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991.
Habitat specificity indices reflect richness (α) and/or distinctiveness (β) components of diversity. The latter may be defined by α and γ (landscape) diversity in two alternative ways: multiplicatively () and additively (). We demonstrate that the original habitat specificity concept of Wagner and Edwards (Landscape Ecol 16:121–131, 2001) consists of three independent components: core habitat specificity (uniqueness of the species composition), patch area and
patch species richness. We describe habitat specificity as a family of indices that may include either area or richness components,
or none or both, and open for use of different types of mean in calculation of core habitat specificity. Core habitat specificity
is a beta diversity measure: the effective number of completely distinct communities in the landscape. Habitat specificity
weighted by species number is a gamma diversity measure: the effective number of species that a patch contributes to landscape
richness. We compared 12 habitat specificity indices by theoretical reasoning and by use of field data (vascular plant species
in SE Norwegian agricultural landscapes). Habitat specificity indices are strongly influenced by weights for patch area and
patch species richness, and the relative contribution of rare vs. common species (type of mean). The relevance of properties
emphasized by each habitat specificity index for evaluation of patches in a biodiversity context is discussed. Core habitat
specificity is emphasized as an ecologically interpretable measure that specifically addresses patch uniqueness while habitat
specificity weighted by species number combines species richness and species composition in ways relevant for conservation
biological assessment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
992.
993.
994.
黄瓜根际促生菌的促生效应与防病作用 总被引:3,自引:0,他引:3
对黄瓜植物根际促生菌(PGPR)菌株的分离筛选、分类鉴定以及人们对其促生防病作用的应用和防病机制的研究现状进行了综述,以期为新型PGPR制剂的进一步研制、开发和应用提供参考. 相似文献
995.
平邑甜茶后代双胚苗的倍性鉴定及核型分析 总被引:1,自引:0,他引:1
为了确定平邑甜茶双胚苗的倍性特征和核型特点,采用压片和流式细胞仪观测的方法对平邑甜茶后代中双胚苗进行染色体倍性观察和核型分析。结果表明:4株供试材料均为三倍体,2n=3x=51,染色体为小型,染色体长度比差异不大;核型组成由中部着丝点染色体(m)和亚中部着丝点染色体(sm)组成;株系8-1、8-2、12-1和12-2的核型公式分别为2n=3x=45m+6sm,2n=3x=48m+3sm,2n=3x=27m+24sm,2n=3x=33m+18sm;染色体相对长度和着丝点指数的变异范围分别为1.21%~2.68%和34.19%~42.37%,1.44%~2.63%和35.59%~44.08%,1.36%~3.02%和32.85%~42.18%,1.43%~2.87%和34.23%~44.02%;核型分别属于1B、1A、2B和1B类型,表现为株系之间的核型不完全相同。本研究为丰富无融合生殖型砧木的育种理论,获得新的苹果无融合生殖型砧木提供有益的借鉴。 相似文献
996.
997.
桃叶片再生不定芽的研究 总被引:2,自引:1,他引:1
以桃栽培品种曙光、金童5号和甜桃王试管苗叶片为外植体,研究了基本培养基、植物生长调节剂种类及质量浓度组合、基因型和试管苗继代次数等因素对叶片再生的影响。结果表明,适宜暗培养的培养基为LP+1.5mg·L-1TDZ+0.15mg·L-1NAA;光培养基为LP+0.5mg·L-1TDZ+0.3mg·L-1KT+0.3mg·L-1NAA和LP+0.6mg·L-1TDZ+0.3mg·L-1KT+0.4mg·L-12,4-D;金童5号和曙光具有较强的再生能力,再生率分别为21.8%和14.5%;曙光和金童5号试管苗继代第1~11次叶片的再生能力与继代前3次愈伤组织相比形成率较高;曙光再生苗在培养基1/2MS+0.5mg·L-1NAA上生根率为100%,平均生根条数为7.9。 相似文献
998.
999.
Temporary water trading is an established and growing phenomenon in the Australian irrigation sector. However, decision support and planning tools that incorporate economic and biophysical factors associated with temporary water trading are lacking. In this paper the integration of an economic trading model with a hydrologic water allocation model is discussed. The integrated model is used to estimate the impacts of temporary water trading and physical water transfers. The model can incorporate economic and biophysical drivers of water trading. The economic model incorporates the key trade drivers of commodity prices, seasonal water allocations and irrigation deliveries. The hydrologic model is based on the Resource Allocation Model (REALM) framework, which facilitates hydrologic network simulation modelling. It incorporates water delivery system properties and operating rules for the main irrigation and urban centres in a study area.The proposed integration method has been applied to a case study area in northern Victoria, Australia. Simulations were conducted for wet and dry spells, a range of commodity prices and different irrigation distribution system configurations. Some example analyses of scenarios incorporating water trading were undertaken. From these analyses potential bottlenecks to trade that constrain the economic benefits from temporary water trading were identified. Furthermore, it was found that in certain areas of the system, trading can make impacts of long drought spells worse for water users, e.g. irrigators. Thus, the integrated model can be used to quantify short-term and long-term third party impacts arising from temporary water trading. These findings also highlight the need to link “paper trades” (estimated by economic models) to physical water transfers (estimated by biophysical models). 相似文献
1000.
Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates 总被引:4,自引:0,他引:4
Mahdi Gheysari Seyed Majid Mirlatifi Mehdi Homaee Gerrit Hoogenboom 《Agricultural Water Management》2009,96(6):946-954
Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO3) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO3-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha−1), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO3-N content of 0-30 and 30-60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO3-N leaching out of the 60-cm soil layer was 8.43 kg N ha−1, for the 142 kg N ha−1 and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO3 concentration at the 60 cm depth was 46 and 138 mg l−1, respectively. Based on our findings, it is possible to control NO3 leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management. 相似文献