Seasonal timing of first rain storms affects rare plant population dynamics

Ecology
By: , and 

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Abstract

A major challenge in forecasting the ecological consequences of climate change is understanding the relative importance of changes to mean conditions vs. changes to discrete climatic events, such as storms, frosts, or droughts. Here we show that the first major storm of the growing season strongly influences the population dynamics of three rare and endangered annual plant species in a coastal California (USA) ecosystem. In a field experiment we used moisture barriers and water addition to manipulate the timing and temperature associated with first major rains of the season. The three focal species showed two- to fivefold variation in per capita population growth rates between the different storm treatments, comparable to variation found in a prior experiment imposing eightfold differences in season-long precipitation. Variation in germination was a major demographic driver of how two of three species responded to the first rains. For one of these species, the timing of the storm was the most critical determinant of its germination, while the other showed enhanced germination with colder storm temperatures. The role of temperature was further supported by laboratory trials showing enhanced germination in cooler treatments. Our work suggests that, because of species-specific cues for demographic transitions such as germination, changes to discrete climate events may be as, if not more, important than changes to season-long variables.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Seasonal timing of first rain storms affects rare plant population dynamics
Series title Ecology
DOI 10.1890/11-0471.1
Volume 92
Issue 12
Year Published 2011
Language English
Description 12 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Ecology
First page 2236
Last page 2247