Seashore mallow (Kosteletzkya pentacarpos) as an ecosystem engineer: community dynamics and growth

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University of Delaware
Planning ahead for climate change is urgent and essential if we are to moderate its impacts. Salt marshes and coastal farmlands will be directly impacted by sea level rise, particularly through salt-water intrusion, increased storm surges and inundation. Planting the halophytic crop Kosteletzkya pentacarpos, seashore mallow, could extend the economic viability of salt-affected working land, while it is still dry enough to mechanically harvest, and simultaneously maximize the ecological potential of its eventual transition to salt-marsh. The purpose of this thesis is to study the eco-physiology of K. pentacarpos. Firstly, we examined its interactions with other halophytes and soil properties, and secondly, we investigated the role of temperature in its growth and development. We hypothesized that the presence of K. pentacarpos would facilitate the colonization of desirable marsh plants, such as Spartina patens, and assist in the evolution of soil conditions from working land to natural habitat. We examined these hypotheses through a multi-year field experiment. Communities initiated with K. pentacarpos were richer in species than those initiated directly with S. patens and more productive than control communities. The presence of K. pentacarpos enhanced the natural colonization of S. patens and Baccharis halimifolia. Although no effect of treatment was detected in major soil nutrients, an increase in organic matter and leaf litter was associated with K. pentacarpos treatments. Our results support the use of K. pentacarpos as a low-cost and efficient nurse crop in degraded agro-ecosystems. Temperature is suspected to play an important role in the life cycle of K. pentacarpos. To test this hypothesis, seeds from two locations within the species range, Delaware and Georgia, were grown at five temperature treatments from 15̊-35̊ C. Germination was not very temperature-sensitive but the development of secondary structures, such as leaves, occurred sooner at higher temperatures. Delaware seeds germinated sooner and seedlings grew larger than Georgia seedlings. These findings inform selection of optimum early growth conditions and reveal promising prospects for crop improvement, through the exploitation of trait variation found throughout the species’ spatial range.