Nutritional Quality Of Foliage Research Articles

Foliar Nutritional Quality Explains Patchy Browsing Damage Caused by an Invasive Mammal.

Introduced herbivores frequently inflict significant, yet patchy damage on native ecosystems through selective browsing. However, there are few instances where the underlying cause of this patchy damage has been revealed. We aimed to determine if the nutritional quality of foliage could predict the browsing preferences of an invasive mammalian herbivore, the common brushtail possum (Trichosurus vulpecula), in a temperate forest in New Zealand. We quantified the spatial and temporal variation in four key aspects of the foliar chemistry (total nitrogen, available nitrogen, in vitro dry matter digestibility and tannin effect) of 275 trees representing five native tree species. Simultaneously, we assessed the severity of browsing damage caused by possums on those trees in order to relate selective browsing to foliar nutritional quality. We found significant spatial and temporal variation in nutritional quality among individuals of each tree species examined, as well as among tree species. There was a positive relationship between the available nitrogen concentration of foliage (a measure of in vitro digestible protein) and the severity of damage caused by browsing by possums. This study highlights the importance of nutritional quality, specifically, the foliar available nitrogen concentration of individual trees, in predicting the impact of an invasive mammal. Revealing the underlying cause of patchy browsing by an invasive mammal provides new insights for conservation of native forests and targeted control of invasive herbivores in forest ecosystems.

Response of larvae of <i>Cirina forda</i> Westwood (Lepidoptera: Saturniidae) to spatio-temporal variation in the nutritional content of foliage of <i>Vitellaria paradoxa</i> Gaertn. f. (Sapotaceae)

Cirina forda, an economically important edible folivore of Vitellaria paradoxa in the moist and dry woodland savanna ecosystems of Nigeria, has become ecologically restricted to the upper dry woodland savanna ecozone. The larvae of this insect are good source of protein for human and livestock consumption and income. However, little information is available on the bioecology of the insect to facilitate mass production. The study investigated, therefore, the emergence pattern and the physiological responses of the larval stages of the pest to spatial and temporal variations in the nutritional quality of foliage of the host tree, and their role in ecological adaptation of this pest. Field studies showed that the emergence pattern of C. forda is entrained to coincide with the period of abundant leaves of V. paradoxa at the beginning of the rainy season in the dry woodland savanna. Occurrence of C. forda in Nigeria has become restricted to the northernly dry woodland savanna ecosystem principally due to variation in the nutritional quality of leaf diet, and this is directly related to foliage age and geographical location of the host, V. paradoxa. Older leaves contained significantly higher (P < 0.05) micronutrients than immature leaves of the same plant, and larvae developed faster with access to foliage of different ages significantly (P < 0.05) than those fed on exclusive diets. Variation in micronutrient content and, probably, phytosterols in the leaves of different ages were suspected to be major reasons for non-survival to adult on exclusive diets. The knowledge would aid laboratory culture and management of this pest.

Influence of balsam fir (Abies balsamea) budburst phenology on hemlock looper (Lambdina fiscellaria)

Many herbivorous insects emerge synchronously with budburst of their host plant, as the nutritional quality of foliage often decreases rapidly following budburst. We carried out manipulative field experiments to evaluate the influence of bud and shoot phenology on performance of the hemlock looper, Lambdina fiscellaria Guenee (Lepidoptera: Geometridae: Ourapterygini), on balsam fir, Abies balsamea (L.) Mill. (Pinaceae), in NF, Canada. Hemlock looper survival, pupal weight, and realized fecundity, which were then combined to estimate fitness, were all highest when newly emerged first instars were placed on foliage of current-year shoots that had completed approximately 25―35% of their elongation, and lower when placed on younger or older foliage. Survival of a small portion of larvae placed on buds a week before budburst suggests that newly emerged first instars either entered unburst buds or survived for a week without food. In laboratory experiments, approximately half of larvae survived for 4 days without food or water at 10 °C and 65% r.h. The timing of egg hatch in the field appeared to be adaptive, but the short duration of egg hatch suggests that another factor in addition to host plant phenology exerts stabilizing selection pressure on the timing of egg hatch.

