Evaluating short term simulations of a forest stand invaded by emerald ash borer

Abstract

The invasive emerald ash borer (Agrilus planipennis - EAB) is causing rapid and widespread ash (Fraxinus spp.) mortality in eastern North America, has established populations near Moscow, Russia, and is threatening ash resources in Europe. Given the prevalence of susceptible hosts these post-invasion forests will clearly differ from their pre-invasion counterparts. Understanding these changes is key to mitigating the impacts of invasion and developing sound management strategies. We evaluated short term changes in a forest stand invaded by EAB, and examined if the southern variant of the Forest Vegetation Simulator (FVS) could accurately predict those changes. Through simulation, managers can gain a clearer understanding of how pest invasions impact and alter future forest dynamics. However, many simulators are designed to achieve long-term predictions and thus do not align with the short term changes associated with rapid EAB-induced ash mortality. Woody vegetation was surveyed in 2010 and used to project impacts of EAB invasion into 2012 by simulating a 50% ash mortality rate. The same plots were then re-surveyed in 2012, allowing us to evaluate: (1) changes in actual forest composition and structure; and (2) simulation accuracy. Within our forest stand, FVS accurately estimated short term changes in stem density and basal area parameters, thus demonstrating its value as a short-term simulator for EAB-induced changes within the southern region of the United States. EAB-induced ash mortality is quickly changing these forests and will ultimately alter how stakeholders manage their lands. We discuss the potential usefulness of FVS as a tool for aiding management decisions in response to EAB invasion. Keywords: Ash, Forest Succession, Modeling, Forest Vegetation Simulator