Effects of Long-Term Warming on Microbial Nutrient Limitation of Soil Aggregates on the Qinghai-Tibet Plateau

Abstract Background and aims Global warming has increasingly serious impacts on the structure and function of the Tibetan Plateau ecosystem. However, the mechanism by which warming affects the biogeochemical processes and consequently the microbial nutrient limitation in soil aggregates is not clear. Methods In the present study, we used open-top chamber experiments to simulate warming in an alpine meadow and an alpine shrubland on the Qinghai-Tibet Plateau to understand how warming affects nutrient utilization and microorganism-limiting mechanisms in soil aggregates. Results The results showed that long-term warming treatment had contrasting effects on soil organic carbon (SOC) content of the alpine meadow and that of the shrubland. This difference was more pronounced with the increase in soil aggregate size, and the SOC content in microaggregates (MIGA) was significantly higher than that in large macroaggregates (LMGA). Soil enzyme activity increased with the decrease in aggregate size and was not significantly affected by warming treatment. Enzyme stoichiometry demonstrated that microbial P limitation is widespread on the Tibetan Plateau, and the long-term warming treatment exacerbated it, which has significant differences in shrubland. At the same time, the long-term warming treatment had no significant effect on C limitation in the alpine shrubland and the alpine meadow, but soil aggregate size affected the C limitation patterns of microorganisms and showed strong limitations in MIGA. Conclusions The microbial P limitation in shrubland is more sensitive to warming than that of grassland. Soil aggregates mediate the acquisition of carbon by microorganisms, and the carbon limitation in MIGA is the greatest. By providing a new perspective on this topic, our study increased our understanding of the effects of warming on microbial nutrient utilization and restriction patterns in soil aggregates.

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Effects of long-term warming on microbial nutrient limitation of soil aggregates on the Qinghai-Tibet Plateau

10.21203/rs.3.rs-604652/v2 ◽

2021 ◽

Author(s):

Wenjing Chen ◽

Huakun Zhou ◽

Leilei Qiao ◽

Yuanze Li ◽

Yang Wu ◽

...

Keyword(s):

Soil Aggregates ◽

Aggregate Size ◽

Soil Aggregate ◽

Tibet Plateau ◽

Alpine Meadows ◽

P Limitation ◽

Microbial Nutrient Limitation ◽

Qinghai Tibet Plateau ◽

C Limitation

Abstract Background and aims Global warming has increasingly serious impacts on the structure and function of the Tibetan Plateau ecosystem. However, the mechanism by which warming affects the biogeochemical processes, and consequently the microbial nutrient limitation in soil aggregates, is not clear. Methods In the present study, we used open-top chamber experiments to simulate warming in an alpine meadow and an alpine shrubland on the Qinghai-Tibet Plateau, and we measured the C, N, and P-acquiring enzyme (β-1, 4-glucosidase, BG; leucine aminopeptidase, LAP; β-N-acetylglucosaminidase, NAG; alkali phosphatase, AP) activities and their stoichiometry to understand how warming affects microorganism-limiting mechanisms in soil aggregates. Results The results showed that long-term warming treatment significantly decreased soil organic carbon (SOC) and total nitrogen (TN) concentrations of large macroaggregates (LMGA) and small macroaggregates (SMGA) in alpine meadows, but significantly increased SOC concentration of LMGA in alpine shrubland. The SOC and TN concentrations of alpine meadows increased with the decrease of soil aggregate size and the concentrations in microaggregate (MIGA) were significantly higher than those LMGA. Soil enzyme activity increased with the decrease in aggregate size and was not significantly affected by warming treatment. Enzyme stoichiometry results demonstrated that soil microbes in alpine meadows and shrubland were limited by nutrient P relative to nitrogen; moreover, the long-term warming treatment aggravated the P limitation of soil microorganisms in the shrubland, and it had significant differences in LMGA and MIGA. At the same time, the long-term warming treatment had no significant effect on C limitation in the alpine shrubland and alpine meadows, but soil aggregate size affected the C limitation patterns of microorganisms and showed the greatest limitations in MIGA. Conclusions The microbial P limitation in shrubland is more sensitive to warming than that in meadow. Soil aggregates mediate the acquisition of C by microorganisms, and the C limitation in MIGA is the greatest. By providing a new perspective on this topic, our study increased our understanding of the effects of warming on microbial nutrient utilization and restriction patterns in soil aggregates.

