The Experts below are selected from a list of 2865 Experts worldwide ranked by ideXlab platform
Jingxue Zhao - One of the best experts on this subject based on the ideXlab platform.
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Precipitation alters temperature effects on ecosystem respiration in Tibetan Alpine Meadows
Agricultural and Forest Meteorology, 2018Co-Authors: Jingxue Zhao, Tianxiang Luo, Haixia Wei, Yanhong TangAbstract:Abstract There is scant evidence for the interactive effect of warming and precipitation change on ecosystem respiration (Re), particularly regarding for Alpine meadow ecosystems where there are high belowground biomass and soil organic carbon stocks. Such knowledge is crucial for predicting terrestrial carbon cycling under climate change. We transplanted meadow blocks reciprocally among three altitudes (4650 m, 4950 m and 5200 m) in the central Tibetan Plateau and examined the controls on Re in 1.5 and 2.5 years after the transplantation. Under the same degree of experimental warming by the downward transplantation, the Re increased and decreased significantly when the precipitation was higher and lower at destination sites than at the home sites, respectively. However, the experimental cooling by the upward transplantation consistently reduced the Re regardless of the precipitation change. Further analysis showed that the increase of Re under the experimental warming was closely related to the increase of aboveground biomass, whereas the reduction of Re under the cooling was highly correlated with the decrease of soil temperature. Moreover, the temperature sensitivity of the Re was decreased by the experimental warming but increased by the experimental cooling. These results suggest that effects of climate warming on the ecosystem respiration are highly associated with precipitation changes in the temperature-limited meadow ecosystems.
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environmental controls on soil respiration in Alpine meadow along a large altitudinal gradient on the central tibetan plateau
Catena, 2017Co-Authors: Jingxue Zhao, Lihua TianAbstract:Abstract Little is known about how environmental factors modify spatiotemporal variations of soil respiration (Rs) and its temperature sensitivity (Q10) in Alpine grasslands on the Tibetan Plateau (TP). We conducted an altitudinal experiment across lower and upper limits of Alpine Meadows on the central TP. Soil respiration and related environmental factors were observed at each of 7 altitudes (from 4400 m to 5200 m) during the growing seasons of 2012 and 2013. Soil temperature (ST) rather than soil moisture (SM) was the major abiotic factor controlling seasonal variation of Rs in Alpine grasslands across the seven altitudes. In addition to ST and SM, plant biomass is also an important factor controlling seasonal trends of Rs. The seasonal mean Rs increased with increasing altitude up to 4950 m, and then decreased above 4950 m. Below-ground biomass (BGB), ST and SM have direct effects on Rs, and the altitudinal trends of Rs can be well-predicated from these three variables (R2 = 0.65). The Q10 values of seasonal Rs generally increased with increasing altitude. Alpine Meadows generally have higher Q10 values comparing with steppe Meadows. Along the altitude gradient, Q10 was negatively correlated with ST, but positively correlated with SM, AGB, BGB and SOC. The results suggested that future climate warming would enhance Rs rates more dramatically in high-altitudes grasslands, and changes in vegetation structure under climate change might have a large impact on Rs in these Alpine grasslands.
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leaf unfolding of tibetan Alpine Meadows captures the arrival of monsoon rainfall
Scientific Reports, 2016Co-Authors: Tianxiang Luo, Xiaoyong Cui, Jingxue Zhao, Thomas Molg, Yanhong TangAbstract:The Alpine meadow on the Tibetan Plateau is the highest and largest pasture in the world, and its formation and distribution are mainly controlled by Indian summer monsoon effects. However, little is known about how monsoon-related cues may trigger spring phenology of the vast Alpine vegetation. Based on the 7-year observations with fenced and transplanted experiments across lower to upper limits of Kobresia Meadows in the central plateau (4400–5200 m), we found that leaf unfolding dates of dominant sedge and grass species synchronized with monsoon onset, regardless of air temperature. We also found similar patterns in a 22-year data set from the northeast plateau. In the monsoon-related cues for leaf unfolding, the arrival of monsoon rainfall is crucial, while seasonal air temperatures are already continuously above 0 °C. In contrast, the early-emerging cushion species generally leafed out earlier in warmer years regardless of precipitation. Our data provide evidence that leaf unfolding of dominant species in the Alpine Meadows senses the arrival of monsoon-season rainfall. These findings also provide a basis for interpreting the spatially variable greening responses to warming detected in the world’s highest pasture, and suggest a phenological strategy for avoiding damages of pre-monsoon drought and frost to Alpine plants.
Chao Zhang - One of the best experts on this subject based on the ideXlab platform.
