Estimates of soil seed banks are important to many ecological investigations and plant conservation, yet seed banks are among the most difficult plant community attributes to accurately quantify. To compare extraction and emergence seed bank characterization methods, we collected 0- to 5-cm soil seed bank samples and measured plant community composition in six microsite types (below different perennial plant species and interspaces) at 10 field sites in the Mojave Desert, USA. Extraction detected five times more species sample−1 and orders of magnitude greater seed density than emergence, though evaluating viability of extracted seed was not straightforward. Only 13 % of 847 tested seeds from extraction emerged in follow-up assays. Considering all sites, species detection was more similar between methods: 21 taxa for emergence and 28 for extraction. Results suggest that: (i) capturing microsite variation is critical for efficiently estimating site-level desert seed banks; (ii) method comparisons hinged on the scale of analysis for species richness, as differences in species detection between methods diminished when increasing resolution from the sample to the regional scale; (iii) combining data from all seed bank methods provided the strongest correlation with vegetation; and (iv) improving knowledge of seed germinability is important for advancing both seed bank methods, including for extraction to evaluate the proportion of extracted seeds that are viable. Multifactor approaches that balance several effectiveness measures (e.g., both seed density and species detection at multiple scales) and procedural challenges are most likely to accurately represent complexity in tradeoffs for choosing methods to quantify soil seed banks.
The online version of this article (doi: 10.1007/s11258-013-0200-3) contains supplementary material, which is available to authorized users.
This study was funded through a cooperative agreement between the National Park Service (Lake Mead National Recreation Area, in particular Alice Newton and Kent Turner) and the University of Nevada Las Vegas (UNLV). We thank Dianne Bangle and Jessica Spencer for help collecting samples at two sites, the Oregon State University Seed Laboratory (Corvallis, OR) for extracting samples, the UNLV research greenhouse for providing space, Kathryn Prengaman and Wes Niles (UNLV) for help with seed identification, Sharon Altman and Cayenne Engel (UNLV) for help preparing figures, and two anonymous reviewers for helpful comments on the manuscript. Any use of trade names is for descriptive purposes only and does not imply endorsement by the US Government.