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Tropical forest soils are a significant source for the greenhouse gas N2O as well as for NO, a precursor of tropospheric ozone. However, current estimates are uncertain due to the limited number of field measurements. Furthermore, there is considerable spatial and temporal variability of N2O and NO emissions due to the variation of environmental conditions such as soil properties, vegetation characteristics and meteorology. In this study we used a process-based model (ForestDNDC-tropica) to estimate N2O and NO emissions from tropical highland forest (Nyungwe) soils in southwestern Rwanda. To extend the model inputs to regional scale, ForestDNDC-tropica was linked to an exceptionally large legacy soil dataset. There was agreement between N2O and NO measurements and the model predictions though the ForestDNDC-tropica resulted in considerable lower emissions for few sites. Low similarity was specifically found for acidic soil with high clay content and reduced metals, indicating that chemo-denitrification processes on acidic soils might be under-represented in the current ForestDNDC-tropica model. The results showed that soil bulk density and pH are the most influential factors driving spatial variations in soil N2O and NO emissions for tropical forest soils. The area investigated (1113 km²) was estimated to emit ca. 439±50 tN2O-Nyr-1 (2.8-5.5 kgN2O-Nha-1 yr-1) and 244±16 tNO-Nyr-1 (0.8-5.1 kgNha-1 yr-1). Consistent with less detailed studies, we confirm that tropical highland rainforest soils are a major source of atmospheric N2O and NO. [ABSTRACT FROM AUTHOR]

Abstract: Forest soils contain the largest carbon stock of all terrestrial biomes and are probably the most important source of carbon dioxide (CO2) to atmosphere. Soil CO2 fluxes from 54 to 72-year-old monospecific stands in Rwanda were quantified from March 2006 to December 2007. The influences of soil temperature, soil water content, soil carbon (C) and nitrogen (N) stocks, soil pH, and stand characteristics on soil CO2 flux were investigated. The mean annual soil CO2 flux was highest under Eucalyptus saligna (3.92μmol m−2 s−1) and lowest under Entandrophragma excelsum (3.13μmol m−2 s−1). The seasonal variation in soil CO2 flux from all stands followed the same trend and was highest in rainy seasons and lowest in dry seasons. Soil CO2 flux was mainly correlated to soil water content (R 2 =0.36–0.77), stand age (R 2 =0.45), soil C stock (R 2 =0.33), basal area (R 2 =0.21), and soil temperature (R 2 =0.06–0.17). The results contribute to the understanding of factors that influence soil CO2 flux in monocultural plantations grown under the same microclimatic and soil conditions. The results can be used to construct models that predict soil CO2 emissions in the tropics. [Copyright &y& Elsevier]

Current estimates of temperature effects on plants mostly rely on air temperature, although it can significantly deviate from leaf temperature (T leaf ). To address this, some studies have used canopy temperature (T can ). However, T can fails to capture the fine-scale variation in T leaf among leaves and species in diverse canopies. We used infrared radiometers to study T leaf and T can and how they deviate from air temperature (ΔT leaf and ΔT can ) in multispecies tropical tree plantations at three sites along an elevation and temperature gradient in Rwanda. Our results showed high T leaf (up to c. 50°C) and ΔT leaf (on average 8-10°C and up to c. 20°C) of sun-exposed leaves during 10:00 h-15:00 h, being close to or exceeding photosynthetic heat tolerance thresholds. These values greatly exceeded simultaneously measured values of T can and ΔT can , respectively, leading to strongly overestimated leaf thermal safety margins if basing those on T can data. Stomatal conductance and leaf size affected T leaf and T can in line with their expected influences on leaf energy balance. Our findings highlight the importance of leaf traits for leaf thermoregulation and show that monitoring T can is not enough to capture the peak temperatures and heat stress experienced by individual leaves of different species in tropical forest canopies., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

