Station K

Like alligator skin  •  Once upon a pond  •  After the deluge (P3.1)

Are you impressed by this huge black-gum with deeply furrowed bark that looks like alligator skin?  If you are, you are in good company.  An arborist with a special interest in old growth forest was both surprised and impressed to find this giant black-gum tree at Salter Grove.  Given the slow growth rate of the species, it is a very old black-gum. 

Are there other black-gums visible in the vicinity?

Answer >

Definitely!  A quick scan suggests there are at least 40 individuals within view of this station marker! 

By looking for trees with similar bark it becomes clear that there is a sizable grove of both large and small black-gums near by with a few reaching the Upland Trail.  However, juveniles have smooth bark and are more readily identified by branching patterns and leaves.  A systematic survey would be needed to determine the exact number of black-gums at Salter Grove.

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Depending on the date of your visit, the open area on the other side of the black gum is either underwater or an expanse of mud.  This portion of the low-lying wetland may be submerged by as much as 75 cm (30 inches) of water after heavy spring rains.  The accumulation of water would be sufficient to sustain the animal species that inhabit a vernal pond, a fascinating but transitory habitat that appears in early spring.

However, due to the park's proximity to lawns and the parkway, fertilizer and other pollutants enter the pond as runoff.  The resulting algal bloom greatly depletes available oxygen in the pond water.  With the exception of a few Spring Peepers, characteristic species like fairy shrimp, salamanders, and wood frogs have long been absent from the vernal pond at Salter Grove.

Two long-time visitors to Salter Grove fondly recall ice-skating on the pond in the 1940s and the 1970’s, respectively.  The pond has not been frozen solid in the past several years (2016-2020) so it would be great to get more information for intervening decades to understand what changes may have occurred.

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When the pond dries up in July, a group of late-blooming herbaceous plant species populates the exposed muddy bottom.   American burnweed, Devil's beggar-ticks, and common water primrose, are not abundant anywhere else in the park but they form luxuriant beds here in late August and September.  Their flowers are eagerly visited by bumblebees and other insects as earlier blooming plants switch to fruit production. 

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Shrubs that grow along the marsh like common buttonbush and swamp rose-mallow also grow on the exposed mud bank.  The buttonbush even forms a dense grove at the very southern end of the pond.  However, these two species do not flower and fruit as well here as their conspecifics along the Marsh Trail.  

Why not?

Answer >

The plants in the pond area get the requisite moisture, but don't get as many hours of full sunlight as the marsh plants.