Under exponential growth, if r > 0:
In the exponential model dN/dt = rN, population size N is positive, so the sign of dN/dt is determined by r. When r exceeds zero, the instantaneous change is positive and abundance increases according to Nt = N0e^(rt). A larger r produces more rapid proportional growth and a shorter doubling time. If r equals zero, e^(rt) equals one and abundance remains constant; if r is negative, the exponential factor declines with time. This interpretation assumes that r summarizes the net per-capita effects included in the model, commonly births minus deaths in a closed population. Immigration and emigrat
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 11