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Soil aggregate size influences the impact of inorganic nitrogen deposition on soil nitrification in an alpine meadow of the Qinghai–Tibet Plateau

PeerJ ◽

10.7717/peerj.8230 ◽

2020 ◽

Vol 8 ◽

pp. e8230 ◽

Cited By ~ 1

Author(s):

Jingjing Li ◽

Chao Yang ◽

Xiaoli Liu ◽

Hanzhong Ji ◽

Xinqing Shao

Keyword(s):

Alpine Meadow ◽

Inorganic Nitrogen ◽

Soil Aggregates ◽

Aggregate Size ◽

Bulk Soil ◽

Tibet Plateau ◽

Nitrification Rate ◽

Soil N ◽

Soil Nitrification ◽

Qinghai Tibet Plateau

Background Ammonium (NH4+) and nitrate (NO3−) are two inorganic forms of nitrogen (N) that are deposited from the atmosphere into soil systems. As the substrate and product of soil nitrification, these two forms of inorganic nitrogen will affect or be affected by the soil net nitrification rate (Nr). Our knowledge regarding soil nitrification is mainly derived from studies with bulk soil. However, soil is composed of different aggregate fractions, which may have an important impact on Nr. Methods In 2017, we collected soil samples from an alpine meadow of the Qinghai–Tibet Plateau and separated them into four soil aggregates (2–4, 1–2, 0.25–1, and <0.25 mm) using the dry sieving method. The four soil aggregate sizes amended with the 2 N deposition forms (NH4+-N and NO3−-N) were then incubated at 25 °C for 28 days, and the soil aggregates for each treatment were collected on day 0, 7, 14, 21, and 28 to determine the NO3−-N concentration. The soil Nr and contribution of soil aggregates to the nitrification rate in the bulk soil were calculated. Results There were differences in the physicochemical properties of the soil aggregates. The addition of N and aggregate size had strong effects on soil Nr, which were significantly increased under high levels of NH4+ addition across all soil aggregates. The Nr during the 4 week incubation period differed among aggregate sizes. Nr in the 2–4 mm aggregates was higher than in the other aggregates, which was correlated with the maximum values of the soil porosity observed in the 2–4 mm aggregates. Furthermore, almost half of the soil was composed of aggregates of <0.25 mm, indicating that the <0.25 mm aggregates made a higher contribution to the nitrification rate in the bulk soil than the other aggregates, even though these aggregates had a lower nitrification ability. Overall, our study revealed that the soil nitrification rate was influenced by both the N addition and soil aggregates, and that the 2–4 mm aggregates had a dominant effect on the response of soil N transformation processes to future nitrogen deposition in the alpine meadow.

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Effects of short-term and long-term warming on soil nutrients, microbial biomass and enzyme activities in an alpine meadow on the Qinghai-Tibet Plateau of China

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2014.05.014 ◽

2014 ◽

Vol 76 ◽

pp. 140-142 ◽

Cited By ~ 52

Author(s):

Xuexia Wang ◽

Shikui Dong ◽

Qingzhu Gao ◽

Huakun Zhou ◽

Shiliang Liu ◽

...

Keyword(s):

Microbial Biomass ◽

Soil Nutrients ◽

Enzyme Activities ◽

Alpine Meadow ◽

Tibet Plateau ◽

Short Term ◽

Qinghai Tibet Plateau

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Effects of long term fencing on biomass, coverage, density, biodiversity and nutritional values of vegetation community in an alpine meadow of the Qinghai-Tibet Plateau

Ecological Engineering ◽

10.1016/j.ecoleng.2019.01.016 ◽

2019 ◽

Vol 130 ◽

pp. 80-93 ◽

Cited By ~ 14

Author(s):

Xixi Yao ◽

Jianping Wu ◽

Xuyin Gong ◽

Xia Lang ◽

Cailian Wang ◽

...

Keyword(s):

Alpine Meadow ◽

Tibet Plateau ◽

Vegetation Community ◽

Nutritional Values ◽

Coverage Density ◽

Qinghai Tibet Plateau

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Cultivation effects on dispersible clay of soil aggregates

Canadian Journal of Soil Science ◽

10.4141/cjss95-013 ◽

1995 ◽

Vol 75 (1) ◽

pp. 101-107 ◽

Cited By ~ 18

Author(s):

L. G. Fuller ◽

Tee Boon Goh ◽

D. W. Oscarson

Keyword(s):

Soil Aggregates ◽

Aggregate Size ◽

Exchange Capacity ◽

Exchangeable Cations ◽

Organic C ◽

Size Fractions ◽

Clay Dispersion ◽

Native Prairie ◽

Exchangeable Ca

The objective of this study was to examine the effect of long-term cultivation on clay dispersibility of four aggregate size fractions (2.0–9.5 mm, 0.85–2.0 mm, 0.25–0.85 mm, and < 0.25 mm) obtained from a Chernozemic soil by comparing two cultivated sites with an adjacent native prairie site. Aggregate size fractions (ASF) were subjected to increasing levels of ultrasonic energy and the amount of clay dispersed at each energy level was determined. Organic carbon, hexose carbon, soluble hexose C, total clay, cation exchange capacity (CEC), and exchangeable cations were measured for each ASF. Clay contained within prairie aggregates was held much more strongly within the aggregate and therefore showed greater stability towards dispersion by ultrasonic vibration. More energy was required to disperse one-half of the ASF clay under prairie than under cultivated soils (228–425, and 95–229 kJ L−1 for prairie and cultivated macroaggregates, respectively; 370–433, and 249–334 kJ L−1 for prairie and cultivated microaggregates, respectively). Clay dispersibility was significantly correlated with organic C, hexose C, soluble hexose C, non-hexose C, CEC, and exchangeable Ca and Mg but was not correlated with total ASF clay. Long-term cultivation of this soil resulted in a decrease in the energy required to disperse an equivalent proportion of clay from aggregates relative to that of the grassland soil. Thus, cultivation of these soils has resulted in aggregates which are more susceptible to clay dispersion and therefore prone to water erosion and surface crusting. Key words: Clay dispersion, aggregation, carbohydrate

