CHARACTERIZATION OF TERRESTRIAL ECOSYSTEMS

The objective of these two laboratory sessions will be to analyze several environments which represent stages in a mesic sere. We will study an abandoned 'old' field, a transitional young forest, and a climax old forest. As we study these sites you will become familiar with plants and animals typically found in several habitats found in central Maine. You will also learn several quantitative techniques used by ecologists.

As you study each site, there are several things which you should look for. These include:

1. stratification layers (how many and the types of plants in each layer);
   
2. vegetational structure of stand (what type of organisms are found and what is the quantity in various size classes?);
   
3. animal signs (trails, burrows, tracks, etc.);
   
4. the nature of abiotic factors (Will the present conditions bring about biotic changes? What is the cause of the biotic differences found among sites?).

   

Some of the vegetational analysis will be done using quadrats, rectangular areas of predetermined sizes, which will be laid out in a random fashion within the area to be studied. We will use two sizes of quadrats to analyze large and small plants. The trees and large shrubs will be quantified using quadrats measuring either 2 x 10 meters or 4 x10 meters. Each group (4 students) will be responsible for characterizing tree size and abiotic parameters for one quadrat of this size. Inside the four corners of each large quadrat, four 1x1/2 meter quadrats will be placed to study vegetative cover.

PROCEDURE:

1. The large quadrats will have been strung off ahead of time. The instructors will assign a specific quadrat for each group to characterize.

2. Divide the responsibilities for data gathering among the group members for the following areas:
   
   1. Abiotic measurements listed on the data sheet. Note that because our equipment is limited, two groups will share equipment for measuring abiotic characteristics.
      
   2. Identify the species of trees in the large quadrat (if any), measure their DBH (diameter at breast height), and count how many of each species there are in each size class listed on the size class sheet.
      
   3. Identify the large shrubs (greater than 1 meter tall) and count the number of individuals in each species in the large quadrat.
      
   4. Place the small quadrat frame within each corner of the large quadrat. Record the species found in them and make a cover estimate (decide on one of the cover classes listed below) for each species.
      The cover classes we will use are those suggested by Braun-Blanquet:
      
      1. <1% (mid-point=0.5)4) 26-50% (mid-point=39)
         
      2. 1-5% (mid-point=3)5) 51-75% (mid-point=63)
         
      3. 6-25% (mid-point=16)6) 76-100% (mid-point=89)

      Enter into the table the midpoint value of which class the cover for a species falls in for each small quadrat. Use the mid points of the classes to develop an average for the four quadrats for each species and a total of all species for the quadrat.

3. Record your observations of animals seen and animal sign as well (e.g. tracks, burrows, trails).
   

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