Seasonal dynamics and exports of elements from a first‐order stream to a large inland lake in Michigan

Headwater streams are critical components of drainage systems, directly connecting terrestrial and downstream aquatic ecosystems. The amount of water in a stream can alter hydrologic connectivity between the stream and surrounding landscape and is ultimately an important driver of what constituents headwater streams transport. There is a shortage of studies that explore concentration–discharge (C‐Q) relationships in headwater systems, especially forested watersheds, where the hydrological and ecological processes that control the processing and export of solutes can be directly investigated. We sought to identify the temporal dynamics and spatial patterns of stream chemistry at three points along a forested headwater stream in Northern Michigan and utilize C‐Q relationships to explore transport dynamics and potential sources of solutes in the stream. Along the stream, surface flow was seasonal in the main stem, and perennial flow was spatially discontinuous for all but the lowest reaches. Spring snowmelt was the dominant hydrological event in the year with peak flows an order of magnitude larger at the mouth and upper reaches than annual mean discharge. All three C‐Q shapes (positive, negative, and flat) were observed at all locations along the stream, with a higher proportion of the analytes showing significant relationships at the mouth than at the mid or upper flumes. At the mouth, positive (flushing) C‐Q shapes were observed for dissolved organic carbon and total suspended solids, whereas negative (dilution) C‐Q shapes were observed for most cations (Na+, Mg2+, Ca2+) and biologically cycled anions (NO3−, PO43−, SO42−). Most analytes displayed significant C‐Q relationships at the mouth, indicating that discharge is a significant driving factor controlling stream chemistry. However, the importance of discharge appeared to decrease moving upstream to the headwaters where more localized or temporally dynamic factors may become more important controls on stream solute patterns.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149221/1/hyp13416.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149221/2/hyp13416_am.pd

Development of forest structure and leaf area in secondary forests regenerating on abandoned pastures in Central Amazonia

The area of secondary forest (SF) regenerating from pastures is increasing in the Amazon basin; however, the return of forest and canopy structure following abandonment is not well understood. This study examined the development of leaf area index (LAI), canopy cover, aboveground biomass, stem density, diameter at breast height (DBH), and basal area ( BA) by growth form and diameter class for 10 SFs regenerating from abandoned pastures. Biomass accrual was tree dominated, constituting >= 94% of the total measured biomass in all forests abandoned >= 4 to 6 yr. Vine biomass increased with forest age, but its relative contribution to total biomass decreased with time. The forests were dominated by the tree Vismia spp. (> 50%). Tree stem density peaked after 6 to 8 yr ( 10 320 stems per hectare) before declining by 42% in the 12- to 14-yr-old SFs. Small-diameter tree stems in the 1-5-cm size class composed > 58% of the total stems for all forests. After 12 to 14 yr, there was no significant leaf area below 150-cm height. Leaf area return (LAI = 3.2 after 12 to 14 yr) relative to biomass was slower than literature-reported recovery following slash-and-burn, where LAI can reach primary forest levels ( LAI = 4 - 6) in 5 yr. After 12 to 14 yr, the colonizing vegetation returned some components of forest structure to values reported for primary forest. Basal area and LAI were 50% - 60%, canopy cover and stem density were nearly 100%, and the rapid tree-dominated biomass accrual was 25% - 50% of values reported for primary forest. Biomass accumulation may reach an asymptote earlier than expected because of even-aged, monospecific, untiered stand structure. The very slow leaf area accumulation relative to biomass and to reported values for recovery following slash-and-burn indicates a different canopy development pathway that warrants further investigation of causes ( e. g., nutrient limitations, competition) and effects on processes such as evapotranspiration and soil water uptake, which would influence long-term recovery rates and have regional implications

Sister telomeres rendered dysfunctional by persistent cohesion are fused by NHEJ

Telomeres protect chromosome ends from being viewed as double-strand breaks and from eliciting a DNA damage response. Deprotection of chromosome ends occurs when telomeres become critically short because of replicative attrition or inhibition of TRF2. In this study, we report a novel form of deprotection that occurs exclusively after DNA replication in S/G2 phase of the cell cycle. In cells deficient in the telomeric poly(adenosine diphosphate ribose) polymerase tankyrase 1, sister telomere resolution is blocked. Unexpectedly, cohered sister telomeres become deprotected and are inappropriately fused. In contrast to telomeres rendered dysfunctional by TRF2, which engage in chromatid fusions predominantly between chromatids from different chromosomes (Bailey, S.M., M.N. Cornforth, A. Kurimasa, D.J. Chen, and E.H. Goodwin. 2001. Science. 293:2462–2465; Smogorzewska, A., J. Karlseder, H. Holtgreve-Grez, A. Jauch, and T. de Lange. 2002. Curr. Biol. 12:1635–1644), telomeres rendered dysfunctional by tankyrase 1 engage in chromatid fusions almost exclusively between sister chromatids. We show that cohered sister telomeres are fused by DNA ligase IV–mediated nonhomologous end joining. These results demonstrate that the timely removal of sister telomere cohesion is essential for the formation of a protective structure at chromosome ends after DNA replication in S/G2 phase of the cell cycle

Positioning aquatic animals with acoustic transmitters

Geolocating aquatic animals with acoustic tags has been ongoing for decades, relying on the detection of acoustic signals at multiple receivers with known positions to calculate a 2D or 3D position, and ultimately recreate the path of an aquatic animal from detections at fixed stations.This method of underwater geolocation is evolving with new software and hardware options available to help investigators design studies and calculate positions using solvers based predominantly on time-difference-of-arrival and time-of-arrival.We provide an overview of the considerations necessary to implement positioning in aquatic acoustic telemetry studies, including how to design arrays of receivers, test performance, synchronize receiver clocks and calculate positions from the detection data. We additionally present some common positioning algorithms, including both the free open-source solvers and the 'black-box' methods provided by some manufacturers for calculating positions.This paper is the first to provide a comprehensive overview of methods and considerations for designing and implementing better positioning studies that will support users, and encourage further knowledge advances in aquatic systems

