9780521861724htl 1..2

predicting scaling exponents (Cyr & Walker, 2004 ). For our analysis, we selected

the recently formalized metabolic theory of Brownet al.(2004) as a framework

for posing testable predictions about the relationship between components of

production and body size. Their metabolic theory is grounded on the assump-

tion that processes driven by metabolism at all ecological scales are subject to

quarter-power scaling, and that individual metabolism scales as M0.75due to the

fractal-like architecture of internal distribution systems (Woodwardet al.,

2005a). For our test of selected predictions of this theory, we specifically focused

on several independent communities because factors constraining bioenergetic

relationships among animals should be most effectively expressed at the com-

munity scale (Cyr & Walker, 2004 ).

The results of our analysis indicate that the scaling exponents describing the

relationship between N, B, P/B and P for the communities of Ball Creek, Sutton

Stream and Stony Creek showed a high level of concordance with the predicted

quarter-power scaling relationships. Among the analyses of the different pro-

duction variables, the relationship between P/B and M (summed taxa) showed

the highest level of precision, with the scaling exponent varying from only

0.24 to0.27, which bracketed the predicted exponent (0.25), and with

0

1

2

3

4

5

0

1

2

3

4

5

log

10

annual P(mg/m

2 )

Ogeechee River

log 10 P = 4.83 – 0.37 log 10 M

(r^2 = 0.60, p < 0.02)

log 10 M (∝g)

Sutton Stream

log 10 P = 2.77 – 0.03 log 10 M

(r^2 = 0.00, p = 0.887)

Stony Creek

log 10 P = 3.09 – 0.13 log 10 M

(r^2 = 0.07, p = 0.556)

Ball Creek

log 10 P = 2.94 – 0.02 log 10 M

(r^2 = 0.03, p = 0.705)

01234567 01234567

0

1

2

3

4

5

0

1

2

3

4

5

01234567 01234567

Figure 4.6Log-log plots of annual

P(P¼mg m^2 yr^1 ) against M (mg/

individual) for four stream

communities (see Fig.4.2for

details). The grey line indicates the

predicted slope of the relationship

between log 10 Pandlog 10 M

(P/M^0 ). The black line indicates

the slope derived from least-

squares regression of the data.

64 A. D. HURYN AND A. C. BENKE