University of the Amazon

In Amazonia pastures are usually established after deforestation by sowing Urochloa grasses. Productivity declines due to nitrogen (N) limitation. Integrating N2-fixing legumes and grasses with Biological Nitrification Inhibition (BNI) capacity are considered as options for improving pasture sustainability. We studied grass-alone (GA) and grass–legume (GL) pastures on seven farms in Colombian Amazonia. Each treatment included grass with either low (Urochloa brizantha), intermediate (U. decumbens), or high (U. humidicola) BNI capacity. Biomass yields were measured over six harvests. Total N and δ15N of grasses and legumes and mineral N in topsoil (0–0.1 m) were analyzed in the first harvest. GL pastures with high BNI U. humidicola showed a biomass yield benefit of 1.6 t ha−1 over six harvests and 9.3 kg N ha−1 higher N yield for the first harvest compared to GA pastures. More than 70

The Andean–Amazon transition constitutes a pronounced environmental gradient that strongly influences the distribution of aquatic biodiversity; however, the compositional patterns of aquatic insects across this landscape remain sparsely characterized. We evaluated the patterns and drivers of the alpha diversity, taxonomic composition, and beta diversity of aquatic Coleoptera in 30 rivers, comprising 10 independent sampling sites per region (Andean, Transition, and Amazonian) in Caquetá, Colombia. We identified 54 genera, with Elmidae being the dominant family. Alpha diversity analysis using Hill numbers (q = 0, 1, 2) indicated that the Amazon region exhibited significantly higher diversity than the Andean and transition zones. Regarding assemblage structure, multivariate analyses (principal coordinate analysis [PCoA] and permutational multivariate analysis of variance [PERMANOVA]) and indicator value analysis (IndVal) revealed distinct assemblages defined by 15 diagnostic genera. Beta diversity partitioning demonstrated that dissimilarity along the gradient was predominantly driven by balanced variation in abundance, indicating that spatial patterns resulted from the substitution of individuals rather than differences in total abundance. Finally, constrained ordination (redundancy analysis [RDA] and distance-based redundancy analysis [dbRDA]) identified dissolved oxygen, organic substrates, and riparian cover as the primary environmental filters driving compositional differences and beta diversity patterns. Collectively, our findings suggest that the Andean–Amazon transition functions as a strong environmental filter, maintaining high regional diversity through the rapid turnover of specialized genera adapted to distinct local hydro-geomorphological conditions.

In this study, CuO, ZnO, and CuO/ZnO nanocomposites were synthesized via a sol-gel method and systematically investigated for photocatalytic and supercapacitor applications. XRD confirmed the formation of monoclinic CuO, hexagonal wurtzite ZnO, and a composite structure free of secondary phases, with average crystallite sizes of 26, 34, and 19 nm, respectively. FTIR and Raman analyses verified the presence of characteristic metal-oxide vibrations, while UV-DRS revealed band gaps of 2.30, 3.16, and 2.60 eV for CuO, ZnO, and CuO/ZnO. FESEM showed uniform dispersion of CuO over ZnO, and EDS confirmed elemental homogeneity. The CuO/ZnO nanocomposite achieved a Rhodamine-B degradation efficiency of 92.6 % within 180 min, following pseudofirst-order kinetics (k = 0.0168 min-1, t1/2 = 41.2 min), outperforming CuO (33.6 %) and ZnO (67.1 %). Electrochemical measurements demonstrated a specific capacitance of 98 F g-1 at 0.5 A g-1, with 84.1 % retention after 5000 cycles and low charge transfer resistance (17.6 Omega), confirming superior energy-storage capability. DFT calculations revealed bidentate adsorption of Rhodamine-B on the CuO/ZnO interface with optimal interaction energy (-8.67 eV), reduced band gap, and enhanced density of states near the Fermi level, explaining the observed experimental efficiency. Overall, the synergistic heterojunction interface in CuO/ZnO enhances charge separation, photocatalytic reactivity, and electrochemical performance, making it a promising multifunctional material for environmental and energy applications.

Cacao (Theobroma cacao) is a key tree species for chocolate production and a vital income source for millions, especially in Africa and South America. In the Amazon, physiological studies on cocoa have focused on abiotic factors, but the comparison of clones in these environments is still in its infancy.This study examined the physiological responses of cacao clones to the typical diurnal conditions of the Colombian Amazon. We measured environmental, plant health, and chlorophyll fluorescence variables in 18 cacao clones using MultispeQ and Imaging-PAM throughout the day; we estimated Fv/Fm, ΦII, ETR, and NPQt, calculated SLA, and quantified photosynthetic pigments. Significant phenotypic differences were identified in photosynthetic efficiency and morphology. High specific leaf area (SLA), linked to efficient energy capture and reduced transpiration, was observed in LUKER-40 and FGH-4. Chlorophyll a fluorescence approach, revealed differences in photochemical efficiency (Fv/Fm) and excess energy dissipation. Genotypes like FGH-4, FSV-41, and IMC-67 showed high Fv/Fm and electron transport rates (ETR) (p < 0.05) under heat stress, indicating strong PSII functionality. Conversely, ICS-95 relied on non-photochemical quenching (NPQt) for heat dissipation. LUKER-50, with high carotenoid content, demonstrated resilience to oxidative stress. Variations in chlorophyll content affected light capture efficiency, with ICS-60 excelling in photosynthesis under high temperatures and excess light at noon. Leaf temperature regulation emerged as critical, with genotypes like LUKER-40 maintaining cooler leaves to avoid potential thermal damage. These traits highlight the acclimation of genotypes to high light and heat in the Colombian Amazon, with LUKER-50, ICS-95, FLE-3, and LUKER-40 identified as promising candidates for agroforestry in this region.

The phenology of trees in tropical forests shapes the temporal distribution of resources such as fruits and leaves. In montane forests (> 1000 m altitude), tree diversity and primary productivity tend to decline with elevation, correlating with lower temperatures and resulting in low food availability for herbivorous and frugivorous consumers. In such environments, wild animals often rely on adaptive food choice strategies to cope when preferred resources are scarce, shifting to less preferred but more available items. This research examines the feeding strategy of red howler monkeys (Alouatta seniculus) inhabiting a montane forest in the Colombian Andes (2,500–3,000 m asl) by analyzing their food intake (grams of dry weight) and their response to resource availability and food species aggregation over an annual cycle. We recorded 1,277 h of continuous focal animal sampling of two howler groups and monitored 28 phenological plots within their home range. Fruit availability varied throughout the year, with asynchronous fruiting patterns observed both within and between species, while leaves remained available all year-round. Montane howlers maintained a predominantly folivorous diet; however, only the daily intake of young leaves and ripe fruits was significantly explained by their availability. Overall, total daily food intake increased with ripe fruit and flower availability but decreased with that of unripe fruits, even though did not explain ripe fruit consumption. In contrast, the aggregation of food species had no effect on daily food intake. Although availability varied among items, montane howler monkeys adjusted their consumption patterns to specific resources availability (e.g., increasing intake of ripe fruits and young leaves during periods of higher availability), within the context of their primarily folivorous feeding strategy.