Ecology of native oil-producing palms and their potential for biofuel production in southwestern Amazonia

In the midst of a worldwide explosion of interest in biofuels, concern has arisen over displaced food crops, greenhouse gas emissions, forest conversion and biodiversity loss. These issues notwithstanding, biofuels are promising as a local fuel source in rural areas of Amazonia, where communities depend on fossil fuels for transportation and electricity generation. This study evaluates the potential of two native Attalea palm species in southwestern Amazonia as a source of oil for biofuel, and generates ecological knowledge to facilitate sustainable management of these species for oil. Attalea palms are common to forests as well as pastures in Amazonia, and their fruits contain copious amounts of oil. I compared flowering and fruiting phenologies of Attalea phalerata Mart. ex Spreng. and Attalea speciosa Mart. ex Spreng. (Arecaceae) in actively grazed pastures and old-growth forests of Acre and Rondonia, Brazil, over 24 months, and combined these observations with data on palm densities, fruit characteristics and oil contents to assess biofuel potential. To better understand the persistence of A. phalerata palms in disturbed landscapes, we also studied the recovery of A. phalerata palms after slash-and-burn agriculture using a before-after-controlimpact (BACI) deforestation experiment.;We found greater inflorescence and infructescence production in pastures than in forests, and generally male-biased inflorescence sex ratios among individuals of both Attalea species. At the population level, pasture palms demonstrated elevated reproductive activity, bearing flowers and mature fruits year-round, while reproductive phenophases of forest palms were more cyclic, with isolated flowering peaks and consecutive months of inactivity. Light availability was positively correlated with inflorescence production, and specifically with pistillate inflorescence, although less so in A. phalerata than in A. speciosa. The size of the leaf crown (i.e., number of leaves) was positively correlated with reproductive activity for both species in pastures, but not in forests. Total palm height had no apparent effect on inflorescence production. Results suggested that female function is more sensitive than male function to environmental stress and resource limitations. Increased access to light and larger crown size shifted Attalea sex expression towards increased female function and greater productivity primarily during the early stages of bud initiation and development through the regulation of sex determination and bud abortion.;Just 14 months after deforestation and burning, our analyses showed no overall effect of slash-and-burn on A. phalerata palm population densities or size class relative abundances. Pre-adult palms persisted in the slash-and-burn area through resprouting of new leaves, but there was relatively little germination. Protection of the apical meristem below-ground and the capacity to continue leaf production following damage characterizes resprouting in palms were critical to Attalea survival. Within slash-and-burn plots, we detected accelerated growth rates in younger palms. Leaf production by surviving A. phalerata seedlings, post-seedlings, and pre-juveniles was so successful in slash-and-burn plots that 73% returned to or surpassed their original number of leaves 14 months after disturbance. Our results confirm that A. phalerata populations quickly recover after slash-and-burn agriculture, and will likely constitute a principal component of the future regenerating forests in the Southwestern Amazon.;In isolated rural Amazonian communities, naturally occurring populations of oleaginous plants represent a largely underexploited energy resource and can serve as an important and immediate source of fuel for electrification and transportation (e.g., river boats, small trucks, or even small airplanes). In a single year, an average A. phalerata palm produced more than three times as many infructescences in pasture than in forest, and A. speciosa produced more than twice as many. A. phalerata palms in old-growth forest produced an average 1.17 L palm -1 yr-1 of oil, and in pasture, 4.55 L palm -1 yr-1, while A. speciosa growing in forest produced 0.93 L palm-1 yr-1 and in pasture, 2.59 L palm-1 yr-1. Energy production from locally available plant resources promises greater independence and improved livelihoods for remote communities, while assigning greater value to standing forests and diversifying pasture systems already under use.