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1

Partitioning sources of ecosystem and soil respiration in an Alpine meadow of Tibet Plateau using regression method

100%
Fu G., Zhang X.-Z., Zhou Y.-T., Yu C.-Q., Shen Z.-X.
Polish Journal of Ecology
|
2014
|
tom 62
|
nr 1
Partitioning sources of ecosystem and soil respiration (Reco and Rs) is important for understanding how climate change affects carbon cycling. Plant and microbial biomass analyses and daytime measurements of Reco and Rs were performed for 25 plots in an alpine meadow at elevation 4313 m on the Tibetan Plateau. Plant and microbial biomass were determined by harvesting method and the chloroform fumigation-extraction method, respectively. Respiration fluxes were measured by an automated CO2 flux system (LI-8100, LI-COR Biosciences, Lincoln, NE, USA). Soil respiration can be estimated by a linear or exponential relationship between Reco and aboveground plant biomass (AGB). Microbial respiration (Rm) can be estimated by a linear or exponential relationship between Rs and belowground plant biomass (BGB) or by a multiple relationship between Reco and AGB and BGB. Soil respiration (or Rm) is respiration flux when AGB (or BGB) is extrapolated to zero for the linear and exponential regression methods. Similarly, Rm is respiration flux when both AGB and BGB are zero for the multiple regression method. Our findings suggest that the exponential regression method to partition sources of Reco and Rs may be more appropriate compared to other methods for this alpine meadow of Tibet.
2

The soil drying along the increase of warming masks the relation between temperature and soil respiration in an Alpine meadow of Northern Tibet

100%
Shen Z.-X., Wang J.-W., Sun W., Li S.-W., Fu G., Zhang X.-Z., Zhang Y.-J., Yu C.-Q., Shi P.-L., He Y.-T.
Polish Journal of Ecology
|
2016
|
tom 64
|
nr 1
A warming experiment with two magnitudes was performed in an alpine meadow of Northern Tibet since late June, 2013. Open top chambers (OTCs) with two top diameters (0.60 m and 1.00 m) were used to increase soil temperature. Soil respiration (Rs) was measured during the growing season in 2013–2014. The OTCs with top diameters of 1.00 m and 0.60 m increased soil temperature by 1.30 and 3.10oC, respectively, during the whole study period, but decreased soil moisture by 0.02 and 0.05 m³ m⁻³, respectively. However, the two patters of OTCs did not affect Rs. These results implied that a higher warming did not result in a higher Rs but a greater soil drying. Therefore, a higher warming may not cause a higher soil respiration, which was most likely due to the fact that a higher warming may result in a greater soil drying.
3

Effects of increased precipitation and nitrogen deposition on methane uptake of Alpine meadow in Qinghai-Tibet Plateau: in situ experiments

100%
Guo X., Dail L., Zhang F., Li Y., Lin L., Li Q., Dawen Q., Fan B., Ke X., Cao G., Zhou H., Du Y.
Polish Journal of Ecology
|
2020
|
tom 68
|
nr 2
4

Biomass and nitrogen responses to grazing intensity in an Alpine meadow on the Eastern Tibetan Plateau

100%
Gao Y., Luo P., Wu N., Yi S., Chen H.
Polish Journal of Ecology
|
2007
|
tom 55
|
nr 3
This study was conducted to examine the seasonal dynamics of biomass and plant nitrogen (N) content under three grazing intensities (light grazing – LG: 1.2, moderate grazing – MG: 2.0, and heavy grazing – HG: 2.9 yaks ha⁻¹) in representative alpine meadow on the eastern Tibetan Plateau. Differentiation in grazing intensity in the study area started since 1997 and has continued to the present time. Plant samples were collected in the middle of June, August and September. The highest aboveground biomass occurred at the MG site for both August and September. Over the growing season, belowground biomass (0–30 cm) increased as grazing intensity increased. The total belowground biomass averaged over all sampling dates was 1226, 1908 and 2244 g m⁻² for LG site, MG site and HG site, which accounted for 75, 81 and 88% of total biomass, respectively. The results suggested that grazing intensity changed biomass allocation pattern between aboveground and belowground parts of plants. Higher grazing intensity resulted in higher N concentration in both live and dead aboveground biomass over the study period. Increased grazing intensity tended to increase plant N content averaged over all sampling dates, which were 17.9 g m⁻², 23.8 g m⁻² and 27.6 g m⁻² in LG site, MG site and HG site. The results indicated that higher grazing intensity had a potential to increase the ecosystem pool of plant N.
5

