Friday, August 23, 2013

Asymmetric Burl Sprouting in Wieslander’s manzanita

Arctostaphylos manzanita ssp. roffii is one of 6 recognized races of a common, often dominant, California manzanita.  The 6 tetraploid races of Arctostaphylos manzanita largely have allopatric geographic ranges.   The Roof manzanita is not a listed rare plant: it is a relatively uncommon however, and is narrowly endemic to the Cascade and North Coast ranges, with one central Sierran exception (SBBG50844)

The Ponderosa fire burned about;25,000 acres of Tehama and Shasta County in August, 2012.  Areas where I had seen and collected Arctostaphylos manzanita ssp. wieslanderi before the fire, I had not understood the differences between the two subspecies.  In the Ponderosa Fire, both were burnt to a crisp. In May, 2013 I revisited one site, and observed Arctostaphylos manzanita ssp. roffii resprouting.

In the instance recorded here, resprouting did not occurring over the entire burl.  Rather, the only resprouts were originating from below the soil (as seen at the 4 o’clock position on the photo of the burl).  In the present instance, it appears as if the fire was sufficiently hot so as to completely kill all of the exposed portion of the burl, leaving only the below ground parts viable.

Resprouting dymanics of chaparral shrubs following fire, including genetic signaling pathways and how they become activated, are a fertile subject for study.   Burn baby burn...

Photo: resprouting burl on April 25, 2013; ca. 5 miles E of Manton, Tehama County.

N.B.  on the original post, dated 8/23/2013, I mis-identified these plants as A. manzanita ssp. wieslanderi.  On April 11, 2014 I again visited the Ponderosa Fire region as part of my vegetation characterization studies, and confirmed that both infrataxa occur in the region.  A. manzanita ssp. wieslanderi lacks a basal burl, while A. manzanita ssp. roffii has a huge burl.  A. manzanita ssp. roffii is superficially similar to A. patula, which also lacks a basal burl (but does resprout epicormically after fire), and which occurs at higher elevations in the Battle Creek watershed.

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