Yvette L. Dickinson

Spatial variability of surface fuels in treated and untreated ponderosa pine forests of the southern Rocky Mountains

There is growing consensus that spatial variability in fuel loading at scales down to 0.5 m may govern fire behaviour and effects. However, there remains a lack of understanding of how fuels vary through space in wildland settings. This study quantifies surface fuel loading and its spatial variability in ponderosa pine sites before and after fuels treatment in the southern Rocky Mountains, USA. We found that spatial semivariance for 1- and 100-h fuels, litter and duff following thin-and-burn treatments differed from untreated sites, and was lower than thin-only sites for all fuel components except 1000-h fuels. Fuel component semivariance increased with mean fuel component loading. The scale of spatial autocorrelation for all fuel components and sites ranged from <1 to 48 m, with the shortest distances occurring for the finest fuel components (i.e. duff, litter). Component mean fuel particle diameter strongly predicted (R2 = 0.88) the distance needed to achieve sample independence. Additional work should test if these scaling relationships hold true across forested ecosystems, and could reveal fundamental processes controlling surface fuel variability. Incorporating knowledge of spatial variability into fuel sampling protocols will enhance assessment of wildlife habitat, and fire behaviour and effects modelling, over singular stand-level means.

An evaluation of tree marking methods for implementing spatially heterogeneous restoration

ABSTRACT Silviculturists are increasingly focused on the development of structurally complex forests through spatially heterogeneous treatments; however, the implementation of these treatments is challenging. We investigated the effectiveness of three tree marking methods used to implement spatially heterogeneous restoration treatments on Colorado’s Front Range: Individual Tree Marking (ITM) physically marks all trees that are either to be cut or left; Designation by Description (DxD) provides a description of the trees that are to be removed based on specific tree characteristics; and Designation by Prescription (DxP) provides the operator with a description of the desired outcomes of the treatment. We employed a mixed methods approach by (a) quantitatively comparing the heterogeneity of stands that have been treated; and (b) interviewing personnel involved in the implementation of these treatments to qualitatively evaluate their efficiency and effectiveness. Neither the quantitative nor the qualitative study methods found a single marking method that was superior to the others in all respects. However, several factors should be considered when selecting a tree marking method, including: the need to set clearly defined silvicultural objectives; personnel experience; trade-offs among personnel; the use of hybrid marking methods; and the range of acceptable outcomes.