Nutrient variability

There are many possible causes of chemical and nutrient variability in tree tissues (27,28) which result in a wide range of spatial arrays of suitable and unsuitable food for insects (29). Although large-scale spatial variation may influence insect host race formation and have interesting consequences for insect biogeography and host race formation (30), the scale of variation with which the individual insect deals most often is more local, on the individual tree or tissue basis. 

Knott, J., Shurson, J., and Gohil, J. (2003), Effects of the Nutrient Variability of Distiller s Solubles Within Ethanol Plants and the Amount of Distiller s Solubles Blended With Distiller s Grains on Fat, Protein and Phosphorus Content ofDDGS, (Website http // www.ddgs.umn.edu/research-quality/nutrientvariability.pdf). Department of Animal Science University of Minnesota. Last modified 9/11/03. 

In order to estimate paleoceanographic nutrient levels, and thereby explore links between nutrient variability, atmospheric CO2 and climate change, a range of nutrient proxies have been developed. The ratio of cadmium (Cd) to calcium (Ca) in benthic foraminifera has been used as a proxy for dissolved phosphate, based on the observation that dissolved cadmium and phosphate concentrations are linearly correlated in modern oceanic waters (Boyle, 1988). While the basis of the Cd PO4 relationship is not understood, from either a biochemical or geochemical standpoint (e.g., Cullen et al., 2003),... 

With recent emphasis on conducting chronic bioassays sometimes at low concentration ranges of the test compound, the question of toxicant and nutrient variability of commercial laboratory animal diets has been extensively examined at NCTR over the last five years (2, 3.). The animal diet must be considered an important... 

A recent review of research on phosphorus input to surface waters from agriculture highlights the variability of particulate and dissolved phosphorus contributions to catchments. The input varies with rainfall, fertilizer application rates, the history of the application of the fertilizer, land use, soil type, and between surface and sub-surface water. The balance struck between export of nutrients from the catchment and recipient-water productivity is the primary factor which controls its quality. 

Some variables such as temperature, pH, nutrient medium, and redox potential are favorable to certain organisms while discouraging the growth of others. The major characteristics of microbial processes that contrast with those of ordinary chemical processing include the following [1] ... 

The fed bateh reaetor (FBR) is a reaetor where fresh nutrients are added to replaee those already used. The rate of the feed flow U may be variable, and there is no outlet flowrate from the fermenter. As a eonsequenee of feeding, the reaetor volume ehanges with respeet to time. Figure 11-22 illustrates a simple fed-bateh reaetor. The balanee equations are ... 

Complex nutrients, such as yeast extract, are variable in composition and consequently it is difficult to maintain process reproducibility within the narrow window required to produce a product of consistent quality. 

Culture with continuous nutrient supply can be operated in two modes (i) variable volume (ii) fixed volume. 

The maximum temperature and duration of heating during fires are important variables that influence the soil nutrient status, as well as the survival of residual vegetation following fire (Table III). Deforestation results in the presence of large quantities of wood debris in close proximity to the soil surface. Fires in this scenario result in soil temperatures and magnitudes of heat flux far in excess of those which occur in fires in uncut forests (Shea, R. W. Oregon State University, unpublished data). 

Silicic acid (H4Si04) is a necessary nutrient for diatoms, who build their shells from opal (Si02 H20). Whether silicic acid becomes limiting for diatoms in seawater depends on the availability of Si relative to N and P. Estimates of diatom uptake of Si relative to P range from 16 1 to 23 1. Dugdale and Wilkerson (1998) and Dunne et al. (1999) have shown that much of the variability in new production in the equatorial Pacific may be tied to variability in diatom production. Diatom control is most important at times of very high nutrient concentrations and during non-steady-state times, perhaps because more iron is available at those times. 

The second case (Table 2) illustrates a hypothetic urban stream receiving both metals and nutrients mainly via urban runoff. Since urban runoff is directly linked with rainfall episodes, metal inputs and exposure will be variable under base-flow during a rainy period and very low under a situation of water scarcity (low rain and low-flow). In this case, a sudden flow increase after strong rains may cause contrasting effects on water metal transport depending on the previous situation. If previous rains have already washed the metals retained in land and sediments, the... 

Fig. 1 Results from a redundancy analysis of stream nutrient concentrations vs. catchment characteristics in 31 headwater catchments in Catalonia (Spain). Note how phosphorus (SRP) and ammonium (NH4) appear associated with urban point and diffuse sources (Urban percent urban land use, Inhabs number of inhabitants, eq. inhab inhabitant equivalents), whereas nitrate (NO3) concentration is positively associated with irrigated agriculture (IrrAg) and bovine cattle units (ECU), and negatively with mean catchment slope (slope) and percent forest land (Forest). The other variables are Area log area, P precipitation, NonIrrAg non irrigated agriculture. Data are from the Catalan water agency (http //ww.gencat.cat/ac)...

A number of factors described as influencing carotenoid bioavailability were regrouped under the SLAMENGFll mnemonic. Species of carotenoid. Linkages at molecular level. Amount of carotenoids consumed in a meal. Matrix in which the carotenoid is incorporated. Effectors of absorption and bioconversion. Nutrient status of the host. Genetic factors. Host-related factors, and Interactions among these variables. Only the factors that affect the micellarization of the compound in the gut are discussed and summarized in Table 3.2.1. 

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