A Synthesis of Plant Invasion Effects on Biodiversity Across Spatial Scales

American Journal of Botany, 98(3): 539–548. 2011

Kristin I. Powell, Jonathan M. Chase, and Tiffany M. Knight

“Premise of the study: Invasive plant species are typically thought to pose a large threat to native biodiversity, and local-scale studies typically confirm this view. However, plant invaders rarely cause regional extirpations or global extinctions, causing some to suggest that invasive species ’ influence on native biodiversity may not be so dire. We aim to synthesize the seemingly conflicting literature in plant invasion biology by evaluating the effects of invasive plant species across spatial scales.

“Methods: We first conducted a meta-analysis on the effects of invasive plants on the species richness of invaded communities across a range of spatial extents. We then discuss studies that consider the role of invasive plants on regional spatial scales for which such meta-analyses are not possible. Finally, we develop a conceptual framework to synthesize the influence of invasive species across spatial scales by explicitly recognizing how invasive species alter species-occupancy distributions.

“Key results: We found a negative relationship between the spatial extent of the study and the effect size of invasive plants on species richness. Our simulation models suggest that this result can occur if invaders, either proportionately or disproportionately, reduce the occupancy of common species to a greater degree than rare species.

“Conclusions: Future studies should consider the influence of invaders on the abundance and occupancy-level changes in native species to inform how invasive plants will influence native species richness relationships across spatial scales. This approach will allow greater predictive ability for forecasting changes in biodiversity”

Geovisualization Challenges of Seascape Genetics

GeoViz: Linking Geovisualization with Spatial Analysis and Modeling, 10-11 March 2011, Hamburg, Germany

Eoin Mac Aoidh and Jann Th. Martinsohn

“Population genetics are widely used for wildlife management and can also support environmental policy decisions. Landscape genetics, termed ’seascape genetics’ for the marine environment, relates the population genetic structure of a species to its surrounding spatial environment. This allows us to link the genetic make-up of a population with influential environmental factors. Unfortunately, there prevails a communication gap between the genetic research community and regulators in the domain thus valuable information resulting from land- or seascape genetics is often lost in translation. In this article we look at the fisheries sector as a case study and propose geovisualizations as an effective means to improve the communication of information resulting from seascape genetic analysis to regulators and other stakeholders in the domain. Using this example we discuss the challenges of implementing such geovisualizations to better integrate genetic data into fisheries management, and more generally to effectively communicate scientific advice to stakeholders.”

Integrating Field Sampling, Geostatistics, and Remote Sensing to Map Wetland Vegetation in the Pantanal, Brazil

Biogeosciences, 8, 667-686, 2011

J. Arieira, D. Karssenberg, S. M. de Jong, E. A. Addink, E. G. Couto, C. Nunes da Cunha, and J. O. Skøien

“Development of efficient methodologies for mapping wetland vegetation is of key importance to wetland conservation. Here we propose the integration of a number of statistical techniques, in particular cluster analysis, universal kriging and error propagation modelling, to integrate observations from remote sensing and field sampling for mapping vegetation communities and estimating uncertainty. The approach results in seven vegetation communities with a known floral composition that can be mapped over large areas using remotely sensed data. The relationship between remotely sensed data and vegetation patterns, captured in four factorial axes, were described using multiple linear regression models. There were then used in a universal kriging procedure to reduce the mapping uncertainty. Cross-validation procedures and Monte Carlo simulations were used to quantify the uncertainty in the resulting map. Cross-validation showed that accuracy in classification varies according with the community type, as a result of sampling density and configuration. A map of uncertainty derived from Monte Carlo simulations revealed significant spatial variation in classification, but this had little impact on the proportion and arrangement of the communities observed. These results suggested that mapping improvement could be achieved by increasing the number of field observations of those communities with a scattered and small patch size distribution; or by including a larger number of digital images as explanatory variables in the model. Comparison of the resulting plant community map with a flood duration map, revealed that flooding duration is an important driver of vegetation zonation. This mapping approach is able to integrate field point data and high-resolution remote-sensing images, providing a new basis to map wetland vegetation and allow its future application in habitat management, conservation assessment and long-term ecological monitoring in wetland landscapes.”

Towards Appropriate Representations of Quantitative Data in Virtual Environments

GeoViz: Linking Geovisualization with Spatial Analysis and Modeling, 10-11 March 2011, Hamburg, Germany

Susanne Bleisch

“Displays of quantitative data within 3D virtual environments are quickly created with today’s technological options but we know little about the appropriateness of such representations. This paper presents a study which experimentally tests six different proportional symbols for the display of quantitative data within virtual environments. The tested symbols are 2D and 3D bars and 2D circles with and without reference frames. Preliminary results show that circles are not as difficult to interpret as expected but 2D and 3D bars yield more accurate results with less variation. The full evaluation will be available soon.”