What Role do Birch Shrubs Play in “Greening” the Bathurst Caribou Range?

Vegetation has become more productive on the Bathurst caribou herd’s range in recent decades.

This trend has been detected by satellites measuring light reflectance from actively growing plants, but what does this “greening” trend look like on the ground?

While most tundra plants grow low to the ground, some shrubs, such as dwarf birch, grow tall and erect.

Read this open access paper on the Arctic Science website.

Research elsewhere has found that birch can contribute to greening by growing more or expanding across the landscape.

We collected and compared stem samples from birch in areas that had greened (Greening sites) and areas where productivity did not change (No Change sites) between 2000 and 2017.

Surprisingly, shrubs at Greening and No Change sites were similar in age, abundance, stem length, and density. They were also growing at similar rates both upwards in height and outwards in thickness.

However, birch canopy had significantly more coverage at Greening sites, while birch shrubs at No Change sites had significantly more dead stems.

Given all other similarities, we suspect that birch at Greening sites have increased their production of foliage in the last two decades.

Meanwhile, higher rates of stem mortality may have dimmed any greening signal from No Change sites. The causes of these differences are not altogether known since the different types of sites experience the same general climate.

Nonetheless, our research is the first field study in this part of Canada to examine how satellite measurements of change relate to changes in vegetation measured on the ground.

Read the paper —Greening on the Bathurst caribou range in northern Canada: are erect shrubs responsible for remotely sensed trends? by Carolyn Bonta, Greg King, and Ryan Danby