Exploring the Layered Series of Grasses in an Island

Image 1. Ammophila breviligulata in center

Assateague Island straddles both Maryland and Virginia. It is a narrow barrier island that I visited and hiked this month, and it contains several ecological areas that made it quite diverse when it came to species diversity. Click here to look at a map of the island.

While I was there it came to me that the distribution of the grass species could be described as a series of layers. The major species were different as one went inward from the beaches to the marshes, and then to the drier meadows, and it was quite interesting to see how the species changed  as one hiked inward from the beach dunes.

Image 2. Panicum amarum

In the first and outer layer (the beaches), the two main grasses were Ammophila breviligulata and Panicum amarum. Both are dune building species, and A. breviligulata especially is crucial in creating the huge dunes that protect beaches. It is the dominant dune grass along the northeast coast, and I was familiar with it from my trips to the beaches in New Jersey. 

The two species are also easy to tell apart, with A. ammophila having very thin leaves, while P. amarum has much wider and bluish green leaves. You can clearly see this in Image 3 below.

Image 3. Ammophila breviligulata (left) and Panicum amarum (right)

Their inflorescences are very different as well, as you can see in Image 4 below. A. breviligulata has a whitish spike like inflorescence, while P. amarum has the typical Panicum type spikelets,

Image 4. Ammophila breviligulata (left) and Panicum amarum (right)

As I continued hiking inland into the marshes I came upon the second layer, which is actually composed of several sublayers (see Image 5 below). The area of the marsh closest to the sea (the low marsh) is inundated daily and has higher salt concentrations, and this area was dominated by Sporobolus alterniflorus (Spartina alterniflora). The so-called "high marsh" is farther away, is not inundated all the time, and is less salty. Here I found Sporobolus pumilus (Spartina patens) and the graminoid Juncus roemerianus, which is in the rush plant family and is NOT a grass. 

Image 5. Marsh

It was fairly easy to tell the two grass species apart. S. pumilus has wavy looking blades that look quite beautiful and distinctive. In the image below (Image 6) the species looks almost like a nice soft fluffy lawn.

Image 6. Sporobolus pumilus (Spartina patens) in foreground (NJ pic)

Sporobolus alterniflorus is more erect in form, and it forms the vast bulk of the vegetation that people associate with marshes as they drive towards the beach. The geometric shapes of their vast stands was quite pleasing to the eye, and I spent some time taking various artistic pics of the scenery.  

Image 7. Geometric stands of S. alterniflorus (S. alterniflora) in the background

I even found flowerheads on some of the nearby specimens. The inflorescences were spike-like, with white anthers dangling out from the flattened spikelets and looking quite grub-like.

Image 8. Inflorescence of S. alterniflorus (S. alterniflora)

Beyond the marsh layer was a forested area, but also pockets of large meadows. This most inner layer is surrounded by the beaches and marshes, and I was astonished to find some species that I would never associate with islands. 

Next to the trail were rows of what I believe were Schizachyrium scoparium (little bluestem), and behind them the beautiful panicles of Panicum virgatum (switchgrass) waved in the breeze. Farther back were dense stands of the invasive Phragmites australis (common reed), which also was present in the high marsh.

Image 9. Meadow layer with a series of grass species

It was an amazing thing to be surrounded by such grasses, when just a few minutes away was marshy waters. But unfortunately, the drier landscape, combined with the disturbance regime due to human activity, has also introduced invasive species to the area. I found dense pockets of Microstegium vimineum (Japanese Stiltgrass) in some of the trails, the silvery lines on the upper surfaces of their leaves the most distinctive sign of their presence.

Image 10. Microstegium vimineum

Nevertheless, I really enjoyed visiting and hiking the short trails in the island, and I loved the structured layering of these major grass species throughout the area.

If you ever visit one of these barrier islands, do keep an eye out for the plants around you. The narrowness of such areas make it possible to go from one ecological region to another with just a short walk.

Flowering at the Crabbing Bridge: Sporobolus alterniflorus at Cheesequake State Park

I've already done several posts on Cheesequake State Park, and how it is notable because it lies in the transition zone between two different ecosystems, and harbors organisms that are native to both south and north New Jersey. It is also interesting to me because it encompasses a salt marsh, and is the home to several grass species, each of which is specific to a particular portion of the salt marsh.

Phragmites australis looking out over Hooks Creek Lake

The place is also a great hiking location, with well-marked trails that are wide and clean. Although there is no high viewpoint in the trails that we've done,  there are various stops at the edges of lakes and ponds. The facility also has a sandy beach that fronts Hooks Creek Lake, and various lookouts that survey nearby marshlands.

