Forested Basins Research Articles

Zircon U–Pb CA–ID–TIMS constraints on the chronology of the Late Carboniferous–early Permian continental Döhlen Basin and its correlation with the Thuringian Forest Basin (Central and Eastern Germany)

We present new zircon U–Pb chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA–ID–TIMS) ages of two Late Carboniferous–early Permian continental basins in Germany. Three volcanic rocks from the Döhlen Basin (Saxony), and two tuff samples of the Thuringian Forest Basin (Thuringia) were dated. Our data indicate that all four formations of the Döhlen Basin were deposited in the interval of approx. 300 Ma to 298 Ma. The tuff samples of the Thuringian Forest Basin provided ages that overlap with the Döhlen Basin data. The Niederhäslich Formation of the Döhlen Basin and the Manebach and Goldlauter formations of the Thuringian Forest Basin contain fossil-rich lacustrine horizons, which have been correlated to a variety of formations in other European basins through the use of insect, amphibian, or conchostracan assemblage zones. Our new data thus provide new absolute age constraints for different fossil assemblage zones. Furthermore, the data can be considered a strong indication for simultaneous large-scale volcanic activity between 300 and 298 Ma. A relation between volcanic and post-Variscan transtensional tectonic activity is proposed because both the Döhlen Basin and the Thuringian Forest Basin are bound to NW trending strike-slip faults.Graphical abstract

Mechanisms of spring freshet generation in southern Quebec, Canada

Seasonal forecasting of spring floods in snow-covered basins is challenging due to the ambiguity in the driving processes, uncertain estimations of antecedent catchment conditions, and the choice of predictor variables. In this study, we attempt to improve the prediction of spring flow peaks in southern Quebec, Canada, by studying the preconditioning mechanisms of runoff generation and their impact on inter-annual variations in the timing and magnitude of spring peak flow. Historical observations and simulated data from a hydrological and snowmelt model were used to study the antecedent conditions that control flood characteristics in 12 unregulated snow-dominated catchments. Maximum snow accumulation (peak SWE), snowmelt and rainfall volume and intensity, soil moisture, river baseflow, and the air freezing index, a proxy for soil freezing, were estimated during the pre-flood period. Stepwise multiple linear regression was used to identify the most relevant predictors and assess their relative contribution to interannual variability flood variability. Peak SWE was not by itself a strong predictor of spring flood magnitude and timing. The snowmelt rate during the pre-flood period was the most ubiquitous and skillful predictor of spring flood magnitude, followed by the rainfall intensity. The ‘soil memory’ effect, represented here by the simulated soil moisture content and freezing depth, was generally poorly related to flood characteristics. SWE and snowmelt dynamics dominated the interannual variability of flood magnitude in the southern and agricultural basins while rainfall intensity had a stronger influence in the northern, snowier forested basins. More complex machine learning models (random forest and support vector regression) did not perform better than the simple linear models to predict peakflow from antecedent hydroclimatic factors. These results highlight the impact of climate and land cover and use on spring flood generation mechanism and the moderate predictability potential of spring floods based on antecedent hydrological factors.

Estimating groundwater resources in an equatorial forested basin using geographic information system and remote sensing techniques (case of Nyong, South Cameroon)

ABSTRACT This article aims to produce a groundwater potential zone (GWPZ) map of the Nyong basin using an integrated analytical hierarchy process driven in a geographic information system (GIS) environment. For this, seven parameters (rainfall, geology, slopes, drainage density, land use and land cover, lineament density, and soil) known to influence the availability of groundwater were considered. The results obtained show that the Eastern part of the basin holds the largest quantities of groundwater. The produced map shows that this region includes high and very high GWPZs (yield > 6 l/s). It is essentially characterized by abundant rainfall (on average 135–136 and 131–134 mm), low slopes, significant drainage and lineament densities, and significant forest cover. On the other hand, the opposite region (west), which includes the low and very low GWPZs, is characterized by less abundant precipitation (on average 121–125 and 125–128 mm), significant slopes, lower drainage and lineament densities, and greater impervious areas. With a success rate of 80%, confidence deserves to be placed in the GWPZs map produced. It can be considered in water supply projects in this basin. Such work has never been done in this basin before.

