rain forests: floristics - uenf · however, forests at higher elevations can be significantly...

RAIN FORESTS: FLORISTICS

F. Z. Saiter Instituto Estadual de Meio Ambiente e Recursos Hídricos, Espírito Santo, Brazil

T. Wendt Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

D. M. Villela Universidade Estadual do Norte Fluminense, Rio de Janeiro, Brazil

M. T. Nascimento Universidade Estadual do Norte Fluminense, Rio de Janeiro, Brazil

Keywords: Tropical forests, floristic composition, biodiversity, monodominance, nutrient cycling

Contents

1. Introduction 2. Global Distribution and Main Features of Tropical Rain Forests 3. Floristic Patterns 4. Biodiversity 5. Tropical Rain Forests are Dynamic 6. Nutrient Cycling 7. Conclusion and Outlook Related Chapters Glossary Bibliography Biographical Sketches

Summary

The tropical rain forest is well-known for its megadiversity and some important ecological services, especially on climate regulation. This forest type occurs in all four major tropical zones (America, Africa, Indo-Malaya and Australia) and covers about seven percent of the Earth’s forest area. Floristic composition varies largely within and among the main phytogeographic regions. However, some distinctive characteristics can be emphasized on family distribution such as the dominance of Dipterocarpaceae in western Malaysia and species richness of Lecythidaceae in America. In general, tropical forests show higher species richness when disturbance is at an intermediate intensity or frequency. On the other hand, monodominant forests can occur when small but frequent disturbances take place or after long periods without any relevant disturbance. Early studies associated low species diversity with low soil nutrient availability, but there is still controversy in this respect. However, chemical fertility and soil moisture are among the factors which have been considered important determinants of species richness in tropical forests. Although tropical forest provides important services to natural systems and humankind, it still suffers severe

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deforestation in most tropical countries.

1. Introduction

Forests cover ~ 42 million km2 of the Earth’s land surface, which only about 7 percent are within tropical regions. However, tropical forests, and especially the tropical rain forests, are extremely important for regulation of global weather and, therefore, of human existence as highlighted by the United Nations Framework Convention on Climate Change and the Convention on Biological Diversity. Estimates are that more than 50% of all the Earth species live in tropical rain forests. Thus, they are a natural reservoir of genetic diversity that offers a myriad of useful forest products. Despite their obvious importance, every year thousands of hectares are destroyed worldwide. Most of the world’s remaining tropical rain forests are located in developing nations and financial return on timber and farming is crucial for human survival in many such nations.

Tropical rain forests across the world are very diverse, but share several basic characteristics. They are limited between the Tropic of Capricorn and Tropic of Cancer and, because of the high solar energy in this region, tropical rain forests are usually warm year round with temperatures about 22-34o C. However, forests at higher elevations can be significantly cooler. Temperature may fluctuate slightly during the year, which in equatorial forests is almost imperceptible. As tropical rain forests lie in the intertropical convergence zone, they are subjected to heavy rainfalls: at least 2,000 mm of rain, and in some areas more than 10,290 mm per year. In equatorial regions, some forests do not show precise "wet" or "dry" seasons, although many forests do have seasonal rains. Even dry periods are usually not long enough to completely dry out leaf litter. The usually constant cloud cover is enough to keep the air moist and prevent plant desiccation.

A primary or mature tropical forest often has several layers and three tree strata. The top layer or upper storey (overstory) is formed by emergent trees that consist of scattered tall trees that have most of their foliage fully above a closed canopy layer formed by the crowns of other trees. The middle storey, or canopy, is the stratum where most of the flowering and fruiting of the trees take place. A third layer (lower storey or understory) is formed by smaller trees whose crowns do not meet. Immediately underneath this stratum one finds the shrubby layer, formed by woody and herbaceous shrubs, and the ground layer (or forest floor), which is the darkest layer where scattered herbaceous plants and seedlings of tree species are found.

2. Global Distribution and Main Features of Tropical Rain Forests

The global distribution of tropical rain forests can be broken up into four biogeographic realms: the Neotropics (northern South America and Central America), the Afrotropics (equatorial Africa), the Indo-Malayan (parts of the Indian subcontinent and Southeast Asia, and tropical islands of the Pacific Ocean), and the Australasian (eastern Indonesia, New Guinea, northern and eastern Australia). Formerly the Australasian rain forest has been considered an extension of the Indo-Malayan, and for the purpose of comparison done in this present chapter we will treat both together.



2.1. The Neotropical Rain Forest

There are three major blocks of rain forest in Neotropical realms: the largest one is located in the Amazon River Basin in South America, a second one along the Brazilian coastline, the so-called Atlantic Forest, and a third block covers the Andes on the Pacific coast extending through to Central America. The Neotropical rain forest is consistently more species rich than the African, Indo-Malayan and Australian rain forest.

The rain forest in the Amazon Basin is known as the Amazon Forest. It occupies seven million square kilometers which represent over half of the Earth’s remaining rain forests. As the largest area of tropical rain forest, the Amazon Forest has unparalleled biodiversity. It is located within nine nations: Brazil (with major total area, 60%), Colombia, Peru, Venezuela, Ecuador, Bolivia, Guyana, Suriname, and French Guiana. Due to its vast extent area, several different vegetation types might be distinguished, which are often related to the flooding pulses of the main rivers at the Amazon basin. The Amazon River is the largest river in terms of discharge and the second longest river in the world after the Nile. Unfortunately, currently the Amazon Forest suffers the highest rate of deforestation associated with land use change especially for agriculture expansion (pasture and soybean), commercial logging and settlements. Deforestation is likely to be the main factor implying in biodiversity loss. There are also concerns about the releases of the carbon contained within the vegetation, which contributes to global warming.

The Amazon Forest has an extensive border with the cerrado (savanna woodland) and caatinga (dry deciduous forest) vegetation types in Brazil, which separates it from the Atlantic Forest. The Atlantic Forest originally extends along much of the Brazilian coast, forming a narrow strip between the ocean and the Brazilian drylands (cerrado, caatinga). While the Amazon Forest lies at more or less the same latitude and altitude, the Atlantic Forest spreads dramatically from the coast up into the mountains, and throughout several latitudinal zones, which confers great variation in temperature and precipitation rates. Thus, under the "Atlantic Forest" label many forest types can be found (e.g. evergreen forest, semi-deciduous forest, montane forest), The mangrove forests found in estuaries, bays and lagoons, and the xeromorphic coastal sandy plain vegetation, locally called restingas, are ecosystems associated to the Atlantic Forest. However, less than 10 percent of the Atlantic Forest remains intact.