Plants face a trade-off between hydraulic safety and growth, leading to a range of water-use strategies in different species. However, little is known about such strategies in tropical trees and whether different water-use traits can acclimate to warming. We studied five water-use traits in 20 tropical tree species grown at three different altitudes in Rwanda (RwandaTREE): stomatal conductance (g s ), leaf minimum conductance (g min ), plant hydraulic conductance (K plant ), leaf osmotic potential (ψ o ) and net defoliation during drought. We also explored the links between these traits and growth and mortality data. Late successional (LS) species had low K plant , g s and g min and, thus, low water loss, while low ψ o helped improve leaf water status during drought. Early successional (ES) species, on the contrary, used more water during both moist and dry conditions and exhibited pronounced drought defoliation. The ES strategy was associated with lower mortality and more pronounced growth enhancement at the warmer sites compared to LS species. While K plant and g min showed downward acclimation in warmer climates, ψ o did not acclimate and g s measured at prevailing temperature did not change. Due to distinctly different water use strategies between successional groups, ES species may be better equipped for a warmer climate as long as defoliation can bridge drought periods., (© 2024 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.)

The productivity and climate feedbacks of tropical forests depend on tree physiological responses to warmer and, over large areas, seasonally drier conditions. However, knowledge regarding such responses is limited due to data scarcity. We studied the impact of growth temperature on net photosynthesis (An), maximum rates of Rubisco carboxylation at 25 °C (Vcmax25), stomatal conductance (gs) and the slope parameter of the stomatal conductance-photosynthesis model (g1), in 10 early successional (ES) and 8 late-successional (LS) tropical tree species grown at three sites along an elevation gradient in Rwanda, differing by 6.8 °C in daytime ambient air temperature. The effect of seasonal drought on An was also investigated. We found that warm climate decreased wet-season An in LS species, but not in ES species. Values of Vcmax25 were lower at the warmest site across both successional groups, and An and Vcmax25 were higher in ES compared with LS species. Stomatal conductance exhibited no significant site differences and g1 was similar across both sites and successional groups. Drought strongly reduced An at warmer sites but not at the coolest montane site and this response was similar in both ES and LS species. Our results suggest that warming has negative effects on leaf-level photosynthesis in LS species, while both LS and ES species suffer photosynthesis declines in a warmer climate with more pronounced droughts. The contrasting responses of An between successional groups may lead to shifts in species' competitive balance in a warmer world, to the disadvantage of LS trees., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Warming climate increases the risk for harmful leaf temperatures in terrestrial plants, causing heat stress and loss of productivity. The heat sensitivity may be particularly high in equatorial tropical tree species adapted to a thermally stable climate. Thermal thresholds of the photosynthetic system of sun-exposed leaves were investigated in three tropical montane tree species native to Rwanda with different growth and water use strategies (Harungana montana, Syzygium guineense and Entandrophragma exselsum). Measurements of chlorophyll fluorescence, leaf gas exchange, morphology, chemistry and temperature were made at three common gardens along an elevation/temperature gradient. Heat tolerance acclimated to maximum leaf temperature (T leaf ) across the species. At the warmest sites, the thermal threshold for normal function of photosystem II was exceeded in the species with the highest T leaf despite their higher heat tolerance. This was not the case in the species with the highest transpiration rates and lowest T leaf . The results point to two differently effective strategies for managing thermal stress: tolerance through physiological adjustment of leaf osmolality and thylakoid membrane lipid composition, or avoidance through morphological adaptation and transpiratory cooling. More severe photosynthetic heat stress in low-transpiring montane climax species may result in a competitive disadvantage compared to high-transpiring pioneer species with more efficient leaf cooling., (© 2021 The Authors. New Phytologist © 2021 New Phytologist Foundation.)

