Artículos científicos

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A methane sink in the Central American high elevation páramo: Topographic, soil moisture and vegetation effects
(Elsevier B.V., 2020-03-15) Chai, Leanne L.; Hernández Ramirez, Guillermo; Hik, David S; Barrio, Isabel C.; Frost, Carol M.; Chinchilla Soto, Isabel Cristina; Esquivel-Hernández, Germain
Methane (CH4) is a strong greenhouse gas with a global warming potential 23 times larger than that of carbon dioxide. Characterizing ecosystems as either sources or sinks for methane and their magnitudes informs on biosphere contributions to the global CH4 budget and to warming of the atmosphere. We quantified methane fluxes for the first time in a neotropical alpine páramo (Valle de Los Conejos, Chirripó Massif, Costa Rica) and examined the relationships of these fluxes with topography, soil moisture and vegetation, during the transition from dry to rainy season. Using closed chambers and laser spectroscopy, we measured soil CH4 and CO2 fluxes across a field site encompassing: a grassy plain as well as a plain, a gentle slope and a plateau dominated by a dwarf bamboo (Chusquea subtessellata Hitchcock). We found that the páramo landscape acts as a sink for CH4 [−53.1 ± 29.6 (mean ± SE) µg C m−2 hr−1]. Of the four field areas, the grassy plain was on average the strongest CH4 sink, likely because this soil profile had no drainage restrictions and was well aerated. By contrast, in the slope and plateau, a heavily-consolidated subsurface layer was shown to perch water, increasing surface soil moisture and limiting CH4 uptake. Conversely, in certain parts of the plain, where Chusquea grew vigorously in discrete, tall patches, we found intense CH4 uptake beneath these patches. Within the Chusquea plain, these hot spots of CH4 uptake localized under the tall Chusquea had double the uptake rates than outside these patches, with even greater uptake than the average in the grassy plain. Our results show that CH4 uptake in the páramo is driven by moisture interacting with impeding soil layers, vegetation and topography.
A preliminary isotope-based evapotranspiration partitioningapproach for tropical Costa Rica
(John Wiley and Sons Ltd, 2021-07) Iraheta, Alberto; Birkel, Christian; Benegas, Laura; Ríos, Ney; Sánchez-Murillo, Ricardo; Beyer, Matthias
Spatially and seasonally distributed information on transpiration (T) fluxes is limited in the tropics. Here, we applied a coupled isotope mass balance model to separate water fluxes of T and evapotranspiration (ET) from precipitation (P). The mean annual T was estimated at a resolution of 100 m for Costa Rica (51,100 km2) and a partitioning of monthly T and evaporation (E) for the 2370-km2 San Carlos catchment. The dominant flux in the forest ecosystems was T with a mean annual T of 1086 mm that ranged from 700 mm in Tropical Montane Very Humid Forest to 1400 mm in Subtropical and Tropical Low Montane Rainforests. We estimated an average 85% of ET was T, which is concurrent with expectations for forested tropical regions, but varied according to model parameterization and data sources. A model comparison exercise showed a range of mean annual T estimates from 988 to 1465 mm and a range of T/P from 0.35 to 0.5 with temperature and relative humidity exhibiting the highest impact on the model results. Across Costa Rica, we estimated an average loss of precipitation by T of 38% (1085 mm), whereas interception (I) constitutes 10% (230 mm) and direct evaporation (E) only 7% (192 mm). Similarly, the results at the catchment scale indicated that monthly T contributes 76% (85-mm monthly average) to total ET and E corresponds to 24% (24-mm monthly average). The T rates exhibited an opposite seasonality to rainfall with highest T over the drier months from December to April with a peak in March (101–144 mm) and the minimum T in September (53–71 mm). Around 17% (79–130 mm) of precipitation over the catchment area is lost to T, both E (10–35 mm) and I (15–38 mm) correspond to 5%. Despite the inherent uncertainties of the data assumptions and simplifications, including data interpolation errors, the coupled isotope mass balance model showed in comparison to other global products reasonable water partitioning for different ecosystems in Costa Rica and the San Carlos catchment area. These results can help to evaluate the impact of land cover conversion on the hydrological cycle in Costa Rica, and the simple isotope-based model could be transferred to different biomes of the tropics.
