Garry Oak in a Common Garden

Quercus garryana

In August 2017, during a visit to Vancouver, British Columbia (Canada) I was able to visit an experimental plantation of Garry oak (Quercus garryana) at the University of British Columbia. The plantation came about as part of a research thesis by Colin Huebert at the Forestry Department at UBC. The project involved collecting seed from 15 native populations of Garry oak, from British Columbia to California, and planting 1,700 seedlings in a plot at Totem Field next to UBC Botanical Garden. This type of trial, known as a common garden experiment, aims to quantify the genetic component of phenotypic variation by raising a number of genotypes in a common environment.

Satellite views of the common garden plantation, the rectangle in the middle of the image, in 2009, 2014, and 2017 (left to right - click on images to enlarge)

Populations of Garry oak have been declining in western North America since European settlement, and it is estimated that only 1-5% of pre-European Garry oak ecosystems remain uncompromised in British Columbia today. However, due to climate change, the area climatically appropriate for Garry oak is estimated to triple by 2080. The objective of Colin Huebert’s study was to investigate levels of genetic diversity among native populations of Garry oak and estimate their ability to adapt to local conditions. Ultimately, the aim is to use this information to recommend seed transfer guidelines for restoration and conservation purposes, and to predict the potential response of Garry oak to future climate change scenarios.

Northeast corner of the Garry oak plantation	Significant variation in height among different trees

The study found weak population differentiation for most traits, with the exception of height, germinant emergence date and cold hardiness, and supported existing evidence that Garry oak is adapted to conditions of intense drought. You can download the thesis here.

Seedlings were planted using a Complete Randomized Block Design with 12 blocks. Each population was represented once within each block for a total of 141 trees per block. Individuals were randomly assigned to both a block and position within block using a random number generator. Seedlings were planted at 60 cm by 60 cm spacing with a single edge row of non-experimental buffer trees surrounding the experiment.

Viewing the plantation 10 years on, it is remarkable to see the variation in habit and height, with some trees reaching up to over 6 meters, and others still only 50 cm high: further confirmation of the infinite variety of our favorite genus, not only among different taxa, but here within a single species.

Variation in leaf shape and density of foliage	Characteristically deep lobes on Q. garryana