Space-time cube uncovers spatiotemporal patterns of basin ecological quality and their relationship with water eutrophication

Maintaining an optimal eco-environment is important for sustainable regional development. However, existing methods are inadequate for examining both spatial and temporal dimensions. Here, we propose a systematic procedure for spatiotemporal examination of the eco-environment using the space-time cube (STC) model and describe a preliminary investigation of the coupling relationships between basin ecological quality and water eutrophication in upstream of the Han River basin between 2000 and 2020. The STC model considers the temporal dimension as the third dimension in calculations. We first categorized the basin into three sub-watershed types: forest, cultivated land, and artificial surface. Subsequently, the ecological quality and driving factors were assessed and identified using the remote sensing ecological index (RSEI) and Geodetector method, respectively. The findings indicated that the forest basin and artificial surface basin had the highest and lowest ecological quality, respectively. The spatiotemporal cold spots of ecological quality during the past 20 years were mostly located in the vicinity of reservoirs, rivers, and artificial surface areas. Human activity, precipitation, and the percentage of cultivated land were other important driving factors in the artificial surface, forest, and cultivated land sub-watersheds, respectively, in addition to the dominant factors of elevation and temperature. The results also indicated that when the ecological quality degraded to a certain extent, water eutrophication was significantly coupled with the ecological quality of the catchments. The findings of this study are useful for ecological restoration and sustainable river basin development.

Current progress in quantifying and monitoring instream large wood supply and transfer in rivers

AbstractLarge wood drives both the form and function of gravel‐bed rivers draining forested basins. Previously overlooked benefits of wood in rivers are now widely recognized. Together with flow and sediment regimes, the wood regime controls rivers' physical and ecological integrity. Yet large quantities of wood transported during floods can pose additional hazards, potentially damaging infrastructures like bridges or dams and exacerbating flooding. However, unlike the water and sediment regimes intensively studied over the past decades, the instream wood regime or budgeting has been only recently defined and thus is still rarely quantified. The instream wood budget describes the cascading processes from supply or recruitment, entrainment, and transport to deposition, storage and decay (i.e., fragmentation or decomposition). These processes show high spatial and temporal variability but can be characterized by magnitude, frequency, timing, duration and mode. Instream wood budgeting is challenging, primarily because of the lack of observations, monitoring stations, and standardized protocols to acquire data. This contribution reviews the most recent advances to quantify the different instream wood budget components, notably the wood supply, and transfer. Case studies showing applications of biogeochemistry, videography, artificial intelligence, numerical modelling or tracking illustrate the current progress. Because critical challenges remain, we identify and describe some of them and discuss how the wood in riverine sciences may develop in the future.

Seasonal analysis of land surface temperature using local climate zones in peak forest basin topography: A case study of Guilin

Understanding the characteristics of Land Surface Temperature (LST) is crucial to mitigate the Surface Urban Heat Island (SUHI) effect. Local Climate Zones (LCZs) framework can be applied in LST analysis and SUHI quantification. However, this framework primarily focuses on evaluating detailed local-scale SUHI, thereby failing to provide a comprehensive assessment of the overarching SUHI trends at the urban level. Additionally, existing LST analyses ignored geographic factors, resulting in partial analysis of LST, especially in areas with complex geography. To fill these gaps, the study develops a SUHI assessment method combining an improved surface urban heat intensity ratio index with LCZs-based SUHII, enabling a dual evaluation of both overall and detailed SUHI effect. The impact of geographic factors, both topography and natural features, on seasonal LST patterns is investigated, especially within built LCZs. Additionally, the spatio-temporal image fusion model is employed to address issues of cloud effects or image mutilations in LST results. Guilin, with unique peak forest basin topography, is selected as a case study to represent complex geographical areas. The results reveal the following: (1) An abnormal heat island phenomenon occurs during winter due to Guilin's distinctive geomorphological conditions. (2) Cooling effects influenced by mountains and water bodies on different built LCZs exhibit seasonal variation, with the strongest cooling effect observed within a 50-m distance. LCZ 2 consistently exhibits the strongest cooling effect. The study offers valuable insights for guiding decisions in sustainable urban planning and design, especially in cities influenced by complex local geography.

