Correlation between mite community structure and gross N fluxes     

Graham H.R Osler  Sylvie Recous  Ian R.P Fillery  Chunya Zhu 《Soil biology & biochemistry》2004,36(1):191-194

Net nitrogen (N) mineralisation rate is the result of two independent processes: gross N mineralisation and N immobilisation. Techniques for determining these rates have only been developed recently and no studies have examined the relationship between soil fauna and these two components of net N mineralisation. We present data which demonstrates that mite community structure, described using the Shannon index, is correlated with gross N immobilisation rates in the Western Australian wheat belt. These results suggest that examining the impacts of mites on gross N fluxes is warranted.  相似文献   

Sample size calculations for studies designed to evaluate diagnostic test accuracy     

Adam J. Branscum  Wesley O. Johnson  Ian A. Gardner 《Journal of Agricultural, Biological & Environmental Statistics》2007,12(1):112-127

We developed a Bayesian approach to sample size calculations for cross-sectional studies designed to estimate sensitivity and specificity of one or more diagnostic tests. Sample size calculations can be made for common study designs such as one test in one population, two conditionally independent or dependent tests in ≤2 populations, and three tests in ≤2 populations. We determine a sample size combination that yields high predictive probability, with respect to the future study data, of accurate and precise estimates of sensitivity and specificity. We also consider hypothesis testing for demonstrating the superiority or equivalence of one diagnostic test relative to another. The predictive probability can also be computed when the sample size combination is fixed in advance, thereby providing a “power-like” measure for the future study. The method is straightforward to implement using the S-Plus/R library emBedBUGS together with WinBUGS.  相似文献   

A review of some problems of tropical marine conservation with particular reference to the Tanzanian coast     

Ian Bryceson 《Biological conservation》1981,20(3):163-171

The productivity, diversity and susceptibility to stress of tropical marine communities are compared with those of temperate marine communities. The question of the i importance of conservation is raised.The applicability of island biogeographical theories in relation to the design of marine reserves is briefly reviewed. It is suggested that the contention that conservation areas should always consist of the largest possible single area is not necessarily correct for the tropical marine environment.Conservation problems of particular habitats within Tanzanian coastal waters are detailed with special reference to the following: coral reefs, rocky intertidal platforms, cliffs, sandy beaches, sandy-muddy tidal flats, seagrass beds, mangroves, estuaries and small islands. The plight of some endangered species is discussed.Conclusions are drawn regarding the present status of marine conservation in Tanzania.  相似文献   

Effects of disturbance on population dynamics of the threatened orchid Prasophyllum correctum D.L. Jones and implications for grassland management in south-eastern Australia     

Fiona Coates  Ian D. Lunt 《Biological conservation》2006,129(1):59-69

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A review of lead poisoning from ammunition sources in terrestrial birds     

Ian J. Fisher  Deborah J. Pain 《Biological conservation》2006,131(3):421-432

Poisoning from lead shot in waterbirds has been well documented globally and, in some countries, legislation exists to combat lead toxicosis at wetlands and/or in waterbirds. However, poisoning of terrestrial species such as raptors and upland game birds, while of potential conservation concern, remains largely to be addressed. For several species, shot are not the only ammunition source of lead, as bullet fragments can be ingested from hunter-killed animal carcasses and gut piles left in the field. This review collates the current knowledge of lead poisoning from ammunition in non-waterbirds. Fifty-nine terrestrial bird species have so far been documented to have ingested lead or suffered lead poisoning from ammunition sources, including nine Globally Threatened or Near Threatened species. We discuss the conservation significance of continued lead use, and detail measures needed to combat lead poisoning.  相似文献   

Landscape-scale species richness of earthworms in the Porongurup Range,Western Australia: influence of aspect,soil fertility,and vegetation type     

Allan?WillsEmail author  Ian?Abbott 《Biology and Fertility of Soils》2003,39(2):94-102

Indigenous Australian earthworms comprise a patchily collected taxon that is likely to have high diversity and pose difficulties for systems of biodiversity prediction or monitoring that use surrogates. This is because surrogates for earthworm diversity have scarcely been identified at landscape scales in Australian contexts. In the present paper we examine the diversity of earthworms in a 26 km² remnant of native vegetation. Comparison of diversity within the Porongurup Range to diversity of other earthworm faunas demonstrates the sampling intensities required to adequately sample regions of 10⁰–10¹ km². In addition diversity patterns were examined in relation to habitat as described by landscape context, vegetation cover and soil characteristics. Species accumulation in samples from the northern aspect of the Porongurup Range was less than expected from a random distribution of species. Combined Karri-, and Marri- and Karri-vegetated sites supported significantly more earthworm species on the southern aspect of the Porongurup Range than expected from accumulation in randomly ordered samples. Sites carrying Jarrah as the only dominant canopy had fewer earthworm species than would be expected from accumulation in randomly ordered samples. Jarrah overstorey sites and southern aspect Karri sites correspond to extremes in a continuum of soil and landscape characteristics. Earthworm responses to landscape and vegetation units in the region warrant further investigation.  相似文献   

