Abstract. Climate models predict amplified warming at high elevations in low latitudes, making tropical glacierized regions some of the most vulnerable hydrological systems in the world. Observations reveal decreasing streamflow due to retreating glaciers in the Andes, which hold 99 % of all tropical glaciers. However, the timescales over which meltwater contributes to streamflow and the pathways it takes – surface and subsurface – remain uncertain, hindering our ability to predict how shrinking glaciers will impact water resources. Two major contributors to this uncertainty are the sparsity of hydrologic measurements in tropical glacierized watersheds and the complication of hydrograph separation where there is year-round glacier melt. We address these challenges using a multi-method approach that employs repeat hydrochemical mixing model analysis, hydroclimatic time series analysis, and integrated watershed modeling. Each of these approaches interrogates distinct timescale relationships among meltwater, groundwater, and stream discharge. Our results challenge the commonly held conceptual model that glaciers buffer discharge variability. Instead, in a subhumid watershed on Volcán Chimborazo, Ecuador, glacier melt drives nearly all the variability in discharge (Pearson correlation coefficient of 0.89 in simulations), with glaciers contributing a broad range of 20 %–60 % or wider of discharge, mostly (86 %) through surface runoff on hourly timescales, but also through infiltration that increases annual groundwater contributions by nearly 20 %. We further found that rainfall may enhance glacier melt contributions to discharge at timescales that complement glacier melt production, possibly explaining why minimum discharge occurred at the study site during warm but dry El Niño conditions, which typically heighten melt in the Andes. Our findings caution against extrapolations from isolated measurements: stream discharge and glacier melt contributions in tropical glacierized systems can change substantially at hourly to interannual timescales, due to climatic variability and surface to subsurface flow processes.

Abstract. Climate models predict amplified warming at high elevations in low latitudes, making tropical glacierized regions some of the most vulnerable hydrological systems in the world. Observations reveal decreasing streamflow due to retreating glaciers in the Andes, which hold 99% of all tropical glaciers. However, the timescales over which meltwater contributes to streamflow and the pathways it takes -surface and subsurface -remain uncertain, hindering our ability to predict how shrinking glaciers will impact water resources. Two major contributors to this uncertainty are the sparsity of hydrologic mea-5 surements in tropical glacierized watersheds and the complication of hydrograph separation where there is year-round glacier melt. We address these challenges using a multi-method approach that employs repeat hydrochemical mixing model analysis, hydroclimatic time series analysis, and integrated watershed modeling. Each of these approaches interrogates distinct timescale relationships among meltwater, groundwater, and stream discharge. Our results challenge the commonly held conceptual model that glaciers buffer discharge variability. Instead, in a sub-humid watershed on Volcán Chimborazo, Ecuador, meltwater drives 10 nearly all the variability in discharge (Pearson correlation coefficient of 0.89 in simulations), with glaciers contributing a broad range of 20-60% or wider of discharge, mostly (86%) through surface runoff on hourly timescales, but also through infiltration that increases annual groundwater contributions by nearly 20%. We further found that rainfall may enhance melt contributions to discharge at timescales that complement melt generation, possibly explaining why minimum discharge occurred at the study site during warm but dry El Niño conditions, which typically heighten melt in the Andes. Our findings caution against extrap-15 olations from isolated measurements: stream discharge and meltwater contributions in tropical glacierized systems can change substantially at hourly to interannual timescales, due to climatic variability and surface to subsurface flow processes.

Since 2000, wild black cherry (Prunus serotina Ehrh.) has produced erratic seed crops, especially in the Allegheny National Forest where poor seed production has been implicated in difficulties with black cherry regeneration in forest stands. Given that black cherry is insect pollinated and unable to produce viable seed from self-pollination, a reduction in seed crops could be due to a pollination deficit; however, its key pollinators are unknown. Identifying the pollinators and factors that influence pollinator abundance and fidelity is critical for supporting and enhancing seed production for this valuable timber species. Over a two-year period in developed, semideveloped, and forested areas in Pennsylvania, we identified the potential pollinators of black cherry and examined how their abundance, along with several other abiotic and biotic factors, influenced viable seed production. We found that andrenid (Andrenidae: Hymenoptera) bees are likely the most important pollinators. The proportion of viable seeds increased as the number of andrenids increased, and these ground nesting bees were most abundant on forest edges, highlighting this habitat’s potential to support pollination services. Andrenids carried an average of 347-fold more black cherry pollen than flies and 18-fold more than halictid (Halictidae: Hymenoptera) bees. We did not find a significant relationship between the abundance of any other taxa besides andrenids and viable seed production. Black cherry flowers also provide resources for natural enemies such as the economically important parasitoid of Popillia japonica Newman (Scarabaeidae: Coleoptera), Tiphia vernalis Rohwer (Tiphiidae: Hymenoptera), which was observed feeding on black cherry nectar in this study.

No abstract

ObjectiveRepeat urgent cesarean sections (CS) carry an increased risk of severe maternal outcomes. As CS increase in sub-Saharan Africa, creative strategies are necessary to reduce the rate of urgent repeat CS. The Zigama-Mama Project in rural Burundi uses complimentary ultrasounds to create a clinical touchpoint to counsel women with a prior CS for a hospital-based delivery.MethodsFrom July 2019 to June 2020, complimentary ultrasounds were offered to all antenatal patients with prior CS, along with counseling for monitored trial of labor after cesarean (TOLAC) or scheduled repeat CS. Community engagement and feedback from district health centers were evaluated.ResultsIn total, 500 women with a prior CS presented for a complimentary ultrasound. During the intervention year, a relative and absolute reduction in urgent repeat CS (baseline: n = 114 {70.8%}, intervention: n = 97{49.7%}, p < 0.001) was observed, with no significant change in maternal mortality or ruptured uteri. All health center personnel agreed the project improved their confidence in referring women with prior CS.ConclusionOffering complimentary ultrasounds as a clinical touchpoint for scheduling a monitored delivery or CS for women at high risk for delivery complication may be an affordable and creative strategy to care for women with previous CS during subsequent deliveries.