Crown Research Institutes

About: Crown Research Institutes is a government organization based out in Wellington, New Zealand. It is known for research contribution in the topics: Geothermal gradient & Biodiversity. The organization has 323 authors who have published 361 publications receiving 11016 citations.

Disturbance to Marine Benthic Habitats by Trawling and Dredging: Implications for Marine Biodiversity

Abstract: ▪ Abstract The direct effects of marine habitat disturbance by commercial fishing have been well documented. However, the potential ramifications to the ecological function of seafloor communities and ecosystems have yet to be considered. Soft-sediment organisms create much of their habitat's structure and also have crucial roles in many population, community, and ecosystem processes. Many of these roles are filled by species that are sensitive to habitat disturbance. Functional extinction refers to the situation in which species become so rare that they do not fulfill the ecosystem roles that have evolved in the system. This loss to the ecosystem occurs when there are restrictions in the size, density, and distribution of organisms that threaten the biodiversity, resilience, or provision of ecosystem services. Once the functionally important components of an ecosystem are missing, it is extremely difficult to identify and understand ecological thresholds. The extent and intensity of human disturbance to ...

Three-Dimensional Surround Sound Systems Based on Spherical Harmonics

Abstract: The theory of recording and reproduction of three-dimensional sound fields based on spherical harmonics is reviewed and extended. Free-field, sphere, and general recording arrays are reviewed, and the mode-matching and simple source approaches to sound reproduction in anechoic environments are discussed. Both methods avoid the need for both monopole and dipole loudspeakers—as required by the Kirchhoff–Helmholtz integral. An error analysis is presented and simulation examples are given. It is also shown that the theory can be extended to sound reproduction in reverberant environments.

Is "Sampling Effect" a Problem for Experiments Investigating Biodiversity-Ecosystem Function Relationships?

Abstract: Increasingly, those studies which are aiming to study the relationship between biodiversity and ecosystem function are utilising experimental designs in which species diversity is varied, with the species composition at each level of diversity being determined randomly from a predetermined species pool. Studies utilising such designs have been criticised on the basis that they are confounded by sampling effect (SE) or selection probability effect, i.e. that the treatments which have the highest diversity have a greater probability of being dominated by the most productive species of the entire species pool; however it has also been claimed that SE is a legitimate mechanism by which diversity effects may express themselves in nature. Firstly I show, using an example of a recently published study claiming to show a diversity effect, how SE can result in the identification of apparent relationships between diversity and ecosystem properties which have little meaning in the real world. I then point out that if we accept SE is a diversity mechanism operating in nature, it is firstly necessary to assume that biological communities are randomly assembled with regard to the ecosystem property being measured; this assumption is inconsistent with conventional concepts about how biological communities are organised. Finally I discuss other experimental approaches which may remove the likelihood of results of biodiversity studies from being confounded by problems associated with SE. None of those studies in which SE may contribute to the observed outcome have successfully shown a result which cannot be ascribed to artifact, and alternative experimental approaches are required in order to better understand how biodiversity loss affects ecosystems in nature.

Understanding Background Mixture Models for Foreground Segmentation

Abstract: The seminal video surveillance papers on moving object segmentation through adaptive Gaussian mixture models of the background image do not provide adequate information for easy replication of the work. They also do not explicitly base their algorithms on the underlying statistical theory and sometimes even suffer from errors of derivation. This tutorial paper describes a practical implementation of the Stauffer-Grimson algorithm and provides values for all model parameters. It also shows what approximations to the theory were made and how to improve the standard algorithm by redefining those approximations.

Status and management of world sea urchin fisheries

Abstract: World production of sea urchins peaked in 1995, when 120 306 t were landed. Chile dominates world production, producing more than half the world's total landings of 90 257 t in 1998. Other important fisheries are found in Japan, Maine, British Columbia, California, South Korea, New Brunswick, Russia, Mexico, Alaska, Nova Scotia, and in a number of countries that produced less than 1000 t in 1998. Aside from the Chilean fishery for Loxechinus albus, most harvest is of Strongylocentrotus spp., particularly S. intermedius, S. franciscanus, and S. droebachiensis. Only a small minority of fisheries have been formally assessed and in the absence of such assessments it is difficult to determine whether fisheries are overfished or whether the large declines observed in many represent the "fish down" of accumulated biomass. Nevertheless, those in Chile, Japan, Maine, California and Washington and a number of smaller fisheries, have declined considerably since their peaks and are likely to be overfished. Fisheries in Japan, South Korea and the Philippines have been enhanced by reseeding hatchery-reared juveniles and by modifying reefs to increase their structural complexity and to promote the growth of algae. Sea urchin fisheries have potentially large ecological effects, usually mediated through increases in the abundance and biomass of large brown algae. Although such effects may have important consequences for management of these and related fisheries, only in Nova Scotia, South Korea and Japan is ecological knowledge incorporated into management.