Thursday, July 24, 2014

Physiology of Plants on the Tundra...

Earlier in the week I mentioned that this was a cold, cloudy, and wet year compared to the previous two or three seasons that our NGEE Arctic team has worked in Barrow. One of several consequences of that has been a slow start to the growing season for many of the plants that we are studying on the tundra. Plant physiologist Alistair Rogers from Brookhaven National Laboratory has seen this first hand in the data that he has collected as he measured rates of photosynthesis. Alistair comes to Barrow for weeks at a time each summer as part of the NGEE Arctic project to measure processes related to plant physiology. He uses a number of highly sophisticated instruments to make these measurements. Just keeping this equipment in top operating condition takes a considerable effort. However, his hard work is returning many unique insights to the project as we integrate field knowledge into climate models.

Alistair has made a number of observations in the last two years, and he has published a couple of nice papers highlighting rates and underlying biochemistry of photosynthesis for tundra vegetation. Most recently while conducting this research he noticed that plant growth was slow or delayed this year compared to previous years, as was the expansion of leaves that he was relying on for many of his measurements. It was a challenge to find leaves of a suitable size for his gas exchange cuvette. Alistair also noticed the leaves were not as green as they were at this time last year possibly due to cold temperatures, limited thaw depth for root development, and a general lack of nitrogen uptake by the plants. Since photosynthesis is strongly dependent on leaf nitrogen, Alistair has observed that rates are somewhat lower than last year. It will be interesting to see if photosynthesis rates recover to expected levels as the season progresses (and hopefully warms) and as plants continue to grow and mature.


It is important to know that the growing season in Barrow is short, typically just three months or so. Not much time for soils to warm, thaw, and biology to come alive on the tundra.  Plants are particularly challenged this year. Although only the latter part of July, temperatures are expected to soon peak and then decline as we get into August. Winter is on the horizon. A few plants are flowering, but even that seems to be less than what I recall in past years.

It would appear that plants have a challenging time growing in this harsh and highly variable environment. Alistair's research is helping us understand how plants cope and adapt to change in an Arctic environment. Knowledge from his studies will be useful as we seek to improve predictions of climate using Earth System Models.