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More forest ecology in February

Bark of some trees in the Lehigh Experimental Forest Plantation. Tree identification becomes a bit more challenging without foliage.

On Thursday it was 58 degrees Fahrenheit on the Lehigh campus, and much too nice to stay in the office all day.  We spent a few hours in the afternoon trying to find and core more Norway Maples (Acer platanoides) in the Experimental Forest Plantation (see previous post here).  We spent a lot of our time trying to relocate trees identified in the survey last fall, but we did manage to get more than a dozen new cores.  Our bark identification skills are also improving.   Which trees in the above picture do you think are Norway Maples? (Answer is now in the comments – 1 March 2012)

A less stationary encounter...a red-backed salamander (Plethodon cinereus).


Investigating the history of invasion

Norway Maple

A norway maple (Acer platanoides) growing in the Lehigh University Experimental Forest Plantation. A nice field identification method is to break off a leaf and look for the white sap. Although sugar maple leaves look similar, they do not have the white sap. However, the samaras of the two species are also quite different.

I spent most of today in the experimental forest plantation on South Mountain with Michelle Spicer (Lehigh senior) and Travis Andrews (Lehigh graduate student).  The experimental forest plantation was established in 1915 by Robert Hall, a professor of biology at Lehigh University.  A set of carefully measured plots were created on 5.5 acres of land, and each plot was planted with one or two tree species.  A total of 22 species were planted, both alone and mixed with other species, with the goal of better understanding what species would grow best on South Mountain and similar areas in Pennsylvania.  The plantation was mostly forgotten about by the 1950s, and its recent rediscovery provides many opportunities for interesting science.  We are currently working on several projects aimed at understanding the results of this century-long experiment in forest planting.

Today’s work was aimed at better understanding a species that was not originally planted – Norway Maple (Acer platanoides).  Originally from central Europe and southwest Asia, it was apparently introduced in the 1750s but didn’t become extensively naturalized until much later. The species is quite shade tolerant, allowing it to invade closed-canopy forests.  Once established it may out-compete native tree species, and its dense shade can displace understory shrubs and herbaceous plants.

Coring trees in the Experimental Forest Plantation.

This invasive maple species apparently became established in the experimental forest plantation sometime in the past century, but interestingly, it is only abundant in one of the plots.  Why has it only been successful in invading this one plot?  The invaded plot was originally planted with sugar maple (Acer saccharum) and tulip poplar (Liriodendron tulipifera) and  is located in the center of the forest plantation, making this even more of a puzzle.  Many large tulip poplars still grow in the plot, although we only encountered one sugar maple.  Today, we collected cores from about 25 Norway Maples and 6 tulip poplars, and Michelle will determine the ages of these trees by counting the annual growth increments. The goal of her project is to determine the timing of establishment of this invasive tree species, and hopefully better understand the factors that affect its success.

The video below captures the fun better than the picture.  Michelle is coring a small norway maple and Travis is coring a tulip poplar.  As you can see, even a small norway maple was a challenge to core!

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