Exercise 2: Species-Area Curves and Measuring Biodiversity
J. Danoff-Burg, T. Kittel, and A. Hoylman.
of the Shared Activities — Data are Shared Among all Biomes
The Local Biome: The Moist Atlantic Forest or Mata AtlânticaAs discussed in Ex. 1, a biome is a large-scale environment where similar abiotic conditions result in a major vegetation association dominating the landscape. Examples include tropical rain forest, boreal forest, hot and cold deserts, grassland, tundra, etc.
The Instituto de Pesquisas Ecologicas Center (IPE) sits in the southern reaches of the Mata Atlântica, a section of the South American Rainforest Biome. Major divisions of the South American Rainforest Biome are (1) the South American Coastal Tropical Forests, (3) South American Interior Tropical Forests, and (3) the Amazon Rainforest.
The South American (SA) Coastal and Interior Tropical Forests stretch through 17 Brazilian states, along nearly the entire coast of the continent. Beginning with the border with Uruguay to the south, all the way around the eastern tip, and up to the Guyana Shield to the north of Brazil. The historic range of the forest forest proceeded furthest inland in the south of Brazil, into the states of Goias, Mato Grosso do Sul, Minas Gerais, and into a significant portion of Paraguay to the west of Brazil.
The Mata Atlântica occupies parts of both of the first two divisions, but is mostly located on the southern coast of Brazil, from Rio Grande do Norte to the border with Uruguay. Historically, this coast was covered by the Atlantic Forest, one of the most biologically diverse places on the planet. There are more than 10,000 plant species found there, half of which are unique or endemic to this area as are least 5% of the world's butterfly species. The canopy is not as high as the Amazonian Rainforest, nor are there as many canopy layers. In the Amazon, it is common for the tallest canopy to be as tall as 50 meters, but in the Mata Atlântica, it is much shorter - usually on the order of 20-30 meters high.
However, at present only approximately 7.3% (94,000) of the original 1,290,692 square kilometers of Mata Atlântica remain in Brazil. As is often the case, the most biologically diverse places are also the most favorable for human settlement. Biologically diverse coastal areas in particular are threatened all over the Earth. The Atlantic Forest is a perfect example of this phenomenon. Over 100 million Brazilians live within the Atlantic Forest, including the cities of São Paulo, Rio de Janeiro, Belo Horizonte, and Porto Alegre. Given that only around 160 million people live in Brazil at present, it is clear that the Atlantic Forest has been vital for the growth of the country.
The Mata Atlântica
At present, large intact stretches of the forest are rare, with most being small, isolated patches. The largest remnants of the forest exist in the states of São Paulo, Parana, Santa Catalina, and Rio de Janeiro. Much of what remains of the forest has been cut over for pasture lands, agriculture, or forestry and has subsequently regrown with what is called Secondary Forest. Most of the undisturbed areas, or
Primary Forests, are isolated to steep hill-sides or are found in inaccessible areas. One of the locations that we will be visiting during the class, Intervales State Park, is a good example of how forests remain in steep areas.
The forest is so biologically diverse because of several reasons: forest refugia, Most of what is now the Mata Atlântica was under water during recent glacial periods, a fact that can be readily observed by the near total absence of rocks in many areas (although this is not true for the area around IPE's headquarters). The great diversity of elevation in the area formed many forest refugia, where native biodiversity remained until they were able to expand their range. These refugia, which are a special type of inland islands with each mountain being comparable to an island, served as the source populations from which the entire Mata Atlântica was repopulated. These refugia allowed for a great number of species to arise. The isolated populations could genetically diverge from other populations with whom they could previously interbreed (more on this during Module 3). Once the ranges were expanded and they had sufficiently diverged, the newly formed species could not interbreed with the other populations.
As a consequence, a great many species currently exist in the Mata Atlântica. Although the number of these forest refugia is debated, it is clear that there are around four of them in the forest. The refugia are of great interest as it is thought that they are some of the most biologically diverse areas in an already biologically diverse location and as a consequence, they are centers for a great many species that are found only there - called centers of endemism.
Many of the huge number of the species that are found within the Mata Atlântica are unique to this area, or are endemic. A listing available from Conservation International details 250 species of mammals (55 endemic), 340 amphibians (90 endemic), 1,023 birds (188 endemic), and approximately 20,000 trees, half of them endemic. For many higher level taxa (genus, family, order, etc.) like primates, more than two-thirds are endemic. Therefore the burgeoning threats posed to the Atlantic forest by human population promises to wipe out one of the most unique areas in the world. This is the reason why many organizations place the Mata Atlântica in the top five of the most important biological hotspots that head the list of areas to be conserved worldwide. We will discuss hotspots further in Module 16.
The Mata Atlântica has frequently been divided into domains that were established by the Brazilian Vegetation Map of IBGE (1988). Eight domains are usually recognized by this work: "ombrophilous dense atlantic forests; mixed ombrophlilous forests; open ombrophilous forests; semidecidual stational forests; decidual stational forests; the countryside swamps, the northeastern forest enclaves and the associated ecosystems - mangroves and restingas.” We will visit most of these domains, with the probable exception of the countryside swamps.
This lab aims to demonstrate the types of communities and species found within the Mata Atlântica and to orient students to the area. It also introduces the concepts of orienteering (topographic map and GPS use), ecological scale, and biodiversity based on observations made in the field. We will further explore ecological significance of biodiversity in the module on community dynamics (Module 5), but for now we will take this opportunity to become familiar with the Mata Atlântica.
GPSNavigating around the world using GPS is an important skill that we will learn today. Knowing your way around a landscape and being able to accurately relocate a site are the most important contributions of GPS. Often the accuracy is to a previously unattainable level, such as that of centimeters.
High accuracy GPS is attained by a two-step process. First, the GPS receiver obtains geographic information in the field from a subset of the satellites that are constantly orbiting the planet. These readings are then stored in the receiver. Then, using software supplied by the GPS company takes the information obtained from the satellites and integrates it to triangulate a more accurate location. This secondary data analysis, called differential post-processing, will allow us to attain 1-3 meter accuracy, if we use the Trimble GeoExplorer 3 GPS units that we have. However, most of our work will be done with the less accurate Garmin eTrek GPS unit, as they tend to obtain better signal in this area of the world.
GPS will be used during this class to determine the precise latitude and longitude of all field sites so that when we enter some of the data into the central repository (eBiome), we can georeference (or precisely locate on the Earth's coordinate system) all datapoints. As a consequence, current and future data can be queried and analyzed spatially. Spatial analysis and the benefits posed by it are subjects that we will discuss and explore in this Module.
Task A: Orienteering and Familiarity with Mata Atlântica Plant Communities (Sunday and Tuesday, late afternoons)
Task B: Measuring Local Biodiversity and the Importance of Spatial Scale (Day 1 of Exercise 2, Tuesday)
Task C: Climates of Brazil (Day 2)
Task D: Regional Biodiversity (Day 2) (Optional)
Task E: Cross-site Analysis (Day 2)
All Materials Copyright © 2001 by J. Danoff-Burg, T. Kittel, and A. Hoylman.
All Rights Reserved.
Rev. 4/20/01, 5/25/01, 5/21/02