Mechanical mastication is an increasingly common fuels management treatment in fire-prone forests and rangelands in the US. Mastication is commonly used in fuelbreaks and along the wildland-urban interface, often in lieu of prescribed fire or other mechanical treatments. By reducing vertical fuels to a compact woody fuelbed, mastication allows improved firefighter access for fire suppression and can make subsequent prescribed fires easier to implement. This proposal directly addresses a need for information regarding the effectiveness and longevity of fuels treatments as stated in the JFSP 2011 RFA 2012-1. In Task 3: Fuel Treatment Effectiveness, the JFSP solicits proposals that will aid land managers in the decision-making process with respect to treating fuels across landscapes. As indicated in the RFA many factors influence fuel treatment effectiveness including treatment type, intensity, size, frequency, season, age, and site. In this proposal we propose to investigate the effectiveness and longevity of mechanical mastication as a fuels treatment in fire-prone northern California and southwest Oregon. Our past experience with masticated fuels provides us with a unique opportunity to identify the effectiveness and longevity of mastication across varying pre-treatment vegetation types, using contrasting mechanical methods, and across a variety of site characteristics. The results generated in this study will enhance the information available to land mangers regarding the viability of masticating fuels across landscapes by evaluating Topic 1) how effective are mastication treatments for meeting fire behavior objectives? Topic 2) how long are mastication treatments effective for meeting fire behavior mitigation objectives? and Topic 3) what measures of fire behavior or ecosystem response are useful indicators of fuels treatment effectiveness? What we know about the effects of mastication pales in comparison to what we dont: 1) the effects of time since treatment on vegetation recovery (in this region, primarily shrub re-growth); 2) changes in fuelbed characteristics over time (bulk density, fuelbed depth, particle density); and 3) the fundamental effects of fuelbed aging on potential fire behavior. All three areas above play a role in treatment effectiveness the probability of modifying fire behavior and effects over the untreated condition. Providing useful metrics that rapidly assess how these fuels vary over time with respect to mitigating fire behavior will enable land managers to make more educated decisions about where and when to use mechanical mastication as a fuel treatment tool. In this proposal, we propose to utilize previously JFSP funded sites and a research team (Varner and Knapp) that was a model for JFSP success- reasonable budget, an abundance and breadth of science delivery (from field tours to talks to 7 peer-reviewed journal articles). We will exceed our past work via our lessons learned, improved capacity, and affiliation with the JFSP-funded California Science Delivery Consortium and the Northern California Prescribed Fire Council. Finally, by collaborating closely with the developers of IFTDSS, we hope to integrate our findings to assist in fuels treatment planning.