Alpine Meadow Of Qinghai-Tibetan Plateau Research Articles

Grazing Changed Plant Community Composition and Reduced Stochasticity of Soil Microbial Community Assembly of Alpine Grasslands on the Qinghai-Tibetan Plateau.

Grazing is a substantial threat to the sustainability of grassland ecosystems, while it is uncertain about the variety of plant and soil microbial community and the linkages between them limit the comprehensive understanding of grazing ecology. We conducted an experiment on the effects of the grazing regimes rotational grazing (RG), continuous grazing (CG), and grazing exclusion (GE) on an alpine meadow in Qinghai-Tibetan Plateau. The differences of plant community composition, soil microbial community assembly mechanism, and taxonomic and functional composition between grazing regimes were examined, and the relationship between plant species and the soil microbes was assessed by constructing a co-occurrence network. The results showed that the plant community composition varied with the grazing regimes, while the soil microbial community composition did not vary with the grazing regimes. The soil bacterial functional composition was similar under RG and CG, while the soil fungal functional composition was similar under GE and RG. The soil microbial community under all grazing regimes was assembled mainly according to stochastic rather than deterministic mechanisms, and RG and CG reduced the relative importance of the stochastic ratio. At the microbial phylum level, CG and GE increased the relative abundance of Acidobacteria and Armatimonadetes and CG and RG increased the relative abundance of Elusimicrobia. In the network of plant species and soil microbial classes, plants and bacteria themselves were mainly positively linked (symbiosis and promotion), while plants and soil microbes were mainly negatively linked (competition). There were five microbial generalists in the network, which connected with many microbes, and four showed no difference in their abundance among the grazing regimes. Overall, the stable key microbes in the network and the fact that many of the plants are unconnected with microbes weakened the impact of grazing-induced changes in the plant community on soil microbes, probably resulting in the stable soil microbial community composition. Moreover, there was still a dominant and tolerant plant species, Kobresia pygmaea, that connected the plant and microbial communities, implying that the dominant plant species not only played a crucial role in the plant community but also acted as a bridge between the plants and soil microbes; thus, its tolerance and dominance might stabilize the soil microbial community.

The Conclusion of ‘Lateral Flow between Bald and Vegetation Patches Induces the Degradation of Alpine Meadow in Qinghai-Tibetan Plateau’ is Inaccurate

The “Type of Article” of this paper is “Letter to the Editor”. This paper discuses about: “The Conclusion of ‘Lateral Flow between Bald and Vegetation Patches Induces the Degradation of Alpine Meadow in Qinghai-Tibetan Plateau’ is Inaccurate”. No formal abstract is available. Readers are requested to read the full article.

Explaining variation in productivity requires intraspecific variability in plant height among communities

AbstractWhile recent studies have shown the importance of intraspecific trait variation in the processes of community assembly, we still know little about the contributions of intraspecific trait variability to ecosystem functions. Here, we conducted a functional group removal experiment in an alpine meadow in Qinghai-Tibetan Plateau over 4 years to investigate the relative importance of inter- and intraspecific variability in plant height for productivity. We split total variability in plant height within each of 75 manipulated communities into interspecific variability (TVinter) and intraspecific variability within a community (ITVwithin). Community-weighted mean height among communities was decomposed into fixed community-weighted mean (CWMfixed) and intraspecific variability among communities (ITVamong). We constructed a series of generalized additive mixed models and piecewise structural equation modeling to determine how trait variability (i.e. TVinter, ITVwithin, CWMfixed and ITVamong) indirectly mediated the changes in productivity in response to functional group removal. Community productivity was not only affected directly by treatment manipulations, but also increased with both inter- and intraspecific variability (i.e. CWMfixed and ITVamong) in plant height indirectly. This suggests that both the ‘selection effect’ and a ‘shade-avoidance syndrome’ can incur higher CWMfixed and ITVamong, and may simultaneously operate to regulate productivity. Our findings provide new evidence that, besides interspecific variability, intraspecific trait variability in plant height also plays a role in maintaining net primary productivity.

