Variable-Density Thinning and a Marking Paradox: Comparing Prescription Protocols to Attain Stand Variability in Coast Redwood

Abstract

are often used to treat multiple stands and thereby promote multiscale homogeneity rather than heterogeneity. VDT prescriptions face the additional challenge of needing to create stand-level heterogeneity, where stand structures may already be homogeneous or where prescribing heterogeneity makes marking/thinning prescriptions very complex. When the VDT prescription or marking guidelines are unclear or confusing, forest workers may revert to marking or thinning stands in accordance with the more regular spacing to which they are accustomed. Even well-designed prescriptions can therefore be quickly undermined at the implementation phase. This represents a “paradox” for VDT, where a more complex, heterogeneous stand structure is the management objective but where simple marking/thinning rules are needed for clear and consistently accurate application. We describe six different protocols for implementing VDT in young, overly dense second-growth forests in the redwood region and assess their effectiveness and efficiency for promoting stand structure heterogeneity, and we discuss their implications for future stand development. Because of the potential importance of VDT as a restoration tool in other forest types, our objectives are broadly applicable to other regions and forest types, where VDT may be used to enhance stand structural variability.