Aynslie Ogden

Msc Graduate, 1996

Aynslie Ogden received her B.Sc. in Agriculture from the University of Guelph in 1993. She completed her M.Sc. in Geography (forest ecology & soils) at Simon Fraser University in 1996 and graduated in 1997. She currently works as a research officer for the Northern Climate Exchange in Whitehorse, Yukon and remains active in soil science organizations. Aynslie is a former President of the Pacific Regional Soil Science Society (PRSSS) and is an active member of the British Columbia Institute of Agrologists.

Summary of Research:

Soil Characteristics of Persistent Canopy Openings Occupied by Vine Maple in a Coastal Western Hemlock Forest 1996

Hardwood species contribute to wildlife habitat, biological diversity, soil ecology and the ecology of riparian areas. In some low-elevation coastal B.C. forests, canopy gaps can be occupied by the hardwood species vine maple. Some gaps occupied by vine maple are not the traditional type of developmental gap created by tree mortality in that these gaps have no evidence of a gapmaker (McGhee 1996). Within some gaps, vine maple has the ability to persist and be self-maintaining over long periods of time.

This study was conducted in a western hemlock forest in the Seymour Demonstration Forest Demonstration Forest in the North Shore Mountains of the Coast Range, which is within the Coastal Western Hemlock (CWH) biogeoclimatic zone. The study was designed to determine if vine maple gaps are edaphic gaps (their location across the landscape is a reflection of a mosaic of inherent soil properties) or priority gaps (their location is due to their ability to establish a dense mat of stems early in stand development that is large enough to prevent invasion of the site by conifers). Since no significant differences were found to exist in inherent soil properties between vine maple gaps and the surrounding forest including groundwater table levels, soil moisture below the rooting zone, soil texture and gravel content, the edaphic gap hypothesis was not supported. Consequently, the data supported the alternate hypothesis that vine maple gaps represent priority gaps.

This study also sought to determine the effect of persistent vine maple gaps on soil properties. Since the vegetation in vine maple gaps has differed from that of the surrounding forest throughout stand development, these gaps were found to cause several alterations to soil properties. Vine maple gaps have significantly thinner forest floor (LFH), less conifer litterfall during the fall, higher pH in the LFH, higher CA, Mg, K and Al concentrations in the LFH and a lower (not significant) C/N ratio in the upper mineral soil. Vine maple litter was found to decompose significantly faster than conifer litter and to have higher concentrations of N, P, Ca, Mg, K, Fe, and Zn. Unlike developmental gaps, vine maple gaps have similar temperature and moisture regimes and rates of total annual litterfall and litter decomposition as compared to the surrounding closed canopy forest. However, larger gaps have a significantly greater influence on nutrient dynamics, temperature regimes and moisture regimes than smaller gaps.

PUBLICATIONS
Ogden, A.E., Schmidt, M.G. and Lertzman, K.P. 1998. Seasonal comparison of soil temperature and moisture in pits and mounds under vine maple gaps and conifer canopy in a coastal western hemlock forest. Can. J. Soil Sci. 78: 291-300.

Ogden, A.E., and Schmidt, M.G. 1997. Litterfall and soil characteristics in canopy gaps occupied by vine maple in a coastal western hemlock forest. Can. J. Soil Sci. 77:703-711.

Ogden, A.E. 1996. Soil characteristics of persistent canopy openings occupied by vine maple in a coastal western hemlock forest. M.Sc. thesis, Department of Geography, Simon Fraser University. Burnaby, British Columbia.

aogden@yukoncolle-ge.yk.ca