Preferred age for assessment of qualitative and quantitative characteristics of the essential oil of tea tree (Melaleuca alternifolia) seedlings prior to plantation establishment     

Russell MF  Southwell I 《Journal of agricultural and food chemistry》2003,51(15):4254-4257

An analytical method for determining the quality and hence the chemical variety status of tea tree transplants is described. The key to the procedure was found to be the leaf age of the test material. Investigation at very early development stages was seen to give misleading results due to the sequential onset of different monoterpenoid biogenetic pathways. For example, in the first few leaves, the high concentration of terpinolene in the terpinen-4-ol variety suggests that the terpinolene variety is under investigation. However, 1,8-cineole percent concentrations in plantation tree leaf were approximately 1.6 times lower than those measured for seedlings prior to transplant. Consequently, the use of a plantation cineole indicator is proposed for estimating plantation cineole from seedling leaf analyses. Although recent investigations enable the chemotype status to be predicted with some certainty, it is now proposed that analysis of leaf set 10 at the age of 6 weeks (seedling age approximately 17 weeks) provides an unambiguous analysis and correlates seedling quality with mature plantation quality. In addition, the oil yield of mature tea tree leaf was found, by steam distillation, to be approximately 5 times higher than that of seedling leaf.  相似文献   

A model system study of the inhibition of heterocyclic aromatic amine formation by organosulfur compounds     

Shin HS  Strasburg GM  Gray JI 《Journal of agricultural and food chemistry》2002,50(26):7684-7690

Organosulfur compounds and sodium bisulfite significantly inhibited (P < 0.05) heterocyclic aromatic amine (HAA) formation in model systems containing phenylalanine, creatinine, and glucose. There was, however, no inhibition by the same compounds in a model system containing only phenylalanine and creatinine. Diallyl disulfide (DAD) and dipropyl disulfide (DPD) concentrations in the model systems were significantly decreased (P < 0.05) after heating for 10 min at 180 degrees C. Only very low concentrations of sulfhydryl groups (4.19 and 4.00 micromol) were produced on heating DAD and DPD for 30 min. Reaction of glucose and DAD produced several sulfur-containing compounds. After 10 min of heating at 180 degrees C, HAA formation in the control model systems was increased significantly, and DAD was an effective inhibitor during this heating period. Tetrahydrothiophene-3-one (THT) and tetrahydrothiophene (THP); two products resulting from the interaction of glucose and DAD, had no direct influence on HAA formation in the model systems.  相似文献   

Formation of sulfur aroma compounds in reaction mixtures containing cysteine and three different forms of ribose   总被引：6，自引：0，他引：6  

Mottram DS  Nobrega IC 《Journal of agricultural and food chemistry》2002,50(14):4080-4086

The headspace volatiles produced from buffered and unbuffered cysteine model systems, containing inosine 5'-monophosphate, ribose 5-phosphate, or ribose, were examined by GC-MS. Sulfur compounds dominated the volatiles of all systems and included mercaptoketones, furanthiols, and disulfides. The inosine monophosphate systems produced much lower quantities of volatiles than ribose phosphate or ribose systems. In the systems buffered with phosphate or phthalate buffers, both ribose and ribose phosphate systems gave similar quantities of sulfur volatiles. However, in the absence of buffer, the ribose system was relatively unreactive, especially for volatiles formed via the 2,3-enolization route in the Maillard reaction, where 4-hydroxy-5-methyl-3(2H)-furanone is a key intermediate. A number of keto-enol tautomerisms, which are known to be acid-base-catalyzed, occur in the 2,3-enolization route. This may explain the catalysis of the ribose systems by the buffers. In the ribose phosphate systems, however, Maillard mechanisms probably played a less important role, because ribose 5-phosphate readily dephosphorylated to give 4-hydroxy-5-methyl-3(2H)-furanone on heating and thus provided an easier route to aroma compounds than the Maillard reaction.  相似文献   

Density and composition of aquatic oligochaete populations in different farmers' ricefields     

Ian C. Simpson  Pierre A. Roger  Roberto Oficial  Ian F. Grant 《Biology and Fertility of Soils》1993,16(1):34-40

Summary The density and composition of ricefield oligochaete populations were estimated in 33 farmers' fields in the Philippines and related to physicochemical properties of the soils and agrochemical use. The spatial distribution of organisms and the investigative sampling strategy were determined from a high-intensity sampling in a single ricefield. Species diversity was low. The dominant species were Limnodrilus hoffmeisteri and Branchiura sowerbyi. The spatial distribution of populations was contagious and densities ranged from 0 to 35 000 m^-2 (maximum 620 kg ha^-1). Mean population density was positively correlated with soil moisture, organic matter, and the quantity of N fertilizer applied. No pesticide impacts were observed.  相似文献