scholarly journals Initial shifts in nitrogen impact on ecosystem carbon fluxes in an alpine meadow: patterns and causes

2017 ◽  
Vol 14 (17) ◽  
pp. 3947-3956 ◽  
Author(s):  
Bing Song ◽  
Jian Sun ◽  
Qingping Zhou ◽  
Ning Zong ◽  
Linghao Li ◽  
...  
Keyword(s):  
Alpine Meadow ◽  
Microbial Respiration ◽  
Ecosystem Respiration ◽  
C Sequestration ◽  
N Deposition ◽  
N Saturation ◽  
N Addition ◽  
Soil Microbial ◽  
Soil Microbial Respiration ◽  
Plant Respiration

Abstract. Increases in nitrogen (N) deposition can greatly stimulate ecosystem net carbon (C) sequestration through positive N-induced effects on plant productivity. However, how net ecosystem CO2 exchange (NEE) and its components respond to different N addition rates remains unclear. Using an N addition gradient experiment (six levels: 0, 2, 4, 8, 16, 32 gN m−2 yr−1) in an alpine meadow on the Qinghai–Tibetan Plateau, we explored the responses of different ecosystem C fluxes to an N addition gradient and revealed mechanisms underlying the dynamic responses. Results showed that NEE, ecosystem respiration (ER), and gross ecosystem production (GEP) all increased linearly with N addition rates in the first year of treatment but shifted to N saturation responses in the second year with the highest NEE (−7.77 ± 0.48 µmol m−2 s−1) occurring under an N addition rate of 8 gN m−2 yr−1. The saturation responses of NEE and GEP were caused by N-induced accumulation of standing litter, which limited light availability for plant growth under high N addition. The saturation response of ER was mainly due to an N-induced saturation response of aboveground plant respiration and decreasing soil microbial respiration along the N addition gradient, while decreases in soil microbial respiration under high N addition were caused by N-induced reductions in soil pH. We also found that various components of ER, including aboveground plant respiration, soil respiration, root respiration, and microbial respiration, responded differentially to the N addition gradient. These results reveal temporal dynamics of N impacts and the rapid shift in ecosystem C fluxes from N limitation to N saturation. Our findings bring evidence of short-term initial shifts in responses of ecosystem C fluxes to increases in N deposition, which should be considered when predicting long-term changes in ecosystem net C sequestration.

scholarly journals Initial shifts in nitrogen impact on ecosystem carbon fluxes in an alpine meadow: patterns and causes

2016 ◽  
Author(s):  
Bing Song ◽  
Jian Sun ◽  
Qingping Zhou ◽  
Ning Zong ◽  
Shuli Niu
Keyword(s):  
Alpine Meadow ◽  
Microbial Respiration ◽  
C Sequestration ◽  
N Deposition ◽  
N Saturation ◽  
N Addition ◽  
Soil Microbial ◽  
Soil Microbial Respiration ◽  
C Cycle ◽  
Plant Respiration

Abstract. The rising nitrogen (N) deposition could increase ecosystem net carbon (C) sequestration by stimulating plant productivity. However, how net ecosystem CO2 exchange (NEE) and its components respond dynamically to rising N deposition is far from clear. Using an N addition gradient experiment (six levels: 0, 2, 4, 8, 16, 32 gN m−2 year−1) in an alpine meadow on the Tibetan Plateau, we explored the responses of different ecosystem C fluxes to an increasing N loading gradient and revealed mechanisms underlying the dynamic responses. Results showed that NEE, ecosystem respiration (ER), and gross ecosystem production (GEP) all increased linearly with N addition rates in the first year of treatment, but shifted to N saturation responses in the second year with the highest NEE (−7.77 ± 0.48 µmol m−2 s−1) occurring under N addition rate of 8 gN m−2 year−1. The saturation responses of NEE and GEP were caused by N-induced accumulation of standing litter, which limited light availability for plant growth, under high N addition. The saturation response of ER was mainly due to decreases in aboveground plant respiration and soil microbial respiration under high N addition, while the N-induced reduction in soil pH caused declines in soil microbial respiration. We also found that various components of ER, including aboveground plant respiration, soil respiration, root respiration, and microbial respiration, responded differentially to the N addition gradient. The results reveal temporal dynamics of N impacts and the rapid shift of ecosystem C cycle from N limitation to N saturation. These findings are helpful for better understanding and model projection of future terrestrial C sequestration under rising N deposition.

