Contrasting soil seed-bank dynamics in relation to local recruitment modesin two clonal shrubs, Rhus aromatica Ait. and R. glabra L. (Anacardiaceae)

Soil seed bank dynamics, greenhouse seed germination and field seedling sur vival were compared in the weakly-clonal shrub Rhus aromatica Ait. and the strongly clonal shrub R glabra L. (Anacardiaceae). Although both species ha d persistent soil seed banks, their sizes and dynamics differed greatly. Th e high seed density (5668 +/- 1267 m(-2) to 8739 +/- 3303 m(-2)) in R glabr a was depleted by ca, 5% annually and replenished with 1102 +/- 316 to 1828 +/- 486 seeds m(-2), whereas the low seed density (9 +/- 5 to 138 +/- 68 m (-2)) in R aromatica was depleted by ca. 50% annually and replenished with 37 +/- 7 to 69 +/- 18 seeds m-2. Seeds of both species germinated within es tablished populations. However, recruitment from seedlings was successful i n It aromatica but not in R glabra, which depended exclusively on root suck ering for aboveground population increase. This difference in local recruit ment modes between the two species was correlated with differences in soil seed bank dynamics and other life history traits, such as fecundity, seed w eight, seed dormancy seed dispersal, seedling establishment and growth form . The results of this study have important implications about life history evolution in that they suggest that various traits related to increasing se xual reproduction in time and space evolved in concert with clonal reproduc tion in clonal woody species.