Demographic analysis of dormancy and survival in the terrestrial orchid Cypripedium reginae
Article first published online: 23 JUL 2004
Journal of Ecology
Volume 92, Issue 4, pages 686–695, August 2004
How to Cite
KÉRY, M. and GREGG, K. B. (2004), Demographic analysis of dormancy and survival in the terrestrial orchid Cypripedium reginae. Journal of Ecology, 92: 686–695. doi: 10.1111/j.0022-0477.2004.00885.x
- Issue published online: 23 JUL 2004
- Article first published online: 23 JUL 2004
- Received 23 September 2003 revision accepted 10 February 2004 Handling Editor: Michael Hutchings
- Cypripedium reginae;
- demographic analysis;
- population dynamics;
- 1We use capture-recapture models to estimate the fraction of dormant ramets, survival and state transition rates, and to identify factors affecting these rates, for the terrestrial orchid Cypripedium reginae. We studied two populations in West Virginia, USA, for 11 years and investigated relationships between grazing and demography. Abe Run's population was small, with moderate herbivory by deer and relatively constant population size. The population at Big Draft was of medium size, with heavy deer grazing, and a sharply declining number of flowering plants up to the spring before our study started, when the population was fenced.
- 2We observed dormant episodes lasting from 1 to 4 years. At Abe Run and Big Draft, 32.5% and 7.4% of ramets, respectively, were dormant at least once during the study period for an average of 1.6 and 1.3 years, respectively. We estimated the annual fraction of ramets in the dormant state at 12.3% (95% CI 9.5–15.8%) at Abe Run and at 1.8% (95% CI 1.2–2.6%) at Big Draft. Transition rates between the dormant, vegetative and flowering life-states did not vary between years in either population. Most surviving ramets remained in the same state from one year to the next. Survival rates were constant at Abe Run (0.96, 95% CI 0.93–0.97), but varied between years at Big Draft (0.89–0.99, mean 0.95).
- 3At Big Draft, we found neither a temporal trend in survival after cessation of grazing, nor relationships between survival and the number of spring frost days or cumulative precipitation during the current or the previous 12 months. However, analysis of precipitation on a 3-month basis revealed a positive relationship between survival and precipitation during the spring (March–May) of the previous year.
- 4Relationship between climate and the population dynamics of orchids may have to be studied with a fine temporal resolution, and considering possible time lags. Capture-recapture modelling provides a comprehensive and flexible framework for demographic analysis of plants with dormancy.