Effects of nitrogen additions on soil microbial respiration and its temperature sensitivity in a Tibetan alpine meadow

2018 ◽  
Vol 38 (7) ◽  
Author(s):  
叶成龙 YE Chenglong ◽  
张浩 ZHANG Hao ◽  
周小龙 ZHOU Xiaolong ◽  
周显辉 ZHOU Xianhui ◽  
郭辉 GUO Hui ◽  
...  
Keyword(s):  
Temperature Sensitivity ◽  
Alpine Meadow ◽  
Microbial Respiration ◽  
Soil Microbial ◽  
Soil Microbial Respiration ◽  
Nitrogen Additions

Soil microbial respiration responses of nitrogen addition: Evidence from a long-time semi-arid grassland soil incubation

2020 ◽  
Author(s):  
Zhaomin Wang ◽  
Zhongmiao Liu ◽  
Binhui Guo ◽  
Zhengchao Qi ◽  
Decao Niu ◽  
...  
Keyword(s):  
Microbial Respiration ◽  
Global Climate ◽  
Nitrogen Concentration ◽  
Terrestrial Ecosystems ◽  
Carbon Pools ◽  
N Addition ◽  
North West ◽  
Soil Microbial ◽  
Soil Microbial Respiration ◽  
Semi Arid

<p>Nitrogen is essential for the synthesis of key cellular compounds such as proteins and nucleic acids in all organisms, and it is one of the limiting elements in most terrestrial ecosystems. During past decades, terrestrial ecosystems nutrients availability have altered with nitrogen deposition increases rapidly so that under the soil microbial metabolism activities terrestrial ecosystem biogeochemical cycles are strongly affected. Therefore, maintaining the stability of soil carbon pools, especially microbial carbon pools has great importance for studying global carbon cycle and global climate change processes. Depending on whether soil microbial has already adapted to the environment nitrogen concentration, there exists different results, such as promotion, inhibition, and no impact. To date, how nitrogen will affect soil microbial respiration still has controversy. To determine the effects, we performed a 59 weeks incubation with the soil which has already treated with Urea for 9 years. The soil has been treated with four N addition levels in a semi-arid grassland where located in North-west part of China. We measured CO<sub>2</sub> effluxion under different treatments within the same temperature. Our results showed that during the first 8 weeks, soil microbial had strong responses about N addition and N9.2 showed greatest influence with soil microbial respiration. With the time passing, in the time of 9-59 weeks, N0 had highest soil microbial respiration rate while N2.3 was the lowest, this illustrated N2.3 had highest N use efficient (NUE), in order to meet soil microbial stoichiometry, microbial growth became strong C-limitation under the N2.3 treatment. What’s more, comparing with other studies which we shared same study area, we also found that the time of nitrogen application also had strong effect on soil microbial respiration. These results highlight the importance of microbial respiration and may also help us to have a better understand about how N deposition controls terrestrial C flows.</p>

scholarly journals Topography modulates effects of nitrogen deposition on microbial resource limitation in a nitrogen-saturated subtropical forest

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hao Chen ◽  
Junjie Tang ◽  
Xibin Sun ◽  
Kayan Ma ◽  
Huaihai Chen ◽  
...  
Keyword(s):  
Resource Limitation ◽  
N Deposition ◽  
Subtropical Forest ◽  
N Saturation ◽  
N Addition ◽  
Microbial Decomposition ◽  
Organic C ◽  
Soil Microbial ◽  
N Limitation ◽  
P Limitation

Abstract Background Nitrogen (N) saturation theory proposes that an ecosystem might switch from N limitation to carbon (C), phosphorus (P), or other nutrient limitations if it receives continuous N input. Yet, after N limitation is removed, which nutrient is the most limited and whether topography modulates such change is rarely tested at a microbial level. Here, we conducted a two-year N addition experiment under two different topography positions (i.e. a slope and a valley) in a N-saturated subtropical forest. Soil enzyme activity was measured, and ecoenzymatic stoichiometry indexes were calculated as indicators of microbial resource limitation. Results In the valley, two-year N addition changed the activity of all studied enzymes to various degrees. As a result, microbial C limitation was aggravated in the valley, and consequently microbial decomposition of soil labile organic C increased, but microbial P limitation was alleviated due to the stoichiometry balance. On the slope, however, N addition did not significantly change the activity of the studied enzymes, and did not alter the status of microbial resource limitation. Conclusions These results indicate that C is a more limited element for microbial growth than P after removing N limitation, but we also highlight that topography can regulate the effect of N deposition on soil microbial resource limitation in subtropical forests. These findings provide useful supplements to the N saturation theory.

