Plant Refugees

Many once-common plant species are today rare, threatened, or endangered. For millennia, they were the basic building blocks of rich ecosystems; now they are hardly remembered. Some are vanishing over huge former ranges. Other species survive well elsewhere but are losing much of whatever may have been unique about their local ecotypes. Today some of these species can be found in obscure habitats (that may indicate little about their former haunts).

Could they become common once again? Certain experiments suggest that they could.

Before we get to a slightly longer list, consider two species – as they were described by H.S.Pepoon in 1927.

Lathyrus ochroleucus (wild sweet pea, wood pea, cream vetchling, or pale vetchling) is listed as threatened in Illinois. Pepoon characterized this plant as “Common on hillsides, in open woods.”

How often do we see the wood pea in woods today? Very rarely. There are probably two reasons: 1) the lack of fire has made our woods too dark, and 2) badly overpopulated deer seek out this delicious ‘sweet pea’.

Wood pea once grew commonly under white and bur oaks with rue anemone, fire pink, large false foxglove, shooting star, two-flowered Cynthia, wood betony, Seneca snakeroot, wood rush, wood vetch, and other first-quality species. (Photo from Wikipedia)

Viola conspersa (or labradorica) (dog violet) is listed as threatened in Illinois. Pepoon characterized it as “very common.” I have three times seen it emerge when woods were thinned of trees making excessive shade. Mostly, these days, it’s found it wet woods – perhaps because shade from invasives is slowest to increase in very wet (or very dry) habitats. Wilhelm and Rericha list its habitats as “wet to dry-mesic woodlands" and include such associates in drier habitats as Penn sedge and bastard toadflax.

Violets hard to identify? Look at the stem (above). It shows a distinguishing character of dog violet. See how a main stem has many leaves and flowers branching off? In contrast, the common blue violet has no branching stems; the simple stems of every flower and leaf sprout directly from the root. 

As woods are restored, at least in some experimental cases, the full range of species that likely were part of the original community should be established. Some officials are reluctant to permit managers to restore now-rare or threatened species. Why should that be? If a plant was once common, what harm could come from giving it chances to become so again? Would its presence not likely help the whole ecosystem, as we try to provide the opportunity for it to restore itself to full health and diversity?

If authorization to restore a species is granted, that authorization often limits restoration of the species to “proper” habitats. Why be so concerned about this? Might it not seem a bit arrogant of us to insist that we know the full amplitude of former habitats? All restoration and natural area management initiatives are experiments. These experiments should be carefully documented. And at least on some sites, the experimenters should give free rein to let the plants sort themselves out.

For me at least, I find the need for species restoration increasingly compelling the more I review species on the refuges list. Details on seven more species are summarized below.

Pale Indian plantain (Cacalia atriplicifolia). Pepoon wrote: “Wooded hillsides. Common.” Today: Very hard to find original populations in woodlands.

Sanicle (Sanicula marylandica). Pepoon wrote: “Woods … common everywhere.” Today: Can be found in some savannas but in our darkening woods it has apparently been almost entirely replaced by clustered black snakeroot.

Smooth tick-trefoil (apparently Desmodium Dillenii and paniculatum in Pepoon). Pepoon wrote: “The common species … In open woodlands.” Now: Uncommon or missing in most woodlands.

Violet bush clover (Lespedeza violacea). Pepoon wrote: “Common on all dry soils.” Today: Rare enough that Swink and Wilhelm do not list it for Lake County, IL. But it showed up spontaneously in at least two Lake County savanna restoration areas, in one case, only after the burns started.

Wide-leaved panic grass (Panicum latifolium). Pepoon wrote:  Woods, common … An abundant, fine grass.” Today: A happy surprise when we occasionally see it.

Wild licorice (Galium circaezans). Pepoon wrote: “Woods common throughout.” Now: occasional or absent.

Wood vetch (Vicia carolina). Pepoon wrote: “Hillsides and dry open woods, frequent.” Today: I haven’t seen one in Cook County for many years.

These and hundreds of other refugee species deserve a natural and sustainable home.

We should not ill-treat these refugees. We have the ability to restore them to ecosystems that are recovering diversity and health.

When volunteers and staff launched the Somme Prairie Grove experiment in savanna and oak woodland restoration, we could find none of the species listed above. Now most of them are common or at least frequent at Somme. 

