Biosphere 2 Center

Exercise 2: Measuring Biodiversity
Module 2: Introduction to Local Biomes

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Your Questions

1. What are the characteristic species assemblages of the U.S. Southwestern Desert ecosystem? 
2. How can local biodiversity be measured? 
3. How does biodiversity vary with sample domain size (scale)? 
4. How does the community structure and climate of these deserts compare with those of the other SEE-U sites?
5. How are Global Positioning Systems (GPS) and Geographic Information Systems (GIS) incorporated into current field ecology and conservation biology? What value are they?

Background

The Local Biome: North American Subtropical Desert Biome

The Biosphere2 Center (B2C) sits in the northern reaches of the Sonoran Desert, a section of the North American Subtropical Desert Biome. The North American (NA) Subtropical Deserts span the continent from the Pacific Ocean to the Gulf of Mexico, and from northern Mexico through the American Southwest (from southern California to southern Texas). The subtropical deserts, along with the cooler Temperate Desert Shrublands of Nevada and Utah, form the bulk of arid shrublands in the United States and on the continent.

The Sonoran

The landscape around Biosphere2 illustrates the biological diversity of the Sonoran Desert, one of the richest ecosystems within the American subtropical desert biome. It is a desert preserve of roughly 100 hectares (250 acres) dominated by widely-spaced small-leafed shrubs and interspersed stem succulents (cacti) varying in stature from ground-sessile pincushion cacti to erect, branching chollas to towering saguaros.

Drainages across the landscape are often dry, but concentrate subsurface moisture that supports riparian vegetation. Diversity in vegetation provided by such landscape heterogeneity provides a range of habitats for insect, mammal, and bird life. Views from B2C show the proximity of desert ranges with other, more mesic (forested) environments, which add to landscape and biological diversity at the regional level.

This lab aims to demonstrate the types of communities and species found within the Sonoran, and orient students to B2C. 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 Sonoran Desert.

GPS

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 (in our case, Trimble’s Pathfinder system) 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 using the Trimble GeoExplorer 3 GPS units.

GPS will be used during this class to determine the precise latitude and longitude of all field sites so that when we enter the data into the central repository (eBiome), we can georeference 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.

Your Assignment — and Timetable

• Task A: Orienteering — Use of map, compass, and GPS as tools for field ecology. Focus on learning the basics of GPS technology. 
• Task B: Measuring Local Biodiversity — Assessment of site biodiversity using species area curves: field data collection and analysis. Use of eBiome for data entry, display, and analysis.
• Task C: Climates of the Sonoran — Compare climates across the Sonoran Desert and with other Subtropical deserts of North America and the world
• Task D: Regional Biodiversity — Use of maps and reference books to gain understanding of regional differences in biodiversity across the Sonoran and the North American Subtropical Desert Biome (Optional)
• Task E: Cross-site Analysis — After sharing your local Task B and C results with the other sites, compare and contrast the climates and communities of the biomes represented by the SEE-U sites. 

Task A: Orienteering and Familiarity with Sonoran Plant Communities (Sunday and Monday, late afternoons)

1. Use existing trail network to become acquainted with the B2C site—its plant communities and dominant species. (Sunday orientation day, late afternoon) 
2. In groups, learn use of map and compass in orienteering, including estimating distance with your own pace.  Follow orienteering course. (Monday, late afternoon) 
3. After this, or at the same time, locate and travel to specific areas of interest (e.g., different hillslope positions on the landscape) using maps, compass, and GPS.  Focus on your map reading skills without use of GPS, then progress to using GPS. (Monday, late afternoon)

Task B: Measuring Local Biodiversity and the Importance of Spatial Scale (Day 1, Tuesday)

1. Beginning early Day 1, return to one of Task A’s points of interest. Census the make-up of the community at several different spatial scales and using several censusing techniques to gauge plant (shrub and arboreal stories) and arthropod diversity. (Day 1, early morning start) 
• Step 1. Measure out a 4m² (2x2m) plot of desert terrain. Count and record the number of plant species (focus on overstory plants, including cacti) and arthropod species (species can be catalogued based on order and/or morphotypes) contained within this plot. 
• Consider: In addition to number of individuals, what other measurements or characteristics could be recorded? 
• Consider: What other types of scales would be important to consider when measuring biodiversity? 
• Step 2. Scale up your plot size by doubling its area.  Repeat your recording of individuals as well as any other measurements you are considering.
• Consider: What type of habitat does your plot cover? — Dry ridgeline? Drainage bottom? Shaded slope? 
• Step 3. Repeat step 2 several (e.g., 3) more times, successively doubling plot area (e.g. to 256 m²,16x16m).  Again, consider additional measurements and descriptors of your plot. 
• Step 4. Return to lab. Bring plant and arthropod specimens to be identified. 
• Consider: How would your sampling techniques be affected in different biomes? 
2. Return to the lab to analyze, write-up, and discuss your results (end of Day 1). 
• Enter data into eBiome. 
• Use eBiome to facilitate analysis.
3. Upload results files to server for use by other sites in Task E (end of Day 1).