The third block of tropical rain forest is found in western Andes, in very humid regions of Ecuador and Colombia, until the latitudinal limit of 19º North, in Vera Cruz, south of Mexico. Large areas of deforestation are found in the lower foothills of the Andes, especially in Peruvian and Ecuadorian lands. However, from Panama northwards these humid forests present discontinuities due to the existence of seasonal forests at the Pacific coast. Central America and Caribbean islands suffered the highest percentage of loss of forest of any tropical region over the last century, with the forest remnants being highly fragmented and persisting only in areas which are inaccessible or are legally protected as conservation units (parks and reserves).

2.2. The African Rain Forest

In the African continent there are two important tropical rain forests: the



Congo Rain forest and the Madagascar Rain forest. At Central Africa, more specifically at the Congo river basin, is located the Congo Rain forest. It is the second-largest dense tropical rain forest, surpassed only by the Amazon Forest, comprising ca. 2 million km2 that represents 70% of the African forest cover. The Congo River is the second largest in volume, and its river basin expands over six nations: Cameroon, Central African Republic, Republic of Congo, Democratic Republic of Congo, Equatorial Guinea and Gabon.

Because of its large size, Congo Rain forest serves as a vast carbon sink of global importance. The forest also regulates regional and local weather patterns, and ensures the cycling of water critical for a large area of Africa. It provides a critically important resource which supports livelihood and well-being of tens of millions of people both in Africa and beyond. This forest type is still well-preserved, accounting for less than 6% of the total loss of humid forest cover in the world. However, deforestation is a severe problem in parts of the continent.

Another important rain forest is located in the Madagascar that lies off the coast of southeastern Africa. It has long been famous for its unique and diverse species of wildlife, especially lemurs, which are small primates found nowhere else on the planet. Madagascar is home to some of the richest moist forests on Earth. Well over half of Madagascar's species are found in these forests which lie on the east coast of the island. However, eastern forests of Madagascar have been threatened by deforestation owing to slash-and-burn agriculture, logging and mining.

2.3. The Indo-Malayan and Australian Rain Forest

The Asian region holds 60% of the world’s population, and centuries of tremendous population pressure has significantly reduced forest surface. Actually, major threats to Asian Rain forests are the paper industry, intensive exploitation for timber and expansion of palm oil plantations.

The scattered fragments of tropical rain forest in Asia are located in the Indo-Malayan Peninsula. The Indo-Malayan Peninsula is the world’s largest archipelago located between mainland Southeastern Asia (Indochina) and Australia, lying between the Indian and Pacific Oceans. It comprises around 20,000 islands, with about 6,000 of those inhabited. The biggest islands are New Guinea, Borneo and Sumatra. Some of the Malay islands are administratively shared by more than one nation. The Republic of Indonesia comprises the majority of those islands (17,508).

Southeast Asia’s tropical rain forests are some of the oldest on Earth, and some present-day forests may have existed over 100 million years ago. Geologically, the archipelago (chain or cluster of islands) is one of the most active volcanic regions in the world. Tectonic uplifts in the region have also produced some impressive mountains, as the Mount Kinabalu (4,101 m) in northern Borneo. During the ice ages, when sea level lowered, some islands were connected to the Asian mainland. Therefore, today these islands have in common with the continent a great quantity of species of flora and fauna. Geographers believe that New Guinea Island may once have been part of the Australian continent, although New Guinea's flora has more affinities with Asia, and its fauna with Australia. Today, Australia has small areas of tropical rain forest in the extreme northeastern part of the continent near the coast.



3. Floristic Patterns

Regarding the species composition of the tropical flora, three patterns are recognized for the families of angiosperms:

� Large families generally have pantropical distribution. � Few families are entirely restricted to any of the three major blocks of

tropical rain forest. � Families that are entirely restricted to any of the three blocks have few

genera and species.

These patterns appear to be related to major biogeographic events during Earth’s geological history. Families of Angiosperms that could have been differentiated in the tropics - after the separation of continental masses corresponding to South America, Africa, India and Australia, about 100 million years ago - generally have few genera and species, probably because there was not enough time for greater diversification. Such families are also restricted to certain realms due to geographical barriers that prevent dispersion. Examples of small families that have exclusivity for certain flora are Cyrillaceae (endemic to the Americas), Sarcolaenaceae (endemic to Madagascar) and Peridiscaceae (endemic to Amazon Basin). Vochysiaceae is also a small family represented by only 6 genera and predominantly distributed in the Americas, with only one African species. However, there are large families, such as Bromeliaceae (Figure 1), composed by 56 genera and about 3,000 species, which is exclusively American, except for one species Pitcairnia feliciana (A. Chev.) Harms & Mildbr. that occurs in the Gulf of Guinea, West Africa.

Figure 1. Bromeliaceae are generally herbaceous plants, with leaves often lanceolate, and spirally arranged, forming a water reservoir tank among leaf

sheaths. The Atlantic rainforest in Brazilian southeast is one of the main centers of diversity and shows a high degree of endemism. The family has a

remarkable importance in the vegetation physiognomy, contributing to structural complexity of the environment which is directly reflected on

richness and diversity of associate fauna and flora.

Other families went through some evolutionary stability in the continent, suffering only diversification into the lower taxonomic categories. Currently, some of them may be considered as large families because they have many genera and species, which may be a unique feature of the taxon, or the result of the diversification that followed the continental drift. Some of the largest families of angiosperms more common in tropical forests are listed in Table 1. Among these, Araceae, Annonaceae, Euphorbiaceae, Moraceae, Myrtaceae and Rubiaceae are examples of families well represented throughout the tropical region. Other families, even with pantropical distribution, have variation in their abundances. Fabaceae (mainly Caesalpinoideae) and



Passifloraceae are more important in America and in Africa than in Asia. Lecythidaceae is much larger in the New than in the Old World, especially in Amazon and Orinoco Basin, both in South America, where there are 105 species of 11 genera. This same pattern is shared by Chrysobalanaceae.

Table 1. Largest Angiosperms families in tropical rain forests.

Dipterocarpaceae, which is a large and dominant family of the flora of Southeast Asia is absent in Australia, while in Africa it is represented only by two genera (Monotes and Marquesia) and by the monotypic genera Pakaraimaea (from Guayana) and Pseudomonotes (from Colombia) in the Neotropics.

The Gymnosperms, unimportant group in tropical forests, are represented mainly by the families Araucariacae and Podocarpaceae. Nowadays, the Araucariaceae is constituted by the genera Araucaria Juss. (Figure 2) that is confined to the southern hemisphere, with species in New Caledonia, New Guinea, Malaysia, Philippines, South America, and Northeast Queensland, Australia. On the other hand, the Podocarpaceae family is represented by 17 genera and about 125 species that are mainly distributed in the subtropical mountains of the Southern Hemisphere. However, most members of this family are represented by the genus Podocarpus (widely distributed), but the genus Sundacarpus, with only one species, Sundacarpus amarus (Blume) C.N. Page, is native of Indonesian islands (Sulawesi, Timor, Sumbawa, Java, Sumatra, and Sabah province on the island of Borneo), Philippines (Mindanao and Luzon), New Guinea and parts of Australia (including northeastern coastal Queensland) and Malaysia.

