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Impact of Extra Nitrogen on Ecological Stoichiometry of Alpine Grasslands on Tibetan Plateau : Meta-Analysis

Zhang H. R., Sun W., Li S. W., Han F. S., Yu C. Q., Zhang X. Z., Wang J. S., He Y. T., Zhong Z. M.

Polish Journal of Ecology

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2018

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Vol. 66, nr 4

315--324

EN

The general impact of extra nitrogen on ecological stoichiometry was examined in alpine grasslands on the Tibetan Plateau. Extra nitrogen increased the ratio of nitrogen to phosphorus (N:P ratio) in leaves and aboveground parts of plants by 43.4% and 32.7%, respectively. In contrast, extra nitrogen reduced the ratio of carbon to nitrogen (C:N ratio) in leaves by 30.6%. Extra nitrogen decreased soil C:N ratio by 9.1% in alpine meadows, but increased soil C:N ratio by 3.4% in alpine steppes. Extra urea had a stronger positive impact on aboveground vegetation N:P ratio than did extra ammonium nitrate. Extra urea rather than ammonium nitrate decreased aboveground vegetation C:N ratio and soil C:N ratio. The impact of extra nitrogen on aboveground vegetation N:P ratio was positively correlated with latitude, mean annual temperature and precipitation, nitrogen application rate and accumulated amount, but negatively correlated with elevation, duration and aboveground vegetation N:P ratio of the control plots. The impact of extra nitrogen on leaves N:P ratio was positively correlated with nitrogen application rate and accumulated amount. The impact of extra nitrogen on leaves C:N ratio was positively correlated with latitude, but negatively correlated with mean annual temperature and precipitation, nitrogen application rate, accumulated amount, duration and leaves C:N ratio of the control plots. Therefore, nitrogen enrichment caused by human activities will most likely alter element balance and alpine plants from nitrogen limitation to phosphorus limitation. This effect may weaken with time, and increase with climatic warming, increased precipitation and nitrogen input rate.

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Biomass fraction of graminoids and forbs in N-limited alpine grasslands: N:P stoichiometry

Zhang R., Gou X., Bai Y., Zhao J., Chen L., Song X., Wang G.

Polish Journal of Ecology

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2011

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Vol. 59, nr 1

105-114

EN

It is known that the dominance of graminoid species is promoted by N addition; however, there has been relatively little effort to examine the pattern induced by natural N fertility. Since nutriet use efficiency (NUE) is an important trait determining plant competitive ability, we expected that the species guild with higher NUE (lower nutrient content) may be more competitive on infertile soils. We explored the relationships between relative forbs biomass share, soil N and productivity by the linear regressi on analysis on a natural alpine meadow in northeast of Qinghai Tibetan Plateau (3600 m a.s.l.). To test the variety of leaf N:P stoichiometry, paired t test and general linear model multivariate (GLM) analysis were also used. We found that the leaf N:P ratios of the whole community were below 13 in studied sites, which may be consistent with the N limitation on the vegetation. Graminoids retained lower concentrations of leaf N and P than forbs in community on the N limited grassland. Consistent with our prediction, we found that the biomass fraction of graminoids declined with soil N content and aboveground production on the grassland. Different from the pattern along fertility gradients induced by N fertilization, our results showed that gr aminoids with lower internal nutrient content were able to resist low levels of nutrient availability on the natural alpine grassland when compared to forbs.

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Cyanoprokaryota of shallow lakes of Lubuskie Lakeland (mid-western Poland)

Pełechata A., Pełechaty M., Pukacz A.

Oceanological and Hydrobiological Studies

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2006

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Vol. 35, No.1

3-14

EN

In the summer seasons 2001 - 2004, water samples were collected in 25 shallow lakes in the area of the Lubuskie Lakeland (mid-western Poland). These investigations were the first detailed studies of phytoplankton in this part of Poland. A total of 73 taxa of Cyanoprokaryota were found. Two water blooms of Cyanoprokaryota were documented, with extremely high biomass in one of them. Water blooms were caused by Planktothrix agardhii, Anabaena flos-aquae and Pseudanabaena limnetica. The genus Anabaena represented the highest number of species. The occurrence of an invasive Cyanoprokaryota species - Cylindrospermopsis raciborskii - was detected in two lakes with the highest biomass of cyanoprokaryotic algae (where the above-mentioned blooms were observed).

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Short-term changes in the hydrochemical constituents in the water column of the Gdańsk Deep (Baltic Sea) in spring. Part 1. Nutrient and oxygen concentrations in relation to the density stratification

Falkowska L., Burska D., Bolałek J.

Oceanologia

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1998

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No. 40 (2)

83-104

EN

Both the seasonal thermocline in the uppermost layer of the sea and the halocline in the near-bottom layer were found to constrain transport of chemical compounds to the productive layer of the Gdansk Deep. The occasional disappearance of the halocline resulted on the one hand in the flow of nitrogen and phosphorus compounds through the intermediate layer towards the surface, and on the other in a considerable improvement in oxygen conditions in the near-bottom layer, this usually being either poorly oxygenated or anoxic. A statistically significant negative correlation between nitrate and oxygen concentrations was found in the isohaline layer. The N:P ratio was usually low during the day but increased at night. During spring this ratio increased in the euphotic layer. The large number of high N:P ratios may attest to the shortage of phosphates and to the change in the limiting factor - from nitrogen compounds in early spring to phosphates in late spring.