Rare Species Guide

  Basis for Listing

Sanicula trifoliata is a rare species found in diverse mesic hardwood forests in the southeast portion of the state. In this case, the term "diverse" refers to forests that have retained their original compliment of species, a variety of topographical aspects, and healthy soils, all of which are needed to sustain vital ecosystem functions. If these functions are impaired, the forests are less able to resist the invasion of aggressive, non-native species particularly Rhamnus cathartica (common buckthorn), Alliaria petiolata (garlic mustard), a variety of tree pathogens, and numerous species of earthworm.

At one time, intact mesic hardwood forests were quite extensive, actually covering a large portion of southeast Minnesota. Land-clearing activities subsequently reduced the continuous forest to small, discontinuous fragments, most of which have been further damaged by livestock grazing or non-sustainable logging practices. This course of events has so severely compromised ecosystem functions that there is considerable doubt many of these remnants can sustain themselves as full-functioning biotic communities. For these reasons, S. trifoliata was listed as a special concern species in Minnesota in 1984.

  Description

Sanicula trifoliata is a biennial forb with a single erect stem that can reach a height of about 75 cm (2.5 ft.). The leaves at the base and on lower portions of the stem have long petioles and palmately 3-parted blades. The leaves on the upper part of the stem are reduced in size, and are sessile or have only short petioles, and they are usually trifoliate. The inflorescence is an umbel with 2 or 3 branches (called rays) that are 1.5-2.5 cm (0.59-0.98 in.) long. At the tip of each ray is an umbellet with about 7 flowers; 4 or 5 of the flowers are entirely male and on pedicels 2-5 mm (0.08-0.20 in.) long. The calyx lobes of the male flowers are lanceolate-acuminate in shape, and the petals are white. In each umbellet there are also 2-5 flowers that are bisexual and sessile; their calyx lobes are larger than those of the male flowers. The styles are erect and shorter than the calyx. The fruits are 6-8 mm (0.24-0.31 in.) long and covered with slender, hooked prickles (Shan and Constance 1951). There are 4 species of Sanicula in Minnesota. Sanicula trifoliata is distinguished from the others by having flowers with styles shorter than the calyx, and the calyx extending beyond the uppermost bristles of the fruit.

  Habitat

In Ohio, S. trifoliata is reported to be an indicator of old-growth forests on northeast-facing slopes (Olivera and Hix 1998). A study in Canada found similar results (Pryer and Phillippe 1989). Preliminary analysis of Minnesota data shows a comparable yet somewhat less restrictive pattern of occurrence in mesic hardwood forests. There is a strong correlation with north-facing slopes in closed-canopy forests of Acer saccharum (sugar maple), Tilia americana (basswood), and Quercus rubra (northern red oak). In some cases the forests have a history of selective of logging, although soils and floristic diversity are largely intact. Presence of non-native species and signs of livestock grazing are minimal.

  Biology / Life History

Sanicula trifoliata is a facultative biennial; it produces seeds once then dies (Hawkins et al. 2007). This is somewhat unusual for a species that occurs in mature hardwood forests where most forbs are perennial. The advantage of this life history trait is not readily apparent.

The structure of the flowers indicates that S. trifoliata is pollinated by flying insects. The fruits, possessing small, hooked bristles, are apparently adapted for attaching to the fur of mammals, probably deer or similar sized animals. Dispersal begins in August when the fruits have matured and lasts a year or longer (i.e., the length of time the fruits are retained on the dead, upright stems) (Hawkins et al. 2007). In an experimental study, some seeds did not germinate until the 6th year, which implies a potential to form a persistent seed bank in the soil (Hawkins et al. 2007).

The best time to search for S. trifoliata is when the fruits are mature in August and September.

  Conservation / Management

Management of S. trifoliata comes down to management of mesic hardwood forests in the southeastern corner of the state. The broad goal is to maintain basic ecological processes that support a high diversity of plants; a goal that is pursued by eliminating incompatible land use activities. Domestic livestock grazing is perhaps the most destructive practice and should be curtailed, as should timber harvesting practices that open large gaps in the canopy or disturb the soil. Also, the remnant forests should not be used for motorized vehicle recreation - the soils are simply too fragile. Invasive species are, and will remain, a serious concern. Potential sources of invasive species and avenues of invasion should be identified and monitored closely, and swift remedial action should be undertaken as soon as a problem is identified.

  Conservation Efforts in Minnesota

A significant percentage of forested habitats in the southeast are under the management control of the Minnesota DNR. These sites are managed primarily for timber production, recreation, and conservation. A few are known to harbor populations of S. trifoliata, although the condition of the habitats and trends of the populations are not being monitored.

  References and Additional Information

Hawkins, T. S., J. M. Baskin, and C. C. Baskin. 2007. Seed morphology, germination phenology, and capacity to form a seed bank in six herbaceous layer Apiaceae species of the eastern deciduous forest. Castanea 72(1):8-14.

Olivera, A. M., and D. M. Hix. 1998. Influence of aspect and stand age on ground flora of southeastern Ohio forest ecosystems. Plant Ecology 139:177-187.

Pryer, K. M., and L. R. Phillippe. 1989. A synopsis of the genus Sanicula (Apiaceae) in eastern Canada. Canadian Journal of Botany 67:694-707.

Shan, R. H., and L. Constance. 1951. The genus Sanicula (Umbelliferae) in the old world and the new. University of California Publications in Botany 25:1-78.