Thread by @biotweeps

Let’s talk about the tundra. It’s very beautiful! Here’s some subarctic/alpine tundra near the Swedish-Norwegian-Finnish border where I did fieldwork. (1/17)

Do you see any trees? Nope- there aren’t any in the tundra! The permafrost & climate prevent plants w/ very deep roots from growing. Depending on location are tall or short shrubs (in the pic below). There’s also grass, flowering plants, mosses and lichens. (2/17)

Depending on how you define tundra, it covers a large area of the earth’s land (~8%). It also stores a lot of carbon underground, which is being released with #climatechange. nytimes.com/2017/05/08/cli… (3/17)

Tundra is defined by environmental limitations, so it can be found either at high latitude (Arctic/subarctic/Antarctic/subantarctic or high altitudes. Here’s a map of northern tundra from the @ArcticCouncil. (4/17)

As you might know, #ClimateChange is rapid in the Arctic (and in high-elevation mountain tundra too!). Here's just one example of research about that: theatlantic.com/science/archiv… (5/17)

In my masters thesis I studied climate effects on tundra plant communities, in three places: the Swiss Alps, subarctic Sweden, and High Arctic Svalbard. In Sweden and Svalbard we used plexiglass structures to passively warm the tundra and see what happened. (6/17)

This is an approach that has been used all over the world by a big collaborative group called the International Tundra Experiment (ITEX). It was cool to be part of this project! (7/17) gvsu.edu/itex/

How do we do this? We use several methods to characterize the plant communities. A really common one (not just in tundra) is the point frame: (8/17)

At each place the strings cross in the frame, we drop a pin down and count what plant material that touches it: what species & if they are alive or dead, etc. Then we sum across the whole area (quadrant) to get an estimate of community composition & abundance. (9/17)

In 1999, ITEX scientists published the first meta-analysis of the experiments: data from 13 sites that had been warmed for 1-4 years. These early responses showed earlier budburst and more biomass (plant growth) in warmed plots. (10/17)

But what’s really cool about these experiments is that many of them were carried on for a long time! Long-term responses can be different than short-term ones. Long term research: (11/17) #ScienceNineNine

Two 2012 papers led by Sarah Elmendorf (#CiteWomen!) looked at longer-term effects of #climatechange, w/ data from dozens of sites & decades of time. They found that vegetation responses to warming often got stronger over time. (12/17)

(Side note: at our Svalbard site, my masters research w/ Elisabeth Cooper @UiTromso found that tundra vegetation changed surprisingly little with warming. There were a lot more dead plants, but not more living plants after 12 years of warming. (13/17))

What’s really scary is that in the control (unmanipulated) plots from 46 Tundra sites, over decades plants got taller & there was more dead plant material and shrubs– with “just” an average of 0.72°C of warming that happened w/ current #climatechange (14/17)

Another big synthesis was recently led by @annebeejay and found that plant height increases a lot with warming in the tundra, but other trait changes aren't so strong. (15/17)

Understanding the effects of #climatechange is really complicated. The most recent synthesis/meta-analysis papers found that soil moisture (water availability) determined how tundra communities/plants responded to warming. (16/17)

So far I’ve talked just about the plant responses to climate change in the tundra. Do you have any questions about that? What else do you want to know about the tundra? Why do you think these plant responses might matter? I’ll answer Q’s and continue this story later! (17/17)