High Elevation Record Breakers Are Evidence of Climate Change

A new record has been set for vascular plants. Three mustards, two composits, and a grass have been found growing at an elevation of 20,177 feet (6,150 m) above sea level!

Mountains are a brutal place to live. Freezing temperatures, fierce winds, limited soil, and punishing UV radiation are serious hurdles for any form of life. Whereas algae and mosses can often eke out an existence at such altitudes, more derived forms of life have largely been excluded from such habitats. That is, until now. The area in which these plants were discovered measured about the size of a football field and is situated atop an Indian mountain known as Mount Shukule II.

Although stressed, these plants were nonetheless established among the scree of this menacing peak. Most were quite young, having only been there for a few seasons but growth rings on the roots of at least one plant indicated that it had been growing there for nearly 20 years!

All of them have taken the cushion-like growth habit of most high elevation plant species in order to reduce exposure and conserve water. The leaves of each species also contained high levels of sugary anti-freeze, a must in this bitter cold habitat.

The research team, who could only muster a few hours of work each day, believed that the seeds of these plants were blown up there by wind. Because soils in alpine zones are often non-existent, the team wanted to take a closer look at what kind of microbial community, if any, was associated with their roots.

Whereas no mycorrhizal species were identified, the team did find a complex community of bacteria living among the roots that are characteristic of species living in arid, desert-like regions. It is likely that these bacteria came in with the seeds. Aside from wind, sun, and a lack of soil, one of the other great challenges for these plants is a short growing season. In order to persist at this elevation, the plants require a minimum of 40 days of frost-free soil each year.

Because climate change is happening much faster in mountainous regions, it is likely that such favorable growing conditions are a relatively recent phenomenon. The area in question has only recently become deglaciated. As average yearly temperatures continue to increase, the habitable zone for plants such as these is also moving up the mountain. The question is, what happens when it reaches the top? Once at the peak, plants have nowhere to go. One of the greatest issues alpine plants face is that they will gradually be squeezed off of these habitat islands.

Although expanding habitable zones in these mountains may sound like a good thing, it is likely a short term benefit for most species. Whereas temperature bands in the Tibetan mountains are moving upwards at a rate of 20 feet (6 m) per year, most alpine plants can only track favorable climates at a rate of about 2 inches (0.06 m) per year. In other words, they simply can't keep up. As such, this record breaking discovery is somewhat bitter sweet.

Photo Credit: [1]

Further Reading: [1]

Green Islands

Autumn is here and all across the northern hemisphere deciduous trees are putting on a show unlike anything else in the natural world. The range of colors are spectacular both from afar and up close. If you're like me then every single leaf is worth investigation. The trees are shedding their leaves in preparation for dormancy. The leaves aren't dying outright. Instead, the trees are reabsorbing the chemicals involved in photosynthesis as a way of getting back some of the energy investment that went in to producing them in the first place. 

If you look closely at some leaves, however, you may notice green spots in an otherwise senescent leaf. Why is it that certain parts of these leaves are still photosynthetically active despite the rest of the photosynthetic machinery shutting down around them? The answer to this question is way cooler than I ever expected. 

These "green islands" as they are called are almost always associated with an insect. If you look closely towards the base of these spots you will usually find a tiny leaf mining larvae of a moth busy munching away at the remaining photosynthetic tissue. The most obvious conclusion at this point would be to say that the moth larvae are the cause of the green islands. However, it is not that simple. 

When researchers raised the moth larvae under sterile conditions, they did not produce the green island effect. This proved to be a bit of a conundrum. Why would this happen in the wild but not under sterile conditions in a lab? The answer is bacteria. 

It would appear that the moth larvae have a symbiotic relationship with bacteria living on their bodies. These bacteria interact with the tissues of the leaf and alter the production of cytokinins. In the leaf, cytokinins inhibit leaf senescence. When the plant switches into dormancy mode, cytokinin production is shut down. The bacteria, however, actually ramp up cytokinin production throughout the tissues surrounding the larva. The result of which is a small region or "island" of tissue with prolonged photosynthetic life. 

Because of this, the larvae are able to go on feeding well into the fall when food would otherwise become nonexistent. By harboring these bacteria, the moths are able to get more out of each seasons reproductive efforts instead of simply stopping once fall hits. This is the first ever evidence of insect bacterial endosymbionts have been shown to manipulate plant physiology, though it most certainly will not be the last. 

I would like to thank Charley Eiseman for the use of this photo as well as inspiring this post. Charley is the man behind one of my all time favorite blogs Bug Tracks (https://bugtracks.wordpress.com/) so make sure to visit and like Northern Naturalists.

Further Reading: