−D

(SID) Simpson Index of Equitability

E=

SID S

(E)

The results of the computation were also obtained and recorded in Table 4C.4. RESULTS AND DISCUSSIONS

In Table 4C.1 is the list of species present along the trail to both tropical forest and tropical grassland study sites. The forest is the climax community and the grassland is the pioneer community. Since in the road to the forest study site, grass and short-statured species, basically of the pioneer community, they could be indicators that the grassland and forest in the site are stages of succession, where in before it became a forest or reached climax community, the site used to be a grassland, and perhaps through time, through ecological succession, became a forest. It is also possible that it is still undergoing succession due to the presence of seedlings and smaller trees. This is further ed by the appearance of tree and shrub species along the trail to the grassland study site, which is also listed in Table 4C.1. Most of the species found along the trail to the grassland are shrub species and more short-statured species rather than tall, large, established trees. This could also indicate ecological succession,

since the species found along the trail to the grassland may indicate a later stage after the pioneer stage, but definitely before the climax stage, as seen by the lesser number of individuals of larger trees. Indicators of agricultural activities in the grassland include the presence of chickens and cows. 4C. 1. Species present along the trail to tropical forest and tropical grassland study sites. Grass and short-statured species found along the road/trail to forest study site Triplaris Dieffenbachia Celtis Tree and shrub species found along the road/trail to grassland study site Few grass species Shrubs Fishtail palm Kakwate Saccharum Sapinit Imperata Vines Ferns Ipomoea Makahiya Ageratum Indicators of agricultural activities in the grassland study site Presence of chicken and cows

In tropical areas such as the Philippines, tropical forests are usually extremely abundant. Especially in the Philippines, where old Spanish records of history described the forest of the Philippines to be bordering nearly that of the shore. Presence of grasslands in the present may indicate the occurrence of phenomenon which may have disturbed and greatly reduced the vegetative cover of the forest. These phenomenon may be due to agricultural activities or natural calamities such as forest fires, storms and landslides. The grasslands serve as the pioneer community. Pioneer species grow in the recently disturbed area and undergo through the seral stages, until after a period of time, with the right conditions, become a climax community, which is the forest. That is usually the process of succession in tropical forests. However, many factors affect this process, such as a change in environmental conditions, or the presence of another

disturbance. It can happen that when a community undergoing succession is repeatedly disturbed, it may not reach climax community anymore, or if it will, it will take a time even longer than normal. The forest study site is most likely a secondary growth forest. A secondary growth forest is once a primary growth forest that has experienced a disturbance, leading to the loss of its community, but is regained through ecological succession after a period of time. Evidences include the presence of young saplings inside the forest as well as smaller trees, as well as the presence of grass and small shrubs, along the area. Since the Philippines used to be dominated by forest vegetation, the presence of grasses and small shrubs indicate that it had been through some form of disturbance. The presence of the young saplings and smaller trees may indicate the transition from the grasses to the larger trees, which is the climax community. Although lacking tangible evidence, it is also said that the forest site had historically experienced a forest fire, leading to the loss of the primary growth forest. A primary growth forest is a forest that originally grew in an area that has not been occupied by a community before. Its characteristics include the presence of trees with extremely large trunks relative to trees that grow in a secondary growth forest, very large and long roots that penetrate deep into the soil. Another characteristic is the increased presence of insects, mosquitos, organisms with microhabitats, which are often smaller in number in secondary growth forests due to have been driven out of their habitat before. Lastly, another important characteristic is the presence of rare birds and other rare organisms that only thrive in undisturbed forests and cannot be found in secondary growth forests. From the values taken from Table 4C.2 and 4C.3, the values of the Shannon index of tropical grassland and tropical rainforest, as seen in Table 4C.4, indicates that the tropical

rainforest has higher species diversity, having higher values of Shannon Index of Diversity and Shannon Index of Evenness. The forest also has a higher value of Simpson Index of Diversity as well as a lower Simpson Index of Dominance. This may be because the rainforest has environmental conditions that is more conducive to the growth and propagation of organisms, rather than in the grassland, which tends to become more selective as it consists of relatively harsher environmental conditions, where fewer organisms can survive, such as being exposed to excessive sunlight, and poor soil quality.

