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 Increased microbial sequestration of soil organic carbon under nitrogen deposition over China’s terrestrial ecosystems

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Shu Liao ◽  
Siyi Tan ◽  
Yan Peng ◽  
Dingyi Wang ◽  
Xiangyin Ni ◽  
...  
Keyword(s):  
Meta Analysis ◽  
Terrestrial Ecosystems ◽  
N Deposition ◽  
N Addition ◽  
Soil Organic C ◽  
Organic C ◽  
Soil Microbial ◽  
Biomass Turnover ◽  
Microbial Residues ◽  
Stimulation Of

Abstract Background China’s terrestrial ecosystems have been receiving increasing amounts of reactive nitrogen (N) over recent decades. External N inputs profoundly change microbially mediated soil carbon (C) dynamics, but how elevated N affects the soil organic C that is derived from microbial residues is not fully understood. Here, we evaluated the changes in soil microbial necromass C under N addition at 11 forest, grassland, and cropland sites over China’s terrestrial ecosystems through a meta-analysis based on available data from published articles. Results Microbial necromass C accounted for an average of 49.5% of the total soil organic C across the studied sites, with higher values observed in croplands (53.0%) and lower values in forests (38.6%). Microbial necromass C was significantly increased by 9.5% after N addition, regardless of N forms, with greater stimulation observed for fungal (+ 11.2%) than bacterial (+ 4.5%) necromass C. This increase in microbial necromass C under elevated N was greater under longer experimental periods but showed little variation among different N application rates. The stimulation of soil microbial necromass C under elevated N was proportional to the change in soil organic C. Conclusions The stimulation of microbial residues after biomass turnover is an important pathway for the observed increase in soil organic C under N deposition across China’s terrestrial ecosystems.

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.

scholarly journals Interactive Effects of Nitrogen and Water Addition on Soil Microbial Metabolic Limitation in Temperate Desert Shrublands

2021 ◽  
Author(s):  
Jiwei Li ◽  
Jiangbo Xie ◽  
Yu Zhang ◽  
Dong Lingbo ◽  
Zhouping Shangguan ◽  
...  
Keyword(s):  
Interactive Effects ◽  
Desert Ecosystem ◽  
N Addition ◽  
Water Addition ◽  
Desert Ecosystems ◽  
Organic C ◽  
Soil Microbial ◽  
P Limitation ◽  
Microbial C ◽  
C Limitation

Abstract Aims Soil microbes play critical roles in regulating the turnover of soil organic carbon (SOC) and nutrients, and microbial metabolic limitation should draw more attention in desert ecosystems. However, soil extracellular enzymes activity (EEA) response and microbial metabolic limitation to atmospheric N deposition and increased precipitation in desert-shrubland are still poorly understood. Methods The study examined the effects of long-term (9 year) N and water additions (i.e., 5 g N m−2 yr−1, 30% ambient precipitation increase and their combination) on EEAs and soil microbial resource limitation, as well as explored their controlling factors in the Gurbantunggut Desert in northwestern China. Results The results showed that N and water additions significantly enhanced soil EEAs and considerably aggravated microbial phosphorous (P) limitation. Water addition and the N-water combination addition alleviated carbon (C) limitation, but N addition alone strengthened microbial C limitation. The interaction of N and water additions relieved the negative impact of N addition on soil microbial C limitation, and positively aggravated microbial P limitation. Soil microbial C limitation was primarily driven by soil moisture and organic C concentration, while the soil microbial N/P limitation was chiefly controlled by soil water and available P contents. Conclusions The influences of either N- or water addition alone on desert ecosystem biogeochemical processes may be altered by their concurrent occurrence. Overall, these findings highlight water availability is more effective at modifying microbial metabolisms than N accumulation in desert ecosystems. Altogether, this may help to predict how terrestrial C and nutrient flow could be induced by global change factors..

scholarly journals Responses of soil respiration to elevated carbon dioxide and nitrogen addition in young subtropical forest ecosystems in China

2010 ◽  
Vol 7 (1) ◽  
pp. 315-328 ◽  
Author(s):  
Q. Deng ◽  
G. Zhou ◽  
J. Liu ◽  
S. Liu ◽  
H. Duan ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Elevated Co2 ◽  
Forest Ecosystems ◽  
N Deposition ◽  
Subtropical Forest ◽  
N Addition ◽  
Above Ground Biomass ◽  
Respiration Rates ◽  
Ambient Co2 ◽  
Ambient N Deposition

