Every restoration is unique: Testing priority effects, year effects, and site effects as determinants of initial restoration trajectories
Restoration practitioners are increasingly aware that their projects may yield variable outcomes. Many of these may be attributable to variation in initial management (e.g., differences in weed control, seed mixes, planting order), while others may be due to site effects and year effects, even if site preparation and installation are identical. Two questions arise: 1) How important are year effects and site effects for generating different initial restoration outcomes? 2) Do these differences maintain themselves in the longer term, or do these plant communities converge? We examined the how year effects and site effects interact with temporal priority in restoration by installing otherwise identical restoration-style plantings across three geographic sites and four planting years.
In addition to confirming the power of priority effects in restoration, initial results demonstrate strong temporal and spatial differences in the outcome of these restoration experiments that are generally maintained at least through the initial years of their implementation. There is some evidence of parallels in year effects and site effects. We discuss the implications of these results for ecological experiments in general, restoration planning, and assisted migration in light of climate change projections.