Birch invasion of heather moorland increases nematode diversity and trophic complexity

To determine whether successional changes in plant communities may influence belowground community structure, we quantified nematode abundance, trophic structure and diversity along two separate chronosequences from heather moorland to birch woodland in the Scottish uplands. Tree invasion markedly altered plant community composition, and hence litter inputs, both directly, and indirectly through changes in understorey species. In turn, these changes in detrital inputs were reflected in consistent changes in nematode community structure. Nematode abundance increased from moorland to birch woodland, with moorland soils being dominated by a few taxa, notably root-hair and fungal feeders, compared to the more diverse composition of the birch woodland soils. Trophic structure was altered through an increase in the abundance of bacterial feeding relative to fungal-feeding nematodes, and an increase in the abundance of predatory nematodes. The increase in predators during the succession from moorland to woodland was associated with an increase in soil pH, highlighting that not only changes in the plant community, but also changes in soil properties associated with tree invasion may influence soil nematodes. Nematode diversity increased from moorland to birch woodland, with nematode richness being positively related to both plant species richness and soil pH. These results suggest that trees may control soil community structure through the manipulation of resources and the soil physico-chemical environment, promoting greater nematode diversity and trophic complexity.     

The dynamic nature of plant-available manganese during storage of a calcareous soil

Summary The effect of length of dry storage period and subsequent moist incubation on the availability of Mn was examined in a calcareous soil. Increasing the time of dry storage (for up to 4 years) generally increased the availability of Mn as determined by plant growth and Mn concentration in wheat and barley. Moist incubation of stored soil had variable effects on Mn availability depending on how long the soil had been stored before use and on the method used to assess Mn availability. When assessed by Mn concentration in plant tissues, increasing the moist incubation time (from 0 to 30 days) of soil stored dry for 4 years increased Mn availability in soil initially and thereafter decreased it. However, incubation time had little effect on Mn availability in soil stored for only 1 year or soil used fresh from the field. When Mn availability was assessed using a chemical extractant (DTPA; diethylenetriaminepentaacetic acid), both soils showed an initial increase in Mn availability immediately on wetting. However, Mn availability in the soil stored for only 1 year decreased rapidly and remained consistently below that of soil stored for 4 years. In the latter soil, Mn availability also decreased but only after a few days. Microbial studies indicated that there was a decrease in the ratio of Mn oxidising to Mn reducing microorganisms with increasing storage time. Inoculation of one soil with another suggested that the factor responsible for the low Mn availability in soils stored for a short period could be transferred to soils stored for a longer period. These results suggest that the change in Mn availability in a calcareous soil with dry storage is a result of changes in microbial populations that cannot be fully restored by moist incubation.     

“家禽微量元素营养”专栏四：确定现代肉鸡的微量元素需要量

在过去50年中，营养学研究取得了极其重要的进展，尤其是在蛋白质、氨基酸和能量的需要上，这对掌握和满足育种公司培育的快速生长家禽的营养需要是必要的，但是微量元素呢？     

SIMULTANEOUS CONGENITAL AND ACQUIRED EXTRAHEPATIC PORTOSYSTEMIC SHUNTS IN TWO DOGS

Two dogs with simultaneous congenital and acquired portosystemic shunts are reported. The first dog was an eight-month-old, male Golden Retriever with a history of peritoneal effusion, polyuria/polydipsia, and stunted growth. The dog had a microcytic, hypochromic anemia, a mildly elevated AST, and a moderate to severely elevated preprandial and postprandial serum bile acids. Transcolonic portal scintigraphy confirmed the presence of a portosystemic shunt. An intraoperative mesenteric portogram was performed. Two conjoined congenital extrahepatic portosystemic shunts and multiple acquired extrahepatic portosystemic shunts were identified. The second dog was a five-month-old, mixed breed with two week history of peritoneal effusion. Abdominal ultrasound and transcolonic scintigraphy were used to diagnose a portosystemic shunt. A single extrahepatic portosystemic shunt, portal hypertension, and multiple acquired collateral shunts were identified at surgery. The histologic alterations observed in these dogs were consistent with a portosystemic shunt. In these dogs, the presence of congenital and acquired portosystemic shunts and histopathologic findings are considered to represent a combination of congenital portosystemic shunts and noncirrhotic portal hypertension or portal vein hypoplasia.     

Characterization of a reo-like virus and its isolation from and pathogenicity for parrots

Necropsy of an African Grey parrot (Psittacus erithacus) revealed subcutaneous hemorrhages, multiple foci and microfoci of necrosis in the liver, spleen, bone marrow, and intestinal lamina propria, mild air sacculitis, and epicarditis. A virus, isolated from the liver, was non-enveloped, was polyhedral with a diameter of 84.9 +/- 3.4 nm, possessed a double-stranded RNA genome, and was stable at pH 3.0 for 30 minutes and at 56 C for up to 120 minutes. The virus was propagated in cell culture, purified by limiting dilution, and inoculated into two African Grey parrots. The experimental infections were fatal on the 8th and 9th days postinoculation in the orally and intramuscularly inoculated birds, respectively, and produced hemorrhages and necrotic lesions that recapitulated those of the index case.