Impact of altitude diversity on the phosphorus content in Chornohora soils [Eastern Carpathians, Ukraine]

84%
Chodorowski J., Melke J.
Polish Journal of Soil Science
|
2009
|
tom 42
|
nr 1
69-76
In this paper the results of studies on three different forms of phosphorus – total, organic and inorganic – in soils of the Chornohora massif (Eastern Carpathians, Ukraine), depending on altitude, have been presented. The studied gleyed acid brown soils are situated in the belt of alpine meadows (1760 and 2057 m a.s.l.) and in the forest layer (1020 and 1120 m a.s.l.).
6

Effects of the conversion of a degraded alpine Kobresia meadow on the organic carbon and nitrogen of soil and plants

84%
Qiao Y., Duan Z., Li X., Quan X., Liang H.
Polish Journal of Ecology
|
2015
|
tom 63
|
nr 4
Three sites with both degraded alpine Kobresia meadow (DM) and adjacent mix-seeded perennial grasses pastures (MSP) in the headwater region of the Yellow River, Qinghai-Tibetan Plateau, were selected to investigate plant and soil organic carbon (SOC), total nitrogen (TN) and their isotope composition. The SOC and TN in the top soil layer to a depth of 10 cm were significantly affected by ploughing and planting mix-seeded perennial grasses. The SOC content in 0–10 cm soil layer of MSPs was 25.6%, 5.5% and 12.9% lower than those of DMs at the I-III sites, respectively, and the rate of OC density loss was 23.8, 14.5 and 18.2%, respectively. The soil TN content in 0–10 cm soil layer of MSPs was 16.6%, 2.2% and 9.4% lower than those of the DMs at three sites, respectively, and the TN density was 15.6, 10.6 and 15.3% lower than those of DMs, respectively. The plant and soil ¹³C values (-27.03‰, -25.16‰, respectively) suggest that the vegetation of both DMs and MSPs are C₃ plant communities. The 15 N value in the soil (>4‰) was significantly greater than in plants (<2‰). No differences of either ¹³C or ¹⁵N abundance between MSPs and DMs at Site I and II, but were found at Site III, indicating that the effects were site specific. The rehabilitation of a degraded Kobresia meadow has a significant influence on the soil properties, SOC and TN. Caution should be taken in site selection before performing conversion.
7

Invasion of Descurainia sophia [L.] [Cruciferae] in Alpine meadow is enhanced by ground disturbance made by Myospalax fontanierii [Milne-Edwards]

84%
Li W., Zhang Y., Wang Y.
Polish Journal of Ecology
|
2009
|
tom 57
|
nr 2
389-393
Because of cold weather and extremely harsh environment, there is few exotic species in Qinghai-Tibetan Plateau. Plateau zokor (Myospalax fontanierii), dominant borrowing small mammal, plays a role as ‘ecosystem engineer’ in alpine meadow ecosystem. We measured and compared the dispersion area, branches, height and number of branches of flixweed tansymustard (Descurainia sophia) on the area disturbed by zokor mounds and in the undisturbed alpine meadow. Flixweed tansymustard is cool-season annual or biennial typical farmland weed in China, and is not found in alpine meadow before. The results indicated that zokor mounds significantly increased the dispersion area, number of individuals in each dispersion area, height and number of branches of flixweed tansymustard on the area disturbed by zokor mounds compared to those in undisturbed alpine meadow. These results suggest that ecosystem engineering by native species of rodent could promote the invasions of alien plant species in alpine meadow ecosystem, leading to higher abundances of invaders.
8

Relationship between seed size and plant abundance in an alpine meadow of the Qinghai-Tibetan Plateau

