The integration of pasture,livestock and widely-spaced pine in South West Western Australia

This paper expands on a short voluntary presentation, by the first two authors, to the 18th IUFRO World Congress held at Ljubljana, Yugoslavia, in September 1986. It describes management procedures and incorporates biological and economic data, from a number of agro-silvo-pastoral trials in the South West of Western Australia.The integration of pine timber and livestock production is shown to have a range of economic and environmental benefits available in the long-term. Ways in which the choice of tree density, planting pattern and silvicultural regime can each be directed towards the achievement of various objectives are indicated.     

改进PSO算法在电力系统无功优化中的应用

介绍一种改进粒子群的无功优化方法。采用简化粒子群优化方程和添加极值扰动算子两种策略加以改进,提出简化粒子群优化（SPSO）算法、带极值扰动粒子群优化（DPSO）算法,并将二者结合起来提出带极值扰动的简化粒子群优化（DSPSO）算法。以IEEE6节点系统为例进行无功优化计算,并与其他算法进行比较,结果表明：该算法具有较快的收敛速度及较强的全局搜索能力,可较好地解决电力系统的无功优化问题。     

Genetic association of cotton yield with its component traits in derived primitive accessions crossed by elite upland cultivars using the conditional ADAA genetic model

Boll number, lint percentage, and boll weight are three component traits for lint yield of upland cotton, Gossypium hirsutum L. Selecting high yielding lines or hybrids depends on the ability to dissect the genetic relationship of lint yield with these component traits. In this study, 14 day-neutral lines with desirable fiber quality derived from primitive accessions were top crossed with five commercial cultivars. The F₂ populations and parents were grown in one location in 1998 and two locations in 1999 at Mississippi State, MS. The F₃ populations and parents were grown in two locations in 2000. Lint yield and three component traits were measured and analyzed by the ADAA genetic model with the mixed model based conditional approach. Results showed that boll number or boll number with lint percentage or boll weight contributed to the majority of the phenotypic variance and variance components for lint yield. Boll number was more important than the other two component traits in terms of various genetic effects. The results also showed that the combination of boll number and boll weight greatly increased the contribution to lint yield even though boll weight itself had no significant contribution to lint yield compared to boll number alone. The genetic contribution effects were also predicted due to single component traits or their combinations for parents and crosses. The results revealed that the balanced selection of boll weight and boll number should be considered to obtain high yielding hybrids or pure lines. Contribution of the USDA-ARS in cooperation with the Mississippi Agric. and Forestry Exp. Stn. Mention of trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by USDA, ARS and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

SSR markers for marker assisted selection of root-knot nematode (<Emphasis Type="Italic">Meloidogyne incognita</Emphasis>) resistant plants in cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L)

Cotton (Gossypium hirsutum L) cultivars highly resistant to the southern root-knot nematode (RKN) [Meloidogyne incognita (Kofoid and White) Chitwood] are not available. Resistant germplasm lines are available; however, the difficulty of selecting true breeding lines has hindered applied breeding and no highly resistant cultivars are available to growers. Recently, molecular markers on chromosomes 11 and 14 have been associated with RKN resistance, thus opening the way for marker assisted selection (MAS) in applied breeding. Our study aimed to determine the utility of these markers for MAS. Cross one was RKN resistant germplasm M240 RNR × the susceptible cultivar, FM966 and is representative of the initial cross a breeder would make to develop a RKN resistant cultivar. Cross two consists of Clevewilt 6 × Mexico Wild (PI563649), which are the two lines originally used to develop the first highly RKN resistant germplasm. Mexico Wild is photoperiodic. We phenotyped the F₂ of cross one for gall index and number of RKN eggs per plant and genotyped each plant for CIR 316 (chromosome 11) and BNL 3661 (chromosome 14). From this, we verified that MAS was effective, and the QTL on chromosome 14 was primarily associated with a dominant RKN resistance gene affecting reproduction. In the first F₂ population of cross two, we used MAS to identify 11 plants homozygous for the markers on chromosomes 11 and 14, and which also flowered in long days. Progeny of these 11 plants were phenotyped for RKN gall index and egg number and confirmed as RKN highly resistant plants. Generally about 7–10 generations of RKN phenotyping and progeny testing were required to develop the original RKN highly resistant germplasms. Our results show that commercial breeders should be able to use the markers in MAS to rapidly develop RKN resistant cultivars.     