Addition of nanosilicas with different silanol content to thermoplastic polyurethane adhesives
(Elsevier, 2005-08-15) Jose-Roberto, Vega-Baudrit; Navarro Bañón, Virtudes; Vásquez, Patricia; Martín Martínez, José Miguel
Three nanosilicas with different silanol contents were prepared by treatment of hydrophilic fumed silica with dimethyldichlorosilane. This treatment reduced the silanol content and produced the particle agglomeration of the nanosilicas. Thermoplastic polyurethane (TPU) adhesives containing nanosilicas were prepared and characterized by FTIR spectroscopy, differential scanning calorimetry (DSC), plate-plate rheology, dynamic mechanical thermal analysis (DMTA), transmission electron microscopy (TEM) and stress-strain testing. Adhesive strength was obtained from T-peel tests of PVC/polyurethane adhesive joints. The addition of hydrophilic nanosilicas favoured the degree of phase separation between the hard (i.e. isocyanate+chain extender) and soft (i.e. polyol) segments in the TPUs; the higher the silanol content on the surface of silica, the higher the degree of phase separation, and the crystallinity of the polyurethane (due to the soft segments) was also increased. Hydrogen bonds between the ester carbonyl groups in the TPU and the silanol groups on the silica surface were created and more favoured by increasing the silanol content. The tensile strength increased and the elongation at break of the polyurethane decreased by increasing the silanol content of the nanosilica. Addition of nanosilica increased the immediate adhesion of the polyurethane adhesives to PVC, irrespective of the silanol content on the nanosilica. The higher the mechanical and the rheological properties of the polyurethanes containing nanosilicas with different silanol content, the higher the final adhesive strength. © 2005 Elsevier Ltd. All rights reserved.
An approach to rheological and electrokinetic behaviour of lipidic vesicles covered with chitosan biopolymer
(Elsevier, 2008) Madrigal-Carballo, Sergio; Seyler, D.; Manconi, M.; Mura, S.; Vila, A.; Molina, F.
The rheological and electrokinetic properties of soybean lecithin vesicles prepared from concentrated soy lecithin dispersions (250 g/L) obtained by slow swelling under shear conditions and mixed with chitosan biopolymer solutions were studied. The rheological behaviour of lecithin-chitosan vesicles was determined by shear stress against shear rate measurements, as well as by the variation on the hysteresis loop area. The results were compared with the rheopectic behaviour of soy lecithin dispersions without chitosan. An important change on the rheological properties of the complex dispersion was observed, depicting in a thixotropic behaviour with a plastic character in the presence of chitosan. This observation indicates that chitosan promotes the transition of planar sheets into closed structures, such as vesicles. The influence on the rheological and the electrokinetic behaviours of several electrolytes, such as NaCl, CaCl2 and AlCl3 with concentrations ranging between 10-5 and 10-2 mol/L were also studied. In all of the cases, an estimation of the diameters of the closed structures was obtained. © 2007 Elsevier B.V. All rights reserved.
Analysis of energy transfer and ternary non-covalent filler/matrix/UV stabilizer interactions in carbon nanofiber and oxidized carbon nanofiber filled poly(methyl methacrylate) composites
(Elsevier, 2011-10-27) Gunes, I. Sedat; Pérez Bolívar, César; Jiménez, Guillermo A.; Çelikbıçak, Ömür; Li, Fengyu; Anzenbacher, Jr., Pavel; Wesdemiotis, Chrys; Jana, Sadhan
Ternary non-covalent interactions between carbon nanofibers (CNFs), oxidized carbon nanofibers (ox- CNFs), poly(methyl methacrylate) (PMMA) chains, and benzotriazole-containing UV stabilizers were analyzed using Fourier-transform infra red spectroscopy (FTIR), time-resolved fluorescence emission spectroscopy, and fluorescence lifetime imaging microscopy. The results indicated that PMMA chains form hydrogen bonds both with ox-CNF fibers and the UV stabilizer molecules. It was also determined that UV stabilizers strongly interact with CNF particles via p-p interactions. The extent of p-p and hydrogen bonding interactions was determined to be lower between ox-CNF particles and UV stabilizers due to less perfect graphitic structure of the former. The morphology of the composites indicated that the hydrogen bonds between PMMA chains and ox-CNF particles resulted in highly improved state of filler dispersion in ox-CNF/PMMA composites.
