The effect of paper birch (Betula papyrifera marsh.) root reinforcement on terrain stability in British Columbia

Abstract

Management of paper birch in mixedwood stands is a sustainable forest management practice. In addition to the ecological and economical benefits of mixedwoods, paper birch trees can maintain or enhance slope stability. This thesis attempted to quantify the contribution of birch root reinforcement in BC to slope shear resistance. The objectives of this thesis were to determine the: 1) genetic variation in paper birch root reinforcement, 2) environmental variation in root reinforcement between birch and pine, and 3) differences in root reinforcement between birch and pine. The first study compared the contribution of birch and pine roots (from different populations growing in three soil types) to soil shear resistance using two controlled environment shear tests (Sonotube and Polytube Experiments). The second study (Tree Uprooting Experiment) compared the vertical uprooting resistance of birch and pine growing in different soil types at three field study sites. The third study (Genecology Experiment) determined the variation of four birch populations growing at one location. Results from the tube experiments found that the roots of birch and pine trees contributed to a significant increase in shear strength, regardless of soil type. At a depth of 20-44 em, paper birch increased shear strength by as much 88%, while pine increased strength by as much as 61%. There was little variation in root reinforcement among the six birch populations in the Sonotube Experiment, which suggested that these trees were from one generalist population rather than six specialist populations. Soil texture affected the root reinforcement of birch and pine in the Polytube Experiment~ both species had the highest root reinforcement in coarse textured sand and the least root reinforcement in medium textured silt. The limiting factor in root reinforcement, in this case, was attributed to a lack of water and nutrients in the silt soil. In the Tree Uprooting Experiment, birch trees had 50% greater resistance to uprooting than did pine trees. Small diameter birch and pine at Aleza Lake had greater uprooting resistance than birch and pine at other field sites. However, larger diameter trees at Gregg Creek and Red Rock had greater uprooting resistance than similar size trees at Aleza Lake. Soil strength and moisture content may have accounted for the uprooting resistance differences among diameter classes at Aleza Lake. Results from the Genecology Experiment showed that the Skeena population had the greatest uprooting resistance, and the greatest height, diameter, and root biomass compared to the other three populations. The results from companion trials, and from the uprooting tests suggested that Skeena trees represent a generalist population. In the same experiment, the nursery where the trees were grown impacted uprooting resistance, even after five years growing in the field. The results from this study reconfirmed the significant length of time nursery can affect field performance. Significant findings arising from this thesis were ...

Effect of seed source and nursery culture on paper birch (Betula papyrifera) uprooting resistance and field performance

“…Paper birch is a shade intolerant, fast-growing, early successional species that colonizes exposed mineral soil soon after disturbance. The rooting morphology and architecture of birch, in combination with its ability to establish quickly in nutrient poor soil allows birch trees to reinforce potentially unstable slopes (Campbell, 2001;Campbell and Hawkins, 2003). Birch also plays Forest Ecology and Management 196 (2004) [425][426][427][428][429][430][431][432][433] a vital role in the health and function of forests, such as providing overstorey cover for young conifers, and reducing both white pine weevil (Pissodes strobi) and the spread of Armillaria root rot (Peterson et al, 1997;Carlson et al, 2000).…”

“…One potential application of broadleaf management is the planting of young paper birch seedlings to enhance slope stability in areas vulnerable to landslides (Campbell, 2001;Campbell and Hawkins, 2003). Critical to the successful management of broadleaf species such as paper birch for slope stabilization is a better understanding of regeneration and field performance.…”