A new eryopid temnospondyl from the Carboniferous–Permian boundary of Germany

AbstractA new eryopid temnospondyl, Stenokranio boldi n. gen. n. sp. is described based on well-preserved cranial and postcranial material from fluvio-lacustrine deposits of the Permo-Carboniferous (Gzhelian/Asselian) Remigiusberg Formation at the Remigiusberg quarry near Kusel, Saar–Nahe Basin, southwest Germany. The new taxon is characterized by three autapomorphies within the Eryopidae: (1) the relatively narrow posterior skull table, therefore nearly parallel lateral margins of the skull; (2) the short postparietals and tabulars; and (3) the wide ectopterygoid. Phylogenetic analysis reveals a monophyletic Eryopidae with the basal taxa Osteophorus, Glaukerpeton, and Onchiodon labyrinthicus forming a polytomy. Actinodon may be either a basal eryopid or a stereospondylomorph, and the genus Onchiodon is not monophyletic. Stenokranio n. gen. is found as a more derived eryopid forming the sister taxon to Eryops. Stenokranio n. gen. was among the largest predators of the Saar–Nahe Basin. Its semiaquatic lifestyle enabled Stenokranio n. gen. to browse riverbanks and lake shorelines for prey, but most likely it fed on aquatic vertebrates. Stenokranio n. gen. was part of a faunal assemblage of aquatic, semiaquatic, and fully terrestrial vertebrates, such as sarcopterygian and actinopterygian fishes, xenacanthid sharks, a dvinosaurian temnospondyl, different “lepospondyls”, diadectomorphs, and synapsids. This is in general accordance with the vertebrate community from the Permo-Carboniferous of North America and from the early Permian localities of Manebach (Thuringian Forest Basin) and Niederhäslich (Döhlen Basin). It is notable that the occurrence of Stenokranio n. gen. and other eryopids in these localities excluded the presence of other large temnospondyls such as Sclerocephalus. However, a previously described isolated eryopid mandible from the Remigiusberg locality differs from that of Stenokranio n. gen. in several characters, implying that probably two different eryopid taxa lived at the same locality.UUID: www.zoobank.org/88a52547-d6fc-40af-965c-a6786c252ed5

Application of Participatory Methods to Explore Changes in Land Use of a Tropical Dry Forest Basin

Tropical hydrographic basins have undergone significant land use change processes in recent decades and correspond to areas of high population growth and development of economic activities. This article explores the causes of land use change in a tropical dry forest watershed, taking the Canalete river basin as a case study. For this purpose, stakeholder analysis techniques and participatory methods were applied. The results showed that the main causes of land use change in pastures were associated with biophysical factors, while forestsshrubs and crops were associated with direct and subyacents socioeconomics factors respectively. The participatory mapping allowed obtaining a desired land use scenario for the year 2030, observing a decrease of more than 16.2 ha of pasture, compensated by an increase of almost 2.4 thousand ha of crops and 13.8 thousand ha of forests and shrubs. Similarly, the hydrological impact of changes in land use was observed, especially in terms of flooding.

Survey of bedrock groundwater in a small forest basin consisting of metamorphic rocks in Hitachi Ohta Experimental Watershed

Survey of bedrock groundwater in a small forest basin consisting of metamorphic rocks in Hitachi Ohta Experimental Watershed

Establishing Modern Peat Analogs to Decipher Mangal Sub-Habitats From Historical Peats

