Crossbill Roots

Elm tree with adventitious roots

This American elm tree (Ulmus americana) has a set of adventitious roots whose appearance reminds me of the illustrations of the crossed bills found on Red Crossbills (Loxia curvirostra) and White-winged Crossbills (L. leucoptera). 

            If this particular small tree had been located in a streamside environment, I would have suspected that erosion might have lowered the ground surface and exposed the root on the left.  However, given the fact that this tree was growing in an overcup oak (Quercus lyrata) / willow oak (Q. phellos) bottomland hardwoods “low flats and ridge” habitat, I suspect that the big root on the left is somewhat adventitious in nature also.

            I don’t know the age of this tree, but given its small diameter and overtopped position, it seems logical to presume that it is relatively young, at least in comparison to some of the approximately 18- to 24-inch dbh dominant willow oaks and overcup oaks in the same stand.  If this is a young tree, then the development of these adventitious roots is a relatively recent phenomenon.

            Did these roots develop in response to a single long-duration inundation event, or are they the products of several such events?  At what time of the year did these roots initiate growth (i.e., during the winter non-growing season, during the early-spring growing season, during the late-spring/early summer growing season, etc.)?  Once growth was initiated, what caused the growth to continue?  Why did some of these roots grow up and over some of the existing roots and over each other?  Is the big root on the left a preliminary stage in the development of a larger fluted root? 

            More food for thought.

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