Genetic characterization and evolutionary analysis of 4 Newcastle disease virus isolate full genomes from waterbirds in South China during 2003-2007

Complete genomes of four Newcastle disease virus (NDV) strains, isolated from ducks and wild birds in Guangdong province of China from 2003 to 2007, were sequenced and analyzed in this study. Pathogenicity tests in chicken embryos and chickens illustrate that D3 and R8 are lentogenic, and W4 and P4 are mesogenic strains. Phylogenetic analysis using all six genes provides a high resolution profile for genotype designation as genotype I for D3 and R8 strains and genotype VI for W4 and P4 strains. In addition, molecular dating based on different genes suggests that D3 and R8 diverged from their common ancestor at around 1998; W4 and P4 diverged from their common ancestor at around 1999. Subsequent selective pressure analysis displayed specific traits of genes evolution in all 4 strains since their divergence from the recent common ancestor. Furthermore, the geographic origins of 4 strains were deduced to be from Europe via two independent introduction events by phylogeographical analysis. This provides insights to the potential influence of waterfowl migration on NDV epidemiology.     

Revitalizing the winter turnip rape crop in the northern latitudes

Abstract

Winter turnip rape (Brassica rapa spp. oleifera) is an underutilized crop that deserves to be revitalized for use in high-latitude agriculture. Many crop rotations around the world are dependent on the small-grain cereals, and turnip rape as a break crop, with its range of secondary chemicals, helps to suppress weeds, nematodes and pathogenic fungi. It may be used as an energy crop, it can restrict erosion and nutrient leaching while also improving soil structure and fertility, and it requires relatively low inputs. Although winter turnip rape was once the major oil crop in Finland, in the 1970s it was replaced by spring turnip rape, the lower erucic acid and glucosinolate contents of which made it suitable for food and feed uses. Winter hardiness of the crop could be improved, and industrial end uses, such as lubricants for which high erucic acid content is preferred, targeted in the first instance. Breeding progress would be accelerated by a change from the predominantly self-incompatible breeding system to self-compatibility, now available in modern germplasm, and this would allow use of other rapid breeding methods, such as doubled haploidy. Thus, the many advantages of the winter turnip rape crop would repay its return to agriculture. In this review we will introduce the many utilization possibilities of the crop as well as give background on why more attention and research efforts should be paid towards this crop. We will also indicate some of the array of factors that have a marked role in an attempt to ecologically intensify crop production.     

Compost Research Runs “Hot” and “Cold” at La Trobe University

? Careful monitoring of the composting process — physically, chemically and biologically — enables managers to determine key nutritional and ecological factors vital to production of a quality compost. At La Trobe University, trials compared composts which achieve high temperature (80° C) with those controlled at moderate thermophilic temperatures (45 — 55° C) to demonstrate whether the hot phase is essential or whether composts of equal nutritional status can be produced by processing at lower temperatures.     

Characterizing Water Holding Capacity and Runoff during Composting of Greenwaste and Biosolids

ABSTRACT

Most composters in the United States use open-windrows. During high intensity precipitation events, uncontained water running off of the surface of the compost piles can potentially contaminate surface waters with nutrients and metals. Water that is absorbed poses no runoff concern but may threaten groundwater quality. To gain insight into these processes, stormwater runoff fractions and water holding capacity of compost piles have been characterized for greenwaste (GW) and biosolids (BS) materials. Laboratory scale experiments were conducted using days 1, 7, and 14 materials representing three different stages of composting. This study also evaluated sloped and flat-top as different pile geometries and surfactant use for promoting infiltration. Results indicate that fresh materials were most hydrophobic and the infiltration rates increased with increased composting times. The water storage capacity of the compost pile increased with the age of the compost pile. Compost water storage capacities could not be reliably estimated as the difference between field capacity and as-received water contents.     

