scholarly journals Dynamics of stand composition changes in grass and grass-clover stands and relations between dominant species

2011 ◽  
Vol 49 (No. 3) ◽  
pp. 119-125
Author(s):  
P. Matušinsky ◽  
F. Hrabě

Changes in the species composition of temporary grass and grass-clover crops stands were studied in 1994–2000. The assessment consisted in determination of the dominance of individual species, measurement of their aboveground biomass weight and subsequent comparison of detected values. The measurements were evaluated by the method of determination of distance between vectors of stand composition and by the subsequent standardization. Resulting values are in a good agreement with the hither to knowledge and confirm that more favourable yield parameters are achieved within 30–60% of total changeability. Changes of species composition and stand changeability are at their initial stages of succession given by external changes mainly contributed to by the group of clumpy grass species and by internal changes within the group of pod-bearing plants.

Author(s):  
Е. Пещанская ◽  
В. Кожевников

Необходимость восстановления луговой степи центрального Ставрополья возникла ещё в середине прошлого столетия. Причиной тому послужило усиление воздействия антропогенных факторов на окружающую среду: распашка целины, промышленное и гражданское строительство, чрезмерный выпас скота, а также воздействие различного вида эрозий. В целях сохранения уникального природного комплекса степей с большим набором ценных и редких видов, а также в качестве опыта по восстановлению кормовых угодий в Ставропольском ботаническом саду в 1963 году были начаты исследования по интродукции дёрна. В период с 1963 по 1984 год на площади около 2 га были воссозданы фрагменты луговой степи. Изучение состояния искусственных ценозов, получение сравнительных данных в отношении видового состава, хозяйственно-ботанических групп, урожайности ценозов важнейшие компоненты исследования. В качестве эталонов обследовались территории естественных целинных степей (эталоны) (г. Бучинка, г. Стрижамент, урочище Новомарьевская поляна) с доминантами, сходными с доминантами изучаемых участков, восстановленных дёрном ( Бучинка , Стрижамент , Новомарьевская поляна ). Количество видов на эталонных участках составляет 6592, на восстановленных участках 83103. Видовой состав максимально представлен разнотравьем: от 44 до 72 видов. Во всех выборках проб преобладают злаки (31,9446,17) и разнотравье (29,4041,64), значительный удельный вес приходится на сухие остатки (старику) 7,6128,64. Масса бобовых колеблется в пределах от 0,85 до 11,01, осок от 0,1 до 13,83. Урожайность травостоя восстановленных ценозов сохраняется высокой 3,243,97 т/га. Показатели урожайности травостоя восстановленных формаций превышают показатели эталонов с разницей от 0,61 до 1,65 т/га. Restoration of grasslands became important in the Central Stavropol region in the middle of the last century. The reason was an increased anthropogenic effect: plowing, industrial and civil engineering, cattle grazing and erosion. Experiments on turf introduction got started at the Stavropol Botanical Garden in 1963 to preserve and restore the unique natural steppe area with a large number of valuable and rare species. Fragments of steppe were grown on 2 ha area from 1963 to 1984. The investigation focused on ecosystem conditions, species composition, botanical groups and yield. Natural steppes performed as controls (Buchinka, Strizhament, Novomaryevskaya Polyana) having similar dominant species as the trial areas. Control areas contained 6592 species, the restored ones 83103. There were 4472 different grass species grown. Proportions of gramineous averaged to 31.9446.17, grass mixtures 29.4041.64, grassland litter 7.6128.64. Contents of legumes varied within 0.8511.01, sedge 0.113.83. Grass productivity of the restored area was high 3.243.97 t ha-1. It exceeded the one of the natural areas by 0.611.65 t ha-1.


1930 ◽  
Vol 20 (3) ◽  
pp. 355-358 ◽  
Author(s):  
Rice Williams

1. The application of the zinc uranyl acetate method to the determination of exchangeable sodium in soils is discussed.2. Using this method of determination, good agreement was found between the exchangeable sodium extracted by 0·5 N acetic acid and that extracted by N ammonium chloride.3. The procedure for estimating sodium in acetic acid extracts is described, and the results for a number of typical non-saline Welsh soils are given.


1990 ◽  
Vol 141 ◽  
pp. 67-67
Author(s):  
V.A. Naumov

The most widely spread method of determination of star declinations is Bessel's method. Alhough it gives good agreement between star declinations obtained from observations of stars in upper and lower culminations, it leads to great systematic errors if the system of the instrument has an error of the type such as flexure or errors of divided circle. Besides, in the determination of correction of latitude (Δφ) and refraction (Δμ) considerable correlation between them exists.


Author(s):  
Elżbieta Wołejko ◽  
Bogumiła Pawluśkiewicz ◽  
Urszula Wydro ◽  
Tadeusz Łoboda ◽  
Andrzej Butarewicz

Abstract The effect of sewage sludge on the growth and species composition of the sward and the content of heavy metals in plants and urban soil. The determination of the sludge fertilising infl uence for the growth and composition of the urban grasslands’ swards and heavy metals concentration in above-ground parts of the plants was the aim of the study. The study was conducted on four research plots along the main roads in Białystok. The plots were seeded with two mixtures of lawn grasses (Eko and Roadside) and three doses of sludge were applied: 0 (control), 7.5 and 15 kg/m2. The study also included the determination of concentrations of Cd, Cr, Cu, Pb and Zn in soil and in the above-ground parts of lawn grasses and selected physical and chemical properties of soils fertilized with different doses of sludge. The dose of 7.5 kg/m2 increased the plant dry matter on average by 53%, the dose of 15 kg/m2 - on average by 90%. The largest effect of fertilization was found for lightest soil. Under these conditions, grass dry matter fertilized with 7.5 kg/m2 sludge was almost doubled, and fertilized with the dose of 15 kg/m2 was almost three times larger than in not fertilized areas. Perennial ryegrass (Lolium perenne L.) was the dominant species in the sward. Perennial ryegrass constituted on average 71% of all grass species in the areas fertilized with sewage sludge in the dose of 7.5 kg/m2, while on the areas fertilized with 15 kg/m2 - about 81%, and on not fertilized ones - 50% on average. Bioconcentration factor in the study allowed for estimating the plants ability to collect heavy metals present in the soil. Based on these results, it was found that the rate of bioconcentration of Cd, Cr, Cu and Pb was the highest in August, which may indicate the ease of downloading these metals by plants, particularly high mobility of metals during this period, and lower in October and June