Different responses of soil C:N:P stoichiometry to stocking rate and nitrogen addition level in an alpine meadow on the Qinghai-Tibetan Plateau

Livestock grazing and nitrogen (N) deposition influenced most grasslands in the world by affecting the element contents and their stoichiometry in soil. Although the individual effects of grazing or N deposition on soil nutrients are well understood, how their interaction effects on soil stoichiometric characteristics are unclear. To reveal the response of soil carbon:nitrogen:phosphorus (C:N:P) stoichiometry to grazing and N deposition, we conducted an experiment in an alpine meadow on the Qinghai-Tibetan Plateau (QTP), which included three stocking rates (0, 8 and 16 sheep ha−1) and four N addition levels (0, 50, 100 and 200 kg N ha−1 yr−1). The results showed that grazing had no significant impact on soil C:N:P stoichiometry. Nitrogen addition significantly increased soil total N and N:P ratio at the stocking rate of 8 sheep ha−1 in the surface soil. The interactive effects of grazing and N addition did not significantly affect soil C:N:P stoichiometry, however, the interplay between grazing and N addition caused vegetation changes, which had indirect effects on soil C:N:P stoichiometry. The differential responses of plants and soil indicated that soil was less sensitive to grazing and N addition than plants. Our findings indicated that N was still a major limit factor for plant growth in the alpine meadow of QTP, and hopefully, provided that stocking rate at 8 sheep ha−1 and N addition at 50 kg N ha−1 yr−1 could be a suitable grassland management technique for soil fertility sequestration in the QTP.

Lateral flow between bald and vegetation patches induces the degradation of alpine meadow in Qinghai-Tibetan Plateau

Bald patches (BPs) are known to accelerate and simultaneously mitigate the process of desertification. However, the mechanisms of these two synchronous actions are little studied in high desert and cold systems; and the incidence of BPs on alpine meadows degradation in Qinghai-Tibetan Plateau (QTP) of China is still unavailable. This study first aims to investigate the soil properties and the erodibility of the system BPs-VPs at the Beiluhe basin in QTP. Then, we adopted dye tracer and HYDRUS-2/3D methods to interpret the water infiltration patterns from point scale to slope scale. The results show that the mattic epipedon layer on the top soil (0–20 cm) of VPs directly reduced the impact of raindrops on alpine meadow; and the adhesion of root system in VPs prevented the soil particles from stripping and washing away by runoff. The soil particles in BPs were easily eroded by rainfall, lowering the ground level of BPs relative to the ground level of VPs. The two patches therefore alternated to form an erosion interface where marginal meadow was likely detached by raindrops, and washed away through runoff. The saturated hydraulic conductivity (Ks) of surface soil (0–10 cm) was 124% higher in BPs than the VPs. Thereby, BPs caused a high spatial variation of infiltration and runoff in QTP. Moreover, this difference in Ks between the two patches conducted to a lateral flow from BPs to VPs, and to soil layers with different water contents. These findings highlight that the water flow features can potentially disturb the processes of freezing-thawing, frost heaves, and thaw slump; and accelerate the alpine meadow degradation. Therefore, land cover such as crop and vegetation should be applied over the bare soil surface to prevent the degradation of alpine meadow.

VARIATION IN GREEN-UP DATE OF KOBRESIA PYGMAEA ALPINE MEADOW IN QINGHAI-TIBETAN PLATEAU DURING 1961–2016

Abstract. Vegetation phenology in Qinghai-Tibetan Plateau (QTP) has been proved to be more sensitive to climate change. The previous researches have reported divergent phonological responses of alpine vegetation in QTP from the analyses of remote sensing data, thus the demand for further analysis based on long-term observed vegetation data becomes more urgent. In the lack of long-term remote sensing monitoring data and ground observation data, phenology model simulation can be used as an effective remedy. In this study, we used a phenology model (unified model, UM) to simulate the green-up date for Kobresia pygmaea alpine meadow, and model evaluation shows that the unified model is able to make reasonable estimation for green-up date derived from satellite observations. Based on the phenology model and its parameters, spatial and temporal changes in green-up dates for Kobresia pygmaea alpine meadow in QTP from 1961 to 2016 were simulated, the results indicated that, the variation in green-up date presented an overall insignificant temporal trend with obvious spatial differences; furthermore, complex stage characteristics about the variation in green-up date were also clearly revealed, the period from 1991 to 2005 could be considered as a turning point, before which the trend was mainly in advan1ce and after which the trend was mainly in delay.