Exceptions:
We have found no nearby seed of Vicia carolina and thus have none at Somme.

Viola conspersa is recovering well in Somme Woods but is rare in Somme Prairie Grove.  

The recovery of wood pea or pale vetchling (Lathyrus ochroleucus) seems only to be just getting started, where dormant roots were transplanted into Somme Woods. The original seedlings were grown for us by the Chicago Botanic Garden. The similar veiny vetchling (Lathyrus venosus) seemed lost at Somme. Then we noticed browsed bits of leaves and stems, provided deer exclusion cages, and now find it thriving in four spots.

Retreat to sand areas:

Some formerly-common, rich-woodland species seem now to survive mostly sand areas, which degrade more slowly in the absence of fire. For example: 

Canada hawkweed (Hieraceum canadense). Pepoon wrote: “Borders of woods, common.” Still common in sand areas, but not rich savannas or woodlands.

Rough hawkweed (Hieraceum scabrum). Pepoon wrote: “Dry open places, throughout. Our common species.” Today: common only in sand areas. 

One Somme seed source principle is that we don't gather seed for restoration in sand areas. Rich-soil areas likely were genetically different, and it's been our goal to restore and conserve the genetics of such places. But should that principle be modified for species that now survive mostly in sand areas, or in very dry areas?

Rely on the seed bank?
A few species, for example some legumes (some of which have long-lasting, hard seed coats), may emerge from the seed bank in some cases. I have seen missing legumes (Lathyrus ochroleucus and Lespedeza violacea) apparently emerge when fire management begins, but it could be that these plants were surviving but not recorded at first because they consisted only of a few leaves hanging on from year to year thanks to the little sun they did get. On most sites, the seed bank seems to be more of a myth than a reality. Most species, on most sites, do not spontaneously re-emerge. Restoring them by seed from nearby populations is one good experiment that should be encouraged at some sites.

One or many seed sources?
We should find as many and diverse populations of these refuges as we can – and restore the seeds (and some soil, if possible) to areas where full ecosystem restoration experiments are under way. Some experts have recommended restoring seeds from only one site for a given restoration. But in some cases, seed sources may consist of only one or just a few plants. Even where there may be many, we may be looking at a clone, or all may have descended from one or two individuals that survived some bottleneck when the farmer let loose his sheep or pigs or whatever. Perhaps most populations have lost some of the “genes” (alleles) that better fitted them for wetter or drier or sunnier or more-browsed-by-deer or whatever conditions. Thus one experiment, as least in some cases, should be to restore species from many nearby small populations, if possible. Perhaps then populations can re-assemble the “natural richness” of their gene pools – and surprise us with their behavior. 

Note on names: Most names above still follow Swink and Wilhelm. When Swink and Wilhelm (Plants of the Chicago Region) refer a Pepoon account to another name, this post uses the S&W common name for that referred species. The contemporary associates given above are mostly from Swink and Wilhelm (plus, in a few cases, Wilhelm and Rericha).

References.

Pepoon, H.S. Flora of the Chicago Region. 1927.

Keep in mind that when he studied plants (late 1800s and early 1900s), the ecosystem had already been degrading for many decades.

  

Fralish, James S. 2004. The Keystone Role of Oak and Hickory in the Central Hardwood Forest. Gen. Tech. Rep. SRS-73. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. pp. 78-87.

     An important article to read, for context. See abstract, below.

     Abstract—Communities of the central hardwood forest have been dominated primarily by oak and hickory for the past 5000 years. Over this time period, they have become keystone species within the ecosystem and are of major importance in maintaining biodiversity. Not only do the large number of oak and hickory species by themselves contribute to community richness but they are known to provide food and support for a substantial number of wildlife species. Moreover, the structure created by dominance of oak and hickory in the forest community provides an environment for a highly diverse herbaceous understory. Data from oak-hickory stands with a maple-beech understory of saplings and small trees show a 90 percent drop in photosynthetically active radiation (PAR) at ground level accompanied by a 35 percent increase in litter weight compared to stands without an understory. The result is over a 90 percent drop in species richness and cover. This drastic loss of biodiversity, foliage, and fruit has serious implications for insect and bird populations and also suggests a potential for increased soil erosion and loss of nutrients. Extensive research into the loss of biodiversity is advised.