Estimating the impacts of harvest distribution on road-building and snag abundance

Abstract

Various patterns of harvest in forests influence the length of road and number of stream crossings required. Snags are removed directly by harvesting, but they are also removed along road and opening edges to ensure worker safety. To assess the potential impacts of rate of harvest and pattern of harvest in an old-forest-dominated montane landscape, we developed a spatially explicit landscape dynamics model, which includes submodels for snag removal, harvesting activities, and access management. The model assesses the amount of new road construction and number of streams crossed by new roads, as well as changes in snag density and configuration across the landscape over a time horizon of several decades, in response to various harvesting patterns. We estimated that a dispersed 40-ha cutblock harvest pattern required about one-third more kilometres of new road over a 50-year period and removal of up to 70% more snags per hectare of harvest for safety purposes, compared with a harvest pattern based on natural-patch size distribution. Each 20% increase in stand-level retention resulted in a roughly equivalent increase in new road required. Up to eight times as many snags were removed per hectare of harvest for safety purposes at a stand-level retention of 70% than at a stand-level retention of 10%. The model appears to be an effective tool for determining the future impact of various harvest-pattern options on a number of important indicators of ecological impact.

Temporal dynamics of snags and development of snag habitats in wet spruce–fir stands in east-central British Columbia

“…The tree mortality patterns, tree and snag fall rates, and snap versus uprooting ratios determined by this study are useful for incorporating deadwood dynamics into existing stand level models. The relationships developed between relative snag age class, tree diameter classes, and tree fall classes and functional habitat availability can be used to further advance stand and landscape-level management and decision support tools (e.g., DeLong et al, 2004) for predicting the effects of alternative forest management options on deadwood habitat availability. Such evaluations of the potential implications of management practices on deadwood quantity, quality as wildlife habitat, and temporal deadwood dynamics are critical in order to develop best practices for deadwood management.…”

“…Recently morphological characteristics of snags have also been used to develop models to predict time since death in order to ease the interpretation of snag habitat changes over time (Newbery et al, 2004;Storaunet, 2004). Quantitative information on snag and log persistence and the relationship between snag or log condition and potential wildlife habitat value are needed for models that predict spatial and temporal effects of forest management on the short-and long-term abundance and/or value of deadwood (DeLong et al, 2004;Densmore et al, 2004).…”

Implementation of natural disturbance-based management in northern British Columbia

“…Apart from resulting in a more natural spatial age mosaic on the landscape, it slows the rate of new road building, new stream crossings, and snag depletion (DeLong et al 2004). Allowing some large patches also reduces fragmentation, which has been shown to have a negative impact on species such as American marten (Martes americana [Turton]) in forested landscapes (Chapin et al 1998, Hargis et al 1999.…”

Influence of stand size on pattern of live trees in mixedwood landscapes following wildfire

“…Retaining higher amounts of residual trees may have significant ecological benefits to plant and wildlife communities (Westworth and Telfer 1993;Norton and Hannon 1997;, Bradbury 2002ab, Fisher and Wilkinson 2002;Schieck and Song 2002). However, there may be tradeoffs that will need to be assessed, since for an equal amount of wood extraction more area will need to be accessed, which may have implications of increased road development, stream crossings and removal of snags if high levels of stand retention are maintained (DeLong et al 2004). scapes to include many of the patterns found after fire (Hunter 1993, Bergeron and Harvey 1997, Delong and Kessler 2000.…”