Treelines in Transition

Fresh from finishing our survey of experimentally-planted seedling survival rates at the Plantation, today the Team monitored the success of natural treeline advancement from a tree island on the tundra plains of study site NAT3 shown in this photo. Notice the small blue flags in the background left which have been used to mark the location of numerous seedlings that have been carried downwind of their parent trees seen in the foreground right.

On this spongy-moist, moss and lichen-rich bed of tundra (it’s just like walking on a bouncy wet mattress), we discovered the presence of about 90 successful seedlings of varying ages. Did you know that, in order to qualify for true tree status on the tundra, it has to have at least one trunk that extends two meters above the winter snowpack? We were surprised to actually find seedlings ranging in age from 3 to 24 years old, considering how the vast majority of them spend the entire winter season frozen below snow level!



It didn’t take us long to realize that older seedlings require much more detailed measurements. It’s not uncommon to find several branches reaching for apical dominance (to be the top branch). Ultimately, in the game of tundra survivor for these seedlings, the winner will be the one to raise the tallest stem and support it, despite the harsh weather conditions it will face. Those that do survive and become reproductively mature may actually help the treeline advance by filling in the area between existing tree islands with future trees. This, of course, is all dependent upon long term climate cooperation.

Today’s question centers on the process of making predictions. Remember that a prediction is a statement of what you think will happen. Given the description of the NAT3 study site that I described today, what do you predict would happen in the movement of the treeline as the arctic climate experiences progressive gradual warming? Provide supporting evidence for your answer.

Check out the window below for a view of late summer life out on the arctic tundra,
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