stages of species colonization within that system. This biomass invariance
denotes that, in species-rich communities, a finer division of biomass and,
therefore, resource partitioning must occur rather than an increase in commun-
ity biomass. These results are similar to those obtained in tree-dominated
communities, where biomass and energy use was constant across species of a
single trophic level (Enquist & Niklas, 2001 ).Total number of species,StotTotal biomass,Btot(g DM m–2)10 –610 –510 –410 –310 –210 –1100101102103104105106107108109Total density,Ntot(ind m–2)10 –610 –510 –410 –310 –210 –1100101102103104105106107108109SB
LL
MYBtot = 0.501 + 0.003StotNtot = 8.892 × 103 Stot1.0640 50 100 150 200Figure 8.2Total densities and biomass per 1 m^2 as a function of the number of species per
1m^2 across stream communities (Seebach (SB), Llwch (LL) and Mynach (MY)). Regression
of log-transformed density on log-transformed number of species givesr^2 ¼0.254,
F1,866¼294.91,P<0.001. Regression of untransformed data for total biomass per 1 m^2
against number of species givesr^2 ¼0.015,F1,866¼13.53,P¼0.001. Regression equations
are given in Table8.2.Table 8.1Estimated predictions of the relationship between sampled area size (A) and the
ordinary least-square slope (bA – OLS) of linear regressions of log population density on log
body-mass based on the exponential decay function:bA – OLS¼aþbe(A/c)for stream
communities (Seebach (SB), Llwch (LL), Mynach (MY)). a, b, c are the regression
coefficients; confidence limits (95%) are given in parentheses;r^2 is the variance explained; n
is the number of random amalgamations of the data (see details in text). ***P<0.001.
Streams abcr^2 n
SB 0.684 0.197 48.180 0.850 104
(0.685,0.683) (0.195, 0.198) (47.098, 49.261)
LL 0.496 0.062 78.348 0.255 104
(0.500,0.493) (0.059, 0.065) (68.350, 88.346)
MY 0.723 0.363 22.684 0.890*** 104
(0.724,0.722) (0.350, 0.356) (22.313, 23.056)
BODY SIZE AND SCALE INVARIANCE 147