Botanical implementation and validation monitoring of project buffers
Areas selected for timber harvest often contain rare and threatened species that are known to prefer interior and/or old forest habitats. Because of this, areas of uncut forest are frequently
Areas selected for timber harvest often contain rare and threatened species that are known to prefer interior and/or old forest habitats. Because of this, areas of uncut forest are frequently left where these species are known to occur in order to provide refuge habitat. However, because these patches are surrounded by cut forest, the may be subject to edge effects that may have negative impacts on the species of concern. The depth to which the edge-effects can penetrate the interior of a forest is dependent on many different variables including forest type, soil composition, and microclimate gradient. Currently, the Medford District of the Bureau of Land Management (BLM) requires a 100ft. buffer around Sensitive Species populations during timber operations on publicly owned lands.
Monitoring stations were placed at select distances within the cut area, buffer area, and along the edge between the two area. Data was recorded and later analyzed from July 24 – September 2, 2007. For each variable (above ground temperature, below ground temperature, and relative humidity) we calculated the daily minimum, maximum, average, and variance. We also randomly selected one date, 1 August, and calculated the hourly minimum, maximum, average, and variance.
While there was some edge effect for a few of the variables, this effect tended to be relatively small. There are a few factors that may have contributed to not finding much of an edge effect in this study. First, we monitored temperature and relative humidity in what is usually the hottest and driest time of the year when hourly and daily variation tend to be relatively small. Thus, the hot and dry conditions would be expected to penetrate further into the interior of the forest at this time of year. Second, many of these areas were subjected to thinning or selective cut, which still leave some of the forest canopy intact; the majority of the studies that have found significant edge effects studied the effects of clear-cutting which has a much greater effect on the canopy. It is also of note that many species, particularly forbs and fungi, are either not active during this time period or are near the end of their yearly growth cycle.
We plan to repeat this study late April through June 2008 in order to determine if there is an edge effect on climatic variables at these sites at a time of year when we expect to find greater hourly and daily variation and that is more biologically relevant for Sensitive Species.