More Than One Limiting Nutrient - P and N Limitation
55
Constructing a Model Species Pair Capable of Coexistence: In Appendix Al
it is shown that the inequalities (Al.l), (Al.2), (Al.8) define the three
sufficient conditions for a stable coexistence of a pair of phytoplankton
species under certain N:P supply ratios. By examining Eqs. (AU), (Al.2),
(Al.8), we find that they can all be expressed in terms of ratios of uptake
affinities among the two species. This means that Eqs. (Al.1), (Al.2), (Al.8)
confine a triangular feasible region in the plane of relative P and N uptake
affinities (a'l'.lla'I'.1 and a'N./a'N.l)' as shown in Fig. 3.9.
3.-------------------~--------~
O~--------_+----------r_--------~
o
1
Relative P affinity
2
3
, / '
u p .2 Up,!
Fig. 3.9. Feasible region for coexistence (solid triangle) in terms of relative P and N uptake
affmities, as defmed by the inequalities Eqs. (Al.I)-(Al.2), (Al.8) (dashed lines). Solid circle
corresponds to the parameter combination given by Table 3.4