Dendroecology of the dwarf shrub Dryas integrifolia M. Vahl. near Churchill, Manitoba By Robert Au Supervisor: Jacques Tardif Committee Members: G. Scott and R. Staniforth

Introduction Tree-rings have been used to: - provide annual growth data - determine past climatic events - study forest dynamics However, trees are absent or scarce in the arctic Dwarf shrubs such as Dryas sp. and Salix sp. predominate in these harsh environments

Introduction Shrubs have generally been overlooked in dendroecology Little information exists on dwarf shrubs Dryas integrifolia perennial shrub –widely distributed throughout northern half of North America –important early colonizer –mat forming species –reproduce sexually + vegetatively © Hans Dommasch 2002 University of Saskatchewan Archives

Objectives This study aims to compare allometric relationships among plant dimensions (mat, stem, root) and to compare plant dimensions with age in four populations of D. integrifolia A secondary objective is to evaluate whether D. integrifolia can be crossdated and therefore, have the potential to be used in dendroclimatology

Significance This study will provide useful information for restoration ecology (e.g. areas stripped of vegetation and in need of remediation in the north) Gravel extraction pit

Hypotheses Allometric relationships will be maintained among sites Plant age will follow a linear relationship with mat size in all four study sites Ring widths will be correlated to temperature fluctuations 0 – 5cm10 – 15cm20 – 25cm

Study area Sampling in Churchill, MB Disturbed (A,B,C,D) –chosen according to increasing mat size classes –at least 2 for each class –avg. of 25 plants/ site Undisturbed (Tp) for max. age

Study area Weather station

Site A Disturbed Sites Site B

Site C Disturbed Sites Site D

Field Measurements Longest diameter Taproot diameter Number of flowers Number of species % mortality

Laboratory Measurements Microtome slides produced for each specimen Age of each D. integrifolia was determined by examining annual growth rings Ages x-validated by 2 people 31 years of age B. Jones

Results

Site D 18 years of age 11 cm 69 cm 30 years of age 74 cm 11.3 cm

Results Crossdated specimens contained pointer years, or conspicuous years of growth observed over several individuals

Results Correlation coefficients between the residual growth chronology and climatic variables

Results Reconstructed tree ring index following stepwise multiple regression model using –October t-1 Tmin, May t Precip., August t Tmax and June t-1 Snow

Discussion/Conclusions Allometric relationships among populations were consistent suggesting an equilibrium between above and below ground resource allocation Growth rate was variable within and between sites. Site A was younger and exhibited faster growth D. integrifolia displays a similar response to that of white spruce regarding October climatic conditions (length of growing season) –Girardin M.P., Berglund, E., Tardif, J. and Monson, K –Jacoby, G. C. and Ulan, L. D

Funding / supporting agencies: Canada Research Chair Program, NSERC, Churchill Northern Research Centre, Northern Scientific Training Program & University of Winnipeg Field / laboratory assistants: Derrick Ko Heinricks, Brin Jones Technical: France Conciatori Acknowledgements