Short-term effects of tillage practices on soil aggregate fractions in a Chinese Mollisol

Abstract

Soil aggregate-size distribution and soil aggregate stability are used to characterize soil structure. Quantifying the changes of structural stability of soil is an important element in assessing soil and crop management practices. A 5-year tillage experiment consisting of no till (NT), moldboard plow (MP) and ridge tillage (RT), was used to study soil water-stable aggregate size distribution, aggregate stability and aggregate-associated soil organic carbon (SOC) at four soil depths (0–5, 5–10, 10–20 and 20–30 cm) of a clay loam soil in northeast China. Nonlinear fractal dimension (D_m) was used to characterize soil aggregate stability. No tillage led to a significantly greater aggregation for >1 mm aggregate and significant SOC changes in this fraction at 0–5 cm depth. There were significant positive relationships between SOC and >1 mm aggregate, SOC in each aggregate fraction, but there was no relationship between soil aggregate parameters (the proportion of soil aggregates, aggregate-associated SOC and soil stability) and soil bulk density. After 5 years, there was no difference in D_m of soil aggregate size distribution among tillage treatments, which suggested that D_m could not be used as an indicator to assess short-term effects of tillage practices on soil aggregation. In the short term, > 1 mm soil aggregate was a better indicator to characterize the impacts of tillage practices on quality of a Chinese Mollisol, particularly in the near-surface layer of the soil.     

Seasonal changes in shoot water relations of Picea rubens at two high elevation sites in the Smoky Mountains

Seasonal changes in water relations of current-year shoots of red spruce (Picea rubens Sarg.) were examined in relation to climatic conditions in trees growing at elevations of 1720 and 1935 m on Clingman's Dome, Tennessee, USA, where increment core data have shown that red spruce decline increases with elevation. Relative height growth of trees at 1720 m was 68% greater than in trees at 1935 m. Following two weeks in July with only traces of precipitation, trees at both sites showed decreased saturated osmotic potentials. The magnitude of the reduction was greater in trees at the high elevation site than in trees at the low elevation site. However, during August and September, shoot water relations of trees at both sites were similar. Precipitation patterns and water relations measurements suggested that, at both sites, trees experienced water stress only briefly during the growing season and to a degree that could not account for the lower growth rates of trees at the high elevation site. During the period of cold hardening in October and November, trees at the low elevation site exhibited saturated osmotic potentials that were lower by 0.2 MPa and solute accumulation (osmol kg(dw) (-1)) that was 48% greater than in trees at the high elevation site.     

Non-timber forest products in rural Mali: a study of villager use

Malian Forest Service activities and policies have evolved since the beginning of colonialism under the assumption that forests and their products are the property of the government. Today the importance of involving local people in forest management is recognized. The purpose of this research was to determine the range of non-timber forest products local people use either for direct consumption or for income generation and to identify the trees/shrubs that yield these products in natural forests, fallow lands and crop fields. A gender analysis of the data was also conducted. The data were collected from face-to-face structured interviews using open-ended questions of 92 randomly sampled households in six Malian villages. One-half of the interviews were conducted with women and the other half were with men. The study identified 55 different non-timber forest products produced by 108 plant species. Almost all (99%) of the products identified are used for personal consumption, whereas 68% of the products are also used to generate income. Products such as firewood, leaves for sauces, shea nuts for oil/butter, seeds for condiments and nuts/seeds for soap are the most frequently mentioned products collected by women. Different categories of products like utensils/house materials, animal feed and construction materials (thatch, poles, mats) are the products most frequently collected by men. Ninety percent of the products collected are found in the natural forests; 63% are collected from trees on fallow lands and 51% from scattered trees in crop fields. Forest Service support of villagers using non-timber forest products would create an economic relationship between the forest and the local people. This is essential for the protection of the forest because people will safeguard their interests.     

Synthetic genetic polymers capable of heredity and evolution

Genetic information storage and processing rely on just two polymers, DNA and RNA, yet whether their role reflects evolutionary history or fundamental functional constraints is currently unknown. With the use of polymerase evolution and design, we show that genetic information can be stored in and recovered from six alternative genetic polymers based on simple nucleic acid architectures not found in nature [xeno-nucleic acids (XNAs)]. We also select XNA aptamers, which bind their targets with high affinity and specificity, demonstrating that beyond heredity, specific XNAs have the capacity for Darwinian evolution and folding into defined structures. Thus, heredity and evolution, two hallmarks of life, are not limited to DNA and RNA but are likely to be emergent properties of polymers capable of information storage.     