Analysis of non-covalent interactions between the nanoparticulate fillers and the matrix polymer as applied to shape memory performance
(The Royal Society of Chemistry, 2010) Sedat Gunes, I; Perez Bolivar, Cesar; Cao, Feina; Jimenez, Guillermo A.; Anzenbacher, Pavel; Sadhan, Jana
Non-covalent interactions between filler particles and polyurethanes were investigated using fluorescence emission spectroscopy. The results were used in the analysis of shape memory (SM) performance of polyurethanes. Composites of shape memory polyurethane (SMPU) and carbon nanofiber (CNF), oxidized carbon nanofiber (ox-CNF), organoclay, silicon carbide, and carbon black were prepared from diphenylmethane diisocyanate, 1,4-butanediol, and poly(caprolactone)diol. It was revealed by fluorescence emission spectroscopy that primarily the urethane groups located in the hard segments of SMPU interacted with the polar functional groups on filler particles. A close correlation between the extent of non-covalent filler-matrix interactions, soft segment crystallinity, and SM properties of polyurethane composites was discussed. It was observed that weak non-covalent interactions of polymer chains with CNF and SiC particles caused significant reductions in soft segment crystallinity of SMPU and hence the shape memory properties of the composites. © The Royal Society of Chemistry 2010.
Announcing the call for the Issue Focus on the 2nd Costa Rican Biophysics Symposium—virtual meeting, March 2021
(Springer (Alemania), 2021) Solis-Ocampo, Chrisopher; Chaves Barboza, Gustavo; Rodríguez-Corrales, José
This Commentary is a call for submissions for the upcoming Issue Focus that will highlight some of the scientific topics discussed during the 2nd Costa Rica Biophysics Symposium.
Anthrone and oxanthrone C,O-diglycosides from Picramnia teapensis
(Elsevier, 2000) Rodríguez Gamboa, Tatiana; Victor, Sandra R.; Fernandes, Joao B.; Rodrigues Fo, Edson; Da Silva, M. Fatima das G.F.; Vieira, Paulo C.; Pagnocca, Fernado C.; Hebling, Maria Jose A.; Castro C., Oscar
Two C,O-diglycosylated compounds, the anthrone picramnioside F, and the oxanthrone mayoside C, were isolated from the stem bark of Picramnia teapensis, along with the previously reported anthraquinones, 1-O-b-d- and 8-O-b-d-glucopyranosyl emodin. The compounds were separated by recycling-HPLC, and their structures were determined on the basis of spectroscopic analysis. CD measurements were used to establish the absolute con®guration of the anthrone and oxanthrone. The antifungal activity of 1- O-b-d- and 8-O-b-d-glucopyranosyl emodin against Leucoagaricus gongilophorus was shown to be similar to that of the lignan sesamin. # 2000 Elsevier Science Ltd. All rights reserved.