Abstract. Global climate change in the real world always exhibits simultaneous changes in multiple factors. Prediction of ecosystem responses to multi-factor global changes in a future world strongly relies on our understanding of their interactions. However, it is still unclear how nitrogen (N) deposition and elevated atmospheric carbon dioxide concentration [CO2] would interactively influence forest floor soil respiration in subtropical China. We assessed the main and interactive effects of elevated [CO2] and N addition on soil respiration by growing tree seedlings in ten large open-top chambers under CO2 (ambient CO2 and 700 μmol mol−1) and nitrogen (ambient and 100 kg N ha−1 yr−1) treatments. Soil respiration, soil temperature and soil moisture were measured for 30 months, as well as above-ground biomass, root biomass and soil organic matter (SOM). Results showed that soil respiration displayed strong seasonal patterns with higher values observed in the wet season (April–September) and lower values in the dry season (October–March) in all treatments. Significant exponential relationships between soil respiration rates and soil temperatures, as well as significant linear relationships between soil respiration rates and soil moistures (below 15%) were found. Both CO2 and N treatments significantly affected soil respiration, and there was significant interaction between elevated [CO2] and N addition (p<0.001, p=0.003, and p=0.006, respectively). We also observed that the stimulatory effect of individual elevated [CO2] (about 29% increased) was maintained throughout the experimental period. The positive effect of N addition was found only in 2006 (8.17% increased), and then had been weakened over time. Their combined effect on soil respiration (about 50% increased) was greater than the impact of either one alone. Mean value of annual soil respiration was 5.32 ± 0.08, 4.54 ± 0.10, 3.56 ± 0.03 and 3.53 ± 0.03 kg CO2 m−2 yr−1 in the chambers exposed to elevated [CO2] and high N deposition (CN), elevated [CO2] and ambient N deposition (CC), ambient [CO2] and high N deposition (NN), and ambient [CO2] and ambient N deposition (CK as a control), respectively. Greater above-ground biomass and root biomass was obtained in the CN, CC and NN treatments, and higher soil organic matter was observed only in the CN treatment. In conclusion, the combined effect of elevated [CO2] and N addition on soil respiration was apparent interaction. They should be evaluated in combination in subtropical forest ecosystems in China where the atmospheric CO2 and N deposition have been increasing simultaneously and remarkably.

Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long term field manipulation and modelling study 

2021 ◽  
Author(s):  
Christopher Taylor ◽  
Victoria Janes-Bassett ◽  
Gareth Phoenix ◽  
Ben Keane ◽  
Iain Hartley ◽  
...  
Keyword(s):  
N Deposition ◽  
Calcareous Grassland ◽  
Organic P ◽  
N Addition ◽  
Soil C ◽  
P Limitation ◽  
P Cycling ◽  
Nutrient Manipulation ◽  
N And P Cycling

&lt;p&gt;In ecosystems where nitrogen (N) limits plant productivity, N deposition can stimulate plant growth, and consequently, promote carbon (C) sequestration by increasing input of detrital C and other forms of plant C to the soil. However, other forms of nutrient limitation such as phosphorus (P) limitation and N-P co-limitation are widespread and may increase in prevalence with N deposition. Our understanding of how terrestrial ecosystem C, N and P cycling may be affected by N deposition when N is not the sole limiting resource is fairly limited. In this work, we investigate the consequences of enhanced N addition on C, N and P cycling in grasslands that exhibit contrasting forms of nutrient limitation.&lt;/p&gt;&lt;p&gt;We do so by collecting data from a long-term nutrient manipulation experiment on two N-P co-limited grasslands; an acidic grassland of stronger N-limitation and a calcareous grassland of stronger P limitation, and integrating this into a mechanistic C, N and P cycling model (N14CP). To simulate the experimental grasslands and explore the role of P access mechanisms in determining ecosystem state, we allowed P access to vary, and compared the outputs to plant-soil C, N and P data. Combinations of organic P access and inorganic P availability most closely representing data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation.&lt;/p&gt;&lt;p&gt;The modelled grasslands showed contrasting responses to simulated N deposition. In the acidic grassland, N addition greatly increased C stocks by stimulating biomass productivity, but the same N treatments reduced the organic C pool in the calcareous grassland. Nitrogen deposition exacerbated P limitation in the calcareous grassland by reducing the size of the bioavailable P pool to plants, reducing biomass input to the soil C pool. Plant acquisition of organic P played an important role in determining the nutrient conditions of the grasslands, as both simulated grasslands increased organic P uptake to meet enhanced P demand driven by N deposition. Greater access to organic P in the acidic grassland prevented a shift to P limitation under elevated levels of N deposition, but organic P access was too low in the calcareous grassland to prevent worsening P limitation.&lt;/p&gt;&lt;p&gt;We conclude that grasslands of differing limiting nutrients may respond to N deposition in contrasting ways, and stress that as N deposition shifts ecosystems toward P limitation, a globally important carbon sink risks degradation.&lt;/p&gt;

scholarly journals Phosphorus Reduces Negative Effects of Nitrogen Addition on Soil Microbial Communities and Functions