(PA) Phragmites australis, (SA) Sporobolus alterniflorus, (SP) Sporobolus pumilus near the Crabbing Bridge

We went there again today to hike, and I spent some time in the Perrine Road Trail, in the general vicinity of the Crabbing Bridge. This where one can see all 3 major grass species in the area (see image above). The invasive Phragmites australis (PA) occupies areas close to the  eastern end of the extended "walkway", with Sporobolus pumilus (SP) next to it, while the low marsh species Sporobolus alterniflorus (SA) is situated close to the water itself.

S. pumilus in front of P.australis stand

It's fairly easy to distinguish the three, with P. australis being much taller than the other two, the darkish flowerhead rising high up in the air and usually drooping to one side. S. pumilus beside it is much shorter, the long thin leaves close to the ground to form graceful clumps.

View of S. alterniflorus from walkway to Crabbing Bridge 

S. alterniflorus is intermediate in size, and occupies most of the area all the way to the actual Crabbing Bridge. When we were walking over the walkway, I noticed that many of the culms had flowerheads in bloom.

The inflorescence was a spike, quite pointed at the end, and mostly green in color. 

White anthers decorated the spikes and dangled out from the flattened spikelets. The anthers seemed quite long, almost sausage-like in shape. The term grub-like might even be used to describe it.

I spent some time taking pics of various blooms, which was not an easy task given that the walkway was perhaps only 2-3 meters in width, and due to Covid-19 restrictions I was trying to remain a bit far away from other passing visitors.

When people passed I tried to keep as close to the edge as possible, and the thought that I might overbalance and fall into the grasses was a constant thought in my mind. I can only imagine the commotion that would ensue if that happened.

Oh, the things we have to do for our passions ;-)

A Tale of Three Salt Marsh Grasses

The salt marsh environment is interesting because it is composed of several layered environments, each of which have their corresponding population of species. The low marsh is closer to the sea, and is inundated daily by the rising tide, whereas the high marsh is only flooded during times of exceptionally high tides.

I have noted the ubiquity of Phragmites australis in Cheesequake State Park in earlier posts, but two other grass species are present in force, especially around the crabbing bridge that is one of the main attractions of the park.

S. patens in front of P. australis. Individuals of the latter shoot up in the midst of S. patens.

If one stands on the crabbing bridge in early Summer and looks toward the south side, one can see the rather beautiful mounds of  Spartina patens (Sporobolus pumilus), while behind them loom the much taller forms of P. australis. S. patens exists in the high marsh areas, and cannot tolerate the higher salt concentrations and daily invasion of the tides.

S. alterniflora along the water edges

Looking to the North, which leads towards the sea, one can see the taller forms of Spartina alterniflora (Sporobolus alterniflorus) hugging the shoreline, with S. patens and P. australis behind them. This species is a low marsh grass, and can handle higher salt concentrations and flooding as the tides come in daily. Interestingly enough, the species comes in two alternate forms: a taller form that takes root along the marsh edges, and a shorter form which sit on slightly higher ground.

P. australis lines the edges of lakes and ponds in the park

Looming above both are the distinctive stands of P. australis, which also dominates the edges of the nearby Hooks Creek Lake and Perrine Pond.

P. australis of course has been deemed the villain in this tale. It is the invasive, and it supplants the native salt marsh plants in its relentless march towards dominance, forming extensive monocultures of 4 meter tall grasses. Its dominance then causes changes in both the biotic and abiotic environment around it.

For example, because of its faster growth rate and investment in below ground structures, the dense mats of decaying organic matter that accumulate in tidal marches dominated by P. australis actually elevate the wetland surface. The very dense stands of this species also slow the movement of tidal water, such that flooding is less deep and less prolonged.

P. australis blocks view of a pond

Interestingly though, there have been some studies that show there are some positives to the spread of P. australis in these environments, and that its negative effects may not be as disastrous as first feared. For example, various studies have shown that animal diversity in the P. australis marshes was just as high as in marshes dominated by the Spartina spp.

P. australis looms behind a wading egret

In addition, P. australis provides some benefits that the Spartina spp. do not. Its ability to sequester carbon is significantly greater than the other grasses, a big plus in a world undergoing climate change. P. australis is also better in sequestering metals and other pollutants from the environment, including nitrogen, thus helping to prevent algal blooms. Finally, P. australis builds and stabilizes tidal marsh soils better than Spartina spp, another big positive in a world undergoing sea level rise.

So the next time you see dense stands of P. australis hogging a shoreline, don't immediately despair over the fate of that environment. Things may be more complicated than a simple black and white perspective on such invasives.

Spring comes to Cheesequake State Park's Phragmites australis

I know that P. australis is an aggressive invasive that has displaced native plants and spread unchecked throughout the country.

But this grass still forms impressive stands, and their dried inflorescence look quite enchanting to most casual observers.