84%
Liu B., Luo Y.
Polish Journal of Ecology
|
2009
|
tom 57
|
nr 3
573-579
Theoretical and field studies on seed size and plant abundance relationship have been conducted in various communities. However, inconsistent patterns have emerged from these studies, and still little is known about alpine meadows. Here we identified four models and their predictions: the seed size/number trade-off model (SSNTM), the succession model (SM), the spatial competition model (SCM), and the triangle model (TM), in order to assess the relationship between seed size and abundance in alpine meadows, and to elucidate underlying mechanisms. The study site was situated on the eastern Qinghai-Tibetan Plateau at 3500 m above sea level. From 1999 through 2001, two indices of plant abundance (aboveground biomass and density) were simultaneously measured in 45 quadrates (0.25 m²). Data for 101 plant species (mostly Cyperaceae, Poaceae, Asteraceae, Ranunculaceae and forbs) showed that seed size is like log normal distributed, and it slightly skewed in smaller-sized seeds. The SSNTM, the TM, the SM and the SCM models were not supported in this alpine meadow, and the relationship between seed size and abundance was always positive (although in some samples, the relationship was not significant). The positive correlation between seed size and abundance observed for some grassland communities was also demonstrated in the alpine meadow. It suggests that seed size depends on the plant growth form, but the biomass-density relationship is inconsistent with previous studies. This suggests that the measure of abundance used in these studies is not the only reason for inconsistency of seed size.
9

Leaf morphology shift of three dominant species along altitudinal gradient in an Alpine meadow of the Quinghai - Tibetan Plateau

84%
Zhong M., Wang J., Liu K., Wu R., Liu Y., Wei X., Pan D., Shao X.
Polish Journal of Ecology
|
2014
|
tom 62
|
nr 4
It has been observed that leaf morphology shift within species is linked to climate change, but there are few studies on the effects of altitude change on leaf morphology of species. We hypothesized that similar to climate change, a morphological shift within species would occur over time under different growing altitudes. In this study, we evaluated three dominant grass species: Elymus nutans Griseb., Kobresia capillifolia Clarke., Carex moorcroftii Boott., taking advantage of the altitudinal variations (3000-4000 a.s.l.) on the Qinghai-Tibetan Plateau. Our study showed that almost all leaf traits of these three species had significant differences (P <0.05) across an altitudinal gradient. Different species responded differently to altitude change. Leaf thickness (LT) of the three species increased with increase in altitude. Leaf area (LA) of E. nutans and C. moorcroftii decreased with increasing altitude, but that of K. capillifolia increased. There was no obvious linear effect on leaf dry matter content (LDMC) and specific leaf area (SLA) of these three species. LDMC of E. nutans and C. moorcroftii showed a trend of increase, while that of K. capillifolia decreased. SLA of E. nutans and K. capillifolia showed a trend of increase, but that of C. moorcroftii decreased with increase in altitude. In addition, soil pH (pH) and air temperature (AT) decreased with increase in altitude. However, other soil and climate factors increased as altitude increased. The finding of this work is that leaf morphology shift within species happens under altitude change to adapt to specific environment.
10

Aerobic methane emission from plant: comparative study of different communities and plant species of Alpine meadow

84%
Guo X., Du Y., Li J., Liu S., Han D., Li Y., Lin L., Zhang F., Oyang J., Cao G.
Polish Journal of Ecology
|
2015
|
tom 63
|
nr 2
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.
11

Initial effects of experimental warming on temperature, moisture and vegetation characteristics in an Alpine meadow on the Qinghai-Tibetan Plateau

