Abstract. Practicing ecologists who excel at their work (''experts'') hold a wealth of knowledge. This knowledge offers a wide range of opportunities for application in ecological research and natural resource decision-making. While experts are often consulted ad-hoc, their contributions are not widely acknowledged. These informal applications of expert knowledge lead to concerns about a lack of transparency and repeatability, causing distrust of this knowledge source in the scientific community. Here, we address these concerns with an exploration of the diversity of expert knowledge and of rigorous methods in its use. The effective use of expert knowledge hinges on an awareness of the spectrum of experts and their expertise, which varies by breadth of perspective and critical assessment. Also, experts express their knowledge in different forms depending on the degree of contextualization with other information. Careful matching of experts to application is therefore essential and has to go beyond a simple fitting of the expert to the knowledge domain. The standards for the collection and use of expert knowledge should be as rigorous as for empirical data. This involves knowing when it is appropriate to use expert knowledge and how to identify and select suitable experts. Further, it requires a careful plan for the collection, analysis and validation of the knowledge. The knowledge held by expert practitioners is too valuable to be ignored. But only when thorough methods are applied, can the application of expert knowledge be as valid as the use of empirical data. The responsibility for the effective and rigorous use of expert knowledge lies with the researchers.

Forest fire size distribution (FSD) is one of the suite of indicators of forest fire regimes. It is applied in forest fire management, particularly for planning and evaluating suppression efforts. It is also used in forest management in the context of emulating natural fire disturbances. Given the recent growth in research and applied interest in this topic, we review and synthesise the state of knowledge on FSD, and identify sources of knowledge uncertainties and future research directions. Based on literature, it is common for forest fires to follow the power law probability distribution, particularly the truncated subtype, under a variety of forest types and forest and fire management practices. Other types of FSD are also observed, but under specific circumstances. Although there is evidence that observed FSDs vary both over space and time, the knowledge is too fragmented to generalise the cause-effect relationships for such variation. As well, it is not clear how the various methods of studying FSD and their spatio-temporal scales influence derivations of FSDs. We suggest that a hypothetico-deductive research approach, combining empirical studies with process-based simulations is an effective means to advance the knowledge of FSD. We suggest caution in the use of FSD in forest management because applying different distributions or even different parameters for the same distribution may result in great fire size class differences and thus different implications for forest management.

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A B S T R A C TThis study explored and applied the concepts of Fire Regulation Capacity (FRC) and Fire Protection Ecosystem Service (FPES) in the assessment of the effects of landscape change in a mountain fire-prone landscape in Portugal. We adopted a modeling and simulation approach using BFOLDS-FRM with landscape data for years 1990 and 2006 (observed) and with three landscape scenarios for 2020. Proxy indicators for FRC (burned area and fire intensity) and for economic damage by fire (loss of provisioning ES) were used to establish trends in the supply and value of FPES. We found decreased FRC to restrain simulated fires burning over 100 ha from 1990 on and to regulate Very High and Extreme fire intensity levels, particularly under our 2020 scenario of Forest expansion. FPES is also expected to decrease, as indicated by higher fire-related damages, particularly if fuel hazard increases in the landscape. However, there were differences among scenarios, suggesting potential tradeoffs between FPES and the supply of provisioning ES. Planning and management in this and similar areas experiencing farmland abandonment must consider fire trends and patterns, since landscape change is a major driver affecting FRC and FPES, which may further be decreased by future climatic conditions.

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