Seven Years Study of the Seasonal Dynamics of Zooplankton Communities in a Large Subtropical Floodplain Ecosystem: A Test of the PEG Model

Irregular hydrological events, according to a classic plankton ecology group (PEG) study, can generate major deviations from the standard PEG model. However, little is known about the function of hydrological factors in influencing the seasonal dynamics of plankton. We used multivariate and Partial Least Squares Path Modeling to analyze the seasonal variation in crustacean zooplankton and related environmental factors from winter 2009 to winter 2016 in Lake Poyang, the largest freshwater lake in China. We found a distinct seasonal pattern in zooplankton development, which deviated, in part, from the PEG model, as we found indications of (1) a weaker degree of food limitation in winter and spring, likely due to high concentrations of allochthonous sources caused by decomposition of seasonally flooded hygrophytes, also affecting sediment dynamics; (2) a peak in crustacean zooplankton biomass in summer when the water level was high (and predation was lower), and where horizontal transport of zooplankton from the littoral zone to the pelagic was possibleand (3) a higher predation pressure in autumn, likely due to a shrinking water volume that left the fish concentrated in less water. The majority of these differences can be attributed to the direct or indirect impacts of physical factor variation.

Bulbostylis litoreamazonicola, a new species of Cyperaceae from the Brazilian Amazonian coast

A new species of Bulbostylis (Cyperaceae), only known from the Brazilian Amazonian coast, is here described and illustrated. Bulbostylis litoreamazonicola was found growing over dunes, in seasonally flooded restinga vegetation, and in humid fields near the mangroves from the State of Pará, Northern Brazil. This is the fifth Brazilian-native species of Bulbostylis lacking a persistent stylopodium on the mature fruit. The new species is mainly characterized by its annual habit, simple anthelate inflorescences, densely hispid to hispidulous longitudinally ribbed scapes, pubescent glumes, and cordiform nutlets.

The Floodplain Forests of the Mamberamo Basin, Papua, Indonesia (Western New Guinea): Vegetation, Soils, and Local Use

New Guinea is the world’s largest, most speciose, and most culturally rich tropical island, and the little-studied Mamberamo Basin of Papua (Indonesian New Guinea) is recognised among the region’s most-important areas for biological diversity. Here, we examined the floodplain forests in the indigenous territory of Papasena, within the Mamberamo-Foja Wildlife Reserve in the Mamberamo Basin. As part of a training activity with local researchers, students, and civil servants, and with the permission and assistance of the local people, we employed various methods including the field surveys detailed here. We used variable-area tree plots, transects for non-trees and soil sampling, and local informants to document 17 plots: four in old-growth dryland forest, five in old-growth swamp forests (two seasonally flooded and three permanently wet including one dominated by sago, Metroxylon sagu Rottb.), five in secondary forest (fallows), and three in gardens (two in swamps and one on dryland). In total, we measured 475 trees over 10 cm in diameter at 1.3 m (dbh). The swamp forests had high local basal areas (highest value 45.1 m2 ha−1) but relatively low statures (20 m but with emergent trees over 40 m). In total, 422 morphospecies from 247 genera and 89 different families were distinguished. These included 138 tree species and 284 non-tree plant species. A quarter (105) of the morphospecies lacked species-level identifications. The woody families Rubiaceae, Araceae, Moraceae, and Euphorbiaceae were especially diverse, with 20 or more morphospecies each. Tree richness was highest in dryland forest (plot 7 having 28 species in 40 stems over 10 cm dbh) with more variation in the flooded forests. Non-tree vegetation showed similar patterns ranging from 65 species in one 40-by-5 m primary forest plot to just 5 in one seasonally flooded forest plot. The local people identified many plants as useful. Among trees, at least 59 species were useful for construction (the most common use), while, for non-trees, medicinal uses were most frequent. Inceptisols dominated (12 plots), followed by Ultisols and Entisols (3 and 2 plots, respectively). Drainage appeared poor and nutrient availability low, while land-suitability criteria implied little potential for crops aside from sago. We discuss the implication of local practises and more recent developments that may threaten the conservation of these floodplain systems. We underline the key role of local people in the oversight and protection of these ecosystems.

Impacts of a large hydroelectric dam on the Madeira River (Brazil) on floodplain avifauna

ABSTRACT Hydroelectric dams represent an important threat to seasonally flooded environments in the Amazon basin. We aimed to evaluate how a dam in the Madeira River, one of the largest tributaries of the Amazonas River, affected floodplain avifauna. Bird occurrence was recorded through simultaneous passive acoustic monitoring in early successional vegetation and floodplain forest downstream from the dam and upstream in sites impacted by permanent flooding after dam reservoir filling. Species were identified through manual inspection and semi-automated classification of the recordings. To assess the similarity in vegetation between downstream and upstream sites, we used Landsat TM/ETM+ composite images from before (2009-2011) and after (2016-2018) reservoir filling. Downstream and upstream floodplain forest sites were similar before, but not after dam construction. Early successional vegetation sites were already different before dam construction. We recorded 195 bird species. While species richness did not differ between upstream and downstream sites, species composition differed significantly. Ten species were indicators of early successional vegetation upstream, and four downstream. Ten species were indicators of floodplain forest upstream, and 31 downstream. Seven of 24 floodplain specialist species were detected by the semi-automated classification only upstream. While we found some bird species characteristic of early successional vegetation in the upstream sites, we did not find most species characteristic of tall floodplain forest. Predominantly carnivorous, insectivorous, and nectarivorous species appear to have been replaced by generalist and widely distributed species.