Biophysical constraints on leaf expansion in a tall conifer

The physiological mechanisms responsible for reduced extension growth as trees increase in height remain elusive. We evaluated biophysical constraints on leaf expansion in old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. Needle elongation rates, plastic and elastic extensibility, bulk leaf water (Psi(L)) and osmotic (Psi(pi)) potential, bulk tissue yield threshold and final needle length were characterized along a height gradient in crowns of > 50-m-tall trees during the period between bud break and full expansion (May to June). Although needle length decreased with increasing height, there was no height-related trend in leaf plastic extensibility, which was highest immediately after bud break (2.9%) and declined rapidly to a stable minimum value (0.3%) over a 3-week period during which leaf expansion was completed. There was a significant positive linear relationship between needle elongation rates and plastic extensibility. Yield thresholds were consistently lower at the upper and middle crown sampling heights. The mean yield threshold across all sampling heights was 0.12 +/- 0.03 MPa on June 8, rising to 0.34 +/- 0.03 MPa on June 15 and 0.45 +/- 0.05 MPa on June 24. Bulk leaf Psi(pi) decreased linearly with increasing height at a rate of 0.004 MPa m(-1) during the period of most rapid needle elongation, but the vertical osmotic gradient was not sufficient to fully compensate for the 0.015 MPa m(-1) vertical gradient in Psi(L), implying that bulk leaf turgor declined at a rate of about 0.011 MPa m(-1) increase in height. Although height-dependent reductions in turgor appeared to constrain leaf expansion, it is possible that the impact of reduced turgor was mitigated by delayed phenological development with increasing height, which resulted in an increase with height in the temperature during leaf expansion.     

Temporal dynamics of stem expansion and contraction in savanna trees: withdrawal and recharge of stored water

Relationships between diel changes in stem expansion and contraction and discharge and refilling of stem water storage tissues were studied in six dominant Neotropical savanna (cerrado) tree species from central Brazil. Two stem tissues were studied, the active xylem or sapwood and the living tissues located between the cambium and the cork, made up predominantly of parenchyma cells (outer parenchyma). Outer parenchyma and sapwood density ranged from 320 to 410 kg m(-3) and from 420 to 620 kg m(-3), respectively, depending on the species. The denser sapwood tissues exhibited smaller relative changes in cross-sectional area per unit change in water potential compared with the outer parenchyma. Despite undergoing smaller relative changes in cross-sectional area, the sapwood released about 3.5 times as much stored water for a given change in area as the outer parenchyma. Cross-sectional area decreased earlier in the morning in the outer parenchyma than in the sapwood with lag times up to 30 min for most species. The relatively small lag time between dimensional changes of the two tissues suggested that they were hydraulically well connected. The initial morning increase in basal sap flow lagged about 10 to 130 min behind that of branch sap flow. Species-specific lag times between morning declines in branch and main stem cross-sectional area were a function of relative stem water storage capacity, which ranged from 16 to 31% of total diurnal water loss. Reliance on stored water to temporarily replace transpirational losses is one of the homeostatic mechanisms that constrain the magnitude of leaf water deficits in cerrado trees.     

Constraints on physiological function associated with branch architecture and wood density in tropical forest trees

This study examined how leaf and stem functional traits related to gas exchange and water balance scale with two potential proxies for tree hydraulic architecture: the leaf area:sapwood area ratio (A(L):A(S)) and wood density (rho(w)). We studied the upper crowns of individuals of 15 tropical forest tree species at two sites in Panama with contrasting moisture regimes and forest types. Transpiration and maximum photosynthetic electron transport rate (ETR(max)) per unit leaf area declined sharply with increasing A(L):A(S), as did the ratio of ETR(max) to leaf N content, an index of photosynthetic nitrogen-use efficiency. Midday leaf water potential, bulk leaf osmotic potential at zero turgor, branch xylem specific conductivity, leaf-specific conductivity and stem and leaf capacitance all declined with increasing rho(w). At the branch scale, A(L):A(S) and total leaf N content per unit sapwood area increased with rho(w), resulting in a 30% increase in ETR(max) per unit sapwood area with a doubling of rho(w). These compensatory adjustments in A(L):A(S), N allocation and potential photosynthetic capacity at the branch level were insufficient to completely offset the increased carbon costs of producing denser wood, and exacerbated the negative impact of increasing rho(w) on branch hydraulics and leaf water status. The suite of tree functional and architectural traits studied appeared to be constrained by the hydraulic and mechanical consequences of variation in rho(w).     

