Photo: New York Ironweed, Matt Bright
Audubon at Home Ambassadors held their annual Potluck Ambassadors’ Brunch at the Fairfax County Government Center on March 19—a welcome gathering, their first in two years. Thirty-two Ambassadors attended, and enjoyed a presentation on “Earth Sangha’s Native Plant Compendium, Plant Communities and Native Plant Selection” given by Matt Bright, Conservation Manager for Earth Sangha.
Plant communities are assemblages of plant species that grow in a particular habitat and interact with each other, wildlife, and the environment around them. Knowing the features of the landscape and the dominant vegetation allows us to predict what other plant species “belong” there, and provides a basis for making plant selections. Plant communities are a natural extension of “right plant, right place.”
New York Ironweed, Matt Bright
A plant community is simply the native plants that tend to grow together in any given habitat. So, for example, different plant communities are found on a steep dry slope, or in the floodplain near a stream, or in an open area. Often the assemblage of plants present is governed by topography.
Conserving and restoring plant communities allows us to protect plants and wildlife in ways that mirror natural environments. Restoring common, dominant native plants that are the ecosystem drivers can create ecological uplift—the drivers will create the conditions that bring along rarer, passenger species that need those conditions to thrive and reproduce.
Plant communities can also help guide choices not only about what to plant, but how much. For example, a floodplain forest often has a dense herbaceous layer, while a mesic to dry forest understory is often sparse, with large areas of leaf litter. The density that occurs in nature may not match gardening conventions, such as planting a single specimen surrounded by 18” of mulch. Planting for succession will create a multilayered understory, with varying age classes of mature canopy trees and young saplings.
Plant communities can provide far greater benefit over the complete life cycle of wildlife species than focusing narrowly on a single species. For example, many people have learned that milkweeds are essential for Monarch caterpillars. While they are necessary, Milkweeds are not sufficient. They are actually relatively poor insect hosts: Goldenrods are much more important late-season nectar sources for migrating Monarch butterflies, and as hosts for specialist bees. A diversity of species within a plant community supports a greater diversity of wildlife.
Matt Bright stressed that ecological value is in the details. An example is leaf litter, which provides essential habitat to many species. He cited results from a recent study that shows large declines—by a shocking two-thirds—in lepidoptera populations when leaf litter is removed. This confirms Audubon Ambassadors’ advice to their clients to “leave the leaves!”
Reconnecting areas has tremendous ecological value. Matt cited results from an 18-year experiment showing that creating even narrow corridors between areas of habitat resulted in fewer extinctions, faster recolonization by native plants, and 14% greater biodiversity in connected sites than in isolated ones.
Matt provided good, practical (and work-saving) advice for prospective native gardeners and restorationists:
Focus on dominant species that will create conditions to create ecological uplift. For a first round of planting, he suggests sticking to common, generalist species, which have more “right places” and are more frequently the right plant that will establish more quickly. Generalist plants often support specialist wildlife.
Leave healthy areas of intact habitat alone. Remove invasives, and before replanting wait to see what regenerates from the seed bank. Volunteer plants are free, and can guide you towards what to plant in the future.
Although plant communities may seem daunting, Matt argued they are actually less work than picking and choosing plants individually. He provided several sources of guidance:
Earth Sangha Native Plant Compendium: You will learn a lot about native plant communities from this text-heavy website, which provides useful advice on high-value generalist canopy trees, understory trees and shrubs, and plants for wet and dry meadows.
Plant NOVA Natives Natural Plant Communities made easy is perhaps the most comprehensible site, which offers practical advice and will help you understand the concept of plant communities.
Natural Ecological Communities of Northern Virginia, by Glenn Tobin—this site is more oriented to the quantitative user. Tobin has begun developing a scheme to help identify plant communities.
Department of Conservation and Recreation, Natural Heritage Program—this site provides descriptions of each of the natural communities of Virginia, as well as its key plant species. Very data rich. Definitive and technical.
Nature Serve Explorer—this site uses different common names for the communities than the DCR site.