Consequences of Buffelgrass Pasture Development for Primary Productivity,Perennial Plant Richness,and Vegetation Structure in the Drylands of Sonora,Mexico

Abstract: In large parts of northern Mexico native plant communities are being converted to non‐native buffelgrass (Pennisetum ciliare) pastures, and this conversion could fundamentally alter primary productivity and species richness. In Sonora, Mexico land conversion is occurring at a regional scale along a rainfall‐driven gradient of primary productivity, across which native plant communities transition from desert scrub to thorn scrub. We used a paired sampling design to compare a satellite‐derived index of primary productivity, richness of perennial plant species, and canopy‐height profiles of native plant communities with buffelgrass pastures. We sampled species richness across a gradient of primary productivity in desert scrub and thorn scrub vegetation to examine the influence of site productivity on the outcomes of land conversion. We also examined the influence of pasture age on species richness of perennial plants. Index values of primary productivity were lower in buffelgrass pastures than in native vegetation, which suggests a reduction in primary productivity. Land conversion reduced species richness by approximately 50% at local and regional scales, reduced tree and shrub cover by 78%, and reduced canopy height. Land conversion disproportionately reduced shrub species richness, which reflects the common practice among Sonoran ranchers of conserving certain tree and cactus species. Site productivity did not affect the outcomes of land conversion. The age of a buffelgrass pasture was unrelated to species richness within the pasture, which suggests that passive recovery of species richness to preconversion levels is unlikely. Our findings demonstrate that land conversion can result in large losses of plant species richness at local and regional scales and in substantial changes to primary productivity and vegetation structure, which casts doubt on the feasibility of restoring native plant communities without active intervention on the part of land managers.     

Karst Hydrological Processes and Grey System Model1

Hao, Yonghong, Jiaojuan Zhao, Huamin Li, Bibo Cao, Zhongtang Li, and Tian‐Chyi J. Yeh, 2012. Karst Hydrological Processes and Grey System Model. Journal of the American Water Resources Association (JAWRA) 48(4): 656‐666. DOI: 10.1111/j.1752‐1688.2012.00640.x Abstract: The karst hydrological processes are the response of karst groundwater system to precipitation. This study provided a concept model of karst hydrological processes. The hydraulic response time of spring discharge to precipitation includes the time that precipitation penetrates through the vadose zone, and the subsequent groundwater pressure wave propagates to a spring outlet. Due to heterogeneities in karst aquifers, the hydraulic response time is different in different areas. By using grey system theory, we proposed a karst hydrological model that offers a calculation of hydraulic response time, and a response model of spring discharge to precipitation. Then, we applied the models to the Liulin Springs Basin, China. In the south part of the Liulin Springs Basin, where large fields of carbonate rocks outcrop with intensive karstification, the hydraulic response time is one year. In the north, where the Ordovician karst aquifer is covered by Quaternary loess sediments, the response time is seven years. The grey system GM(1,3) response model of spring discharge to precipitation was applied in consideration of the hydraulic response time. The model calibration showed that the average error was 6.55%, and validation showed that the average error was 12.19%.     

Neural Network Input Selection for Hydrological Forecasting Affected by Snowmelt1

Abstract: Snowmelt largely affects runoff in watersheds in Nordic countries. Neural networks (NN) are particularly attractive for streamflow forecasting whereas they rely at least on daily streamflow and precipitation observations. The selection of pertinent model inputs is a major concern in NNs implementation. This study investigates performance of auxiliary NN inputs that allow short‐term streamflow forecasting without resorting to a deterministic snowmelt routine. A case study is presented for the Rivière des Anglais watershed (700 km²) located in Southern Québec, Canada. Streamflow (Q), precipitations (rain R and snow S, or total P), temperature (T) and snow lying (A) observations, combined with climatic and snowmelt proxy data, including snowmelt flow (Q_SM) obtained from a deterministic model, were tested. NN implemented with antecedent Q and R produced the largest gains in performance. Introducing increments of A and T to the NNs further improved the performance. Long‐term averages, seasonal data, and Q_SM failed to improve the networks.     

Tributyltin distribution and producing androgenic activity in water,sediment, and fish muscle

This study investigated the concentrations of Tributyltin (TBT) in water, sediment, and fish muscle samples taken from Kaohsiung Harbor and Kaoping River estuary, Taiwan. TBT concentrations in water and sediment samples ranged from less than 18.5 to 34.1 ng Sn L^?1 and from 2.44 to 29.7 ng Sn g^?1 weight per weight (w/w), respectively. Concentrations in the TBT‐contaminated fish muscle samples ranged from 10.8 to 79.6 ng Sn g^?1 w/w. The TBT concentrations in fish muscle were higher than those in water and sediment samples. The fish muscle/water TBT bioconcentration factor (BCF) ranged from 590 to 3363 L kg^?1. Additionally, the water samples were assessed for androgenic activity with an MCF7‐AR1 human breast cancer cell line. The androgenic activity ranged from 0.94 to 3.1 ng‐dihydrotestosterone per litre water (ng‐DHT L^?1). Higher concentrations of TBT in water and sediment samples occurred in the dry season, but the androgenic activity had higher values in the rainy season.     

