kreischer hill rare plant community

Protectors of Pine Oak Woods · Current Issues · Kreischer Hill Rare Plant Community

Forest Restoration
By Don Recklies, Naturalist

Forest Restoration July 17, 2010

As had been predicted, Saturday’s restoration (Protectors’ 169th) was hot and humid, although the temperature under the canopy was considerably less than the 94 degrees we experienced before gathering our tools in the parking lot at High Rock Park. Chuck came over to open the tool storage shed, and then had to return to his plumbing (there’s a tough choice: to fix the toilets or to pull vines!), leaving only the three of us, Elaine, Norm and myself, to trek the Greta Moulton Tract on the Green trail close to Manor Road. There we spent a sweaty few hours cutting twining vines from the trees and uprooting Multi-flora Rose.

We have been to this section many times before: it was one of four areas that we regularly visited when I first joined Protectors of Pine Oak Woods, and at least twice a year we would come sometimes to plant trees and shrubs but mostly to remove Oriental Bittersweet and - especially - Japanese Honeysuckle. The area was too much degraded by invasive plants to fully clear with success, but we had managed to save many saplings by repeatedly removing the strangling vines and had cleared a small area of Multi-flora Rose. The herb layer, however, remained almost all Japanese Honeysuckle which had successfully shaded out everything but the invasive rose and the Oriental Bittersweet. Three years ago, the Department of Parks judged that drastic measures were needed for any success and treated the area with herbicide, killing almost all growth above-ground (including, alas, several of our saplings), and much of the below-ground roots.

When we returned a year later, Honeysuckle had begun to re-sprout and thorny rose shoots had sprung up from surviving root stock. Few of the surviving shrubs and saplings required attention, so we concentrated upon clearing woody vines from the trees on the border of the treated area and pulling the re-sprouted rose. Because of the herbicide, there were many fewer rose sprouts to tackle, and those that re-sprouted were relatively easy to pull up with a weed hook, possibly because the root system had been weakened and damaged by the action of the herbicide. On this month’s restoration, about a year and a half later, the situation was not much different; there were a few woody vines to remove from trees in the treated area, and more re-sprouted rose to uproot. Honeysuckle has again covered the ground, not as densely as before, and thankfully there is some competing Virginia Creeper. We did what we could.

After the restoration a few other members joined us for a short walk in the vicinity of High Rock Park. One of those who joined, not able to take part in our restoration sessions, had decided to do some restoration on her own, and I had recently heard of the results of her work from the High Rock Park supervisor. On a recent walk at La Tourette, Sarah-David was appalled at the dumped tires lying about and buried at the western end of the new bike path. She asked to whom she should report them and what she could do about them, even volunteering to gather them herself if the Department of Parks would then remove them. Her offer was apparently accepted, and she had gathered over a hundred tires and some other debris from the vicinity of the bike path, stacking them alongside the path. I have been told these have recently been removed by park workers. I’ve excavated tires in the past, and I can only say I am impressed and thank her on behalf of all of us who want to enjoy an unspoiled Greenbelt.

When we started our walk we encountered by chance a woman of Korean descent with her two young children out for a walk in the woods, and they joined our small group to make a circuit of Loosestrife Swamp. I am completely hopeless at estimating the age of children, but I guessed them at three and four years old, and what little explorers they were, peering into the marsh and examining random leaves for bugs! Their mother was no slouch herself in the sharp-eye department, spotting a Spring Peeper on a loosestrife leaf in the marsh. (Although we call it Loosestrife Swamp, it’s technically a small marsh. Swamps are wetlands inhabited by trees, whereas marshes are unshaded wetlands.) I’ve stood for half an hour beside the marsh in the spring trying to find some of these frogs which were singing no more than a few feet away, but she spotted this silent one even though its pale green silhouette was close to the color of the leaf itself. This frog was accommodating enough not to jump away even though a stick was used to point it out for those of us who still couldn’t make out its shape in the green.

The loosestrife here, as no doubt you are aware, it not the invasive Purple Loosestrife (Lythrum salicaria) which has overgrown many wetlands in the northeast, but is instead a native plant, (Decodon verticillatus). It is another member of the loosestrife family, sometimes called Swamp Loosestrife or Water Willow because of its arching, drooping stems, although it is not a willow at all. It extends itself across the swamp by means of those arching stems, growing new roots from the stem tips when they droop back into the water and soil of the marsh. At the northwest corner of the marsh, where new trees were planted this past It’s My Park Day, the shrubby Loosestrife was covered with viney, yellow-brown nets of a parasitic plant called Dodder.

