Trade-offs among establishment success,stem morphology and productivity of underplanted Toona ciliata: Effects of nurse-species and thinning density

Toona ciliata (Australian red cedar), a valuable hardwood species, requires a nurse-tree overstorey to prevent damage from frost and drought in some regions of north-eastern Argentina. Different nurse-species offer different degrees of protection, resource competition, and thinning revenues. In addition, choice of nurse-species will influence trade-offs between T. ciliata establishment success, stem quality and productivity as well as revenue from intermediate and final harvests. We tested the effects of overstorey species and planting density on underplanted T. ciliata survival, stem morphology and growth. Initial stand densities of nurse-species Pinus taeda (625 stems/ha), P. elliottii × P. caribaea (625 stems/ha), and Grevillea robusta (833 stems/ha) were thinned by 0%, 25%, 50%, and 75% in three experiments, each using a randomized block design. Initial mortality, light availability and growth of T. ciliata, as well as growth of its nurse-trees, were measured before and two years after thinning. In the third year, we characterized T. ciliata stem morphology (straightness and height-to-diameter-ratio) and destructively harvested a subsample of T. ciliata in order to investigate T. ciliata biomass production and allocation patterns in response to overstorey species, thinning density and light availability. T. ciliata mortality was lower when planted under G. robusta than the pines, and increased in plots with greater exposure to solar radiation. T. ciliata productivity was also greater under G. robusta than under the pines, and was generally greatest where any of the nurse-species were thinned by 75%. Stem form was best when growing under P. taeda and in stands thinned by 50%, regardless of nurse-species. With the exception of early mortality, light levels appeared to have limited effects on T. ciliata growth dynamics. Neither growth rate nor stem morphology was strongly correlated with light availability. Total overstorey basal-area was highest in P. taeda stands and individual overstorey tree growth generally increased with decreasing stand densities, except for slower height growth of G. robusta in more open stands. Thinning operations resulted in sawn-wood revenue for the pine species only. Because stand productivity and stem quality were optimized under different nurse-species and thinning treatments, we conclude that the choice of nurse-species and thinning intensity will depend on management objectives and will change with market preferences and conditions.     

Australian sperm whales from different whaling stocks belong to the same population

1. Understanding the factors driving population structure in marine mammals is needed to evaluate the impacts of previous exploitation, current anthropogenic threats, conservation status, and success of population recovery efforts.
2. Sperm whales are characterized by a worldwide distribution, low genetic diversity, complex patterns of social and genetic structure that differ significantly within and between ocean basins, and a long history of being commercially whaled. In Australia, sperm whales from the (International Whaling Commission assigned) southern hemisphere ‘Division 5’ stock were very heavily exploited by whaling.
3. The present study assessed the potential effects of whaling on the genetic diversity of sperm whales in Australia and the population genetic structure of these whales within a global context. A combination of historical and contemporary sperm whale samples (n = 157) were analysed across six regions, from south-eastern Australia (‘Division 6’ stock in the Pacific Ocean) to south-western Australia (‘Division 5’ stock in the Indian Ocean).
4. Sperm whales sampled from the ‘Division 5’ and ‘Division 6’ stocks belong to the same population based on nuclear and mitochondrial DNA (mtDNA) analyses. Four novel sperm whale mtDNA haplotypes were identified in animals from Australian waters. Levels of genetic diversity were low in Australian sperm whales but were similar to those previously reported for populations in the Indian and Pacific Oceans.
5. Given the genetic distinctiveness of sperm whales in Australian waters from other regions in the Pacific and Indian Oceans, and the lack of recovery in population numbers, further scientific studies are needed to increase our understanding of population dynamics and the effectiveness of threat management strategies in this species.

     

Selection efficiency of high inorganic phosphorus-low stachyose lines from soybean breeding populations of different genetic backgrounds

Reducing the antinutritional components of soybean (Glycine max) seed is necessary for producing animal feed with increased metabolizable energy and nutrient availability. The objective of this study was to evaluate marker-assisted and phenotypic selection for the high inorganic phosphorus (Pi) and low stachyose traits controlled by the Lpa and MIPS1 mutations in six breeding populations. Phenotypic selection for low phytate individuals carrying Lpa mutations using Pi was reliable, but the assay should include parental genotypes to construct thresholds before performing selections, as the effect of Lpa on Pi depends on genetic background. Phenotypic selection for low phytate individuals carrying MIPS1 using Pi should be complemented with sugar data because selection based solely on Pi may be inefficient, as this trait is not environmentally stable in MIPS1 germplasm. Marker-assisted selection for simple sequence repeat (SSR) linked to Lpa2 (Satt527, Satt561) depended on the pedigree of the population suggesting that perfect markers (e.g., single nucleotide polymorphism) should become the molecular tool for screening a large number of progenies with high efficiency.     

Paired-site approach for studying soil organic carbon dynamics in a Mediterranean semiarid environment

This work investigated the effects of land cover and land-use change (LUC) on the ability of a soil to store carbon (C) and reduce carbon dioxide (CO₂) emissions, in a Mediterranean area. Using a paired-site approach, we estimated the effect of land-cover change on the C stock from 1972 to 2008 in a natural reserve (Grotta di Santa Ninfa) in western Sicily. We selected 15 paired sites representative of five LUCs. We studied the effect of land use on soil organic C (SOC) content in bulk soil and in different particle-size fractions (2000-1000 μm, 1000-500 μm, 500-250 μm, 250-63 μm, 63-25 μm, and < 25 μm). Laboratory incubation of the soil samples was conducted to measure CO₂ evolution in bulk soil collected at two different depths from each paired site. We found that the conversion of natural vegetation to orchards (vineyards and olive groves) resulted in SOC decreases ranging from 27% to 50%. The conversion from vineyards to arable land led to a 9% decrease in SOC, whereas the opposite caused a 105% gain. When arable land was replaced by Eucalyptus afforestation, a 40% increase in SOC was observed. SOC decline occurred mainly in coarser soil fractions, whereas the finest fractions were not influenced by land use. We calculated an overall SOC reduction of 63% in the study area, corresponding to a 58 Mg ha^− 1 SOC loss in less than 30 years. Our results indicate that land-use conversion, vegetation type, and management practices that control the biogeochemical and physical properties of soil could help reduce CO₂ emissions and sequester SOC.     

