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Titre : Estructura poblacional y dinámica de plántulas del cactus columnar Neobuxbaumia mezcalaensis (Bravo) Backeberg en la Cañada del Zopilote, Guerrero

POPULATION STRUCTURE AND SEEDLING DYNAMICS OF THE COLUMNAR CACTUS NEOBUXBAUMIA MEZCALAENSIS (BRAVO) BACKEBERG AT CAÑADA DEL ZOPILOTE

Auteur : Nova Muñoz, Elizabeth

Etablissement de soutenance : Colegio de Postgraduados (COLPOS) Consejo Nacional de Ciencia y Tecnología (CONACYT)

Grade : Maestría en Ciencias, Especialidad Forestal 2010

Résumé
The analysis of the population structure of a plant species provides information about natural processes and environmental factors to which each developmental stage has been subject through time. Such information is needed for designing strategies to use and preserve the species. The current work was aimed to analyze the population structure and seedling demography of Neobuxbaumia mezcalaensis three 50 X 50 m (2500 m2) observational plots were established at Cañada del Zopilote, Guerrero. All N. mezcalaensis individuals were registered, their diameter at breast height (dbh) and total height measured, and mapped through their coordinates X and Y. The Ripley´s index was used to determine the spatial distribution and spatial correlation patterns among developmental stages. A total of 20 woody and Cactaceae species were registered. Burseraceae family accounted for 29% of the registered species, followed by Cactaceae with 25% and Sapindaceae with 10%. The species with highest Index of Importance Value were N. mezcalaensis (46.1%) and Bursera morelensis (7.1%). The dbh distribution of N. mezcalaensis fitted the reverse “J” shape model, indicating a constant recruitment of new individuals. The spatial distribution pattern showed by N. mezcalaensis was markedly clumped in juvenile and adult developmental stages. However, the clumping intensity decreases with developmental stage and analyzed distance, that is some random patterns were detected for adults. For studying seedling dynamics, 15 plots (0.5 X 0.5) m were established. All new emerging seedlings were tagged and its growth and survival followed during one year. The height mean annual increment observed for seedlings was 0.78 cm year-1. Among most probable mortality causes were physical damage (31.6%) and drought (21.4%). However, 26.5 % of seedlings disappeared by unknown mortality causes. After one year of observation 64.8% of seedlings survived, which is a high rate compared with those reported for one-year seedlings of tree species.

Mots clés : Índice de Ripley ; Patrón de Distribución Espacial ; Patrón de Correlación Espacial ; Crecimiento en altura ; Tasas de Supervivencia ; Causas de Mortalidad ; Ripley´s Index ; Spatial Distribution Pattern ; Spatial Correlation Pattern ; Height Growth ; Survival rates ; Mortality Causes ; Maestría ; Forestal

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