Gastrointestinal Bacterial Transmission among Humans,Mountain Gorillas,and Livestock in Bwindi Impenetrable National Park,Uganda

Abstract: Habitat overlap can increase the risks of anthroponotic and zoonotic pathogen transmission between humans, livestock, and wild apes. We collected Escherichia coli bacteria from humans, livestock, and mountain gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda, from May to August 2005 to examine whether habitat overlap influences rates and patterns of pathogen transmission between humans and apes and whether livestock might facilitate transmission. We genotyped 496 E. coli isolates with repetitive extragenic palindromic polymerase chain reaction fingerprinting and measured susceptibility to 11 antibiotics with the disc‐diffusion method. We conducted population genetic analyses to examine genetic differences among populations of bacteria from different hosts and locations. Gorilla populations that overlapped in their use of habitat at high rates with people and livestock harbored E. coli that were genetically similar to E. coli from those people and livestock, whereas E. coli from gorillas that did not overlap in their use of habitats with people and livestock were more distantly related to human or livestock bacteria. Thirty‐five percent of isolates from humans, 27% of isolates from livestock, and 17% of isolates from gorillas were clinically resistant to at least one antibiotic used by local people, and the proportion of individual gorillas harboring resistant isolates declined across populations in proportion to decreasing degrees of habitat overlap with humans. These patterns of genetic similarity and antibiotic resistance among E. coli from populations of apes, humans, and livestock indicate that habitat overlap between species affects the dynamics of gastrointestinal bacterial transmission, perhaps through domestic animal intermediates and the physical environment. Limiting such transmission would benefit human and domestic animal health and ape conservation.     

VELOCITY AND CONCENTRATION DISTRIBUTIONS OF SEDIMENT‐LADEN OPEN CHANNEL FLOW1

ABSTRACT: A mathematical model to predict both velocity and concentration distributions for sediment‐laden open channel flow is developed. Velocity profiles are derived by theoretical analysis and numerical method. Logarithmic law and semi‐empirical wake function concept are not adopted. An empirical equation for the ratio of sediment exchange and fluid diffusion coefficients is considered to solve the diffusion equation for suspended‐sediment concentration profiles. Four sets of experimental data from previous researchers are compared to numerical calculation. In the engineering applications, velocity and concentration profiles of sediment‐laden flow can be predicted simultaneously by the present model with the measured velocity and sediment‐concentration at reference level.     

Determining gestational age using genome methylation profile: A novel approach for fetal medicine

Gestational age determination by traditional tools (last menstrual period, ultrasonography measurements and Ballard Maturational Assessment in newborns) has major limitations and therefore there is a need to find different approaches. In this study, we looked for a molecular marker that can be used to determine the accurate gestational age of the newborn. To this end, we performed reduced representation bisulfite sequencing (RRBS) on 41 cord blood and matching placenta samples from women between 25 and 40 weeks of gestation and generated an epigenetic clock based on the methylation level at different loci in the genome. We identified a set of 332 differentially methylated regions (DMRs) that undergo demethylation in late gestational age in cord blood cells and can predict the gestational age (r = −.7, P = 2E-05). Once the set of 411 DMRs that undergo de novo methylation in late gestational age was used in combination with the first set, it generated a more accurate clock (R = .77, P = 1.87E-05). We have compared gestational age determined by Ballard score assessment with our epigenetic clock and found high concordance. Taken together, this study demonstrates that DNA methylation can accurately predict gestational age and thus may serve as a good clinical predictor.     

WATER SUPPLY EVALUATION OF TAIWAN'S SILICON VALLEY1

ABSTRACT: The objective of this paper is to examine a deficit in water for the Hsinchu area, the location of Taiwan's “Silicon Valley.” The methods suggested in this paper to diagnose water shortage problems are simple and practical. The results show that Hsinchu is in an area without sufficient water to meet demand for domestic and industrial uses. Until the completion of the Baoshan II Reservoir in 2006, the most feasible options for the Taiwan Water Supply Corporation to offset the water deficiency in Hsinchu City over the next five years are: (a) to obtain water gratuitously from the southern Yungheshan Reservoir; (b) to import additional water at an extra charge from other sources such as the northern Shihmen Reservoir and the agricultural sector; and (c) to conduct a comprehensive water conservation program at the Hsinchu Science‐based Industrial Park.