Small semi-fossorial herbivores can affect plant aboveground biomass (AGB) in grasslands and possibly alter the allocation of AGB and belowground biomass (BGB). In this study, plateau pika (
) was ...used to investigate such effects at three alpine meadow sites on the Eastern Tibetan Plateau, where pairs of disturbed vs. undisturbed plots were randomly selected and sampled. We also explored the relationships between soil properties and BGB/AGB across the plots in the presence and absence of plateau pikas, respectively. We found that BGB and BGB/AGB were 11.40 and 8.20% lower in the presence of plateau pikas than in their absence, respectively. We also found that the BGB/AGB was positively related to soil moisture and soil total nitrogen (STN) in the absence of plateau pikas. In contrast, BGB/AGB was positively related to STN, soil organic carbon (SOC), soil carbon/nitrogen (C/N), and soil total phosphorus in the presence of plateau pikas. These factors indicated plateau pika disturbance increased AGB allocation. The relationship between AGB and BGB of alpine meadow plants to soil variables was also different between sites with and without plateau pika disturbance. In conclusion, small semi-fossorial herbivore disturbance is likely to alter grassland carbon stock and should be well controlled for sustainable conservation and management of alpine meadows on the Tibetan Plateau.
Herbivores can influence plant species richness and plant aboveground biomass. However, only a few studies have examined their impact on the relationship between plant aboveground biomass and plant ...species richness, focusing on large herbivores. This study examined the influence of a small burrowing herbivore, the plateau pika (Ochotona curzoniae) with averaging 150 g, on the plant aboveground biomass, plant species richness, and their relationship in the alpine meadows on the Qinghai–Tibet Plateau. The study used a random stratified paired sampling design to collect data on plant species richness and plant aboveground biomass across five sites. Each site contained 10 pairs of plots. Each pair consisted of an undisturbed plot and a disturbed plot. Plant species richness was higher in the disturbed plots; whereas, plant aboveground biomass did not differ in relation to plateau pika disturbance. In the undisturbed plots, the plant species richness increased positively with plant aboveground biomass. In the disturbed plots, the plant species richness peaked at intermediate plant aboveground biomass levels. The findings suggest that small herbivores could alter the relationship between plant aboveground biomass and plant species richness by inducing an increase in plant species diversity, and they should be considered for assessing the management and conservation measures of alpine meadow.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The activity of small mammalian herbivores influences grassland ecosystem services in arid and semi-arid regions. Plateau pika (Ochotona curzoniae) was considered to be a focal organism to ...investigate the effect of small mammalian herbivores on meadow ecosystem services in alpine regions. In this study, a home-range scale was used to measure the forage available to livestock, water conservation, carbon sequestration and soil nutrient maintenance (total nitrogen, phosphorus and potassium) in the topsoil layer, and a quadrat scale was used to assess the biodiversity conservation of alpine meadows. This study showed that the forage available to livestock and water conservation was 19 % and 16 % lower in the presence of plateau pikas than in their absence, and biodiversity conservation, carbon sequestration, soil nitrogen and phosphorus maintenance was 15 %, 29 %, 10 % and 8.9 % higher in the presence of plateau pikas than in their absence. In contrast, it had no impact on soil potassium maintenance of meadow ecosystems in alpine regions. The forage available to livestock, biodiversity conservation and soil nutrient maintenance of meadow ecosystems in alpine regions had maximum values as the disturbance intensity of plateau pikas increased; the water conservation tended to decrease linearly with the increasing disturbance intensity of plateau pikas. These results present a pattern of plateau pikas influencing the ecosystem services of meadow ecosystems in alpine regions, enriching our understanding of the small mammalian herbivores in relation to grassland ecosystem service.
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•Presence and intensity present more information than only presence.•Presence increased soil total nutrients and NO3−-N and NH4+-N.•Different intensities have different influences on ...the soil nutrients.•The largest benefits are associated with 475±90 burrow entrances per ha.