Antimicrobial activities of Marcgraviaceae species and isolation of a naphthoquinone from Marcgravia nervosa (Marcgraviaceae)
(NRC Research Press, 2015) Carballo Arce, Ana Francis; Chieu Anh, Kim Ta; do Nascimento Rocha, Marco Eduardo; Rui, Liu; Harmsen, Irene; Mogg, Christopher; Otárola-Rojas, Marco; Garcia, Mario; Sánchez Vindas, Pablo; Poveda, Luis; Rajagopal Subramaniam; Smith, Myron; Coelho Kaplan, Maria Auxiliadora; Figueiredo, Maria Raquel; Durst, Tony; Arnason, John
The Marcgraviaceae is a neotropical plant family of lianas and shrubs distributed throughout Central and South America, mainly in evergreen and semi-evergreen tropical forests. In this study, extracts of 12 Marcgraviaceae species were assessed for inhibition of bacterial quorum sensing (QS) in Chromobacterium violaceum, bacterial biofilm formation in Pseudomonas aeruginosa PA14, and fungal growth in Saccharomyces cerevisiae. Six species showed promising inhibitory activities in at least one of the three bioassays (Marcgravia nervosa Triana & Planch., Marcgravia polyantha Delp., Marcgravia schippii Standl., Marcgraviastrum subsessile (Benth.) Bedell, Schwartzia brasiliensis (Choisy) Bedell ex Gir-Cañas, and Schwartzia costaricensis (Gilg.) Bedell). Analyses of the crude extract of the leaves of Marcgravia nervosa using HPLC–APCI–MS showed the presence of five pentacyclic triterpenes: ursolic acid (2), betulinic acid (3), α–amyrin (4), β–amyrin (5), lupeol (6). Bioassay-guided fractionation of this plant resulted in the isolation and identification of 2-methoxy-1,4-naphthoquinone (1) as the active principle with a minimum inhibitory concentration (MIC) of 85–100 μmol·L−1 against Saccharomyces cerevisiae BY4741 (haploid) and BY4743 (diploid).
Arsenate removal by chitosan iron oxyhydroxide beads: Preparation, characterization, and adsorption studies
(Desalination Publications, 2021) González Rodríguez, José Ricardo; Rojas Carrillo, Oscar; Romero-Esquivel, Luis G.
This study compared arsenic removal from drinking water by two different adsorbents: iron-im-pregnated chitosan beads (Fe-ICB) and iron-doped chitosan beads (Fe-dCB). Scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared, and Raman spectroscopy were applied to characterize the materials produced. The As(V) adsorption capacity of both types of materials was evaluated by batch tests, followed by a column test using the most promising material. The XRD and the Raman spectroscopy confirmed the presence of 2-line ferrihydrite in the produced Fe-dCB, and no specific iron oxy-hydroxide was identified in the Fe-ICB. Both types of materials followed either the Langmuir or the Freundlich isotherm adsorption models. The Fe-dCB were more efficient in removing As(V) than the Fe-ICB. The actual maximum capacity of the produced Fe-dCB ranged from 0.27 to 0.61 mg/g under the conditions tested (concentration: 1 mg/L; pH: 7.0; 100 rpm). The Fe-dCB with the better adsorption capacity at low concentrations (<0.1 mg/L) were used in a column test using an As(V) influent concentration of 0.060 mg/L. The Fe-dCB produced close to 91,000 BVs, meeting the standard for drinking water (0.01 mg/L). Therefore, the material exhibits promising adsorbent properties for filtration applications with low arsenic concentrations.
Arthropod biodiversity loss and the transformation of a tropical agro-ecosystem
(Chapman & Hall, 1997) Perfecto, Ivette; Vandermeer, John; Hanson, Paul; Cartin, Víctor
The coffee (coffea arabica) agro-ecosystem in the Central Valley of Costa Rica was formerly characterized by a high vegetational diversity. This complex system has been undergoing a major transformation to capital-intensive monocultural plantations where all shade trees are eliminated. In this study we examined the pattern of arthropod biodiversity loss associated with this transformation. Canopy arthropods were sampled in three coffee farms: a traditional plantation with many species of shade trees, a moderately shaded plantation with only Erythrina poeppigeana and coffee, and a coffee monoculture. An insecticidal fogging technique was used to sample both canopy and coffee arthropods. Data are presented on three major taxonomic groups: Coleoptera, non-formicid Hymenoptera, and Formicidae. Data demonstrate that the transformation of the coffee agro-ecosystem results in a significant loss of biological diversity of both canopy arthropods as well as arthropods living in coffee bushes. Percentage of species overlap was very small for all comparisons. Furthermore, species' richness on a per tree basis was found to be within the same order of magnitude as that reported for trees in tropical forests. If results presented here are generalizable, this means that conservation efforts to preserve biological diversity should also include traditional agro-ecosystems as conservation units.
