Effects of dormant season soil flooding and soil temperature on pin oak (Quercus palustris) seedlings

Bottomland forests are the dominant forest cover along the Mississippi Alluvial Valley. Changes in land use and hydrologic regimes have reduced the area of bottomland forest, putting pressure on the remaining area to meet multiple objectives. To maintain migratory waterfowl habitat, some forests are managed as greentree reservoirs and artificially flooded during the fall and winter. Red oaks are a desirable component of these forests for their acorn production, but oak decline and inadequate recruitment pose problems for maintaining quality habitat. Artificial flooding regimes may be a driving factor in oak decline, as flood timing and duration may be outside of historic conditions. Previous studies have shown growing season floods can inhibit root growth, but the impacts of dormant season flooding are not as well studied. We conducted a greenhouse study to determine how winter flooding at different soil temperatures affects the growth and development of Quercus palustris (pin oak) seedlings. We examined the effects of soil temperature and dormant season flooding on Q. palustris seedlings using insulated water baths at 5, 10, and 15 degrees C. Half of the seedlings received soil flooding for 60 days from January to March, after which floodwater was drained for the remainder of the study. Seedlings were harvested before, during, and after flooding. Root length was determined using scanned images and WinRHIZO (Regent Instruments, Inc), after which samples were oven-dried to determine mass. During soil flooding, root mass was significantly less in flooded seedlings than those that were not flooded. However, following drainage this difference was no longer present. By the end of the experiment, seedlings that received flooding exhibited greater lateral root mass and length than those that had not been flooded. Flooding had minor positive impacts on aboveground variables, such as increased stem area, but did not significantly impact aboveground seedling biomass. These findings suggest that Q. palustris may experience temporary stress during dormant season flooding but can recover without lasting effects. While these results seem promising for current greentree reservoir management practices, care should be taken in applying them to field conditions.Includes bibliographical references

Effect of aging on the physical, chemical and dielectric properties of dodecylbenzene

High voltage transformers and cables form integral parts of the electrical power distribution network and therefore their reliable operation is crucial to preventing costly outages. A liquid dielectric, typically mineral oil, is used in transformers whilst dodecylbenzene is gradually replacing mineral oil in paper/oil cable systems. As such, the oil serves as a convenient medium for sampling to assess plant health. In the current investigation, samples of dodecylbenzene cable oil were aged at 135 ºC under conditions where the oxygen diffusion into the oil was deliberately limited. The resulting aged samples were subjected to a battery of tests to determine changes in their physical, chemical and dielectric properties. Aging resulted in yellowing, oxidation, increased water content, increased dielectric loss, increased electrical conductivity and reduced electrical breakdown strength. Copper accelerated the aging process resulting in the formation of an insoluble precipitate; however, the inclusion of this material did not affect the electrical properties of the oil indicating that it is non-polar in nature. Instead, the deterioration of the dielectric properties was found to be correlated with the production of small polar molecular compounds, which remain dissolved within the oil, such as water, alcohols, ketones, carboxylic acids and aldehydes

Water quality improvements offset the climatic debt for stream macroinvertebrates over twenty years

Many species are accumulating climatic debt as they fail to keep pace with increasing global temperatures. In theory, concomitant decreases in other stressors (e.g. pollution, fragmentation) could offset some warming effects, paying climatic debt with accrued environmental credit. This process may be occurring in many western European rivers. We fit a Markov chain model to ~20,000 macroinvertebrate samples from England and Wales, and demonstrate that despite large temperature increases 1991–2011, macroinvertebrate communities remained close to their predicted equilibrium with environmental conditions. Using a novel analysis of multiple stressors, an accumulated climatic debt of 0.64 (±0.13 standard error) °C of warming was paid by a water-quality credit equivalent to 0.89 (±0.04)°C of cooling. Although there is finite scope for mitigating additional climate warming in this way, water quality improvements appear to have offset recent temperature increases, and the concept of environmental credit may be a useful tool for communicating climate offsetting

Aging behaviour of dodecylbenzene in the presence of copper and dibenzyl disulfide (DBDS)

Copper sulfide deposition remains a serious issue in high voltage power transformers and can result in equipment failure. In order to understand the chemistry of this process, dodecylbenzene was used as a model oil system. Copper and dibenzyl disulfide (DBDS) were added in controlled amounts and accelerated aging was then performed. It was found that copper sulfide (CuxS) could be formed (i.e. the included copper sheets were blackened) even under non-oxidative conditions but only when DBDS was present in the oil. The reaction was accelerated in the presence of oxygen and competes for available copper with the parallel copper carboxylate producing reaction. The AC breakdown strength was reduced after aging, but exhibited a more catastrophic reduction in oils containing DBDS, confirming the detrimental effects of CuxS on breakdown performanc

The forgotten flies:The importance of non-syrphid Diptera as pollinators

Bees, hoverflies and butterflies are taxa frequently studied as pollinators in agricultural and conservation contexts. Although there are many records of non-syrphid Diptera visiting flowers, they are generally not regarded as important pollinators. We use data from 30 pollen-transport networks and 71 pollinator-visitation networks to compare the importance of various flower-visiting taxa as pollen-vectors. We specifically compare non-syrphid Diptera and Syrphidae to determine whether neglect of the former in the literature is justified. We found no significant difference in pollen-loads between the syrphid and non-syrphid Diptera. Moreover, there was no significant difference in the level of specialization between the two groups in the pollen-transport networks, though the Syrphidae had significantly greater visitation evenness. Flower visitation data from 33 farms showed that non-syrphid Diptera made up the majority of the flower-visiting Diptera in the agricultural studies (on average 82% abundance and 73% species richness), and we estimate that non-syrphid Diptera carry 84% of total pollen carried by farmland Diptera. As important pollinators, such as bees, have suffered serious declines, it would be prudent to improve our understanding of the role of non-syrphid Diptera as pollinators

Volume 14, Number 3, June 1994 OLAC Newsletter

Digitized June 1994 issue of the OLAC Newsletter

Volume 16, Number 2, June 1996 OLAC Newsletter

Digitized June 1996 issue of the OLAC Newsletter

Volume 14, Number 3, March 1994 OLAC Newsletter

Digitized March 1994 issue of the OLAC Newsletter

Volume 15, Number 1, March 1995 OLAC Newsletter

Digitized March 1995 issue of the OLAC Newsletter

Volume 14, Number 4, December 1994 OLAC Newsletter

Digitized December 1994 issue of the OLAC Newsletter