Biomass Data (biomass + data)

Distribution by Scientific Domains

Selected Abstracts

Managing non-target, data-poor species using catch limits: lessons from the Alaskan groundfish fishery

Abstract, The 2006 reauthorisation of the Magnuson-Stevens Fishery Conservation and Management Act requires annual catch limits for all target and non-target species within federally managed fisheries in the United States. In Alaska, both target and non-target species in the Alaska groundfish fisheries have been managed using catch limits since the early 1990s. Non-target species that are caught incidentally in a fishery require monitoring to ensure that the population is not negatively impacted by commercial fishing. Resource assessment scientists have been challenged with obtaining sufficient data to recommend an acceptable catch level for management of these species. This paper reviews three case studies where a catch limit is determined for non-target species when certain data are limited: (1) varying levels of biomass and catch data for all species within a species group or complex; (2) adequate catch data but no biomass data; (3) emerging target fishery of data-poor species, plus an example of how a complex of ecosystem component species is managed. [source]

Ant colony size and the scaling of reproductive effort

J. Z. Shik
Summary 1Reproductive effort typically scales as mass075 in unitary organisms, but less is known about such scaling in colonial organisms. 2I compiled data on worker and reproductive number at maturity for 65 ant species and found an interspecific allometry (alate number = worker number073) whose exponent was significantly < 1, even after a phylogenetic correction. 3When I analyzed 15 species for which biomass data were available, I found an interspecific isometry (alate biomass = worker biomass089) whose exponent was not significantly different from 1. Analysis of maximum species biomass values, rather than averages, strengthened this isometry, yielding a slope b = 101 that was also not distinguishable from 1. 4Species with larger colony size at reproduction tended to couple investment in proportionately fewer alates with investment in larger male and female alates. 5This comparative analysis suggests a trade-off between alate size and number, and provides a framework for studying the diversity of colony life histories and the mechanisms generating allometries. [source]

Year-to-year variation in plant competition in a mountain grassland

Summary 1We used a series of removal experiments to examine how species response to competition and climatic differences varied in three different years. We tested the interaction between removal of the dominant grass species, Festuca rubra, and year-to-year environmental variation in a mown mountain grassland. 2In each year, we quantified shoot frequency and above-ground biomass of all remaining plant species. Above-ground responses were tested both by analysis of covariance and by redundancy analysis with randomization tests of changes in total species composition. 3Analysis of above-ground biomass data showed that other species compensated for the removal of F. rubra biomass within 2 years and that the response in total biomass of the community did not differ among years in which the experiment was started. 4Multivariate tests showed that species composition changed as a result of the removal; grass biomass and frequency increased more than that of dicotyledons. However, response of species composition to removal of F. rubra was significantly different between onset years. Specific conditions in individual years thus affect the competitive ability of individual species in a non-additive way. 5Our results indicate that the year-to-year variation at the site has the potential to affect species coexistence and richness. As a consequence, year-to-year variation of climatic parameters may be an important driving factor in community dynamics and should be taken into account in studies of ecosystem response to climate. [source]

Geographical and interannual variability in biomass partitioning in grassland ecosystems: a synthesis of field data

Dafeng Hui
Summary ,,Biomass partitioning is an important variable in terrestrial ecosystem carbon modeling. However, geographical and interannual variability in fBNPP, defined as the fraction of belowground net primary productivity (BNPP) to total NPP, and its relationship with climatic variables, have not been explored. ,,Here we addressed these issues by synthesizing 94 site-year field biomass data at 12 grassland sites around the world from a global NPP database and from the literature. ,,Results showed that fBNPP varied from 0.40 to 0.86 across 12 sites. In general, savanna and humid savanna ecosystems had smaller fBNPP but larger interannual variability in fBNPP, and cold desert steppes had larger fBNPP but smaller interannual variability. While mean fBNPP at a site decreased significantly with increasing mean annual temperature and precipitation across sites, no consistent temporal response of fBNPP with annual temperature and precipitation was found within sites. ,,Based on these results, both geographical variability in fBNPP and the divergent responses of fBNPP with climatic variables at geographical and temporal scales should be considered in global C modeling. [source]