Author(s):  
Jiří Skládanka ◽  
František Hrabě ◽  
Pavel Heger

The objective of the paper is to assess the species composition of grass stands used under regime of two and three cuts, the grassland species diversity and the grassland quality at different levels of nutrition. The experimental site is situated in the Bohemian-Moravian Upland at an altitude of 650 m a.s.l. The subjects of assessment are two-cut and three-cut grass stands with diverse intensities of nutrition: unfertilized, 30 kg ha−1 P and 60 kg ha−1 K fertilized, fertilized with 90 kg ha−1 N+PK, and fertilized with 180 kg ha−1 N+PK. Studied characteristics were as follows: share of dominant species in the harvested herbage, species diversity of the grass stand and grass stand quality. Evaluated were years 2002–2006. The two-cut use promoted development of Dactylis glomerata. The three-cut use promoted development of Poa ssp. The share of Alopecurus pratensis was equable in the two-cut and three-cut grass stands. The dose of N90+PK promoted Dactylis glomerata and was insufficient to increase the share of Alopecurus pratensis and Poa ssp. Fertilization resulted in the decreased share of most present herbs but de­ve­lop­ment of Polygonum bistorta was promoted, namely by the dose of N90+PK. In contrast, the application of PK promoted Trifolium repens. Fertilization had a significant (P < 0.05) influence on the share of individual species in the grassland. Three-cut grass stands exhibited a higher diversity than two-cut grass stands did. Fertilization had a significant (P < 0.05) influence on the decreased species diversity and on the increased grassland quality.


Author(s):  
J N Chapman ◽  
W A P Nicholson

Energy dispersive x-ray microanalysis (EDX) is widely used for the quantitative determination of local composition in thin film specimens. Extraction of quantitative data is usually accomplished by relating the ratio of the number of atoms of two species A and B in the volume excited by the electron beam (nA/nB) to the corresponding ratio of detected characteristic photons (NA/NB) through the use of a k-factor. This leads to an expression of the form nA/nB = kAB NA/NB where kAB is a measure of the relative efficiency with which x-rays are generated and detected from the two species.Errors in thin film x-ray quantification can arise from uncertainties in both NA/NB and kAB. In addition to the inevitable statistical errors, particularly severe problems arise in accurately determining the former if (i) mass loss occurs during spectrum acquisition so that the composition changes as irradiation proceeds, (ii) the characteristic peak from one of the minority components of interest is overlapped by the much larger peak from a majority component, (iii) the measured ratio varies significantly with specimen thickness as a result of electron channeling, or (iv) varying absorption corrections are required due to photons generated at different points having to traverse different path lengths through specimens of irregular and unknown topography on their way to the detector.


1969 ◽  
Vol 62 (4) ◽  
pp. 663-670 ◽  
Author(s):  
Lars Carlborg

ABSTRACT Oestrogens administered in lower doses than necessary to induce full cornification of the mouse vagina induce mucification. It was shown previously that the degree of mucification could be estimated by quantitative determination of sialic acids. A suitable parameter for oestrogen assay was the measurement of vaginal sialic acid concentration which exhibited a clear cut dose response curve. Eleven assays of various oestrogens were performed with this method. Their estimated relative potencies were in good agreement with other routine oestrogen assays. A statistically sufficient degree of precision was found. The sensitivity was of the same order, or slightly higher, than the Allen-Doisy test.


2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Camilo Fuentes Serrano ◽  
Juan Reinaldo Estevez Alvares ◽  
Alfredo Montero Alvarez ◽  
Ivan Pupo Gonzales ◽  
Zahily Herrero Fernandez ◽  
...  

A method for determination of Cr, Fe, Co, Ni, Cu, Zn, Hg and Pb in waters by Energy Dispersive X Ray Fluorescence (EDXRF) was implemented, using a radioisotopic source of 238Pu. For previous concentration was employed a procedure including a coprecipitation step with ammonium pyrrolidinedithiocarbamate (APDC) as quelant agent, the separation of the phases by filtration, the measurement of filter by EDXRF and quantification by a thin layer absolute method. Sensitivity curves for K and L lines were obtained respectively. The sensitivity for most elements was greater by an order of magnitude in the case of measurement with a source of 238Pu instead of 109Cd, which means a considerable decrease in measurement times. The influence of the concentration in the precipitation efficiency was evaluated for each element. In all cases the recoveries are close to 100%, for this reason it can be affirmed that the method of determination of the studied elements is quantitative. Metrological parameters of the method such as trueness, precision, detection limit and uncertainty were calculated. A procedure to calculate the uncertainty of the method was elaborated; the most significant source of uncertainty for the thin layer EDXRF method is associated with the determination of instrumental sensitivities. The error associated with the determination, expressed as expanded uncertainty (in %), varied from 15.4% for low element concentrations (2.5-5 μg/L) to 5.4% for the higher concentration range (20-25 μg/L).


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