84%
Xu M.-H., Peng F., You Q.-G., Guo J., Tian X.-F., Liu M., Xue X.
Polish Journal of Ecology
|
2014
|
tom 62
|
nr 3
The ongoing warming in the Qinghai-Tibetan Plateau leads to changes in ecosystem processes while the responses of soil and vegetation are not well understand. Thus, we used infrared radiators to carry out experimental warming from July 2010 to August 2011 in an alpine meadow on the Plateau (about 4630 m above sea level) to research the responses of environmental factors and vegetation characteristics to short-term warming (1 year). The experimental design was a block design consisting of five replications and included three treatment levels: control, T1 (130 W m–2) and T2 (150 W m–2). The results showed that air temperature at 20 cm height, surface temperature and soil temperature in the 0–100 cm layers increased with warming. The biggest differences of T1 (1.66°C) and T2 (2.34 °C) appeared on the surface and at 20 cm depth, whereas the biggest amplitudes of T1 (27.15%) and T2 (35.81%) all occurred at 100 cm depth. Soil moisture showed different trends with warming in different soil layers. In the 0–40 cm layers, soil moisture decreased with warming. The biggest differences (–2.97% for T1 and –2.73% for T2) and amplitudes (–18.07% for T1 and –16.64% for T2) all appeared at 10 cm depth. In the 60–100 cm layers, soil moisture increased with warming. The biggest differences (2.53% for T1 and 6.45% for T2) and amplitudes (11.39% for T1 and 29.05% for T2) all occurred at 100 cm depth. Relative to control, vegetation height and aboveground biomass increased significantly in T1 and T2 (P <0.05), while vegetation coverage had not significant differences in T1 and T2 (P> 0.05). In T1 and T2, the amplitudes were 30.67% and 30.19% for vegetation height, and 36.22% and 27.87% for vegetation aboveground biomass, and 12.89% and 4.42% for vegetation coverage, respectively. In the path analysis between environment and vegetation properties, vegetation was directly affected by soil moisture at 40 cm and 60 cm depths, whereas indirectly influenced by relative humidity at 20 cm height and soil temperature at 40 cm depth. This might be related to the downward movement of the soil moisture caused by warming.
12

Summer diet of two sympatric species of raptors Upland Buzzard [Buteo hemilasius] and Eurasian Eagle Owl [Bubo bubo] in Alpine meadow: problem of coexistence

84%
Cui Q., Su J., Jiang Z.
Polish Journal of Ecology
|
2008
|
tom 56
|
nr 1
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 (Cue = 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.
13

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

67%
Qiao Y., Wang Q., Wang W.
Polish Journal of Ecology
|
2009
|
tom 57
|
nr 4
769-777
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 × 1 m quadrates in each treatment. Above-ground biomass was measured in five 0.5 × 0.5 m quadrates. Shrub, forb, graminoid and sedge plant materials were clipped at ground level and oven-dried at 85ºC 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.
14

Effects of freezing and freeze-thaw cycles on soil microbial biomass and nutrient dynamics under different snow gradients in an Alpine meadow (Tibetan Plateau)

67%
Liu L., Wu Y., Wu N., Xu J., Mao Y., Luo P., Zhang L.
Polish Journal of Ecology
|
2010
|
tom 58
|
nr 4
In alpine zones, cold season processes, particularly those associated with snow accumulation and ablation, have a central role in ecosystem functioning. However, we know very little about soil carbon and nitrogen processes under the snowpack in these ecosystems, including the Tibetan Plateau. We conducted an experiment comparing three snow regimes (11 m × 1 m plots) of different snow depths and durations at an altitude of 4,100 m in the Minshan Range on the eastern Tibetan Plateau. The three snow regimes included a shallow and short duration snowpack (SS; depth <10 cm), a moderate snow depth and medium duration snowpack (MS; depth <20 cm), as well as a deep and long duration snowpack (DS; depth > 30 cm). This study explores the effects of different snow conditions on soil temperature, and further describes the sequence and timing of dissolved nutrients and microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) in soils under different snow regimes during the autumn-winter transition (i.e. November 7, 2008 – March 7, 2009). Three successive phases of temperature change were distinguished: I – initial decline – soil temperatures dropped steadily from 4°C to about 0°C at the same rate for all three snow regimes; II – moderate freezing – soil temperatures fluctuated between 0°C and –7°C under all three snow regimes; III – multiple freeze-thaw cycles took place in the SS and MS regimes, but permanent freezing occurred in the DS regime. Under moderate freezing, we found that soil temperature fluctuation was an essential factor for the transformation of soil C and N. Our results indicate that larger temperature fluctuations correlate with a greater increase in dissolved organic nitrogen (DON) content. Dissolved organic carbon (DOC) content increased markedly only under the most drastic temperature fluctuations. In contrast, MBC content increased significantly only when soil temperatures were relatively steady. Under the permanent freezing, only a large number of freeze-thaw cycles caused a significant decline of NO₃⁻–N and DOC concentrations. DON content declined markedly under permanent freezing and multiple freeze-thaw cycles. However, MBC content declined significantly only under permanent freezing. Ultimately, multiple freeze-thaw cycles resulted in the export of dissolved nutrients (organic and inorganic nitrogen) from the alpine ecosystem which had previously accumulated in the moderate freezing phase of the soil.
15