In vitro biomechanical comparison of three methods for internal fixation of femoral neck fractures in dogs

The in vitro biomechanical properties of three methods for internal fixation of femoral neck fractures were evaluated. Fifty cadaveric femura from Beagle dogs were used. Ten intact femora served as controls. In 40 femura, an osteotomy of the femoral neck was performed to simulate a transverse fracture. With the remaining 30 femura, three repair methods (two medium Orthofix pins, a 2.7 mm cortical bone screw placed in lag fashion and an anti- rotational Kirschner wire, or three divergent 1.1 mm Kirschner wires) were used to stabilize the osteotomies, and 10 osteotomies were stabilised per repair method. These 30 femura where then subject to monotonic loading to failure. Construct stiffness and load to failure were measured. In the remaining 10 femura, pressure sensitive film was placed at the osteotomy site prior to stabilization with either two Orthofix pins (n = 5) or a screw placed in lag fashion (n = 5) to determine the compressive pressure (MPa), compressive force (KN) and area of compression (cm2). There was no significant difference in the stiffness or load to failure for the three repair methods evaluated. There was no significant difference in the compressive pressure, compressive force or area of compression in osteotomies stabilized with Orthofix pins and 2.7 mm bone screws.     

Efficacy against Fasciola hepatica and the pharmacokinetics of triclabendazole administered by oral and topical routes

Objective   To determine the efficacy of triclabendazole (TCBZ) against 28-day-old, early immature liver fluke in cattle and its pharmacokinetics following administration by the oral or topical (pour-on) route.
Procedures   Cattle (n = 18) were infected with 500 TCBZ-susceptible liver fluke metacercariae and randomly allocated to three groups. At 28 days after infection, the groups were: (1) untreated controls; (2) treated with oral TCBZ at 12 mg/kg in combination with oxfendazole and selenium (TOS); (3) treated with pour-on TCBZ at 30 mg/kg in combination with abamectin (TA). Blood samples were taken immediately prior to treatment and serially after treatment to assess the plasma profile of TCBZ metabolites. Ten weeks after treatment all animals were slaughtered and total liver fluke counts, fluke egg counts and liver pathology were assessed.
Results   Both the TOS and TA treatments resulted in significant reductions of 28-day-old liver fluke, as assessed by fluke counts and fluke egg counts at slaughter, and the reductions following TOS treatment were significantly greater than those following TA treatment. The blood profile of TCBZ metabolites in TOS-treated animals showed a significantly greater area under the plasma concentration time curve and a higher maximum observed concentration than those treated with TA. There was significantly less liver pathology in TOS-treated animals than in the TA-treated animals.
Conclusion   TCBZ administered orally at 12 mg/kg resulted in greater efficacy against 28-day-old, early immature liver fluke than was achieved by topical administration at 30 mg/kg. Plasma metabolites of TCBZ were higher and liver pathology was less in TOS-treated animals than in TA-treated animals.     

Is rhamnolipid biosurfactant useful in cadmium phytoextraction?

Purpose  

Successful chelant-assisted phytoextraction requires application of an eco-friendly metal-complexing agent which enhances metal uptake but does not pose a significant risk of off-site movement of metals. Rhamnolipid biosurfactant has been used to enhance cadmium (Cd) removal from contaminated soil by washing. It has a strong affinity for Cd compared to some other hazardous metals, suggesting that rhamnolipid could be useful in Cd phytoextraction. This study investigated the potential use of rhamnolipid to enhance Cd phytoextraction.     

Comparative cell morphology in the peripheral blood film from exotic and native animalsa

Haematological investigation is an important part of disease diagnosis. This is particularly so when investigating individual animal disease. It may also be important when investigating diseases in groups of animals, but the opportunity to perform necropsies to directly detect disease processes often diminishes its usefulness. Haematological investigation is essentially similar for all species. The presence of nucleated erythrocytes and thrombocytes in nonmammals requires alteration of haemoglobin measurement and cell counting. In addition, it may cause some confusion in identification of cells in peripheral blood films. Examination of blood films is an important component of haematological investigation and provides useful information on erythroid, leukocytic and platelet/thrombocytic alterations. Interpretation of alterations is essentially similar for all species. However, cell identification can at times be difficult. There are five basic leukocytes in all species: neutrophil (mammals) or heterophil (nonmammals), eosinophil, basophil, lymphocyte and monocyte. In nonmammals it may be difficult at times to distinguish between heterophils and eosinophils. In addition, lymphocytes may be confused with thrombocytes. However, a common-sense approach to the examination of the peripheral blood film will minimise this confusion.