Figure 2. In the tropics, Gymnosperms are less representative, but in the mountainous areas of southern Atlantic Brazil and extends into northeastern

Argentina, we can find the endangered Brazilian Araucaria (Araucaria angustifolia). Forest with Araucaria angustifolia are easily set apart from

other portions of the Brazilian Atlantic forest. However apparent homogeneity, Araucaria forests represent an extraordinary mosaic combining species from a relict coniferous forest (including several Andean genera) with

Atlantic forest species. In this mosaic, several endemic species are found.

Tropical rain forest largely varies as regards to phytophysiognomies due to differences of altitude (lowland, lower montane, upper montane and cloud montane), annual precipitation, soil types and the degree of continentality. Following these changes, the flora also varies to a greater or lesser degree between forest formations, and the differences in species and genera are the most striking.

For example, in the lowland Atlantic coastal forest of northeastern Brazil between south Bahia state and neighboring northern Espírito Santo state, corresponding to an area of ca 72,000 km², the family Lauraceae is not very conspicuous (there are just over 50 species throughout the region). On the



other hand, in only 1 ha of upper montane forest (ca 800 m high) in Santa Lucia Biological Station, in southern Espírito Santo state, 46 tree species of Lauraceae can be found, indicating its preference to montane environments.

In addition, although the forest in the Amazon basin is a continuous block, the abundance of elements of given botanical families of woody plant species varies from area to area. For instance, Fabaceae and Moraceae are the most important families in the Ecuadorian Amazon, while Moraceae and Myristicaceae are predominant in the Bolivian Amazon, and Lecythidaceae and Moraceae are well represented in Central Amazon forest. On the other hand, comparisons between the elements of the woody flora of the Amazon Forest and the Atlantic Forest reveal that many individual species co-occur in both floristic domains. This can be explained, at least in part, by the migration of these species across the dendritic drainage of gallery forests that establishes connection between these two blocks of rain forests.

4. Biodiversity

4.1. Tropical Rain Forests are generally Rich in Species and Endemism

Within the 10 million species that possibly exist on Earth, half or more are found in tropical forests. However, all this biodiversity is distributed in different ways between rain forests and dry forests. Thus, rain forests are generally richer in species than dry forests. Such characteristic seems to be related to environmental factors, mainly water availability. In fact, tropical forests of high diversity are distributed throughout all tropical zones, but they tend to concentrate in low areas that receive regular and abundant rain throughout the year. In Malaysia, the lowland forests of the Lambir Hills National Park and the Pasoh Forest Reserve are examples of this situation (see number of tree species in Table 2).

Table 2. Data of tropical rain forests that compose the network of the forest dynamics plots organized by the Center for Tropical Forest Science /

Smithsonian Tropical Research Institute.

Another common pattern is that the diversity found in African rain forest is often lower than the diversity of American and Indo-Malayan rain forests. In mainland Africa there are about sixty species of palms, although in Madagascar there are about 170, most of which are endemics. In both tropical America and Malaysia there are over 1,000 species of palms. In addition, the Ituri Forest, in Democratic Republic of Congo, and the Korup National Park, in Cameroon, are between the African forests with highest richness, but they have less tree species than areas of Asia and Latin America (see Table 2).

The lower diversity of African forests has been related to the uplifting of its land surface in the Tertiary, which caused a desiccation of the climate, and a reduced availability of large areas for the occurrence of refuges in those arid periods. One of the few large areas of endemism in mainland Africa is between Nigeria and the Democratic Republic of Congo (the Cross River-Mayombe Pleistocene Refuge). Outside the continent, Madagascar has one of the highest levels of endemics of the Earth, but the surface of the island is not exclusively covered by tropical moist forest. Of the nearly 12,000 species of plants, between 70 and 80% are endemic. Ten families and 260 genera of plants are endemics there; only Australia has more endemic plant species. Of



the 8 species of baobab found in the world, six are endemic to Madagascar.

The northwest of the South America (ecological region of Chocó-Darién) and the coast of Brazil possess the higher levels of diversity and endemism of the world. The ecological region of Chocó-Darién, with 196,400 km², initiates in the province of Darién, in the Canal of Panama, and spreads southwards passing by the Pacific coast of Colombia until Cabo Pasado, in the province of Manabí, North Ecuador. Annual precipitation varies from North to South and in the Chocó-Darién, one of the most humid places of the world; it reaches 4,000-9,000 mm. The moist forests cover about 90% of the ecological region, from sea level to altitudes of 2,700 m, and the lowland moist forests are the most significant, with higher biodiversity. Estimates suggest that the flora of Chocó-Darién has 9,000 vascular plant species (with 25% of endemism). For vertebrates, for instance, endemism is also high (total 1,625 species of which 418 are endemic). The Yasuní National Park is in Chocó-Darién and has over 1,000 tree species (see Table 2).

Despite controversies regarding the definition of the Atlantic Forest, data available for the broadest definition (1,300,000 km² that encloses moist forests of the Brazilian coast and continental semi-deciduous forests) indicate the existence of 2,330 species of vertebrates (732 endemics), and about 20,000 species of plants (8,000 endemics).

4.2. The Diversity in Local Scale

Alpha diversity - or the wealth of species in a local scale - in the tropical forests is often higher than most terrestrial ecosystems as a result of the sparse distribution of individuals of the majority of the populations. Thus, in a given area many species (called rare) are represented by small populations, whereas a reduced number of species (called dominant) is endowed with populations with many individuals, constituting what is called an "oligarchy". In phytosociological studies, the registering of species with only one or two individuals per hectare is rather common. For example, in the Atlantic Forest of the Santa Lúcia Biological Station, in southeast Brazil, approximately 45% of the 384 registered trees species in a 1-hectare forest inventory are represented by 1 or 2 trees/ha, whereas the ten most representative species accumulate 26% of the trees.

In fact, one of the key questions in ecology of biological communities is how high levels of alpha diversity are kept in tropical forests. Some hypotheses, which are often mutually compatible, have suggested mechanisms that explain this pattern. Amongst the best known, there are the Janzen-Connell Hypothesis, the Regeneration-Niche Hypothesis and the Hypothesis of Gap Dynamics. The Janzen-Connell Hypothesis proposes that seedlings next to co-specific adult trees generally suffer greater mortality than seedlings that are more distant. This is because the aggregation of individuals attracts more predators and pathogens, increasing mortality and limiting the establishment of new individuals to more distant areas from the co-specific adult. The Regeneration-Niche Hypothesis and that of Gap Dynamics are based on the cycle of development of the forest, where different species present different requirements for establishment and growth. This results in preference for certain environments within the mosaic of environments in the forest. The choice of these environments by the different species is related mainly to the light levels that reach the forest floor in each phase of development. Thus, a



great variety of environments allows the existence of diverse niches that will result in the maintenance of a great number of species (see also Section 5, next).

