Species Richness, Spatial Variation, and Abundance of the Soil Seed Bank of a Secondary Tropical Rain Forest¹

Abstract

Despite the importance of the soil seed bank in tropical forest regeneration, little is known about spatial variability in species composition and abundance of seeds stored in the soil. To develop sampling methods for comparative studies, we examined species richness, spatial variation, and abundance of germinants from the soil seed bank in a 16 year old secondary, tropical wet forest at La Selva Biological Station, Costa Rica. Surface soil (10 cm deep, 4.7 cm diameter) was collected at the intersection points of a gridded 1 ha plot (10 × 10‐m grid, 121 samples) and in a nested 100 m2 subplot (2 × 2‐m grid, 36 samples). The 1 ha plot had a density of 4535 seeds/m2 with 34 species observed. Based on a series of 100 randomized species accumulation curves, a Michaelis‐Menten fit predicted a mean species richness of 36.3 species; the number of observed species was close to the predicted asymptote. A nonparametric, first‐order jackknife species richness estimator predicted a species richness of 37.0 species. Eighty‐five and 95 percent of the observed species richness is contained, on average, within 41 and 74 pooled samples, respectively. Within the 100 m2 nested subplot, a density of 5476 seeds/m2 was observed, comprising 26 species with an estimated species richness (Michaelis‐Menten fit) of 29.1 species. The jackknife species richness estimator predicted a species richness of 36.7 species. For species richness and abundance of both plots, spatial autocorrelation statistics (Moran's I) were not significantly different from zero at lag distances from 2 to 100 m, indicating a random distribution at these spatial scales. For this site, accurate estimates of species composition depend upon the number of samples collected as well as the spatial distribution of sampling effort. Many small samples distributed over a large area provide greater accuracy and precision for estimating species richness of the soil seed bank.

The seed bank of a gallery forest in Southeastern Brazil

“…Marked variation was observed in the seed stocks in the two periods sampled. In tropical forests, seasonal variations in the composition and density of the soil seed community may partly reflect the annual and seasonal modes of production, deposition and stocking of seeds in the soil (Dalling et al 1997(Dalling et al , 1998Butler and Chazdon, 1998;Dupuy and Chazdon, 1998). Additionally, factors such as the seasonal pattern of flooding and the constant removal and deposition of litter may affect the composition of the soil seed bank.…”

“…The composition and abundance of seed species in the soil, as well as the distribution of life forms, are influenced by factors such as floristic composition, the phenology of the local vegetation and disturbances occurring at the forest edge (Quintana-Ascencio et al, 1996;Butler and Chazdon, 1998). Gallery forests are considered areas of permanent protection in Brazil.…”

“…The role of soil seed banks in the regeneration of natural or man-made clearings has been extensively investigated in tropical forests, particularly since the floristic composition and density of the seeds stored in the soil may indicate the regenerative potential of a forest (Butler and Chazdon, 1998). The composition and abundance of seed species in the soil, as well as the distribution of life forms, are influenced by factors such as floristic composition, the phenology of the local vegetation and disturbances occurring at the forest edge (Quintana-Ascencio et al, 1996;Butler and Chazdon, 1998).…”

O banco de sementes e suas implicações na diversidade da Floresta Ombrófila Densa Submontana no Parque Estadual Carlos Botelho, São Paulo, SP, Brasil

“…A sazonalidade encontrada no banco de sementes pode estar relacionada à viabilidade das sementes no banco, que é influenciada por patógenos, predação (Orozco-Segovia et al 1993) e dormência das sementes (Whitmore 1998). Espécies que dispersam num período restrito de tempo e apresentam sementes de curta longevidade, podem compor o chamado banco de sementes transitório (Garwood 1989) e ocasionar alta variabilidade entre coletas (Dalling et al 1997, Butler & Chazdon 1998, Grombone-Guaratini et al 2004.…”

“…Estudos sobre os processos naturais que influenciam a dinâmica florestal têm mostrado que o banco de sementes é uma das principais fontes de recrutamento de novos indivíduos na sucessão secundária (Hall & Swaine 1980, Butler & Chazdon 1998, Hopfensperger 2007.…”