Abstract
ABSTRACT The Brazil-nut tree (Bertholletia excelsa) is native to the Amazon rainforest, and its fruit production varies naturally with climatic conditions. Our aim was to evaluate the temporal variation in Brazil-nut production associated with climatic variables, including the strong El Niño of 2015/2016. The study was carried out in two 9-ha permanent plots in the northeastern Brazilian Amazon from 2007 to 2018: one in forest (12-year monitoring) and the other in savannah/forest transition (eight years). Overall, we monitored fruit production of 205 trees with diameter at breast height ≥ 50 cm. Annual fruit production was related to temporal series (2005-2018) of climatic data (the Oceanic Niño Index; and precipitation and air temperature from two local meteorological stations). Average fruit production per tree in 2017 was eight times lower than in 2015 and two times lower than the general average for both sites, and was significantly associated to the El Niño of 2015/2016, that increased average maximum monthly temperature and reduced the precipitation in the region, extending the dry season from three to six months. Years with higher and lower fruit production per tree coincided in both sites. Annual fruit production was significantly and negatively correlated with thermal anomalies that occurred in the third semester prior to harvest monitoring. Years with higher production were related with predominance of neutrality or the La Niña phenomenon at the global scale, and higher rainfall at the local scale. The relationship of fruit production with climate was independent of the local habitat.
Highlights
The Brazil-nut tree (Bertholletia excelsa Bonpl.) has been undergoing a process of domestication by amerindian peoples in the Amazon region since pre-Columbian times (Levis et al 2018), and has great socioeconomic and cultural importance in the region today (Salomão 2014)
In order to test the hypothesis that the drastic decrease in fruit production of Brazil-nut trees in 2017 was associated with the effects of a strong climatic anomaly, the 2015/2016 El Niño phenomenon, we evaluated Brazil-nut tree production across a series of years (2007-2018)
The local increase in the average maximum monthly temperature during the second semester of 2015 and the first months of 2016 in the study area corroborate the description of this period as a strong El Niño
Summary
The Brazil-nut tree (Bertholletia excelsa Bonpl.) has been undergoing a process of domestication by amerindian peoples in the Amazon region since pre-Columbian times (Levis et al 2018), and has great socioeconomic and cultural importance in the region today (Salomão 2014). The species has a long and synchronous flowering period that occurs during six months (Rathcke and Lacey 1985), normally in the dry season (Tonini 2011). The period between the emission of the first floral buds and maturation of the fruits is about 15 months and fruit dispersion occurs during the rainy season (Moritz 1984; Tonini 2011; Wadt et al 2018). There is a large intrapopulational and intraindividual yearly variation in fruit production (Kainer et al 2006; Pedrozo et al 2015), which may be due to crown characteristics such as sociological position and vine infestation (Wadt et al 2015), tree age and size, mainly stem diameter (Neves et al 2015), soil nutrients (Costa 2018), spatial location of trees and support capacity of different forest typologies (Batista et al 2019), or interaction with pollinators and climate factors such as rainfall (Wadt et al 2018)
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