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41.
利用泽兰实蝇控制紫茎泽兰的生防策略研究 总被引:12,自引:1,他引:11
本文根据野外泽兰实蝇种群15个世代的调查资料,利用契贝谢夫正交多项式拟合了泽兰实蝇、紫茎泽兰的空间格局。阐明了泽兰实蝇空间格局的序列变化及紫茎泽兰空间格局的特点;揭示了泽兰实蝇空间格局的特点受当地主风及寄主紫茎泽兰空间格局特点的影响;并从最优控制系统的角度对泽兰实蝇-紫茎泽兰系统作了初步探讨。首次提出了最佳释放虫量指标为每条虫占有10条枝条。这些结果为多点释放及定点多次释放泽兰实蝇防治紫茎泽兰这一生防策略提供了理论基础。 相似文献
42.
Abstract. The annual cycle of canopy structure in two mediterranean shrubs in a pioneer zone of the mobile dune system in the Donana National Park, Scrophularia frutescens and Halimium halimifolium, has been analyzed. Destructive methods were used as well as a new non-destructive method, based on frequency analysis of organ distribution within the plant canopy. S. frutescens shows strong seasonal changes of photo-synthetic biomass, but little annual increment in dry weight. In H. halimifolium, seasonal changes are not as strongly differentiated as in S. frutescens, but a higher annual increment is shown. The canopy structure of both species and its temporal changes are compared with existingplant strategy models. 相似文献
43.
The naturally-occurring stable isotopes deuterium and hydrogen are fractionated by a number of physical and biological processes. Deuterium has a tendency to precipitate out first from a moist air mass. Thus ground water will become isotopically lighter with an increase in latitude, altitude, or distance inland. Water taken up by the plant from the soil undergoes little change until evapotranspiration results in leaf water becoming isotopically heavier. Thus hydrogen isotopes in plants can reveal something of geography (groundwater) and climate. Hydrogen isotopes undergo little fractionation by passage through the food chain, although plant parasites tend to be enriched in D as compared to their hosts, possibly due to higher rates of transpiration in the parasitic plants. The splitting of water in photosynthesis results in the lighter isotope being incorporated into organic matter. An even larger isotopic fractionation results during lipid synthesis and other processes involving the pyruvate dehydrogenase complex. Differences in metabolic pathway between species can be detected by D/H ratios. Hydrogen isotopic differences can be detected between CAM, C4, and C3 species. Within C4 plants, the NADP-ME plants are isotopically distinguishable from NAD-ME and PEP-CK plants. 相似文献
44.
Seasonal water uptake and movement in root systems of Australian phraeatophytic plants of dimorphic root morphology: a stable isotope investigation 总被引:12,自引:0,他引:12
A natural abundance hydrogen stable isotope technique was used to study seasonal changes in source water utilization and water movement in the xylem of dimorphic root systems and stem bases of several woody shrubs or trees in mediterranean-type ecosystems of south Western Australia. Samples collected from the native treeBanksia prionotes over 18 months indicated that shallow lateral roots and deeply penetrating tap (sinker) roots obtained water of different origins over the course of a winter-wet/summer-dry annual cycle. During the wet season lateral roots acquired water mostly by uptake of recent precipitation (rain water) contained within the upper soil layers, and tap roots derived water from the underlying water table. The shoot obtained a mixture of these two water sources. As the dry season approached dependence on recent rain water decreased while that on ground water increased. In high summer, shallow lateral roots remained well-hydrated and shoots well supplied with ground water taken up by the tap root. This enabled plants to continue transpiration and carbon assimilation and thus complete their seasonal extension growth during the long (4–6 month) dry season. Parallel studies of other native species and two plantation-grown species ofEucalyptus all demonstrated behavior similar to that ofB. prionotes. ForB. prionotes, there was a strong negative correlation between the percentage of water in the stem base of a plant which was derived from the tap root (ground water) and the amount of precipitation which fell at the site. These data suggested that during the dry season plants derive the majority of the water they use from deeper sources while in the wet season most of the water they use is derived from shallower sources supplied by lateral roots in the upper soil layers. The data collected in this study supported the notion that the dimorphic rooting habit can be advantageous for large woody species of floristically-rich, open, woodlands and heathlands where the acquisition of seasonally limited water is at a premium. 相似文献
45.