In mangroves of South Florida, plant debris accumulates and humifies to form peat. The structure and composition of mangrove peat differs among mangal sub-habitats, leading to categorically distinct peat types reflective of the taphonomically active zone (TAZ). Here, taphonomic processes degrade and shape the peat until it is sequestered in the depth of final burial (DFB). Sequestered peats provide historical archives of the mangal depositional environment and the palaeoecological context of peat formation that are used to reconstruct mangal sub-habitats. However, as peat passes through the TAZ, information about the precursor mangal sub-habitat is reduced, which may skew mangrove community reconstructions. To better understand the influence of the TAZ on peat formation, we analyzed plant organ- and taxon-based measures by characterizing surficial mangrove peats from two contrasting mangal sub-habitats in Barnes Sound, Florida: a tidally influenced, Rhizophora-dominated fringe sub-habitat; and an inundated, interior mixed forest basin sub-habitat. We found (1) peats formed in basin sites have greater amounts of leaf litter, which correlates with reduced tidal activity and restricted detritivore access to the litter layer; (2) peats formed in fringe sites have higher root percentages, or root–shoot ratios, which provide a reliable method to differentiate between peats at depth, and (3) mangal sub-habitats differ in preserved organismal signals, such as foraminifera and insect parts. Further, we compare our surficial core samples to historical, deep core samples from other South Florida mangrove peat deposits to establish modern peat analogs needed to decipher preserved mangrove peats. These comparisons suggest that few aerial plant organs survive the TAZ and sequestered peats are biased towards root-rich peats characteristic of fringe sub-habitats; however, sequestered peats with lower root-shoot ratios indicate leaf litter-rich peats formed in basin sub-habitats.

Changes in Slope Stability over the Growth and Decay of Japanese Cedar Tree Roots

In Japan, repeated driftwood landslide disasters have become a major issue; thus, studies are required to better understand forest function to implement appropriate forest management and prevent such disasters. We investigated the effect of Japanese cedar tree roots on shallow landslide initiation. To incorporate the effect of roots on the two side-flanks of the shallow landslide, we propose a new slope-stability analysis method in which the sliding block is simplified as a three-prism model. The root reinforcement was approximated by the sum of the root pullout forces over a unit area, incorporating changes in the root strength with the growth of the trees after planting and the decay of the stumps after cutting. The reinforced root strength after the stump-cutting decreased linearly with time, with no strength remaining at 9 years. In contrast, the reinforced root strength of the new plants increased according to a logistic curve with time; thus, the root strength increased only slightly up to 9 years after planting, and the minimum total reinforced root strength was observed at this time. The safety factor of the slopes in a forest basin in Ibaraki Prefecture was calculated using the proposed three-prism method at intervals of 5 years on a 1-metre-resolution digital elevation model. The number of unstable grids peaked at 10 years, and a higher risk of slope instability was observed at 5–15 years. Therefore, implementing forest operations for lowering slope instability during this period should be important to prevent landslide disasters.

Eco-hydrological responses of the Black Dragon fire in three forested basins in the Daxing’an Mountains, northeast China

Understanding how bushfire affects basin-wide ecohydrological processes is critical for ecological restoration and water supply. However, the mechanisms responsible for post-fire streamflow remain poorly explored in forested basins of China due to complex scale-dependent relationships between fire-induced forest changes and ecohydrological processes, lack of reasonable design of paired watershed experiments, and especially data scarcity. Here, we re-examine ecohydrological responses of the Black Dragon fire (one of the largest and most damaging forest fires on record globally) on an annual scale in three forest basins (two fire-impacted basins, namely Emuer and Pangu, and a nearly unimpacted basin, Huma) in the Daxing’an Mountains using multiple most recent datasets and methods. We found that the Black Dragon fire decreased annual- and basin-averaged vegetation leaf area, evapotranspiration, interception loss, transpiration, soil moisture, runoff, and discharge capacity in 1987 in the two fire-impacted basins compared with the unimpacted basin. The annual- and basin-averaged evapotranspiration (runoff) did not reduce (increase) as much as that expected with decreased LAI given the precipitation amount in 1987 in the two fire-impacted basins, which properly linked to the quick postfire regrowth of vegetation in the growing season. Vegetation leaf area and productivity can quickly recover in the following two to three years postfire, but the hydrological systems need more than 10 years to adapt this disturbance. These findings improve the understanding of ecohydrological responses to bushfire disturbance and provide scientific evidence for ecological protection and water resources management under intensified natural and anthropogenic disturbances.