The temperature sensitivity of physiological processes and growth of tropical trees remains a key uncertainty in predicting how tropical forests will adjust to future climates. In particular, our knowledge regarding warming responses of photosynthesis, and its underlying biochemical mechanisms, is very limited. We grew seedlings of two tropical montane rainforest tree species, the early-successional species Harungana montana and the late-successional species Syzygium guineense, at three different sites along an elevation gradient, differing by 6.8℃ in daytime ambient air temperature. Their physiological and growth performance was investigated at each site. The optimum temperature of net photosynthesis (T optA ) did not significantly increase in warm-grown trees in either species. Similarly, the thermal optima (T optV and T optJ ) and activation energies (E aV and E aJ ) of maximum Rubisco carboxylation capacity (V cmax ) and maximum electron transport rate (J max ) were largely unaffected by warming. However, V cmax , J max and foliar dark respiration (R d ) at 25℃ were significantly reduced by warming in both species, and this decline was partly associated with concomitant reduction in total leaf nitrogen content. The ratio of J max /V cmax decreased with increasing leaf temperature for both species, but the ratio at 25℃ was constant across sites. Furthermore, in H. montana, stomatal conductance at 25℃ remained constant across the different temperature treatments, while in S. guineense it increased with warming. Total dry biomass increased with warming in H. montana but remained constant in S. guineense. The biomass allocated to roots, stem and leaves was not affected by warming in H. montana, whereas the biomass allocated to roots significantly increased in S. guineense. Overall, our findings show that in these two tropical montane rainforest tree species, the capacity to acclimate the thermal optimum of photosynthesis is limited while warming-induced reductions in respiration and photosynthetic capacity rates are tightly coupled and linked to responses of leaf nitrogen., (© 2021 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Tropical climates are getting warmer, with pronounced dry periods in large areas. The productivity and climate feedbacks of future tropical forests depend on the ability of trees to acclimate their physiological processes, such as leaf dark respiration (R d ), to these new conditions. However, knowledge on this is currently limited due to data scarcity. We studied the impact of growth temperature on R d and its dependency on net photosynthesis (A n ), leaf nitrogen (N) and phosphorus (P) contents, and leaf mass per unit area (LMA) in 16 early-successional (ES) and late-successional (LS) tropical tree species in multispecies plantations along an elevation gradient (Rwanda TREE project). Moreover, we explored the effect of drought on R d in one ES and one LS species. Leaf R d at 20°C decreased at warmer sites, regardless if it was expressed per unit leaf area, mass, N or P. This acclimation resulted in an 8% and a 28% decrease in R d at prevailing nighttime temperatures in trees at the intermediate and warmest sites, respectively. Moreover, drought reduced R d , particularly in the ES species and at the coolest site. Thermal acclimation of R d is complete or overcompensatory and independent of changes in leaf nutrients or LMA in African tropical trees., (© 2020 The Authors New Phytologist © 2020 New Phytologist Foundation.)

Tropical canopies are complex, with multiple canopy layers and pronounced gap dynamics contributing to their high species diversity and productivity. An important reason for this complexity is the large variation in shade tolerance among different tree species. At present, we lack a clear understanding of which plant traits control this variation, e.g., regarding the relative contributions of whole-plant versus leaf traits or structural versus physiological traits. We investigated a broad range of traits in six tropical montane rainforest tree species with different degrees of shade tolerance, grown under three different radiation regimes (under the open sky or beneath sparse or dense canopies). The two distinct shade-tolerant species had higher fractional biomass in leaves and branches while shade-intolerant species invested more into stems, and these differences were greater under low radiation. Leaf respiration and photosynthetic light compensation point did not vary with species shade tolerance, regardless of radiation regime. Leaf temperatures in open plots were markedly higher in shade-tolerant species due to their low transpiration rates and large leaf sizes. Our results suggest that interspecific variation in shade tolerance of tropical montane trees is controlled by species differences in whole-plant biomass allocation strategy rather than by difference in physiological leaf traits determining leaf carbon balance at low radiation., (© The Author(s) 2019. Published by Oxford University Press.)

House flies (Musca domestica) are widespread, synanthropic filth flies commonly found on decaying matter, garbage, and feces as well as human food. They have been shown to vector microbes, including clinically relevant pathogens. Previous studies have demonstrated that house flies carry a complex and variable prokaryotic microbiota, but the main drivers underlying this variability and the influence of habitat on the microbiota remain understudied. Moreover, the differences between the external and internal microbiota and the eukaryotic components have not been examined. To obtain a comprehensive view of the fly microbiota and its environmental drivers, we sampled over 400 flies from two geographically distinct countries (Belgium and Rwanda) and three different environments-farms, homes, and hospitals. Both the internal as well as external microbiota of the house flies were studied, using amplicon sequencing targeting both bacteria and fungi. Results show that the house fly's internal bacterial community is very diverse yet relatively consistent across geographic location and habitat, dominated by genera Staphylococcus and Weissella. The external bacterial community, however, varies with geographic location and habitat. The fly fungal microbiota carries a distinct signature correlating with the country of sampling, with order Capnodiales and genus Wallemia dominating Belgian flies and genus Cladosporium dominating Rwandan fly samples. Together, our results reveal an intricate country-specific pattern for fungal communities, a relatively stable internal bacterial microbiota and a variable external bacterial microbiota that depends on geographical location and habitat. These findings suggest that vectoring of a wide spectrum of environmental microbes occurs principally through the external fly body surface, while the internal microbiome is likely more limited by fly physiology.

