Factors controlling the regenerative cycle of Thymus funkii subsp. funkii in a semi-arid gypsum steppe: A seed bank dynamics perspective |
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| Authors: | E Martínez-Duro P Ferrandis JM Herranz |
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| Institution: | 1. Kansai Research Center, Forestry and Forest Products Research Institute, Nagai-kyutaro, Momoyama, Fushimi, Kyoto 612-0855, Japan;2. Department of Bioapplications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology, 2-24-16 Koganei, Tokyo 184-8588, Japan;3. National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan;4. Atomic & Molecular Physics Laboratory, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan;5. Surface Chemical Analysis G., National Institute for Materials Science, 1-2-1 Sengen, Tsukuba-shi, Ibaraki 305-0047, Japan;6. Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1205, Japan;7. Synchrotron Analysis L.L.C., 3-1-2 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1205, Japan;8. Forestry and Forest Products Research Institute, Matsunosato, Tsukuba, Ibaraki 305-8687, Japan;1. MPG Ranch, Florence, MT 59833, USA;2. Department of Geosciences, University of Montana, 59801, USA;3. College of Forestry and Conservation, University of Montana, 59801, USA;4. Interdisciplinary Sciences, University of Montana, 59801, USA;1. Southern Cross GeoScience, Southern Cross University, Lismore, NSW, Australia;2. Federation University, Ballarat, VIC, Australia;1. W.M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, 925N. Mills Ave, Claremont, CA 91711, United States;2. Department of Geoscience, University of Nevada Las Vegas, 4505S. Maryland Pkwy, Las Vegas, NV 89154, United States;3. School of Life Sciences, University of Nevada Las Vegas, 4505S. Maryland Pkwy, Las Vegas, NV 89154, United States |
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| Abstract: | We researched the soil seed bank dynamics of Thymus funkii subsp. funkii, a gypsovag shrub endemic to the southeastern Iberian Peninsula, to determine possible reasons for low recruitment in isolated populations growing on crusted gypsum soils. Recruitment-restriction hypotheses involving main factors in the seed bank dynamics were analysed, and a diagrammatic dynamics model drafted from a population perspective. Viable seed production averaged 362 per plant. Seed shadows resulting from primary dispersal were concentrated under the mother plant. There were two thyme-seed predators: coleopteran larvae (pre-dispersal phase) and Messor bouvieri ants (pre- and post-dispersal phases), which predated 16.4% and 3.8% of population yield, respectively. However, ants may simultaneously contribute to the spatial secondary dispersal, since they lost a small fraction of seeds they harvested. Seeds showed innate physiological dormancy to high summer temperatures, although this disappeared rapidly. The response of germination to other temperature × light conditions was wide and rapid. No permanent seed bank was detected in the soil. Seeds buried in the upper soil layer (2 cm) germinated highly and fast. In contrast, a significant fraction of seeds buried deeply (8 cm) remained viable for over one year. Germination in the field accounted for only 1.0% of the seed output, and seed death due to pathogen attack and aging was also low (3.0%). Seedling emergence was confined to autumn and showed a high correlation with total plant cover, irrespective of plant species. Seedling survival was very low. The small spatial correspondence between primary dispersal and seedling emergence patterns may reflect the importance of secondary dispersal in T. funkii seed bank dynamics. Hypotheses and consequences of such horizontal seed movements for conservation management are discussed. |
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