Burial increases seed longevity of two Artemisia tridentata (Asteraceae) subspecies.
OBJECTIVE
Seed longevity and persistence in soil seed banks may be especially important for population persistence in ecosystems where opportunities for seedling establishment and disturbance are unpredictable. The fire regime, an important driver of population dynamics in sagebrush steppe ecosystems, has been altered by exotic annual grass invasion. Soil seed banks may play an active role in postfire recovery of the foundation shrub Artemisia tridentata, yet conditions under which seeds persist are largely unknown.


METHODS
We investigated seed longevity of two Artemisia tridentata subspecies in situ by retrieving seed bags that were placed at varying depths over a 2 yr period. We also sampled naturally dispersed seeds in litter and soil immediately after seed dispersal and before flowering in subsequent seasons to estimate seed persistence.


RESULTS
After 24 mo, seeds buried at least 3 cm below the soil surface retained 30-40% viability whereas viability of seeds on the surface and under litter declined to 0 and < 11%, respectively. The density of naturally dispersed seeds in the seed bank was highly heterogeneous both spatially and temporally, and attrition varied significantly by region.


CONCLUSIONS
Our study suggests that Artemisia tridentata has the potential to form a short-term soil seed bank that persists longer than has been commonly assumed, and that burial is necessary for seed longevity. Use of seeding techniques that promote burial of some seeds to aid in formation of a soil seed bank may increase restoration potential.
U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 S.W. Jefferson Way, Corvallis, Oregon 97331 USA. ucwijayratne@fs.fed.us
Upekala C
UC
Wijayratne
David A
DA
Pyke
D019306:Artemisia / Q000145:classification* / Q000502:physiology*; D008136:Longevity; D012639:Seeds / Q000145:classification* / Q000502:physiology*; D012987:Soil; D013045:Species Specificity
D012987:Soil