INCORPORATING NATURAL VARIABILITY,UNCERTAINTY, AND RISK INTO WATER QUALITY EVALUATIONS USING DURATION CURVES1

ABSTRACT: Quantifying natural variability, uncertainty, and risk with minimal data is one of the greatest challenges facing those engaged in water quality evaluations, such as development of total maximum daily loads (TMDL), because of regulatory, natural, and analytical constraints. Quantification of uncertainty and variability in natural systems is illustrated using duration curves (DCs), plots that illustrate the percent of time that a particular flow rate (FDC), concentration (CDC), or load rate (LDC; “TMDL”) is exceeded, and are constructed using simple derived distributions. Duration curves require different construction methods and interpretations, depending on whether there is a statistically significant correlation between concentration (C) and flow (Q), and on the sign of the C‐Q regression slope (positive or negative). Flow DCs computed from annual runoff data vary compared with an FDC developed using all data. Percent exceedance for DCs can correspond to risk; however, DCs are not composed of independent quantities. Confidence intervals of data about a regression line can be used to develop confidence limits for the CDC and LDC. An alternate expression to a fixed TMDL is suggested as the risk of a load rate being exceeded and lying between confidence limits. Averages over partial ranges of DCs are also suggested as an alternative expression of TMDLs. DCs can be used to quantify watershed response in terms of changes in exceedances, concentrations, and load rates after implementation of best management practices.     

ASSEMBLY OF MAP‐BASED STREAM NARRATIVES TO FACILITATE STAKEHOLDER INVOLVEMENT IN WATERSHED MANAGEMENT1

ABSTRACT: Watershed stewardship activities throughout North America have evolved into a process that requires more involvement in planning and decision making by community stakeholders. Active involvement of all stakeholders in the process of watershed stewardship is dependent on effective exchange of information among participants, and active involvement of a wide range of stakeholders from “communities of place” as well as those from “communities of interest.” We developed a map‐based stream narrative tool as a means to: (a) assemble a wealth of incompletely documented, “traditional” ecological or natural history observations for rivers or streams; and (b) promote a higher level of active involvement by community stakeholders in contributing to information‐based, watershed management. Creation of stream narratives is intended for use as a tool to actively engage local stakeholders in the development of a more comprehensive information system to improve management for multiple stewardship objectives in watersheds. Completion of map‐based stream narrative atlases provides a valuable supplement to other independent efforts to assemble observations and knowledge about land‐based natural resources covering entire watersheds. We are confident that completion of stream narrative projects will make a valuable addition to the information and decision making tools that are currently available to the public and resource agencies interested in advancing the cause of community‐based approaches to watershed and ecosystem management.     

Phenological tracking enables positive species responses to climate change

Earlier spring phenology observed in many plant species in recent decades provides compelling evidence that species are already responding to the rising global temperatures associated with anthropogenic climate change. There is great variability among species, however, in their phenological sensitivity to temperature. Species that do not phenologically "track" climate change may be at a disadvantage if their growth becomes limited by missed interactions with mutualists, or a shorter growing season relative to earlier-active competitors. Here, we set out to test the hypothesis that phenological sensitivity could be used to predict species performance in a warming climate, by synthesizing results across terrestrial warming experiments. We assembled data for 57 species across 24 studies where flowering or vegetative phenology was matched with a measure of species performance. Performance metrics included biomass, percent cover, number of flowers, or individual growth. We found that species that advanced their phenology with warming also increased their performance, whereas those that did not advance tended to decline in performance with warming. This indicates that species that cannot phenologically "track" climate may be at increased risk with future climate change, and it suggests that phenological monitoring may provide an important tool for setting future conservation priorities.     

Scale-dependent responses of plant biodiversity to nitrogen enrichment

Experimental studies demonstrating that nitrogen (N) enrichment reduces plant diversity within individual plots have led to the conclusion that anthropogenic N enrichment is a threat to global biodiversity. These conclusions overlook the influence of spatial scale, however, as N enrichment may alter beta diversity (i.e., how similar plots are in their species composition), which would likely alter the degree to which N-induced changes in diversity within localities translate to changes in diversity at larger scales that are relevant to policy and management. Currently, it is unclear how N enrichment affects biodiversity at scales larger than a small plot. We synthesized data from 18 N-enrichment experiments across North America to examine the effects of N enrichment on plant species diversity at three spatial scales: small (within plots), intermediate (among plots), and large (within and among plots). We found that N enrichment reduced plant diversity within plots by an average of 25% (ranging from a reduction of 61% to an increase of 5%) and frequently enhanced beta diversity. The extent to which N enrichment altered beta diversity, however, varied substantially among sites (from a 22% increase to an 18% reduction) and was contingent on site productivity. Specifically, N enrichment enhanced beta diversity at low-productivity sites but reduced beta diversity at high-productivity sites. N-induced changes in beta diversity generally reduced the extent of species loss at larger scales to an average of 22% (ranging from a reduction of 54% to an increase of 18%). Our results demonstrate that N enrichment often reduces biodiversity at both local and regional scales, but that a focus on the effects of N enrichment on biodiversity at small spatial scales may often overestimate (and sometimes underestimate) declines in regional biodiversity by failing to recognize the effects of N on beta diversity.     

