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Root respiration rates have been shown to be correlated with temperature and root N concentration in studies of individual forest types or species, but it is not known how universal these relationships are across forest species adapted to widely different climatic and edaphic conditions. In order to test for broad, cross-species relationships, we measured fine root respiration, as O2 consumption,...
Tortula ruralis is a homoiochlorophyllous-desiccation-tolerant (HDT) moss that retains all pigments when dehydrated and rapidly recovers physiological function upon rehydration. This moss forms extensive cover in exposed and shaded areas in the sandy semi-arid grasslands of Central Europe. We hypothesized that contrasting drying regimes between these microhabitats would affect plant N status, constraints...
Pressurized ventilation acts to increase the oxygen supply to roots and rhizomes in some species of emergent plants. In a greenhouse experiment, we investigated how pressurized ventilation affected growth, biomass allocation and mineral content of Phragmites australis in two water depths (15 cm or 75 cm) and two substrates (organic sediment or sand). Through perforating each stem above the water surface,...
Activity patterns of colonies of the central-place foraging (CPF) social caterpillar, Eriogaster lanestris, were electronically long-term recorded under field conditions. Caterpillars showed distinct, highly synchronized activity bouts during which they left their tent, fed on their host-plant and returned to their tent. Caterpillars stayed almost inactive during their digestion phases when they rested...
Plants can have a significant impact on the fitness and efficacy of natural enemies. These interactions are widespread and suggest that the influences on the population dynamics of insect herbivores cannot be simply divided into "bottom up" and "top down". Several questions remain little studied in this field. Firstly, to what extent can plants affect the interactions between insects...
Although widely distributed on rocky reefs at Santa Catalina Island (southern California, USA), the small, substrate-oriented fish, Lythrypnus dalli, often reaches its highest densities in areas of extreme vertical relief where the sea urchin, Centrostephanus coronatus, is common. Through surveys and manipulative field experiments, we examined the extent to which the availability of C. coronatus influenced...
Large-bodied zooplankton of the genus Daphnia are thought to be keystone species in freshwater pelagic habitats, potentially able to exert strong grazing effects and enhance phosphorus limitation of algae. I examined the degree to which Daphnia pulex differ from small-bodied zooplankton in their effects on algal biomass, seston C:P and N:P, total nitrogen and total phosphorus. This was done with both...
The influence of habitat structure on abundance and taxonomic richness of epibenthic harpacticoid copepods in seagrass beds of Port Phillip Bay, Australia was investigated using artificial seagrass plants. The density and length of artificial seagrass plants was manipulated at three sites over two sampling times. Results for artificial plants were also compared with controls without plants. The presence...
The importance of wood ants (Formica rufa) in determining the community structure (defined as the relative abundance of component species) and small-scale distribution of carabids was examined in a mature Scots pine stand in the New Forest, southern England. Carabids and wood ants were sampled by pitfall trapping throughout the forest stand from March to September 1998. The abundance of individual...
Portions of a regenerating scrub oak ecosystem were enclosed in open-top chambers and exposed to elevated CO2. The distinct 13C signal of the supplemental CO2 was used to trace the rate of C integration into various ecosystem components. Oak foliage, stems, roots and ectomycorrhizae were sampled over 3 years and were analyzed for 13C composition. The aboveground tissue 13C equilibrated to the novel...
Specificity of plant induction responses may be important to the interactions between mustards and insect herbivores. This study compared the effects of the cabbage white butterfly, Pierisrapae (L.), cabbage looper, Trichoplusiani (Hubner), and the mustard flea beetle, Phyllotretacruciferae (Goeze) on induction of leaf trichome density, sinigrin concentration, and nitrogen concentration in black mustard,...
We used a data set of ungulate censuses from 31 natural ecosystems from East and Southern Africa to test two hypotheses: (1) megaherbivores should dominate ungulate communities in ecosystems with high rainfall and low soil nutrient status because of their ability to survive on poor quality food resources, and (2) the abundance of megaherbivores affects the abundance of the mesoherbivores, distinguishing...
Understanding how species interactions shape the structure of ecological communities based on pairwise comparisons has been a difficult undertaking for ecologists because effects in reassembled communities can be different than simple density-mediated interactions would suggest. Part of this complexity occurs because many species change their behavior and morphology with different predators and competitors...
Many species of neotropical rodents consume and subsequently disperse viable spores of arbuscular mycorrhizal fungi (AMF). Consequently, rodents may be important determinants of both AMF and tree community composition in neotropical forests. We examined the influence of both availability of other food resources and season on the consumption and subsequent dispersal of AMF spores by Proechimys semispinosus ...
Global climate change models predict reduced cloud water in tropical montane forests. To test the effects of reduced cloud water on epiphytes, plants that are tightly coupled to atmospheric inputs, we transplanted epiphytes and their arboreal soil from upper cloud forest trees to trees at slightly lower elevations that are naturally exposed to less cloud water. Control plants moved between trees within...
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