PARENT SESSION
Poster Session #32: Plant Ecology I.
Wednesday, August 8, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
137
Temporal variation of the soil seed bank in an arid thorn scrub community of north-central Chile.
Gutiérrez, Julio1, Meserve, Peter2, 1 2
ABSTRACT- Soil seed bank was monitored in four 75x75 m plots over six years (1990-1995) at a semiarid site in north-central Chile. Sixty-six species were identified in the seed bank, but seeds of woody shrubs were poorly represented. Total seed densities ranged from 2,000 to 42,000/sq.m. Average mass of shrub seeds was significantly greater than that of seeds of other growth-forms. Depending on the year, between 70 and 90% of the seeds in the soil were less than 1 mg with those in the 0.51-1.00 mg size-class being most numerous. Seed densities were highly variable between years as well as within years, but were also closely associated with plant cover patterns and rainfall regime. Higher seed densities were found in wet years, and in samples taken in early summer and early autumn (i.e., after seed dispersal); the lowest seed densities were found in late winter (i.e., after ephemeral plant emergence). The ephemeral plant species with the highest cover were also the most abundant in the soil seed bank and exhibited the largest seed density fluctuations. In general, species' seed densities were 5-10 fold higher during the 1991-1992 El Niño/Southern Oscillation (ENSO) years. The large increase of the soil seed bank after an ENSO event shows the importance of this phenomenon for the replenishment of seeds in the semiarid region of Chile.
KEY WORDS: seed bank, arid systems, enso, chile