Document Details

Terrestrial Gastropods as Focal Species for Monitoring Ecological Effects of Variableretention Logging Practices
Ovaska, Kristiina
This proposed project contributes to knowledge gaps associated with Sustainability Program Theme 3, topic 3.1, Indicators and monitoring systems. Terrestrial gastropods (slugs and land snails) were selected as a focal group for examining the effects of variable retention (VR) logging practices on forest ecosystems within Weyerhaeuser?s ecological monitoring program (Bunnell et al. 2003). These organisms were included because of their sensitivity to changes in moisture and temperature regimes and the structure of the forest floor and their sedentary habits, which preclude escape from unfavourable conditions (Ovaska and Sopuck 2000). As a result, gastropod faunas are likely to reflect the disturbance history of particular forest stands (Strayer et al. 1986). This project is a continuation of a pilot study initiated in fall 1999. Initial studies, from 1999 to 2001, focused on characterizing gastropod faunas of different forest types, developing sampling methodologies, and conducting investigations of the sensitivity of different species at operational VR-sites. In 2001 work began at experimental sites with the objective of comparing the effectiveness of different types of VR-treatments and clearcutting on maintaining patterns of species diversity and abundance of gastropods on the forest floor. To date, we have conducted intensive pre-disturbance sampling at six experimental sites on Vancouver Island, coastal mainland, and the Queen Charlotte Islands, as follows: 1. North Island Timberlands (2001): Tsitika experimental site (groups with 3 levels of retention) 2. Stillwater Timberlands (2001): Horseshoe Lake site (dispersed with 3 levels of retention) 3. North Island Timberlands (2002): Port McNeill site (retention using 3 different sizes of groups) 4. Queen Charlotte Islands (2002): East Yakoun/Hoodoo site (groups with 3 levels of retention) 5. North Island Timberlands (2003): Moakwa Creek-White River site (group retention within riparian areas) 6. Stillwater Timberlands (2003): Goat Island site (groups with 3 levels of retention) The above study sites for this research are part of a series of experimental harvesting blocks replicated three times that test different types, amounts and spatial patterns of retention. These Variable Retention Adaptive Management (VRAM) experiments are the foundation of Weyerhaeuser?s AM program. Each block has 4 or 5 treatments: clearcut, uncut (old growth or 2nd growth), and two or three variable retention alternatives (20 ha minimum size for each treatment). Each VRAM site was installed with random allocation of treatments. The sites were chosen to be as uniform as possible in timber type, site series and topographic features. In 2005-2007, we plan to conduct post-logging surveys for gastropods at the six experimental sites described above. Each year two different sites will be selected, starting with the Tsitika and Horseshoe Lake sites in 2005. The objective of this study is to collect post-disturbance data on species diversity and relative abundance of gastropods within areas subjected to different logging treatments and within a control area that has remained undisturbed. These data will be compared with pre-disturbance baseline data of the same areas to assess the effects of variable retention logging practices during the first few years after logging. Such an experimental approach provides a powerful method for examining causal effects of different treatments and for accounting for potential confounding effects resulting from pre-existing differences in habitat. At each experimental site, we will re-survey the four pre-disturbance sampling plots in each of the four treatment areas (clearcut, 3 retention treatments) and in the control area for a total of 20 plots. We will use two sampling methods to obtain relative abundance estimates, based on results from our previous pilot studies: artificial cover-objects (cardboard sheets) and litter sampling. All surveys will be conducted when the f ...
Report Number
Executive summary
Annual Report: terrestrial gastropods as focal species ...

EIRS Search Options

Useful Contacts