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

Abstract

We 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 of Echinocactus platyacanthus (Cactaceae), Yucca filifera and Agave 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 filifera seeds always had high germination independently of warming treatment and season. Agave striata seeds from OTCs had higher germination than those from control plots. Agave striata exhibited 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 platyacanthus showed 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 platyacanthus formed 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 for A. striata and E. platyacanthus at 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.

Seed traits and germination in the Cactaceae family: A review across Americas

“…Even some works where the cactus seeds were stored under controlled conditions have demonstrated that these can germinate after various years (Flores et al 2005, Sánchez-Salas et al 2006 up to a maximum of 10 years (Alcorn & Martin 1974, Fearn 1977, Trujillo et al 2014. Few studies have directed their efforts toward evaluating the viability of cactus seeds under natural conditions and their permanence in seed banks (Álvarez-Espino et al 2014, Aragón-Gastélum et al 2018.…”

“…There are few studies that have submitted the seeds to environmental conditions and have examined their viability after different burial periods (Bowers 2000, 2005, Matías-Palafox 2007Olvera-Carrillo et al 2009, Cheib & Souza 2012, Goodman et al 2012, Álvarez-Espino et al 2014, Ordoñez-Salanueva et al 2017, Lindow-López et al 2018a, Aragón-Gastélum et al 2018 or have assessed the effective seed bank, extracting the seeds from the soil in different times of the year (Montiel & Montaña 2003). Only the studies of Bowers (2005) and Ordoñez-Salanueva et al (2017) shows two species (Mammillaria grahamii and Polaskia chende) capable of possessing a long-term, continuous seed bank (up to at least five years) according to the classification of Bakker et al (1996).…”

“…In recent years, various studies of cactus have directed their efforts to evaluating the possible impact of global warming on the germination of the seeds (Ordoñez-Salanueva et al 2015, and Aragón-Gastélum et al 2018, through the assessment of the germination response faced with different temperatures. Other studies, although not directly mentioning global warming, show useful results to evaluate the response of cactus seeds faced with temperatures higher than 30 °C (Kin et al 2015, Meiado et al 2016.…”

Review: Plant Eco-Evolutionary Responses to Climate Change: Emerging Directions

“…Additionally, studies should examine the fitness consequences of temporal shifts in germination [15,16]. By exploring the effects of climate change on the processes by which seeds germinate, future studies will generate realistic predictions of recruitment from seed under climate change [29,30], and inform conservation strategies [26].…”

Seed dormancy release of Halenia elliptica in response to stratification temperature, duration and soil moisture content

“…Some studies have determined the response of seed dormancy release to single environmental factors such as temperature [5,7,[16][17][18], winter duration [11,19] and seed/soil moisture content [13][14][15] during cold stratification. The results of these studies suggested that global warming could impact the dynamics of seed dormancy release and thus delay or enhance plant regeneration from seeds [20][21][22][23]. However, climate change is not only a change in temperature, but it also may alter the duration of winter and soil moisture content [20].…”