Histological,chemical, and morphological reexamination of the “heart” of a small Late Cretaceous <Emphasis Type="BoldItalic">Thescelosaurus</Emphasis>

A three-dimensional, iron-cemented structure found in the anterior thoracic cavity of articulated Thescelosaurus skeletal remains was hypothesized to be the fossilized remains of the animal’s four-chambered heart. This was important because the finding could be interpreted to support a hypothesis that non-avian dinosaurs were endothermic. Mammals and birds, the only extant organisms with four-chambered hearts and single aortae, are endotherms. The hypothesis that this Thescelosaurus has a preserved heart was controversial, and therefore, we reexamined it using higher-resolution computed tomography, paleohistological examination, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy. This suite of analyses allows for detailed morphological and chemical examination beyond what was provided in the original work. Neither the more detailed examination of the gross morphology and orientation of the thoracic “heart” nor the microstructural studies supported the hypothesis that the structure was a heart. The more advanced computed tomography showed the same three areas of low density as the earlier studies with no evidence of additional low-density areas as might be expected from examinations of an ex situ ostrich heart. Microstructural examination of a fragment taken from the “heart” was consistent with cemented sand grains, and no chemical signal consistent with a biological origin was detected. However, small patches of cell-like microstructures were preserved in the sandstone matrix of the thoracic structure. A possible biological origin for these microstructures is the focus of ongoing investigation.     

Developing Nutrient Criteria for Streams: An Evaluation of the Frequency Distribution Method1

Abstract: The U.S. Environmental Protection Agency recommends two statistical methods to States and Tribes for developing nutrient criteria. One establishes a criterion as the 75th percentile of a reference‐population frequency distribution, the other uses the 25th percentile of a general‐population distribution; the U.S. Environmental Protection Agency suggests either method results in similar criteria. To evaluate each method, the Montana Department of Environmental Quality (MT DEQ) assembled data from STORET and other sources to create a nutrient general population. MT DEQ’s reference‐stream project provided reference population data. Data were partitioned by ecoregions, and by seasons (winter, runoff, and growing) defined for the project. For each ecoregion and season, nutrient concentrations at the 75th percentile of the reference population were matched to their corresponding concentrations in the general population. Additionally, nutrient concentrations from five regional scientific studies were matched to their corresponding reference population concentrations; each study linked nutrients to impacts on water uses. Reference‐to‐general population matches were highly variable between ecoregions, as nutrients at the 75th percentile of reference corresponded to percentiles ranging from the 4th to the 97th of the general population. In contrast, case studies‐to‐reference matches were more consistent, matching on average to the 86th percentile of reference, with a coefficient of variation of 13%.     

采用大体积进样提高水样中农药检测的灵敏度

正质谱技术的进步,使得分析方法的检测限不断降低,推动了许多有关环境和食品中痕量污染物的研究.通常情况下,亚ppb级的污染物水平分析,首选串联四极杆质谱.使用WatersXevoG2-S QTof可轻松实现对10-9级别的已知和未知化合物的筛查,如果增大样品进样体积,还可进一步提高灵敏度.而仅依靠MS/MS,是无法得到未知物或大量污染物的分析结果的.结合Xevo G2-S QTof的高精确质量数准确度(3×10-6)在低浓度水平下进行筛查实验,对许多环境分析     

Generating a geospatial database of U.S. regional feedstock production for use in evaluating the environmental footprint of biofuels

The potential environmental effects of increased U.S. biofuel production often vary depending upon the location and type of land used to produce biofuel feedstocks. However, complete, annual data are generally lacking regarding feedstock production by specific location. Corn is the dominant biofuel feedstock in the U.S., so here we present methods for estimating where bioethanol corn feedstock is grown annually and how much is used by U.S. ethanol biorefineries. We use geospatial software and publicly available data to map locations of biorefineries, estimate their corn feedstock requirements, and estimate the feedstock production locations and quantities. We combined these data and estimates into a Bioethanol Feedstock Geospatial Database (BFGD) for years 2005–2010. We evaluated the performance of the methods by assessing how well the feedstock geospatial model matched our estimates of locally-sourced feedstock demand. On average, the model met approximately 89 percent of the total estimated local feedstock demand across the studied years—within approximately 25-to-40 kilometers of the biorefinery in the majority of cases. We anticipate that these methods could be used for other years and feedstocks, and can be subsequently applied to estimate the environmental footprint of feedstock production.

Implications: Methods used to develop the Bioethanol Feedstock Geospatial Database (BFGD) provide a means of estimating the amount and location of U.S. corn harvested for use as U.S. bioethanol feedstock. Such estimates of geospatial feedstock production may be used to evaluate environmental impacts of bioethanol production and to identify conservation priorities. The BFGD is available for 2005–2010, and the methods may be applied to additional years, locations, and potentially other biofuels and feedstocks.     

Gastropod herbivory in response to elevated CO2 and N addition impacts plant community composition

In this study, the influence of elevated carbon dioxide (CO2) and nitrogen (N) deposition on gastropod herbivory was investigated for six annual species in a California annual grassland community. These experimentally simulated global changes increased availability of important resources for plant growth, leading to the hypothesis that species with the most positive growth and foliar nutrient responses would experience the greatest increase in herbivory. Counter to the expectations, shifts in tissue N and growth rates caused by N deposition did not predict shifts in herbivore consumption rates. N deposition increased seedling N concentrations and growth rates but did not increase herbivore consumption overall, or for any individual species. Elevated CO2 did not influence growth rates nor have a statistically significant influence on seedling N concentrations. Elevated CO2 at ambient N levels caused a decline in the number of seedlings consumed, but the interaction between CO2 and N addition differed among species. The results of this study indicate that shifting patterns of herbivory will likely influence species composition as environmental conditions change in the future; however, a simple trade-off between shifting growth rates and palatability is not evident.