Stable isotopes reveal niche segregation between native and non-native Hoplias in a Neotropical floodplain

We investigated whether isotopic niche partitioning could mediate the coexistence between native (Hoplias sp. B) and non-native (Hoplias mbigua) trahira in a Neotropical floodplain. We hypothesised that during the dry season both species inhabit isolated sites (i.e. lakes) and thus rely on distinct food resources to sustain their coexistence. We found evidence of trophic segregation among native and non-native freshwater fish in the Upper Paraná River, Brazil. Even though both species rely on the same primary littoral carbon sources and present similar trophic diversity, trophic segregation was attained through larger niche amplitude and smaller isotopic niche width for the non-native fish. Three decades after initial invasion, non-native Hoplias have distinct foraging behaviour and do not compete for trophic resources with native trahira; this is likely due to morpho-anatomical differences. Limited morphological similarity between these congeneric species might be the strongest factor contributing to their coexistence in the Paraná River floodplain during the dry season.     

Organic practices intensify the microbiome assembly and suppress root-knot nematodes

Journal of Pest Science - Roots can recruit beneficial microorganisms to suppress plant pathogens. However, conventional and organic practices differently shape the soil microbiome and consequently...     

Study of Interaction Between Glyphosate and Goethite Using Several Methodologies: an Environmental Perspective

Glyphosate (N-(phosphonomethyl) glycine) is one of the most widely used herbicides in the world. Experiments using distilled water or CaCl₂ extractor resulted in as much as 60% of glyphosate being desorbed from goethite. When Mehlich 1 extractor was used, desorption could reach up to 73%. At pHs 2.0, 4.0, 6.0, and 8.0, an increase in salt content decreased the adsorption of glyphosate onto goethite. This indicates that most of the glyphosate is bound weakly to goethite through an outer-sphere complex. Thus, in soils with a high goethite content, glyphosate will contaminate groundwaters or rivers easily. FT-IR spectra showed that glyphosate interacts with goethite through the phosphate group and, at high pH, the amine group could be involved. Evidences of the interaction of the amine group of glyphosate with goethite were also obtained from the EPR spectra that showed, at high pH, a distortion in the octahedral symmetry of iron. In addition to the adsorption decrease with an increase in pH, a decrease of desorption at high pH occurs. This probably occurs because, at high pH, glyphosate interacts with goethite as a monodentate complex and through the amine group. The adsorption results fit best to a Freundlich isotherm model. This is in good agreement with the desorption results, indicating the presence of at least two adsorption sites—one for outer-sphere complexes and the other of inner-sphere complexes. The experimental results fit well with both pseudo-second-order and diffusion-limited models. The experimental results also fit well with a diffusion-limited model; however, the C value was different from zero. Therefore, the adsorption process was not controlled by diffusion only. Adsorption of glyphosate onto goethite is a complex process that could involve intra-particle diffusion. After adsorption of glyphosate onto goethite, a large decrease of pH_pzc was observed. The surface area and pore volume of goethite did not change with the adsorption of glyphosate.     

Carbon, nitrogen, organic phosphorus, microbial biomass and N mineralization in soils under cacao agroforestry systems in Bahia, Brazil

Large amounts of plant litter deposited in cacao agroforestry systems play a key role in nutrient cycling. Organic matter, nitrogen and phosphorus cycling and microbial biomass were investigated in cacao agroforestry systems on Latosols and Cambisols in Bahia, Brazil. The objective of this study was to characterize the microbial C and N, mineralizable N and organic P in two soil orders under three types of cacao agroforestry systems and an adjacent natural forest in Bahia, Brazil and also to evaluate the relationship between P fractions, microbial biomass and mineralized N with other soil attributes. Overall, the average stocks of organic C, total N and total organic P across all systems for 0?C50?cm soil depth were 89,072, 8,838 and 790?kg?ha^?1, respectively. At this soil depth the average stock of labile organic P was 55.5?kg?ha^?1. For 0?C10?cm soil depth, there were large amounts of microbial biomass C (mean of 286?kg?ha^?1), microbial biomass N (mean of 168?kg?ha^?1) and mineralizable N (mean of 79?kg?ha^?1). Organic P (total and labile) was negatively related to organic C, reflecting that the dynamics of organic P in these cacao agroforestry systems are not directly associated with organic C dynamics in soils, in contrast to the dynamics of N. Furthermore, the amounts of soil microbial biomass, mineralizable N, and organic P could be relevant for cacao nutrition, considering the low amount of N and P exported in cacao seeds.