Effects of Warming and N Deposition on the Physiological Performances of Leymus secalinus in Alpine Meadow of Qinghai-Tibetan Plateau.

Warming and Nitrogen (N) deposition are key global changes that may affect eco-physiological process of territorial plants. In this paper, we examined the effects of warming, N deposition, and their combination effect on the physiological performances of Leymus secalinus. Four treatments were established in an alpine meadow of Qinghai-Tibetan plateau: control (CK), warming (W), N deposition (N), and warming plus N deposition (NW). Warming significantly decreased the photosynthetic rate (Anet), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr), while N deposition and warming plus N deposition significantly increased those parameters of L. secalinus. Warming significantly increased the VPD and Ls, while N deposition and warming plus N deposition had a significant positive effect. Warming negatively reduced the leaf N content, Chla, Chlb, and total Chl content, while N deposition significantly promoted these traits. Warming, N deposition, and their combination significantly increased the activity of SOD, POD, and CAT. Besides, warming and warming plus N deposition significantly increased the MDA content, while N deposition significantly decreased the MDA content. N deposition and warming plus N deposition significantly increased the Rubisco activity, while warming showed no significant effect on Rubisco activity. N deposition and warming plus N deposition significantly increased the Fv/Fm, ΦPSII, qP, and decreased NPQ, while warming significantly decreased the Fv/Fm, ΦPSII, qP, and increased NPQ. N deposition strengthened the relations between gs, Chl, Chla, Chlb, Rubisco activity, and Anet. Under warming, only gs showed a significantly positive relation with Anet. Our findings suggested that warming could impair the photosynthetic potential of L. secalinus enhanced by N deposition. Additionally, the combination of warming and N deposition still tend to lead positive effects on L. secalinus.

Nitrogen addition gradient can regulate the environmental filtering of soil potassium or phosphorus in shaping the community assembly of alpine meadow

Abstract Nitrogen (N) deposition and warming leads to environmental gradients that shape plant communities and ecological diversity, space is treated as an equally important variable as the environmental variables in the environmental gradients. The Qinghai-Tibetan Plateau (QTP) is very sensitive to large increases in N deposition rates and warming. Environmental gradients caused by N deposition and spatial factors act as environmental filtering in community assembly by affecting plant functional traits and phylogeny. To investigate the effects of environmental filtering caused by N deposition on the community assembly in alpine meadows, we randomly placed and fertilized at 6 levels of N addition (no N addition, 8 kg N ha-1year−1, 24 kg N ha−1 year−1, 40 kg N ha−1 year−1, 56 kg N ha−1 year−1 and 72 kg N ha−1 year−1) both in a normal (normal precipitation and normal temperature) year and a warm (normal precipitation and warm) year. We used the fourth-corner analysis and extended RLQ (R stands for a matrix of environmental variables by samples, L stands for a species-cover-by-samples matrix and Q stands for a species-by-traits matrix) through multiple factors (soil factors, spatial heterogeneity, species traits, phylogenetic factor) to examine the effects of environmental filtering on the community assembly in alpine meadows. The results demonstrated that all soil variables showed a clear gradient and were affected by simulated N deposition; N addition at 8 kg N ha-1year−1 can filtrate the species of the gramineae, but N addition at 72 kg N ha−1 year−1 can filtrate the species of non-gramineae, the main factors of environmental filtering were potassium in normal year and phosphorus in warm year. With the increase of N deposition rate in alpine meadow of QTP, non-gramineous plants will be favored first, but eventually gramineous plants will occupy the dominant position in the QTP. Rational mitigation strategies should be developed for different climate change scenarios of alpine grasslands on the QTP according to their responses to the N addition gradients and climate change scenarios in the future.

