Tuesday, June 2, 2015

Answer: Why so ... young?

It seemed to me... 

that the trees in the Dartmouth area were preternaturally young.  And this week's Challenge was to figure out why the trees in the greater area of Hanover, NH, were all around the same size: 

More importantly, they did NOT look like this: 

Old growth forest in NH (Nov, 1915). Image from Harvard arboretum. This tree fell during hurricane of 1938.

For this kind of a search, I turned first to Google Books and did a search on: 

     [ history of Dartmouth ] 

and found a number of books, all of which agreed that when Dartmouth was founded in 1769, the area was a forest primeval, and full of some very large, very impressive trees.  In one of these books, A History of Norwich, Vermont (Dartmouth Press, 1905).  I did a text-search for "tree" and found "..one tree was found to be 270 feet by actual measurement.  An acre of land could be enclosed, it is said, by four of these monsters properly felled.."  It goes on to point out that some of the largest pines by the river were between 300 and 400 years old, by count of their rings.  (You have to know that Norwich is directly across the river from Hanover, NH, maybe 1 mile away.) 

From this book (and others in that set), we know that there were VERY large trees in the Hanover area until the middle 1800s.  Then, timber was harvested with a vengeance. 

As I was searching, I remembered that Arcadia Publishing prints books that are basically collections of archival photos.  Maybe that would be a good place to start!  In Google Books, I did a search for: 

     [ "Arcadia Publishing" Dartmouth ] 

and found a few remarkable books.  The first I reviewed, "Early Dartmouth College and Downtown Hanover" (by Frank J. Barrett, Arcadia Publishing 2008) has a couple of photos from the Dartmouth Special Collections showing the clearcut farmlands around Hanover and Dartmouth from the 1860s.  As you can see, there's not a lot of trees here.    

So I'm willing to bet that nearly all of the trees we now see in the greater Hanover area date from after 1869.  

What else could have happened to the Hanover trees since 1869?  

I did a simple query: 

     [ "history of trees" Hanover NH ] 

which led me to the Wikipedia "History of New England" article, which told me about the New England hurricane of 1938, which led to a great loss of trees in New York, Connecticut, Vermont, and New Hampshire.  (Note also the caption on the original photo of "Old Growth Forest" above--that tree was also lost in the 1938 storm.)  

This suggested that the trees of the Hanover area have had some... challenges... over the years.  Deforestation, storm damage, and when I did the query: 

     [ trees Hanover New Hampshire ] 

Reading through those results I was reminded of the devastation of Dutch Elm disease, which first arrived in New England in 1928, and wiped out a large number of the elms in New Hampshire.  

I spent a good deal of time searching for other archival images of Dartmouth, trying various searches: 

     [ age of trees Dartmouth ] 
     [ forest history Hanover NH ] 
     [ woods history Groften county ]    - the county where Hanover, NH is located 

etc etc.  And while I looked at many, many pages, I wasn't able to find any truly authoritative work.  

One of the tricks I often use to solve Challenges like this is to imagine the perfect document that would answer my question.  Then step back and ask, what would that be like?  And, using what insights I get from that envisionment process, try to find something perfect. 

Searches on News and Scholar yielded a few results.  Interestingly, one scholarly paper (DeGraaf & Miller, 1996) said that "... nearly all of the arable land of southern New England was in crops and pasture by 1820 - 1840..." and that major changes have happened to the region since then as a result of diseases and storms.  

But what I could NOT find was the perfect result.  Instead, I found lots of clues... 

And so we're left pulling together pieces of evidence from photographs and documents of effects that are hinted at by other writings.  

Another paper I found in Scholar from my search: 

     [ natural history trees OR forest hanover NH OR "New hampshire"  ] 

was Peart, et al.  (See below for citation.)  

(I chose to use "natural history" as I saw that phrase coming up time and again in my research.  It seemed like a bit of terminology that would be useful to me.)  

As they write:  
Canopy structure following the 1938 hurricane and subsequent salvage logging was evaluated from 1942 aerial photographs for six gauged watersheds in the northern hardwoods forest at the Hubbard Brook Experimental Forrest, N.H. ... In 1942, percent openness (area without canopy cover) ranged from 13% to 38%... However, damage was patchy: the most heavily damaged area (72% open) was that which was logged least before the hurricane, and watersheds with most evidence of young second growth prior to the hurricane were apparently the least damaged. [however...] Recovery of the canopy in the heavily damaged area was rapid: in 1978, only 9% of the area was open, and canopy structure was similar to that in the gauged watersheds. Thus, 40 years of canopy development effectively masked the patchy effects of hurricane damage. 

And that pretty much matches what I'd seen in and around Dartmouth.  There are lots of trees, but mostly more-or-less similar in size and girth.  

After the heavy deforestation from the 19th century, and after hurricanes and diseases (such as Dutch Elm), the forest of Hanover seems to have been pretty much rebooted in the 1940s.

And that's most likely why the woods look as they do--beautiful, but rather young.  

Search Lessons

1.  Sometimes you have to integrate information across a number of sources.  This was the biggest thing I was doing here--pulling pictures from here, reading journal articles there, checking out books from the 19th century.  Sometimes there IS no one single resource that pulls it all together for you.  

2.  It's still useful to know some resources.  One of the most valuable bits of information I had was knowing that "Arcadia Publishing" tends to put out books with lots of archival images.  The site: restricted search on the Arcadia website was incredibly useful.  But I wouldn't have found it unless I knew--ahead of time--that these kinds of books existed.  

3.  Special terms can help out a lot.  Using the phrase "natural history" was a success in searching for books and papers about the forests around Hanover.  Be sure to notice these commonly-used phrases as you read about a topic or area.  They let you hone in on what you seek.  

4.  I didn't really know when to stop!  This Challenge took me more time than most (about 4 hours) because I kept having the feeling that someone  must have written about this phenomenon, but I just couldn't find it.  There really are times when you just have to stop, and trust that you'll find something more in the future.  You never know.  

Search on!  


DeGraaf, Richard M., and Ronald I. Miller. "The importance of disturbance and land-use history in New England: implications for forested landscapes and wildlife conservation." Conservation of faunal diversity in forested landscapes. Springer Netherlands, 1996. 3-35.

Peart, David R., Charles V. Cogbill, and Peter A. Palmiotto. "Effects of logging history and hurricane damage on canopy structure in a northern hardwoods forest." Bulletin of the Torrey Botanical Club (1992): 29-38.


1 comment:

  1. Preternaturally is new for me. Also didn't know about "Arcadia Publishing."

    Search lessons are great and also the topic. For example, how trees inside campus were less affected by diseases and the fact that since those days tree zones are helped.

    [natural history trees] is something that I would never have thought of using.

    Never stopping is so true. I most of times, find so interesting information that is hard to stop. And much more when you have those feelings that something is missing. Do you have some time in calendar that tells you when to stop ? I have assigned times for the Challenge and after that time, look for new space and keep searching.