1 / 20

Grupo de Ecología del Desierto Departamento de Biología Universidad Nacional de San Juan

Grupo de Ecología del Desierto Departamento de Biología Universidad Nacional de San Juan.

ward
Download Presentation

Grupo de Ecología del Desierto Departamento de Biología Universidad Nacional de San Juan

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Grupo de Ecología del DesiertoDepartamento de BiologíaUniversidad Nacional de San Juan Dr. Eduardo Pucheta – Prof. Titular Ecología, Dpto. Biol.Lic. Yanina Ribas-Fernández - Becaria CONICET, Adscripta docenteLic. Laura Quevedo-Robledo - Becaria CONICET, Adscripta docenteLic. Victoria García - Lic. en Biología, Becaria FONCyT, Adscripta docenteMario Gatica – Estudiante de Biología, Adscripto alumnoOctavio Gerlo – Estudiante de Biología, Adscripto alumno

  2. Are density and identity of the germinable seed bank (GSB) of annual plants dependent on previous rainfall? • Is there any interaction between rainfall and microhabitat to control seed density and species identity in the GSB of annuals? • How is the seed depletion process in transient seed banks? • Are seed depletion mechanisms rainfall-dependent? Influences of rainfall and vegetation patches on persistent and transient seed banks in central Monte, Argentina

  3. Top-down filters Seed production and dispersal Rainfall Persistent and transient seed banks Bottom-up filters Vegetation patches Bare ground Plant regeneration

  4. 1. Influences of interyear variability and microhabitat on the identity and density of the germinable seed bank of annual plants in a sandy Monte desert 2. Seed fate in the desert shrub Bulnesia retama along a precipitation gradient in central Monte ±200 mm rainfall gradient

  5. Persistent seed bank1. Influences of interyear variability and microhabitat on the identity and density of the germinable seed bank of annual plants in a sandy Monte desert Methods Study site We collected 3 composite soil samples 10 cm diameter and 5 cm depth on bare ground and under shrub patches (N=30) after seed rain for two years (May 2002 and July 2003) We assessed the GSB in a greenhouse after cold treatment for 4 weeks.

  6. Persistent seed bank1. Influences of interyear variability and microhabitat on the identity and density of the germinable seed bank of annual plants in a sandy Monte desert Below-avg rainfall 75.1 mm (2001-2002) Above-avg rainfall 138.9 mm (2002-2003) Some annual plant species showed indicator values (P<0.05) for different combinations of growing season and microhabitat type (Indicator species analysis). Portulaca grandiflora, Sclerophylax arnottii, Chenopodium murale Chenopodium papulosum Bare ground The interaction of growing season and microhabitat showed non-additive effects for species composition, resulting in four significant species-assemblages (MRPP). Boopis sp., Tribulus terrestris, Gomphrena mendocina Amaranthus standleyanus, Portulaca umbraticola, Vegetation patches

  7. 138.9 mm (Oct-Apr) 75.1 mm (Oct-Apr) Persistent seed bank1. Influences of interyear variability and microhabitat on the identity and density of the germinable seed bank of annual plants in a sandy Monte desert Interyear variability was more important than microhabitat explaining seed bank density variation. Despite there was no significant interaction between rainfall and microhabitat, there is an “apparent” interaction to be tested in the long-term. New question Is there any effect of rainfall and microhabitat on the germinable fraction of the persistent seed bank? J. Arid Enviro. In press

  8. 118.4 mm 150 mm 154.5 mm 329 mm Transient seed bank 2. Seed fate in the desert shrub Bulnesia retama along a precipitation gradient in central Monte

  9. Transient seed bank 2. Seed fate in the desert shrub Bulnesia retama along a precipitation gradient in central Monte 118.4 mm 150 mm 154.5 mm 329 mm

  10. Methods On each location (4 independent Bulnesia retama populations) and for two years we installed 4 rain gauges and selected 10 individuals and 10 adjacent bare soils, where we studied bimonthly: • Branch exclusion • Temporal counts up to >90% dispersal • Soil samples • Seed germination Transient seed bank 2. Seed fate in the desert shrub Bulnesia retama along a precipitation gradient in central Monte • Predispersal fruit losses • Fruit dispersal • Seed bank dynamics • Postdispersal seed losses

  11. Predispersal fuit losses to consumers Fruit consumption increased with time after fruit maturation (R2 = 0.12; F = 33.18; P = <0.0001) similarly in all 4 sites (F = 0.21; P = 0.886). Annual rainfall did not explain fruit consumption (F = 0.29; P = 0.589).

  12. How does fruit dispersal is? Dispersal slopes were year and site dependent, But rainfall correlated weakly with dispersal (data not shown).

  13. How does rainfall affect B. retama soil seed bank? Early seed bank increased their density and spatial variance with rainfall. Accumulated rainfall up to the beginning of the Autumn seems to impose an upper limit to the amount of seeds that could be stored in soils. Seed bank may reflect seed production.

  14. How does rainfall affect B. retama soil seed bank? Late seed bank decreased their density and spatial variance with rainfall. Accumulated rainfall imposed an opposite upper limit to the amount of seeds that could be stored in soils. Late seed bank depletion may be associated to rainfall.

  15. Is seed germination a mechanism explaining seed loss? Rainfall explained seed germination in early and late seed banks. Seed germination was explained by rainfall similarly in bare soils and in undercanopies.

  16. Is seed germination a mechanism explaining seed loss? Rainfall explained seed germination in early and late seed banks. Seed germination was explained by rainfall similarly in bare soils and in undercanopies.

  17. Seed production and dispersal Rainfall Persistent and transient seed bank Top-down filters Vegetation patches Bare ground Plant regeneration Bottom-up filters

  18. Top-down filters Fruit consumption Seedling consumption Microsite effects Bottom-up filters Predispersal seed losses Fruit dispersal Rainfall Vegetation patches Bare ground Seed bank dynamics Seed germination Postdispersal seed losses Seedling establishment Plant regeneration

  19. Influences of rainfall and microhabitat on persistent and transient seed banks in central Monte desert GSB of annual plants • Observed patterns in seed density and species identity were related to the amount of rainfall in the previous growing season and to microhabitat type Seed fate in B. retama shrubs • Predispersal seed loss was independent from rainfall, but dependent on time since fruit maturation, • Microsites were important in determining soil seed densities, but they were unimportant for seed germination rates, • Rainfall partially explained seed germination, but there were more seeds in soils under higher rainfall, suggesting an effect of rainfall on fruit production.

  20. Future plans Influences of rainfall and microhabitat on persistent and transient seed banks in central Monte desert: a long-term study Muchas gracias!

More Related