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This study was aimed at qualifying the methane emission ability of different communities in alpine meadow, and monitoring if the dominant species from these communities could emit methane in a sand culture experiment. Using the static chamber technique and gas chromatography method, two experiments were conducted in the field and in laboratory. First, the methane flux rate was measured in plant communities: natural alpine meadows (NM), Elymus nutans pasture (EP), herbaceous community in shrub (HS), and a Poa fruticosa meadow (PS). A 3-month sand culture experiment was conducted to show the non-microbial methane emission from living plants. Average methane emission rates were estimated to be 16.83 µg m⁻² h⁻¹(range -49.3–107.8), 28.49 µg m⁻² h⁻¹ (range -55.0–96.2) and 20.91 µg m⁻² h⁻¹ (range -31.9– 145.8) for NM, EP, and PS, respectively. Methane emission rate from EP was significantly higher than from NM during the growing season. The reclaim of grassland would enhance the methane emission in this aera through this one year's measurement, but whether this conclusion suit to the whole Tibet Plateau, it remains further longer time and larger spatial scale experiments to verify it. The result of the sand culture experiment showed that some plant species emitted methane in an aerobic, nonmicrobial environment, most of herbaceous species showed a methane emission characteristic, the methane emission from plant may have a species dependent characteristic.
The primary goals of this study were to quantify the composition and size of bud banks and to evaluate the roles of bud banks of main dominant species Leymus chinensis (Trin.) Tzvel. and Carex duriuscula C.A. Mey. in population maintenance over a 2-year period. The four experimental plots were in early, early-mid, middle and late seral stages of a flooded restoration succession after they had approximately 12, 10, 8, and 6 months’ flood durations in the Songnen meadow, China. Five quadrats (each 0.25 ´ 0.25 m in area and 30 cm deep) were each sampled in four seral spots. The differences of L. chinensis and similarity of C. duriuscula in bud bank characteristics persisted in the studied seral stages from year to year. In each seral stage, rhizome buds comprised most of the L. chinensis bud banks in 2003; in 2004, juvenile tillers predominated. Rhizome buds consisted of the majority of C. duriuscula bud banks throughout the study period. The bud densities of L. chinensis and C. duriuscula experienced a significant linear increase with the increase of tiller density at different seral stages each year, but the slopes of these relationships in L. chinensis were higher than those in C. duriuscula. The total bud densities of C. duriuscula showed a significant linear decrease corresponding to the increase of those of L. chinensis from the early to the late seral stage in 2003 and 2004. Bud banks are vital for population maintenance and the number of bud banks is a good predictor of population dynamics.
In the present study, we selected a total of 26 Salix sphaeronymphe Gorz shrubs of various sizes on a cutover in the eastern Tibetan Plateau to evaluate the effects of shrub size on richness, cover and biomass of the understorey herbaceous community, grasses and forbs, as well as litter cover and biomass. Results indicated that the richness of herbaceous community, grasses and forbs significantly increased with the increased area of both undershrub canopies and open field. However, the cover and biomass of the herbaceous community beneath the shrub canopies decreased with increasing shrub size. Grasses and forbs, as different functional groups, responded differently to the increasing area of shrubs: the cover and biomass of grasses decreased while those of forbs increased. The cover and biomass of herbaceous community, grasses and forbs in the open field did not obviously vary with area. Under the shrub canopies, the cover and mass of litter positively correlated to area, but this was not the case in the open field. Our results suggest that shrubs have a positive effect on diversity and a negative effect on the cover and productivity of the herbaceous community in forest secondary succession on the alpine cutovers, and that these effects are size–dependent. Moreover, different functional groups of herbaceous plants can respond differently to the presence of shrubs.
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