Aquatic herbaceous plants of the Amazon floodplains: state of the art and research needed

Abstract

The Amazonian wetlands cover a vast area subject to a monomodal flood pulse with an annual amplitude averaging 10 m, which defines an aquatic phase and a terrestrial phase of great biological importance. According to the geological origin and the catchment areas, the physical and chemical properties of the wetland will vary, being defined two major groups, the várzeas and the igapós. Although aquatic herbaceous plants do occur in the two types, higher species richness and densities are typical of the várzeas where aquatic herbaceous species, particularly C 4 plants may exhibit high biomass values and net primary production-NPP about three times these of the floodplain forest. The aquatic herbaceous plants are very important in the carbon and nutrient budgets of the várzea, since through their decomposition they promote the enrichment of the aquatic system and associated floodplains, both during the aquatic and terrestrial phases of the hydrologic cycle. The major threats to herbaceous aquatic plants are related to the modification and contamination of the habitats owing to their use in economic activities as cattle and buffalo ranching and agriculture. Degradation improves the susceptibility of these systems to fire especially during the terrestrial phase, resulting in economic losses and further degradation of floodplains. Recently oil spills linked to the petroliferous activities in the region are of major concern demanding further and urgent evaluation.

Methane emissions from floodplains in the Amazon Basin: challenges in developing a process-based model for global applications

“…While such representative values will never be able to represent the high variability in flooding susceptibility of this diverse ecosystem (Junk and Piedade, 1993;Piedade et al, 2010), we chose a value for emergent C4 grasses with high productivity, dominating the herbaceous Amazon ecosystem, like Echinochloa polystachya and Paspalum repens. In our approach, we did not account for floating macrophytes (e.g., Paspalum fasciculatum) whose specificities (Wassmann et al 1992) would require a more fundamental recoding of LPX (see Discussion).…”

Carbon Dioxide Fluxes to the Atmosphere From Waters Within Flooded Forests in the Amazon Basin

“…If aerobic respiration and CO 2 production were in balance, the excess of CO 2 (Ex-CO 2 , i.e., CO 2 in the water subtracted from equilibrium CO 2 saturation) and the apparent oxygen utilization (AOU, i.e., atmospheric equilibrium O 2 solubility subtracted from the O 2 concentration measured in surface water) would follow a 1:1 line. Processes that could cause increased CO 2 production or elevated Ex-CO 2 include methanogenesis (Bartlett et al, 1988), groundwater CO 2 inputs, and root respiration within the flooded forest and associated herbaceous plants that use atmospheric CO 2 in photosynthesis and release respired CO 2 through their inundated roots (Abril et al, 2014;Abril & Borges, 2019;Piedade, Junk, et al, 2010). The first two processes were not likely to be important at our sites.…”

Morphometry and retention time as forcing functions to establishment and maintenance of aquatic macrophytes in a tropical reservoir

“…All aquatic macrophytes recorded in Ourinhos Reservoir are common in Neotropical reservoirs and lakes (Vilarrubia and Cova, 1993;Bini et al, 1999Bini et al, , 2005Neiff, 2001;Nahlik and Mitsch, 2006;Neiff et al, 2008;Martins et al, 2008;Bianchini Junior et al, 2010;Henry-Silva et al, 2010;Piedade et al, 2010;Rolon et al, 2010;Alves Ferreira et al, 2011). In the Paranapanema watershed, these species were also usually recorded in the following reservoirs: Rosana, Salto Grande, Chavantes, Piraju and Jurumirim (Henry and Nogueira, 1999;Casatti et al, 2003;Martins et al, 2008;Neves, 2008;Bianchini Junior and Cunha-Santino, 2014).…”

“…Neotropical aquatic ecosystems usually support several species of aquatic macrophytes (Neiff et al, 2008;Rolon et al, 2010;Piedade et al, 2010). The metabolic response of these organisms to abiotic factors combined with biological interactions (e.g., competition for light, herbivory, allelopathy) determine the basis of the community diversity and abundance (Lacoul and Freedman, 2006;Bornette and Puijalon, 2009).…”