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grazing exclusion reduces soil n2o emissions by regulating nirk and nosz type denitrifiers in Alpine Meadows
Journal of Soils and Sediments, 2021Co-Authors: Lu Zhang, Jie Wang, Xiangtao Wang, Guobin Liu, Chao Zhang, Qian Wan, Lirong LiaoAbstract:Knowledge of soil N cycling and the associated functional microbial groups of N2O production under different management measures could provide clues for the restoration of degraded Meadows in Alpine ecosystems. We investigated soil N2O emissions, the genes related to N2O production and reduction (AOA-amoA, AOB-amoA, nirK, nirS, and nosZ), and associated microbial communities in four Meadows (continuous grazing, grazing exclusion by fencing, grazing exclusion by combined fencing and reseeding, and undisturbed meadow) in the Tibetan Plateau to reveal the mechanism underlying potential N2O emissions in Alpine Meadows. Compared to the grazing meadow, fencing and fencing + reseeding Meadows had lower N2O emissions and lower abundances of AOA-amoA, AOB-amoA, nirK, nirS, and nosZ genes, suggesting that grazing exclusion could decrease the soil N-turnover potential. However, the higher N2O emissions compared to those of undisturbed Meadows indicated that longer restoration periods were necessary. Seeding the fenced meadow did not alter soil N2O emission or the abundance of AOA-amoA, AOB-amoA, nirK, nirS, and nosZ genes, possibly owing to the similar soil nutrient status compared to that of the fencing meadow. Grazing exclusion also resulted in significant changes in the community diversity and composition of microbes harboring these functional genes, especially nirK and nosZ communities. N2O emissions were significantly associated with microbial communities involved in N2O production and reduction but not with the gene abundance of AOA-amoA, AOB-amoA, nirK, nirS, and nosZ. Soil dissolved organic nutrients, including C and N, and soil moisture were the controlling factors for N2O production by altering the community composition of nirK- and nosZ-type denitrifiers, such as Bradyrhizobiaceae, Rhizobiaceae, Brucellaceae, Ochrobactrum, and Proteobacteria. Our results indicated that grazing-induced elevation of potential N2O emissions from meadow soil could be alleviated by grazing exclusion, including sole fencing and a combination of fencing and reseeding, by changing soil dissolved organic nutrients and moisture thus regulating the microbial communities.
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fencing as an effective approach for restoration of Alpine Meadows evidence from nutrient limitation of soil microbes
Geoderma, 2020Co-Authors: Jie Wang, Xiangtao Wang, Guobin Liu, Guoliang Wang, Chao ZhangAbstract:Abstract The effects of restoration on plant communities and soil nutrients have been extensively studied but knowledge of the metabolic requirements of microbial communities is limited, especially in fragile Alpine meadow ecosystems. Here, vegetation and soil from four Meadows (grazed meadow, fenced meadow, fenced + reseeded meadow, and undegraded meadow) on the Tibetan Plateau were investigated. The nutrient requirements of microbes represented by stoichiometry of extracellular enzyme activities related to soil C, N, and P acquisition (β-1,4-glucosidase, BG; β-1,4-N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP; and alkaline phosphatase, AP) and their possible environmental drivers were determined. Our results showed that enzymatic C:N:P acquisition in all the Meadows deviated from 1:1:1, suggesting that soil enzymatic activity stoichiometry in Tibetan Alpine Meadows is not homeostatic. Microbial communities in grazed Meadows were co-limited by soil N and P levels, and this limitation was closely associated with the stoichiometry of soil nutrients. Activities of BG, NAG + LAP, AP, and their stoichiometry (C:N, C:P, and N:P) in fenced Meadows were 38.2%, 32.9%, 51.2%, 16.8%, 19.5% and 2.3% higher than those in grazed Meadows. These results indicate that fencing can relieve the N and P limitations for microbial communities in Alpine Meadows. Seeding the fenced meadow did not increase the soil nutrient content, microbial biomass, or enzyme activity compared with the fenced meadow, possibly owing to the low competition of the seeded species for resources. Changes in extracellular enzyme activity and stoichiometry were better explained by dissolved organic C and microbial biomass N than by plant or other soil properties. Our results demonstrate the effectiveness of fencing on the restoration of degraded Alpine Meadows from the perspective of alleviating microbial nutrient limitations.
Jian Sun - One of the best experts on this subject based on the ideXlab platform.
