Summer in Tucson
During my summer vacations from a Tucson, Arizona high school, close to high noon I go outside to the Sonoran Desert and map and photograph soil crusts. My brother tells me this is why I am so, you know, dippy. Even though its very hot outside then, the light is good for seeing the crusts. If you can't understand the logic behind anything in these lessons, just remember its source. Sometimes I take a painful approach to get to some ephemeral point. "The light is better."

This is a guide for the teaching of ecology in a high school classroom. It is designed after research I have done on the ecology of soil lichen in the Tucson Basin area during the summers of 1997 and 1998. Its purpose is to guide students into adopting the problem solving thinking of ecologists.

Little things matter
The overriding focus is on the tiny unobtrusive organisms that so often exist in the middle of a place's ecology. Really, the main objective is for you and your charges to give credit to the little things. We all know it is the little things that matter.

Ecology Unit
The lesson could be considered the entire ecology unit: it encompasses all the concepts of interactions between organisms and their environment. If you aren't lucky enough to live in the Sonoran Desert, just spend a little time looking very closely at the ground or on rocks or trees. You will find the organisms that are just beyond the tunnel vision of society, yet of panoramic proportions in ecology.

There is "my" logic behind the order of the activities. One activity develops the skills of ecologists; students will construct their own knowledge of an area. This will be used for the next lesson. Making maps of plants becomes a focus for a couple day lesson. These maps will then be digitized and analyzed using NIH Image on the Macintosh computers. This assists the students in turning observations into a numerical format that can be quantified and analyzed.

The end of the lesson could be an extended inquiry into succession of communities. This could be done by comparing the organisms from different replicates of a given area. Identifying invasive, transition and climax communities would be the main objective.

Plant Identification
Without a passing knowledge of the diversity of an area, ecology is meaningless. Dick Barber's Field Book is a great template. The ability to identify the perennials of the area, Acacia, Larrea tridentata, Ambrosia deltoides, Prosopis ssp., Opuntia ssp., and Cercidium would be essential. Also being able to identify the differences between perennials and annuals would be helpful because of the nature of nutrient recycling. A plant identification book could be made by bringing in clippings of native plants and have the students paste them into their own little booklet along with a brief comment as to its importance in the desert ecology. Completion of the booklet as well as the comments could be the assessment.

Once these organisms are identified, then a closer observation of the way they congregate becomes apparent. For example, foothills paloverde thrives in very coarse soil with large boulders, while blue paloverde is usually found in deep sandy soils. Creosote grow poorly around caliche and heavy clay soils. These trees above ground tell what is below ground. Very few things grow under the canopy of the mesquite tree because of its thick litter.

Soil Analysis
Analyzing the soil taken from plots is a fun activity that incorporates movement, mud, measuring, and (ugh!) mathematics. Sometimes it is possible to discern a difference between soils with crust on them and soils without crust on them using the sieve method. This uses a stack of four sieves with different sized grating and the weights of each grate's particles is weighted and divided into the total, giving a percentage of the total. Completion of this activity would be the assessment.

Bouyoucous Method
If the class hasn't totally burned out, then the Bouyoucous method of soil analysis could be taught which gives an extremely accurate percentage of gravel, silt and clay. It is for a class that is interested in actually doing research. But this method takes a full 120 minutes and has much down time between readings.

Concept Maps
The last lesson would be to go back to our concept maps and transects and to see if there is a relationship between the plants above ground and the lichen on the ground. Typically, there are few lichen colonies where the land is disturbed. Also, there are several bush species (Burroweed, burrow bush) that indicate the land has been disturbed within the past six years. Ambroisia deltoides is a bush that is very long lived, as indicated by retaking old photographs. It has been shown that the same bush can live fifty years or more. This, along with creosote, which has been estimated to live for 11,000 years, are typically associated with soil lichen, whereas Burroweed is not.

Typically.

With the original small groups, ask them to think of what would influence the growth of soil lichen. Make a master list from all unique ideas and have the groups create a concept map. Assess the concept map on the number of concepts, the cross connections, coherence of ideas and the logic of the hierarchy.

Rubric for Concept Maps