Aggressive ruderal plant species pose an increasing problem in anthropically degraded lands. They both affect and are affected by other vegetation and by soil fertility in their surroundings. This study explores the case of the babassu palm (Attalea speciosa Mart., Arecaceae), which attains high dominance especially in frequently burned degraded lands throughout former Amazonia. We sought to understand the extent to which babassu palms affect their surroundings.
We investigated the interrelationships between different components within the plant-soil continuum, from aboveground vegetation and litter-layer to topsoil (0–5 and 5–15 cm) soil organic matter fractions, and soil physical (texture, porosity, density) and chemical (pH, nutrient contents and topsoil carbon stocks) characteristics. We developed a case-study in two secondary forests in different stages (3 year.-old and 20 year.-old) and sampled 12 plots in each, covering a wide range of babassu biomass proportions (0.3–98.7% of total aboveground biomass).
Babassu sequesters soil carbon, as indicated by the significantly higher C:N-ratio in the litter-layer, higher concentration of low-density (labile) organic matter, higher C-concentrations in labile SOM, and an overall increase in belowground C-stocks. The babassu palm decreases aboveground-belowground complexity by building stronger interactions via changes in the litter layer and in SOM-fractions.
Our results indicate that single-species dominance can centralize ecosystem interactions to favor the dominant species and that guaranteeing high species diversity and sequestering carbon may constitute mutually exclusive management objectives.