title: Ability of matrix models to explain the past and predict the future of plant populations.
abstract: Uncertainty associated with ecological forecasts has long been recognized, but forecast accuracy is rarely quantified. We evaluated how well data on 82 populations of 20 species of plants spanning 3 continents explained and predicted plant population dynamics. We parameterized stage-based matrix models with demographic data from individually marked plants and determined how well these models forecast population sizes observed at least 5 years into the future. Simple demographic models forecasted population dynamics poorly; only 40% of observed population sizes fell within our forecasts' 95% confidence limits. However, these models explained population dynamics during the years in which data were collected; observed changes in population size during the data-collection period were strongly positively correlated with population growth rate. Thus, these models are at least a sound way to quantify population status. Poor forecasts were not associated with the number of individual plants or years of data. We tested whether vital rates were density dependent and found both positive and negative density dependence. However, density dependence was not associated with forecast error. Forecast error was significantly associated with environmental differences between the data collection and forecast periods. To forecast population fates, more detailed models, such as those that project how environments are likely to change and how these changes will affect population dynamics, may be needed. Such detailed models are not always feasible. Thus, it may be wiser to make risk-averse decisions than to expect precise forecasts from models.
authors.affiliation: Harvard Forest, Harvard University, 324 N Main Street, Petersham, MA, 01366, U.S.A.. ecrone@fas.harvard.edu.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Crone
authors.forename: Martha M
authors.initials: MM
authors.lastname: Ellis
authors.forename: William F
authors.initials: WF
authors.lastname: Morris
authors.forename: Amanda
authors.initials: A
authors.lastname: Stanley
authors.forename: Timothy
authors.initials: T
authors.lastname: Bell
authors.forename: Paulette
authors.initials: P
authors.lastname: Bierzychudek
authors.forename: Johan
authors.initials: J
authors.lastname: Ehrlén
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Kaye
authors.forename: Tiffany M
authors.initials: TM
authors.lastname: Knight
authors.forename: Peter
authors.initials: P
authors.lastname: Lesica
authors.forename: Gerard
authors.initials: G
authors.lastname: Oostermeijer
authors.forename: Pedro F
authors.initials: PF
authors.lastname: Quintana-Ascencio
authors.forename: Tamara
authors.initials: T
authors.lastname: Ticktin
authors.forename: Teresa
authors.initials: T
authors.lastname: Valverde
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Williams
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Doak
authors.forename: Rengaian
authors.initials: R
authors.lastname: Ganesan
authors.forename: Kathyrn
authors.initials: K
authors.lastname: McEachern
authors.forename: Andrea S
authors.initials: AS
authors.lastname: Thorpe
authors.forename: Eric S
authors.initials: ES
authors.lastname: Menges
mesh_terms: D003247:Conservation of Natural Resources; D005544:Forecasting; D008962:Models, Theoretical; D018521:Plant Physiological Phenomena; D011156:Population Density; D011157:Population Dynamics / Q000639:trends
keywords: análisis de viabilidad poblacional; density dependence; dependencia de la densidad; dinámica poblacional de plantas; ecological forecasting; environmental change; matrix projection models; modelos de proyección matricial; plant population dynamics; population viability analysis; precipitación; precipitation; pronóstico ecológico; temperatura; temperature