Prescribed fire,snag population dynamics,and avian nest site selection

Snags are an important resource for a wide variety of organisms, including cavity-nesting birds. We documented snag attributes in a mixed-conifer forest dominated by ponderosa pine in the Sierra Nevada, California where fire is being applied during spring. A total of 328 snags were monitored before and after fire on plots burned once, burned twice, or left unburned to assess the effects of prescribed fire on snag populations. The greatest loss of snags (7.1 snags ha⁻¹ or 43%) followed the first introduction of fire after a long fire-free period. On plots burned a second time 21% of snags (3.6 snags ha⁻¹) were lost, whereas 8% (1.4 snags ha⁻¹) were lost on unburned control plots in the same time period. New snags replaced many of those lost reducing the net snag losses to 12% (2.0 ha⁻¹) for plots burned once, and 3% (0.5 ha⁻¹) for plots burned twice and unburned plots. We also examined snags used by cavity-nesting birds. Snags preferred for nesting were generally ponderosa pine (Pinus ponderosa), larger diameter, and moderately decayed as compared to available snags. For monitored snags that met the preferred criteria, there was a net loss (1.7 snag ha⁻¹ or 34%) after the first burn, while the loss of useable snags was less than 1 snag ha⁻¹ following the second burn (15%) or on unburned controls (8%). We recommend protection of preferred snags, in particular large ponderosa pines, especially during primary fire applications on fire-suppressed landscapes.     

Response of Mycorrhizal Infection to Glyphosate Applications and P Fertilization in Glyphosate-Tolerant Soybean,Maize, and Cotton

Glyphosate and phosphorus (P) fertilizer may alter arbuscular mycorrhizal (AM) fungal infection rates of glyphosate-tolerant cotton, maize, and soybean in low-P soil. Microbial biomass, water soluble P, Mehlich-3 P, and acid and alkaline phosphatase activities were not significantly impacted by glyphosate or P in the greenhouse. Phosphorus fertilization decreased mycorrhizal infection rates in cotton and maize and increased shoot biomass and shoot P in soybean in 2005, and decreased mycorrhizal infection in soybean and increased shoot biomass in cotton and maize and shoot P in all three crops in 2006. In pasteurized soil, glyphosate decreased percent mycorrhizal infection in maize, increased infection in cotton, and did not significantly affect infection in soybean. When soil was not pasteurized, glyphosate did not significantly alter mycorrhizal infection in any crop. The potential for glyphosate to alter AM fungal infection in glyphosate-tolerant plants may depend on whether soil microbial communities are compromised by other factors.     

Aerial canopy temperature differences between fast‐ and slow‐wilting soya bean genotypes

Drought stress limits crop growth and yield in soya bean (Glycine max [L.] Merr.), but there are relatively few tools available to assess the ability of different genotypes to tolerate drought. Aerial infrared image analysis was evaluated as a potential tool for identifying drought tolerance in soya bean. Drought effects were evaluated from late vegetative to mid‐reproductive stages of soya bean development in an experiment with ten genotypes including five slow‐ and five fast‐wilting genotypes that were from a population derived from Benning×PI416937. There were two deficit irrigation levels for 2 years and one deficit irrigation level for the third year along with a fully irrigated control level. When the canopy was completely closed, relative canopy temperature was determined using an infrared camera taken from an aerial platform 50–75 m above the experiment. As water availability decreased, the relative canopy temperature generally increased. Moreover, slow‐wilting soya bean genotypes generally had lower canopy temperature compared to fast‐wilting genotypes, and grain yield was generally positively associated with cool canopy temperatures. The results indicate that the determination of canopy temperature is a promising tool for rapid characterization of drought‐related traits in soya bean.     

Presumed case of "stiff-horse syndrome" caused by decreased gamma-aminobutyric acid (GABA) production in an American Paint mare

Glutamic acid decarboxylase (GAD) converts glutamic acid into the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Increased serum GAD (auto) antibody concentrations were found in a mare with increased postural musculature tone resulting in stiffness and recumbence. The mare was treated with dexamethasone which resulted in resolution of clinical signs and decreased GAD antibody concentrations.