Arbor Day: Thinking about the Trees for the Forest

This weekend in Louisiana, we are celebrating Arbor Day. Some of you reading this from more northerly latitudes may think it’s absurd to try to dig a hole in the ground in January and a fool’s errand to get anything would take root and live in it. Nevertheless, late winter/early spring is the perfect time for tree planting in Louisiana because it gives the roots several months to establish growth in the new location before our oppressive summer heat sets in. Check out this link for species recommendations and planting tips. Also, for those of you in the Baton Rouge area, the LSU AgCenter Botanic Gardens at the Burden Center will be having a full day of arboreal festivities. If your family plants a tree in the Burden Woods, you get GPS coordinates so you can keep track of your tree’s growth over the years.

If you live in a place where you are still regularly using an ice scraper on your car, don’t plant a tree today. Please consult this link to determine your Arbor Day date. You still have time to order tree saplings from the Arbor Day Foundation that will be best suited for your growing area. For example, if this weekend is not your Arbor Day, don’t order lemon or other citrus trees. Also, if you are inclined to become a Foundation member, you can even get free trees. Keep an eye out for Arbor Day events at your local nurseries, agricultural extension offices and botanical gardens.

I know that Arbor Day is all about planting new trees, but new research published in Nature this week* should change the way we think about old trees too. Yes, get ready for something new about something old under the sun. In case you’ve never thought about it, plants are very different from us when it comes to growth and development. Many plants and trees in particular just keep growing and getting bigger. Researchers had known that trees reach an ‘adolescent growth spurt’ when they grow faster after they’ve reached a certain size, but it had always been assumed that as they get much older their rate of growth slows down. Scientists surveyed more than 600,000 older tree specimens across the globe of more than 400 different species to check this assumption. Crunching all of these numbers on growth rates yielded a surprising conclusion- the majority of older trees were accumulating mass at an increasing rate. In other words, there’s no slowing down in the golden years for these trees.

On a forest scale, younger forests are better (compared to older forests) at trapping carbon dioxide from the atmosphere because there are more trees in a given area for these forests. This new research means reconsidering how individual trees are contributing to this process. On a per tree basis, the data says that older trees are pulling in much more carbon dioxide and converting that to tree mass. Of course, when these large, older trees fall**, the potential for carbon dioxide release is also greater because more is produced as a byproduct of the decomposition process. This is likely why the fast growth of older trees was masked in forest-scale measurements of primary productivity comparing simply ‘young’ vs. ‘old’ forests. These new findings will change the way we think about forest management. When thinking about maintaining optimal productivity of forests, it’s important to keep these older trees instead of culling them.

So, today or whenever your Arbor Day is, make sure you celebrate by planting a new tree and appreciating the older trees in your environment. For more inspiration on superlative trees today, check out my ‘Super Photosynthesizer‘ posts on Hyperion (The World’s Tallest Tree) and Methuselah and Prometheus (World’s Oldest Living Organisms).

Johnna

*Unfortunately, the original research paper is behind a paywall, but check out some of the other links below for more freely-available commentary.

**Whether or not anyone hears it.

References and Links:

http://www.lsuagcenter.com/news_archive/2013/december/headline_news/Arbor-Day-celebration-set-for-Jan-18-at-Botanic-Gardens-.htm

http://www.lsuagcenter.com/en/our_offices/research_stations/Burden/News/Arbor-Day-2014.htm

http://theadvocate.com/features/people/7949344-123/br-getting-ready-for-arbor

http://www.nature.com/news/tree-growth-never-slows-1.14536

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12914.html

http://www.npr.org/2014/01/16/262479807/old-trees-grow-faster-with-every-year

http://www.scientificamerican.com/article.cfm?id=older-trees-grow-faster-as-they-age

http://www.livescience.com/42578-oldest-trees-grow-fastest.html?cmpid=514645

http://www.usgs.gov/newsroom/article.asp?ID=3781