Abstract
Soil seed banks have been used for investigation of natural regeneration of forests. In this study, we compared seed density and species composition of soil seed banks of trees among natural forests, restored forests of different ages, and abandoned agricultural land. The soil seed banks were collected from a natural forest (NF), 12-year-old and 17-year-old restoration sites (RF12y and RF17y), and 17-year-old abandoned site (AA) at Ban Mae Sa Mai, Chiang Mai, Thailand. A seedling emergence technique was used to assess seed density and species of emerged seedlings was identified. We found 5-8 tree species at each site. Seed densities in the study areas ranged from 43 to 298 seeds/m2. The seed density of RF12y was significantly higher than that of both NF and AA but not significantly different than RF17y (p < 0.01). Although there was no significant relationship between the restoration ages and the seed densities of the soil seed banks, the species composition of standing vegetation was related to the seed bank species. Sorensen’s similarities between the species composition of the soil seed banks and the existing trees in each area were between 0 and 13.79%, suggesting seed dispersal of both within and across study sites. Eight out of fourteen species in the soil seed banks were dispersed into restoration sites without standing vegetation of those species. Seven of those were animal-dispersed species. The selected native trees, framework species, attracted small seed dispersers into the study areas, especially at the restoration sites. This finding suggests that active forest restoration improved natural regeneration in restoration sites as well as neighboring areas via seed dispersal.
Highlights
A soil seed bank consists of viable seeds resting in litters and soils (González-Rivas et al, 2009)
The forest restoration sites in this study were planted using the “framework species method” in 1998 and 2003, while the abandoned areas were left for natural regeneration since 1998
The species richness of both sites was slightly larger than RF12y and abandoned site (AA)
Summary
A soil seed bank consists of viable seeds resting in litters and soils (González-Rivas et al, 2009). Soil seed banks are often studied as part of investigations into natural regeneration of disturbed areas as well as abandoned sites (Chen et al, 2013; González-Rivas et al, 2009; Kostel-Hughes et al, 1998; Martins and Engel, 2007). Seed density and species richness are important factors for understanding soil seed banks (dos Santos et al, 2013; González-Rivas et al, 2009; Kostel-Hughes et al, 1998;). Species in the soil seed bank consists of herbs and grasses. Vol 5(1): 167-180, April 2021 higher seed density than those found in the older forests, even though the proportion of woody species seeds became greater in the old ones (Cao et al, 2000)
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