The plateau pika (Ochotona curzoniae), one of the main bioturbators, creates extensive disturbances in the soil of the alpine meadow of the Qinghai-Tibet Plateau (QTP). This study investigated the effects of the presence and intensity of plateau pika disturbances on the main soil nutrients of the Kobresia pygmaea meadow across three study sites in the QTP by using the method of counting the active burrow entrance densities of plateau pika in the field as a representation of the disturbance intensity. Our results showed that the presence of plateau pika significantly increased the soil total nitrogen (TN), soil organic carbon (SOC) and total phosphorus (TP) concentrations and decreased the available phosphorus (AP) concentrations across the three study sites. The presence of plateau pika increased the NO3−-N and NH4+-N concentrations in Luqu County and Maqu County, but had no significant effect on these concentrations in Gonghe County. The soil TN, SOC and TP concentrations showed a downward parabola and the NO3−-N, NH4+-N and AP concentrations showed an upward parabola as the intensity of the disturbances increased in Luqu County and Maqu County. These soil nutrients had a threshold (inflection point) of 475 (475±90) burrow entrances per ha. However, the soil TN, SOC and TP concentrations increased linearly while the NO3−-N, NH4+-N and AP concentrations decreased linearly with the increasing intensity of disturbances in Gonghe County (≤512 burrow entrances per ha). These results implied that the soil nutrient changes induced by plateau pika disturbances are not only related to their presence but are also related to the intensity of the disturbances, and that the most appropriate disturbance intensity (475 (475±90) burrow entrances per ha) of plateau pika was beneficial to the storage of soil carbon and nitrogen in the alpine meadow in the QTP.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Soil salinity is an increasingly serious problem worldwide that reduces agricultural output potential. Selected beneficial soil bacteria can promote plant growth and augment tolerance to biotic and ...abiotic stresses. Bacillus subtilis strain GB03 has been shown to confer growth promotion and abiotic stress tolerance in the model plant Arabidopsis thaliana. Here we examined the effect of this beneficial soil bacterium on salt tolerance in the legume forage crop, white clover. Plants of white clover (Trifolium repens L. cultivar Huia) were grown from seeds with or without soil inoculation of the beneficial soil bacterium Bacillus subtilis GB03 supplemented with 0, 50, 100, or 150 mM NaCl water into soil. Growth parameters, chlorophyll content, malondialdehyde (MDA) content and osmotic potential were monitored during the growth cycle. Endogenous Na(+) and K(+) contents were determined at the time of harvest. White clover plants grown in GB03-inoculated soil were significantly larger than non-inoculated controls with respect to shoot height, root length, plant biomass, leaf area and chlorophyll content; leaf MDA content under saline condition and leaf osmotic potential under severe salinity condition (150 mM NaCl) were significantly decreased. Furthermore, GB03 significantly decreased shoot and root Na(+) accumulation and thereby improved K(+)/Na(+) ratio when GB03-inoculated plants were grown under elevated salt conditions. The results indicate that soil inoculation with GB03 promotes white clover growth under both non-saline and saline conditions by directly or indirectly regulating plant chlorophyll content, leaf osmotic potential, cell membrane integrity and ion accumulation.
A type of quinoxaline-derived tridentate N,N,O-ligand was synthesized in good to excellent yields over three steps through iodination of 2-aryl indoles, sequential Kornblum-type oxidation with DMSO, ...and capture by 1,2-diaminobenzenes. The prepared atropisomeric N,N,O-ligand was successfully applied in the synthesis of N-vinyl cinnamaldehyde nitrones as only Z-isomers in good yields through the Chan-Lam reaction. The method features an easily accessed tunable tridentate N,N,O-ligand, broad substrate scope, good functional group tolerance, and high Z-isomer for N-vinyl nitrones.
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IJS, KILJ, NUK, PNG, UL, UM
Small burrowing herbivores create extensive disturbances to grassland soil, which may change carbon cycling. We focused on the plateau pika (Ochotona curzoniae) to simultaneously investigate the ...responses of the soil organic carbon (SOC) and soil inorganic carbon (SIC) stocks of alpine meadows to the disturbance caused by this small burrowing herbivore and its disturbance intensity at the plot scale across five sites on the Qinghai‐Tibetan Plateau. The percentage of bare soil area in a disturbed plot was used as a proxy for the disturbance intensity of plateau pikas. Our study found that the disturbance by plateau pikas reduced the SIC stock and increased the SOC stock, whereas it had no effect on the soil total carbon (STC) stock. Our study also found that the SOC and STC stocks were higher at intermediate disturbance intensities of plateau pikas, whereas the SIC stock showed a decreasing trend as the disturbance intensity of plateau pikas increased. Our findings suggest that intermediate disturbance intensities of a small burrowing herbivore (plateau pika) improve soil quality by increasing the SOC stock and benefit soil carbon sequestration by increasing the STC stock.
