One way that ecologists characterize an ecosystem is through a transect: a path along which occurrences of a species, or abiotic features of an ecosystem, are measured. The figure below illustrates a transect across a sand dune ecosystem.
B
In this transect, soil was analyzed at sites A. B. and C. The results are shown in the table below.
Sampling site along transect
A
B
C
% humus
0.3
5.4 16.2
(dead plant material)
Nitrate concentration 27.6 63.8 165.6
(parts per million)
Number of soil bacteria 158.4 241.7 783.6
per gram of soil (10%)
a) Describe the difference in the percentage of humus at sites A and C. Explain the causes of this difference.
b) Use the data in the table to describe the difference in nitrate concentration between sites A and C. Explain the causes of this
difference.
c) An ecology student predicted that ar sites A and B legumes will grow better than non-legumes. Explain how the results
support this prediction.