Timing and spatial patterning of seed dispersal and redistribution in a South American warm desert

MARONE, LUIS; ROSSI, BERTILDE; HORNO, MANUEL

PLANT ECOLOGY

SPRINGER

Lugar: Berlin; Año: 1998 vol. 137 p. 143 - 150

1385-0237

We measured newly-produced seeds entering the soil (Potential Seed Bank) to assess the timing and spatial patterningof Phase I dispersal in the central Monte desert, Argentina. Rates of forb- (6.13 mg m−2 d−1) and shrub-seedinput (48.9 mg m−2 d−1) were maximum in early summer. The rate of grass-seed input, instead, was similar inearly and late summer (7 to 8 mg m−2 d−1). About 90% of forb- and shrub-seed mass entered the habitat throughprotected (i.e., under canopy) areas, whereas 70% of grass-seed mass did so through exposed areas. Adult plantlocation and the uneven impact of wind on shrub, forb and grass seeds may explain such patterns.We also compared the Potential Seed Bank with the soil seed bank in the following spring (Realized SeedBank). Seeds that form transient banks in other ecosystems (e.g., shrub seeds of the genus Larrea, or perennialgrass seeds like those of Pappophorum and Trichloris) prevailed in the Potential Seed Bank. Some annual forbseeds, instead, appeared to form a more persistent seed bank, and prevailed in the Realized Seed Bank (e.g.,Chenopodium). Horizontal redistribution did not affect the spatial patterning of forb and shrub seeds, but produceda more homogeneous distribution of grass seeds in the habitat. The impact of wind could explain the redistributionpattern of grass seeds. Finally, we found almost 80% of total seeds in the top 2 cm of soil. The smallest grass andforb seeds (Sporobolus and Descurainia) as well as some medium-sized and large forb seeds (e.g., Glandularia,Sphaeralcea, Phacelia) were able to reach deeper soil layers in the central Monte desert.