Potential impact of global warming on seed bank, dormancy and germination of three succulent species from the Chihuahuan Desert

Abstract

AbstractWe assessed inter-seasonal dynamics of seed banks, dormancy and seed germination in three endemic Chihuahuan Desert succulent species, under simulated soil warming conditions. Hexagonal open top-chambers (OTCs) were used to increase soil temperature. Seeds ofEchinocactus platyacanthus(Cactaceae),Yucca filiferaandAgave striata(Asparagaceae) were collected and buried within and outside OTCs. During the course of one year, at the end of each season, seed batches were exhumed to test viability and germination. Soil temperature in OTCs was higher than in control plots.Yucca filiferaseeds always had high germination independently of warming treatment and season.Agave striataseeds from OTCs had higher germination than those from control plots.Agave striataexhibited low germination in fresh seeds, but high germination in spring. Seeds from this species lost viability throughout the experimental timeframe, and had no viable seeds remaining in the soil.Echinocactus platyacanthusshowed high germination in fresh seeds and displayed dormancy cycling, leading to high germination in spring, low germination in summer and autumn, and high germination in winter. Germination of this species was also higher in seeds from OTCs than those from control plots.Echinocactus platyacanthusformed soil seed banks and its cycle of inter-seasonal dormancy/germination could be an efficient physiological mechanism in a climate change scenario. Under global warming projections, our results suggest that future temperatures may still fall within the three studied species’ thermal germination range. However, higher germination forA. striataandE. platyacanthusat warmer temperatures may reduce the number of seeds retained in the seed bank, and this could be interpreted as limiting their ability to spread risk over time. This is the first experimental study projecting an increase in soil temperature to assess population traits of succulent plants under a climate change scenario for American deserts.