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Terrestrial Food Webs (terrestrial + food_web)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

A cross-ecosystem comparison of the strength of trophic cascades

ECOLOGY LETTERS, Issue 6 2002
Jonathan B. Shurin
Abstract Although trophic cascades (indirect effects of predators on plants via herbivores) occur in a wide variety of food webs, the magnitudes of their effects are often quite variable. We compared the responses of herbivore and plant communities to predator manipulations in 102 field experiments in six different ecosystems: lentic (lake and pond), marine, and stream benthos, lentic and marine plankton, and terrestrial (grasslands and agricultural fields). Predator effects varied considerably among systems and were strongest in lentic and marine benthos and weakest in marine plankton and terrestrial food webs. Predator effects on herbivores were generally larger and more variable than on plants, suggesting that cascades often become attenuated at the plant,herbivore interface. Top-down control of plant biomass was stronger in water than on land; however, the differences among the five aquatic food webs were as great as those between wet and dry systems. [source]

Bioavailability of decabromodiphenyl ether to the marine polychaete Nereis virens

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010
Susan L. Klosterhaus
Abstract The flame retardant decabromodiphenyl ether (BDE 209) accumulates in humans and terrestrial food webs, but few studies have reported the accumulation of BDE 209 in aquatic biota. To investigate the mechanisms controlling the bioavailability of BDE 209, a 28-d bioaccumulation experiment was conducted in which the marine polychaete worm Nereis virens was exposed to a decabromodiphenyl ether (deca-BDE) commercial mixture (>85% BDE 209) in spiked sediments, in spiked food, or in field sediments. Bioaccumulation from spiked substrate with maximum bioavailability demonstrated that BDE 209 accumulates in this species. Bioavailability depends on the exposure conditions, however, because BDE 209 in field sediments did not accumulate (<0.3 ng/g wet weight; 28-d biota-sediment accumulation factors [BSAFs] <0.001). When exposed to deca-BDE in spiked sediments also containing lower brominated congeners (a penta-BDE mixture), bioaccumulation of BDE 209 was 30 times lower than when exposed to deca-BDE alone. Selective accumulation of the lower brominated congeners supports their prevalence in higher trophic level species. The mechanisms responsible for limited accumulation of BDE 209 may involve characteristics of the sediment matrix and low transfer efficiency in the digestive fluid. Environ. Toxicol. Chem. 2010;29:860,868. © 2009 SETAC [source]

Trophic supplements to intraguild predation

OIKOS, Issue 4 2007
Matthew P. Daugherty
Intraguild predation (IGP) is a dominant community module in terrestrial food webs that occurs when multiple consumers feed both on each other and on a shared prey. This specific form of omnivory is common in terrestrial communities and is of particular interest for conservation biology and biological control given its potential to disrupt management of threatened or pest species. Extensive theory exists to describe the dynamics of three-species IGP, but these models have largely overlooked the potential for other, exterior interactions, to alter the dynamics within the IGP module. We investigated how three forms of feeding outside of the IGP module by intraguild predators (i.e. trophic supplementation) affect the dynamics of the predators (both IG predator and IG prey) and their shared resource. Specifically, we examined how the provision of a constant donor-controlled resource, the availability of an alternative prey species, and predator plant-feeding affect the dynamics of IGP models. All three forms of trophic supplements modified the basic expectations of IGP theory in two important ways, and their effects were similar. First, coexistence was possible without the IG prey being a superior competitor for the original shared resource if the IG prey could effectively exploit one of the types of trophic supplements. However, supplements to the IG predator restricted the potential for coexistence. Second, supplements to the IG prey ameliorated the disruptive effects of the IG predator on the suppression of the shared resource, promoting effective control of the resource in the presence of both predators. Consideration of these three forms of trophic supplementation, all well documented in natural communities, adds substantial realism and predictive power to intraguild predation theory. [source]

The impacts of rising CO2 concentrations on Australian terrestrial species and ecosystems

AUSTRAL ECOLOGY, Issue 6 2010
MARK J. HOVENDEN
Abstract The increasing atmospheric concentration of carbon dioxide ([CO2]) contributes to global warming and the accompanying shifts in climate. However, [CO2] itself has the potential to impact on Australia's terrestrial biodiversity, due to its importance in the photosynthetic process, which underlies all terrestrial food webs. Here, we review our knowledge regarding the impacts of elevated [CO2] on native terrestrial species and ecosystems, and suggest key areas in which we have little information on this topic. Experimental information exists for 70 (or less than 0.05%) of Australia's native terrestrial plant and animal species. Of these, 68 are vascular plants. The growth of Australian woody species is more reliably increased by elevated [CO2] than it is in grasses. At the species level, the most overwhelming responses to increased [CO2] are a reduction in plant nitrogen concentration and an increase in the production of secondary metabolites. This is of particular concern for Australia's unique herbivorous and granivorous marsupials, for which no information is available. While many plant species also displayed increased growth rates at higher [CO2], this was far from universal, indicating that changes in community structure and function are likely, leading to alterations of habitat quality. Future research should be directed to key knowledge gaps including the relationship between [CO2], fire frequency and fire tolerance and the impacts of increasing [CO2] for Australia's iconic browsing mammals. We also know virtually nothing of the impacts of the increasing [CO2] on Australia's unique shrublands and semi-arid/arid rangelands. In conclusion, there is sufficient information available to be certain that the increasing [CO2] will affect Australia's native biodiversity. However, the information required to formulate predictions concerning the long-term future of almost all organisms is far in excess of that currently available. [source]