Base flow simulation using a physically based subsurface model – The case of a tropical basin in the Western Ghats, India

A novel framework that integrally uses groundwater and streamflow observations to calibrate a physically based sub surface model to generate base flow on a daily time step is presented in this study. Trend analysis on mean annual base flow time series showed that a declining trend was present in the basin though the upstream humid region was devoid of any trend. GLUE analysis was adopted to the simulation of base flow in the humid region and the most sensitive parameters were identified as the recharge factor (rf) and discharge factor (pd). The model was able to satisfactorily simulate base flow as observed values fell within the 95CI bands for the calibration period. The mean annual BFI values were computed at Muthankera to be 0.236 ± 0.02. The mean seasonal BFI varied from 48 % during post monsoon periods to 21 % during monsoon periods. The base flow simulated by the model was comparable to the output from the Eckhardt filter which has been widely cited to be a suitable baseflow separation method for many river basins. Due to the absence of groundwater level data in the transition region, a combination of model and digital filter was used to calibrate that region. The draft from the groundwater storage computed from the model was found to be highly nonlinear. The rf was seen to be lower and pd to be higher in the transition region than in the humid region. This would imply that in the transition region, the base flow is generated more gradually in comparison to the humid region. This was characteristic of forested basins where the uptake of water by deep rooted trees during evapotranspiration from the unsaturated zone causes delay in the water table response which in turn could result in delay in the base flow generation process. The consequence of the calibration exercise on Kabini basin was establishing that the heterogeneity in terms of precipitation and land use has resulted in the distinct hydrologic responses from the two regions in the basin.

Characterizing the impact of Land-Use/Land-Cover changes on a Temperate Forest using the Markov model

Land-Use/Land-Cover (LULC) change is one of the main factors contributing to ecosystem degradation and to the global climate change. The Markov Chains (MC) model is a widely used technique for the spatio-temporal evaluation of LULC changes, allowing the projection of the landscape variability based on the multidirectional potential of LULC changes. This study assessed the LULC changes in a disturbed temperate forest basin of northern México during the period 1990–2019. In addition, three LULC scenarios, employing the MC model, were projected for 2048. Supervised classification techniques were performed on data from Landsat sensors to generate LULC maps. Results from the Kappa Index showed a precision of 85 and 85.8% for the classifications of 1990 and 2019, respectively. During the evaluated period, degradation and deforestation processes in the basin were the main factors of disturbance, causing the pine-oak forest to show the biggest loss of coverage (190.81 km2). Conversely, open lands showed the biggest increase in its coverage, which indicates anthropogenic activities as the main driver causing changes on the ecosystem. Projections for 2048 indicate processes of degradation and deforestation will continue, expecting increases in coverage for open lands, deciduous forest, and secondary forest. The current and projected conditions of the landscape highlight the importance of the implementation of conservation and restoration strategies, as well as responsible public policies in the study area to mitigate the impacts on these ecosystems.

Sensitivity analysis of hydrological processes to perturbed climate in a southern boreal forest basin

Hydrological processes over and through frozen and unfrozen ground were simulated in the well instrumented boreal forest basin of White Gull Creek, Saskatchewan, Canada using a model created using the flexible Cold Regions Hydrological Modelling (CRHM) platform. The CRHM-created Boreal Hydrology Model was structured and initially parameterized using decades of process hydrology research in the southern boreal forest with minor parameter calibration, and generally produced quite good performance on simultaneously reproducing the measurements of runoff, snow water equivalent (SWE), soil liquid water content and eddy correlation flux tower observations of evapotranspiration (ET) over two decades. To examine the sensitivity of basin hydrology to perturbed climate inputs, air temperature (T) inputs were set up by linear increments in the reference observation of up to +6 ℃, and precipitation (P) inputs were generated by multiplying the reference observed P from 70% to 130%. The model results showed that the basin hydrological variables showed quite different sensitivities to perturbations of P and T. The volume of annual runoff and the annual runoff coefficient increased more rapidly with rising P, at rates of 31% and 16% per 10% increase in P, but decreased by only 3.8% and 4.7% per 1 ℃ of warming. Annual ET increased rapidly with temperature, by 7% per 1 ℃ of warming and therefore drove the streamflow volumetric changes with warming, but increased only 1% per 10% increase in P. Perturbations of P and T had distinctively different influences on the streamflow regime. Increased P enhanced the intra- and inter-annual variabilities of basin runoff, reduced the relative contribution of winter runoff to annual runoff and increased the relative contribution of summer runoff; whilst rising T resulted in the inverse changes in the streamflow regime. Effects of warming on some hydrological processes could be compensated for to varying degrees by the effects of increases in P. Reductions in the annual runoff volume and runoff coefficient caused by warming up to 6 ℃ could be compensated for by increases of <20% in P. However, the maximum increase in P (+30%) examined could only compensate for the changes in snow processes caused by warming of less than 4 ℃ and snow-cover duration decreases with 1 ℃ warming could not be compensated for by any precipitation increase considered. These results inform the vulnerability of boreal forest hydrology to the first-order changes in P and T and provide guidance for further climate impact assessments for hydrology in the southern boreal forest in Canada.

