Increasing river discharge to the Arctic Ocean

Synthesis of river-monitoring data reveals that the average annual discharge of fresh water from the six largest Eurasian rivers to the Arctic Ocean increased by 7% from 1936 to 1999. The average annual rate of increase was 2.0 +/- 0.7 cubic kilometers per year. Consequently, average annual discharge from the six rivers is now about 128 cubic kilometers per year greater than it was when routine measurements of discharge began. Discharge was correlated with changes in both the North Atlantic Oscillation and global mean surface air temperature. The observed large-scale change in freshwater flux has potentially important implications for ocean circulation and climate.     

Microbial community composition and carbon cycling within soil microenvironments of conventional, low-input, and organic cropping systems

This study coupled stable isotope probing with phospholipid fatty acid analysis (¹³C-PLFA) to describe the role of microbial community composition in the short-term processing (i.e., C incorporation into microbial biomass and/or deposition or respiration of C) of root- versus residue-C and, ultimately, in long-term C sequestration in conventional (annual synthetic fertilizer applications), low-input (synthetic fertilizer and cover crop applied in alternating years), and organic (annual composted manure and cover crop additions) maize-tomato (Zea mays - Lycopersicum esculentum) cropping systems. During the maize growing season, we traced ¹³C-labeled hairy vetch (Vicia dasycarpa) roots and residues into PLFAs extracted from soil microaggregates (53-250 μm) and silt-and-clay (<53 μm) particles. Total PLFA biomass was greatest in the organic (41.4 nmol g⁻¹ soil) and similar between the conventional and low-input systems (31.0 and 30.1 nmol g⁻¹ soil, respectively), with Gram-positive bacterial PLFA dominating the microbial communities in all systems. Although total PLFA-C derived from roots was over four times greater than from residues, relative distributions (mol%) of root- and residue-derived C into the microbial communities were not different among the three cropping systems. Additionally, neither the PLFA profiles nor the amount of root- and residue-C incorporation into the PLFAs of the microaggregates were consistently different when compared with the silt-and-clay particles. More fungal PLFA-C was measured, however, in microaggregates compared with silt-and-clay. The lack of differences between the mol% within the microbial communities of the cropping systems and between the PLFA-C in the microaggregates and the silt-and-clay may have been due to (i) insufficient differences in quality between roots and residues and/or (ii) the high N availability in these N-fertilized cropping systems that augmented the abilities of the microbial communities to process a wide range of substrate qualities. The main implications of this study are that (i) the greater short-term microbial processing of root- than residue-C can be a mechanistic explanation for the higher relative retention of root- over residue-C, but microbial community composition did not influence long-term C sequestration trends in the three cropping systems and (ii) in spite of the similarity between the microbial community profiles of the microaggregates and the silt-and-clay, more C was processed in the microaggregates by fungi, suggesting that the microaggregate is a relatively unique microenvironment for fungal activity.     

The effect of dietary protein on the pathogenesis of acute ovine haemonchosis

Two experiments were conducted to examine the ifluence of dietary proteins on parasite establishment and pathogenesis in Finn Dorset/Dorset Horn lambs infected with Haemonchus contortus. The lambs were introduced to high (169 g) or low (88 g crude protein (CP) kg⁻¹ dry matter (DM)) protein diets at 3 months of age and infected 1 month later with 350 larvae kg⁻¹ body weight (BW). Blood and faecal smaples were collected for analysis and body weights recorded weekly. In the first experiments some of the infected lambs were killed 6 weeks after infection and the remainder 5 weeks later. In the second experimental all the infected lambs were killed 4 weeks after infection.

The results showed that lambs on a low protein diet were less able to withstand the pathogenic effects of infection with 350 H. contortus larvae kg⁻¹ BW than lambs given the higher protein diet. Thus mortality was greater in the low protein group and adverse clinical signs, such as inappetance, weight loss and oedema were osbserved more frequently. This group also had a more severe anaemia, hypoproteinaemia and hypoalbuminnaemia than the high protein group. In contrast, faecal egg counts, total daily faecal egg output and worm burdens were similar in all groups of infected lambs, indicating that the diets did not influence parasite establishment.     

THE RESPONSE TO FERTILIZER TREATMENTS OF WINTER WHEAT GROWN AFTER LEYS

Over three years, eight replicated experiments were conducted in which winter wheat was sown after a ley with and without seedbed applications of P and K. Fertilizer N was applied at 0, 45, 90 and 135 lb per acre in one dressing in early spring. Observations were made on tiller counts, grain size and yield.
There were no significant interactions between N and mineral fertilizer. Mineral fertilizer had no important effect on tillering or grain yield. Consideration of the previous fertilization of the pastures showed that there was probably an adequate reserve of P and K in the soil, although soil analysis did not always reveal it.
Nitrogenous fertilizer significantly increased fertile tiller numbers and raised yield of grain up to an application of 45 lb N per acre in 1960 and 90 lb N per acre in 1961 (after a wet winter). The average responses to 90 lb per acre of N after leys were 74, 6·3 and 101 cwt grain per acre in 1959, 1960 and 1961, respectively. In 1961 the corresponding response in an arable field was 16·3 cwt.
It is concluded that after a well-fertilized ley neither mineral fertilizers nor N are necessary in the seed bed and that the ley contributes about 45 lb N per acre towards the succeeding crop. The practical advantages of autumn drilling without fertilizer are stressed and reference is made to the importance of considering fertilizer applications for the rotation as a whole.     

Imerslund-Grasbeck syndrome in a cross-breed dog

Imerslund-Gräsbeck syndrome is an autosomal recessive disease reported only in certain pure-breed dogs. An 18-month-old, male neutered beagle cross-breed was presented for evaluation of severe lethargy, progressive weakness and anorexia. Main clinicopathological findings included low body condition score (2.5/9), severe muscle atrophy, several neurological abnormalities, mild normochromic, normocytic, non-regenerative anaemia, severe hypocobalaminemia and mild proteinuria. Extensive diagnostic tests ruled out most of differential diagnoses for the aforementioned clinicopathological abnormalities and genetic evaluation showed that the dog was heterozygous for two previously described mutations affecting the CUBN gene, the beagle and the border collie variants. The dog showed an excellent clinical response to oral cobalamin supplementation with no relapse after 4 months. In conclusion, this case creates awareness that Imerslund-Gräsbeck syndrome should be considered even in mixed-breed dogs with compatible clinical signs and that two different pathogenic CUBN mutations in compound heterozygosity can lead to a typical Imerslund-Gräsbeck syndrome phenotype.