The Sunken Forest Tour: Salt Spray Dynamics

Salt spray from the Atlantic Ocean has a profound impact on treee growth in the forest.

NPS/Sucena

As a “climax community” The Sunken Forest would not exist except through centuries of gradual succession. From Beach Grass to Bayberry, Pitch Pine to Black Berry Cherry, each plant that has grown on Fire Island has helped to pave the way for what you see here. Look above at the flat canopy overhead and you may start to understand why this place is so unique. Where else on Long Island can you listen to the crashing of ocean waves beneath a canopy of towering trees?

 

This forest exists in a delicate state of balance. As waves on the beach crash, they toss salt into the air forming what is commonly referred to as “Salt Spray.” To humans salt spray can be quite pleasant, it’s what gives the beach that familiar summer smell, but salt spray can have a harsh effect on plants, sapping their leaves of precious water. 

 

As that salt spray travels across Fire Island, carried across by the ocean breeze, it sweeps through the swale and other plant communities. Most of these communities are somewhat adapted to that constant exposure to salt spray, but here in the Sunken Forest the trees are not. 

 

So then, how do these trees manage to grow in an environment which is normally so inhospitable to them? The answer lies in the set of ancient dunes you see before you. Here at Sailors Haven we are lucky to have not only a robust and healthy set of primary dunes, those tall hills of sand you saw when you began on the beach, but also a vast system of secondary dunes. It’s this double dune system which acts as a shield, protecting the forest from the effects of salt spray exposure. 

 

Though the dunes work to protect the forest from most of the salt spray, containing it upon the beach and within the swale, some of that salt spray continues to sweep above the canopy of trees you see overhead. As it does it actively trims or “prunes” the trees in an effect we call “salt spray pruning.” Pay attention to the height of the trees as you walk through the Sunken Forest. You will notice that as you rise closer to the top of the dunes, the trees will shrink, and as you sink below the dunes the trees will grow. It is as if a “salt spray ceiling” sits above the forest preventing its upward growth. This creates the “Sunken” effect to which this forest owes its name, as the trees appear to have sunk into the dunes they grow upon.

 

When it comes to salt spray, however, it is not all destruction. Even as the salt trims the tree tops, potentially killing the forest if the dunes were to suddenly vanish, that same salt spray is what enables this forest to grow here at all. You see, Fire Island and the Sunken Forest are young ecosystems. Their soil is sandy and thin. Even still, were you to investigate the soil of the Sunken Forest you would find it packed with minerals and nutrients brought in by that same salt spray. Those minerals and nutrients act as food for the trees. Without this delicate balance, this forest would not be here for us to enjoy.