Local Drivers Associated to Temporal Spectral Response of Chlorophyll-a in Mangrove Leaves

The pigment content in leaves has commonly been used to characterize vegetation condition. However, few studies have assessed temporal changes of local biotic and abiotic factors on leaf pigments. Here, we evaluated the effect of local environmental variables and tree structural characteristics, in the chlorophyll-a leaf concentration (Chl-a) associated with temporal change in two mangrove species. Rhizophora mangle (R. mangle) and Avicennia germinans (A. germinans) trees of a fringe mangrove forest (FMF) and lower basin mangrove forest (BMF) were visited over a period of one year, to obtain radiometric readings at leaf level to estimate Chl-a. Measurements on tree characteristics included diameter at breast height (DBH), basal area (BA), and maximum height (H). Environmental variables included soil interstitial water temperature (Ti), salinity (Si), and dissolved oxygen (Oi), flood level (fL), ambient temperature (Tamb), and relative humidity (Hrel). Generalized linear models and covariance analysis showed that the variation of Chl-a is mainly influenced by the species, the interaction between species and mangrove forest type, DBH, seasonality and its influence on the species, soil conditions, and fL. Studies to assess spatial and temporal change on mangrove forests using the spectral characteristics of the trees should also consider the temporal variation of leave chlorophyll-a concentration.

Latest Carboniferous to early Permian volcano-stratigraphic evolution in Central Europe: U\u2013Pb CA\u2013ID\u2013TIMS ages of volcanic rocks in the Thuringian Forest Basin (Germany)

Mainly acidic Stephanian to early Permian volcanic rocks and intercalated sediments accumulated in the Thuringian Forest Basin (TFB) in central Germany to a total thickness of ca. 2000 m. This basin offers a wide range of biostratigraphic information. New high-precision U–Pb CA–ID–TIMS (chemical abrasion–isotope dilution–thermal ionization mass spectrometry) zircon data are obtained from volcanic rocks for the first time in the TFB. Pre-treatment of the zircons by chemical abrasion was important to get rid of severe Pb loss. The zircon ages of the investigated formations indicate that the total duration of the volcanic activity in the TFB was considerably shorter [ca. 4 Myr: from 300 Ma for the oldest formation (Möhrenbach) until ca. 296 Ma for the youngest volcanic-rock-bearing formation (Rotterode)] than suggested in previous studies (ca. 20 Myr; 295 Ma to 275 Ma). Consequently, the well-documented gap of the sedimentary record from the early Permian volcanic rocks up to the Illawarra geomagnetic reversal has to be extended to ca. 25 Myr from the previously proposed 5 Myr. The zircon ages of the investigated volcanic rocks allow the constraining of some intercalated fossiliferous horizons crucial for biostratigraphic correlation of latest Carboniferous–early Permian (Rotliegend) sections. The high-precision age data require a new interpretation of the evolution of the TFB but also offer the chance to obtain a more reliable comparison of the timing of the main magmatic activity across intramontane basins as well as to obtain links to the Standard Global Stratigraphic Scale.

Simulation of nitrogen and phosphorus pollution in typical agricultural and forested basins as well as relevant reduction effect based on SWAT model

Abstract Non-point source nitrogen and phosphorus pollution is a critical threat to aquatic ecosystems and a potential risk to drinking water safety. To precisely control nitrogen and phosphorus pollution in the river basin, in this study, we identified key pollution areas of the river basin, analyzed the main characteristics of pollution sources as well as their contribution to the river basin pollution, and conducted simulation analysis on reduction measures based on the SWAT model. The results showed the following. (1) The simulation effect of the calibrated model was good, and sub-basins 3, 39 and 96 were the key source areas, the main sources of pollution were combined pollution from livestock and poultry breeding and planting industry. (2) Crops had the largest input and output for both nitrogen and phosphorus, the output of which was 6,137.8 t/a and 562.4 t/a respectively. The urban point sources had the highest output rates of nitrogen and phosphorus, 75.7% and 67.5% respectively. (3) With the optimal combination of reduction measures, nitrogen and phosphorus were reduced by 1,438.9 t and 85.3 t respectively, i.e., the reduction rates were the highest. The reduction effect for total nitrogen was better than that for total phosphorus.

