Getting to Know Our Woods through the Seasons - Springtime Insights

Posted: April 26, 2017

In each season, we can gain new insights on how the woods function and what kinds of stewardship activities may be needed.

With the arrival of spring, many of us go into the woods with a specific mission in mind, whether it is looking for the excitingly elusive morel mushroom, photographing ephemeral woodland flowers, or watching for returning migratory birds. In search of our own favorite spring harbinger, it can be easy to overlook the bigger picture and the story this picture tells about a woodland. In each season, we can gain new insights on how the woods function and what kinds of stewardship activities may be needed.

Many people focus on learning to identify trees primarily by leaves. Tree flowers and the timing of flowering are also useful features for identification, helping to distinguish between different species of the same genus of tree. Many guidebooks include flower illustrations. An especially helpful resource for visual learners is George W. D. Symmond’s The Tree Identification Book, published in 1958. In this book, photographs of tree flowers are organized in the general order of when they bloom.

Right now across central Pennsylvania we see some trees displaying pale green shades flowers that are recognizable as maples. But which species? The very-common red maple can be ruled out since those blooms are red or yellowish-red and have already passed peak bloom time. In your own woodland, you may have previously identified one of these trees as a sugar maple. A closer look at the pale green flower, though, may lead to a corrected identification—the non-native Norway maple. Sugar maple flowers are clustered on long pedicels (stalks) that dangle, resembling clumps of green tinsel on the tree. The flowers of non-native Norway are on shorter, upright pedicels. This closer examination of tree flowers can also help to identify desirable tree species in your woodland that may not have been noticed before because there are few in number. Flowers can also help to reveal a tree in your woods that needs assistance if it is to survive—a hackberry within a thicket of bush honeysuckle, for example.

In many tree species, the flowers emerge before the leaves. This is an adaptive strategy, enabling a tree to put its energy (carbohydrates stored in the tree over the winter) into reproduction—producing the flowers, which will in turn produce seeds. Flowering before leaves emerge or are fully grown helps in tree pollination, allowing more open space for pollen and pollinators to move from flower to flower. Some species, including oaks, hickories, elm, and birch, are pollinated by wind. Other species, including yellow poplar, basswood, locust, cherry, and magnolias, are pollinated by insects. As with the flowers of non-woody plants, tree flowers of different species have different morphology (shape) to attract particular pollinators—bees, beetles, flies, wasps, butterflies, moths. Maples are wind-pollinated but they also may benefit from pollination by the bees and other insects that visit the flowers. Binoculars are a great way to get a view of flowers that are out of reach and the pollinators that visit them.

A broader view of a woodland in early spring can give a general sense of how many different tree species grow there. With the help of the flowers and without the leaves, it is easier to get a sense of how many other individuals of a tree species are present in a stand of trees or throughout the woodland. Having many individuals of the same species of our native trees is not necessarily a concern. On the other hand, this broad view may reveal an undesirable non-native species, which will negatively affect growth of native species, and may dominate a woodland. For example, Norway maple—identified both by flowers and by leaves that emerge sooner than sugar maple—may be common in a stand. Similarly, if the broad view of the understory shows lots of shrubs which have developed leaves before most everything else in the woods, this usually indicates non-native invasives.

This simple exercise of taking the broad view of the woods to get a sense of whether there are a few species or many species has significance beyond mere observation. Foresters agree that a woodland is most resilient to threats from insect pests or disease or extreme weather when it has diverse species and ages of trees. Enhancing native tree and plant diversity involves managing light in woodlands, which is done by creating openings. Growth of tree species other than those present in the canopy, and growth of new age classes of trees (for example, seedlings, saplings) benefit from sunlight reaching below the canopy. In addition to openings being important to fostering age and species diversity in the woods, these openings also benefit pollinators. In 2016, researchers from the Southern Research Station of the U.S. Forest Service reported on their study of pollinator abundance in seven types of forests. Their findings showed that the abundance and diversity of pollinators was greatest in forests that had more openings in the canopy.

Adding to the other springtime observations suggested here, this season is also ideal for observing how light availability changes as leaves in the canopy emerge. This can help further decipher whether a woodland may benefit from new canopy openings to enhance native tree and plant diversity.
Does sunlight still reach the understory and forest floor when the canopy trees have leafed-out? If not, there may be need and opportunity to create some openings in the canopy to allow younger trees to establish and grow.

Any decisions to create new openings in the forest should involve careful thought about what other plants will take advantage of the openings. Clearly, if non-native invasive plants are nearby or already present in the stand, there is great risk that those undesirable plants commandeering increased light resources. Therefore, if you plan to change forest structure, it is critical to have a plan to address invasive-competitive plant species.

Springtime activities like these—learning to identify trees in a new way, observing and tracking how light in the woods changes as leaves emerge, and taking small ongoing steps to control populations of invasive plants—may sometimes feel inconsequential. To the contrary, every small effort we make in understanding what’s growing in our woods and thinking about how to foster variety in the species and the age of trees is essential and will contribute to greater overall impacts, especially if they are shared with family members, friends, and neighbors.