Biofabrication of Gold Nanotriangles Using Liposomes as a Dual Functional Reductant and Stabilizer
(American Chemical Society, 2021-03-23) Soto, Jackeline; Conejo-Valverde, Paolo; Sáenz-Arce, Giovanni; Dou, Hongjing; Rojas Carrillo, Oscar
Negatively charged liposomes accomplished both functions as a reducing and stabilizing agent in the synthesis of gold nanotriangles (GNTs). Liposomes are based on a mixture of phospholipids phosphatidylcholine/phosphoglycerol, and they were used as a template phase to perform the GNTs. The method was evaluated under different conditions such as temperature, reaction time, phosphoglycerol chain length, and precursor concentration. Isotropic and anisotropic gold nanoparticles are formed simultaneously during the synthesis. Therefore, by combining centrifugation and depletion flocculation strategies, the sample was concentrated in terms of GNTs from 15% crude to 80% by using sodium dodecyl sulfate (SDS). As a result, a green colored dispersion was obtained containing highly purified, well-defined, negatively charged GNTs, where the edge length of most particles is centered in the range of 60-80 nm with an average thickness of 7.8 ± 0.1 nm. By this purification process, it was possible to highly increase the yield in terms of GNTs. Other surfactants [cetyltrimethylammonium chloride (CTAC), hexadecyltrimethylammonium bromide (CTAB), Tween 20, and dodecyldimethylammonium bromide] were evaluated during the purification stage, and both CTAB and CTAC show similar results to those obtained by using SDS. These GNTs are potential candidates for future applications in molecular imaging, photothermal therapy, drug delivery, biosensing, and photodynamic therapy.
Biogardens as constructed wetlands in tropical climate: A case study in the Central Pacific Coast of Costa Rica
(Elsevier, 2019-03-25) Pérez-Salazar, Roy; Mora Aparicio, Carmen; Alfaro-Chinchilla, Carolina; Sasa Marín, Jihad; Scholz, Carola; Rodríguez-Corrales, José
In Costa Rica, <10% of wastewater is treated before its discharge. This generates a significant impact on the environment, public health, and tourism industry, which is one of the country's main economic activities. Biogardens, subsurface flow artificial wetlands, are alternative systems for the treatment of wastewater. The present study evaluated the removal of organic matter and nutrients in a biogarden located at a hotel in the Central Pacific Coast of Costa Rica between 2012 and 2017. Pretreatment involved septic tanks and grease traps for sewage and gray water, respectively. The biogarden, which is composed of seven wetlands with an average area of 12 m2 and a depth of 0.7 m, contains river cobble as support material, gravel as bed, and Cyperus papyrus and Heliconia sp. plants. Removal of the biochemical oxygen demand (BOD), the chemical oxygen demand (COD), and the total suspended solids (TSS) on average were 80%, 66%, and 72%, respectively, thus producing an effluent in compliance with current national legislation. Furthermore, the biogarden did not emit noxious odors or display an excessive presence of mosquitoes. The results showed consistent and efficient removal of organic matter and nutrients from the wastewater throughout different seasons and pollutant loads, verifying that such systems can be used in decentralized locations (e.g., tourist areas) in tropical climates.
Characterization and applications of silver nanoparticles-decorated electrospun nanofibers loaded with polyphenolic extract from rambutan (Nepelium lappaceum)
(Elsevier B.V., 2020-05) Urena-Saborio, Hilary; Rodríguez, Gerardo; Madrigal-Carballo, Sergio; Gunasekaran, Sundaram
Rambutan (Nephelium lappaceum) is a traditional fruit originally from Asia and now widely available in Central America. The rind of rambutan is rich in antioxidants, especially polyphenols, which have natural anti-inflammatory and antimicrobial properties. Rambutan polyphenolic extract (RPE) was encapsulated in multi-component electrospun nanofiber (ESNF) templates. These nanofibers were decorated with silver nanoparticles (AgNPs) via in situ electrochemical reduction. The RPE-loaded and AgNPs-decorated ESNF (AgNPs/RPE-ESNF) were evaluated for their hydrophilic, antioxidant, and antimicrobial properties. Results indicate that the addition of RPE to synthetic polycaprolactone (PCL) ESNF improves hydrophilicity and cell attachment and proliferation in vitro. In addition, a synergistic antibacterial and cell proliferation effect between AgNPs and RPE was observed when they were combined in the multi-functionalized ESNF system. The effectiveness of AgNPs/RPE-PCL ESNF as an antioxidant and antibacterial matrix could potentially promote wound healing and also serve as a hybrid scaffold for tissue engineering.
