Trip Photos

The Search for Root Collars

One of the things we were interested in was the growth patterns of shrubs in the Bathurst Caribou herd range. Specifically, we wanted to know how climate has affected shrub growth. We have already looked at the greening patterns in the satellite data, but the shrubs themselves have a story to tell us. At each of our sites we would try to find fifteen of the oldest living shrubs we could. Oldest is a difficult thing to tell – sometimes the largest shrubs just have access to more water or nutrients and sometimes they really are the oldest.

Emily & Greg finding what seems to be an old shrub. They are tossing down the tools they were carrying in preparation to start digging.

Emily & Greg finding what seems to be an old shrub. They are tossing down the tools they were carrying in preparation to start digging.

Once we found what seemed to be an old shrub, we would try to get to the oldest part of it to take a sample. The oldest part is where the root and stem meet – the root collar. This sounds simple, but in practice it was difficult to find. The samples we took needed to have a consistent growth direction so that we could count the growth rings when we returned to the lab (and dwarf birch growth rings are very difficult to see, unlike the spruce or pine growth rings many people are more familiar with). A few shrubs had a clear root collar, with stems above and roots below, but most were a mess of multiple stems and roots growing in every direction.

A complete birch shrub, including the root ball which is often underground.

A complete birch shrub, including the root ball which is often underground.

Cutting the largest stem closer and closer to the root ball to see if we can get the oldest part - the root collar. Even on the top part you can see some small roots though.In these cases, we would try to get to the base of the largest stem to get the oldest sample we could. We are currently busy counting and measuring rings on all the samples we brought back. These samples will give us a picture of how quickly shrubs have been growing each year over their life. When we correlate this with our satellite data, which goes back about 20 years, we will gain much more information about how the vegetation has been growing over the last 20-40 years or so (depending on the age of all the samples we gathered).

Cutting the largest stem closer and closer to the root ball to see if we can get the oldest part – the root collar. Even on the top part you can see some small roots though.

At the end of a day we would let the samples dry out to keep them from rotting before we put them in a dry bag.

At the end of a day we would let the samples dry out to keep them from rotting before we put them in a dry bag.

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