Effects of simulated N deposition on photosynthesis and productivity of key plants from different functional groups of alpine meadow on Qinghai-Tibetan plateau

Nitrogen (N) deposition may alter physiological process of plants in grassland ecosystem. However, little is known about the response mechanism of individual plants in alpine regions to N deposition. We conducted a field experiment, and three treatments including 0 kg Nha-1year-1 (CK), 8 kgNha-1year-1 (Low N), and 72 kg N ha-1 year-1 (High N) were established to simulate N deposition in alpine meadow of Qinghai-Tibetan plateau. Our objectives were to determine the influence of N deposition on photosynthesis of different functional types of herbage species in alpine meadow, and finally characterize the links of plant productivity and photosynthesis with soil nutrients. The results showed that responses of alpine plants were species-specific under N deposition. Compared with grass species Agropyron cristatum and forb species Thalictrum aquilegifolium, the sedge species Carex melanantha was much more sensitive to N deposition; a lower N load (8 kgNha-1year-1) can cause a negative effect on its photosynthesis and productivity. Additionally, N deposition can promote plant N uptake and significantly decreased the C (carbon)/N (nitrogen) ratio. Compared with CK and low N deposition, high N deposition inhibited the photosynthesis and growth of the forb species Thalictrum aquilegifolium and sedge species Carex melanantha. In all three functional types of herbage species, the grass species A.cristatum tended to show a much higher photosynthetic capacity and better growth potential; thus, suggesting that grass species A.cristatum will be a more adaptative alpine plants under N deposition. Our findings suggested that plant photosynthetic responses to N deposition were species-specific, low N deposition was not beneficial for all the herbage species, and N deposition may change plant composition by the differential photosynthetic responses among species in alpine grassland. Plant composition shift to grass-dorminant in alpine regions might be attributed to a much higher photosynthetic potential and N use efficiency of grass species.

Response of ammonium oxidizers to the application of nitrogen fertilizer in an alpine meadow on the Qinghai-Tibetan Plateau

The alpine meadows in Qinghai-Tibetan Plateau is an ecosystem sensitive to environmental changes. As part of a study on global climate change and the effects of N precipitation on soil microbiota, we fingerprinted ammonium oxidizing archaea (AOA) and bacteria (AOB) in relation to the N supplement in an alpine meadow in Qinghai-Tibetan Plateau. The results showed that nutrient content in the studied soil was significantly varied in different months (sampling period) but not influenced by the N supplement rate. Long-term nitrogen input dramatically changed the abundance and community composition of the AOB but exerted no obvious effect on the AOA community in the tested soil. Significant differences in the abundance and composition of AOA were recorded in different months. Our findings implied that 1) the soil fertility and physicochemical features of the studied alpine meadows in Qinghai-Tibetan Plateau were stable even under the long-term high N supply; 2) AOB might be the active nitrifiers responding to the high N supply, while the AOA were the abundant and stable nitrifiers despite the N supply; 3) sampling periods mainly affected the abundance and community composition of the nitrifiers in the tested alpine meadow; and 4) the AOB in the studied area are psychrotrophs. Therefore, despite the enhancement of plant growth, high N supplements in the tested alpine meadow ecosystems might cause more pollution to water and air, which in turn contributes to global climate change.

