Print PageTo what extent are seed maturation and hydrochory of riparian plant species coupled with timing of flood events? Some riparian plants show tight coupling between regeneration phenology and seasonal flood timing, but patterns have not been described for most taxa. Such knowledge is important for predicting recruitment bottlenecks for riparian species and community-wide responses to alterations of flow regimes. We recorded flowering and fruiting phenology monthly for one year for 103 riparian plant species in the riparian zone of the Verde River, a semiarid region river with a bimodal flood regime. Additionally, we seined hydrochores and measured flow rate at nine sites along the river, 12 times from April to September. Hydrochore identity and abundance were assessed in a greenhouse using the emergence method.
Results/Conclusions
Hydrochore species richness increased during all flood peaks, with the greatest increase during one of two seasonal maxima for seed maturation (July). However, individual species varied greatly in their seed maturation and hydrochory patterns. We identified three hydrochory strategies: 1) pulse species had viable seeds in the water in accordance with their short dispersal phenology; included in this group were Populus fremontii and Salix, both of which disperse and geminate during the short period of winter flood recession in the spring; 2) constant species had viable seeds in the water throughout the growing season and an extended period of seed dispersal from the mother plant; and 3) constant/pulse species had hydrochores present throughout the season (many of which presumably were prior-year seeds mobilized by flood pulses) but pulsed during their short periods of seed maturation. The phenological specialists with short-lived seeds (pulse species) are likely to be more sensitive to temporal flow alterations than are the many phenological generalists.
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