U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 S.W. Jefferson Way, Corvallis, Oregon 97331 USA.
Am J Bot. 2012 Mar;99(3):438-47. doi: 10.3732/ajb.1000477. Epub 2012 Feb 1.
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.
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.
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.
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.
种子在土壤种子库中的寿命和持久性对于在幼苗建立和干扰机会不可预测的生态系统中种群的持续存在可能尤为重要。火是草原生态系统种群动态的重要驱动因素，而异种一年生草本植物的入侵改变了火的发生规律。土壤种子库可能在基础灌木三齿蒿（Artemisia tridentata）的火灾后恢复中发挥积极作用，但种子持久存在的条件在很大程度上尚不清楚。
我们通过检索在 2 年内放置在不同深度的种子袋，调查了两种三齿蒿亚属的种子寿命。我们还在种子散布后和随后的季节开花前立即在凋落物和土壤中采样自然散布的种子，以估计种子的持久性。
在 24 个月后，埋藏在至少 3 厘米深的土壤下的种子保持 30-40%的活力，而表面和凋落物下的种子活力分别下降到 0 和 <11%。种子库中自然散布的种子的密度在空间和时间上都高度不均匀，损耗因地区而异。
我们的研究表明，三齿蒿有可能形成一个短期的土壤种子库，其持久性比通常假设的要长，并且埋藏是种子长寿的必要条件。使用促进部分种子埋藏的播种技术来帮助形成土壤种子库可能会增加恢复潜力。