Effects of zokors (Myospalax baileyi) on plant, on abiotic and biotic soil characteristic of an alpine meadow

The population of plateau zokor (Myospalax baileyi) has markedly increased on the degraded alpine meadow of Qinghai-Tibetan plateau. Zokors build mounds that alter plant and soil nutrients as well as biotic communities. This study explored changes in biotic and abiotic features of the community on zokor mounds of different ages (one year, and five-six year, referred to as ZM-1, and ZM-5-6) and undisturbed alpine meadow (CM) in the eastern Qinghai-Tibetan Plateau. Significant difference of four plant functional groups on the CM, ZM-1 and ZM-5-6 indicated the grass and sedge plants have led the recovery, and the forb plants lag behind the legumes in the process of restoration in disturbed alpine meadow. Redundancy analysis (RDA) identified that variance in soil microbial communities are mainly explained by the interacting effects of soil physicochemical properties and plant community characteristics. The results also demonstrate that influence of zokors on alpine meadow restoration is complex. While it is clear that intermediate concentrations of zokors appear to enhance the recovery process, it is also clear that the positive feedback between degradation and zokor population dynamics can lead to zokor population levels that cause degradation and retard recovery. A management challenge then becomes how to maintain these intermediate zokor populations and thus maximize meadow recovery.

Effects of yak dung patch dropped in cold season on soil and pasture on the Qinghai-Tibetan Plateau

To clarify how dung patches from grazing yaks affect soil and pasture in the alpine meadow of Qinghai-Tibetan Plateau, yak dung was collected, mixed and redistributed in a cold grazing season. The soil physical and chemical properties and forage growth were then monitored under the yak dung patch, and 10cm and 50cm from the edge of yak dung patches. The result has shown that yak dung significantly improved soil moisture, total organic matter, and soil available N and P under or close to the dung patches. The forage production at 10cm from the dung patch (303g/m2) was significantly higher than that at 50cm from the dung patch (control) (284g/m2) in the second year, while the production was similar to the control in the first and the third year. The process of yak dung decomposition was slow and yak dung remains were observed 3years after the drop. The dung patches also formed a strong ‘shell’, very difficult for plant underneath to penetrate and grow. Therefore, almost all plants under yak dung patches died, leading to decline in forage yield in the first, second, and the third year. In practice in the Qinghai-Tibetan Plateau regions, yak dung is often collected as fuel by the local farmers. Removing yak dung from alpine meadow may on one hand lead to losses in soil nutrients, but on the other hand reduces some of the negative effects, e.g. the reduction of forage yield under yak dung patches.

Geochip-based analysis of microbial communities in alpine meadow soils in the Qinghai-Tibetan plateau

BackgroundGeoChip 3.0, a microbial functional gene array, containing ~28,000 oligonucleotide probes and targeting ~57,000 sequences from 292 functional gene families, provided a powerful tool for researching microbial community structure in natural environments. The alpine meadow is a dominant plant community in the Qinghai-Tibetan plateau, hence it is important to profile the unique geographical flora and assess the response of the microbial communities to environmental variables. In this study, Geochip 3.0 was employed to understand the microbial functional gene diversity and structure, and metabolic potential and the major environmental factors in shaping microbial communities structure of alpine meadow soil in Qinghai-Tibetan Plateau.ResultsA total of 6143 microbial functional genes involved in carbon degradation, carbon fixation, methane oxidation and production, nitrogen cycling, phosphorus utilization, sulphur cycling, organic remediation, metal resistance, energy process and other category were detected in six soil samples and high diversity was observed. Interestingly, most of the detected genes associated with carbon degradation were derived from cultivated organisms. To identify major environmental factors in shaping microbial communities, Mantel test and CCA Statistical analyses were performed. The results indicated that altitude, C/N, pH and soil organic carbon were significantly (P < 0.05) correlated with the microbial functional structure and a total of 80.97% of the variation was significantly explained by altitude, C/N and pH. The C/N contributed 38.2% to microbial functional gene variation, which is in accordance with the hierarchical clustering of overall microbial functional genes.ConclusionsHigh overall functional genes and phylogenetic diversity of the alpine meadow soil microbial communities existed in the Qinghai-Tibetan Plateau. Most of the genes involved in carbon degradation were derived from characterized microbial groups. Microbial composition and structures variation were significantly impacted by local environmental conditions, and soil C/N is the most important factor to impact the microbial structure in alpine meadow in Qinghai-Tibetan plateau.

