Soil seed bank composition over desert microhabitats: patterns and plausible mechanisms

L. MARONE; V. R. CUETO; F. A. MILESI; J. LOPEZ DE CASENAVE

CANADIAN JOURNAL OF BOTANY

National Research Council Canada

Año: 2004 vol. 82 p. 1809 - 1816

0008-4026

We assessed soil seed bank composition and size over several microhabitats of two habitats of the central Monte Desert of Argentina (open Prosopis woodland and Larrea shrubland) to analyse differences among them. Seed densities were similar to those already reported for other deserts, but we found consistent differences in seed composition among microhabitats. Whereas grass seeds (e.g., Aristida, Pappophorum, Neobouteloua, Trichloris, Digitaria) prevailed in natural depressions of open areas, forb seeds (e.g., Phacelia, Lappula, Descurainia, Plantago, Chenopodium) were more abundant under trees. The comparison of seed production during primary dispersal (i.e., seed rain) with seed density on the ground at the end of dispersal indicated that most forb seeds entered the habitat through the microhabitats located beneath the canopy of trees and tall shrubs, and remained there after redistribution. Most grass seeds, by contrast, entered it through bare-soil and under-grass microhabitats, and reached more even distributions after secondary dispersal, especially because of dramatic losses in bare soil. Patterns of plant recruitment and seed dynamics in specific microhabitats were better understood when differences of soil seed bank composition, but not of total seed density, were taken into account.Prosopis woodland and Larrea shrubland) to analyse differences among them. Seed densities were similar to those already reported for other deserts, but we found consistent differences in seed composition among microhabitats. Whereas grass seeds (e.g., Aristida, Pappophorum, Neobouteloua, Trichloris, Digitaria) prevailed in natural depressions of open areas, forb seeds (e.g., Phacelia, Lappula, Descurainia, Plantago, Chenopodium) were more abundant under trees. The comparison of seed production during primary dispersal (i.e., seed rain) with seed density on the ground at the end of dispersal indicated that most forb seeds entered the habitat through the microhabitats located beneath the canopy of trees and tall shrubs, and remained there after redistribution. Most grass seeds, by contrast, entered it through bare-soil and under-grass microhabitats, and reached more even distributions after secondary dispersal, especially because of dramatic losses in bare soil. Patterns of plant recruitment and seed dynamics in specific microhabitats were better understood when differences of soil seed bank composition, but not of total seed density, were taken into account.Aristida, Pappophorum, Neobouteloua, Trichloris, Digitaria) prevailed in natural depressions of open areas, forb seeds (e.g., Phacelia, Lappula, Descurainia, Plantago, Chenopodium) were more abundant under trees. The comparison of seed production during primary dispersal (i.e., seed rain) with seed density on the ground at the end of dispersal indicated that most forb seeds entered the habitat through the microhabitats located beneath the canopy of trees and tall shrubs, and remained there after redistribution. Most grass seeds, by contrast, entered it through bare-soil and under-grass microhabitats, and reached more even distributions after secondary dispersal, especially because of dramatic losses in bare soil. Patterns of plant recruitment and seed dynamics in specific microhabitats were better understood when differences of soil seed bank composition, but not of total seed density, were taken into account.Phacelia, Lappula, Descurainia, Plantago, Chenopodium) were more abundant under trees. The comparison of seed production during primary dispersal (i.e., seed rain) with seed density on the ground at the end of dispersal indicated that most forb seeds entered the habitat through the microhabitats located beneath the canopy of trees and tall shrubs, and remained there after redistribution. Most grass seeds, by contrast, entered it through bare-soil and under-grass microhabitats, and reached more even distributions after secondary dispersal, especially because of dramatic losses in bare soil. Patterns of plant recruitment and seed dynamics in specific microhabitats were better understood when differences of soil seed bank composition, but not of total seed density, were taken into account.