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solar radiation regulates the leaf nitrogen and phosphorus stoichiometry across Alpine Meadows of the tibetan plateau
Agricultural and Forest Meteorology, 2019Co-Authors: Jian Sun, Biying Liu, Yong You, M Liu, Hua ShangAbstract:Abstract Leaf nitrogen (N) and phosphorus (P) stoichiometry covary with many aspects of climatic and edaphic factors, yet the effects of solar radiation (SR) on leaf stoichiometry are still unclear. In the Tibetan Plateau, the high level of SR can induce the plants to reach their light saturation point easily, which causes photoinhibition of photosynthesis. Here, the leaf N and P concentrations across the Alpine meadow of the Tibetan Plateau were measured to explore the response of leaf N and P stoichiometry to SR. Our results showed that the concentrations of both leaf N and leaf P were negatively correlated with SR under the high SR level (SR > 15,000 KJ m−2 d-1). The structural equation model demonstrated that SR plays a vital role in leaf N and P stoichiometry, and SR has direct effects on leaf N and P stoichiometry through a physiological process (path coefficient =-0.293 and -0.343, respectively). In addition, the high SR level lowered the level of precipitation (path coefficient =-0.615) and temperature (path coefficient =-0.047), then changed the soil organic carbon, soil nitrogen and phosphorus content. Furthermore, precipitation, temperature, soil organic carbon, soil nitrogen and phosphorus also regulated leaf N and P stoichiometry, which caused the SR to have indirect effects on leaf N and P stoichiometry (path coefficient =-0.072 and -0.053, respectively). As a consequence, we highlighted that SR regulates leaf N and P stoichiometry across Alpine Meadows of the Tibetan Plateau, and the results provide guidance on grassland management.
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soil nitrogen and carbon determine the trade off of the above and below ground biomass across Alpine grasslands tibetan plateau
Ecological Indicators, 2016Co-Authors: Jian Sun, Haiming WangAbstract:The objective of this study is to gain a deeper understanding of the trade-offs between the aboveground biomass (AGB) and belowground biomass (BGB) due to environmental factors in Alpine grasslands, including Alpine steppes and Alpine Meadows, on the Tibetan Plateau. We assessed transect surveys to determine the response threshold and critical determinant of trade-offs. Additionally, a non-significant relationship was observed between trade-offs and climate factors and soil properties when the data for the Alpine meadow and Alpine steppe were analyzed separately. However, the trade-off between AGB and BGB were increased with soil nitrogen and organic carbon gradients across the Alpine grassland. The results demonstrate the trade-off effects of AGB and BGB in Alpine grasslands, emphasizing the need for an understanding of how the trade-off is affected by drivers of critical environmental factors at the regional scale. Consequently, trade-offs are an ecological indicator and tool for ecological management and decision-making. (C) 2015 The Authors. Published by Elsevier Ltd.
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biomass partitioning and its relationship with the environmental factors at the Alpine steppe in northern tibet
PLOS ONE, 2013Co-Authors: Jiangtao Hong, Jian Sun, Xiaodan Wang, Jihui Fan, Yanjiang CaiAbstract:Alpine steppe is considered to be the largest grassland type on the Tibetan Plateau. This grassland contributes to the global carbon cycle and is sensitive to climate changes. The allocation of biomass in an ecosystem affects plant growth and the overall functioning of the ecosystem. However, the mechanism by which plant biomass is allocated on the Alpine steppe remains unclear. In this study, biomass allocation and its relationship to environmental factors on the Alpine grassland were studied by a meta-analysis of 32 field sites across the Alpine steppe of the northern Tibetan Plateau. We found that there is less above-ground biomass (MA) and below-ground biomass (MB) in the Alpine steppe than there is in Alpine Meadows and temperate grasslands. By contrast, the root-to-shoot ratio (R:S) in the Alpine steppe is higher than it is in Alpine Meadows and temperate grasslands. Although temperature maintained the biomass in the Alpine steppe, precipitation was found to considerably influence MA, MB, and R:S, as shown by ordination space partitioning. After standardized major axis (SMA) analysis, we found that allocation of biomass on the Alpine steppe is supported by the allometric biomass partitioning hypothesis rather than the isometric allocation hypothesis. Based on these results, we believe that MA and MB will decrease as a result of the increased aridity expected to occur in the future, which will reduce the landscape’s capacity for carbon storage.
Gaolin Wu - One of the best experts on this subject based on the ideXlab platform.
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long term fencing improved soil properties and soil organic carbon storage in an Alpine swamp meadow of western china
Plant and Soil, 2010Co-Authors: Jimin Chen, Gaolin Wu, Lei Zhang, Tianming HuAbstract:Overgrazing significantly affects Alpine Meadows in ways similar to grasslands in other areas. Fencing to exclude grazers is one of the main management practices used to protect Alpine Meadows. However, it is not known if fencing can improve soil properties and soil organic carbon storage by restraining grazing in Alpine Meadows. We studied the long-term (nine-year) effects of fencing on soil properties, soil organic carbon and nitrogen storage compared with continued grazing in an Alpine swamp meadow of the Qinghai–Tibetan Plateau, NW China. Our results showed that fencing significantly improved vegetation cover and aboveground biomass. There were significant effects of fencing on pH value, soil bulk density, and soil moisture. Long-term fencing favored the increase of soil total nitrogen, soil organic matter, soil organic carbon, soil microbial biomass carbon and soil carbon storage compared with grazed Meadows. Our study suggests that long-term fencing to prevent disturbance could greatly affect soil organic carbon and nitrogen storage with regard to grazed Meadows. Therefore, it is apparent from this study that fencing is an effective restoration approach of with regard to the soil’s storage ability for carbon and nitrogen in Alpine meadow of the Qinghai–Tibetan Plateau.
