Holdaway, Bailey; Emily, Martin; Kettenring, Karin (Utah State University)
Faculty Advisor: Kettenring, Karin (S.J. & Jessie E. Quinney College of Natural Resources, Watershed Sciences Department);
Seeds are the primary revegetation method for Great Salt Lake wetlands, however, the density and the priority timing to sow seeds are not clear to wetland managers due to a lack of Great Salt Lake specific revegetation research. Having too low a native seed sowing density could allow unwanted species like the non-native invasive plant Phragmites to reinvade. Too high of a density and density-dependent mortality of sown native seeds could occur, resulting in wasted seeds and unneeded costs for resource-limited managers. In addition, the priority timing (i.e., the relative time and order that seeds are sown) of sowing is also vital for revegetation to favor natives over unwanted invasives. Therefore, our research goal was to determine the optimal seed sowing density and timing priority for reestablishing Great Salt Lake native wetland plant communities. We conducted an outdoor mesocosm experiment with two native sowing densities (3 and 5x the standard sowing density in the region) and three native seed mix sowing timings (4, 2, or 0 weeks prior to sowing Phragmites seeds). We determined the cover of the native plant community and Phragmites at the end of the growing season across the 6 treatment combinations. We found the greatest reduction in Phragmites cover when the native seed mix was sown 4 weeks prior to Phragmites, particularly at the higher native sowing density. A 2-week priority effect did not significantly benefit native species over Phragmites. These results suggest that native seed mixes in Great Salt Lake wetland restorations need to sown much earlier in the summer growing season than when Phragmites seeds germinate and at a very high density to reduce Phragmites cover overall. Though, managers may need to greatly reduce Phragmites seed densities in the seed bank and in the vicinity of restoration sites before revegetation efforts begin.