Transient population dynamics impede restoration and may promote ecosystem transformation after disturbance

Authors: SHRIVER, R - Us Geological Survey (USGS); ANDREWS, C - Us Geological Survey (USGS); ARKLE, R - Us Geological Survey (USGS); Barnard, David; DUNIWAY, M - Us Geological Survey (USGS); GERMINO, M - Us Geological Survey (USGS); PILLIOD, D - Us Geological Survey (USGS); PYKE, D - Us Geological Survey (USGS); WELTY, J - Us Geological Survey (USGS); BRADFORD, J - Us Geological Survey (USGS)

Submitted to: Ecology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2019
Publication Date: 6/17/2019
Citation: Shriver, R.K., Andrews, C.M., Arkle, R.S., Barnard, D.M., Duniway, M.C., Germino, M.J., Pilliod, D.S., Pyke, D.A., Welty, J.L., Bradford, J.B. 2019. Transient population dynamics impede restoration and may promote ecosystem transformation after disturbance. Ecology Letters. https://doi.org/10.1111/ele.13291.
DOI: https://doi.org/10.1111/ele.13291

Interpretive Summary: Disturbed ecosystems are increasingly prevalent and, despite great efforts to understand factors affecting ecosystem recovery from a restoration perspective, little is known about how vegetation populations recover. In this study, we used data collected from sites of sagebrush recovery across the Great Basin, USA and used statistical modeling approaches to approximate the trajectory of sagebrush population recovery after fire. Our models show that following disturbance and subsequent seeding treatments, sagebrush populations decline substantially before either recovering population growth or dieing off completely, each with variable impacts on future ecosystem functioning. Our findings suggest that sampling vegetation recovery in the first several years post disturbance may not reveal true trends in vegetation recovery and that better understanding of post-disturbance population recovery is needed to improve resource management.

Technical Abstract: The apparent failure of ecosystems to recover from increasingly widespread disturbance is a global concern. Despite growing focus on factors inhibiting resilience and restoration, we still know very little about how demographic and population processes influence recovery. Using inverse and forward demographic modeling of 531 post-fire sagebrush populations across the western US, we show that demographic processes during recovery from seeds do not initially lead to population growth but rather to years of population decline, low density, and risk of extirpation after disturbance and restoration, even at sites with potential to support long-term, stable populations. Changes in population structure, and resulting transient population dynamics, lead to a >50% decline in population growth rate after disturbance and significant reductions in population density. Our results indicate that demographic processes influence the recovery of ecosystems from disturbance and that demographic analysis can be used by resource managers to anticipate ecological transformation risk.