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Sunday, March 27, 2016

Cape Cod Ecology

For my annual holiday visit home each year, I've made a tradition of stopping at a local Barnes & Nobel before seeing family after the long drive from Ohio to Massachusetts. Always with a warm coffee in hand, I scour the travel section in search of weekend New England haunts to explore while I let the nostalgia of my hometown sink in, and my legs stretch. This year, I came across a map of Cape Cod that brought me back to memories of family beach days and late-night fishing trips; then I remembered hearing about the Cape Cod National Seashore (CCNS) - home to the longest stretch of undeveloped shoreline on the east coast. In my experience, national lakes and seashores are some of the most well-kept and scenic areas that always seem to be in the heart of a historical hotspot like the old whaling towns of the outer Cape - artifacts of what are now centers for culture and art. With minimal traffic, free parking, and uncontested views of the offseason, I couldn't pass up the opportunity to see Cape Cod from on ecological perspective. Even though the winter weather outlook was fierce for the weekend, I bought the map and began to plan. 

Cape Cod is an 18,000 year old glacial outwash that was formed as large terminal moraines at the end of the last glacial period in North America (Wisconsonian), and is one of the largest barrier islands in the world. Archaeologic findings suggest humans have occupied these lands for the past 12,000 years. Since the colonization of North America in the 17th century, Cape Cod has undergone major disturbances. Logging for agricultural lands, urban sprawl, and over-harvesting of marine wildlife (mostly via whaling) have all contributed to a worn land-use legacy; however, the creation of the CCNS in 1963 by John F. Kennedy was a huge step toward conserving this ecologically important area. 

Massachusetts is part of the Eastern Deciduous Forest, and has three distinct ecoregions: Northeastern Highlands, Northeastern Coastal Zone, and the Atlantic Coastal Pine Barrens. Cape Cod exists in the Atlantic Coastal Pine Barrens ecoregion, which is a globally uncommon community only found here and New Jersey. This community is predominately made up of pitch pine, with a mixture of hardwood plant communities throughout.

Early Pilgrim writings describe the forests of Cape Cod as open woods that extended to the very "brink of the sea."  Although, in the 18th and 19th centuries, agriculture dominated the landscape, drastically impacting the forested landscape and ecology of Cape Cod. When Thoreau visited in the 1850s, he described an area completely devoid of trees. Soon after, an extensive effort to plant trees for erosion control took place as the shift to a tourism-driven economy arose. Today, forests are returning with a higher proportion of hardwood species for many reasons. Currently, the dominant tree species is still pitch pine (Pinus rigida), with greater levels of black oak (Quercus velutina), white oak (Q. alba), and bear oak (Q. ilicifolia) than ever before. Other  abundant species include red maple (Acer rubrum), American white cedar (Thuja occidentalis), and American beech (Fagus grandifolia). Black locust (Robinia pseudoacacia) groves can also be found in certain areas - they were introduced from southern states to assist with erosion control.

During this trip, I was fortunate to visit most of the top scenic areas throughout CCNS; Among the forest types, scrub forest (pictured) seemed to exist more than any other, which makes complete sense due to the poor acidic soils and harsh weather conditions of Cape Cod. This is an area with harsh winters and heavy salt spray from the ocean. Further, the sandy soils are very nutrient poor, acidic, and retain little to no water - it takes hearty, drought-resistant species like oaks and pitch pine to survive here, which they have proved to do for thousands of years. In the scrub forest I encountered, stunted pitch pine, bear oak, black oak, and white oak dominated the landscape. Their stature is not an indication of age as it takes a lot longer for trees to grow here than in more temperate areas throughout the country. The moisture from the ocean provides excellent conditions for a variety of lichens to take refuge, and the herbaceous layer consists mostly of grasses. Prior to fire suppression efforts, this landscape was well adapted to random fire events caused by lightening strikes.
Bear oak is a scrubby, slow-growing species that is found is harsh environments with low nutrient availability. The gnarly, stunted growth form is an indication of this species' toughness. Pitch pine grows predominately throughout the Appalachian mountains and Atlantic coast, where it does well in sandy, acidic soils. Here in Ohio, we find them on ridge tops, often on xeric ridge tops where soil nutrients are low. Although, in Ohio, I have yet to see the characteristic epicormic branching seen in many field guides like that of Cape Cod pitch pines. I wonder what this might be an indicator of. Pitch pine got its name from the pitch it produces, which was used to make turpentine spirits and other resinous products.

