Seed dormancy responses to temperature relate to Nothofagus species distribution and determine temporal patterns of germination across altitudes in Patagonia

Abstract

Seeds integrate environmental cues that modulate their dormancy and germination.Although many mechanisms have been identified in laboratory experiments, their contribu-tion to germination dynamics in existing communities and their involvement in definingspecies habitats remain elusive.By coupling mathematical models with ecological data we investigated the contribution ofseed temperature responses to the dynamics of germination of three Nothofagus species thatare sharply distributed across different altitudes in the Patagonian Andes.Seed responsiveness to temperature of the three Nothofagus species was linked to the ther-mal characteristics of their preferred ecological niche. In their natural distribution range, therewas overlap in the timing of germination of the species, which was restricted to mid-spring.By contrast, outside their species distribution range, germination was temporally uncoupledwith altitude. This phenomenon was described mathematically by the interplay between inter-specific differences in seed population thermal parameters and the range in soil thermic envi-ronments across different altitudes.The observed interspecific variations in seed responsiveness to temperature and its environ-mental regulation, constitute a major determinant of the dynamics of Nothofagus germinationacross elevations. This phenomenon likely contributes to the maintenance of patterns ofspecies abundance across altitude by placing germinated seeds in a favorable environment forplant growth