Specific gravity responses of slash and loblolly pine following mid-rotation fertilization

Wood quality attributes were examined in six stands of slash pine (Pinus elliottii Engelm. var. elliottii) and loblolly pine (P. taeda L.) in the lower Coastal Plain of Georgia and Florida. Several plots comprised each stand, and each plot was divided so that it received three fertilizer treatments: a control treatment with herbaceous weed control at planting and brush control at mid-rotation only (control); 45 kg ha⁻¹ N + 56 kg ha⁻¹ P + herbaceous weed control at planting and 224 kg ha⁻¹ N + 45 kg ha⁻¹ P + brush control at mid-rotation (fertilizer with N at planting); and 56 kg ha⁻¹ P + herbaceous weed control at planting and 224 kg ha⁻¹ N + 45 kg ha⁻¹ P + brush control at mid-rotation (fertilizer without N at planting). Ring width, ring earlywood specific gravity (SG), ring latewood SG, whole ring SG, and ring percent latewood were measured on each of seven trees. Of these measurements, this study focused mainly on the properties related to SG. Examination of the rings showed that latewood SG was significantly lower in trees treated with fertilizers with and without N at planting in the two to three years following fertilization, but that latewood SG gradually returned to a level similar to the control. Fertilizer without N at planting may also have had a brief negative effect on earlywood SG following mid-rotation fertilization, but it was not as clear or lasting as the effect on latewood SG. Additionally, although slash and loblolly pine appear to differ in the developmental patterns of these SG properties, there were no significant differences in how these patterns interacted with treatment. This study demonstrated that fertilization treatments have similar short-term effects on the SG of slash and loblolly pines, particularly in latewood, but the trees will return to a SG pattern consistent with unfertilized trees within two or three years.     

Estimates of Heritability of Larval and Early Juvenile Growth Traits in Red Drum (Sciaenops ocellatus)

ABSTRACT

Eighteen to 29 families of red drum were generated via spontaneous spawning of multiple sets of three dams?×?two sires. In 2002, offspring from spawning events were grown in separate larval ponds to a mean TL of 30.4 mm. In 2003, offspring from spawning events were individually passive integrated transponder (PIT)-tagged and grown in “common-garden” tanks from 121.9 to 166.6 mm. Offspring in both experiments were assigned to parents based on genotypes at four microsatellite loci. Heritability estimates were 0.24?±?0.06 (larval TL) and 0.48?±?0.16 (juvenile-specific growth rate in length) and indicate a significant genetic component for both traits.     

Dietary effect of squid and fish meals on growth and survival of Pacific white shrimp Litopenaeus vannamei in the presence or absence of phytoplankton in an indoor tank system

This study was conducted in 36 indoor 40‐L fibreglass aquaria to determine the weight gain and survival of Litopenaeus vannamei fed different dietary levels of fish (FM) and squid meal (SM) and to evaluate the potential of phytoplankton to reduce FM and SM levels in shrimp feeds. Six experimental isonitrogenous (35% protein) and isocaloric (17.5 kJ g^?1) diets were formulated to contain either 5%, 10% or 20% SM combined with either 6.5% or 12% FM. Dietary effects on growth and survival were compared in two systems: a ‘CLEAR water system’ (CWS) without the presence of microalgae and a ‘GREEN water system’ (GWS) with microalgae in the culture water. Shrimp cultured in the GWS had 28–57% greater weight gain than those cultured in the CWS, regardless of dietary treatment. However, survival was not different. Shrimp cultured in the CWS or the GWS, and fed diets containing combinations of FM and SM did not show differences in weight gain and feed conversion ratio. These results suggest that under the conditions existing during this research, 6.5% FM and 5% SM can be used as a cost‐effective combination in commercial feeds for shrimp production and that growth can be enhanced in the presence of primary productivity.     

Importance of habitat type classifications for predicting ruffed grouse use of areas for drumming

To incorporate ruffed grouse (Bonasa umbellus) habitat planning in forest management, it is necessary for managers to understand factors contributing to grouse habitat use. Previous studies examining ruffed grouse drumming habitat documented relationships between drumming grouse and broad vegetation categories (e.g., northern hardwoods, young aspen [Populus spp.], oak [Quercus spp.]), but few studies have documented how drumming grouse respond to ecological variations in site conditions of aspen or other vegetation types that might be used. Our objectives were to determine the utility of habitat type classifications in predicting the occurrence of ruffed grouse drumming habitat in the western Upper Peninsula of Michigan, and demonstrate how classifications may be used to understand how forest management may affect ruffed grouse habitat. We used survey routes on state land and conducted drumming surveys during mid-April and early May at 78 points in 2005 and 2006. We recorded the number of drumming males heard at each point, the azimuth to where the grouse was heard, and a qualitative measure of distance to determine in which forest stands grouse were drumming. Using GIS, we determined the specific vegetation type, age class, and habitat type, evaluated habitat suitability, and determined a suitability score for areas in which grouse were drumming. We constructed a logistic regression model that calculated the probability of grouse use of areas for drumming based on vegetation characteristics at used and random locations. Our results indicated that the probability of grouse use of an area for drumming is based on inherent site characteristics (i.e., habitat type) and habitat suitability. The model is useful for planning forest management activities and understanding how grouse may respond to spatial or temporal changes in vegetation through succession or manipulation.     

