Investigating facilitative interactions of native marsh plants under elevated salinity stress

Saltwater intrusion (SWI) is becoming increasingly common and affects many coastal ecosystems, resulting in extirpation and replacement of ill-adapted species by more salt-tolerant species. Plants like wild rice (Zizania aquatica), which grows in tidal, freshwater marshes of the Chesapeake Bay, are especially vulnerable to decline and replacement from SWI. However, under increased salinity stress, having close neighbors can sometimes be more beneficial than growing alone. To test if species interactions become more positive (i.e. facilitative v. competitive) under elevated stress, I manipulated salinity and plant neighbor presence of two marsh plants, Z. aquatica and Schoenoplectus pungens in a fully crossed mesocosm study. Surprisingly, salinity had little effect on wild rice health, but when Z. aquatica was grown with neighbors, competition declines and even resulted in interspecific facilitation. This indicates that wild rice may generally benefit from having neighbors, providing meaningful insight into conservation and restoration management strategies of these valuable ecosystems.