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Ramet recruitment from different bud types along a grassland degradation gradient in Inner Mongolia, China

Qian J., Busso C. A., Wang Z., Liu Z.

Polish Journal of Ecology

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2015

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Vol. 63, nr 1

38–-52

EN

Since the contribution of total belowground bud bank and different bud types to community regeneration has rarely been explored, the vegetative offspring recruited from different belowground bud types was investigated in four plant communities along a grassland degradation gradient in northeastern China (Inner Mongolia). This gradient, between 1000 and 1500 m a.s.l., has been caused by overgrazing. It is a Leymus chinensis steppe which occupies about 3.0×105 ha. Recruitment from tiller buds was dominant (>80%) in determining the total vegetative offspring density along the whole grassland degradation gradient. However, the proportional contribution of tiller-ramets to total ramet recruitment was significantly greater (P <0.05) during earlier than later stages of grassland degradation, while that of rhizome-ramets showed an opposite pattern. While the percentage contribution and density of root-derived ramets to total ramet density increased significantly (P <0.05) during the late stages of grassland degradation, those of bulb-ramets kept relatively constant along the whole grassland degradation gradient. The relative contribution of hemicryptophytes [i.e., Achnatherum sibiricum, Cleistogenes squarrosa, Festuca ovina, Koeoleria cristata, Poa annua, Stipa grandis] to total plant species richness decreased, while that of geophytes [i.e., Agropyron cristatum, Carex korshinskyi. Leymus chinensis, Allium anisopodium, A. bidentatum, A. tenuissimum, Astragalus galactites, Cymbaria dahurica, Iris tenuifolin, Potentilla acaulis, P. bifurca, Pulsatilla turczaninovii, Serratula chinensis, Thalictrum aquilegifolium] increased with the increases of grassland degradation. Our results showed that as grassland degradation increased, changes in the proportion of tiller-, rhizome- and root-derived ramets with respect to total ramet density determined in turn changes in the proportion of hemicryptophytes and geophytes in the study plant communities.

2

Responses of soil ß-glucosidase activities to simulated increased precipitation in a semi-arid temperate grasslands

Rui X., Liang D.

Polish Journal of Ecology

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2013

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Vol. 61, nr 2

401--404

EN

In concurrent with global warming, precipitation regimes are predicted to change as well around the world. In this study, two experimental sites were selected with different nutrient availability along a slope to study the effects of simulated increased precipitation on soil β-glucosidase activities in an Inner Mongolian grassland. Soil samples were adjusted to 55% of water holding capacity and incubated at 22°C in the dark for 32 days. Soil β-glucosidase activities were measured prior to and after the incubation. Results showed that soil β-glucosidase activities had differential responses to increased precipitation with a significant increase in the downslope site, but not in the upslope site. Correlation analysis showed that the initial soil β-glucosidase activities exerted a significantly negative relationship with soluble organic nitrogen (N). Our results indicated that both water availability and soil soluble N availability played important roles in regulating β-glucosidase activities in this semiarid region.

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Effect of 5 years long cessation of grazing on methane uptake in a semi-arid grassland

Zhou X., Hao Y.

Polish Journal of Ecology

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2010

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Vol. 58, nr 4

801-804

EN

Grazing exerts a key role in nutrient cycling in grassland ecosystems, however, little is known about the effects of short-term enclosure on methane (CH4) fluxes in a semi-arid steppe biome like this of Inner Mongolia. CH4 fluxes were measured in the Leymus chinensis (Trin) Tzvel. grassland using static chamber and gas chromatography (GC). Measurements were carried out twice per month over a growing season in 2004 at the two sites (one fenced since 1999 (UG99) and the other subjected to freely grazing (FG)). All CH4 fluxes were positive, indicating that this grassland functioned as the active atmospheric CH4 uptakes. During this period, the UG99 site (57.6 [plus or minus] 6.7 [mu]g C m[^-2] h[^-1]) had significantly higher mean CH4 uptake in comparison to the FG site (37.0 [plus or minus] 6.3 [mu]g C m[^-2] h[^-1]). A significant liner negative correlations between CH4 uptake and soil moisture (0.5 cm) at the both sites were found (P <0.05). The results indicated that short-term enclosure was helpful to improve CH4 uptake in this area.