The international normalized ratio overestimates coagulopathy in patients after major hepatectomy

Abstract BACKGROUND: The International Normalized Ratio (INR) is commonly used to guide therapy after hepatectomy. We hypothesized that the use of thrombelastography (TEG) would demonstrate a decreased incidence of hypocoagulability in this patient population. METHODS: Seventy-eight patients were prospectively enrolled before undergoing hepatectomy. INR, TEG, and coagulation factors were drawn before incision, postoperatively, and on postoperative days 1, 3, and 5. RESULTS: Patients demonstrated an elevated INR at all postoperative time points. However, TEG demonstrated a decreased R value postoperatively, with subsequent normalization. Other TEG measurements were equivalent to preoperative values. All procoagulant factors save factor VIII decreased postoperatively, with a simultaneous decrease in protein C. CONCLUSIONS: TEG demonstrated a brief hypercoagulable state after major hepatectomy, with coagulation subsequently normalizing. The INR significantly overestimates hypocoagulability after hepatectomy and these data call into question current practices using the INR to guide therapy in this patient population. Ó 2014 Elsevier Inc. All rights reserved. Partial hepatectomy remains the treatment of choice for a wide range of both benign and malignant diseases of the liver. Following major hepatectomy, derangement of hepatic synthetic function has been well characterized, including impaired synthesis of serum clotting factors and regulatory proteins

Modeling plant competition with GAPS object-oriented dynamic simulation model

ABSTRACT framework, mention in passing an “arbiter ” module that Modeling interspecies competition is a natural application for dynamic simulation models of agricultural systems. We extended a dy-can partition resources among different crop models. We extended a dynamic soil–plant–atmosphere simunamic simulation model of the soil–plant–atmosphere system, GAPS, lation model, GAPS, to include the case where multiple to include the case where multiple plant species are growing in compe- plant species are growing in competition. The key innotition. The competition model was implemented as an object hierarchy vations of this work are as follows. that exchanges information with a crop model hierarchy by means of access procedures. Crop models, atmospheric procedures, and soil– plant water interface procedures required minimal change in order 1. The competition model is implemented as an ob-ject hierarchy, which exchanges information with to support the competition model. We implemented two competition the existing crop model hierarchy by means of acmodels: modified ALMANAC and winner-takes-all. The modified cess procedures

Temperature dependence of daily respiration and reaeration rates during baseflow conditions in a northeastern U.S. stream

Study region: Finger Lakes Region, New York, USA. Study focus: The relationship between stream temperature and daily respiration and reaeration rates was investigated from May 2015 – May 2016 for two sites, one in the headwaters and the other near the mouth of a net heterotrophic stream. Daily respiration and reaeration rates were calculated by applying the night time slope method to open-channel diel oxygen concentrations during baseflow conditions. New hydrological insights for the region: Reference values for activation energy (Ea) are presented that could be applicable to lower order streams in temperate climates receiving significant inputs from surface and subsurface flows. There was a sizeable difference in temperature sensitivity between upstream and downstream sites. Ecosystem respiration (ER) exhibited a strong Arrhenius temperature dependence with daily respiration rates of 0.5–9.5 g O2 m−2 d−1 (Ea = 0.61 eV) in the headwaters and 1.8–30.3 g O2 m−2 d−1 (Ea = 0.67 eV) at the downstream location where ER in the headwaters was less sensitive to temperature. Ea for both sites fell within the expected theoretical range for heterotrophic respiration in aquatic ecosystems. Temperature reaeration rate coefficients ranged from 1.011 to 1.020 at the headwaters and from 1.005 to 1.009 downstream suggesting that daily reaeration rates at the headwaters were more sensitive to temperature than the downstream location where reaeration was likely controlled by stream discharge and driven by turbulence. Keywords: Stream metabolism, Dissolved oxygen, Arrhenius kinetics, Gas transfer coefficient, Aquatic respiration, Baseflow, Lotic ecosystems, Nighttime slope metho

Yield response to climate, management, and genotype: a large-scale observational analysis to identify climate-adaptive crop management practices in high-input maize systems

Sustaining food security under climate conditions expected for the 21st century will require that existing crop production systems simultaneously increase both productivity and resiliency to warmer and more variable climate conditions. In this study, we analyzed observational rainfed maize ( Zea mays L.) yield data from major maize production areas of the US Corn Belt. These data included detailed information on crop management and genetics not typically available in observational studies, allowing us to better understand maize yield response to climate under variable management. Spatial variability in management variables across the study domain is coincident with spatial climate gradients. Regularized global and geographically weighted regression models were used to explore maize yield response to climate, management, genetics, and their interactions, while accounting for collinearity among them associated with corresponding scales of spatial variability. In contrast with recent analyses suggesting increased susceptibility to drought stress under higher plant populations in maize production, our analyses indicated that under moisture limitation, higher yields were achieved when high planting rates were coupled with delayed planting date. Maize genetic families that performed best with adequate moisture saw greater yield penalties under moisture limited conditions, while positive response to increased radiation was consistent among family lines. The magnitude of yield response to climate, management, and their interactions was also variable across the study domain, suggesting that information on crop management in spatial yield data can be used to better tailor local management practices to changes in yield potential resulting from agronomic advancements and changing local climate