Antennal electrophysiological responses of the giant swallowtail butterfly, Papilio cresphontes, to the essential oils of Zanthoxylum clava-herculis and related plants

We used the electroantennogram (EAG) technique to compare the antennal sensitivity of both sexes of the giant swallowtail butterfly, Papilio cresphontes to four doses (1, 10, 100, and 1,000 μg) of the leaf essential oils of Zanthoxylum clava-herculis and Ptelea trifoliata (key host plants) and Sassafras albidum (a marginal or non-host plant). The main hypothesis tested was that P. cresphontes will show greater olfactory sensitivity to volatiles of the key host plants than to volatiles of the marginal host plant, in particular at low doses. At the lower doses, extract of the key host plant, Z. clava-herculis elicited greater EAG responses in both sexes than extracts of the remaining two plants. At higher doses, however, extracts of P. trifoliata and S. albidum elicited greater EAG responses than extract of Z. clava-herculis. These results partly support our hypothesis and may suggest that Z. clava-herculis is a more preferred host plant of P. cresphontes than P. trifoliata. In general, female butterflies showed greater EAG responses than males to the three plant extracts at the higher doses. Preliminary coupled gas chromatography-electroantennogram (GC-EAD) tests revealed four components each from Z. clava-herculis and P. trifoliata (three peaks common to both extracts) and seven from S. albidum (one shared with Z. clava-herculis) which elicited GC-EAD activity in P. cresphontes females, but the peaks were un-indentified because most were detected in trace amounts. In addition, the chemical composition of the leaf essential oil of Z. clava-herculis was analyzed by GC–MS. The leaf essential oils consisted of 25 components, largely menthane monoterpenoids, dominated by limonene and 1,8-cineole, but neither of the two major components elicited significant GC-EAD response in P. cresphontes. These results are discussed in relation to host-plant selection in P. cresphontes.     

Rarity of Organisms in the Sand Pine Scrub Habitat of Florida

Naturalists conceive of "rare" organisms as those narrow in geographic range, restricted to few habitats, or small in population sizes. Because rare organisms may be rare in a variety of ways, a particular conservation strategy that purports to protect them may not do so effectively in all cases; therefore, categorization of rarity in advance could help ensure that the chosen strategy has a reasonable chance of success in a particular case. We placed plants, amphibians, and reptiles resident in the Sand Pine scrub habitat of Florida into categories of rarity. Determining if and in what way a particular organism is rare proved difficult, because the process requires exact specification of what is meant by "narrow,""restricted," and "small." Furthermore, the process requires choice of a scale for judging rarity and relies upon data that are likely to be of variable availability and reliability. We categorized rarity by several schemes, and they produced distributions of taxa among categories of rarity that largely were similar to one another but that diverged in telling ways. The distributions of taxa among categories of rarity produced by any scheme were different for scrub plants than for scrub amphibians and reptiles. Likewise, these distributions were different than those produced by previously published studies of rarity. We found that the results of our categorization schemes did not match particularly well with the official listing of scrub organisms as endangered or potentially endangered.     

Assessing the Effects of Natural and Anthropogenic Stressors in the Potomac Estuary: Implications for Long-Term Monitoring

Ecological conditions in the Potomac Estuary are affected by a variety of natural and anthropogenic stressors. Natural climatic factors combined with anthropogenic activities affect fluxes of material through Potomac River watersheds and cause changes in ecological conditions in the Potomac Estuary. A basic premise of this ongoing study is that effects of anthropogenic and natural stressors can be distinguished. The investigation involves: 1) analysis of existing data using time series methods, 2) retrospective modeling to link the response of estuarine water quality to changes in stressors, and 3) new measurements on sediment cores from the Potomac Estuary. Estuarine effects being considered include changes in the distribution and abundance of chlorophyll a, diatoms, dinoflagellates, ostracods, submerged aquatic vegetation, benthic fauna, dissolved oxygen, and foraminifera. Since current conditions may be due to the accumulation of effects over many years, our research considers variability and changes during the past century in the context of long-term changes during the past 500 years. The availability of large data sets from the past century, long-term information on variability in precipitation from tree ring data from the past 300 years, and paleoecological studies by other investigators in the Potomac Estuary and main stem of Chesapeake Bay make the Potomac Estuary an ideal place to develop methods to distinguish between effects of natural and anthropogenic stressors in estuaries, in the context of a varying, and perhaps changing, climate.     

Timber harvest calculations on a National Forest: A case study

Harvest calculations determine sawtimber flows from public lands and are closely scruntinized by a wide spectrum of forest users. This study examines the reliability of harvest calculations on a single national forest in New Mexico Forest Service determinations of an array of variables were reviewed and evaluated. The study revealed a lack of precision in Forest Service adherence to self-imposed procedural standards governing the calculation process. Timber sales have taken place on lands where such standards prohibit harvesting and these lands have been included in annual harvest calculations. Assumptions required by a mathematical model used by the Forest Service in calculating the harvest were not followed in the subsequent implementation of the harvest level. These factors suggest that the Forest Service could have significantly over-stated annual harvest rate for the first decade. Opportunities exist to improve the calculation, and benefits realized may greatly exceed additional costs of implementation     

Potential nitrogen enrichment of soil and surface water by atmospheric ammonia sorption in intensive livestock production areas

Elevated atmospheric NH₃ levels near intensive livestock operations can add significant N to local agroecosystems. In this study, the potential atmospheric NH₃ sorbed by soil and water was assessed over a 2-year period starting October 2000 in an intensive livestock production area in southern Alberta, Canada. Fifty-two uneven grid sampling sites were selected in the 53,905 ha study area. The sorption rate of atmospheric NH₃ was estimated weekly by exposing distilled water and air-dried soil samples to the atmosphere at the sampling sites. The increases in NH₄–N content in the samples after 1-week exposure was regarded as an index of the atmospheric NH₃ sorbed for that week. The NH₃ sorption rates were highly variable across the 52 sites, with water ranging from 4 to 125 kg ha⁻¹ year⁻¹ with a mean of 22 kg N ha⁻¹ year⁻¹ and soil from 5 to 84 kg N ha⁻¹ year⁻¹ with a mean of 20 kg N ha⁻¹ year⁻¹. Considerable variation in NH₃–N sorption across the study area reflects the effects of size, direction (upwind or downwind) and proximity of nearby livestock operations or other NH₃ sources and operators’ activities around the sampling sites. The NH₃ sorption rate at each site also varied considerably in response to weather conditions. The high rate of NH₃ input poses a direct risk of surface water eutrophication in intensive livestock operation areas. If fertilizer recommendations are not reduced to account for NH₃ sorption by soil, excess N may also contribute to eutrophication through runoff and leaching.     

Modeling sorbent injection for mercury control in baghouse filters: I--model development and sensitivity analysis

A two-stage mathematical model for Hg removal using powdered activated carbon injection upstream of a baghouse filter was developed, with the first stage accounting for removal in the ductwork and the second stage accounting for additional removal caused by the retention of carbon particles on the filter. The model shows that removal in the ductwork is minimal, and the additional carbon detention time from the entrapment of the carbon particles in the fabric filter enhances the Hg removal from the gas phase. A sensitivity analysis on the model shows that Hg removal is dependent on the isotherm parameters, the carbon pore radius and tortuosity, the C/Hg ratio, and the carbon particle radius.