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941.
Abstract This study was conducted to evaluate the effects of various rates of Copper (Cu) amendments (as CuSO4.5H2O at either 0, 25, 50, 100, 200, or 400 mg Cu kg‐1) to soils with different pH values on the distribution of various chemical forms of Zinc (Zn), Iron (Fe), Manganese (Mn), and Aluminum (Al) in soils and their uptake by Swingle citrumelo citrus rootstock seedlings. The soils included Myakka fine sand (pH 5.70), Candler fine sand (pH 6.45), and Oldsmar fine sand (pH 8.16). The chemical forms of metals evaluated in this study included exchangeable, sorbed, organically bound, precipitated, and residual forms. An increase in Cu rates, lowered the pH in the Myakka and Candler fine sands, but not in the Oldsmar fine sand. This, in turn, resulted in an increase in the proportion of the readily soluble forms (the exchangeable + sorbed forms) of Zn and Mn, and decreased that of Fe in the Myakka and Candler fine sands. In those two soils, the organically bound forms of Zn, Fe, and Mn decreased with an increase in Cu rates. However, the proportion of readily soluble forms was not significantly influenced by increasing Cu rates in the Oldsmar fine sand. The total content of Zn, Fe, and Mn in citrus roots and that of Zn and Fe in the leaves, significantly decreased with an increase in Cu rates in the Myakka and Candler fine sands. In the Oldsmar fine sand, Cu rates through the entire range had no significant effects on the total contents of Zn, Fe, and Mn in the leaves or in the roots of Swingle citrumelo rootstock seedlings. 相似文献
942.
RICHARD FRANKHAM JONATHAN D. BALLOU MARK D. B. ELDRIDGE ROBERT C. LACY KATHERINE RALLS MICHELE R. DUDASH CHARLES B. FENSTER 《Conservation biology》2011,25(3):465-475
Abstract: Fragmentation of animal and plant populations typically leads to genetic erosion and increased probability of extirpation. Although these effects can usually be reversed by re‐establishing gene flow between population fragments, managers sometimes fail to do so due to fears of outbreeding depression (OD). Rapid development of OD is due primarily to adaptive differentiation from selection or fixation of chromosomal variants. Fixed chromosomal variants can be detected empirically. We used an extended form of the breeders’ equation to predict the probability of OD due to adaptive differentiation between recently isolated population fragments as a function of intensity of selection, genetic diversity, effective population sizes, and generations of isolation. Empirical data indicated that populations in similar environments had not developed OD even after thousands of generations of isolation. To predict the probability of OD, we developed a decision tree that was based on the four variables from the breeders’ equation, taxonomic status, and gene flow within the last 500 years. The predicted probability of OD in crosses between two populations is elevated when the populations have at least one of the following characteristics: are distinct species, have fixed chromosomal differences, exchanged no genes in the last 500 years, or inhabit different environments. Conversely, the predicted probability of OD in crosses between two populations of the same species is low for populations with the same karyotype, isolated for <500 years, and that occupy similar environments. In the former case, we recommend crossing be avoided or tried on a limited, experimental basis. In the latter case, crossing can be carried out with low probability of OD. We used crosses with known results to test the decision tree and found that it correctly identified cases where OD occurred. Current concerns about OD in recently fragmented populations are almost certainly excessive. 相似文献
943.
944.
Abstract The excessive application of fertilizer and pesticides in grain production in China has posed a threat to the environmental sustainability of agricultural production. One of the major reasons of the increasing usage of chemical inputs by farmers is their trying to reach higher yields, especially In absence of adequate public inputs, such as development and extension of appropriate technology and necessary production infrastructure, etc. Based on the crop-specific data of the past 20 years, this paper examines how the public Investments in agricultural researches could impact on the reduction of farmers' private material inputs of major grain crops in China. It manifests that the increased investments in public sector, especially in agricultural researches, is a favorable and effective way to reduce farmers' private material inputs and should be given a priority consideration in the policy emendation to increase yields and improve production sustainability. 相似文献
945.
为探究煤炭生产过程中呼吸性粉尘难以捕捉且对人体造成伤害的问题,提出超音速水雾荷电降尘技术。基于荷电雾化机理,研究电极环直径、电极间距、电压3因素对超音速气动液滴荷电、雾化效果的影响。利用网状目标法测量雾滴群电流并计算荷质比,采用SPSS软件分析3因素与雾滴荷质比之间的相关性,并用激光粒度仪测量雾滴粒径。最后,采用最优荷电雾化参数进行喷雾降尘试验。研究结果表明:各因素对荷电效果的影响次序为:电压>电极间距>电极环直径;雾滴粒径随电压的升高而减小,随电极间距的增大先增大后减小,随电极环直径的增大先减小后增大;当电压12 kV,电极间距2.5 cm,电极环直径6 cm时,超音速荷电水雾降尘效果最佳,与普通水雾降尘相比,全尘降尘效率提高12.4%,呼尘降尘效率提高49.6%。 相似文献
946.