Chemical constituents from Zanthoxylum setulosum (Rutaceae)
(Universidad Nacional, Costa Rica, 2011-02-10) Castro, Víctor; Poveda, Luis; Chavarria, Max; Mora Vasquez, Soledad; Murillo, Renato
Following our phytochemical studies of Costa Rican plants, in this work we report the isolation and identification of eight compounds from aerial parts of Zanthoxylum setulosum (Rutaceae). They were identified as the alkaloid skimmianine, the lignans savinin, kusunokinin, sesamin, syringaresinol and the isopentenyl ether of pluviatol, the amide aurantiamide acetate, and the triterpen lupeol. This is the first report of isolation of skimmianine from the leaves of Z. setulosum and its presence confirm that quinoline and benzophenanthridine alkaloids, can be considered as chemotaxonomic markers of this genus. All the isolated compounds were characterized by spectroscopic methods (including 1H-NMR, 13C-NMR, HMQC, HMBC and NOESY) and comparison with the literature data. © 2011 Boletín Latinoamericano y del Caribe de Plantas Medicinales y Aromáticas.
Composite soy lecithin–decylpolyglucoside vesicles: A theoretical and experimental study
(Elsevier, 2008) Mura, S.; Manconi, M.; Madrigal Carballo, S.; Sinico, C; Fadda, A.M; Vila, A.O; Molina, F
In the present work, vesicles made with soy lecithin and a commercial mixture of alkyl polyglucosides were prepared and characterized. Vesicles with a constant amount of soy lecithin and an increasing amount of a decylpolyglucoside surfactant, (OrNS10), were formulated and their physicochemical properties were studied with the aim to design a drug delivery system suitable for different applications. To this purpose, morphology, size distribution, ζ-potential and apparent viscosity of the prepared vesicles were studied. Vesicles were also characterized by using optical and light polarized microscopy, transmission electron microscopy and photon correlation spectroscopy. A stability study was also performed by checking mean size and ζ-potential value variation of the several formulations during 4 weeks. Moreover, theoretical advances on geometric and thermodynamic aspects related to lipid vesicle formation were applied to this study. © 2007 Elsevier B.V. All rights reserved.
Composites of carbon nanofibers and thermoplastic polyurethanes with shape-memory properties prepared by chaotic mixing
(Wiley Inter Science, 2009) Jimenez, Guillermo A.; Jana, Sadhan C.
