Desert Plant Diversity



Students will be able to identify patterns in plant distribution and diversity in the Sonoran desert ecosystem. They should be encouraged to develop ideas about why these patterns exist. Students will learn to use a vegetation key to identify desert plants.



Tool for defining plot size:pole w/ string attached, meter sticks, measuring tape, flagging.

Map of area to be sampled (if available)

Data Sheet (clipboard)

Plant identification books

Visually inspect the site. How many different plant species do you see? Select at least two sites to sample; these should have different kinds of vegetation so you can compare them. For example, you may want to do a north-facing slope vs. a south-facing slope.

1) Sample the vegetation with a transect line.

The transect should go in a straight line of approximately 100 meters; however along streamsides follow the course of the streambed. After establishing the line, plot 5 sub-plots off of this line. Follow instructions in “Study Site Selection” protocol.

The sub-plots off of the transect line should consist of 5 circular or square plots 20 m apart. Each circular plot should have a radius of 5.6m (so the area of each circle is 100m2). If you don’t have room to do 5 plots, you can do less but be sure to record this on the data sheet.

To find the starting point of the transect line pick up a rock and throw it over your shoulder, start the line wherever the rock falls.

Attempt to remain within your identified vegetation type. For example, if your transect is on a slope go along the slope (sideways on the hill), rather than up and down.

2)Identify and count how many trees, shrubs and cacti (don’t count the annual plants) are in each of the circles and record on your data sheet.

3)Don’t count the same plant twice

4)Don’t count dead plants—be careful to distinguish between dead and dormant plants (many desert plants loose their leaves in the summer and appear dead; they aren’t and will have green in the stems when broken).

5) You may want to conduct this study as a comparison with another site, or as a long term study of the same site.



1) Which plant is the most common in each of the plots? (Can you use math to figure this out?)

2) Are some plants found in all the plots?

3) Are some plants found in only a few plots?

4) Which plots had the most plants (total number)?

5) Which plots had the highest number of plant species richness?

6) List possible differences between the plots (more water, north slope, south slope, desert wash).

7) Is there a link between environmental factors and the number or kind of plants?

8) Did you notice any animal signs in any of the plots?

Desert Vegetation Data Sheet

 Location (name of park, closest cross streets, etc.)


Date:______________________ Survey Site No. ________________Survey Team                                             


Number of circular plots on transect line_________________________________

Distance between each circular plot:____________________________________

Survey Site Description (approximate location, GPS coordinates):

Circle No. 

Plant Name (common name, scientific name)