In response to increasing wildfire severity and extent across the dry forests of the western United States in the last several decades, federal policy initiatives have encouraged joint vegetation management and fuels treatments to restore ecosystem composition, structure and function and reduce the potential for extreme fire behavior. While fuels reduction treatments traditionally focus on reducing potential fire behavior recently treatments have also included specific objectives to create structurally complex residual forests. However, there are few scientific studies that have either simulated or directly evaluated the influence of spatial complexity on potential fire behavior and many of the simulation tools that are commonly used to asses treatment effectiveness assume that a homogenous fuels complex exists and are thus not necessarily useful in assisting managers whom need to weigh the effects of creating structural complexity on future fire behavior. Given the large number of acres undergoing treatments where there are simultaneous objectives of altering spatial complexity and future fire behavior, there is an urgent need to understand the relative influence of spatial complexity on potential fire behavior and to provide decision-makers with improved knowledge to simultaneously achieve a specified desired range of future fire behavior and stand heterogeneity. Our objective in this proposal is to investigate the effect of ecosystem restoration treatments on spatial complexity and the resulting range of future fire behavior. The expected benefits at the completion of this project are: 1) greater understanding of the effectiveness of joint vegetation management and fuels treatments to restore ecosystem composition structure and function; 2) improved guidelines and methods of how to measure, quantify and describe spatial complexity; 3) improved understanding of the effect of fuels reduction treatments and ecological restoration treatments on spatial variability of surface and canopy fuels; 4) improved understanding of potential errors in terms of predicted fire behavior introduced by variations from a homogeneous fuels complex; and 5) improved guidance on how to identify and weigh the potential effects of spatial complexity in the design of ecological restoration and fuel hazard reduction treatments. To quantify changes in spatial pattern and future fire behavior we will collect pre- and post-treatment fuels data on a 18 four-hectare plots randomly located inside treatment boundaries using a factorial design with two levels of residual basal area (40 and 80 ft2 ac-1) and three categories of residual forest structure and three replicates. Specifically, we will focus on the three important forest structures identified by Larson and Churchill (2012): homogeneous widely spaced single trees (as an outcome of traditional fuels reduction treatments), spatially heterogeneous spatial patterns with a single tree size class in each group and, spatially heterogeneous spatial patterns with a mix of tree size classes within each group (both resulting from ecological restoration treatments). Spatially explicit pre- and post-treatment field measurements will be collected using terrestrial LiDAR scanning (TLS), common fuels inventory methods. Spatial complexity will be estimated using a variety of standard approaches (McElhinny et al. 2005, Larson and Churchill 2012) and changes between pre- and post-treatment spatial complexity will be quantified. Each study site will be modeled using both WFDS and FFE-FVS; and the potential fire behavior will be simulated across a range of wind speeds and fuel moisture scenarios to evaluate the role of spatial complexity in determining treatment effectiveness. The findings from the proposed study will provide forest managers with the knowledge and tools they need to weigh the potential effects of structural complexity on simultaneously meeting ecological restoration and fuels hazard reduction objectives.