Effects of dietary supplementation of a commercial prebiotic Previda® on survival,growth, immune responses and gut microbiota of Pacific white shrimp,Litopenaeus vannamei

A 35‐day feeding trial was conducted to evaluate growth, bacterial populations of the gastrointestinal tract (GIT) and immune responses of Litopenaeus vannamei fed diets containing the commercial prebiotic Previda^®. Diets were formulated to contain Previda^® at 0, 0.2, 0.5, 1.0 or 1.6 g kg^?1 by weight. At the end of the study, differences in weight gain and survival among treatments were not significant (P > 0.05), but denaturing gradient gel electrophoresis analysis revealed that the microbial communities in the GIT changed significantly with the inclusion of dietary Previda^® at different levels. Previda^® was therefore able to selectively modify the microbial communities in the shrimp's GIT. Although individual bacterial species were not identified, enteric populations in shrimp fed the prebiotic at similar levels of inclusion were genetically similar. In addition, shrimp fed Previda^® at 1.6 g kg^?1 responded significantly (P < 0.05) better immunologically with respect to hemocyte phagocytic capacity, haemolymph protein, hyaline cell counts and haemolymph glucose compared with shrimp fed the basal diet. Although shrimp were not exposed to virulent pathogens in this study, the observed upregulation of some of imm‐une responses upon prebiotic supplementation indicates that an improved outcome of such challenges may be anticipated in Previda^®‐fed shrimp under commercial conditions.     

Effects of a Simulated Agricultural Runoff Event on Sediment Toxicity in a Managed Backwater Wetland

We examined the effects of an amended mixture of three pesticides, atrazine (72.7?g), S-metolachlor (54.5?g), and permethrin (both cis and trans isomers; 11.4?g), on 10-day sediment toxicity to Hyalella azteca in a managed natural backwater wetland after a simulated agricultural runoff event. Sediment samples were collected at 10, 40, 100, 300, and 500?m from inflow 13?days prior to amendment and 1, 5, 12, 22, and 36?days post-amendment. Background pesticide concentrations ranged from <1 to 977, <1 to 119, and <1 to 2???g?kg^?1, for atrazine, S-metolachlor, and permethrin, respectively. Average post-amendment atrazine and S-metolachlor were 2,915?C3,927 and 3?C20???g?kg^?1, respectively at 10?C40?m and 538?C872 and <1???g?kg^?1, respectively at 300?C500?m. Average post-amendment permethrin was 65?C200???g?kg^?1 at 10?C40?m and 1?C10???g?kg^?1 at 300?C500?m. H. azteca 10-day survival varied spatially and temporally up to 100?m from inflow. Animal growth, independent of survival, was reduced 40 and 100?m from inflow on day?36, showing continued sediment toxicity of up to 100?m from inflow more than 1?month after amendment. Animal survival and growth were unaffected at 300 and 500?m from inflow throughout the study period. Correlations of pesticide concentrations and H. azteca responses indicated that observed sediment toxicity was primarily from permethrin with potential additional synergistic toxicity from atrazine and methyl parathion. Study results indicate that natural backwater wetlands can be managed to ameliorate pesticide mixture 10-day sediment toxicity to H. azteca within 300?m of inflow and smaller wetlands (??100?m) may require several months of effluent retention to mitigate effects.     

Growth and mineral nutrition of cattails inhabiting a thermally‐graded South Carolina reservoir: I. Growth and the macronutrients 1

Growth and macronutrient uptake in two species of cattail, Typha latifolia and T. domingensis, were determined during an annual growth cycle in Par Pond, a thermally‐graded nuclear reactor cooling reservoir in South Carolina. Shoots of the same age class were sampled periodically from the initiation of growth in early spring to senescence in late autumn. Although differences between thermal regimes were mostly statistically non‐significant, growth and macronutrient uptake, especially of N, P, and K, tended to be enhanced by elevated water temperatures. The pattern for growth and N, P, and K uptake in decreasing order were: “Warm”; > “Intermediate”; > “Ambient”; regimes. The non‐significant statistics were attributed to large between‐stand and between‐temperature regime variations. Both Typha species exhibited sharp declines in N, P, and K concentrations in the shoots, and some decline in the rhizomes, early in the growing season, followed by either a more gradual decline or leveling off of concentrations until senescence. Calcium in shoots of both species increased with season, whereas Mg remained fairly constant. Thermal effluents can alter the growth form of Typha, as confirmed by the elimination of T. domingensis in the “Warm”; regime, and can affect their mineral nutrition.     

Effect of nitrogen form during the flowering period on zucchini squash growth and nutrient element uptake

Zucchini squash (Cucurbita pepo L. cv. Green Magic) plants were grown hydroponically with nitrate (NO₃):ammonium (NH₄) ratio of 3:1 until the onset of flowering when the plants were assigned to four NO₃:NH₄ ratio (1:0, 1:1, 1:3, or 3:1) treatments. Changing the original nitrogen (N) form ratio significantly affected plant growth, fruit yield, nutrient element, and water uptake. Growth of plants was better when NO₃‐N (1:0) was the sole form of N than when NH₄‐N was part of the N treatment. Fruit yields for plants fertilized with 1:0 or 1:3 N‐form ratio were double those of plants grown continuously with 3:1 N ratio. The largest leaf area and plant water use were obtained with 1:0 N ratio treatment Total uptake of calcium (Ca), magnesium (Mg), and potassium (K) decreased with increasing NH₄‐N proportion in the nutrient solution which suggest NH₄‐N was competing with these cations for uptake. The results also demonstrated that growers may increase fruit yield by using a predominantly NO₃‐N source fertilizer through the vegetative growth stage and by shifting the NO₃:NH₄ ratio during the reproductive phase.