Disturbance, Diversity, and Invasion: Implications for Conservation

Disturbance is an important component of many ecosystems, and variations in disturbance regime can affect ecosystem and community structure and functioning. The "intermediate disturbance hypothesis" suggests that species diversity should be highest at moderate levels of disturbance. However, disturbance is also known to increase the invasibility of communities. Disturbance therefore poses an important problem for conservation management, Here, we review the effects of disturbances such as fire grazing, soil disturbance and nutrient addition on plant species diversity and invasion with particular emphasis on grassland vegetation. Individual components of the disturbance regime can have marked effects on species diversity, but it is often modifications of the existing regime that have the largest influence. Similarly, disturbance can enhance invasion of natural communities, but frequently it is the interaction between different disturbances that has the largest effect. The natural disturbance regime is now unlikely to persist within conservation areas since fragmentation and human intervention have usually modified physical and biotic conditions. Active management decisions must now be made on what disturbance regime is required and this requires decisions on what species are to be encouraged or discouraged.     

Land Use, Lag Times and the Detection of Demographic Change: The Case of the Acorn Woodpecker

Changes in land-use patterns that alter habitat may have a delayed negative effect on animal species occupying that habitat, and thus such effects may not be recognized for years. In Water Canyon, located in the Magdalena Mountains of southcentral New Mexico, we studied a relatively stable population of the cooperatively breeding Acorn Woodpecker ( Melanerpes formicivorus ) from 1975 to 1984. These woodpeckers rely on self-constructed storage sites, or "granary trees," to hold the acorns used during the winter and spring. Most granaries were in dead trunks and limbs of the narrow-leafed cottonwood trees ( Populus angustifolia . Storage sites form the primary basis for differential quality among territories. Groups of woodpeckers with large storage facilities (high-quality territories) have greater annual reproductive success and survival than do pairs or groups with poorly developed storage sites. In the summers of 1994 and 1995 we censused the original study site, which had held 21 territories. Most territories that had contained birds a decade earlier were unoccupied. This drastic decline was correlated with the loss of nearly all large storage facilities because of the collapse of the granary trees. Most neighboring territories with lesser storage facilities also were vacant. The lack of production of new, high-quality granaries for the period 1975–1995 probably is due inpart to the age structure of the cottonwood trees, which is distinctly bimodal: nearly all trees are either very young or old. There are now fewer old, partly dead trees that could provide granary sites. The scarcity of middle-aged trees reflects a period of intensive cattle grazing in Water Canyon, during which time production of young cottonwoods was suppressed.     

Comparison of two reactor concepts for anoxygenic H2 production by Rhodobacter capsulatus

In the contribution at hand two main concepts of photobioreactors are considered: the flat-panel reactor and the tubular reactor. Both reactors are investigated under outdoor conditions in Germany in the summer time for their applicability for H₂ production by means of purple non-sulphur bacteria Rhodobacter capsulatus. The experiments are performed as fed batch. The performance of a photobioreactor is evaluated in terms of H₂ productivity per IRS (illuminated reactor surface). It is demonstrated that both reactors could be operated stable for several weeks with comparable H₂ productivities. The mean hydrogen productivity for the panel and the tubular reactor is 3690 ml H₂/(m_IRS² d) and 3350 ml H₂/(m_IRS² d) respectively. While approximately 8 m² of the illuminated reactor surface of the panel reactor can be installed on 1 m² of ground space, the relation of the illuminated reactor surface to the ground area for the tubular reactor is approximately 1–1.     

Calculating Field‐Scale Evapotranspiration with Closed‐Chamber and Remote Sensing Methods

Currently, there is no agreed upon method for estimating evapotranspiration (ET) across large regions such as the state of New Mexico. Remote sensing methods have potential for providing a solution, but require validation. A comparison between field‐scale ET measurements using a portable chamber ET measurement device and modeled ET using the remote sensing Regional Evapotranspiration Estimation Model (REEM) was performed where the model had not been previously evaluated. Data were collected during the growing season of 2015 in three irrigated agricultural valleys of northern New Mexico in agricultural and nonagricultural settings. No statistically significant difference was observed in agricultural datasets between means of measured (M = 3.7 mm/day, SE = 0.31 mm/day) and modeled (M = 4.0 mm/day, SE = 0.01 mm/day) daily ET; t(17) = ?1.50, p = 0.15, α = 0.05. As there was no statistical difference observed between agricultural datasets, results support the use of REEM in irrigated agricultural areas of northern New Mexico. A statistically significant difference was observed in nonagricultural datasets between means of measured (M = 1.7 mm/day, SE = 0.22 mm/day) and modeled (M = 0.0 mm/day, SE = 0.00 mm/day) daily ET; t(9) = 1.79, p = 5.7 × 10^?6, α = 0.05. With additional calibrations and air temperature sensors placed outside of agricultural areas, REEM may be suitable for use in nonagricultural areas of northern New Mexico.     