Stem dimensional fluctuation in Jeffrey pine from variation in water storage as influenced by thinning and prescribed fire

Forest thinning utilizing cut-to-length and whole-tree harvesting systems with subsequent underburning were assessed for their impacts on water storage in the extensible tissues of dominant and codominant trees in an uneven-aged Jeffrey pine (Pinus jeffreyi Grev. & Balf.) stand on the east slope of the Sierra Nevada. Prior to the onset of the third growing season following thinning and the second season after burning, manual band dendrometers were installed at breast height on the selected trees and readings of diurnal fluctuation in stem circumference, an indication of bole water status, were taken monthly for one year. Diameter and relative diameter fluctuation were calculated from the circumference measurements. Overall, thinning had a positive influence on stem water recharge capacity, with the most pronounced effects evident in the latter part of the growing season. During this period, bole contraction in thinned stand portions was 49 to 55% greater than in the unthinned control, suggesting that both a greater volume of stored water was available for transpiration and was transpired in trees of the former treatment. There was no clear evidence that harvesting method affected stem water storage and influences of underburning were also absent entirely. Seasonal effects on diurnal changes in stem diameter were prominent, as the extent to which boles contracted generally increased over the course of the growing season, whereas fluctuations were at a minimum during the colder months. The magnitude of stem dimensional flux was found to be negatively correlated with initial tree DBH in one instance, while negative relationships between the former and live crown length as well as percentage were also revealed, albeit infrequently. Changes in bole size were positively correlated with residual basal area in some cases. These results suggest that improvement in water relations can be realized from density management in a dry site forest type with no apparent compromise of this benefit by broadcast underburning.     

Removal of nutrient limitations by long-term fertilization decreases nocturnal water loss in savanna trees

Under certain environmental conditions, nocturnal transpiration can be relatively high in temperate and tropical woody species. We have previously shown that nocturnal sap flow accounts for up to 28% of total daily transpiration in woody species growing in a nutrient-poor Brazilian Cerrado ecosystem. In the present study, we assessed the effect of increased nutrient supply on nocturnal transpiration in three dominant Cerrado tree species to explore the hypothesis that, in nutrient-poor systems, continued transpiration at night may enhance delivery of nutrients to root-absorbing surfaces. We compared nocturnal transpiration of trees growing in unfertilized plots and plots to which nitrogen (N) and phosphorus (P) had been added twice yearly from 1998 to 2005. Three independent indicators of nocturnal transpiration were evaluated: sap flow in terminal branches, stomatal conductance (g(s)), and disequilibrium in water potential between covered and exposed leaves (DeltaPsi(L)). In the unfertilized trees, about 25% of the total daily sap flow occurred at night. Nocturnal sap flow was consistently lower in the N- and P-fertilized trees, significantly so in trees in the N treatment. Similarly, nocturnal g(s) was consistently lower in fertilized trees than in unfertilized trees where it sometimes reached values of 150 mmol m(-2) s(-1) by the end of the dark period. Predawn gs and the percentage of nocturnal sap flow were linearly related. Nocturnal DeltaPsi(L) was significantly greater in the unfertilized trees than in N- and P-fertilized trees. The absolute magnitude of DeltaPsi(L) increased linearly with the percentage of nocturnal sap flow. These results are consistent with the idea that enhancing nutrient uptake by allowing additional transpiration to occur at night when evaporative demand is lower may avoid excessive dehydration associated with increased stomatal opening during the day when evaporative demand is high.     

The recombinant BGH controversy in the United States: Toward a new consumption politics of food?

The history of the controversy overrecombinant bovine growth hormone (rBGH) is exploredin terms of the issue of the potential robustness ofa consumption-driven ``new' politics of food andagriculture. It is noted that while the dominanthistorical traditions in the social sciences haveserved to discount the autonomous role that consumersand consumption play in modern societies, there hasbeen growing interest in consumption within foodstudies as well as other bodies of scholarship such aspostmodernism, social constructivism, socialcapital/social distinction, and environmentalsociology. A review of the shifting pattern ofdiscourses during the rBGH controversy shows thatconsumption-driven claims and politics played atangible, but relatively minor role. Even so, it issuggested that the rBGH experience along with paralleltrends in food politics (e.g., anti-pesticidecampaigns such as the ``Alar scare,' agribusinessattempts to intimidate opponents through fooddisparagement laws, conditions-of-productionprovisions of the World Trade Organization agreement)could make the consumption/consumer dimension of foodpolitics more important in the future.