Abstract.
- 1 Seasonal population growth rates for the pea aphid, Acyrthosiphon pisum Harris, were determined in three different host plant habitats; alfalfa, Medicago sativa (L.), clover, Trifolium pratense (L.), and peas, Pisum sativum (L.); over four years and eight places. It was possible to estimate a common intrinsic rate of increase for each host plant habitat.
- 2 An analysis of the relative influence of temporal, spatial and host plant habitat variation showed that the host plant habitat was most important in determining the growth rates of the populations, both in rate of build-up and decline.
- 3 Patterns of alate production in the three different habitats differed substantially between the annual peas and the two perennial legumes. During the summer, alate production was large and rapid in peas and remained low and constant in clover and alfalfa
- 4 Parasitism was highest in peas. The species composition of parasitoids differed between crops.
- 5 Aphids in annual peas had a higher intrinsic rate of increase and a faster rate of decline than in the two perennial legumes. This explains the presence of both migratory and sedentary forms among pea aphids.
46.
Marisa C. Piccolo Christopher Neill Jerry M. Melillo Carlos C. Cerri Paul A. Steudler 《Plant and Soil》1996,182(2):249-258
The natural abundance of 15N was examined in soil profiles from forests and pastures of the Brazilian Amazon Basin to compare tropical forests on a variety of soil types and to investigate changes in the sources of nitrogen to soils following deforestation for cattle ranching. Six sites in the state of Rondônia, two sites in Pará and one in Amazonas were studied. All sites except one were chronosequences and contained native forest and one or more pastures ranging from 2 to 27 years old. Forest soil 15N values to a depth of 1 m ranged from 8 to 23 and were higher than values typically found in temperate forests. A general pattern of increasing 15N values with depth near the soil surface was broadly similar to patterns in other forests but a decrease in 15N values in many forest profiles between 20 and 40 cm suggests that illuviation of 15N-depleted nitrate may influence total soil 15N values in deeper soil where total N concentrations are low. In four chronosequences in Rondônia, the 15N values of surface soil from pastures were lower than in the original forest and 15N values were increasingly depleted in older pastures. Inputs of atmospheric N by dinitrogen fixation could be an important N source in these pastures. Other pastures in Amazonas and Pará and Rondônia showed no consistent change from forest values. The extent of fractionation that leads to 15N enrichment in soils was broadly similar over a wide range of soil textures and indicated that similar processes control N fractionation and loss under tropical forest over a broad geographic region. Forest 15N profiles were consistent with conceptual models that explain enrichment of soil 15N values by selective loss of 14N during nitrification and denitrification. 相似文献
47.
ITE Merlewood Land Classification of Great Britain 总被引:7,自引:0,他引:7
R. G. H. Bunce C. J. Barr R. T. Clarke D. C. Howard A. M. J. Lane 《Journal of Biogeography》1996,23(5):625-634
Abstract. The Institute of Terrestrial Ecology (ITE) has classified the 1 km squares in Great Britain (GB) into thirty-two environmental strata, termed land classes, as a basis for ecological survey. The classes have been used in biogeographical studies of the distribution of individual species and species assemblages. The concept behind the technique is that there is an association between the environmental character of land and ecological parameters. The initial classification was based on a sample of squares drawn from a regular grid. The data for the 12121 km squares classified were drawn from published maps; the number of squares was limited by the available computing power. Subsequently the availability of more powerful computers and the need to improve geographical definition have led to the allocation of every 1 km square to its appropriate class. This paper has been written to summarise the principles involved in the development of the system and indicate the range of projects for which it has been used. The extension of the classification from a sample to the complete coverage of GB revealed the importance of the structure and style of data used to produce the classification. The significance of these conclusions for future work is discussed, with particular reference to automated methods of data capture. 相似文献
48.