2020 ◽  
Vol 8 (11) ◽  
pp. 1828 ◽  
Author(s):  
Zongwei Xia ◽  
Jingyi Yang ◽  
Changpeng Sang ◽  
Xu Wang ◽  
Lifei Sun ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Bacterial Diversity ◽  
Soil Microbial Communities ◽  
N Deposition ◽  
N Fixation ◽  
N Addition ◽  
Soil Bacterial Diversity ◽  
Soil Microbial ◽  
Soil Bacterial ◽  
P Addition

Increased soil nitrogen (N) from atmospheric N deposition could change microbial communities and functions. However, the underlying mechanisms and whether soil phosphorus (P) status are responsible for these changes still have not been well explained. Here, we investigated the effects of N and P additions on soil bacterial and fungal communities and predicted their functional compositions in a temperate forest. We found that N addition significantly decreased soil bacterial diversity in the organic (O) horizon, but tended to increase bacterial diversity in the mineral (A) horizon soil. P addition alone did not significantly change soil bacterial diversity but mitigated the negative effect of N addition on bacterial diversity in the O horizon. Neither N addition nor P addition significantly influenced soil fungal diversity. Changes in soil microbial community composition under N and P additions were mainly due to the shifts in soil pH and NO3− contents. N addition can affect bacterial functional potentials, such as ureolysis, N fixation, respiration, decomposition of organic matter processes, and fungal guilds, such as pathogen, saprotroph, and mycorrhizal fungi, by which more C probably was lost in O horizon soil under increased N deposition. However, P addition can alleviate or switch the effects of increased N deposition on the microbial functional potentials in O horizon soil and may even be a benefit for more C sequestration in A horizon soil. Our results highlight the different responses of microorganisms to N and P additions between O and A horizons and provides an important insight for predicting the changes in forest C storage status under increasing N deposition in the future.

scholarly journals Different Molecular Characterization of Soil Particulate Fractions under N Deposition in a Subtropical Forest

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 914
Author(s):  
Jing Geng ◽  
Shulan Cheng ◽  
Huajun Fang ◽  
Jie Pei ◽  
Meng Xu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Structure ◽  
Critical Role ◽  
N Deposition ◽  
Subtropical Forest ◽  
Gas Chromatography Mass Spectrometry ◽  
N Addition ◽  
Pyrolysis Gas ◽  
C Cycle ◽  
N Treatment

Key Findings: Combining physical fractionation and pyrolysis–gas chromatography/mass spectrometry (py-GC/MS) technique can help better understand the dynamics of soil organic matter (SOM). Background and Objectives: SOM plays a critical role in the global carbon (C) cycle. However, its complexity remains a challenge in characterizing chemical molecular composition within SOM and under nitrogen (N) deposition. Materials and Methods: Three particulate organic matter (POM) fractions within SOM and under N treatments were studied from perspectives of distributions, C contents and chemical signatures in a subtropical forest. N addition experiment was conducted with two inorganic N forms (NH4Cl and NaNO3) applied at three rates of 0, 40, 120 kg N ha−1 yr−1. Three particle-size fractions (>250 μm, 53–250 μm and <53 μm) were separated by a wet-sieving method. Py-GC/MS technique was used to differentiate between chemical composition. Results: A progressive proportion transfer of mineral-associated organic matter (MAOM) to fine POM under N treatment was found. Only C content in fine POM was sensitive to N addition. Principal component analyses (PCA) showed that the coarse POM had the largest plant-derived markers (lignins, phenols, long-chain n-alkanes, and n-alkenes). Short-chain n-alkanes and n-alkenes, benzofurans, aromatics and polycyclic aromatic hydrocarbons mainly from black carbon prevailed in the fine POM. N compounds and polysaccharides from microbial products dominated in the MAOM. Factor analysis revealed that the degradation extent of three fractions was largely distinct. The difference in chemical structure among three particulate fractions within SOM was larger than treatments between control and N addition. In terms of N treatment impact, the MAOM fraction had fewer benzofurans compounds and was enriched in polysaccharides, indicating comparatively weaker mineralization and stronger stabilization of these substances. Conclusions: Our findings highlight the importance of chemical structure in SOM pools and help to understand the influence of N deposition on SOM transformation.

scholarly journals Soil Organic Carbon and Nitrogen Decomposition in Fecal Manure of Cattle Fed Browse/Maize Silages

