Persistent soil seed banks in Phacelia secunda (Hydrophyllaceae): experimental detection of variation along an altitudinal gradient in the Andes of central Chile (33 S)

Abstract

Summary1 It is unclear whether soil seed banks in alpine environments are a result of selection for extended seed dormancy, of ideal conditions for seed preservation in the soil, or a combination of both. 2 The nature of the soil seed bank was investigated in the perennial herb Phacelia secunda (Hydrophyllaceae) through reciprocal burial experiments using seeds obtained from populations growing at 1600, 2200, 2900 and 3400 m a.s.l. in the mediterranean Andes of central Chile. At the four elevations, six replicates of 50 seeds each, from each of the four elevational sources, were buried at 5 cm depth in mesh envelopes, placed in wire cages to protect against predation. Seeds were retrieved 1, 2 and 3 years after burial, and numbers of ungerminated seeds, and of those that remained viable, were determined. 3 At all elevations of seed burial, increasing proportions of seeds remained ungerminated, and proportionately more of the ungerminated seeds remained viable, as elevation of source of seed increased. For seed from low elevation, more seeds remained viable in the soil at the higher burial sites. However, for the seeds from higher elevation sources, seeds remaining viable were similar in number at all sites for seed burial. Half-lives of seed buried at the source elevation, calculated from the log-logistic distribution, increased with elevation, and ranged from 188 days at 1600 m to 354 days at 3400 m. 4 The results suggest that the propensity to form a persistent seed bank in P. secunda increases with elevation. Seeds from the highest elevations had the longest persistence, and this was largely unaffected by soil preservation conditions. Seeds from lower elevations survived for less time, and this was modifiable by preservation conditions. These results suggest that both selective effects and soil conditions may be involved in soil seed bank expression in the alpine environment.

Seed bank persistence of clonal weeds in contrasting habitats: implications for control

“…This is consistent with other alpine plant species, which delayed seed germination until reaching at least the next growing season (e.g., Meyer et al 1995;Cavieres and Arroyo 2001;Shimono and Kudo 2005). This innate dormancy prevents precocious germination beneath the snow pack, finetuning the timing of seed germination to favour seedling establishment.…”

“…Seeds provide an essential link in the population dynamics of these species allowing the establishment of individuals and founding of new populations via dispersal both in space and time (Rees 1996). The timing of seed germination is also a critical determinant of reproductive success (Donohue et al 2005a) and is often controlled by seed dormancy (i.e., seeds that do not germinate in spite of being placed into conditions generally suitable for germination), which can be lost or acquired in response to environmental stimuli such as temperature (Allen and Meyer 1998;Cavieres and Arroyo 2001;Adondakis and Venable 2004), soil moisture (Murdoch and Ellis 1992; Galatowitsch and van der Valk 1996;Bekker et al 1998c) and nutrient concentration (Bekker et al 1998b). Seed dormancy is thought to have evolved in response to unpredictable environmental variability and might lead to the existence of soil seed banks-populations of viable seeds in the soil (e.g.…”

Lolium Multiflorum seeds in the soil: II. Longevity under natural conditions

“…There are some evidences that soil and climate may influence seed longevity (Bekker et al, 1998b;Blaney and Kotanen, 2001;Cavieres and Arroyo, 2001). Fenner and Thompson (2005) concluded that seed persistence is chiefly a species trait but it can be modified by environmental conditions.…”

Divergent Norms of Reaction to Temperature in Germination Characteristics among Populations of the Arctic-Alpine Annual,Koenigia islandica

“…Finally, the possibility exists that large soil seed banks persist over many years, from which only a small fraction germinates each season. Reynolds (1984b) found only a small residual bank of viable seeds in a K. islandica population from Montana, but populations in more severe climates might have larger and more persistent seed banks (Cavieres and Arroyo, 2001). Further investigation is needed to shed light on this aspect.…”