Abstract Detail

Forest Tree Responses to a Changing Climate

Hogg, Edward H. (Ted) [1].

Multi-year impacts of drought on stand dynamics of aspen forests in western Canada.

Over the past decade, there has been a notable increase in reporting of drought impacts on forests around the world. One of the affected species is trembling aspen (Populus tremuloides), the most abundant deciduous tree in the North American boreal forest. In response to public and forest industry concerns about aspen dieback in the 1990s, we established a regional study entitled “Climate Impacts on Productivity and Health of Aspen” (CIPHA). CIPHA is a multi-scale study that includes tree-ring analysis, aerial surveys, remote sensing, and ground-based monitoring of aspen in 180 plots across the boreal forest and parklands of west-central Canada. The CIPHA study was initiated in 2000 and has continued through partnerships with the Province of Alberta and other agencies. In 2001-2002, an exceptional drought affected the study region, leading to massive aspen mortality along the northern edge of the prairies. The prior establishment of CIPHA provided an ideal opportunity to assess aspen forest responses to this drought over a 10-year period. Results showed that the drought led to a regional, multi-year collapse in aspen biomass increment owing to reduced growth and a nearly 3-fold increase in mortality losses. Furthermore, the drought led to a change in the size distribution of dying trees. In sites where drought effects were minimal, mortality affected mainly small, suppressed aspen, reflecting the normal process of self-thinning, whereas large size classes of trees died in the more severely drought-affected sites. We also recorded an increase in stem damage by wood-boring insects and fungal pathogens, which likely amplified and prolonged the drought’s impact. Re-measurement of the CIPHA plots in 2012 indicated that aspen productivity had recovered in some stands, but regional mortality losses had not yet returned to pre-drought levels. Overall, the CIPHA results to date show that drought can operate as a major disturbance with long-lasting impacts on aspen forest health and stand dynamics. GCM projections indicate a likely northward movement of prairie-like climates into the boreal forest during this century. Thus, it is imperative that drought be included as a disturbance type when forecasting future changes in boreal forest health, carbon cycling, and wood fiber supply.

Related Links:
Overview of CIPHA study

1 - Canadian Forest Service, Natural Resources Canada, 5320-122 Street, Edmonton, AB, T6H3S5, Canada

Keywords:
boreal forest
Tree mortality
drought
climate change
Populus tremuloides.

Presentation Type: Symposium Presentation
Session: SY13
Location: Hall A/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 8:15 AM
Number: SY13002
Abstract ID:448
Candidate for Awards:None