scholarly journals Nutrient Enrichment Mediates the Relationships of Soil Microbial Respiration with Climatic Factors in an Alpine Meadow

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Ning Zong ◽  
Jing Jiang ◽  
Peili Shi ◽  
Minghua Song ◽  
Zhenxi Shen ◽  
...  
Keyword(s):  
Nutrient Enrichment ◽  
Alpine Meadow ◽  
Microbial Respiration ◽  
Climatic Factors ◽  
Distribution Patterns ◽  
The Tibetan Plateau ◽  
Soil Microbial ◽  
Soil Microbial Respiration ◽  
Nutrient Additions ◽  
Ecosystem Carbon

Quantifying the effects of nutrient additions on soil microbial respiration (Rm) and its contribution to soil respiration (Rs) are of great importance for accurate assessment ecosystem carbon (C) flux. Nitrogen (N) addition either alone (coded as LN and HN) or in combination with phosphorus (P) (coded as LN + P and HN + P) were manipulated in a semiarid alpine meadow on the Tibetan Plateau since 2008. Either LN or HN did not affectRm, while LN + P enhancedRmduring peak growing periods, but HN + P did not affectRm. Nutrient addition also significantly affectedRm/Rs, and the correlations ofRm/Rswith climatic factors varied with years. Soil water content (Sw) was the main factor controlling the variations ofRm/Rs. During the years with large rainfall variations,Rm/Rswas negatively correlated with Sw, while, in years with even rainfall,Rm/Rswas positively correlated with Sw. Meanwhile, in N + P treatments the controlling effects of climatic factors onRm/Rswere more significant than those in CK. Our results indicate that the sensitivity of soil microbes to climatic factors is regulated by nutrient enrichment. The divergent effects of Sw onRm/Rssuggest that precipitation distribution patterns are key factors controlling soil microbial activities and ecosystem C fluxes in semiarid alpine meadow ecosystems.

scholarly journals Effect of Short-Term Low-Nitrogen Addition on Carbon, Nitrogen and Phosphorus of Vegetation-Soil in Alpine Meadow

2021 ◽  
Vol 18 (20) ◽  
pp. 10998
Author(s):  
Zhen’an Yang ◽  
Wei Zhan ◽  
Lin Jiang ◽  
Huai Chen
Keyword(s):  
Alpine Meadow ◽  
Nitrogen Addition ◽  
Ammonium Nitrogen ◽  
N Deposition ◽  
Total Carbon ◽  
N Addition ◽  
Short Term ◽  
Nitrogen And Phosphorus ◽  
Soil Rhizosphere ◽  
And Function

As one of the nitrogen (N) limitation ecosystems, alpine meadows have significant effects on their structure and function. However, research on the response and linkage of vegetation-soil to short-term low-level N deposition with rhizosphere processes is scant. We conducted a four level N addition (0, 20, 40, and 80 kg N ha−1 y−1) field experiment in an alpine meadow on the Qinghai-Tibetan Plateau (QTP) from July 2014 to August 2016. We analyzed the community characteristics, vegetation (shoots and roots), total carbon (TC), nutrients, soil (rhizosphere and bulk) properties, and the linkage between vegetation and soil under different N addition rates. Our results showed that (i) N addition significantly increased and decreased the concentration of soil nitrate nitrogen (NO3−-N) and ammonium nitrogen, and the soil pH, respectively; (ii) there were significant correlations between soil (rhizosphere and bulk) NO3−-N and total nitrogen (TN), and root TN, and there was no strong correlation between plant and soil TC, TN and total phosphorus, and their stoichiometry under different N addition rates. The results suggest that short-term low-N addition affected the plant community, vegetation, and soil TC, TN, TP, and their stoichiometry insignificantly, and that the correlation between plant and soil TC, TN, and TP, and their stoichiometry were insignificant.

Sign in / Sign up

Export Citation Format

Share Document