4.3. Diversity as a Result of Latitudinal Gradients

The greatest biodiversity of tropical forests (when compared to other climatic zones of the world) is one of the oldest and most accepted global biodiversity patterns. However, despite some controversy, latitude is not the determining factor of variation in regional distribution of biodiversity. Environmental factors correlated to the latitude are primarily responsible for such a distribution. It seems reasonable to argue that latitudinal gradients of diversity result not only of a single factor, but of a set of factors that act synergistically. In this line, some hypotheses are distinguished that try to explain the relations between latitudinal diversity gradients:

� Climatic stability and favorable environments: environments that are climatically steady possess one constant supplement of resources and create favorable conditions for the existence of many species.

� Time: diversity increases throughout time because it is a product of evolutionary processes. Speciation should have been faster and extinction less sharp in steady tropical environments than in temperate habitats, since during geological time the tropics had more climatic stability than temperate zones.

� Spatial heterogeneity: the more diverse the physical environment, the more diversified the inhabiting organisms.

� Productivity: in the tropics, light intensity and temperature are higher and, therefore, productivity is higher. With more available energy, it is likely that more species should benefit.

� Competition: competition between individuals of different species is higher in the tropics, reducing the size of each niche, but increasing the number of niches.

� Predation: the highest number of predators and parasites in the tropics reduces the size of the populations of carnivores. Small populations reduce competition levels and allow species addition, as much of carnivores as of predators;

� Disturbance: the occurrence of perturbation in various scales (e.g., climatic changes, hurricanes, landslides, volcanic flooding and eruptions) delays the process of competitive exclusion and allows the coexistence of many species. Hence, when disturbances are small, less competitive species are excluded, and when disturbances are high, even the highly competitive species might be lost.

4.4. The Paradox of the Monodominant Forests

Nowhere diversity is greater than in the tropics. As seen in the previous sections of this chapter, the tropics are widely renowned for their spectacular plant diversity, and the occurrence of one or a few species dominating large areas of tropical forest was until the mid-1980's considered uncommon.



However, monodominant rain forests have been found in all regions of the tropics. They can occur side by side with highly diverse forests and these monodominant forests are often similar in species composition to the adjacent mixed forests.

It is interesting that most tropical monodominant forests reported in Africa and America are dominated by legume trees, mainly Caesalpiniaceae species (i.e. Cynometra alexandri C. H. Wright, Gilbertiodendron dewevrei (De Wild.) J. Léonard, Julbernardia seretii Troupin and Talbotiella gentii Hutch. & Greenway in Africa, and Eperua purpurea Benth, Monopteryx uaucu Spruce ex Benth, Mora excelsa Benth and Peltogyne gracilipes Ducke in America), while in Asia they are dominated by dipterocarp trees (Dipterocarpaceae) such as Shorea curtisii Dyer ex King and Dryobalanops aromatica C. F. Gaertn.

A large number of studies has been published on the mechanisms maintaining high diversity among the canopy trees, such as compensatory mechanisms, predation and herbivory, disturbance and neutral theory of tropical forest dynamics. On the other hand, little attention has been paid to low-diversity communities and only by the end of the 1980s attempts were made to explain the mechanisms that produce or maintain low-diversity among the canopy trees of tropical forests. Many abiotic and biotic factors have been cited to lead dominance in a community, such as soil moisture regime or water-table level, soil nutrient concentrations, wildfire, seed predation and herbivory, allelopathy or ectomycorrhizas. In some of these cases, the occurrence of monodominance in a community seems to be related to a single environmental stress. However, monodominant forests also occur on well-drained soils and adjacent to species-rich forests where soils show similar characteristics. According to Connell & Lowman (1989) monodominant forests on well-drained soils can be produced by two ways:

� The most common species produces abundant seeds and disperse them into a large open patch during the short period available before canopy closure;

� The most common species gradually invades an existing diverse rain forest by tree-by-tree replacement.

Therefore, a monodominant species is likely to be the species most tolerant of adverse conditions and also the most efficient competitor for resources such as light, water or soil nutrients. We can recognize two types of monodominant forest:

� Type I: with a persistent dominant that, once established, persists because of its abundant regeneration or its superior ability to exploit resources;

� Type II: with a temporary dominant that does not persist beyond one generation and shows poor recruitment in the understory because its seedlings cannot establish and survive after canopy closure. This type is related to an early successional process.

Other authors also recognized these two types and similar mechanisms to those proposed by Connell and Lowman for the maintenance of the dominance. However, the hypotheses for the origin of the dominance were



different. While some authors emphasized the importance of the ectomycorrhizal association in promoting type I dominance, others considered the disturbance (or successional stage) the key factor. According to Hart and collaborators, type I forests occur where disturbance is infrequent and slight (late succession). In this case, the dominant species has lower seed predation and herbivory than the other species. Type II dominance occurs where disturbance is frequent and large (early succession) and so the dominant species shows poor recruitment in the understorey. In the case of intermediate disturbance (mid succession) a species-rich forest is expected, with greater abundance of tree falls and shade-intolerant species.

More recently, the ‘suite of traits’ hypothesis was proposed by Torti and collaborators in 2001, where adults of monodominant species have a number of traits that alter the understory environment in such a way that inhibits recruitment by other tree species. Seedlings and saplings of monodominants, in turn, are thought to possess a number of traits that allow them to tolerate the stressful environment created by the adults. Although the suite of traits hypothesis (Table 3) seems well-supported for the Gilbertiodendron system, does the hypothesis apply to other monodominant species as well? An analysis based on available data for tropical monodominant species provides initial support for this hypothesis (Table 4). Monodominant species, in general, have similar traits, although they did not possess all traits considered as potentially important.

Table 3. Proposed suite of traits necessary for a plant to be a tropical monodominant. Plants do not have to possess all traits, but the possession of

just a few does not result in monodominance. (from Torti et al. 2001)

Table 4. A comparison of traits of tropical monodominant species (> 60% dominance) in lowland, tropical rain forest on well-drained soils (modified

from Torti et al. 2001).