Identifying a new paradigm for assessing irrigation system performance

There are many definitions of irrigation system efficiency that are applied over a range of scales. Many traditional definitions considered only the water diverted as the water volume of concern. Considering also the water consumed in defining effective irrigation efficiency is a shift from the classical definition of system efficiency. In this paper, equations are derived for calculating the following system performance measures: the irrigation consumptive use coefficient, irrigation system efficiency, irrigation water and soil salinities, relative yield, and productivity of consumed, diverted and beneficially used water. The expressions are based on quite general assumptions and are valid for systems with a single water source and layouts composed of (or simplified to) irrigation units arranged in a row. The aim of these expressions is to illustrate how system performance is affected by the reuse of water which depends on the system’s hydraulic connections and the irrigation unit performance. Illustrations of the model are provided for systems in series and in parallel. Testing and refinement by removing some of the general assumptions underlying the model will be needed to develop practical applications that can be more confidently applied for comparison and improvement of irrigation systems.     

胆碱与乳牛营养

乳牛需要胆碱用于合成一定数量的磷脂,而且胆碱是乙酰胆碱的前体。同时,胆碱也是不稳定甲基体的重要来源,胆碱和蛋氨酸均可提供不稳定甲基体,两者具有可以互换的性质。因此,提供不稳定甲基体的胆碱、蛋氨酸和甜菜碱(betaine),和为合成甲基体的叶酸和维生素B_(12)在饲粮中的供应,在满足胆碱的需要量方面均有相     

Biodiversity in a germplasm collection of durum wheat

Summary Over 7,600 durum wheat accessions belonging to 22 country gene pools were evaluated in Syria, during the seasons 1985–86 through 1987–88 under semi-arid Mediterranean climatic conditions. Data on seven agronomic traits are presented to assess the distinctiveness and the phenotypic diversity of these pools. Univariate statistical analysis revealed differences among materials of diverse origins for all traits. Mean phenotypic diversity within countries was highest in the germplasm from India, lowest in that from Bulgaria. In a canonical variate analysis, the first three canonical variables explained 77.7% of the total variance. A cluster analysis was performed to supplement the generated information by the canonical analysis. The multivariate analyses evidenced the distinctiveness of the Ethiopian germplasm. The gene pools from Syria and Jordan, closely resembling each other, appeared separate from all others. A certain peculiarity was also shown by the germplasms from Greece, Morocco and France, while the remaining countries clustered into four groups. The results of the present evaluation could provide useful information for breeding activities, germplasm collection, and establishment of core collections. Evidence is presented that environment played a major role in creating the overall variation for the considered traits, although germplasm exchange seemed also an important factor.     

Structure and variation of subterranean clover populations from Sicily,Italy

Summary A collection of subterranean clover lines singled out from populations of the species Trifolium brachycalycinum and T. subterraneum collected in Sicily, Italy, was examined at two localities for flowering time and at one locality for oestrogen content and seed yield. The structure and variation of the populations of the two species were compared. The relationship between flowering time of the populations and some environmental features of their collection sites was examined to assess whether the maturity requirements of the two species were similar and to frame selection models focused on developing varieties of appropriate maturity. Populations of T. subterraneum were, on average, more complex than those of T. brachycalycinum, being characterized by higher number of lines per population and greater intra-population variation for flowering time, oestrogen content and seed yield. Furthermore, populations of T. subterraneum were, on average, about 15 days earlier than sympatric populations of T. brachycalycinum. Both the greater variation and the relative earliness of T. subterraneum occurred irrespective of the environments of origin of the populations. Inferences are drawn on the adaptive advantages that such features confer to T. subterraneum. Mean flowering time of the populations increased on increasing annual rainfall and altitude of the collection sites. However, the changes in maturity appeared almost exclusively related to variations in rainfall in T. subterraneum, while in T. brachycalycinum the effect of altitude was greater and that of rainfall less marked than in the former species.     

Acylglycerol and fatty acid components of pulp,seed, and whole olive fruit oils. Their use to characterize fruit variety by chemometrics

The contents of triacylglycerols and diacylglycerols in three kinds of olive fruit oils (pulp, seed, and whole fruit) were determined. The fatty acid composition and the quality ratios 1,2-diacylglycerols/1,3-diacylglycerols and 1,2-diacylglycerols/total diacylglycerols were also assessed. Seven major Italian olive varieties were considered. Results of univariate statistical analyses indicated that the above analytical parameters (glyceridic ratios excepted) were effective in discriminating between pulp and seed oils. The seed oil fraction did not determine any change in the glyceridic indices and the acylglycerol or fatty acid composition concerning the whole fruit oil (mixture of pulp and seed oil fractions), the weight (%) of seed ( approximately 2%) being by far lower than the weight (%) of pulp ( approximately 85%) (fruit weight basis). Based on the data of triacylglycerol or fatty acid composition, and using appropriate parametric or nonparametric multivariate statistics, the genetic origins (olive variety) of the three fruit oil kinds were characterized.