Oak trees were mostly suppressed to the understory from the abundance of pitch pines - an allelopathic species that emits growth-inhibiting chemicals into the surrounding soil; but with the help of the turpentine beetle pest, forest gaps, and natural succession, oaks have begun to increasingly reach the canopy. Oaks are hardy, shade tolerant tree species that live longer than pitch pines. Although black oak is by far the most dominant representative of this genus on Cape Cod, red oaks are also found where the soil is more fertile. Also, post oak is an uncommon species on the Cape as well.

As secondary forest begins to grow, patterns emerge that indicate human disturbances have completely altered the vegetation of Cape Cod. For example, the area was almost completely forested pre-settlement. Half of the land was "improved" or, cleared for timber, and the other half was cleared for agriculture. Land that was plowed now seems to be forested with pitch pine. Although, land that was only cleared for timber retains many more oaks. Clearing forest also opened up the door for heath barrens that are important for erosion control on the Cape. 

Unfortunately, a lethal insect pest has recently made its way to Cape Cod and the islands, which preys on black oak trees - a species of tree that makes up a quarter of the trees in the area. The oak crypt gall wasp is worrying entomologists, especially because little is known about this insect. They suspect climate change has something to do with their spread.

American beach grass (Ammophila breviligulata) and beach heather (Hudsonia tomentosa) often grow in close procimity to one another, and serve similar functions in dune ecosystems. American beach grass has many strains, but the above-mentioned Cape Cod species was selected for use to replant along the eastern seaboard after a devastating hurricane in 1938 damages a lot of the dune systems. It is also planted along the great lakes to protect dues there as well. Beach heather is also common along the dunes in CCNS, and is well adapted for harsh windy conditions with its low-growing growth-form. The sand-loving earth star fungus was strewn about the dunes, and a terrapin diamondback turtle nest was found nearby.

One of the highlights of my trip was hiking the Great Island Trail in Wellfleet, which offered a glimpse of tidal marshes, pitch pine forests, and tall dunes. Along the way, I found dozens of Wellfleet oyesters, renowned for their sweet, fresh taste. Cape Cod has historically been surrounded by very fertile, clean waters that increase the taste of oysters, and foster many marine organisms. In fact, Stellwagen Bank is three miles from Provincetown and still draws various of species of whales for the abundance of zooplankton it harbors. The shallow waters there create a very rich ecosystem that fishermen still take advantage of today; although, due to years of over harvest, the whaling industry that helped build many the towns took a large toll on whale populations.

Two common plants found atop the dunes of CCNS are bearberry and bayberry. It is no surprise to see bearberry growing along the harsh dunes of Cape Cod since it is found in subalpine climates of the north. Bayberry forms fruit that have a waxy coating, which is still used today to make candles. The second picture from the right is broom crowberry - a regionally endemic plant that is found in coastal sand-plain communities from New Jersey to Newfoundland. It is listed as a Species of Special Concern by the state of Massachusetts. Cape Cod has long harbored some of the largest and best known populations of broom crowberry, with descriptions by early settlers depicting carpets of the plant and healthy seedling recruitment. Lastly, Massachusetts' state flower, Mayflower, can be seen blooming practically anywhere along Cape Cod.
Atlantic white cedar inhabits some kettle holes found on the Cape, which is close to the northern-most extent for this species. At one time, this species was very abundant, but has since declined due to climate change over time, and over-harvesting. 

Humans long favored the rot-resistant, durable wood from this species. Native Americans used hollowed out white cedars for canoes, and early settlers made cedar shingles, which is why in-tact cedar swamps like this one are difficult to find. 

This trip not only brought back childhood memories; it also proved to be a learning experience filled with the sights, sounds, and scents of New England's coast that I've missed dearly while being in Ohio. As my education is nearing its end, it feels more and more like time to head back home for some period of time before entering my field for the rest of my life. It is always exciting to return to a place I visited as a child, and see it from a new perspective - a much more informed and observant perspective. At the end of this trip, I felt like I had traveled full circle. Regardless, one thing is for sure - Cape Cod is one of the most beautiful places I've been.The Cape Cod National Seashore is well worth the trip.

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