4C. 2. Species composition in a tropical rainforest. NAME OF SPECIES

NUMBER OF INDIVIDUAL

POPULATI ON DENSITY

In (Pi)

Pi(lnPi )

(Pi)^2

0.020

RELATIV E DENSITY (Pi) 0.017

Bauhina

3

-4.10

-0.068

1

0.0067

0.0055

-5.20

-0.029

Caryota

5

0.033

0.028

-3.59

-0.099

Arengga

3

0.020

0.017

-4.10

-0.068

Triplaris Celtis Guazuma

81 21 4

0.54 0.14 0.027

0.45 0.116 0.022

-0.80 -2.15 -3.81

-0.36 -0.25 -0.084

Shorea

1

0.0067

0.0055

-5.20

-0.029

Dracaena

1

0.0067

0.0055

-5.20

-0.029

Ixora

1

0.0067

0.0055

-5.20

-0.029

Goniothalao nus Parashorea

1

0.0067

0.0055

-5.20

-0.029

3

0.020

0.017

-4.10

-0.068

Memecylon

1

0.0067

0.0055

-5.20

-0.029

0.0002 7 0.0000 31 0.0007 6 0.0002 7 0.20 0.013 0.0004 9 0.0000 31 0.0000 31 0.0000 31 0.0000 31 0.0002 7 0.0000 31

Livistonia

Unknown 1

1

0.0067

0.0055

-5.20

-0.029

Unknown 2

2

0.013

0.011

-4.51

-0.050

Unknown 3

2

0.013

0.011

-4.51

-0.050

Unknown 4

2

0.013

0.011

-4.51

-0.050

Pterocarpus

3

0.020

0.017

-4.10

-0.068

Bagong Aso

1

0.0067

0.0055

-5.20

-0.029

Drypetes

2

0.013

0.011

-4.51

-0.050

Glospiros

1

0.0067

0.0055

-5.20

-0.029

Coffea

5

0.033

0.028

-3.59

-0.099

Swietenia Antidesma

9 1

0.060 0.0067

0.050 0.0055

-3.00 -5.20

-0.15 -0.029

Dieffenbachi a Platimytra

1

0.0067

0.0055

-5.20

-0.029

1

0.0067

0.0055

-5.20

-0.029

Pentandous

1

0.0067

0.0055

-5.20

-0.029

Kong

2

0.013

0.011

-4.51

-0.050

Cordyline

3

0.020

0.017

-4.10

-0.068

Synometra

2

0.013

0.011

-4.51

-0.050

Chysochetro m Uvana

1

0.0067

0.0055

-5.20

-0.029

1

0.0067

0.0055

-5.20

-0.029

Artocarpus

4

0.027

0.022

-3.81

-0.084

Compandra

1

0.007

0.0055

-5.20

-0.029

Amorphopha lous Specimen 98

2

0.013

0.011

-4.51

-0.050

3

0.020

0.017

-4.10

-0.068

Specimen 100

2

0.013

0.011

-4.51

-0.050

0.0000 31 0.0001 2 0.0001 2 0.0001 2 0.0002 7 0.0000 31 0.0001 2 0.0000 31 0.0007 6 0.0025 0.0000 31 0.0000 31 0.0000 31 0.0000 31 0.0001 2 0.0002 7 0.0001 2 0.0000 31 0.0000 31 0.0004 9 0.0000 31 0.0001 2 0.0002 7 0.0001 2

Specimen 106 Specimen 95

1

0.0067

0.0055

-5.20

-0.029

1

0.0067

0.0055

-5.20

-0.029

Total

181

-2.449

0.0000 31 0.0000 31 0.2218 8

4C. 3. Species composition in a tropical grassland. NAME OF SPECIES

INTERCEPT ED LENGTH (cm)

% COVER

RELATIVE COVER (Pi)

In (Pi)

Pi(lnPi )