We describe the isolation and characterization of three bacterial isolates from the common house fly, Musca domestica , caught in Londerzeel, Belgium and Huye District, Rwanda. Although isolated from distinct geographical locations, the strains show >99 % identical 16S rRNA gene sequences and are <95 % identical to type strains of Apibacter species. Whole-genome sequences were obtained for all three strains. The genomes are 2.4-2.5 Mb with a G+C content of ~30.3 mol%. Bacteriological and biochemical analysis of the strains demonstrate distinctly different characteristics compared to known Apibacter species. Particularly, the three strains investigated in this study can be distinguished from the known Apibacter species ( Apibacter mensalis and Apibacter adventoris ) through urease and β-glucosidase activities. Whole-cell fatty acid methyl ester analysis shows that the fatty acid composition of the novel strains is also unique. On the basis of phylogenetic, genotypic and phenotypic data, we propose to classify these isolates as representatives of a novel species of the genus Apibacter, Apibacter muscae sp. nov., in reference to its prevalence in house flies, with strain G8 T (=LMG 30898 T =DSM 107922 T ) as the type strain.

Objective: To evaluate the long-term retention of skills gained by rural physicians who completed a postpartum hemorrhage simulation-training program., Methods: A quasi-experimental pre-post intervention study enrolled a convenience sample of generalist physicians in rural Rwanda. Participants underwent initial simulation training including pre- and post-training testing in February 2012. Simulation drills to assess skill retention were conducted in March 2014. Participants were scored based on their communication, evaluation, and management skills. Median scores and inter-quartile ranges were calculated and the Wilcoxon signed-rank sum test was used to compare the pre-training, post-training, and retention scores. Physician confidence was assessed using a survey., Results: In total, 11 physicians were enrolled; eight were available for the 2-year skill-retention evaluation. Significant improvements were observed when comparing participants' pre-training and post-training communication (P=0.03), evaluation (P=0.05), and management (P=0.02) scores, and there were no changes between participants' post-training and 2-year communication (P>0.99), evaluation (P=0.16), and management (P=0.46) scores. There were no differences in the self-reported confidence measures across the duration of the study., Conclusion: Simulation training is an effective method for teaching postpartum hemorrhage-management skills to generalist physicians in rural areas and skills are retained for at least 2 years. Further studies could determine the optimal time intervals for refresher training., (Copyright © 2016 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.)

To evaluate the effectiveness of decentralizing ambulatory reproductive and intrapartum services to increase rates of antenatal care (ANC) utilization and skilled attendance at birth (SAB) in Rwanda. A prospective cohort study was implemented with one control and two intervention sites: decentralized ambulatory reproductive healthcare and decentralized intrapartum care. Multivariate logistic regression analysis was performed with primary outcome of lack of SAB and secondary outcome of ≥3 ANC visits. 536 women were entered in the study. Distance lived from delivery site significantly predicted SAB (p = 0.007), however distance lived to ANC site did not predict ≥3 ANC visits (p = 0.81). Neither decentralization of ambulatory reproductive healthcare (p = 0.10) nor intrapartum care (p = 0.40) was significantly associated with SAB. The control site had the greatest percentage of women receive ≥3 ANC visits (p < 0.001). Receiving <3 ANC visits was associated with a 3.98 times greater odds of not having SAB (p = 0.001). No increase in adverse outcomes was found with decentralization of ambulatory reproductive health care or intrapartum care. The factors that predict utilization of physically accessible services in rural Africa are complex. Decentralization of services may be one strategy to increase rates of SAB and ANC utilization, but selection biases may have precluded accurate analysis. Efforts to increase ANC utilization may be a worthwhile investment to increase SAB.