Landscape patterns and parcel boundaries: an analysis of composition and configuration of land use and land cover in south-central Indiana

In many areas of the world, socioeconomic and political factors are increasingly impacting spatial patterns of land use and land cover in the landscape. Much of the land in the United States has been divided using a grid-based system that was implemented to realize socioeconomic and political goals rather than to protect and conform to biophysical differences. The borders of individual parcels of land often reflect the boundary lines created by this system. These borders are important components of policies related to land management such as zoning and private land use decisions. The potential impact this system of land division may have on spatial patterns in a landscape remains unclear. The majority of landscape research has focused exclusively on biophysical differences occurring over relatively large areas of land and ignored possible finer-scale, human impacts on landscape composition and configuration. There is a need for research on spatial patterns occurring over areas that match socioeconomically or politically important units of land in order to improve understanding of relationships between human related processes and ecosystem functions and to create better management policies.This research explores whether the system of land parcelization is evident in patterns of land use and land cover in the landscape of south-central Indiana. In particular, it investigates whether parcel boundaries correspond to distinct changes in the composition and configuration of forest, developed, and agricultural lands. This research uses theory and methodology from geography, geographic information science, and landscape ecology to analyze patterns of land use and land cover in a rural to semi-rural county in south-central Indiana. A classification of a remotely sensed image is used as a basis for calculating metrics of landscape composition and configuration with the use of a geographic information system. The metrics are calculated for areas of forest, developed, and agricultural land associated with a sample of parcels chosen to represent all the parcels within Monroe County. The values for areas near the parcel boundaries are compared with the values for areas at relatively short distances from the parcel boundaries. This comparison indicates whether there is a distinct change in the composition or configuration of the landscape occurring at approximately the parcel boundaries.The results suggest that in Monroe County, Indiana, changes in the composition of the landscape, particularly the amount of area covered by agriculture and forest, correspond with parcel boundaries. Changes in the configuration of agricultural and, to a lesser extent, developed lands also occur near parcel boundaries. The results support the hypothesis that the grid-based system of parcelization has affected spatial patterns of land use and land cover. These results illustrate the potential impact socioeconomic and political systems may have on spatial patterns in a landscape.     

The humidity dependence of ozone deposition onto a variety of building surfaces

Measurements of the dry deposition velocity of O₃ to material samples of calcareous stone, concrete and wood at varying humidity of the air, were performed in a deposition chamber. Equilibrium surface deposition velocities were found for various humidity values by fitting a model to the time-dependent deposition data. A deposition velocity-humidity model was derived giving three separate rate constants for the surface deposition velocities, i.e. on the dry surface, on the first mono-layer of adsorbed water and on additional surface water. The variation in the dry air equilibrium surface deposition velocities among the samples correlated with variations in effective areas, with larger effective areas giving higher measured deposition velocities. A minimum for the equilibrium surface deposition velocity was generally measured at an intermediate humidity close to the humidity found to correspond to one mono-layer of water molecules on the surfaces. At low air humidity the equilibrium surface deposition velocity of O₃ was found to decrease as more adsorbed water prevented direct contact of the O₃ molecules with the surface. This was partly compensated by an increase as more adsorbed water became available for reaction with O₃. At high air humidity the equilibrium surface deposition velocity was found to increase as the mass of water on the surface increased. The deposition velocity on bulk de-ionised water at RH=90% was an order of magnitude lower than on the sample surfaces.     

Leader self‐awareness: An examination and implications of women's under‐prediction

Self‐awareness represents an important aspect of leadership. However, past research on leader self‐awareness has focused on one component of self‐awareness, self versus others' ratings, leaving the second component, the ability to anticipate the views of others, largely neglected. We examined this second component of self‐awareness by focusing on women leaders who have been found to under‐predict how others rate them. In two studies, we measured how women leaders anticipate the views of their bosses in regard to their leadership. In Study 1, 194 leaders rated their leadership, were rated by their bosses, and then predicted how their bosses rated their leadership. While we found that women under‐predict their boss ratings compared with men, we did not find that boss gender or feedback played a role in this under‐prediction. In Study 2, 76 female leaders identified (via open‐ended questions) possible reasons and consequences of under‐prediction for women in organizations. Results from Study 2 reveal the following: (1) the reasons for women's under‐prediction include a lack of self‐confidence, differences in feedback needs, learned gender roles, and self‐sexism; and (2) the perceived consequences of under‐prediction are negative for both women and the organization. Copyright © 2013 John Wiley & Sons, Ltd.