Comparisons of quantitative trait locus mapping properties between two methods of recombinant inbred line development

Theoretical comparisons for quantitativetrait loci (QTL) mapping properties wereconducted among simulated recombinantinbred (RI) populations developed bysingle-hill (SH), complete bulk, and singleseed descent (SSD) procedures by MonteCarlo simulations based on variouspopulation sizes, heritabilities, and QTLeffects. Our simulations includedestimation of QTL effects, QTL positions,and statistical testing power in the RIpopulations by comparing the estimates withpreset values. The simulation resultsshowed that the single hill (SH) bulk andsingle seed descent RI populations weregenerally not significantly different withrespect to quality of estimated QTL effectsand positions. Furthermore, when each RIpopulation had 150 lines, each couldprovide desirable properties for QTLmapping. The results implied that a SH RIpopulation consisting of 75 or moreF₂-derived families with two lines perfamily (corresponding population size of150 or above) was appropriate for QTLmapping and was not significantly differentthan a SSD RI population of 150. Thus, theSH method could be used to develop largenumbers of RI lines for achieving betterresults in QTL mapping. Simulations alsoshowed that there was no significantdifference between means using SH methodswith 10 and 100 fruits per family. However, RI populations developed by thecomplete bulk method where F₂identities are lost were not suitable forQTL mapping.     

Rollover protection on New York tractors and farmers' readiness for change

Tractor overturns contribute significantly to fatalities in New York State agriculture. On-site inspections a decade ago indicated that approximately 60% of tractors were without effective rollover protection. Our objectives were: to describe the current prevalence and distribution of rollover protective structures (ROPS) on New York farm tractors, to identify characteristics associated with the absence of ROPS, to explore segmenting the New York farm community on readiness for ROPS retrofitting, and to identify demographic characteristics that might assist in this segmenting. A random selection of 644 livestock, dairy, fruit, cash crop, vegetable, and organic farms were contacted for a telephone survey. Of 562 farms (87%) participating, 102 (18.1%) had all tractors equipped with ROPS and 138 (24.6%) had none. A disproportionate number of livestock, cash crop, and organic operations had no ROPS. Rates of ROPS-equipped tractors correlated directly with farm size and annual hours of tractor operation. Older farmers had a lower proportion of ROPS tractors. The presence of a child operator did not affect the proportion of ROPS tractors. After weighting the sample, the total number of non-ROPS tractors in New York is estimated at more than 80,000. In addition to providing key farm demographics, the survey enabled placement of farmers on a "stage of change" continuum related to readiness for retrofitting. Three-quarters of New York farmers are in the "precontemplation" stage of change relative to ROPS retrofitting, and this varies little by size of operation, age of farmer, or the presence of child tractor operators. Stage of change may relate to hours of tractor operation (p = 0.05) and does relate to commodity (p = 0.003) due primarily to the higher proportion of crop farmers in the earliest stage of change. The goal of retrofitting all New York farm tractors with ROPS appears nearly as daunting as it did a decade ago.     

A Climatic Freshening of the Deep Atlantic North of 50{degrees}N over the Past 20 Years

Observations made in summer 1981 show a significant and widespread decrease in salinity, averaging 0.02 per mil, in deep waters of the subpolar North Atlantic over the past two decades. This implies a relatively rapid response of deep water formation to climatic perturbation.     

Modeling perspective of the deforestation impact in stream water quality of small preserved forested areas in the amazonian rainforest

A long-term predictive model, MAGIC, was applied to a Central Amazonian catchment area to illustrate large scale deforestation effects on ‘islands’ of preserved areas, for the situations with and without climate changes. In addition, model sensitivity in response to different organic matter levels in the soil and stream waters as well as to different Al solubility constants was evaluated. The model output was strongly dependent on the chosen values of organic matter concentration and Al solubility constant. Application of the model to a 30 yr deforestation program revealed increases in streamwater ionic concentrations with or without climate change, although streamwater ionic concentrations were predicted to be higher as a consequence of climate change. On the centennial scale, streamwater ionic concentrations reach a new equilibrium, with concentrations higher than those prior to the surrounding deforestation. With the assumed increased cation deposition to the preserved forest areas, soil exchangeable cation concentrations increase with time and aluminum is released to solution. At the end of the simulated deforestation program, SO ₄ ^2? in the preserved areas began to be released to streamwater, inducing acidification. Application of the MAGIC model makes possible to estimate, for the rainforest environment, water quality changes as a function of different climate and land use changes.