The sensitivity of photosynthetic metabolism to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial feedback on future climate change. While temperature responses of photosynthetic capacities have been comparatively well investigated in temperate species, the responses of tropical tree species remain unexplored. We compared the responses of seedlings of native cold-adapted tropical montane rainforest tree species with those of exotic warm-adapted plantation species, all growing in an intermediate temperature common garden in Rwanda. Leaf gas exchange responses to carbon dioxide (CO2 ) at different temperatures (20-40°C) were used to assess the temperature responses of biochemical photosynthetic capacities. Analyses revealed a lower optimum temperature for photosynthetic electron transport rates than for Rubisco carboxylation rates, along with lower electron transport optima in the native cold-adapted than in the exotic warm-adapted species. The photosynthetic optimum temperatures were generally exceeded by daytime peak leaf temperatures, in particular in the native montane rainforest climax species. This study thus provides evidence of pronounced negative effects of high temperature in tropical trees and indicates high susceptibility of montane rainforest climax species to future global warming., (© 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.)

Photosynthetic capacity of tree leaves is typically positively related to nutrient content and little affected by changes in growth temperature. These relationships are, however, often poorly supported for tropical trees, for which interspecific differences may be more strongly controlled by within-leaf nutrient allocation than by absolute leaf nutrient content, and little is known regarding photosynthetic acclimation to temperature. To explore the influence of leaf nutrient status, successional strategy and growth temperature on the photosynthetic capacity of tropical trees, we collected data on photosynthetic, chemical and morphological leaf traits of ten tree species in Rwanda. Seven species were studied in a forest plantation at mid-altitude (~1,700 m), whereas six species were studied in a cooler montane rainforest at higher altitude (~2,500 m). Three species were common to both sites, and, in the montane rainforest, three pioneer species and three climax species were investigated. Across species, interspecific variation in photosynthetic capacity was not related to leaf nutrient content. Instead, this variation was related to differences in within-leaf nitrogen allocation, with a tradeoff between investments into compounds related to photosynthetic capacity (higher in pioneer species) versus light-harvesting compounds (higher in climax species). Photosynthetic capacity was significantly lower at the warmer site at 1,700 m altitude. We conclude that (1) within-leaf nutrient allocation is more important than leaf nutrient content per se in controlling interspecific variation in photosynthetic capacity among tree species in tropical Rwanda, and that (2) tropical montane rainforest species exhibit decreased photosynthetic capacity when grown in a warmer environment.

Objective: To evaluate the perceptions of healthcare and traditional medicine providers regarding the type, indications, side effects, and prevalence of traditional medicine use amongst pregnant women in a rural Rwandan population., Methods: Six focus groups with physicians, nurses, and community health workers and four individual in-depth interviews with traditional medicine providers were held. Qualitative data was gathered using a structured questionnaire querying perceptions of the type, indications, side effects, and prevalence of use of traditional medicines in pregnancy., Results: The healthcare provider groups perceived a high prevalence of traditional botanical medicine use by pregnant women (50-80%). All three groups reported similar indications for use of the medicines and the socioeconomic status of the pregnant women who use them. The traditional medicine providers and the healthcare providers both perceived that the most commonly used medicine is a mixture of many plants, called Inkuri. The most serious side effect reported was abnormally bright green meconium with a poor neonatal respiratory drive. Thirty-five traditional medicines were identified that are used during pregnancy., Conclusion: Perceptions of high prevalence of use of traditional medicines during pregnancy with possible negative perinatal outcomes exist in areas of rural Rwanda.

Using the point count method, linear mixed models, Shannon's diversity index, and Bray-Curtis cluster analysis, we conducted a study of the effect of urban fabric layout on bird diversity and distribution in northern Rwanda. The results showed a significant effect of city landscapes on bird richness and relative abundance; residential neighborhoods, institutional grounds, and informal settlements had the highest species diversity in comparison to other microlandscape types. Riversides were characterized by specialized bird species, commonly known to be restricted to wetland environments. Built-up areas and open field landscapes had comparable results. One Albertine Rift endemic bird species, the Ruwenzori Double-collared Sunbird (Cinnyris stuhlmanni), was recorded. Three migratory birds were found in Musanze city for the first time: the Common Sandpiper (Actitis hypoleucos), the Spotted Flycatcher (Muscicapa striata), and the Willow Warbler (Phylloscopus trochilus). Two bird species have not been previously reported in Rwanda: the Garden Warbler (Sylvia borin) and the Lesser Spotted Eagle (Aquila pomarina). The implications of this study are particularly relevant to urban decision makers who should consider the existence of a great diversity of avian fauna when developing and implementing master plans, especially when villages and cities are in proximity of protected areas or natural reserves.