(Pi)^2

Elephantopus Ipomoea Saccharum Desmodium Calopogoniu m Synedrella

140.6 21.2 88.6 37.1 187.4

4.69 0.71 2.95 1.24 6.25

0.059 0.0089 0.037 0.016 0.078

-2.83 -4.72 -3.30 -4.14 -2.55

-0.17 -0.042 -0.12 -0.066 -0.2

0.0035 0.000079 0.0014 0.00026 0.0061

6.4

2.13

0.0027

-5.91

-0.016

Crotalatia Mimosa Imperata Psidium Unknown 1

31.5 82.8 1783 9 1.5

1.05 2.75 59.43 0.3 0.05

0.013 0.035 0.75 0.0038 0.00063

-4.34 -3.35 -0.29 -5.57 -7.37

Unknown 2

3.9

0.13

0.0016

-6.44

-0.056 -0.12 -0.22 -0.021 0.004 6 -0.01

0.000007 3 0.00017 0.0012 0.56 0.000014 0.000000 40

TOTAL

2393

80.99

0.000002 6 0.5752

4C. 4. Diversity and Similarity Indices in Tropical Grassland and Tropical Rainforest. COMMUNITY TYPE

S

H'

J

D

SID

E

TROPICAL FOREST TROPICAL GRASSLAND

39

2.45

0.67

0.22

0.78

0.020

12

1.046

0.42

0.57

0.43

0.036

Species that is most common in the grassland, as seen in Table 4C.3, is Imperata. Its ability to dominate the community may be due to a few of its morphological characteristics, such as very lightweight seeds that are easily dispersed by the wind, enhancing the probability of propagation of its kind. It may also be due to its wide range of tolerance, as it is able to withstand harsh environmental conditions such as more acidic soil, and exposure to excessive sunlight. Species that are rare in the grassland is Unknown species 1 and 2, and Synedrella. They have the smallest values of intercepted length, % cover and relative cover. Species that are common in the forest are Triplaris and Celtis. Their dominance in the community may be due to their ability to propagate more effectively. Some species of Triplaris have bright red fruits, which may be able to catch the attention of more seed dispersers. Triplaris is also known for having a hollow terminal branches where ants reside. These ants become aggressive and fend off any attack from any organism on the tree. As for Celtis, it produces a fruit with sugar content, making it sweet. This may be able to attract seed dispersers effectively as well.

SUMMARY AND CONCLUSION Ecological succession is the process of the evolution of the structure of a community over time (Thompson, 2016). There are two types of succession, primary and secondary. In tropical rainforests, primary growth is when the forest grew in an area that has not been occupied by a community before, while secondary growth has already experienced disturbance and loss of community, but through time, has undergone regrowth of the forest.

The forest site visited was the forest in the College of Forestry, University of the Philippines Los Baños, while the grassland site was the grassland in Putinglupa, Calamba City. The forest site can be inferred to have experienced or is currently experiencing secondary ecological succession, due to the presence of grass and small-statured species along the trail approaching the forest. This is further backed up by historical evidence, wherein Spanish historians noted the dominance of the forest cover in the country, therefore the presence of grasslands indicate the event of a disturbance. The grass species in the grasslands are therefore consists of the pioneer community while the forest consists of the climax community in the ecological succession. Using the values obtained from the Shannon and Simpson’s Indices, it can be seen that there is more or higher species diversity in the tropical rainforest than in the grasslands. This may be due to the difference in environmental conditions, where in the rainforest tends to be more conducive to propagation and growth of organisms, while the grassland tends to be more selective due to harsh environmental conditions.

LITERATURE CITED Boundless (2016). Boundless Biology. Retrieved from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/ecology-andthe-biosphere-44/terrestrial-biomes-246/what-constitutes-a-biome-910-13111 Cuevas, V.C., Cervancia, C.R., Zafaralla, T.M., Lit, .Jr., I.L., Barrion-Dupo, A.L.A., Lambio, I.A.F( 2012) Exploring Ecology. Environmental Biology Division, Institute of Biological Sciences, CAS, UPLB McGinley, M. (2014). Biome. Retrieved from http://www.eoearth.org/view/article/150661 McGinley, M. (2014). Species diversity. Retrieved from http://www.eoearth.org/view/article/156211.

Paleontology, U. (2013). Forest biome. Retrieved from http://www.eoearth.org/view/article/152816 Thompson, J.N. (2016). Ecological Succession. Encyclopedia Britannica. Retrieved on April 18, 2016 from http://www.britannica.com/science/ecological-succession