Modifying native and exotic species richness correlations: the influence of fire and seed addition.

An important goal in restoration is to increase the richness of native species while reducing exotic species. However, native species richness is often positively correlated with exotic species richness. In a grassland-savanna system in Michigan (USA), we show that management that focuses on changing the nature of the exotic-native richness relationship can be used to restore native communities. Native and exotic species richnesses were positively correlated, likely due to a shared coupling with aboveground live biomass (a surrogate for productivity). The addition of native seed shifted the exotic-native richness relationship from a linear positive to a monotonic relationship: in areas of intermediate levels of exotic species richness, seed addition increased native diversity without an associated effect on exotic diversity, but in areas of high or low exotic richness, it did not affect native species richness. Prescribed burning broke the correlation between native and exotic richness with no consistent effect on the richness of either group. However, when burning was combined with native-seed addition, the relationship between native and exotic richness was maintained and was shifted upwards, enhancing native recruitment. Although aboveground productivity was strongly related to species richness across the landscape, changes in productivity did not drive these shifts.     

Rheological study of biodegradable blends of starch and polyvinyl alcohol

The rheological behavior of biodegradable blends of starch and poly(vinyl alcohol) (PVOH) was measured as a function of temperature, shear rate, and moisture content using a capillary rheometer. An excellent correlation was found with a rheological model which was used as a means to characterize the influence of starch/PVOH content as well as a qualification of the viscosity for simulation studies. This model consisted of a power law dependence on shear rate, an Arrhenius dependence on temperature, and an exponential dependence on moisture.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts.Guest Editor: Dr. Randall Shogren, USDA.     

Reduced disease in offspring: A benefit of coloniality in sunfish

Summary Increased disease and parasitism are a well-documented cost of group living for colonial birds and mammals, but we now show that disease in offspring of fish may be reduced by nesting in colonies. The aquatic fungusSaprolegnia sp., which is a common cause of egg mortality among freshwater fishes, is more prevalent in the nests of solitary than colonial male bluegill sunfish (Lepomis macrochirus). Moreover, fungal infection decreases with nest density in colonies. This may be due in part to a behavioural advantage since colonial males can devote less time to defending eggs and more time to fanning them, which reduces fungal infection. In addition, we demonstrate experimentally that solitary nests become infected at higher rates than colonial nests, even in the absence of parental males. This suggests that colonies are encountered by spores at a lower rate and/or that the large number of nests in colonies dilutes the number of fungal spores per nest. Through one or all of these mechanisms, egg mortality in colonial nests is lowered significantly. Therefore, in some cases, disease may select for group living.     

Episodes of incivility between subordinates and supervisors: examining the role of self‐control and time with an interaction‐record diary study

Scholars have hypothesized that experiencing incivility not only negatively affects well‐being, but may even trigger further antisocial behavior. Previous research, however, has focused mainly on the relation between incivility and well‐being. Thus, little is known about the behavioral consequences of incivility. With this in mind, we conducted an interaction‐record diary study to examine whether supervisor incivility causes retaliatory incivility against the supervisor. Using the self‐control strength model as a framework, we further examined whether the target's trait (trait self‐control) and state (exhaustion) self‐regulatory capacities moderate this effect. In addition, we examined the role of time by testing the duration of the effect. When we analyzed the full data set, we found no support for our hypotheses. However, using a subset of the data in which the subsequent interaction happened on the same day as the prior interaction, our results showed that experiencing incivility predicted incivility in the subsequent interaction, but only when the time lag between the two interactions was short. Furthermore, in line with the assumption that self‐regulatory capacities are required to restrain a target from retaliatory responses, the effect was stronger when individuals were exhausted. In contrast to our assumption, trait self‐control had no effect on instigated incivility. Copyright © 2015 John Wiley & Sons, Ltd.     

A NET BENEFIT MODEL FOR RECREATION PLANNING AT DRINKING WATER RESERVOIRS1

A management model was developed for determining levels of recreation activities at public drinking water reservoirs. Quabbin Reservoir, located in central Massachusetts, served as a case study for the model. An interdisciplinary research team was formed to study the impact of selected recreation activities on water quality, public demand and willingness to pay for selected recreation activities, carrying capacity constraints, and the economic cost/benefits associated with increases in recreation at the Quabbin Reservation. Study variables were integrated into a quadratic programming model, producing the number of participants that corresponds to maximum net benefits for specific development packages on design days. The recreation mix associated with maximum net economic benefits was found to be cost-effective (assuming the use of reasonable entrance fees) and not deleterious to water quality. However, as a result of the findings of a related study, it was recommended that nutrients, particularly from wastewater, not be permitted to enter the reservoir, since the current phosphorous level may be at a critical point. Management techniques that would safeguard against this occurrence were recommended. The model was sensitive to management objectives; recommendations were limited to activities that would not lower the existing high quality of Quabbin water.