Influence of simulated warming using OTC on physiological–biochemical characteristics of Elymus nutans in alpine meadow on Qinghai-Tibetan plateau

Elymus nutans Griseb. is a typical important plant species in the alpine meadow of Qinghai-Tibetan plateau. To examine the effects of temperature elevation on its physiological and chemical characteristics, a simulation study was conducted in situ with open-top chambers (OTC) followed the method of International Tundra Experiment (ITEX) from November 2002 to September 2007, and these OTCs were designed five kinds of size with bottom diameters of 0.85, 1.15, 1.45, 1.75, 2.05 m so as to rise different air temperatures. The air temperature inside OTCs increased by 2.68, 1.57, 1.20, 1.07 and 0.69 °C with increase of OTC diameter compared with ambient air. We found that with increase of air temperature, the soluble sugar content and SOD (superoxide dismutase) activity in leaves of E. nutans increased first, and then decreased, whereas, the soluble protein content and GSH (Glutathione) content decreased first and increased then, the chlorophyll a and total chlorophyll contents were decreased, but the contents of chlorophyll b were higher than that of control. Increased temperature enhanced the above-ground biomass and blade height of E. nutans. These results indicated that elevated temperature had significant and complicated effects on physiological–biochemical characteristics of E. nutans on Qinghai-Tibet plateau, when the temperature increased within the range of 0.69–1.57 °C, it may have positive effects on plant growth and development, and E. nutans could adapt even develop defensive strategy to the changes of a certain ecological environment changes.

The construction of Grassland Degradation Index for Alpine Meadow in Qinghai-Tibetan Plateau

Diagnosing the degradation degree of grassland ecosystem is the basis for ecological restoration. However, there is no literature documenting how to quantify the grassland degradation degree by using visible indicators. In this study, an integrated degradation index was developed to assess the grassland condition on the basis of applicability and certainty analysis through a cases study from degraded alpine grassland on Qinghai-Tibetan Plateau of China.

Establishment of Elymus natans improves soil quality of a heavily degraded alpine meadow in Qinghai-Tibetan Plateau, China

Elymus natans is a dominant native species widely planted to restore the heavily degraded alpine meadows in Qinghai-Tibetan plateau. The objective of this study was to determine how E. natans establishment affected the quality and fertility of a heavily degraded soil. Soil samples (at depths of 0-10, 10-20 and 20-30 cm) were collected from the 3- and 7-year-old E. natans re-vegetated grasslands, and in the heavily degraded alpine meadow (control). The establishment of E. natans promoted plant cover and aboveground biomass. Compared to the non-reseeded meadow, the concentration of total organic C increased by 13% in the soil under 3-year-old reseeded E. natans grassland at 0-10 cm, and by 7-33% in the soil under 7-year-old reseeded E. natans grassland at 0-10, 10-20 and 20-30 cm depths. Rapid increases in total and available N were also observed in two E. natans re-vegetated grasslands, especially in the 0-10 cm soil layer. Across three sampling depths, total P concentration was increased by 17-35% and 18-54% in 3- and 7-year-old reseeded soil respectively, compared to the soil of control. After 3 years of E. natans growth, microbial biomass C increased by 13-58% at 0-10 and 10-20 cm layers; while it increased by 43-87% in 7-year-old reseeded treatment at 0-10, 10-20 and 20-30 cm depths relative to control. A similar increasing trend was observed for microbial biomass N and P generally. Significant increase in neutral phosphatase, urease, catalase and dehydrogenase was also found in 3- and 7-year-old re-vegetated grasslands compared with heavily degraded meadow. Our results suggest a significant positive impact of E. natans establishment on soil quality. Thus, E. natans establishment could be an effective and applicable measure in restoring heavily degraded alpine meadow in the region of Qinghai-Tibetan Plateau.

Response of Seedling Root of Six Herbaceous Species to Light and Nutrient in Alpine Meadow of Qinghai-Tibetan Plateau

Response of Seedling Root of Six Herbaceous Species to Light and Nutrient in Alpine Meadow of Qinghai-Tibetan Plateau