Composites of carbon nanofibers (CNFs), oxidized car bon nanofibers (ox-CNFs), and shape-memory thermo plastic polyurethane (TPU) were prepared in a chaotic mixer and their shape-memory properties evaluated. The polymer was synthesized from 4,40 -diphenylme thane diisocyanate, 1,4-butanediol chain extender, and semicrystalline poly(e-caprolactone) diol soft segments. The shape-memory action was triggered by both con ductive and resistive heating. It was found that soft segment crystallinity and mechanical reinforcement by nanofibers produced competing effects on shape memory properties. A large reduction in soft segment crystallinity in the presence of CNF and stronger me chanical reinforcement by well-dispersed ox-CNF determined the shape-memory properties of the re spective composites. It was found that the maximum shape recovery force, respectively, 3 and 4 MPa, was obtained in the cases of 5 and 1 wt% CNF and ox-CNF, respectively, compared with 1.8 MPa for unfilled TPU. The degree of soft segment and hard segment phase separation and thermal stability of the composites were analyzed. POLYM. ENG. SCI., 49:2020–2030, 2009. ª 2009 Society of Plastics Engineers
Distinguishing the Regional Atmospheric Controls on Precipitation Isotopic Variability in the Central-Southeast Portion of Brazil
(Springer (Alemania), 2022-10) Santos, Vinícius dos; Marshall Fleming, Peter ; Henrique Mancini, Luís; Dalva Santos Cota, Stela; Lima, Graziele Beatriz de; Rodrigues Gomes, Rafaela; Kirchheim, Roberto Eduardo; Sanchez-Murillo, Ricardo; Gastmans, Didier
Precipitation isotope ratios (O and H) record the history of water phase transitions and fractionation processes during moisture transport and rainfall formation. Here, we evaluated the isotopic composition of precipitation over the central-southeastern region of Brazil at different timescales. Monthly isotopic compositions were associated with classical effects (rainfall amount, seasonality, and continentality), demonstrating the importance of vapor recirculation processes and different regional atmospheric systems (South American Convergence Zone-SACZ and Cold Fronts-CF). While moisture recycling and regional atmospheric processes may also be observed on a daily timescale, classical effects such as the amount effect were not strongly correlated (δ18O-precipitation rate r ≼ −0.37). Daily variability revealed specific climatic features, such as δ18O depleted values (∼6‰ to −8‰) during the wet season were associated with strong convective activity and large moisture availability. Daily isotopic analysis revealed the role of different moisture sources and transport effects. Isotope ratios combined with d-excess explain how atmospheric recirculation processes interact with convective activity during rainfall formation processes. Our findings provide a new understanding of rainfall sampling timescales and highlight the importance of water isotopes to decipher key hydrometeorological processes in a complex spatial and temporal context in central-southeastern Brazil.
Dry season plant water sourcing in contrasting tropical ecosystems of Costa Rica
(John Wiley & Sons (Estados Unidos), 2023) Sánchez-Murillo, Ricardo; Todini-Zicavo, Diego; Poca, María; Birkel, Christian; Esquivel-Hernández, Germain; Chavarría, María Marta; Zuecco, Giulia; Penna, Daniele
Tracer-aided studies to understand plant water uptake sources and dynamics in tropical ecosystems are limited. Here, we report the analysis of dry season source water uptake patterns of five unique ecosystems of Costa Rica across altitudinal (<150– 3,400 m asl) and latitudinal (Caribbean and Pacific slopes) gradients: evergreen and seasonal rainforests, cloud forest, Páramo and dry forest. Soil and plant samples were collected during the dry season in 2021. Plant and soil water extractions were conducted using centrifugation. Stem water extracted volume and stem total water content were calculated via gravimetric analysis. Water source contributions were estimated using a Bayesian mixing model. Isotope ratios in soil and stems exhibited a strong meteoric origin. Enrichment trends were only detected in stems and cactus samples within the dry forest ecosystem. Soil profiles revealed nearly uniform isotopic profiles; however, a depletion trend was observed in the Páramo ecosystem below 25 cm. More enriched compositions were reported in cactus samples for extracted water volumes above 20% (adj. r2 = 0.34, p < 0.01). The most prominent dry season water source in the evergreen rainforest (74.0%), seasonal rainforest (86.4%) and cloud forest (66.0%) corresponded to well-mixed soil water. In the Páramo ecosystem, recent rainfall produced by trade wind incursions resulted in the most significant water source (61.9%), whereas in the dry forest, mean annual precipitation (38.6%) and baseflow (33.1%) were the dominant sources. The latter highlights the prevalence of distinct water uptake sources between recent cold front rainfall (near-surface soil storage) to more well-mixed soil moisture during the dry season, revealing ecohydrological processing previously unknown in this tropical region.
Editorial for ‘Issue focus on 2nd Costa Rica Biophysics Symposium - March 11th–12th, 2021’
(Springer (Alemania), 2022) Chaves, Gustavo; Rodríguez-Corrales, José; Solis-Ocampo, Chrisopher
This Editorial describes both the motivation for, and the five articles appearing in, the Issue Focus dedicated to the 2nd Costa Rica Biophysics Symposium which was held in March 2021. Some recent history about both the symposium and developments in science occurring within Costa Rica is described.

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