WHAT IS A GERMINATION NICHE AND HOW DOES IT RELATE TO CLIMATE CHANGE?
Walck, J. and Hidayati, S.
Department of Biology, Middle Tennessee State University, Murfreesboro, Tennessee, USA
Contact: Jeffrey L. Walck, Jeffrey.email@example.com
Knowing the range of conditions over which germination occurs for a species is vital to understanding species’ responses to climate change as well as re-establishing plant populations from ex situ seed banks. From testing seeds over a range of environmental conditions, the width of this range can be determined and various terms have been coined to describe it. Germination niche, germination niche-breadth, germination tolerance range, germination niche width, and germination envelope are some examples. The range has been described using species diversity indexes or modified versions of them (Shannon equitability index, Pielou’s evenness index, Levins’ B, inverse Simpson index) or by defining the absolute range between the maximum and minimum conditions of germination. While some research has focused on quantifying the width of this range, other studies have determined the cardinal (or threshold) conditions, particularly the base temperature associated with this range. Data for these studies have been based on field emergence or more commonly on laboratory conditions. Studies on these ranges for germination have been done to examine the correlation between germination width and geographic or ecological range size, with equivocal results, or to predict species’ responses to climate change. However, gaps on our knowledge concerning germination niches are plentiful. First, investigations into germination niches usually focus on the germination stage and temperature responses, which make up only one part of the regeneration and establishment of a species. Second, population variation in germination niches over spatio-temporal scales is rarely considered – determination usually being limited to a single population. Third, how these measurements of germination niches can be extrapolated to natural settings remains problematic, especially when normally the range tested does not include extremes that may occur during climate change. And fourth, additional life cycle stages need to be incorporated to better understand the relationships among niche widths of stages over a broad range of species at a community level.