1 Life history theory predicts that reproduction incurs costs in terms of f
uture growth and survival. In infertile environments reproductive events ma
y accelerate nutrient turnover such that losses of limiting nutrients canno
t be replenished by uptake from the soil.
2 We compared the effect of reproduction on nitrogen (N) turnover and N use
-efficiency, i.e. the annual dry matter produced per unit N lost, of three
carnivorous species of the genus Pinguicula on an infertile subarctic heath
. We hypothesized that reproduction should increase N turnover, unless a la
rger N pool or improved N resorption can compensate for the losses associat
ed with reproduction.
3 These carnivorous herbs showed a nitrogen use strategy similar to that of
non-carnivorous plants (herbs and grasses) with a relatively low mean resi
dence time (MRT) of N and a large dry matter productivity per unit N in the
plant (annual N productivity). N pool size and the efficiency of N resorpt
ion from senescent leaves were similar in reproductive and non-reproductive
individuals. Reproductive individuals had significantly larger annual N lo
sses and thus a lower average MRT (0.8 vs. 1.8 years), with values < 1 indi
cating that the annual N losses are greater than the annual average N pool.
Unless plants can enhance their nutrient acquisition, flowering may theref
ore impact on future growth and survival.
4 This study presents evidence for a direct link between reproduction, refl
ected in a higher relative allocation to inflorescences, turnover and N use
-efficiency; the latter being reduced because of increased N turnover. The
ranking of species in terms of reproductive allocation was the reverse of t
heir ranking in terms of their N use-efficiency.