An interesting case study is that of Peltogyne gracilipes that forms the only monodominant forest that has been described in the Amazon Basin (Figure 3). Large Peltogyne forests exist in and around Maraca Island, a protected ecological reserve with an established biological station (3° 15’N and 61° 22’W) in Boa Vista district, Roraima State, northern Brazil. The island is 60 km long and 15-25 km wide, with a total area of approximately 100,000 ha. Annual rainfall on the island is 1750-2000 mm, with a distinct dry season from December-February. Previous research shows that soils on Maraca Island are generally poor and that the only difference between soils in the Peltogyne forest and those in forests without Peltogyne is that the Peltogyne forest soils are rich in magnesium and therefore exhibit a high Mg/Ca ratio. Because this forest has high soil and foliar Mg concentrations, and Mg is known to be toxic to plant growth at high concentrations, the monodominance of Peltogyne was related to its deciduousness and faster leaf-decomposition in the dry season, which coincides with a large leaf fall. Magnesium is lost quickly from the Peltogyne leaves and the resultant pulses of Mg into the soil during the heavy rains at the beginning of the wet season may be deleterious for other species which are not adapted to high solution Mg concentrations. Therefore, Peltogyne dominance seems also related to the pattern of its nutrient cycling and the seasonal pulses of toxic Mg.

Peltogyne has a number of traits thought to be important in the suite of traits



hypothesis (Table 4). Peltogyne is a mast fruiting species, producing seeds every 2-4 years. Juveniles are slow growers, shade tolerant, and appear to suffer low damage by herbivores. Unlike Gilbertiodendron, Peltogyne does not form ectomycorrhizae. Also, unlike Gilbertiodendron, adult Peltogyne trees are deciduous during the dry season, but juveniles do not lose their leaves. Peltogyne do not have poor quality leaf litter, although the high amounts of Mg they release may create a chemical barrier to the establishment of other species. Also, while Peltogyne leaf litter decomposes slowly, most of the nutrients are quickly mobilized from its decomposing leaves. Thus, the unique suites of traits possessed by adult and juvenile Peltogyne individuals couple together to favor monodominance in this system.

Figure 3. Aerial view of the Peltogyne monodominant forest and mixed forest boundary on Maracá Island, Roraima, Brazil. The pale areas are Peltogyne

forest.

5. Tropical Rain Forests are Dynamic

Plant communities are called "climaxes" when they have structure and composition in equilibrium. But, contrary to what the word "equilibrium" might suggest, stability here is of a dynamic nature. Thus, these communities are not "static" throughout time.

The process of regeneration in tropical forests is more complex than in temperate forests and the equilibrium is guaranteed by the incorporation of new components in substitution to what had been lost. This balance between losses and gain is based on the cyclical behavior of the forests, where three phases of development are recognized: mature (mature), open area (gap) and regeneration or construction (building). The mature phase shows trees in several layers and a closed canopy. Eventually trees of the canopy die or are damaged, knocking down lesser surrounding areas and forming bare places. These bare places are quickly filled by herbs, lianas and young trees. Some of these plants arise from banks of seeds and seedlings, while others simply burst from exposed roots and trunks broken. The regeneration phase corresponds to the growth of these components until the formation of a new canopy many years later, reestablishing the mature-phase stage. Interestingly, all these phases generally coexist in forest patches, resulting in a forest mosaic, resulting in a heterogeneous environment.

In this context, mortality, recruitment and growth of trees play an important role in the maintenance of the structure and diversity and in the processes of nutrient cycling in forests (more details in Section 6). The mortality of trees in tropical forests is the result of the combination of different biotic and abiotic factors. Four main causes of tree mortality can be defined, each one with its own spatial scale, regularity and frequency. The first one is related to endogenous processes of genetic origin that provoke a set of gradual physiological and metabolic alterations ultimately leading to death, known as



senescence. The second one refers to the sudden or gradual action of toxic substances, pathogens, parasites and consumers, in an individual or population context. The third cause is related to changes in abiotic factors, such as edaphic (soil) conditions, light intensity and natural flood regimes, causing an essential reduction in the energy availability and materials. The last possible cause is associated to the occurrence of catastrophic natural disturbance such as strong winds, uncommon storms, hurricanes, landslides, flooding, droughts and fires that can provoke irreversible damages to the trees.

In general, in tropical forest stands where only natural disturbance of small scale operate, mortality is highest for the youngest plants (i.e. seedlings), of any given population, which are often times numerous. However, curves of individual distribution in size classes often have a "reversed-J" shape, which means that smaller size classes have higher number of plants despite high mortality.

The recruitment is a spare mechanism of trees in forests that depends directly on the fecundity rates, the growth and the survival of young individuals of diverse species. Therefore, recruits emerge from seed bank, bank of seedlings or young trees, whose development is often enhanced by higher light availability provoked by gaps in the forest canopy. Recruitment substitutes dead trees and also contributes for the replacement of the live material in the forest. Thus, for forests in dynamic balance, the addition of the increase in biomass of surviving trees via growth to the increment of biomass of the new trees recruited must be approximately equal to the total of lost live material due to the fall of vegetative organs, such as leaves and branches, and for the death of trees.

6. Nutrient Cycling

6.1 An Overview

The often unseen processes that underlie most mechanisms of diversity distribution and patterns described in this chapter may be related to nutrient cycling as plant nutrient cycling and allocation patterns may alter the community biology and ecology of plants and animals in tropical forests. Chemical fertility and soil moisture are among the factors which have been considered important determinants of species richness in tropical forests. Early studies associated low species diversity with low soil nutrient availability, but no confirmation to this pattern has been found yet. The available data on soil-nutrients and tree species-richness are conflicting. These relations encompass nutrient cycling process in tropical forests described from now on in this chapter.

The term nutrient cycling involves geochemical, biogeochemical and biochemical pathways of the essential elements required to plants, mainly N, P, K, Ca, and Mg, which are most likely to limit primary production and other ecosystems functions, denominated nutrients. It is interesting the view that nutrient cycling encompasses a wide range of processes co-occurring on different timescale from minutes or days, as the turnover of available nutrients in soil solution, to millions of years, as the development of tropical soils. Three principal processes are measured in tropical forests: (i) inputs and



outputs from the forest, which includes throughfall and stemflow; (ii) internal pools and cycles within the forest ecosystem, which includes the feedback of nutrients from soil-plant (e.g. litterfall, decomposition, Figure 4), comprising most data; (iii) internal distribution of mobile elements (retranslocation). Those processes are interactive, controlling the availability, cycling and limitation of nutrients in tropical forests, and in terrestrial systems as a whole, despite their differences in timescale.

Figure 4. A litter trap in an Atlantic forest underground at the União Biological Reserve, Brazil, used to collect and measure the amount of litterfall

mass and nutrient input in forested ecosystems.

There is a "popular view" of the occurrence of primary and old secondary rain forests in infertile soils, having most of their nutrients in the above-ground living matter, maintaining high production by rapid and efficient nutrient cycling, having closed and tight nutrient cycles, since the first studies on nutrient cycling in tropical forest ecosystems in Ghana and in the Brazilian Amazon around the 1960s. However this view has been criticized and much more studies are needed to hold those assumptions as the pattern of nutrient cycling in tropical forests are diverse, and as Vitousek & Sanford in 1986 pointed out "it makes no more sense to describe a ‘typical’ tropical forest than a ‘typical’ temperate forest", although some patterns may be found.

