A model for the importance of large arborescent palms in the dynamics of seasonally-dry amazonian forests

Abstract

In this study we propose a model that represents the importance of large arborescent palms in the dynamics of seasonally-dry Amazonian forests. Specifically, the model is aimed at guiding the investigation of the role of large arborescent palms on forest regeneration and succession. Following disturbance, the high level of luminosity reaching recently formed forest gaps favors the quick proliferation of shade-intolerant lianas that, by casting shade on the crowns of mature forest trees and increasing tree-fall probability, suppress forest succession. Due to their columnar architecture palm trees are, however, not severely affected by vines. As the palms grow, the canopy at the gaps becomes gradually higher and denser, progressively obstructing the passage of light, thus hindering the growth of shade-intolerant lianas and enabling late-successional tree development and forest regeneration. Owing to the long time associated with forest regeneration, the model cannot be tested directly, but aspects of it were examined with field data collected at an Attalea maripa-rich secondary forest patch within a matrix of well-preserved seasonally-dry forest in the Southeastern Amazon. The results indicate that (1) forest disturbance is important for the recruitment of large arborescent palms species, (2) these palms can grow rapidly after an event of disturbance, restoring forest canopy height and density, and (3) secondary forest dominated by palm trees species may be floristically similar to nearby undisturbed forests, supporting the hypothesis that the former has undergone regeneration, as purported in the model. Key words: Amazon, Attalea maripa, forest dynamics, palm trees, regeneration. ResumoNeste estudo propomos um modelo que representa a importância de palmeiras arborescentes de grande porte na dinâmica das florestas amazônicas sazonalmente secas. Especificamente, o modelo visa guiar a investigação do papel destas palmeiras na regeneração da floresta. Após um evento de perturbação, a alta luminosidade das clareiras recentes favorece a rápida proliferação de lianas dependentes de insolação que, sombreando as copas das árvores e aumentando sua probabilidade de queda, tendem a interromper o processo de sucessão. Devido a sua arquitetura colunar, as palmeiras arborescentes, no entanto, não são severamente afetadas por lianas. À medida que estas palmeiras crescem, o dossel das clareiras se torna gradualmente mais alto e denso, limitando desta forma o crescimento das lianas e permitindo o desenvolvimento das árvores de estádios sucessionais tardios e, consequentemente, a regeneração da floresta. Devido ao longo período associado à regeneração da floresta o modelo não pode ser testado diretamente, mas aspectos deste foram examinados com dados de campo coletados em uma mancha de floresta secundária rica em Attalea maripa em uma matriz de florestas primárias bem preservadas no sudeste da Amazônia. Os resultados revelam que (1) eventos de perturbação florestal são importantes para o recrutamento das palmeiras arboresce...

Impact of pre-Columbian “geoglyph” builders on Amazonian forests

“…In the Amazonian terra firme, palms are often the first trees to colonize forest clearings after herbs and lianas (53) but are eventually outcompeted by slower-growing trees (54). If humans stopped maintaining this artificial succession stage, palm communities would eventually be replaced by other species.…”

Historical ecology, human niche construction and landscape in pre-Columbian Amazonia: A case study of the geoglyph builders of Acre, Brazil

“…BP levels at FC1, JS1 and JS2. We can hypothesize that a wetter-than-previous climate at this time would, if anything, have discouraged the appearance of palm forest by favouring a denser forest canopy (Salm et al 2005), and that this phenomenon thus had its roots in coupled human-environment interactions (Watling et al 2017a). The increases in palms (which accompany overall increases in charcoal in the same locations) may have occurred through the re-visitation and re-utilization of these places in the landscape by successive generations of people, who were attracted to the useful plants concentratedintentionally or unintentionallyby previous people, and who in turn contributed further to their concentration.…”

“…We suggest that once humans stopped using and managing these locations within the landscape, the selective pressures acting upon these forests changed, this time favouring slower-growing, canopy-filling species. In southwest Amazonia, palms are favoured during an 'intermediate succession stage' following forest clearance, occurring after grasses and lianas and before eventually being out-competed by larger trees (Salm et al 2005). We might postulate that the geoglyph builders artificially maintained this succession stage and favoured the palm niche, which then became disfavoured once people abandoned this trajectory.…”

Conservation value of an exotic species: the case of coconuts on the Kayapo indigenous lands, south-eastern Amazonia

“…As the palms grow, the canopy at the gaps becomes gradually higher and denser, progressively obstructing the passage of light, thus hindering the growth of shade-intolerant lianas and enabling latesuccessional tree development and forest regeneration. We have examined aspects of this model in relation to a native palm species (Attalea maripa) (Salm et al 2005). We find no reason why coconut palms would not behave similarly and become important tools for environmental reconstitution of these highly threatened forests.…”