Simulating N2O emission from Kobresia humilis Serg. alpine meadow on Tibetan Plateau with the DNDC model

67%
Du Y., Cui X., Cao G., Zhao X., Yang G.
Polish Journal of Ecology
|
2011
|
tom 59
|
nr 3
Field me asured N2O emissions in two years were used to parameterize and validate a process-based model, DNDC, for an alpine Kobresia humilis meadow on the Tibetan Plateau in China. Although this model failed to capture the N2O fluxes in some time periods in the spring or autumn, the modeled results showed overall a good performance in terms of simulating the seasonal variation of N2O fluxes and quantifying the annual total emissions. The relative deviation on the annual basis was about 12.4% and –15.9% for the two years, respectively. The modeled data showed that nitrification contributed about 53% of total N2O production, slightly higher than denitrification. The modeled fluxes were sensitive to soil organic content (SOC), pH, and temperature, but less sensitive to variation of precipitation, soil ammonium and nitrate contents. Further mo difications for the model were suggested to focus on the process of soil freezing and thawing as well as the crop growth sub-model that would improve the model’s performance for quantifying N2O emission from the alpine meadow.
16

The effect of habitat on methane emission from an alpine wetland

67%
Chen H., Wu N., Gao Y., Yao S., Wang Y., Tian J., Sun G., Yuan X.
Polish Journal of Ecology
|
2009
|
tom 57
|
nr 2
377-381
Alpine wetland is a source for methane (CH₄), an important greenhouse gas, but little is known about how this habitat influences the emission. To understand this wetland habitats were selected at the altitude of 3430 m a.s.l. (in National Wetland Nature Reserve of Zoige, Quingle – Tibetan Plateau) and the methane flux was measured with static chambers in three different sites, including hollows with Carex muliensis Hand – Mazz. and Eleocharis valleculosa Ohwi f. setosa (Ohwi) Kitagawa., grass hummocks composed of Kobresia tibetica Maxim, Cremanthodium pleurocaule R. D. Good, Potentilla bifurca L. and Pedicularis sp. We have found that in alpine wetland these habitats significantly affect CH₄ emissions in the onset (April, 2006) and peak (August, 2005) stages of growing season.Hollows covered with Carex muliensis and Eleocharis valleculosa had higher values of emission than grass hummocks built by several grass species. Slight difference of CH₄ emission was found between two kinds of hollows with Carex muliensis and Eleocharis valleculosa. These results were consistent with the change of water table, which was found best correlated with CH₄ emissions (r²= 0.43, P <0.01) in the peak stage of growing season. Directly measured shoot biomass and plant heights were best related to CH₄ emissions (r²= 0.59, P <0.01). However, in the onset stage of growing season, variation of CH₄ emission may not be simply ascribed to changes in water table and vegetation structure.
17

Effects of seed mass and light on seedling success in Artemisia sieviersiana Willd in the Tibetan Plateau

67%
Wu G.-L., Li W., Du G.-Z.
Polish Journal of Ecology
|
2010
|
tom 58
|
nr 3
Seed mass and light availability are important factors which affect seedling recruitment in plant populations. Effects of seed mass and light availability on seed germination and seedling recruitment in Artemisia sieversiana Willd, which is a widely distributed herbs and a common component species in alpine meadows of the Tibetan Plateau, were tested in a manipulative field experiment. Our research indicated that seed mass and light significantly affected seed germination and seedling emergence and survival and there was a significant interaction effect between seed mass and light availability on these life traits within species. Our study showed that larger seeds presented significant advantages in germination, seedling emergence and survival than smaller seeds under different light availability, especially under deep shade. Our results suggested that seedling success of Artemisia sieversiana appears to be regulated by an interactive effect of seed mass and light availability in alpine meadow of the Qinghai-Tibetan Plateau. In addition, seedlings from larger seeds have more and more stronger advantages from germination, emergence to survival stage than seedlings from smaller seed within species.
18

