Spatial coherence between seasonal seed banks in a semi-arid gypsum community: density changes but structure does not

Abstract

Seed banks play a crucial role in arid plant communities because they confer stability and long-term persistence. However, seed banks have high temporal and spatial variability, with dramatic changes in density and composition. The aim of this study was to test whether seasonal change affected seed bank community structure and spatial pattern. Moreover, we wanted to know if the effect driven by environmental factors on the seed bank was constant year round. We sampled the seed bank at 188 points along seven parallel transects through a gypsum system in central Spain. Soil samples were taken twice (September and April) in contiguous plots. In each plot we measured environmental parameters, including micro- and macroslope, vegetation band, shrub cover, lichen crust cover and landform. A nearly threefold decrease in seed bank density occurred between September (16,230 seeds m–2) and April (5960 seeds m–2). Seasonal changes in density varied widely among species; however, a seed bank was present for most species at both sampling dates. For several well-studied species (Lepidium subulatum and Helianthemum squamatum), seed losses were within the range of losses by emergence reported in the literature. In both seasons, seed bank composition was controlled mainly by community band and microslope. Sampling season had a significant, but minor effect on seed bank composition. Moreover, a high spatial correlation existed in terms of seed density and richness through the two studied seasons. These results show that the seed bank keeps a constant structure even under substantial variation in density.

Seed banks in a degraded desert shrubland: Influence of soil surface condition and harvester ant activity on seed abundance

“…a Caballero et al, 2003Caballero et al, , 2005 Cabin and Marshall, 2000. c Guo et al, 1998. d Chambers et al, 1991.…”

“…A reduction in organic debris that contains ripening infructescences may diminish inputs into the seed bank and decrease the capture of wind-blown seeds as they disperse across disturbed surfaces. Disturbances often remove shrub canopies where seeds are concentrated after seed rain and where seeds of annual and perennial grasses and forbs accumulate as they disperse from shrub interspaces (Nelson and Chew, 1977;Price and Reichman, 1987;Guo et al, 1998;Marone et al, 1998;Caballero et al, 2003Caballero et al, , 2005Caballero et al, , 2008Li, 2008). Large or small soil particle sizes entrap like-sized seeds (Price and Reichman, 1987;Chambers et al, 1991;Chambers, 1995), so disturbance-induced shifts in particle sizes will likely change the abundance and species composition of seeds and the resulting establishment of seedlings.…”

Does aboveground vegetation composition resemble soil seed bank during succession in specialized vegetation on gypsum soil?

“…The ecology of gypsum plant communities has been much studied recently (e.g., Meyer 1986;Guerrero-Campo et al 1999a, b;Escudero et al 1999Escudero et al , 2000Palacio et al 2007;Pueyo and Alados 2007), including their seed banks at small spatial and temporal scales (see Escudero et al 1997;Caballero et al 2003Caballero et al , 2005Caballero et al , 2008Olano et al 2005) and aboveground succession both primary (Mota et al 2003;Dana and Mota 2006) and secondary (Martinez-Duro et al 2010). However, many aspects of gypsophile community dynamics and the relationship between aboveground vegetation and seed bank composition during succession remain unknown.…”

“…Seed banks are especially important in gypsum steppes because of the limitations imposed by the particular physical and chemical characteristics of the soil, and the aridity of the climate (Bertiller 1998;Figueroa et al 2004;Caballero et al 2005). It has been suggested recently that community dynamics in this specialized system may be based on a close relationship between the aboveground and seed bank components at small scales that varies slowly over larger temporal and spatial scales (Caballero et al 2008).…”

Seasonal dynamics in alpine meadow seed banksalong an altitudinal gradient on the Tibetan Plateau

“…Funes et al 2003;Caballero et al 2005). Onipchenko et al (1998) showed that alpine plants have lower biomass and seed production as adaptations to severe environments.…”