ABSTRACT

A tropical forest in Mount Makiling, UP Los Banos and tropical grassland in Putinglupa, Calamba were observed. Species in both biomes were observed and recorded. Species found in tropical rainforest is relatively higher than those found in tropical grassland. There were 27 species found and identified in tropical rainforest while in tropical grassland, there were only 16 species. Logically, it can be stated that the rainforest has higher diversity and evenness of species which is equal to 2.593 and 0.787, respectively. However, when it comes to dominance, the grassland has greater value which is equal to 0.189 thus; its species diversity is low. The dominant species in the tropical rainforest is Palosanto while Imperata cylindrica dominated the grassland. There is no similar species that can be found in both biomes which states that grassland would not be dominated by the species found in the forest. As studied, in tropical regions, there are repetitive disturbances that inhibit succession. Thus, ecological succession is not likely to occur in the type of grassland observed.

INTRODUCTION

To most ecologists, the term community means an assemblage of species that occur together in the same place. Ecologists also agree that the species living together within a community can interact strongly as consumers and resources or as competitors. Some ecologists have asserted that the community is a unit of ecological organization having recognizable boundaries and whose structure and functioning are regulated by interactions among species. Others have regarded the community as a loose assemblage of those species that can tolerate the conditions of a particular place or habitat, but which has no distinct boundary where one type of community meets another (Ricklefs, 2008).

Biomes are major communities of organisms that have a characteristic appearance and that are distributed over a wide land area defined largely by regional variations in climate. There are many ways to classify biomes, and

different ecologists may assign the same community to different biomes (Johnson and Raven, 2002).

The tropical rainforest is s hot and moist biome found near the Earth’s equator. 60 to 10 inches of precipitation which is fairly evenly distributed throughout the year is received by tropical forests. Tropical rainforests become a suitable environment for many plants and animals through the combination of constant warmth and abundant moisture present in it. It also contains the greatest biodiversity in the world having over 15 million species of plants and animals.

Grassland biomes, on the other hand, are large open regions on Earth that have a lot of grass hence, the name grassland. Bushes do not grow much in grassland and the trees are commonly found near the rivers. Grasslands make up almost ¼ of the Earth’s land surface. It rains between 10 to 30 inches per year in this region. If there is more rain, trees will grow and the land would become a forest but when there is lee rain, the land would become a desert thus; grasslands are often located between deserts and forests.

Communities exist in a state of continuous flux. Organisms die and others are born to take their places; energy and nutrients pass through the community. Yet the appearance and composition of most communities do not change appreciably over time. But when a habitat is disturbed the community slowly rebuilds. Pioneering species adapted to disturbed habitats are successively replaced by other species as the community attains its former structure and composition. The sequence of changes initiated by disturbance is called succession, and the ultimate association of species achieved is called a climax community (Ricklefs, 2008).

This study was designed to determine if ecological succession is likely to occur in grassland biome. It also aims to infer stages of ecological succession after the study of grassland and forest communities and describe the structures of tropical grassland communities through measures of species diversity and dominance indeces. This study was conducted at Putinglupa, Calamba and Mount Makiling, UP Los Baños on July and August, 2007.

REVIEW OF RELATED LITERATURE

There are studies focusing on species diversity. Samuel M. Scheiner, Stephen B. Cox, Michael Willig, Gary G. Mittelbach, Craig Osenberg and Michael Kaspari conducted a study regarding patterns of species diversity as a scale. It also determines how, for a given set of species, the species-area curve varies with respect to latitude or productivity. Critical is whether the relationship is scale-invariant (i.e. the species–area curves for different levels of the third variable are parallel), rank-invariant (i.e. the curves are non-parallel, but non-crossing within the scales of interest) or neither, in which case the qualitative relationship is scale-dependent. This recognition is critical for the development and testing of theories explaining patterns of species richness because different theories have mechanistic bases at different scales of action. Scale includes four attributes: sample-unit, grain, focus and extent. Focus is newly defined here. Distinguishing among these attributes is a key step in identifying the probable scale(s) at which ecological processes determine patterns (Cox, et al. 2000)

RESULTS AND DISCUSSION

Trails in biomes, tropical grassland and rainforest, were made in order to determine the species present. The data gathered were organized in Table 4C.1, 4C.2 and 4C.3.

(Insert table 4C.1 to 4C.3 here) Primary forest refers to untouched, pristine forest that exists in its original condition. This forest has been relatively unaffected by human activities. Primary rainforest is often characterized by a full ceiling canopy and usually several layers of understory. The ground floor is generally clear of heavy vegetation because the full canopy allows very little light, necessary for plant growth, to penetrate. Occasionally, when a canopy tree falls, a temporary "light gap" is opened in the canopy, allowing growth of floor and understory species. Primary forest is the most biologically diverse type of forest.

Secondary forest is rainforest that has been disturbed in some way, naturally or

unnaturally. Secondary forest can be created in a number of ways, from degraded forest recovering from selective logging, to areas cleared by slash-and-burn agriculture that have been reclaimed by forest. Generally, secondary forest is characterized (depending on its level of degradation) by a less developed canopy structure, smaller trees, and less diversity. Due to the lack of a full canopy, more light will reach the floor, supporting vigorous ground vegetation. "Jungle" is the term often applied to secondary forest with dense ground growth, but it is also applied to some tropical moist forests where seasonal variations permit thick ground growth.