Extensive genetic diversity of Plasmodium vivax dbp-II in Rio de Janeiro Atlantic Forest and Brazilian Amazon Basin: evidence of positive selection

BackgroundPlasmodium vivax is the most widespread human malaria parasite outside Africa and is the predominant parasite in the Americas. Increasing reports of P. vivax disease severity, together with the emergence of drug-resistant strains, underscore the urgency of the development of vaccines against P. vivax. Polymorphisms on DBP-II-gene could act as an immune evasion mechanism and, consequently, limited the vaccine efficacy. This study aimed to investigate the pvdbp-II genetic diversity in two Brazilian regions with different epidemiological patterns: the unstable transmission area in the Atlantic Forest (AF) of Rio de Janeiro and; the fixed malaria-endemic area in Brazilian Amazon (BA).Methods216 Brazilian P. vivax infected blood samples, diagnosed by microscopic examination and PCR, were investigated. The region flanking pvdbp-II was amplified by PCR and sequenced. Genetic polymorphisms of pvdbp-II were estimated based on the number of segregating sites and nucleotide and haplotype diversities; the degree of differentiation between-regions was evaluated applying Wright’s statistics. Natural selection was calculated using the rate of nonsynonymous per synonymous substitutions with the Z-test, and the evolutionary distance was estimated based on the reconstructed tree.Results79 samples from AF and 137 from BA were successfully sequenced. The analyses showed 28 polymorphic sites distributed in 21 codons, with only 5% of the samples Salvador 1 type. The highest rates of polymorphic sites were found in B- and T cell epitopes. Unexpectedly, the nucleotide diversity in pvdbp-II was higher in AF (0.01) than in BA (0.008). Among the 28 SNPs detected, 18 are shared between P. vivax isolates from AF and BA regions, but 8 SNPs were exclusively detected in AF—I322S, K371N, E385Q, E385T, K386T, K411N, I419L and I419R—and 2 (N375D and I419M) arose exclusively in BA. These findings could suggest the potential of these geographical clusters as population-specific-signatures that may be useful to track the origin of infections. The sample size should be increased in order to confirm this possibility.ConclusionsThe results highlight that the pvdbp-II polymorphisms are positively selected by host’s immune pressure. The characterization of pvdbp-II polymorphisms might be useful for designing effective DBP-II-based vaccines.

The Harvest of Tsam-Tsam in a Congolese Bowl: Body Adaptations of Harvesters

This exploratory and diagnostic standard study on the harvesters of local wine made from date palm aims to assess the effects of the practice of harvesting tsam-tsam, on the arch of the palm and thickening-hardening of the palm in the tsam-tsam harvesters in the marshy environment of the Congolese forest basin. This experimental, longitudinal, analytical and comparative study, exclusively concerned only the harvesters of swampy and non-swampy areas. Out of a population of 85 harvesters from different villages, 55 harvesters from villages in the districts of Makoua and Owando in the northern part of the country were chosen. It took place in the period of July 15, 2018 and July 19, 2019. The non-probabilistic method and the reasoned sampling technique were used for the choice of subjects. The subjects were randomized into two groups: a first experimental group (GE = 25) operating in the marshy area, a second control group (GC = 30) in the non-marshy area. The kinesiology technique based on the podoscope to be scanned with a manual platform made it possible to appreciate the effect of the marshy environment on deformations of the arch of the palm of the hand of tsam-tsam harvesters. The results showed that the values of the arch of the hands are significantly higher in the tsam-tsam harvesters living in the swampy area than those in the non-swampy area. The mercantile activity of the harvest of the local drink based on the sap of the date palm, helps fight poverty, and generates various deformations in the arch of the feet, from the hands of practitioners.