SEE-U 2000: Atlantic Forest - Module 1:Exercise 1

## Exercise 1: The Terrestrial Biomes: Identification of Major Controls over Structure and Distribution
Module 1: Introduction to Global Biomes

### Your Questions

1. What are the general ecological features of each of the major terrestrial biomes, e.g., in terms of dominant vegetation structure and specifically for biomes in Brazil and South America
2. What features of climate characterize each of the biomes?
3. How does the climate prescribe the dominant vegetation structure of each biome?

### Background

#### Characterization of Climate Controls.

The distribution of vegetation is controlled by several factors (regional climate, topography, soil parent material, time, and organisms). However, at the broadest scale, the scale of biomes, global climate patterns are the primary factor determining the structure and distribution of vegetation. We will discuss the role of the other 4 factors in subsequent modules on the local biome (Module 2) and abiotic factors (Section C).

Aspects of climate that exert strong control over vegetation are temperature, precipitation, humidity, solar radiation, and wind. Each of these affect plant physiology directly (through effects on photosynthesis and respiration) or indirectly (through effects on nutrient availability via decomposition, and soil development).

The simplest schemes relating biome distribution to climate evaluate annual or monthly mean temperature and precipitation. In this exercise, we will use a system devised by Henrick Walter to plot monthly mean temperature and precipitation on the same graph in a way that illustrates both (1) seasonality of thermal regime and (2) seasonality of moisture availability. In this way, these climate diagrams depict key (but not all) features of climate that control the structure and distribution of biomes.

Information on the features of a Walter diagram is in the Lieth et al. CD, or will available as a handout.

#### Characterization of Vegetation Structure.

At the local scale, the structure of vegetation is usually described in terms of dominant plant species that are commonly found together as a plant community or association.

At the biome level, however, this approach is problematic because species that characterize a biome on one continent are generally not those that typify the biome on another continent (or even in different regions of the same continent). Rather, we find that species of similar lifeform or plant functional type describe a biome. For example, the mid-latitude forests of eastern US, eastern China, and western Europe are primarily dominated by Winter-Deciduous Broadleafed Trees.

At the simplest level, biomes are first distinguished by the dominance and density of trees, shrubs, vs. grasses:

- Forest woodland savanna grassland
- Shrubland shrubsteppe grassland

Then, functional aspects of vegetation are included in the definition:

- Leaf duration—Evergreen, winter or drought-deciduous
- Leaf shape/size—Broadleaf, needleleaf, microphyllous (small leafed)
- Photosynthetic pathway, e.g. for Grasses—C3, C4 [less commonly used]

And finally, zonal (latitudinal/climatic) distinctions are made to imply other lifeform features:

- e.g., reflecting thermal regime—Boreal, cool or warm temperate, subtropical, and tropical

Hence,

- Temperate Winter-Deciduous Broadleaf Forest
- Subtropical Mixed Drought-Deciduous/Evergreen Microphyllous Shrubland
- Tropical Rain-Evergreen Broadleaf Forest

Often, these names are shortened because certain aspects are implied: e.g., “Temperate Deciduous Forest” and “Subtropical Desert.” However, be careful with what is implied—are all Boreal Conifer Forests evergreen? Are all Subtropical Deserts shrublands?

### Your Assignment

Your assignment is to compare Walter climate diagrams for the similar biomes of the world and South America (Task A) and to evaluate these to understand why each biome typically has a given vegetation structure (Biological Spectrum) and distribution (Task B).

#### Task A—Climate Diagrams

1. Select several pairs climate stations from locations around the world in different biomes (with one member of the pair from South America) from global climatology databases either from CD or printed material. Download mean monthly temperature, monthly precipitation, and station location (lat/lon).
2. Load software for creating climate diagrams.
3. Plot data for each site using a Walter diagram.
4. Use data from a local site for making a Walter diagram
5. Post diagrams on class’s web site.

#### Task B—Climatic Controls over Biome-level Vegetation Structure

1. For each site, describe general vegetation structure at the biome level (lifeforms, plant functional types) and generate hypotheses relating vegetation structure to climatic controls.
2. Use climate diagrams posted by other students for sites in the same or neighboring biomes to support your analysis.
3. In conference with labmates, select one or two biomes to present.

#### Evaluation

1. Orally summarize your analyses for one or two biomes (5 min. max.).
2. Participate in discussion of other students’ presentations. Based on your analyses for other stations, do you agree or have additional insights?

### Objectives

1. Better knowledge of major terrestrial biomes in terms of their features and distribution
2. Understanding of climatic controls over biome structure and distribution
3. Familiarity with climate diagrams
4. Introduce basic concepts of vegetation description

### Key Skills

1. Facility using and interpreting climate diagrams.
2. Dexterity with naming of terrestrial biomes and other major vegetation divisions.

### Timetable

1. Total elapsed time to perform the experiment: < half day.
2. Total elapsed hands-on time : 2.5 hours
   - Instructions = 10 min
   - Set-up (downloading data and climate diagram software) = 20 min
   - Tasks A and B analysis, and group discussions = 1 hr
   - Presentations and discussion = 1 hr

### Procedural Notes

Exercise is portable. Exercise is lab only, so not affected by inclement weather—unless power outages or surges require digital lab to be shutdown. In which case, discussion of climate diagrams and vegetation structure can proceed with hardcopy materials (reference books) and graph paper(!).

### Materials Needed

1. Lieth et al. CD ‘Climate Diagram World Atlas’—for climate diagram software and diagrams from other sites.
2. References for descriptions of biome vegetation and discussion of macroclimate controls over vegetation:
   - Wilson & Perlman CD “Conserving the Earth’s Biodiversity”
   - Walter “Vegetation of the Earth”
   - Barbour “Terrestrial Plant Ecology”
   - Hueck “As florestas de America do Sul”
3. Computer equipment
   - Computer
   - Printer—color printer preferred
   - Excel or some other data base