The Importance of Consistent Global Forest Aboveground Biomass Product Validation

Several upcoming satellite missions have core science requirements to produce data for accurate forest aboveground biomass mapping. Largely because of these mission datasets, the number of available biomass products is expected to greatly increase over the coming decade. Despite the recognized importance of biomass mapping for a wide range of science, policy and management applications, there remains no community accepted standard for satellite-based biomass map validation. The Committee on Earth Observing Satellites (CEOS) is developing a protocol to fill this need in advance of the next generation of biomass-relevant satellites, and this paper presents a review of biomass validation practices from a CEOS perspective. We outline the wide range of anticipated user requirements for product accuracy assessment and provide recommendations for the validation of biomass products. These recommendations include the collection of new, high-quality in situ data and the use of airborne lidar biomass maps as tools toward transparent multi-resolution validation. Adoption of community-vetted validation standards and practices will facilitate the uptake of the next generation of biomass products.

Using nonlinear mixed effects models to estimate size-age relationships for black bears

Size–age relationships for three physical characteristics, body length, zygomatic width, and pad width, weremodeled for black bears (Ursus americanus) captured in northeastern Minnesota, U.S.A. Because the curves representingsize–age relationships were nonlinear, and because some of the data consist of repeated, longitudinal observations for multiplebears, nonlinear mixed effects model analyses were required. The results are presented as parameter estimates with standarderrors and estimated population curves with 95% confidence intervals. Variance estimates obtained using mixed-effects modelsare compared with erroneous estimates obtained using ordinary least-squares techniques. Comparisons are made between maleand female Minnesota bears with respect to parameter estimates and estimated population curves. In addition, the results forMinnesota bears are compared with results from similar studies on bears in other regions.