Another ‘paradigm’ relates the occurrence of tropical forests on poor soils with specific features and strategies of plants, such as root mats or small sclerophyllous leaves. This assumption has been challenged, as some Amazonian rain forests do not present those characteristics. Nevertheless they are neither unproductive with a low nutrient demand, nor are particularly efficient in nutrient use or have a rapid nutrient recycling, as expected. It raised questions on the functional strategies of the tropical forests, which show no evidence of nutrient limitation, contradicting several generalizations about rain-forest nutrition.

6.2. Environmental Conditions Which Drive Nutrient Cycling in the Rain Forests

Some environmental conditions may drive nutrient cycling in the tropical forests such as climate, soils, species composition and sucessional stage. Litterfall seasonality is one of the processes strongly related to rainfall in moist and seasonally dry forest in opposite way. While in moist tropical forests as those in Australia, Brazil, New Guinea, Sarawak, Zaire the peak litterfall is in the wet season, in seasonally dry forests the peak of litterfall mass and nutrient input is in the dry season, as in some Amazon and Atlantic forest in Brazil, in secondary forest in Nigeria and elsewhere in the tropics. But even in some evergreen moist forests, the litter may fall in the dry season. This common pattern of tropical forests suggests that water deficit is one of the main factors of leaf-fall in those ecosystems. Nevertheless, quantities of litterfall is not determined only by climate, as moist or dry tropical forest



produce annually about 7 to 13 t/ha, a variation that may be driven also by other factors as floristic composition, sucessional stage or soil type.

Climate may also interfere with litter decomposition process, a critical step in nutrient cycling, which is the responsible for the transference of nutrients from the litter layer to the soil. Dry-season retardation of decomposition has been observed in moist and dry tropical forests. The faster decomposition process in the wet season is attributed to an increase in the activity of micro-decomposers and macro-fauna, and in some forests to a greater growth of fine roots. Rapid decomposition rate is a result of the initial rains stimulating mass loss and nutrient release after dry spells resulting in pulses of nutrients. Pulses of nutrients are known to be important regulators in tropical forests functioning.

The higher stock of nutrients in the small litter layer in the dry season in many forests may be a consequence of the high input and low litter decomposition rate during this season. However, although differences among sites may influence decomposition, the effects of substrate quality and soil fauna can be crucial in this process in tropical forests.

Altitude is also a factor that may interfere in rain forests structure, productivity, nutrient limitation and cycling. Most studies have been shown that tropical rain forests decrease in stature, above-ground biomass and net primary productivity, litterfall nutrient input, decomposition rate, and soils nitrogen concentration, with increasing elevation mainly in response to temperature decrease. In-situ fertilization experiments in montane forests have indicated that growth and litter production, are limited by N or N and P. However, the conclusions in relation to the effect of soils nutrient limitation and reduction of plant nutrients with altitude are not consistent, as it may be influenced by air temperature directly.

The relationship between soil fertility and nutrient cycling in rain forests has demonstrated that patterns of the cycles of nutrients differ in forests on different soils. It has been shown that moderately fertile soils support productive forests that cycle large quantities of nutrients, contrasting with forests on medium to low fertile soils that efficiently cycle smaller quantities of phosphorus and calcium, although they seems to be not limited by nitrogen, while forests on very low fertile soils cycle small quantities of N and P, with a high root/shoot ratio. Nevertheless, we may reinforce the position prior raised by Proctor in 1995 that rain forest soils are rarely critically evaluated and hard facts about relationship between rain forests and their soils are still relatively few, what causes a number of widely accepted ideas up to that moment about rain forest and their soils, including those relating to the proportions of nutrients in biomass and soils, the efficient cycling of nutrients and the importance of mycorrhizas, which are shown to be oversimplifications and based on slender evidences.

6.3. Floristic Composition, Diversity, Nutrient Cycling and Rain Forest Management

It is known that species create positive feedbacks to the patterns of nutrient cycling in natural ecosystems, further reducing nutrient availability in low-nutrient sites and in opposite way enhancing nutrient availability in high-nutrient ones. In fact, species effects have been found to be many times more



important than abiotic factors in controlling ecosystem fertility. Different studies in the tropics and elsewhere have been raised questions on the influence of specialist species which dominates some specific ecosystems on their function. It has been discussed that it might be true that ecosystems in regions with more diverse flora could function differently due to a greater diversity of species within sites, because members of an array of species could have complementary patterns of resource use or of responsiveness to disturbance.

Some studies have shown that key species, which represent dominant trees have a great influence on nutrient cycling through their litter in tropical ecosystems, for example the Peltogyne gracilipes in a monodominant Amazon forest (see above, Figure 5), Metrodorea nigra in seasonally dry Atlantic forest, or even nurse-plants such as Clusia hilariana in sand dune vegetation thickets in Brazil. The opposite also happens as nutrient availability and cycling may drive species dominance as seems the case for the forest type dominated by Peltogyne gracilipes described earlier in this chapter, and for some monodominant ectomycorrhizal tropical forests as those in Africa, which are related mainly to P control which is particularly important on highly weathered tropical soils.

Figure 5. Leaf litter layer composed mainly by Peltogyne leaves in the Peltogyne monodominant Amazon forest on Maracá Island, Brazil, at the end

of the dry season (March).

Nutrient cycling studies also help elucidate environment changes related to vegetation succession, as well as nutrient cycling and allocation patterns may also influence those processes. In general, there is an increase in biomass and nutrient accumulation in the tropical forests with successional stage, and secondary forests may present higher values than the stable mature forests.

The knowledge of roles of richness and composition is essential for understanding the function of preserved ecosystems as species are gained or lost. It is also true for degraded forests as there is a general trend of reducing tree diversity and changing in composition with the disturbance intensity. A less diverse and more disturbed (open) forest tends to have a rapid nutrient release from decomposing leaf-litter and it has been suggested that the successes of the system is more dependent of its capacity to retain nutrients.

It is already a general consensus that the understanding of nutrient cycling processes is fundamental to the management of natural and disturbed vegetation growing on tropical soils of low fertility. The deleterious effects of a variety of disturbances as deforestation, fire, selective logging and fragmentation on biomass, litter production, decomposition and nutrient dynamics were shown for a sort of African, Asian, central and south American rain forests.