Guobin Liu - One of the best experts on this subject based on the ideXlab platform.
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grazing exclusion reduces soil n2o emissions by regulating nirk and nosz type denitrifiers in Alpine Meadows
Journal of Soils and Sediments, 2021Co-Authors: Lu Zhang, Jie Wang, Xiangtao Wang, Guobin Liu, Chao Zhang, Qian Wan, Lirong LiaoAbstract:Knowledge of soil N cycling and the associated functional microbial groups of N2O production under different management measures could provide clues for the restoration of degraded Meadows in Alpine ecosystems. We investigated soil N2O emissions, the genes related to N2O production and reduction (AOA-amoA, AOB-amoA, nirK, nirS, and nosZ), and associated microbial communities in four Meadows (continuous grazing, grazing exclusion by fencing, grazing exclusion by combined fencing and reseeding, and undisturbed meadow) in the Tibetan Plateau to reveal the mechanism underlying potential N2O emissions in Alpine Meadows. Compared to the grazing meadow, fencing and fencing + reseeding Meadows had lower N2O emissions and lower abundances of AOA-amoA, AOB-amoA, nirK, nirS, and nosZ genes, suggesting that grazing exclusion could decrease the soil N-turnover potential. However, the higher N2O emissions compared to those of undisturbed Meadows indicated that longer restoration periods were necessary. Seeding the fenced meadow did not alter soil N2O emission or the abundance of AOA-amoA, AOB-amoA, nirK, nirS, and nosZ genes, possibly owing to the similar soil nutrient status compared to that of the fencing meadow. Grazing exclusion also resulted in significant changes in the community diversity and composition of microbes harboring these functional genes, especially nirK and nosZ communities. N2O emissions were significantly associated with microbial communities involved in N2O production and reduction but not with the gene abundance of AOA-amoA, AOB-amoA, nirK, nirS, and nosZ. Soil dissolved organic nutrients, including C and N, and soil moisture were the controlling factors for N2O production by altering the community composition of nirK- and nosZ-type denitrifiers, such as Bradyrhizobiaceae, Rhizobiaceae, Brucellaceae, Ochrobactrum, and Proteobacteria. Our results indicated that grazing-induced elevation of potential N2O emissions from meadow soil could be alleviated by grazing exclusion, including sole fencing and a combination of fencing and reseeding, by changing soil dissolved organic nutrients and moisture thus regulating the microbial communities.
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fencing as an effective approach for restoration of Alpine Meadows evidence from nutrient limitation of soil microbes
Geoderma, 2020Co-Authors: Jie Wang, Xiangtao Wang, Guobin Liu, Guoliang Wang, Chao ZhangAbstract:Abstract The effects of restoration on plant communities and soil nutrients have been extensively studied but knowledge of the metabolic requirements of microbial communities is limited, especially in fragile Alpine meadow ecosystems. Here, vegetation and soil from four Meadows (grazed meadow, fenced meadow, fenced + reseeded meadow, and undegraded meadow) on the Tibetan Plateau were investigated. The nutrient requirements of microbes represented by stoichiometry of extracellular enzyme activities related to soil C, N, and P acquisition (β-1,4-glucosidase, BG; β-1,4-N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP; and alkaline phosphatase, AP) and their possible environmental drivers were determined. Our results showed that enzymatic C:N:P acquisition in all the Meadows deviated from 1:1:1, suggesting that soil enzymatic activity stoichiometry in Tibetan Alpine Meadows is not homeostatic. Microbial communities in grazed Meadows were co-limited by soil N and P levels, and this limitation was closely associated with the stoichiometry of soil nutrients. Activities of BG, NAG + LAP, AP, and their stoichiometry (C:N, C:P, and N:P) in fenced Meadows were 38.2%, 32.9%, 51.2%, 16.8%, 19.5% and 2.3% higher than those in grazed Meadows. These results indicate that fencing can relieve the N and P limitations for microbial communities in Alpine Meadows. Seeding the fenced meadow did not increase the soil nutrient content, microbial biomass, or enzyme activity compared with the fenced meadow, possibly owing to the low competition of the seeded species for resources. Changes in extracellular enzyme activity and stoichiometry were better explained by dissolved organic C and microbial biomass N than by plant or other soil properties. Our results demonstrate the effectiveness of fencing on the restoration of degraded Alpine Meadows from the perspective of alleviating microbial nutrient limitations.