PS 34-238 - Growth and Fungal Root Colonization in Three Beach Adapted Plants on a Novel Substrate

Abstract: Background/Question/Methods

Coastal restoration efforts use beach adapted vegetation as a sustainable and effective ground stabilization method to reduce erosion from wave action or large storm systems. Other restoration efforts include dredging sand from offshore to restore washed out or eroded sand banks. However, sand dredging can undermine restoration efforts by increasing erosion, decreasing substrate stability, and can destroy habitat for local flora and fauna. Efforts from Glass Half Full NOLA, a New Orleans based glass recycling company, have brought a novel alternative through processing glass into glass sand. This process is far removed from the soil and is assumed to contain no growth-promoting fungi or bacteria. Thus we expect plants used in restoration to perform worse in glass sand than in natural environments, threatening restored coastal buffer zones through slow growing or weakened plants. To test this, we compared plant growth and root colonization in treatments of pure glass sand (GS), glass sand/beach sand mix (80/20) (GSM), glass sand/sterile beach sand mix (80/20) (GSSM), and beach sand (RS). Each treatment was split into a fertilized or unfertilized group, yielding eight treatments in total. Beach sand was obtained from Dauphin Island, Alabama, and was autoclaved in the sterile mixes. Commercial plugs of three plant species common in beach restorations were used: two beach morning glories (railroad-vine, Ipomoea pes-caprae; beach morning glory, Ipomoea imperati) and sea oats, Uniola paniculata.



Results/Conclusions

All three species grew fastest in RS, slowest in GS, and had intermediate growth in GSM and GSSM. These results support our hypothesis that growth-promoting soil microbiota are lacking in glass sand. We also expected less growth from GSSM versus GSM. This was observed in both morning glory species although the difference was only seen between the fertilized mixtures. For sea oats, growth in GSSM was better than in GSM, regardless of fertilization status. Fertilization might accentuate the disparity between sterile and non-sterile substrates, and the holdover root microbiota community from the initial transplant plug may confound results given that residual microbes may be more difficult to control in transplants not grown from seed. Realistic outcomes of glass sand restoration will most closely resemble the results from GSM. These results support the practice of using GSM rather than pure GS in restoration efforts where plant growth for erosion control is important.