The results from deforestation may vary with factors such as tree species, period and type of logging, rainfall pattern and soil properties. Although



relatively few trees are cut per hectare in a selective logging operation, the effects on ecosystem structure due to loss of nutrients may be underestimated. Fragmentation is one of the main consequences of deforestation in the rain forests (Figure 6) causing a variety of abiotic and biotic changes in the community, which may also alter litterfall and nutrient dynamics. There are still few and sometimes contrasting data on the effects of rain forest fragmentation on those processes, however the possible synergism between forest fragmentation and fires has been shown in the beginning of this century (2004) for the Amazon, amplifying the risk of threatening the rain forests elsewhere in the globe, as fragmentation process is already a fate for the tropics (Figure 7). The role of nutrients in regulating organic matter decomposition has also been discussed in the present decade for tropical rain forests and its consequence on global carbon cycle stressed as tropical forests contain up to 40 % of terrestrial carbon biomass and account for one-third of annual biosphere-atmosphere CO2 exchange.

Figure 6. Aerial view of a rain forest fragment of Atlantic forest at União Biological Reserve, Brazil. Note that different types of border surround the

fragment.

Figure 7. Border of an Atlantic forest fragment at Guaxindiba Biological Station, Brazil, just after a fire. Note the invaders grasses at the fragment

border, which may facilitate and amplify the fire risk.

The advantage of more structural diversity ecosystem, as the conservation of soil condition and nutrient dynamics and the control of intensity and amplitude of disturbance have been demonstrated all over the tropics in different aspects of nutrients maintenance and cycling. Although some managed systems promote natural regeneration, by altering but not interrupting the basic structure and functioning of the forest, the impacts of the different types of disturbances on nutrients stocks and dynamics must be considered important in tropical forests and their effects need to be evaluated carefully and in long-term studies. The use of key species as indicators of disturbance is regarded as useful in monitoring and managing some tropical forests.

7. Conclusion and Outlook

Despite the importance of the world’s tropical rain forest, our knowledge concerning its flora is still limited and based on relatively few inventories. It is important to highlight that although the number of floristic inventories in



tropical rain forests has increased, only few studies cover large geographical areas, especially in Amazon forest, with most of them concentrated inside or nearby Conservation Units such as Barro Colorado, Cocha Cashu, La Selva and Reserva Ducke. Moreover, although a pool of information has been obtained in those last four decades on nutrient cycling that provided answers to questions about their stock and function in tropical forests, many processes and mechanisms are still poorly known to make a more consistent and general conclusion on its nutrient limitation, dynamics and cycling specially considering the great diversity of rain forests and its importance to an increasingly changing world. So, the scarcity of field data in tropical rain forests still limits our understanding on patterns of species richness, species distribution and functioning.

Another important point is that most available data on floristic composition are based on quantitative plant inventories that only include large trees (plants with a stem diameter greater than 10 cm at breast height), with few samples of other life forms such as lianes, epiphytes, and herbs. These inventories have about 20-30% of the tree species sample as unidentified species or morphospecies. A morphospecies can be a new species or, as in most cases, a described species that has not yet been identified. This factor means that our knowledge of the tropical flora is still poor and efforts are needed to improve it. The annual area deforested in the tropics is very large, and several papers have shown the relationship between deforestation and species loss. Thus, attention should be paid to geographical areas that are poorly collected and/or are suffering high deforestation rates, since good floristic data are important not just for plant systematic, phytogeographic and evolution studies but also for conservation and management of the tropical vegetation.

Related Chapters

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Glossary

Allelopathy : Is a chemical process of inhibition of growth of a plant due to biomolecules released by another.

Biomass : The weight of a living organism, or of all the organisms in an ecosystem or in a habitat.

Biochemical cycles

: Encompass internal transfers or translocation of nutrients within plants.

Biogeochemical cycles

: Encompass the recycling of nutrients between the soil and plants and heterotrophs.

Continental drift : The hypothetical tendency or ability of continents to drift on the earth's surface because of weakness of the sub-oceanic crust. Today, scientists believe that 200 million years ago the Earth's continents were joined together to form one gigantic supercontinent, called Pangaea.

Dendritic drainage

: Is the pattern formed by the streams, rivers, and lakes in a particular drainage basin.

Decomposition : Is the natural process carried out by invertebrates, fungi



and bacteria which a dead plant or animal tissue is broken down, resulting into nutrients which return to the soil.

Early succession : The initial stage of a succession process. Ectomycorrhizas : EcM, typically form between the roots of woody plants

and fungi belonging to the divisions Basidiomycota, Ascomycota, or Zygomycota.These are external mycorrhizae which form a loose sheet of hyphae around tree roots and a branching hyphal network (Hartig net) inside the root.

Fragmentation : Is a form of habitat fragmentation occurring when forests are cut down in a manner that leaves relatively small, isolated patches of forest known as forest fragments or forest remnants.

Gallery forest : A forest along a river or stream. Genetic diversity : Is a level of biodiversity that refers to the total number

of genetic characteristics in the genetic makeup of a species.

Geochemical cycles

: Encompass inputs and losses of nutrients to the large abiotic environment.

Ice ages : Is a period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers.

Late succession : The final stage of the succession process. Litterfall : Consists of leaves, flowers and fruits, woody and trash

(very small parts from a variety of origins) that fall to the soil floor.

Mid succession : The intermediate stage of a succession process. Mast fruiting : Is the intermittent and synchronous production of large

fruits. Monodominant forest

: A forest in which a single late successional tree species comprises 60% of the canopy trees or of the total basal area.

Neotropical : Refers to occurrence in the tropical regions of the New World, i.e. the Americas.

Pantropical : Terms used to define an area of geographical occurrence of an organism, or group of organisms. When the distribution of a taxon is pantropical, it means that the taxon occurs in the tropical regions of all of the major continents.

Phytophysiognomy : The characteristic appearance of a plant community by which it can be recognized at a distance.

Phytosociology : Is the study of the characteristics, classification, relationships, and distribution of plant communities.

Primary or mature forest

: Vegetation which has not been disturbed or changed by man.

Retranslocation : Is the nutrient removal from plant tissue into the perennial part of the plant prior to senescence, which occurs primarily from leaves.

Seed bank : All dormant but viable seeds in the soil.



Bibliography

Connell, J. H and Lowman, M. D. (1989). Low-diversity tropical rain forests: some possible mechanisms for their existence. American Naturalist 134: 88-119. [This work provides a general view on the mechanisms for monodominance in tropical forests.]

Hart, T. B.; Hart, J. A. and Murphy, P. G. (1989). Monodominant and species-rich forests of the humid tropics: causes for their co-occurrence. American Naturalist 133: 613-633. [This paper highlights the importance of disturbance and the life history traits for the occurrence of monodominant tropical forests.]

Jordan. C. F. (1985). Nutrient Cycling in Tropical Forest Ecosystems: Principles and their application in management and conservation. John Willey & Sons, New York, USA. 190p. [This is one of the first book that discuss the factors related to productivity and cycling of nutrients on tropical forest ecosystems and the implications of different management systems on those process.]

Kreft, H. and Jetz, W. (2007). Global patterns and determinants of vascular plant diversity. PNAS 104: 5925-5930. [This recent paper discusses the distribution patterns of diversity of the vascular plants around the world.]

