Effect of intensity and frequency of defoliation on aerial growth and carbohydrate reserve levels in Acacia karroo plants

Acacia karroo trees were defoliated by goats at two intensities and four frequencies; 2, 4, 8 and 12‐weekly. Leaf accumulation and carbohydrate reserve levels were compared to a non‐defoliated control, and to plants (defoliation controls) which were defoliated for the first time that season each time a frequency treatment was defoliated. These plants are activated by defoliation in such a manner that successive defoliations can result in this activation being additive. There is clearly a defoliation level below which they are not activated. Activation appears to be negated to a degree by defoliations at 2 and 4‐weekly frequencies, relative to the 8‐weekly defoliation frequency. The 12‐weekly frequency at heavy defoliation produced less than the same defoliation at 8‐weekly frequency. The 2‐weekly frequency treatments produced as much leaf as the 4 and 12‐weekly defoliations at the same defoliation intensity. The more frequently plants were defoliated, the more carbohydrate reserves dropped. However, plants adjusted to cope with very frequent defoliations. There was no connection between leaf accumulation and carbohydrate reserve levels following the different frequencies and intensities of defoliation.     

Evaluation of a technique using the carbon dioxide laser for the treatment of aural hematomas

A new technique using the carbon dioxide (CO2) laser for the treatment of aural hematomas is described. The laser is used to make an incision into the hematoma to allow for evacuation of the blood, and then multiple, small incisions are made over the surface of the hematoma to stimulate adhesions between the tissue layers. The CO2 laser was used in this fashion to treat 10 aural hematomas in eight dogs. Follow-up ranged from 1 to 23 months. Owners evaluated the cosmetic results following CO2 laser surgery as excellent in three ears, good in five ears, and fair in two ears. Hematomas were resolved in all 10 cases, although two cases developed serosanguineous fluid accumulation that required percutaneous drainage in one case and a second laser procedure in the other case.     

Second-order scattering from the sea: ten-meter radar observations of the Doppler continuum

Ten-meter radar observations of the sea have been used to study second-order interactions between waves in electromagnetic scattering from the sea. Techniques of coherent, pulsed radar provide echo frequency spectra from several range intervals. The echo spectra are resolved with an analysis window of a few millihertz. These spectra show a clear second-order echo continuum which appears as sidebands about the first-order Bragg scattering lines. Up to one-half of the total echo power has been observed in these sidebands. The principal characteristics of these sidebands vary with time, apparently in response to the sea state. The form of the echo spectra is consistent with the results of perturbation theory computations based on Rice's method.     

Effect of intensity of defoliation by goats at different phenophases on leaf and shoot growth of acacia karroo hayne

Abstract

Defoliation by goats (leaves plus shoots) during the growing phenophases resulted in a considerable stimulation of leaf and shoot growth relative to non‐defoliated plants. The response differed considerably depending on the intensity and phenophase of defoliation. Plants were most susceptible to defoliation and young shoot removal during the spring flush when carbohydrate levels were at their lowest. During the rest of the growing season carbohydrate levels were high. At these times moderate to heavy (50 % to 75 % leaf removal) defoliations resulted in the greatest leaf and shoot growth.

In contrast, the initial and continuing impact of avian and insect consumption of leaves only reduced leaf and shoot production. The stimulatory effect of defoliation in one season carried through the dormant season to the following growing season. Defoliations during the dormant season did not have any positive or negative impact on plants relative to non‐defoliated plants. Leaf and shoot material removed when the plants were growing, was replaced within weeks of defoliation.     

Immunisation against ovine caseous lymphadenitis: correlation between Corynebacterium pseudotuberculosis toxoid content and protective efficacy in combined clostridial-corynebacterial vaccines

Groups of sheep were dosed with vaccines containing Corynebacterium pseudotuberculosis toxoid combined in varying amounts with 5 clostridial antigens. Resistance of the sheep to infection with C pseudotuberculosis was tested at 1, 6 and 12 months after vaccination by infection with pus from ovine lymph glands actively infected with C pseudotuberculosis. The outcome was assessed 3 months after challenge by slaughter and inspection of the sheep for caseous lymphadenitis lesions. Protection was demonstrated by a significant reduction in the proportion of immunised sheep exhibiting lesions compared with control sheep, and by fewer abscesses in affected immunised sheep than in affected control sheep. A positive correlation was found between amount of C pseudotuberculosis toxoid administered and degree of protection obtained. Chromatographically-purified toxoid induced essentially the same protection, suggesting that anti-toxic immunity is the major factor in protection.     

Habitat amount,quality, and fragmentation associated with prevalence of the tick-borne pathogen Ehrlichia chaffeensis and occupancy dynamics of its vector,Amblyomma americanum

Landscape Ecology - Tick-borne diseases are becoming increasingly prevalent world-wide. This is likely due in part to land-cover change, particularly forest fragmentation, but this evidence is...