Thursday, July 12, 2012

Elevation and Climate: Visiting Boreal Forest on a Mountain

One of the things that I have become fascinated in in recent years is weather and climate. This interest is evident in the level of detail about weather which the articles go into on RateTea's pages on the various tea-producing regions. One of the key factors in tea production, which is explained in more depth on the page about climate, geography, and tea production, is elevation. A quick summary of the influence of elevation on climate is that temperatures get colder and precipitation (rain and snow) gets greater as elevation increases. And, as hikers at very high elevations are aware of, the air gets noticeably thinner.

Recently, I had the opportunity to visit Massachussets, where I went to the top of Mount Greylock. Mount Greylock is quite remarkable from an ecological perspective. From a distance, it looks a lot like any of the other surrounding hills, but when you actually climb to the top, you will find an ecosystem quite remarkable for a point so far south:

Pictured above is a meadow on the edge of Boreal forest, or Taiga. Boreal forest is common in Canada, Alaska, and the extreme northernmost parts of the continental U.S. But Massachusetts is far enough south that only a small amount of this ecosystem exists, only at the top of this one mountain. Boreal forest reflects the adaptation of plants and animals to cold temperatures, long winters, and short summers. Some of these adaptations include:

  • Trees have a conical shape. This helps to shunt off the heavy loads of snow falling in the winter, so that the trees do not lose limbs. Evergreen trees (like pine and cedar) growing in southerly climates tend to have a rounded shape, because there is little to no snow in the winter; round shapes capture more sunlight, but increase the risk of limbs breaking during a snowfall.
  • Most plants are evergreen. This is because the temperatures are so cold that there is not enough time for the nutrients in the soil to break down and become available to plants; because nutrients are scarce, plants cannot afford to drop their leaves each year. Incidentally, the tea plant's evergreen status is also an adaptation to low nutrient levels, which is why it is able to survive on rocky outcroppings like those in the Wuyi mountains.
  • Deciduous trees have light-colored bark. Think aspen and paper birch (white birch). The temperatures are so cold in winter, and the sun is at a low angle, so that if a deciduous tree (which drops its leaves in winter) were to have dark-colored bark, the sun shining on it horizontally would heat the bark so much that it would crack. This is the same phenomenon of thermal shock that I explained in my earlier post about why teaware can shatter when pouring boiling water in it. The light color of the bark reflects the sun and prevents the heating and cracking of the bark.

These ecosystems extend even farther south, at even higher elevations. For example, one can find a similar ecosystem in the mountains of New Mexico, although there, the ecosystem only shifts to boreal forest somewhere around 8,000 feet. Mount greylock, pictured above, is under 3,500 feet.

Birds galore:

As a birdwatcher, I was excited to explore this ecosystem to find birds that normally only winter or migrate through the areas where I live. It was July, a time when migration has stopped and usually only breeding resident songbirds are found. And I found quite a few birds that I normally only see during winter or migration, including white-throated sparrow, dark-eyed junco, purple finch, winter wren, Blackpoll warbler, yellow-rumped warbler, Blackburnian warbler, black-throated blue warbler, and black-throated green warbler, among others. The Blackpoll warbler in particular is a species that breeds only in boreal forests.

Above is a photo I took of a singing white-throated sparrow, near the summit of Mount Greylock. In Southeastern Pennsylvania and Delaware, these birds are normally only winter residents.

Try looking for the changes in ecosystem with elevation:

If you have the opportunity to hike or drive to the top of a tall mountain in any region of the world, I would recommend doing so. It will not only help you to learn more about ecology, but it will also help you to see firsthand some of the aspects of how geography influences climate which are most important in the production of tea. If you live in an arid climate, such as the southwestern U.S., you will be even more able to see the phenomenon of how precipitation increases with altitude.

These same factors control where the tea plant is able to be grown. In drier countries like Kenya, tea is only able to be grown at higher elevations, where rainfall is higher. But as the elevation becomes too high, temperatures eventually become too cold. In humid climates, tea can be grown the whole way to sea level, and in colder regions, it can only be grown at low elevations.

What do you think?

Do you think much about elevation, and its influence on climate and ecosystems? Have you ever noticed these sorts of changes, when driving or hiking? Do you live in an area with easy access to mountains or changes in elevation? Do you live in or have you ever visited an area that is dry or cold enough that you can see major changes in an ecosystem as elevation changes?


  1. How nice to be able to get out of the city and spend some time exploring a forest. The bird-watching must be amazing!

    1. It is really nice, although, there are actually quite a few nice forests within the city limits of Philadelphia even, as well as quite close to a number of other metro areas I've lived in. San Diego had nice canyons in its city limits, and Cleveland has the metroparks surrounding the whole metro area (still in the same county).

      I think getting out into nature is really essential, no matter where you live!