Foliar Concentration of a Single Toxin Creates Habitat Patchiness for a Marsupial Folivore

We examined intraspecific variation in susceptibility to herbivory by common ringtail possums (Pseudocheirus peregrinus) for two species of Eucalyptus, (E. polyanthemos and E. sideroxylon) and the chemical basis for that variation. Using a no-choice protocol, we observed dry matter intakes by common ringtail possums ranging from 3.28 to 44 g·(kg body mass)−0.75·d−1 for E. polyanthemos and from 2.4 to 67 g·(kg body mass)−0.75·d−1 for E. sideroxylon. We investigated, using correlative analyses, the relationships between dry matter intake and a range of foliage chemical characteristics, including measures of nutritional quality (total nitrogen, cellulose, hemi-cellulose, lignin, in vitro dry matter digestibility) and plant secondary chemistry (total phenolics, condensed tannins, cyanogenic glycosides, terpenes, and sideroxylonal, a recently identified Eucalyptus toxin). Significant relationships were identified only for terpenes (and 1,8-cineole in particular) and sideroxylonal. Bioassay experiments confirmed that the foliar concentration of sideroxylonal alone was sufficient to explain the variation observed. To undertake a field study of variation in foliar sideroxylonal and dry matter intake by possums of E. polyanthemos, we developed calibrations of both variables against the near infrared spectra of foliage samples. Acceptable calibration equations were developed, and we applied these to samples collected from a number of E. polyanthemos individuals within an area approximating the home range size of common ringtail possums. We found that foliar sideroxylonal varied from nil to 12.6 mg/g, while predicted dry matter intakes by possums ranged from nil to 42.8 g·(kg body mass)−0.75·d−1. We conclude that significant patchiness in nutritional quality of foliage, resulting from variation in foliar concentrations of a single compound, exists at a scale relevant to the feeding decisions of individual animals.

FOLIAR CONCENTRATION OF A SINGLE TOXIN CREATES HABITAT PATCHINESS FOR A MARSUPIAL FOLIVORE

We examined intraspecific variation in susceptibility to herbivory by common ringtail possums (Pseudocheirus peregrinus) for two species of Eucalyptus, E. polyanthemos and E. sideroxylon, and the chemical basis for that variation. Using a no-choice protocol, we observed dry matter intakes by common ringtail possums ranging from 3.28 to 44 g.kg body mass-0.75.d-1 for E. polyanthemos and 2.4 to 67 g.kg body mass-0.75.d-1 for E. sideroxylon. We investigated, using correlative analyses, the relationships between dry matter intake and a range of foliage chemical characteristics, including measures of nutritional quality (total nitrogen, cellulose, hemi-cellulose, lignin, in vitro dry matter digestibility) and plant secondary chemistry (total phenolics, condensed tannins, cyanogenic glycosides, terpenes and sideroxylonal, a recently identified Eucalyptus toxin). Significant relationships were identified only for terpenes (and 1,8-cineole in particular) and sideroxylonal. Bioassay experiments confirmed that the foliar concentration of sideroxylonal alone was sufficient to explain the variation observed. To enable a field study of variation in foliar sideroxylonal and dry matter intake by possums of E. polyanthemos, we developed calibrations of both variables against the Near Infrared spectra of foliage samples. Acceptable calibration equations were developed and we applied these to samples collected from a number of E. polyanthemos individuals within an area approximating the home range size of common ringtail possums. We found that foliar sideroxylonal varied from nil to 12.6 mg/g, and predicted dry matter intakes by possums ranged from nil to 42.8 g.kg body mass-0.75.d-1. We conclude that significant patchiness in nutritional quality of foliage, resulting from variation in foliar concentrations of a single compound, exists at a scale relevant to the feeding decisions of individual animals.

Dieback of rural eucalypts: the effect of stress on the nutritional quality of foliage

Abstract Canopy dieback of Eucalyptus blakelyi trees is often associated with defoliation by insects: the foliage of trees with dieback is nutritionally superior for insects and is more heavily damaged by them. I investigated whether differences in the nutritional quality of foliage were genetically determined, or caused by environmental stress. In a series of glasshouse experiments, with seedlings and grafted plants derived from dieback and healthy populations of trees. I tested the influence of deprivation of nutrients, drought, waterlogging, saline waterlogging and addition of excess phosphate, on the nutritional quality of foliage. Differences in the foliar properties of plants from different genetic sources were not consistent with the differences between the source populations. Most of the environmental stresses applied caused a reduction in foliar quality (decreased water and nitrogen contents, and increased specific leaf weights). I hypothesize that the enhanced nutritional quality of the foliage of dieback trees is more likely to be a consequence of benign growing conditions (e.g. improved soil fertility) than of environmental stress. Field data for soil properties and the effect of drought on mature trees are consistent with this view.