Leigh Jr., E. G.; Davidar, P.; Dick, C. W.; et al. (2004). Why Do Some Tropical Forests Have So Many Species of Trees? Biotropica 36: 447-473. [This is an excellent review about tree diversity in the tropics.]

Mittermeier, R. A.; Gil, P. R.; Hoffmann, M.; et al. (2004). Hotspots revisited: earth’s biologically richest and most endangered terrestrial ecoregions. Cemex, Washington, DC. [This book identifies 34 regions worldwide presents where 75 percent of the planet’s most threatened mammals, birds, and amphibians survive within habitat covering just 2.3 percent of the Earth’s surface.]

Nascimento, M. T.; Proctor, J. and Villela, D. M. (1997). Forest structure, floristic composition and soils of an Amazonian monodominant forest on Maracá Island, Roraima, Brazil. Edinburgh Journal of Botany 54: 1-38. [In this paper the authors describe the only monodominant forest that has been reported for the Amazon Basin.]

Osborne, P. L. (2000). Tropical Ecosystems and Ecological Concepts. Cambridge University Press, Cambridge. 464p. [A good textbook for students of tropical ecology. It covers all major tropical ecosystems.]

Proctor, J. (1987). Nutrient cycling in primary and old secondary rain forests. Applied Geography 7: 135-152. [One of the first critical review on nutrient cycling patterns in tropical rain forest.]

Proctor, J. (1989). Mineral Nutrients in Tropical Forests and Savanna Ecosystems. Blackwell Scientific Publications, Oxford, UK. 473p. [This book has 28 Chapters on different aspects and views of nutrient cycling in tropical vegetation.]

Seedling : A young plant growing from its seed. Shade tolerant : Plant adapted to growth under low irradiance. Stemflow : The flow of rain water down the trunk or stem of a

plant. Successional stage : A phase of the succession process is a change in plants

and animals which occurs periodically in all communities.

Throughfall : Describes the process of rain water passing through the plant canopy.

Well-drained soils : Are soils that water is removed from readily (but not rapidly) and they are not wet for significant periods of time.



Proctor. J. (1995). Rain forest and their soils. In: Primack, R. and Lovejoy, T. (Editors). Ecology, Conservation and Management of South-east Asian Rain forests. Yale University Press, USA. 304p. [This paper discuss some assumptions about rain forests and their soils.]

Richards, P. W. (1996). The tropical rain forest an ecological study, 2nd Ed. Cambridge University Press: Cambridge UK. 575 p. [This is a classical book containing all aspects of structure, physiognomy, floristics and human impacts of different types of tropical rain forests.]

Scott, D. A., Proctor, J. and Thompson, J. (1992). Ecological studies on a lowland evergreen rain forest on Maracá Island, Roraima, Brazil. II. Litter and nutrient cycling. Journal of Ecology 80: 705:717. [This paper argues the assumption which relates the occurrence of tropical forests on poor soils with specific features and strategies of plants.]

Torti, S. D.; Coley, P.D. and Kursar, T. A. (2001). Causes and consequences of monodominance in tropical lowland forests. American Naturalist 57: 141-153. [This paper provides a new hypothesis on monodominance occurrence, including the data shown in Table 1.]

Vasconcelos, H. L. and Luizão, F. J. (2004). Litter production and litter-nutrient concentrations in a fragmented Amazonian Landscape: Edge and soil effects. Ecological Applications 14: 884-892. [This paper evaluates the edge effects of fragmentation on litter on a large-scale experiment in the central Amazon.]

Vitousek, P. M. and Sanford Jr., R. L. (1986). Nutrient Cycling in moist tropical forest. Ann. Rev. Ecol. Syst. 17: 137 – 167. [Important review on nutrient cycling patterns in tropical rain forest relating and discussing the mechanisms that regulates this process.]

Vitousek, P. (2004). Nutrient Cycling and Limitation: Hawaii as a model system. Princeton University Press, New Jersey. USA. 223p. [This is one of the most recent book which address the assumption of nutrient cycling in forests.]

Whitmore, T. C. (1990). An introduction to tropical rain forests. Oxford University Press: Oxford, UK. [This is a well-written introductory book on tropical rain forests for a broad readership.]

Wright, S. J. (2002). Plant diversity in tropical forests: a review of mechanisms of species coexistence. Oecologia 130: 1-14. [Important review on plant species coexistence in hyper-diverse communities.]

Biographical Sketches

Felipe Zamborlini Saiter is Analyst for the Environment at the Management of Natural Resources of the Instituto Estadual de Meio Ambiente e Recursos Hídricos, Espírito Santo, Brazil, and Professor of Ecology of the Escola Superior São Francisco de Assis, Espírito Santo, Brazil. He works in government projects for the conservation of natural resources and his present research interests are dynamics of plant communities and phytogeography.

Tânia Wendt is Professor of Plant Taxonomy at the Botany Department of the Universidade Federal do Rio de Janeiro, Brazil. She has a career-commitment to research on plant systematics especially within Bromeliaceae, a keystone family within the Atlantic tropical rain forest biome, and its unique ecological adaptations.

Dora M. Villela is an Associate Professor at the Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Rio de Janeiro, Brazil. Her research interests emphasize nutrient cycling of forested systems. She has been working for over two decades on cerrado vegetation and monodominant forests in the Amazon. More recently, her main interest has been on Atlantic forest ecosystems and the effects of fragmentation on nutrient cycling.

Marcelo T. Nascimento is an Associate Professor and Curator of the Herbarium at the Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Rio de Janeiro. For the last 15 years, his research has focused on plant communities, including phytosociological studies, herbivory, and plant population dynamics.



To cite this chapter F. Z. Saiter, T. Wendt, D. M. Villela, M. T. Nascimento ,(2008),RAIN FORESTS: FLORISTICS, in International Commission on Tropical Biology and Natural Resources, [Eds. Kleber Del Claro,Paulo S. Oliveira,Victor Rico-Gray,Ana Angelica Almeida Barbosa,Arturo Bonet,Fabio Rubio Scarano,Francisco Jose Morales Garzon,Gloria Carrion Villarnovo,Lisias Coelho,Marcus Vinicius Sampaio,Mauricio Quesada,Molly R.Morris,Nelson Ramirez,Oswaldo Marcal Junior,Regina Helena Ferraz Macedo,Robert J.Marquis,Rogerio Parentoni Martins,Silvio Carlos Rodrigues,Ulrich Luttge], in Encyclopedia of Life Support Systems (EOLSS), Developed under the Auspices of the UNESCO, Eolss Publishers,Oxford,UK, [http://www.eolss.net] [Retrieved May 18, 2009]

©UNESCO-EOLSS Encyclopedia of Life Support Systems



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