Based on the information gathered, a secondary forest community will not replace the grassland community because no type of species that covers up the forest was found in the forest and in most tropical grasslands there are many repeated disturbances like fire or agricultural practices that inhibit ecological succession.

The community with higher diversity, evenness, and degree of dominance were determined (see Table 4C.4). Results showed that tropical rainforest has higher diversity (2.593) and evenness (0.787) as compared to the tropical grassland (1.996 and 0.720, respectively). One property of diversity is that it ensures an “even” community to have a greater index of diversity than one, in which the community is dominated by one or few of them n which case its diversity in the intuitive sense would be less (Pielou, 1975). However, when it comes to dominance, the tropical grassland has higher value (0.189) than that of rainforest (0.131). The degree of dominance was computed by using the Simpson Index of dominance. It takes a different approach- the number of times we would have to take pairs of individuals at random to find a pair of the same species. Dominants in a community may be the most numerous, possess the highest biomass, pre-empt the most space, make the largest contribution to energy flow or mineral cycling, or by some other means, control or influence the rest of the community (Smith and Smith, 2006). A community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance.

The species, Imperata cylindrica and Mimosa, are found to be common in grassland. Grass is a very successful plant because it can survive the harshest conditions. Unlike most plants, grasses grow from the base, not the top. Creeping stems above the ground are called stolons, and those below the ground are called rhizomes. As these creeping stems spread out, shoots grow up and produce leaves. The deep, spreading root systems make sure that even in drought; the plants are able to get water. Long narrow leaves like grass do not lose as much water in the heat as big leaves do. Grass can be cut quite close to the ground, and new leaves (blades of grass) sprout from the base of the plant. This means that grasses can be eaten and walked on by animals and are not killed.

Trees and shrubs have been observed to be rare in tropical grasslands. The variable rainfall is not enough to support large trees but is sufficient for many species of grass (Asis and Velasquez, 1993).

Trees, especially Palosanto, and shrubs turned out to be common in forest. In sharp contrast, the climate of the tropical rainforest is hot and wet. With over 80 inches of rain per year, as opposed to the desert's 10 inches or less, plants have adaptations that enable them to shed water efficiently. The leaves of many rainforest plants have drip tips for this purpose. Buttress and stilt roots are thought to provide extra support for trees growing in spongy, wet soils.

Tropical rainforest plants also have adaptations to take in what little sunlight is available on the dark forest floor. Large leaves are common; they increase the amount of sunlight a plant can capture. Other plants, like orchids, bromeliads and ferns, grow as epiphytes high up in the canopy where there is more sunlight.

SUMMARY AND CONCLUSION

To determine if ecological succession is likely to occur in grassland, an experiment

was conducted using two types of biomes: the tropical grassland in Putinglupa,

Calamba and the tropical rainforest in Mount Makiling, UP Los Baños. A belt-

transect (10m x 30m) and a line transect (30m) were laid out on the tropical

rainforest and tropical grassland, respectively. The species found in these areas

were identified and recorded in tables. There are 27 species in the belt-transect of

rainforest while 16 species present in the transect line of the grassland. Using the

same data, the indices of diversity were computed and results showed that the

rainforest has: H’= 2.593, J= 0.787, D= 0.131, SID= 0.869, E= 0.032 while the

grassland has: H’= 1.996, J= 0.720, D= 0.189, SID= 0.811, E= 0.051. Based on the

values computed, the rainforest has the higher diversity of species than the

grassland. The Palosanto and shrubs dominates the forest and the Imperata

cylindrica and Mimosa dominates the grassland. The species found in the two

biomes are completely different. These differences may be due to the distance of

the biomes observed. Ecological succession will most likely not occur in grassland

because no species in the rainforest will dominate or occur on it. If the study

would be changed and choose biomes near to each other, the chances of having

same species will increase. As studied, in tropical regions, the grasslands would

not exhibit ecological succession because it would be inhibited by repetitive

disturbances like agricultural practices or fire. Thus, ecological succession would

not occur in grassland.

LITERATURE CITED

Ricklefs, R.E. 2008. The Economy of Nature. 6th ed. New York: W. H. Freeman and Company

Asis, C.V. and Velasquez, C.C. 1993. Modern Biology. Revised Ed. Quezon City: Atlas Publishing Company, Inc.

Johnson, G.B. and Raven, P.H. 2002. Biology. 6th ed. New York: McGraw-Hill Companies, Inc.

Pielou, E.C. 1975. Ecological Diversity. Canada: John Wiley and Sons, Inc. y

Scheiner, M.S., et al. 2000. Evolutionary Ecology Research. 2000. Cambridge: Cambridge UniversityPress.

Smith, R.L. and T.M. Smith. 2006. Elements of Ecology. 6th Ed. New York: Addison Wesley Longman, Inc.

Ehrlich, P. R. and J.Roughgarden. 1987. The Science of Ecology. New York, USA:Macmillan Inc.

Janzen, D. H.1988. Management of Habitat Fragments in a Tropical Dry Forest:Growth. Annals of the Missouri Botanical Garden. USA: Missouri Botanical GardenPress

Bruner, W.E. and Weaver, J.E. 1945. Ecological Monographs: Ecological Society of America. Lincoln, Nebraska, United States: Agronomy and Horticulture Faculty. Accessed February 19 through: http://www.digitalcommons.unl.edu/agronomyfacpub/474/

Begon, M., J.L. Harper and C.R. Townsend. 1998. Ecology: Individuals, Populations and Communities. 2nd Ed. Blackwell Publ., U.S.A.