Task C: Climates of the Sonoran (Day 1)

1. Compare and contrast climates (e.g, with climate diagrams) and corresponding vegetation of different regions of the Sonoran Desert and with other Subtropical Deserts in North America and the world.  (Day 1)
2. Upload results files to server for use by other sites in Task E (end of Day 1).

Task D: Regional Biodiversity (Day 2) (Optional)

1. Compile a species list for shrub and arboreal plants for the B2C site based on classes field work in Task B. Keep organized by habitat type (hilltop, riparian, etc.). 
2. Compare and contrast this compilation with those from sites across the Sonoran and other divisions of the NA Subtropical Desert Biome. Is there a strong overlap among communities from different regions of the Sonoran and of the NA Subtropical Desert biome? Or do the regions have distinct vegetation? What difference does site habitat make on this comparison? 
3. Use statistical tests to evaluate consistency. (Optional) 
4. Refer to maps, other source materials, and climate diagrams to further evaluate vegetation and climatic differences for divisions within the North American Subtropical Desert Biome and within the Sonoran. 
5. In conference with labmates, select results from one or two regional comparisons to present. Present summary of these regional divisions, along with presentation for Task B.

Task E: Cross-site Analysis (Day 2)

1. Download Task B and C results from other SEE-U sites.
2. Compare sites — 
• Compare and contrast the climates and communities of the biomes.  Analyze, discuss, and present results.
• Discuss results with students at the other sites — Were outcomes different? Why do you and they think that was so?

Resources:

1. Brown, “Biotic communities of the American Southwest”—book and map 
2. Rondeau et al., “Annotated Flora and Vegetation of the Tucson Mountains” 
3. Larson, “The Deserts of the Southwest” (Sierra Club Books)
4. Jaeger, “The North American Deserts” 
5. Barbour and Billings, “Vegetation of North America”—Chapter on Warm Deserts.
6. Man and the Biosphere (MAB), “Map of the World Distribution of Arid Regions” — map and text.
7. Walter “Vegetation of the Earth” 
8. Bailey “Ecosystem Geography” and US/North American maps.
9. Lieth et al. “CD Climate Diagram World Atlas” —  climate diagram software
10. The Nature Conservancy (TNC) and state heritage programs—written reports of plant community composition (optional task). 
11. Statistical software for plant community consistency. (optional task)

1. Oral presentation to share with class local biodiversity field results (Tasks B) and regional climate and (optional) biodiversity analysis (Tasks C and D) (10 min/group max.) 
2. Participation in discussion of other students’ presentations. Based on your analyses for other sites, do you agree or have additional insights?

Key Skills

1. Gain familiarity and confidence with the local ecosystem 
2. Understanding of field safety 
3. Familiarity with basic orienteering techniques 
4. Ability to conduct thorough ecological observations and collect data in the field. 
5. Identification of key floral and faunal species. 
6. Knowledge of the importance of scale.

Procedural Notes

1. Appropriate field gear (hat, sunscreen, bug spray, food, water) are needed for extended stay in desert terrain. 
2. Students should be scattered about a diversity of habitats — instructors will choose the general types ahead of time (ridge top, slopes, drainage, etc.). All locations should be grouped together and there should be at least one instructor or TA very nearby.

Materials Needed

1. Field notebook and writing instruments 
2. Appropriate field gear (hat, sunscreen, bug spray, food, water) 
3. Tape measures (at least 50 to 100 m tapes) 
4. Plot frames (e.g., 1x1 or 2x2  m)
5. Compasses 
6. GPS units 
7. Topographic maps — USGS maps and maps printed out from eBiome
8. Plant and arthropod collecting tools (bags, vials, presses, knives, tags) 
9. Plant and arthropod field identification handouts/guides