Nursery pot size, not planting density, affects vegetation performance in a restored semi‐arid wetland
Kathryn M. Beheshti, Henry M. Page, Rachel S. Smith, Daniel C. Reed, Emily Blair, Andres Deza, Justin C. Hoesterey, David Huang, Russell Johnston, Morgan Tusa, Stephen C. SchroeterAbstract
Introduction
Coastal wetland restoration often involves planting nursery‐grown potted plants to accelerate vegetation development, particularly when stressful conditions or insufficient source material inhibit natural recruitment. Under these conditions, planting more densely or larger, more developed plants may increase vegetation survival and growth. Prior wetland studies suggest that planting densely ameliorates stressful conditions characteristic of the high marsh, which can facilitate the persistence and growth of plantings in the field.
Objectives
We tested the effects of density and size of nursery‐grown plants used to accelerate vegetation cover in a restored tidal marsh in southern California.
Methods
During a 6‐month period, we assessed the survivorship and growth of plantings and soil salinities at mid and high marsh elevations.
Results
In the high marsh, pot size, but not plant density, affected the growth of all species tested. Gains in growth were three times greater for large pots versus small pots. For the dominant marsh plant species ( Salicornia pacifica ), we found a marginally significant interaction between plant density and elevation on growth, which was 5% greater for high‐ versus low‐density plots in the high marsh. Clustering and using larger pots increased planting survival, though the relative importance of either varied by species. Hypersaline soil surface layers were, on average, 22 ppt higher in the high marsh than the mid marsh.
Conclusion
Overall, our results suggest that in a stressful, hypersaline environment, larger pot size—rather than higher planting density—was an effective strategy for increasing plant growth and accelerating vegetation development at the restoration site.