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Biology of Dryland Plants

Mandujano, Maria [1].

Demography of dryland plants.

Size-stage classified population matrix models have been used to describe the structure and dynamics of desert plants and to explore how spatial and temporal environmental heterogeneity influence population dynamics. Matrix models provided complementary information on population dynamics and the life history, and even though the potential of these models has been demonstrated, demographic studies of desert plants are scarce. Summarizing the available information, the finite rate of population growth (l) varied among species, but generally yielded l ca. 1, micro endemic rare species are an exception were l < 1. Dominant elements or invasive species under some particular rainy years shown l > 1, and shrub species fluctuate among years or sites from low l < 1 to huge population rates of increase (l ca. 14). Reproductive value increased monotonically with plant size with few exceptions, but dominant landform species produced orders of magnitude more offspring than rare species. Prospective analyses showed that sensitivity values were highest for sexual recruitment in all populations, suggesting environmental bottlenecks in these transitions. Absence of recruitment in succulent species is the most common pattern reported whereas woody species show low, but constant recruitment. Elasticities summed over size-classes or demographic processes differed widely between years, habitats and species. In general stasis show the highest elasticities and sexual recruitment the lowest. However plotting elasticities of different species in GLF demographic triangle indicate that species with clonal propagation shifted upwards in the triangle (increase growth with respect to survival). Matrix models aptly summarize the striking spatial and temporal differences found in the structure, population dynamics and life history traits of desert plants. With sufficient demographic data, these models can be used in decision making to preserve threatened species, fix carrying capacities and to assess the effects of different factors (e.g. interactions) on population dynamics.


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1 - Universidad Nacional Autonoma de Mexico, Instituto de Ecologia, Ciudad Universitaria, A.P. 70-275, Mexico, D.F., 04510, Mexico

Keywords:
demography
arid and semi-arid environments
prospective analysis
matrix population models.

Presentation Type: Symposium or Colloquium Presentation
Session: 49-15
Location: Salon K - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 3:30 PM
Abstract ID:139


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