Geology topics

J.L. Moore

Publications and source records attributed to J.L. Moore.

4 recordsLinked to original sources

USGS2020

Climate and local environment structure asynchrony and the stability of primary production in grasslands

Aim Climate variability threatens to destabilize production in many ecosystems. Asynchronous species dynamics may buffer against such variability when a decrease in performance by some species is offset by an increase in performance of others. However, high climatic variability can eliminate species through stochastic extinctions or cause similar stress responses among species that reduce buffering. Local conditions, such as soil nutrients, can also alter production stability directly or by influencing asynchrony. We test these hypotheses using a globally distributed sampling experiment. Location Grasslands in North America, Europe and Australia. Time period Annual surveys over 5 year intervals occurring between 2007 and 2014. Major taxa studied Herbaceous plants. Methods We sampled annually the per species cover and aboveground community biomass [net primary productivity (NPP)], plus soil chemical properties, in 29 grasslands. We tested how soil conditions, combined with variability in precipitation and temperature, affect species richness, asynchrony and temporal stability of primary productivity. We used bivariate relationships and structural equation modelling to examine proximate and ultimate relationships. Results Climate variability strongly predicted asynchrony, whereas NPP stability was more related to soil conditions. Species richness was structured by both climate variability and soils and, in turn, increased asynchrony. Variability in temperature and precipitation caused a unimodal asynchrony response, with asynchrony being lowest at low and high climate variability. Climate impacted stability indirectly, through its effect on asynchrony, with stability increasing at higher asynchrony owing to lower inter‐annual variability in NPP. Soil conditions had no detectable effect on asynchrony but increased stability by increasing the mean NPP, especially when soil organic matter was high. Main conclusions We found globally consistent evidence that climate modulates species asynchrony but that the direct effect on stability is low relative to local soil conditions. Nonetheless, our observed unimodal responses to variability in temperature and precipitation suggest asynchrony thresholds, beyond which there are detectable destabilizing impacts of climate on primary productivity.

Global Ecology and Biogeography↗

USGS1996

The efficacy of protoporphyrin as a predictive biomarker for lead exposure in canvasback ducks: effect of sample storage time

We used 363 blood samples collected from wild canvasback dueks ( Aythya valisineria ) at Catahoula Lake, Louisiana, U.S.A. to evaluate the effect of sample storage time on the efficacy of erythrocytic protoporphyrin as an indicator of lead exposure. The protoporphyrin concentration of each sample was determined by hematofluorometry within 5 min of blood collection and after refrigeration at 4 °C for 24 and 48 h. All samples were analyzed for lead by atomic absorption spectrophotometry. Based on a blood lead concentration of ≥0.2 ppm wet weight as positive evidence for lead exposure, the protoporphyrin technique resulted in overall error rates of 29%, 20%, and 19% and false negative error rates of 47%, 29% and 25% when hematofluorometric determinations were made on blood at 5 min, 24 h, and 48 h, respectively. False positive error rates were less than 10% for all three measurement times. The accuracy of the 24-h erythrocytic protoporphyrin classification of blood samples as positive or negative for lead exposure was significantly greater than the 5-min classification, but no improvement in accuracy was gained when samples were tested at 48 h. The false negative errors were probably due, at least in part, to the lag time between lead exposure and the increase of blood protoporphyrin concentrations. False negatives resulted in an underestimation of the true number of canvasbacks exposed to lead, indicating that hematofluorometry provides a conservative estimate of lead exposure.

Louisiana↗

USGS1994

Distribution and status of submerged vegetation in estuaries of the upper Texas coast

Composition and biomass of beds of submerged aquatic vegetation (SAV) in estuaries along the upper Texas coast were examined from bottom core and rake samples taken along 72 line transects during July–August 1987. Substrate composition, salinity, water depth, and water clarity were also measured at each sample station. Halodule wrightii was the dominant species of SAV meadows (69% occurrence), followed by Ruppia maritima (36%). Najas guadalupensis and Vallisneria americana were only found in the shallow (<60 cm), oligohaline (<10 ppt) waters of Trinity Bay. Halophila engelmannii and Thalassia testudinum were only found in the deeper (35–110 cm) euhaline waters (30–40 ppt) of Christmas and Matagorda Bays. H. wrightii and R. maritima occurred across the greatest depth and salinity spectra, with R. maritima more prominent in shallower (<90 cm) mixohaline waters (10–30 ppt) and H. wrightii more prominent in euhaline waters (30–40 ppt). Beds of SAV were more extensive and had greater biomass along south shorelines compared to north shorelines (P<0.045), and depth to which vegetation grew was positively correlated with water clarity (r=0.927, P<0.001). The correlations of water depth, salinity, and water clarity with variation in SAV species composition and distribution suggest that abiotic tolerances documented by previous experimental studies are major factors influencing field distributions. Comparisons with similar field data from the early 1970s corroborate the reported decrease in SAV in the Galveston Bay complex and suggest a slight increase in the Matagorda Bay complex. Decline of SAV in the Galveston Bay complex coincided with major shorefront development and a decline in numbers of wintering redhead ducks Aythya americana . Protection of shorelines of upper coast estuaries is vital to maintaining SAV resources and the dependent fauna. Where possible, barrier island preserves should be established adjacent to beds of-SAV and development restrictions implemented to reduce impacts.

Texas↗

USGS1992

Food preferences of spring-migrating blue-winged teal in southwestern Louisiana

We studied effects of pair status, molt intensity, and year on food selection by migrating male blue-winged teal (Anas discors) in southwestern Louisiana during springs 1990 and 1991. Diets consisted primarily of animal foods; but plant material, consisting mostly of seeds, comprised as much as 44%. There was no difference in animal food consumption by paired and unpaired males; however, the proportion of animal material in the male diet was greater in 1990 than in 1991. Animal food consumption was not positively correlated with mean molt intensity. Food preferences of paired and unpaired males were similar in both years. Animal foods, especially benthos and organisms associated with vegetative substrates, were preferred to seeds and freeswimming invertebrates. We recommend that habitat management for spring-migrating blue-winged teal focus on production of invertebrates, especially long-lived forms such as dragonflies, hemipterans (except water boatmen), midges, and other dipterans.

Louisiana↗