Dodder (Cuscuta sps.) climbs on its host plant much like Morning Glory on a trellis, and indeed for many years was considered to be in the same family, but had been split into its own botanical group because of certain inconspicuous characteristics of its small flowers (DNA analysis, however, frequently disturbs traditional botanical groupings, and I read that current authorities contemplate grouping many of the Dodders back into the Morning Glory family). It is a true flowering plant, reproducing by seeds, but is also an obligatory parasite and cannot survive on its own, even though many Dodders are capable of producing a small amount of chlorophyll, inadequate to keep them alive. If you should look closely at the vine you may discern small scales, which are all that remain of its leaves. Its seeds can lie dormant in the seed bank for several years until conditions for germination are right. The seeds eventually sprout small vines, anchored by small roots that serve more for mechanical support than nourishment, that twist about seeking a host. If a variety of plants are present, the vines tend to grow toward suitable hosts, but it was a somewhat a mystery how the seedlings knew where those hosts might be located. Recently researchers bent on finding ways to control the plant found that Dodder can recognize and follow subtle airborne chemical signals emitted by their hosts. These small vines have only a few days to find a suitable host before they exhaust their resources and die. If they encounter an acceptable host, they twist about it, embracing it closely. Wherever the vines are in close contact with the stem of the host plants, they develop tiny lumps, and some of these in turn become tiny rootlets, called haustoria, which penetrate into the hosts’ conductive tissue. Soon the Dodder derives all its nourishment from the host, and the Dodder’s roots wither away severing its connection with the ground. (http://www.swarthmore.edu/NatSci/cpurrin1/dodder.htm might be of interest) Dodder is only one of many parasitic flowering plants lacking chlorophyll; worldwide there are estimated to be several hundred different kinds, and no doubt there are many more waiting to be discovered. Among those we see in our woods are the brown, spindly Beechdrops (Epifagus virginiana), parasitic on the roots of Beech, and stalky, yellow, brown-tinged Squawroot (Conopholis americana), which is parasitic on the roots of oaks.

To me, it seems we have a certain learned aversion to the parasitic life-style; a proper plant should after all earn its keep, not free-load on other hard-working, chlorophyllous relatives! (Certainly a chauvinistic attitude in light of the fact that we are ourselves parasites; our existence is based upon green plants that photosynthesize foodstuffs from water, carbon-dioxide and sunlight, and, as an excretory by-product, provide oxygen for the very air we breathe. No matter who eats what, the base of the food chain is anchored in plants with chlorophyll.) However, we must admit that the parasitic lifestyle has its advantages: if one climbs on other plants and uses them for support, resources that would have gone into producing stiff stems can be employed instead in the production of blossoms and seeds. Likewise, if one doesn’t have to produce one’s own chlorophyll based food factories, those resources too can be dedicated to producing more seed, and is that after all the plant’s ultimate objective.

Dodders can produce a lot of seeds, and in parts of the country - not to mention in your own garden - can become serious agricultural pests. They can accommodate themselves to many different hosts, and when growing in fields of grain often contaminate the harvest with their seeds. Because their conductive tissues are in intimate contact with the tissues of the host plant, it is usually not feasible to combat them with herbicide, and attempts to remove them from agricultural fields by letting the fields lie fallow for several seasons often fail because the seeds of the Dodder remain viable in the soil’s seed bank for many years. (There is one report of 60 year-old Dodder seeds from a herbarium germinating successfully, but in the soil they don’t last nearly that long.) In good growing conditions Dodder can actually bury their hosts, as can be seen in a small loosestrife swamp in the northern section of Wolfe’s Pond Park close to Hylan Boulevard. However, it isn’t a good survival strategy to smother the host unless the Dodder has already blossomed and is going to seed!

On the western edge of Loosestrife Swamp we paused to examine another parasitic plant, the Indian Pipe (Monotropa uniflora), sometimes called the Ghost Flower or Corpse Plant (On a hike in northern New Jersey one of our members heard these plants called “Ice Flowers”, a very descriptive name although the season is all wrong!). The pallid stems of these waxy white plants burst up through the leaf litter and, with a single tightly rolled flower nodding from the top, look very much like ceremonial pipes of northeastern American Indians stuck stem first into the ground. Indian Pipes are often noticed during our summer walks, and those not in the know assume they are some kind of fungus. They are, however, another true flowering plant that lacks chlorophyll, and therefore cannot manufacture its own food. Just like more familiar flowers, the blossoms produce a nectar that attracts pollinating insects, mostly small bees, and their hung-down, nodding habit probably serves to keep rain from washing away that nectar. Once the flowers have been pollinated, they straighten up and stand at attention, the blossom becoming a knobby seed capsule cupping the maturing seeds until they are shaken out during the fall and winter. In winter we see them as erect, blackened, knobby sticks. It’s hard to believe, but botanists relate these ghostly pipes to the blueberries.