Sara Kophamel Björn Illing Ellen Ariel Morgan Difalco Lee F. Skerratt Mark Hamann Leigh C. Ward Diana Méndez Suzanne L. Munns 《Conservation biology》2022,36(1):e13724
Wildlife health assessments help identify populations at risk of starvation, disease, and decline from anthropogenic impacts on natural habitats. We conducted an overview of available health assessment studies in noncaptive vertebrates and devised a framework to strategically integrate health assessments in population monitoring. Using a systematic approach, we performed a thorough assessment of studies examining multiple health parameters of noncaptive vertebrate species from 1982 to 2020 (n = 261 studies). We quantified trends in study design and diagnostic methods across taxa with generalized linear models, bibliometric analyses, and visual representations of study location versus biodiversity hotspots. Only 35% of studies involved international or cross-border collaboration. Countries with both high and threatened biodiversity were greatly underrepresented. Species that were not listed as threatened on the International Union for Conservation of Nature Red List represented 49% of assessed species, a trend likely associated with the regional focus of most studies. We strongly suggest following wildlife health assessment protocols when planning a study and using statistically adequate sample sizes for studies establishing reference ranges. Across all taxa blood analysis (89%), body composition assessments (81%), physical examination (72%), and fecal analyses (24% of studies) were the most common methods. A conceptual framework to improve design and standardize wildlife health assessments includes guidelines on the experimental design, data acquisition and analysis, and species conservation planning and management implications. Integrating a physiological and ecological understanding of species resilience toward threatening processes will enable informed decision making regarding the conservation of threatened species. 相似文献
947.
张余郭溶誉李振东张新月王晓静黄小燕黄凯丰 《应用与环境生物学报》2022,(6):1437-1443
为明确外源2,4-表油菜素内酯影响苦荞生长、粒重与产量形成的生理机制,以苦荞品种晋荞2号为试验材料,研究不同浓度的外源2,4-表油菜素内酯处理(0、0.1、0.5、1.0和2.0 mg/L)对苦荞籽粒的灌浆特性、淀粉合成酶、根系形态及活力、叶片抗氧化酶活性及光合特性、农艺性状及产量的影响.结果表明:0.5 mg/L处理时苦荞籽粒的灌浆起始势(R0)、最大灌浆速率(Gmax)和平均灌浆速率(Gmean)最大,而达最大灌浆速率的时间(Tmax.G)最小;随2,4-表油菜素内酯施用量的增加,苦荞籽粒的腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)和可溶性淀粉合成酶(SSS)活性、根系总长度等根系形态指标和根系活力、叶片抗氧化酶活性及光合特性指标、株高、主茎直径、单株粒重和千粒重均呈先增加后降低的趋势,且都在0.5 mg/L处理时达最大.外源2,4-表油菜素内酯的施用能在一定程度上促进苦荞产量的增加,其中0.1、0.5和1.0 mg/L处理与对照相比分别提高产量1.10、1.31和1.06倍,2.0 mg/L处理则降低0.96倍.本研究表明适宜的外源2,4-表油菜素内酯处理(0.5 mg/L)能促进苦荞籽粒灌浆,提高粒重和最终的产量.(图1表8参32) 相似文献
948.
949.
950.
Increasing populations are causing an increase in food demands, and the area of cultivated land expands every year. Inappropriate land transition from ecology to production results in the constant decline of the ecological security level and influences the regional sustainable development. Adjusting unreasonable land use mode and reconstructing natural land cover are important ways to maintain and improve the ecological environment. Also reclaiming farmland as areas for forests and grasslands (FRFG) is another way. Successful implementation of FRFG in China is the result of comprehensive effect of the multi-scales driving forces. This paper analyses the driving forces of FRFG in China on a national (country) -regional (province) - local (county) - household (farmer) level scale, and the results are: driving forces at the national scale include ecological and food security and the western development of China; at the regional scale, ecological and economic benefits become the main factors to influence the dimension of FRFG under the same policy. The driving forces can be divided into 6 types: industrial structure adjustment, water source protection, flood prevention, the Three-Gorge Project protection, reduction of the amount of sediment flowing into the Yellow River and wind erosion desertification prevention. The driving forces at the local scale can be divided into 12 types with developing leading industries, increasing farmers' income and improving agricultural production conditions as the main types; at the household scale, the national policy meeting farmers' demands and the optimization of individual interests are all driving forces. 相似文献