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Microbial nutrient limitation in arctic lakes in a permafrost landscape of southwest Greenland

Biogeosciences Discussions ◽

10.5194/bgd-12-11863-2015 ◽

2015 ◽

Vol 12 (14) ◽

pp. 11863-11890

Author(s):

B. Burpee ◽

J. E. Saros ◽

R. M. Northington ◽

K. S. Simon

Keyword(s):

Nutrient Limitation ◽

Enzyme Activities ◽

Arctic Lakes ◽

The Arctic ◽

Nutrient Concentrations ◽

Nutrient Inputs ◽

P Limitation ◽

Microbial P ◽

Microbial Nutrient Limitation ◽

Southwest Greenland

Abstract. Permafrost is degrading across regions of the Arctic, which can lead to increases in nutrient concentrations in surface freshwaters. The oligotrophic state of many arctic lakes suggests that enhanced nutrient inputs may have important effects on these systems, but little is known about microbial nutrient limitation patterns in these lakes. We investigated microbial extracellular enzyme activities (EEAs) to infer seasonal nutrient dynamics and limitation across 24 lakes in southwest Greenland during summer (June and July). From early to late summer, enzyme activities that indicate microbial carbon (C), nitrogen (N), and phosphorus (P) demand increased in both the epilimnia and hypolimnia by 74 % on average. Microbial investment in P acquisition was generally higher than that for N. Interactions among EEAs indicated that bacteria were primarily P limited. Dissolved organic matter (DOM, measured as dissolved organic carbon) was strongly and positively correlated with microbial P demand (R2 = 0.84 in July), while there were no relationships between DOM and microbial N demand. Microbial P limitation in June epilimnia (R2 = 0.67) and July hypolimnia (R2 = 0.57) increased with DOM concentration. The consistency of microbial P limitation from June to July was related to the amount of DOM present, with some low DOM lakes becoming N-limited in July. Our results suggest that future changes in P or DOM inputs to these lakes are likely to alter microbial nutrient limitation patterns.

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Long-term warming does not affect soil ecoenzyme activity and original microbial nutrient limitation on the Qinghai—Tibet Plateau

Soil Ecology Letters ◽

10.1007/s42832-021-0116-0 ◽

2021 ◽

Author(s):

Yuanze Li ◽

Huakun Zhou ◽

Wenjing Chen ◽

Yang Wu ◽

LeiLei Qiao ◽

...

Keyword(s):

Nutrient Limitation ◽

Tibet Plateau ◽

Microbial Nutrient Limitation ◽

Qinghai Tibet Plateau

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Nitrogen retention patterns and their controlling factors in an alpine meadow: implications for carbon sequestration

Biogeosciences Discussions ◽

10.5194/bgd-4-2641-2007 ◽

2007 ◽

Vol 4 (4) ◽

pp. 2641-2665 ◽

Cited By ~ 1

Author(s):

X. L. Xu ◽

H. Ouyang ◽

G. M. Cao

Keyword(s):

Alpine Meadow ◽

Nitrogen Retention ◽

Tibet Plateau ◽

Short Term ◽

Organic Carbon Concentration ◽

Long Term Retention ◽

Abiotic And Biotic Factors ◽

One Year ◽

Qinghai Tibet Plateau

Abstract. We hypothesized that the patterns of NO3− and NH4+ retention are different over short-term scales while they are similar over long-term scales in alpine meadows and that abiotic and biotic factors might be responsible for their different patterns over short-term scales. In order to test the hypotheses, a 15N-labeled experiment was conducted in an alpine meadow in the Qinghai-Tibet Plateau over four years. Our results showed that 15NO3− and 15NH4+ retention was distinctly different within two months, and even one year after tracer additions. The long-term retention of 15N at the whole-plot level did not differ significantly between 15NH4+ and 15NO3− treatments, and averaged 50% after four years. Higher soil temperature or soil organic carbon concentration enhanced 15NH4+ retention, but significantly reduced 15NO3− retention in the soil within two months following tracer additions. Soil moisture significantly affected 15N recovered in soil organic matter and microbial biomass as well as aboveground parts, but had no significant effects on 15N recovered in roots. These findings have important ecological implications with regard to the consequences of deposited nitrogen because of the possible difference in the fate of NH4+ vs. NO3− in alpine meadow ecosystems.

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