2014 ◽  
Vol 3 (3) ◽  
pp. 50
Author(s):  
Habib Kato ◽  
Robert Mulebeke ◽  
Felix Budara Bareeba ◽  
Elly Nyambobo Sabiiti
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
The Other ◽  
Organic N ◽  
Calliandra Calothyrsus ◽  
Maize Silage ◽  
Protein Nitrogen ◽  
Microbial Decomposition ◽  
Organic C ◽  
Soil Microbial

<p>Soil organic carbon (C) and nitrogen (N) decomposition in fecal manure of cattle fed browses of Calliandra (<em>Calliandra calothyrsus</em>), Gliricidia (<em>Gliricidia sepium</em>) and Leucaena (<em>Leucaena leucocephala</em>) browse/maize silage mixtures and maize (<em>Zea mays</em>) silage alone when applied to the soil were investigated in a pot experiment in comparison to the corresponding silages fed. Maize silage alone had the lowest N and a larger C: N ratio, making it a poor quality compost when applied to the soil, but compared to the browse/maize silage mixtures it had the highest level of soluble N as non-protein nitrogen (NPN) which makes much of its N available for soil microbial decomposition of its organic C. Calliandra browse/maize silage mixture had the highest level of fiber-bound N (ADFN), which reduces N availability for soil microbial decomposition of its organic C in spite of its high N content and a narrower C: N ratio. Fecal manure from maize silage alone had a lower level of N and a wider C: N ratio than fecal manure from the other silages fed which would affect its decomposition in the soil, but it had the lowest level of ADFN and much of its N is made available for soil microbial decomposition of its organic C. Soil samples after 12 weeks of the experiment showed that Calliandra browse/maize silage mixture maintained the highest level of C in the soil, while maize silage alone maintained the lowest level. Also soils treated with fecal manure from the other browse/maize silage mixtures maintained higher levels of C than fecal manure from maize silage alone. Organic C levels were lowest at 8 weeks of the experiment for all treatments and rose to the original levels at 12 weeks which could have been as a result of biotic and hydrologic factors coupled with soil aggregation. Decomposition of organic N followed a similar trend as organic C. The two elements are linked in both plant inputs in the soil and in the eventual soil humic substances. The soils treated with browse/maize silage mixtures maintained C: N ratios that were similar to that of the control soil and higher than those of the fecal manure treatments. Thus, in spite of the added silage materials to the soil, rapid decomposition of organic C could not occur to reflect benefits of adding the silage materials to the soil. Thus, fecal manure, particularly from feeding animals on browse/forage diets is more beneficial in the soil as it would decompose more readily releasing the plant nutrients they contain.</p>

scholarly journals Soil Nitrogen and Sulfur Leaching in a Subtropical Forest at a Transition State under Decreasing Atmospheric Deposition

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1798
Author(s):  
Piaopiao Ke ◽  
Gaoyue Si ◽  
Yao Luo ◽  
Zhenglin Cheng ◽  
Qian Yu ◽  
...  
Keyword(s):  
Transition State ◽  
Soil Layer ◽  
N Deposition ◽  
Subtropical Forest ◽  
N Leaching ◽  
N Saturation ◽  
Subtropical Forests ◽  
Net Flux ◽  
Throughfall Deposition

Anthropogenic emissions of nitrogen- (N) and sulfur (S)-containing pollutants have declined across China in recent years. However, the responses of N and S depositions and dynamics in soil remain unclear in subtropical forests. In this study, the wet and throughfall depositions of dissolved inorganic N (DIN) and SO42− were continuously monitored in a mildly polluted subtropical forest in Southeast China in 2017 and 2018. Moreover, these solutes in soil water along the soil profile were monitored in 2018. Throughfall deposition of DIN and S decreased by 59% and 53% in recent 3 years, respectively, which can be majorly attributed to the decreases in wet depositions of NO3− and SO42−. Meanwhile, NH4+ deposition remained relatively stable at this site. Even though N deposition in 2018 was below the N saturation threshold for subtropical forests, significant N leaching still occurred. Excess export of N occurred in the upper soil layer (0–15 cm), reaching 6.86 ± 1.54 kg N/ha/yr, while the deeper soil (15–30 cm) was net sink of N as 8.29 ± 1.71 kg N/ha/yr. Similarly, S was excessively exported from the upper soil with net flux of 14.7 ± 3.15 kg S/ha/yr, while up to 6.37 ± 3.18 kg S/ha/yr of S was retained in the deeper soil. The significant N and S leaching under declined depositions suggested that this site possibly underwent a transition state, recovering from historically high acid deposition. Furthermore, the rainfall intensity remarkably regulated leaching and retention of SO42− and DIN at this site. The impacts of climate changes on N and S dynamics require further long-term monitoring in subtropical forests.

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