Determinants of the pathways of litter chemical decomposition in a tropical region.

Litter decomposition is a key ecosystem process, yet our understanding of the drivers in chemical changes in leaves during decay is limited. Our aim was to determine the comparative differences (chemical divergence or convergence) between sites and the drivers of decay pathways. We used the litterbag method ('in situ' litterfall and standardized 'control' leaves) in Australian tropical rainforests and near-infrared spectrometry to show the chemical pathways during decomposition (c.

Palatability mapping: a koala's eye view of spatial variation in habitat quality.

Ecologists trying to understand the value of habitat to animals must first describe the value of resources contained in the habitat to animals and, second, they must describe spatial variation in resource quality at a resolution relevant to individual animal foraging. We addressed these issues in a study of koalas (Phascolarctos cinereus) in a Eucalyptus woodland. We measured beneficial and deterrent chemical characteristics as well as the palatability of trees using a near-infrared spectroscopic model based on direct feeding experiments.

Dugong grazing and turtle cropping: grazing optimization in tropical seagrass systems?

Grazing by dugongs and cropping by green turtles have the capacity to alter the subsequent nutritional quality of seagrass regrowth. We examined the effects of simulated light and intensive grazing by dugongs and cropping by turtles on eight nutritionally relevant measures of seagrass chemical composition over two regrowth periods (short-term, 1-4 months; long-term, 11-13 months) at two seagrass communities (a mixed species community with Zostera capricorni, Halophila ovalis, Halodule uninervis, Cymodocea rotundata and C. serrulate; and a monospecific bed of Halodule uninervis) in tropical Queensland, Australia.

Near-infrared reflectance spectroscopy is a rapid, cost-effective predictor of seagrass nutrients.

Near-infrared reflectance spectroscopy was used to analyze nutrient composition of tropical and subtropical seagrasses in Queensland, Australia, as part of a broader study of impacts of grazing by dugongs on seagrass. Seagrass samples of 10 species were collected, transported to the laboratory, and separated into leaf and root/rhizome fractions. They were dried, ground, and near-infrared spectra (400-2500 nm) were collected.

Coping with chemical complexity in mammal-plant interactions: near-infrared spectroscopy as a predictor of Eucalyptus foliar nutrients and of the feeding rates of folivorous marsupials.

We investigated the utility of near-infrared reflectance spectroscopy (NIRS) as a means of rapidly assaying chemical constituents of Eucalyptus leaves and of directly predicting the intake of foliage from individual trees by greater gliders (Petauroides volans) and common ringtail possums (Pseudocheirus peregrinus). The concentrations of total nitrogen, neutral detergent fiber, condensed tannins and total phenolics could be predicted accurately by partial least squares regression models relating the near-infrared reflectance spectra of foliage samples to analyses performed using standard laboratory procedures. Coefficients of determination (r ) for all four constituents ranged between 0.

Administration of a 5HT3 receptor antagonist increases the intake of diets containing Eucalyptus secondary metabolites by marsupials.

The effect of a naturally occurring plant phenolic constituent (the acylphloroglucinol derivative, jensenone, derived from Eucalyptus jensenii) on the food intake of two folivorous marsupials, the common ringtail (Pseudocheirus peregrinus) and the common brushtail possum (Trichosurus vulpecula) was studied. When fed diets containing varying concentrations of jensenone, both species regulated their intake of jensenone so as not to exceed a ceiling intake. This ceiling was about twice as high for common ringtails as for common brushtails from northern Australia.

Ecological applications of near infrared reflectance spectroscopy - a tool for rapid, cost-effective prediction of the composition of plant and animal tissues and aspects of animal performance.

Many ecological studies rely heavily on chemical analysis of plant and animal tissues. Often, there is limited time and money to perform all the required analyses and this can result in less than ideal sampling schemes and poor levels of replication. Near infrared reflectance spectroscopy (NIRS) can relieve these constraints because it can provide quick, non-destructive and quantitative analyses of an enormous range of organic constituents of plant and animal tissues.

Intraspecific variation in Eucalyptus secondary metabolites determines food intake by folivorous marsupials.

Traditional approaches to the question of the effects of plant secondary metabolites on the feeding choices of folivores of Eucalyptus have focused on the tree species level, although numerous field studies of foraging behaviour have identified selection at the level of the individual trees. Attempts to relate these decisions to deterrency resulting from secondary leaf chemistry have been inconclusive because assays used have focused on broad groups of compounds such as "total" phenolics. In this study we have conducted no-choice feeding trials with two arboreal mammalian folivores, the common ringtail possum (Pseudocheirus peregrinus) and the koala (Phascolarctos cinereus), to measure deterrency of individual trees of two species of Eucalyptus, E.

The effects of elevated CO atmospheres on the nutritional quality of Eucalyptus foliage and its interaction with soil nutrient and light availability.

 Seedlings of Eucalyptus tereticornis (Smith) were grown under two levels of availability each of CO (352 and 793 µmol mol), soil nutrients (1/24 and 1/4 Hoagland's solution) and light (full and 30% sunlight). Low soil nutrient availability or high light increased the C:N ratio of leaves, leading to lower leaf nitrogen concentrations, higher leaf specific weights and higher levels of both total phenolics and condensed tannins. These results were consistent with other studies of the effect of environmental resource availability on foliage composition.