December 2012 Number 1 - Utah Native Plant Society

Utah Native Plant Society
All of the species discussed so far are common plants
that were included in seed bank studies in order to understand
their establishment ecology, rather than to provide
seed bank data to inform PVA. There are very few
long-term seed retrieval studies for rare plants. The
Snake River Plains endemic Lepidium papilliferum is
one of the few rare species whose seed bank dynamics
have been included in PVA (Meyer et al. 2005, 2006).
This spring ephemeral species has cue non-responsive
seeds that show the characteristic linear decrease as a
function of time in the proportion of initially viable
seeds remaining in the seed bank (Figure 7; Meyer et al.
2005). There was little or no germination during the first
two years of this eleven-year retrieval study, so that at
least three years of retrieval data would have been
needed to estimate the slope of seed bank depletion. The
maximum longevity in soil for two seed collections in-
cluded in the study was estimated to be 12 years. Seeds
of this species can be induced to germinate by piercing
imbibed seeds and subjecting them to 2-4 weeks of
moist chilling. Development of this technique has facilitated
greenhouse production of seeds for reintroduction
experiments, but seems to shed little light on how the
seeds gradually become nondormant in the field.
Rare plants can be expected to have seeds that run
the gamut of germination response patterns and associated
seed bank depletion trajectories. As discussed
above, it is frequently important to investigate this aspect
of rare plant population biology, especially when
the goal is to understand the likely future status for a
population or species. The information obtained from
seed bank studies can also be critical for planning management
and mitigation activities.
% OF INITIALLY VIABLE SEEDS
100
80
60
40
20
0
100
80
60
40
20
0
1991 SEEDS
8/92 8/93 8/94 8/95 8/96 8/97 8/98 8/99 8/2000 8/2001 8/2002 8/2003
1992 SEEDS
DORMANT
DORMANT PLUS GERMINABLE
DORMANT PLUS GERMINABLE PLUS GERMINATED
TOTAL I NITIALLY VIABLE
8/92 8/93 8/94 8/95 8/96 8/97 8/98 8/99 8/2000 8/2001 8/2002 8/2003
DATE
Figure 7. Patterns of change through time in dormant seed percentage, dormant plus germinable seed percentage, and
viable plus germinated seed percentage over an eleven-year period in a seed retrieval experiment with two collections
of Lepidium papilliferum. The difference between viable plus germinated seed percentage and initially viable seed
percentage represents seeds that lost viability prior to germinating. Adapted from Meyer and others (2005).
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