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Warming effects on plant growth, soil nutrients, microbial biomass and soil enzymes activities of two alpine meadows in Tibetan Plateau

Li N., Wang G., Gao Y., Wang J.

Polish Journal of Ecology

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2011

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Vol. 59, nr 1

25-32

EN

The aim of this study was to assess initial effects of warming on the plant growth, soil nutrient contents, microbial biomass and enzyme activities of two most widespread ecosystem types: swamp meadow (deep soil, high water content) and alpine meadow (poor soil, low water content), in the hinterland of the Qinghai-Tibet Plateau (altitude 4600.4800 m a.s.l.) The temperature of air and upper soil layer was passively enhanced using open-top chambers (OTCs) (50 cm high with 60 cm at opening and constructed of 6 mm thick translucent synthetic glass) from 2006 to 2008. The use of OTCs clearly raised temperature and decreased soil moisture. In warmed plots, monthly mean air temperature was increased by 2.10[degrees]C and 2.28[degrees]C, soil moisture of 20 cm soil layer was decreased by 2.5% and 3.9% in alpine meadow and swamp meadow, respectively. Plant biomass significantly increased by 31% in alpine meadow and 67% in swamp meadow. Warming also affected soil microbial biomass C and N at both meadows. In swamp meadow, warming caused the decrease of soil organic carbon and total nitrogen in 0-5 cm layer and an increase in 5-20 cm. While in alpine meadow, these soil parameters increased in 0-5 cm layer and decreased in 5-20 cm layer. The effects of warming on enzyme activities differed depending on the enzyme and the meadow ecosystem. In general, enzyme activities were higher in the upper soil layers (0-5 cm) than in the lower soil layers (5-20 cm). The experiment results exhibited that warming improved the soil biochemical and microbiological conditions in high- mountain meadows, at least in the short term.

2

Yak (Bos grunniens L.) grazing effects on vegetation of alpine meadow with Potentilla fruticosa L. (Rosaceae) shrub in Qinghai-Tibet Plateau

Qiao Y., Wang Q., Wang W.

Polish Journal of Ecology

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2009

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Vol. 57, nr 4

769-777

EN

Grazing can change plant community composition and structure, which may alter the functions of the shrub meadow ecosystem. Grazing effects on Potentilla fruticosa shrub community in the headwater region of the Yellow River, which is in core area of the Qinghai-Tibet Plateau, are studied to provide adequate protection decision-making. We investigated continuous grazing and seasonal enclosure effects on P. fruticosa shrub communities. Three sites of P. fruticosa shrub comprising both continuous grazing and seasonal enclosure treatments were selected. The size of each fenced plot of P. fruticosa shrub was about 3000 m2, the stocking rate was about 5 heads per 100 m2 in continuous grazing treatment. Three samplings were made in each growing season of 2003 and 2004. Cover of vegetation, plant species composition and vegetation height were investigated in seven 1 x 1 m quadrates in each treatment. Above-ground biomass was measured in five 0.5 x 0.5 m quadrates. Shrub, forb, graminoid and sedge plant materials were clipped at ground level and oven-dried at 85[degrees] C to a constant mass. Plant composition was affected by long term continuous grazing and changes were caused by forb species shifting. No apparent difference in species richness between the grazed and ungrazed communities over the growing months were found but the Shannon's diversity indices of the grazed communities in June and July were higher than that of the ungrazed but lower in the late August and September. Live vegetation cover was reduced by 6.7%, 7.3% and 11.5%, respectively, owing to grazing in July, August and September, but not in June (P> 0.05). Forbs took up more than 50% cover of the vegetation in both grazed and ungrazed treatments. Relative cover of sedges and forbs in ungrazed treatment decreased in July, August and September, while that of graminoids increased more than 70% in the same period. Live vegetation height was reduced by 27% (2004) and 23% (2003) in late August and early September, but not in early growing season. Grazing reduced total above-ground biomass by 35%, 37% and 36% in July, August and early September, respectively, and the reduction was mainly in forb biomass. Continuous grazing affects plant composition and species diversity. The quantitative characteristics of P. fruticosa communities were influenced by grazing over growing months, but the effects were offset by non-growing season grazing.

3

Summer diet of two sympatric species of raptors Upland Buzzard (Buteo hemiliasius) and Eurasian Eagle Owl (Bubo bubo) in alpine meadow : problem of coexistence

Cui Q., Su J., Jiang Z.

Polish Journal of Ecology

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2008

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Vol. 56, nr 1

173-179

EN

Summer diets of two sympatric raptors Upland Buzzards (Buteo hemilasius Temminck et Schlegel) and Eurasian Eagle Owls (Bubo bubo L. subsp. Hemachalana Hume) were studied in an alpine meadow (3250 m a.s.l.) on Qinghai-Tibet Plateau, China. Root voles Microtus oeconomus Pallas, plateau pikas Ochotona curzoniae Hodgson, Gansu pikas O. cansus Lyon and plateau zokors Myospalax baileyi Thomas were the main diet components of Upland Buzzards as identified through the pellets analysis with the frequency of 57, 20, 19 and 4%, respectively The four rodent species also were the main diet components of Eurasian Eagle Owls basing on the pellets and prey leftovers analysis with the frequency of 53, 26, 13 and 5%, respectively. The food niche breadth indexes of Upland Buzzards and Eurasian Eagle Owls were 1.60 and 1.77 respectively (higher value of the index means the food niche of the raptor is broader), and the diet overlap index of the two raptors was larger (C[ue] = 0.90) (the index range from 0 - no overlap - to 1 - complete overlap). It means that the diets of Upland Buzzards and Eurasian Eagle Owls were similar (Two Related Samples Test, Z = -0.752, P = 0.452). The classical resource partitioning theory can not explain the coexistence of Upland Buzzards and Eurasian Eagle Owls in alpine meadows of Qinghai-Tibet Plateau. However, differences in body size, predation mode and activity rhythm between Upland Buzzards and Eurasian Eagle Owls may explain the coexistence of these two sympatric raptors.

4

Carbon isotope composition of plants along altitudinal gradient and its relationship to environmental factors on the Qinghai-Tibet Plateau

Li Mingcai, Liu Hongyan, Li Laixing, Yi Xianfeng, Zhu Xiaojia

Polish Journal of Ecology

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2007

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Vol. 55, nr 1

67-78

EN

Distribution pattern of [delta][^13]C values of plateau plants and their responses to environment along altitudinal gradients were investigated. In the growing season of 2003 (June-August), stable carbon isotope ratios ([delta][^13]C) of 174 plant samples belonging to 89 species of 20 families and 58 genera along the gradient 2800-4400 m (above sea level) was studied in six sites on the east edge of Qinghai-Tibet Plateau. The results indicated that the range of [delta][^13]C values of plants is narrow from -30.2[per mil] to -25.2[per mil], which means that none of the species examined belonged to C[4] photosynthetic pathway and all of these species performed C[3] photosynthetic pathway. The average [delta][^13]C values of plants at 6 sites were positively correlated to altitude (r = 0.974, P <0.01). The results revealed that site-averaged [delta][^13]C values were negatively correlated with temperature (r = 0.907, P <0.05) as well as CO[2] partial pressure (r = 0.940, P <0.01). The combination of these two factors account for 80% of the variation of [delta][^13]C values (r[^2] = 0.859, P <0.01). Varying precipitation with increasing altitude does not affect the plant [delta][^13]C values (r = 0.469, P> 0.05) as well as the sunlight duration(r = 0.630, P> 0.05).