Monday, February 27, 2017

In Search of Green

We're on the cusp of Spring. The temperatures are rising. The birds who overwintered here are brushing up on their vocal skills. The Skunk Cabbage and Harbinger of Spring are blooming. The daylight period is getting longer. The amphibians are attempting to breed. The reptiles are leaving their hibernacula. Nature is preparing for a new season.

But I can't wait. I think it's because Winter never really came to Athens, Ohio. I love Winter, but I want it to be Winter when it's Winter. Sure, it got kind of cold on some days, and sure there were a few instances of flurries or maybe an inch of snow that lasted a day, but we didn't have any stretch of time where it felt like a proper Winter. So I gave up hoping for a real Winter and have since been impatiently waiting for Spring. Over the past week I couldn't wait any longer, so I ventured out to some nearby parks in search of some greenery to scratch my Spring-itch.

Riddle State Nature Preserve
The view from the Sourwood Trail in Riddle State Nature Preserve.
First up, Sells Park and Riddle State Nature Preserve. On the northeast side of Athens sits a system of six contiguous parks owned by various agencies. On the westernmost end of this system sits Sells Park, with Riddle State Nature Preserve located just next door. Several trails crisscross these two parks, which protect a series of mature forested ridge tops and ravines. Riddle State Nature Preserve is well-known for protecting one of the few old-growth forests remaining in Ohio, but the section I hiked around (and that is pictured above) is only a mature secondary-growth forest.

Although we often think of Ohio forests turning various shades of brown during the Winter months, there are a great deal of herbaceous plants which remain green. The little green leaf above is one such example. This is the leaf of a Cranefly Orchid, Tipularia discolor. The Cranefly Orchid is one of the 46 species of orchid which have been recorded in Ohio. It has a rather strange range in Ohio; it can be commonly found throughout the southern third of the state, but can also be found in several counties centered around the Cleveland area. This range, however, appears to be changing; the Cranefly Orchid seems to be slowly expanding northward throughout much of its northerly limits. In the coming decades, there might be populations of this orchid in central Ohio.

Tipularia discolor leaf
Cranefly Orchids have a unique bi-colored leaf. The topside is green, but if you flip it over you'll be rewarded with a deep purple hue. This leaf does more than simply looking cool to plant lovers. But before we get to that, we have to understand what the function of a leaf is. The main function of a leaf is to produce food in the form of glucose for a plant. It does this through the process of photosynthesis. There are three main ingredients when it comes to photosynthesis: carbon dioxide, water, and sunlight. Those last two ingredients, sunlight and water, are rather limiting for a plant. A plant needs a lot of sunlight and a lot of water to make enough food to grow. As a result, it makes the most sense for plants to grow during the warm months from late Spring to early Fall, as the period of daylight is longer and there is normally plenty of water available. But this creates other problems. Imagine you're a tiny herbaceous plant on the forest floor. You need sunlight to make food for yourself, but the trees overhead are hogging most of it. The light that finally reaches you is just a tiny portion of the light initially available. Most of these herbaceous forest-floor plants simply make due with this problem, but some plants have found ways around it.
Cranefly Orchid Ohio
The leftover flowering stalk of a Cranefly Orchid with seed capsules.
When Winter comes around, many plants decide to stop photosynthesizing and lose their green leaves. With only a few hours of daylight to use, and water not as readily available, it doesn't make sense to photosynthesize. So the forest suddenly becomes a lot less green. But this does something else: with the trees lacking leaves, way more sunlight now reaches the forest floor. In comes the Cranefly Orchid. The Cranefly Orchid evolved a solution to this light competition problem long ago. Instead of fighting for a little sunlight during the Summer when all the other plants are competing as well, the Cranefly Orchid decided to simply change the time of year when it grows a photosynthetic leaf.

Cranefly Orchid flowers in the summer like many other species (as that's when insects are out to pollinate the flowers), but it doesn't grow a leaf until the leaves of most other plants are beginning to change late in the Fall. By the time the leaf is fully grown, the canopy is open and the Cranefly Orchid can exploit all of the sunlight that now reaches the forest floor. As I mentioned before, this is a hard strategy for most plants, which is why we don't commonly see this strategy. However, nearly all of the patterns we see in nature are a result of the interplay between costs and benefits. For the Cranefly Orchid, the benefits of trying to photosynthesize during the winter outweigh the benefits of trying to photosynthesize during the Summer, even when the plant factors in the costs associated with photosynthesizing through the freezing temperatures and shorter photoperiod. As Spring ramps up, this leaf will break down and the rest of the plant will then begin to send up a stalk for flowering before repeating the cycle all over again.

Strouds Run State Park
Of course, seeing the Cranefly Orchid made me want to see the other two orchid species around Athens that have leaves present during the winter. The Sun was going down though, so I went home and decided to try again the next day. After classes ended that next day, I traveled out to Strouds Run State Park, yet another park within the larger system bordering Athens.

Puttyroot Orchid leaf

First up, Puttyroot Orchid, Aplectrum hyemale. Puttyroot is another orchid which utilizes a strategy like that of Cranefly Orchid. Toward the end of Fall, the underground part of the plant sends up a single leaf in order to capitalize on the open Winter canopy and avoid the competition associated with sunlight during the Summer. This leaf will live through the Winter months before breaking down by mid-Spring. Right after the leaf disintegrates, the plant will send up a flowering stalk.

Aplectrum hyemale leaf

The overwintering leaf of a Puttyroot Orchid is quite stunning. They're pretty large, and hard to miss if you're looking at the plant life within a forest. This species is more widespread in Ohio, with the core of its range being in the southern and northeastern portions of the state, with scattered populations elsewhere in the central and northwestern portions. The Puttyroot Orchid is an inhabitant of moist woods, where it can be found along forested floodplain terraces, the bottoms of ravines, low to mid level regions of forested slopes, and sandstone canyons. The individual pictured above was part of a colony found underneath a sandstone outcrop on a rather-seepy forested hillside.

Downy Rattlesnake Plantain Ohio
Of course, this post wouldn't be complete without talking about one of my favorite orchids, the Downy Rattlesnake Plantain, Goodyera pubescens. Unlike the previous two species I've talked about, the leaves of the Downy Rattlesnake Plantain are present year-round. This orchid species can be found throughout the Allegheny Plateau region of eastern Ohio, where it grows on dry or moist upland portions of the widespread hills. In fact, this orchid can be very abundant in the appropriate habitat, and the individuals pictured above were just a few of the dozens I saw over the course of 2 hours at Strouds Run State Park.

Goodyera pubescens leaf
Downy Rattlesnake Plantain is one of my favorite orchids for two reasons. First, it was the first species of orchid I ever saw in the wild. Second, the leaves are phenomenally beautiful and eye-catching. Even a person not that interested in plants would find themselves stopping for a closer look if they came across a population of this orchid while out on a hike.

As I write this, the weather is chilly and rainy. This is a far cry from the previous Friday, where Ohio teased us all with Spring-like weather in the high 70's. As we sink back into a more seasonable weather pattern, I can't help but continue to impatiently wait for Spring to rev up in earnest. Thanks for reading!

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