Reciprocal transport between ramets increases growth of Fragaria chiloensis when light and nitrogen occur in separate patches but only if patches are rich

Summary

Fragaria chiloensis is a stoloniferous perennial herb that grows on coastal sand dunes where scattered shrubs create small patches of lower photon flux density (PFD) but higher soil nitrogen availability. The potential effects of resource transport between ramets when PFD and soil nitrogen are negatively associated in space were tested by comparing the growth of pairs of ramets in which the vascular connection between ramets was either severed or left intact. One ramet in each pair was given high PFD but a low level of soil nitrogen and the other ramet was given low PFD but high N. The analogous effects of resource transport likely to be realized in nature were tested by substituting a more realistic medium soil nitrogen level in place of the high level. Results suggested that connected ramets exchanged carbon and nitrogen under both regimes of soil nitrogen heterogeneity. In the low versus high nitrogen regime, connected ramets had higher combined dry biomass and different patterns of dry mass partitioning from those of severed ramets; effect of connection was greater on ramets given low PFD and high N and on younger ramets. In the low versus medium nitrogen regime, connected ramets had different patterns of partitioning only. Apparent reciprocal resource transport between ramets can enhance the growth of ramets with complementary resource deficiencies, but may affect growth in dry mass only when maximum resource levels are high.