Dense stands of P. australis look bi-colored due to new green growth at lower end. New growth also in right foreground.

We hiked Cheesequake State Park in New Jersey, and it was interesting to see the new growth of this species rising out of the tall light brown remnants of the grass from last year.

The new growth was dwarfed by the much taller dried grass, but its vibrant green coloration made it stand out anyways. In fact, when looking at a monoculture of P. australis from the side, the difference in color made it seem as if the grass was bi-colored, with a green lower half and a light brown top!

P. australis is abundant in the park

The park itself was very well-maintained, with well-marked paths and even long wooden boardwalks that allowed you to traverse the boggy low-lying ground that occupied parts of the park.

P. australis grows abundantly in the lower and marshy areas, and forms dense impenetrable stands along the sides of paths and around some of the park lakes and ponds. It is however absent from the higher areas of the park, as well as directly below the shaded tree canopy.

I can only surmise that eradicating the invasive grass from the park would have cost too much, though it might be a small consolation to park managers that visitors probably found the dense stands of grass an impressive sight.

New green growth rises under the shadow of last year's dried remnants

Phragmites australis in New Jersey

One of the most conspicuous invasive grasses in the Garden State is Phragmites australis.

This grass can be up to 4.6 meters tall, and it is a lover of wet areas, occurring in such places as tidal and non-tidal wetlands, brackish and fresh-water marshes, river edges, shores of lakes and ponds, roadsides and ditches.

There are 3 forms of the species, with the invasive European form being the most aggressive. This form probably entered the USA in the early 17th century and is now one of the most problematic invasive plants in the country.

The two others are subspecies and are considered native to the country. P. australis subspecies americanus also blankets the USA, whereas P. australis subspecies berlandieri is restricted to the gulf states and south to Mexico.

The way to determine which subspecies you have is fairly straightforward. Click here to read a PDF of this, or this youtube video might help:

Like many other invasive grasses, it outcompetes native vegetation and forms dense monotypic stands. P. australis is particularly noticeable along the highways in New Jersey, where the tall grasses line highways.

P. australis on side of highways

You can even see stands of the invasive grass in the highway median!

P. australis along median of highways

It also forms dense stands along waterways, crowding out native species.

P. australis along waterways

This species has also recently been investigated as one of the factors that promote wildfires, along with other invasive grasses such as cheatgrass (Bromus tectorum), cogon grass (Imperata cylindrica), buffelgrass (Cenchrus ciliaris) medusahead grass (Taeniatherum caput-medusae), and others (Fusco et al, 2019).

One interesting thing is that even though it has a lot of negatives, there have been studies that show there are some advantages to the species.

For example, its ability to sequester carbon is significantly greater than the other grasses in its area, a big plus in a world undergoing climate change. P. australis is also better in sequestering metals and other pollutants from the environment, including nitrogen, thus helping to prevent algal blooms. Finally, P. australis builds and stabilizes tidal marsh soils better than neighboring plants, another big positive in a world undergoing sea level rise.

In the end, given its competitive abilities and ubiquity, we will probably have to live with it wherever it has already managed to gain a strong foothold. Ensuring that P. australis does not continue spreading to other non-infected sites has to be our primary goal instead.

References:
 
Emily J. Fusco, John T. Finn, Jennifer K. Balch, R. Chelsea Nagy, Bethany A. Bradley. Invasive grasses increase fire occurrence and frequency across US ecoregions. Proceedings of the National Academy of Sciences, 2019; 201908253 DOI: 10.1073/pnas.1908253116

Autumn creeps on Cheesequake State Park

In October 2019, I visited Cheesequake State Park in Matawan/Old Bridge, NJ, which is notable because it lies in the transition zone between two different ecosystems, and harbors organisms that are native to both south and north New Jersey.

Microstegium vimineum (Japanese stiltgrass)

One of the more interesting things I noticed was that the carpets of invasive Microstegium vimineum (Japanese stiltgrass) that covered some of the forest floor had turned golden in color, and made the scenery seem quite magical and surreal.

Microstegium vimineum (Japanese stiltgrass)

But perhaps the highlight of the place for me was the Crabbing Bridge, a long boardwalk that passed over the marshlands in the park and was surrounded by tall grasses.

Crabbing Bridge on Sept, 2018

Birds flew and waded in the grasses that stretched into the distance.

Sporobolus pumilus  (saltmeadow cordgrass)

Although they were too far for me to make an ID easily, at least some of them were Sporobolus pumilus  (saltmeadow cordgrass), which was previously named Spartina patens.

Sporobolus pumilus  (saltmeadow cordgrass)

Also present in the park was the invasive Phragmites australis, which is one of the more ubiquitous grasses in the state, and which I will be discussing in a separate future post.

Phragmites australis