REYNALDO LUIZ VICTORIA FERNANDO FERNANDES† LUIZ ANTONIO MARTINELLI MARISA DE CÁSSIA PICCOLO PLINIO BARBOSA DE CAMARGO SUSAN TRUMBORE‡ 《Global Change Biology》1995,1(3):165-171
Measurements of the organic carbon inventory, its stable isotopic composition and radiocarbon content were used to deduce vegetation history from two soil profiles in arboreal and grassy savanna ecotones in the Brazilian Pantanal. The Pantanal is a large floodplain area with grass-dominated lowlands subject to seasonal flooding, and arboreal savanna uplands which are only rarely flooded. Organic carbon inventories were lower in the grassy savanna site than in the upland arboreal savanna site, with carbon decreasing exponentially with depth from the surface in both profiles. Changes in 13C of soil organic matter (SOM) with depth differed markedly between the two sites. Differences in surface SOM 13C values reflect the change from C3 to C4 plants between the sites, as confirmed by measurements of 13C of vegetation and the soil surface along a transect between the upland closed-canopy forest and lowland grassy savanna. Changes of 13C in SOM with depth at both sites are larger than the 3–4 per mil increases expected from fractionation associated with organic matter decomposition. We interpret these as recording past changes in the relative abundance of C3 and C4 plants at these sites. Mass balances with 14C and 13C suggest that past vegetational changes from C3 to C4 plants in the grassy savanna, and in the deeper part of the arboreal savanna, occurred between 4600 and 11 400 BP, when major climatic changes were also observed in several places of the South American Continent. The change from C4 to C3, observed only in the upper part of the arboreal savanna, was much more recent (1400 BP), and was probably caused by a local change in the flooding regime. 相似文献
49.
Guo-Ling Nan Adelheid R. Kuehnle 《In vitro cellular & developmental biology. Plant》1995,31(3):131-136
Summary Five parameters were examined for their effect on transformation ofDendrobium tissues by microprojectile bombardment. The superpromoter in pBI426 produced at least 1.5 times as many transient transformants
as the single cauliflower mosaic virus 35S promoter in pBI121 (37 to 69% vs. 0 to 44%) with dark and frequent GUS (β-glucuronidase) staining. Tissue, genotype, and type of microparticle significantly affected transient GUS activity. Higher
expression was seen in protocormlike bodies and in hybrid UH44 compared to etiolated shoots and protocorms and to hybrids
M61 and K1329-39. Microparticles of 1.6-μm Bio-Rad gold were more effective than 1.0-μm ASI gold. Transient GUS activity did
not differ among protocormlike bodies bombarded using helium propellant pressures of 650, 900, or 1100 psi. Transgenic plants
were recovered fromDendrobium UH800 protocormlike bodies bombarded with pBI426-coated, 1.1-μm tungsten particles using an early-model gunpowder-driven
apparatus with an estimated stable transformation rate of 11.7%. One transgenic plant ofDendrobium UH44 was recovered from etiolated shoot explants bombarded with pBI121-coated, 1.1-μm tungsten particles using the Dupont
PDS-1000 with a stable transformation rate of 0.17%. Positive selection results showed 100 to 200 mg·liter−1 kanamycin to be appropriate for regeneration of transgenic plants from protocormlike bodies, protocorms, and etiolated shoot
explants over a 3- to 9.5-mo. period. 相似文献
50.
Summary A field study of the foraging strategy used by the ponerine ant,Hagensia havilandi is reported. They have permanent nests in the leaf litter of coastal forests.H. havilandi is a diurnal forager and collects a variety of live and dead arthropods. These predatory ants exhibit individual foraging with no cooperation in the search for or retrieval of food items. Three colonies were observed and showed similar temporal and spatial foraging patterns. The paths of individual ants were followed and the results showed that the foragers exhibit area fidelity, and return to the nest via a direct route on finding on prey item. Several foragers did not return to the nest at dusk but returned the following morning. Occasionally a limited amount of tandem recruitment was displayed. 相似文献