Effects of livestock exclusion on vegetation and soil properties under two topographic habitats in an Alpine meadow on the Eastern Quinghai - Tibetan Plateau

67%
Shi F., Chen H., Wu Y., Wu N.
Polish Journal of Ecology
|
2010
|
tom 58
|
nr 1
Long-term overgrazing has resulted in grassland deterioration and even desertification on the eastern Qinghai-Tibetan Plateau. In this paper, we examined the characteristics of vegetation and soil properties in the livestock-excluded pastures and the adjacent grazed pastures under two topographic habitats (the flat valley and the south-facing slope). Seven-year exclusion of livestock has enhanced aboveground live biomass, root biomass and litter accumulation. Livestock exclusion has also increased soil bulk density and soil water content, soil organic C concentration, total N concentration and its transformation rate, and soil microbial activity. The results showed that livestock exclusion has facilitated vegetation recovery and improved physical, chemical and biological properties of soil. However, livestock exclusion has significantly decreased graminoid biomass accumulation, especially on the flat valley, the biodiversity also significantly decreased there. The results suggested that long-term livestock exclusion was disadvantageous for palatable forage production and biodiversity protection on the flat valley. Compared to the flat valley, the grassland on the south-facing slope was under more severe degradation, and the reversion was in a slower process. Thus, the optimal grassland management in the livestock-excluded pasture on the flat valley should include a low or moderate grazing intensity or adopt an alternate grazing system, but more effective and even longer livestock exclusion practice should be taken on the south-facing slope.
19

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

67%
Zhang R., Gou X., Bai Y., Zhao J., Chen L., Song X., Wang G.
Polish Journal of Ecology
|
2011
|
tom 59
|
nr 1
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 nutrie nt use e fficiency (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 explo red t he 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 f ound 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 veget ation. Graminoids re tained lower concentrations of leaf N and P than forbs in community on the Nlimited 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 w ere able to resist low levels of nutrient availability on the natural alpine grassland when compared to forbs.
20

The effects of protective enclosure on vegetation diversity, and productivity of degraded Alpine Kobresia meadow [Qinghai-Tibetan Plateau]

67%
Li S., Wang Q., Jing Z., Wang W.
Polish Journal of Ecology
|
2009
|
tom 57
|
nr 3
495-502
Grassland degradation due to anthropogenic and natural factors and their interactions is one of the worldwide ecological and economic problems because it reduces grassland productivity and diversity and leads to desertification. The objective of this study was to assess the influence of protective enclosure on vegetation composition and diversity and plant biomass of an alpine degraded meadow. The experiment was conducted at center of Qinghai-Tibetan Plateau with two degraded (caused by overgrazing) alpine meadows: the lightly and severely degraded ones (LD and SD) and their enclosed areas with iron net (LDE and SDE, respectively). The areas 200 m × 150 m for each of four degraded alpine meadow treatments at average altitude 3,960 m a.s.l. were set for research. The lightly degraded plots were dominated by Scirpus distigmaticus (Kukenth.) Tang et Wang, Elymus nutans Griseb. and Oxytropis ochrocephala Bunge. The dominating plants in severely degraded plots were: Artemisia sieversiana Ehrhart ex Willd, Ajania tenuifolia (Jacq.) Tzvel, Lonicera minuta Batal. The results showed: (1) the vegetation cover of two degraded plots (LD and SD) has increased after taking the enclosure measures and the forbs dominated both plots. (2) Species richness has also increased in two enclosed degraded plots, respectively. There no significant differences in evenness and diversity between LD and LDE, and SD and SDE, respectively. (3) Enclosure may promote aboveground biomass, particularly grass and forb biomass in LD, and forb biomass in SD plots.
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