Comparison of methods to estimate soil seed banks: the role of seed size and mass

Abstract

There are two main methods for estimating seed density and species composition of soil seed banks: manual seed extraction and seedling emergence. These methods were used to determine and compare seed density and species composition in the soil of a natural grassland in Patagonia. Additionally, known amounts of seeds of different sizes from Patagonian grassland species were mixed with soil to evaluate the efficiency of the seed extraction method, and determine their recovery percentage. Seed density found in the grassland soil with the extraction method was four times higher than that found with the seedling emergence method. Through the use of these two methods, there was very little overlap found in species composition. Small seeds (< 1 mm) were only found with the seedling emergence method, whereas the seeds of species with specific germination requirements were found with the seed extraction method. Seed recovery of grassland species varied from 2.5% for smaller seeds (Erophila verna) to 100% for larger seeds (Rumex acetosella) with the seed extraction method. This method was more effective in detecting seeds of large-seeded species. Discrepancies in seed detection between both methods may be related to seed dormancy, specific germination requirements, seed size and mass. These two methods are necessary to describe seed density and seed bank composition.Nomenclature: Correa (1969Correa ( -1999.

The Andean Forest Soil Seed Bank in Two Successional Stages in Northeastern Colombia

“…The fact that the diversity and density of the species found by using the direct separation method was higher compared to the germination method can be explained by three non-exclusive factors: 1) physiological, such as seed dormancy, longevity, and germination traits (Saatkamp et al 2009, Gonzalez & Ghermandi, 2012; 2) ecological, such as storage time, germination requirements and high rates of dispersal/predation (Thompson et al 2003, Daws et al 2005, Walck et al 2005, Bernhardt et al 2008, Esquivel et al 2008, Price et al 2010, Gonzalez & Ghermandi 2012; and 3) morphological, such as seed size and seed coat (De Villiers et al 1994, Facelli et al 2005, Venable 2007, Price et al 2010, Gonzalez & Ghermandi 2012. Similar results were found in a study with seed banks from natural grasslands in Patagonia by Gonzalez and Ghermandi (2012). These authors report a seed density which is four times higher with the direct separation method than with the germination method.…”

“…Two methodologies have been developed to assess the presence of soil seed banks: germination and direct separation (Ishikawa-Goto & Tsuyuzaki 2004, Price et al 2010, Gonzalez & Ghermandi 2012. In the former, germinated seedlings are identified and quantified (Roberts 1981, Ter Heerdt et al 1996, while in the latter the seeds are separated by both seed size and density.…”

“…Depending on the method employed, differences in both density and species composition may be found, even in the same location (Tsuyuzaki 1994, Ishikawa-Goto & Tsuyuzaki 2004, Bernhardt et al 2008, Price et al 2010. Most studies that have used these two methods to compare the soil seed bank have found different results and concluded that the two methods are complementary (Price et al 2010, Gonzalez & Ghermandi 2012. Despite these differences, most studies only employ the germination method (Jaimes-Sánchez & Rivera-Ospina 1991, Cárdenas et al 2002, Acosta 2004, Montenegro & Vargas 2005, Moscoso & Diez 2005.…”

Evaluation of desiccated and deformed diaspores from natural building materials

“…from the inorganic components of adobe. Common salt (sodium chloride, NaCl) solution with 1.1261 g cm -3 specific gravity was used as flotation medium (Gonzalez and Ghermandi 2012;Henn et al in press). The supernatant was processed using a 0.25 mm sieve after sedimentation, which was then rinsed under tap water and air-dried.…”

Soil seed bank assay methods influence interpretation of non‐native plant management

“…The extraction method directly identifies seeds in soil regardless of germinability (Ball & Miller, ) and often detects more seeds and species compared to emergence (Brown, ; Price et al., ). However, extraction counts all seeds regardless of their potential viability, habitat selection or preferred niche or specific germination requirements (Baskin & Baskin, ; Gonzales & Ghermandi, ), often generating false positives for apparently healthy, but non‐viable seeds, and overestimating viability in seed banks (Baskin & Baskin, ). Viability tests can be conducted after extraction to somewhat mitigate these false positives.…”