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Floristics of soil seed banks on agricultural and disturbed land cleared of tropical forests

Weerasinghe, Madhushi, Ashton, Mark S., Hooper, Elaine R., Singhakumara, Balangoda M. P.
Restoration ecology 2019 v.27 no.1 pp. 138-147
buried seeds, disturbed land, ferns and fern allies, germination, grasses, growth habit, herbs, land use, monitoring, multivariate analysis, plantations, rain forests, reforestation, shrubs, soil, species richness, tea, trees, tropical forests, vines, woody plants, Sri Lanka
Little is known about how soil seed banks vary in germination, composition, and density under different land uses after tropical forest conversion. Seed banks can potentially act as one source of regeneration for reforestation of old agricultural lands. Our study documents the composition and density of germinants in soil seed banks from four land uses types surrounding the Sinharaja forest in southwest Sri Lanka. These include: (1) kekilla fern lands; (2) pine plantations; and (3) tea. These were compared to the adjacent (4) mature rainforest. During the 6‐month period of monitoring, we recorded 1,674 germinants (0.036 germinants/cm³ soil), representing 46 species. Germinants of tree and shrub species were restricted to the pine and rainforest soils and all of them are considered pioneers. The soils of the rainforest had the lowest species richness, density, and diversity of germinants; tea lands comprised much higher richness, Shannon diversity, and density. However, almost all germinants in tea were grasses and herbs as compared with other land uses. A multivariate analysis of the germinants of soil seed banks revealed that the four land use types comprise very different compositions and abundances, some of which can be associated with differences in growth habit (trees, shrubs, vines, herbs, grasses). Our results suggest that pine plantations may facilitate some tree and shrub regeneration. However, the seed banks beneath tea and kekilla fern land do not comprise any woody plant species. This may explain why agricultural lands such as tea do not revert back to forest easily.