環境科学院 植物生態学セミナー   2011-10-18 (Tue) 10:30
(Room: A809 )

What determines seedbank persistence? Litter controls the movement and longevity of seeds in a post-mined peatland

Chika Egawa
(Chairperson: Saito )

Seedbank in temperate regions is classified as persistent or transient, according to whether the germinable seeds were detected throughout the year or not, respectively. The first crucial step in the formation of seedbank is burial. In general, deep buried seeds can keep viability until the second or some subsequent germination season, whereas seeds nearer the ground surface germinate and disappear soon. Ground surface environments significantly affect the vertical movement of seeds after landing, and therefore, should be closely related to seedbank persistence. Plant litter gradually covers the ground surface with succession. Litter accumulating process may change the fate of seeds and seedbank persistence.

We investigated 1) seed viability after one year burial at different depths and 2) vertical seed movement after landing for Drosera rotundifolia (seed mass 0.011 ± 0.003 mg), Lobelia sessilifolia (0.250 ± 0.041), Rhynchospora alba (0.873 ± 0.127) and Moliniopsis japonica (1.820 ± 0.403), in three different successional stages with different litter thickness on the post-mined peatland, Sarobestu Mire.

  1. Litter increased seed longevity for all the species. On the later successional stage, seeds of all the species showed high survival rates at the peat surface covered by thick litter. In contrast, seed survival rates at the peat surface were almost zero on bareground.
  2. Litter increased the provability of seed retention and decreased that of migration, in particular, for larger seeds. The largest seeds of M. japonica rarely reached the deeper layer throughout the year regardless of litter thickness. Many of small seeds of D. rotundifolia and L. sessilifolia migrated soon after landing, but 10-20 % of the dispersed seeds were trapped by litter on the later successional stage, and then moved down to the deeper layer until early spring.

Seedbank persistence of each species could change with succession, because litter accumulation determines both the seed longevity and vertical seed movement after landing in the post-mined peatland. These litter-controlling processes may be related to the changes in species richness and density of seedbank along succession.


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