The northern pitcher plant Sarracenia purpurea is a model system for forecasting extinction risk in the face of environmental change. We have monitored demographic variables of two mapped cohorts of S. purpurea in ombrotrophic bogs of northern New England from 1997-2005 (Hawley Bog, Massachusetts) and 1997-present (Molly Bog, Vermont). Growth, survivorship, and reproduction are in close balance, and matrix-models with four life stages (seeds, seedlings/juvenile plants, non-flowering adult plants, flowering adults) predicted population growth rates close to zero, with long doubling times. To further assess seed-to-seedling transitions, we measured and weighed Sarracenia seeds, and conducted a greenhouse experiment on density-dependent dynamics of newly germinated seedlings of S. purpurea.
In fall 1997, we located and tagged 400 S. purpurea plants at Hawley Bog and 444 plants at Molly Bog (400 in one area, 44 in another area of the bog); one-half of each marked cohort were "adult" plants (rosette diameters greater than 100 mm), the other half were "juvenile" plants (rosette diameters less than 100 mm). Each year since then (through 2005 at Hawley Bog, when the population was trampled by moose), plants are relocated and measured (as described in A. M. Ellison and N. J. Gotelli, 2001, Proc. Nat. Acad. Sci. 99: 4409-4412), and flowering status, and whether or not the plant has been damaged by herbivores noted. Plants were mapped with transit and stadia rods in 1999.
Mature seeds of S. purpurea and other recognized species of Sarracenia were collected in the field. Maximum length and width of 100-200 seeds of each species were measured with an ocular micrometer at 100x magnification under a dissecting microscope. A random subset of 20 seeds of each species were individually weighed to the nearest 10 ug.
In September 1998, 1000 S. purpurea seeds were randomly scattered in a planting bed (3 x 1 x 0.25 m) filled with milled Sphagnum. Germinated seedlings were individually flagged with toothpicks, and their location was mapped (+- 1 mm). The number of seedling leaves, plant diameter, length of longest leaf, and rosette diameter of each plant were measured in May 1999, June 1999, August 1999, May 2000, June 2000, August 2000, September 2001, and August 2002. Surviving plants in August 2002 were harvested, dried, and weighed after separating roots and shoots. The flowers from the three flowering plants were also dried and weighed.
Ellison A, Gotelli N. 2019. Demography of Sarracenia Purpurea in Massachusetts and Vermont since 1997. Harvard Forest Data Archive: HF202.