Highlights
Explored the SIC and SOC stocks simultaneously in relation to the disturbance by a small burrowing herbivore.
Soil carbon stocks were evaluated at plot scale across five sites.
SIC and SOC stocks responded differently to the disturbance by plateau pika and its disturbance intensity.
The intermediate disturbance intensities were good for the soil quality and soil carbon sequestration.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Do semi-fossorial herbivores influence the trajectory of plant community succession by altering belowground bud density in alpine meadows? Field surveys were carried out to investigate the effect of ...disturbance and disturbance intensity of the plateau pika (Ochotona curzoniae) on the belowground bud density in alpine meadows at two sites. The Linear Mixed Model (LMM) test and Linear Model (LM) test were used to analyze the relative effect of plateau pika disturbance on bud density and to clarify the response of belowground bud density to disturbance intensity. Our results showed that disturbance by the plateau pika increased belowground bud density of graminoids and plants from the grass and sedge families, including Kobresia pygmaea and Elymus nutans, but had no effect on forbs bud density. The bud density of graminoids, grass and sedge plants, and K. pygmaea and E. nutans showed a downward parabolic trend in response to increased disturbance intensity of the plateau pika, implying that there was an optimal level of disturbance intensity that maximized belowground bud density of graminoids. These results suggest that disturbance by the plateau pika has different effects on belowground bud densities of graminoids versus forbs. Additionally, disturbance by plateau pika up to the optimal intensity may improve grazing quality of alpine meadow in the long term through increasing graminoid bud density, resulting in a higher proportion of graminoids in pasture, while higher levels of disturbance by plateau pika may deteriorate alpine meadows through a reduction in graminoid bud density.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Although grassland degradation simultaneously affects plant productivity and soil nutrient concentrations, the relationship between plant productivity and soil nutrient concentrations during the ...process of grassland degradation is not yet well documented. A 4-year survey in the Qinghai-Tibetan Plateau was conducted to simultaneously investigate the relationships between plant productivity and soil nutrient concentrations in an alpine grassland at an overall degradation level and individual degradation levels. Our results showed that the total plant, sedge, and forb biomasses decreased, whereas the grass and legume biomasses first increased and then decreased as the level of alpine grassland degradation increased. Soil organic carbon (C), total nitrogen (N), total phosphorus (P), available N, and available P concentrations also decreased with the increase in degradation level. Our results also showed that plant productivity was positively correlated with soil nutrient concentrations (soil organic C, total T, total P, available N, available P) at an overall degradation level, whereas plant productivity was positively correlated with only the soil organic C concentration at each degradation level. Our findings suggested that the alpine grassland degradation conditions had different effects on the plant productivity of four functional groups (sedges, grasses, legumes, forbs) and affected the relationship between plant productivity and soil nutrient concentrations.
The presence of burrowing mammals can have extensive effects on plants and soils, creating bare soil patches in alpine meadows and potentially altering plant-soil carbon (C) and nitrogen (N). This ...study focuses on the plateau pika (
) to examine the responses of plant-soil C and N to a small burrowing mammal from quadrat scale to plot scale. The density of active burrow entrances in disturbed plots was used as an indicator of the disturbance intensity of plateau pikas. The study found that the below-ground biomass (BGB) and its C and N, as well as soil C and N concentrations were significantly lower in bare soil areas than in vegetated areas and undisturbed plots. This shows that the quadrat scale limited the estimation of the C and N sequestration potential. Therefore, further research on the plot scale found that the disturbance by plateau pika significantly reduced plant biomass and BGB carbon stock. However, plateau pika did not affect soil C and N stocks or ecosystem C and N stocks. These findings suggest the bare soil patches formed by plateau pika caused plant and soil heterogeneity but had a trade-off effect on plant-soil C and N stocks at the plot scale. Nevertheless, moderate disturbance intensity increased the C and N sequestration potential in grassland ecosystems. These results provide a possible way to estimate how disturbance by small burrowing mammals affects C and N cycling in grassland ecosystems while accurately assessing the effects of small burrowing mammal densities on C and N in grassland ecosystems.
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