9780521861724htl 1..2

between M and N, and M and P/B, using individual taxa rather than size classes.

The purpose of this analysis was to assess the variability of the relationship

between M and N, and M and P/B within independent communities.

Scaling coefficients for log 10 N, B, P and P/B versus log 10 M were obtained from

least-squares linear-regression models. Predicted scaling exponents were

assumed to be statistically indistinguishable from observed exponents when

they fell within two standard errors (SE) of the latter.

Results

The scaling exponents for N versus M (taxa summed within size classes) ranged

from0.99 to0.59 (Fig.4.2). All regressions were significant (p<0.05). The

scaling exponents were negative and within one (Ball Creek, Sutton Stream,

Stony Creek) or two SE of the predicted exponent of0.75 (Fig.4.3).

The scaling exponents for B versus M (summed taxa) ranged from 0.13 to 0.29

(Fig.4.4). Only the regression for Ball Creek was significant, however (p<0.04).

Nevertheless, the relationship between B and M was similar for all streams, with

positive exponents that were within one SE of the predicted exponent of 0.25

(Fig.4.3).

0

1

2

3

4

5

0

1

2

3

4

5

log

N (individuals/m 10

2 )

Ogeechee River

log 10 N = 5.35 – 0.99 log 10 M

(r^2 = 0.88, p < 0.001)

Sutton Stream

log 10 N = 3.91 – 0.59 log 10 M

(r^2 = 0.62, p < 0.04)

log 10 M (∝g)

Stony Creek

log 10 N = 4.68 – 0.91 log 10 M

(r^2 = 0.78, p < 0.01)

Ball Creek

log 10 N = 4.52 – 0.76 log 10 M

(r^2 = 0.95, p < 0.001)

01234567

0

1

2

3

4

5

0

1

2

3

4

5

01234567

0 1234567 01234567

Figure 4.2Log-log plots of

population density

(N¼individuals/m^2 ) against M

(summed taxa,mg/individual) for

the snag-community of the

Ogeechee River and benthic

communities of Ball Creek,

Sutton Stream and Stony Creek.

The largest body-size class for Ball

Creek is occupied by crayfish. The

largest body-size classes for the

latter two streams are occupied

by invertivorous fishes. The grey

line indicates the predicted slope

of the relationship between

log 10 N and log 10 M(N/M0.75).

The black line indicates the slope

derived from least-squares

regression of the data.

60 A. D. HURYN AND A. C. BENKE