Demography of the Clonal PalmPrestoea Acuminatain the Colombian Andes: Sustainable Household Extraction of Palm Hearts

Abstract

Prestoea acuminata is a highland clonal palm traditionally used as a source of palm hearts by the Awá Indians of Colombia and Ecuador; its commercial use thrived in the 1980´s. Extraction pressure on the resource is particularly strong during Holy Week, as campesinos use it as a substitute for meat. We studied P. acuminata demography at La Planada Reserve, southwestern Colombia, and elaborated a ramet-based matrix model to assess the impact of different palm heart harvest regimes. The 1.5 ha study area had 1182 genets, composed of 5389 ramets. Harvestable stems were 23-40 years old and accounted for 0.32% of the stable stage distribution (SSD). Ramet population asymptotic growth rate  was 1.0485, and was more sensitive to changes in the survival of stemless ramets. Observed stage distribution (OSD) differed from predicted SSD, which suggests the population was exhibiting transient dynamics. As our census was conducted four years after a severe ENSO, we argue that the OSD could be reflecting this environmental disturbance. Thus, harvest simulations must be interpreted with caution. Although P. acuminata ramets are abundant at La Planada, the typical genet architecture, with many stemless ramets (20) and only 1-2 stems appropriate for palm heart extraction, accounts for a very low resource yield (127 palm hearts ha -1 in our survey). This, and its slow growth rate, make P. acuminata suitable only for household extraction. As harvest has a strong effect on sexual recruitment, we recommend a maximum annual extraction of 10% of harvestable ramets. Key words: Arecaceae, La Planada, Matrix ProjectionResumen Prestoea acuminata es una palma clonal de tierras altas utilizada tradicionalmente como fuente de palmito por los indígenas Awá de Colombia y Ecuador, que fue explotada comercialmente en los años 1980's. La presión de extracción sobre el recurso es particularmente fuerte durante la Semana Santa, pues los campesinos lo consumen en reemplazo de la carne. Para evaluar el impacto de diferentes regímenes de cosecha, estudiamos la demografía de P. acuminata en la Reserva La Planada, suroccidente de Colombia, y elaboramos un modelo matricial para los rametes. Las 1.5 ha estudiadas tenían 1182 genetes compuestos de 5389 rametes. Los tallos cosechables tenían 23-40 años y representaron el 0.32% de la distribución estable de estados (SSD). La tasa de crecimiento asintótico para los rametes fue de =1.0485, siendo más afectada por cambios en la supervivencia de los rametes sin tallo. La distribución observada de estados (OSD) y la SSD estimada fueron significativamente diferentes, lo que sugiere que la población estaba atravesando por dinámicas transitorias. Dado que nuestro censo se llevó a cabo cuatro años depués de un severo El Niño, argumentamos que la distribución observada podría estar reflejando esta perturbación ambiental. Por lo tanto, las simulaciones de cosecha deben ser interpretadas con precaución. Aunque los rametes de P. acuminata son abundantes en La Planada, la arquitectura típica de un genete, con m...

Population modelling and genetics of a critically endangered Madagascan palm Tahina spectabilis

“…Some studies have found such habitats provide advantage for palms by increasing survivorship and reducing herbivory (Berry, Gorchov, Endress, & Stevens, 2008), and this may be the case for T. spectabilis . Many palm species are utilized by humans for a variety of purposes, such as the consumption of the palm heart and harvesting of palm leaves for thatch and a variety of other purposes (Gamba‐Trimiño et al, 2011; Gruca et al, 2016; Jansen et al, 2018; Martínez‐Ballesté et al, 2005; Navarro et al, 2011; Reis et al, 2000). Previous studies of palm demography have demonstrated that loss of palm leaves can reduce palm survival, growth and reproduction (Mandle & Ticktin, 2012; Martínez‐Ramos et al, 2010; Ratsirarson et al, 1996;).…”

“…The consumption of heart of palm has been documented as a widespread practice in Madagascar that potentially impacts on Critically Endangered palm species (Gruca et al, 2016; Shapcott et al, 2012). Given the long generation time of T. spectabilis , the critically small population sizes and the hapaxanthic reproductive lifecycle, this species is particularly vulnerable to impacts of heart of palm consumption as it kills the plants before they can reproduce (Gamba‐Trimiño et al, 2011; Shapcott et al, 2012).…”

“…We used the detailed analysis of the TS1 population structure and relative locations and sizes of individuals in 2008 and 2016 to determine estimates of the numbers of individuals remaining in the same size category and those that transitioned to the next developmental stage in the eight year time step. Thus, calculations of survivorship (stage specific survivorship Ss i ) and transition probabilities (stage‐transition survivorship S i ) between development stages based on methods of Akçakaya, Burgman, and Ginzbur (1999), Gamba‐Trimiño et al (2011) and Simmons et al (2012).…”

“…Some local measures have been put in place at the original locations first visited in 2008 to protect T. spectabilis from fire and cattle trampling, considered to be threats to this species in situ (Gardiner, Rabehevitra, Letsara, et al, 2017; Gardiner, Rabehevitra, & Rajaonilaza, 2017). Demographic population modelling approaches have been widely used in palm studies to predict the impacts of differing threats on species including fire, grazing and harvesting and have proven a useful tool for conservation management (Arneaud et al, 2017; Gamba‐Trimiño, Bernal, & Bittner, 2011; Mandle & Ticktin, 2012; Martínez‐Ballesté, Martorell, Martínez‐Ramos, & Caballero, 2005; Melito et al, 2014; Navarro, Galeano, & Bernal, 2011; Pinéro, Martinez‐Ramos, & Sarukhan, 1984). The application of these approaches to investigate T. spectabilis population growth is likely to provide insights into its long‐term viability.…”

“…Demographic population modelling approaches have been widely used in palm studies to predict the impacts of differing threats on species including fire, grazing and harvesting and have proven a useful tool for conservation management (Arneaud et al, 2017;Gamba-Trimiño, Bernal, & Bittner, 2011;Mandle & Ticktin, 2012;Martínez-Ballesté, Martorell, Martínez-Ramos, & Caballero, 2005;Melito et al, 2014;Navarro, Galeano, & Bernal, 2011;Pinéro, Martinez-Ramos, & Sarukhan, 1984). The application of these approaches to investigate T. spectabilis population growth is likely to provide insights into its long-term viability.…”