We often found Indian Pipe sprouting about Beech trees, and once assumed that they were parasitic upon the Beech roots, but it turns out that their nature is more complicated than that. Over a century ago botanists found that the roots of the Indian Pipe were covered with fine fungal filaments and they began to suspect that the source of the Indian Pipe’s food wasn’t derived from the nearby trees but from the fungi growing in the soil. It was soon recognized that the mushrooms that fruited from these mycelial threads were our familiar Russulas and Lactarius, the reddish, crumbly mushrooms and latex-bearing milkcaps that would be very common now if the weather hadn’t recently been so hot and dry. Several years ago it was discovered that Beech and many other forest trees have a commensal relationship with these same fungi in the soil. The fine fungal threads (which are actually the body of the mushroom; the cap above ground is just the “fruit”) intimately intertwine with the roothairs of the trees, covering the roothairs like thin, netted gloves, and penetrating them with - you guessed it - haustoria. This type of mushroom relationship is called mycorrhizal; the tree produces carbohydrates that nourish the mushroom, and the mycelial threads of the fungal partner extract mineral nutrients from the soil that the tree itself would be unable to extract and supply them to the tree. Both partners benefit from the relationship. Indeed, it is now thought that in the plant world such mycorrhizal relationships might be the rule rather than the exception, and that the fungi in this way serve as much more than simple de-composers of dead wood in the ecology of the forest.

So now it seems that the Indian Pipe is parasitic on two organisms; it is parasitic directly upon fungi in the soil, and indirectly parasitic on forest Beech trees through the intermediation of the fungi. This theory was verified by providing a tree with carbon dioxide containing a radioactive carbon isotope and tracing the flow of radioactive compounds first from the tree to the fungus and then from the fungus to the Indian Pipe. But we are still far from a complete understanding of these tangled natural relationships. We assume that the Indian Pipe is a simple parasite which has managed the neat trick of parasitizing two other organisms at the same time, but must keep in mind that perhaps it’s not so simple and that the Indian Pipes may in turn confer some benefit to the Russulas and other mushrooms that we yet know nothing about.

The concept that threads of fungal mycelium are to transfer carbohydrates between plants is interesting indeed; if they can transfer carbohydrates, why not other chemicals as well? We know that many plants communicate chemically with other plants. Some, when suffering insect attacks such as caterpillars munching on their leaves, produce toxic compounds distasteful to the caterpillars and begin to emit volatile chemicals that attract wasps that prey on those caterpillars. The chemicals are also a signal to other plants in the vicinity which in turn begin to produce greater amounts of their own distasteful compounds, even if they have not yet suffered insect browsing. The more that research is done, the more we learn that some plants are able to communicate among themselves in ways that we wouldn’t have even dreamed about. I don’t think it’s too far-fetched to consider that the net of fungal mycelia in the forest might also function as a kind of underground telegraph between plants. Paul Stamets, who might be described as an extreme fungal enthusiast, develops this concept in his recent book Mycelium Running, in which he hypothesizes that this underground network might be conscious in its own way, and he describes it as “Nature’s Internet.” That’s a little extreme for me, but the concept is interesting.

At the end of our walk we paused in the shade at one of the ponds along the Red-Dot loop trail south of High rock Park to spy on the dragonflies and occasional turtle. The turtles were too wary for us, however, and slid into the water from their sunning logs at our approach, but the water was alive with frogs, breeching like small whales up through the duckweed blanketing the pond to snatch an occasional low-flying or perching insect. I wondered if they might be green frogs, but despite their constant activity we were always looking at the wrong spot and they were much too quick for us to verify their identity. That was enough for us, and we returned to the High Rock parking lot by following the trail east on the asphalt drive that extends from Altamont Street and then back up the hill. On the way we noted many Devil’s Walking Stick saplings lining the side of the road, and mentally marked them down for a future Forest Restoration.

DfR