Estimating soil seed bank characteristics in ponderosa pine forests using vegetation and forest-floor data

Abstract

Abstract-Soil seed banks are important for vegetation management because they contain propagules of species that may be considered desirable or undesirable for site colonization after management and disturbance events. Knowledge of seed bank size and composition before planning management activities facilitates proactive management by providing early alerts of exotic species presence and of abilities of seed banks to promote colonization by desirable species. We developed models in ponderosa pine (Pinus ponderosa) forests in northern Arizona to estimate the size and richness of mineral soil seed banks using readily observable vegetation and forestfloor characteristics. Regression models using three or fewer predictors explained 41 to 59 percent of the variance in 0-to 2-inch (0-to 5-cm) seed densities of total and native perennial seed banks. Key predictors included aboveground plant species richness/10.8 ft 2 (1 m 2 ), litter weight and thickness, and tree canopy type (open or closed). Both total and native perennial seed banks were larger and richer in plots containing: (1) species-rich understories, (2) sparse litter, and (3) tree canopy openings. A regression tree model estimated that seed bank density of native perennials is 14-fold greater if aboveground plant richness exceeds eight species/10.8 ft 2 , forest-floor leaf litter is < 1 inch (2.5 cm) thick, and tree canopies are open.

Soil seed banks in a mature coniferous forest landscape: dominance of native perennials and low spatial variability

“…Using a systematic gradient design might be useful to explore potential finer-scale variation in seed banks in our study area. Lack of relationship between seed banks and site-level tree canopy cover contrasts sharply with a previous study 250 km to the south-east of ours, on a P. ponderosa forest landscape, where seed density was threefold greater below open compared to dense canopies (Abella and Springer, 2008). Some previous studies in western USA coniferous forests found that, contrasting with our results, seed banks differed among ecosystem and forest types within landscapes (Kramer and Johnson, 1987;Abella et al, 2007).…”

Is the soil seed bank a reliable source for passive restoration of bush-cleared semi-arid rangelands of South Africa?

“…Our results highlighted that effective passive restoration soon after bush clearing depends upon seed production, particularly of early successional species rather than persistent seed bank. Under these circumstances, post-clearing management of aboveground vegetation including protection of already existing vegetation is key to increase seed production and species richness (Abella and Springer 2008). In general, similarity between SSB and AGV at Kgomokgomo was low although it increased with time in cleared microsites (Fig.…”