scholarly journals Altered precipitation regimes mitigate N2O flux response to nitrogen addition in an alpine steppe

2021 ◽  
Author(s):  
Yang Yang ◽  
Yuanming Xiao ◽  
Li Changbin ◽  
Bo Wang ◽  
Gao yongheng ◽  
...  
Keyword(s):  
Global Change ◽  
N Deposition ◽  
N2o Emissions ◽  
Ammonia Oxidizing Bacteria ◽  
N Addition ◽  
Precipitation Patterns ◽  
Alpine Steppe ◽  
Altered Precipitation ◽  
Precipitation Regimes ◽  
Precipitation Changes

Anthropogenic-driven global change, including changes in atmospheric nitrogen (N) deposition and precipitation patterns, is dramatically altering N cycling in soil. How long-term N deposition, precipitation changes, and their interaction influence nitrous oxide (N2O) emissions remains unknown, especially in the alpine steppes of the Qinghai-Tibetan Plateau (QTP). To fill this knowledge gap, a platform of N addition and altered precipitation experiments was established in an alpine steppe of the QTP in 2013. N addition significantly increased N2O emissions, and alterations in soil NO3-N, pH, temperature, and belowground biomass modulated N2O emissions. In addition to abiotic parameters, ammonia-oxidizing bacteria dominated N2O emissions in nitrification compared with ammonia-oxidizing archaea. Changes in the denitrifying microbial community, namely a high ratio of (nirS+nirK) gene-containing to nosZ gene-containing organisms, were responsible for N2O emissions in denitrification. Altered precipitation did not affect N2O emissions. This unexpected finding, which is inconsistent with the conventional view that N2O emissions are controlled by soil water content, indicates that N2O emissions are particularly susceptible to N deposition in the alpine steppes. Notably, whereas N2O emissions were affected by N addition as a single factor, they were not significantly affected by the combination of precipitation changes and N addition, indicating that altered precipitation patterns may mitigate the positive feedback effect of N addition on N2O emissions. Consequently, our study suggests that the response of N2O emissions to N deposition in future global change scenarios will be affected by precipitation regimes in the alpine steppes.

scholarly journals Testing mechanisms of N-enrichment-induced species loss in a semiarid Inner Mongolia grassland: critical thresholds and implications for long-term ecosystem responses

2012 ◽  
Vol 367 (1606) ◽  
pp. 3125-3134 ◽  
Author(s):  
Zhichun Lan ◽  
Yongfei Bai
Keyword(s):  
Ecosystem Services ◽  
Rare Species ◽  
Inner Mongolia ◽  
Global Environmental Change ◽  
N Deposition ◽  
Critical Threshold ◽  
Species Loss ◽  
N Addition ◽  
Precipitation Regimes ◽  
N Enrichment

The increase in nutrient availability as a consequence of elevated nitrogen (N) deposition is an important component of global environmental change. This is likely to substantially affect the functioning and provisioning of ecosystem services by drylands, where water and N are often limited. We tested mechanisms of chronic N-enrichment-induced plant species loss in a 10-year field experiment with six levels of N addition rate. Our findings on a semi-arid grassland in Inner Mongolia demonstrated that: (i) species richness (SR) declined by 16 per cent even at low levels of additional N (1.75 g N m –2 yr −1 ), and 50–70% species were excluded from plots which received high N input (10.5–28 g N m −2 yr −1 ); (ii) the responses of SR and above-ground biomass (AGB) to N were greater in wet years than dry years; (iii) N addition increased the inter-annual variations in AGB, reduced the drought resistance of production and hence diminished ecosystem stability; (iv) the critical threshold for chronic N-enrichment-induced reduction in SR differed between common and rare species, and increased over the time of the experiment owing to the loss of the more sensitive species. These results clearly indicate that both abundance and functional trait-based mechanisms operate simultaneously on N-induced species loss. The low initial abundance and low above-ground competitive ability may be attributable to the loss of rare species. However, shift from below-ground competition to above-ground competition and recruitment limitation are likely to be the key mechanisms for the loss of abundant species, with soil acidification being less important. Our results have important implications for understanding the impacts of N deposition and global climatic change (e.g. change in precipitation regimes) on biodiversity and ecosystem services of the Inner Mongolian grassland and beyond.

scholarly journals Impacts of Nitrogen Addition on Nitrous Oxide Emission: Model-Data Comparison

2018 ◽  
Author(s):  
Yujin Zhang ◽  
Minna Ma ◽  
Huajun Fang ◽  
Dahe Qin ◽  
Shulan Cheng ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Global Climate ◽  
Pore Space ◽  
Terrestrial Ecosystem ◽  
N2o Emission ◽  
N Deposition ◽  
N2o Emissions ◽  
Emission Model ◽  
N Addition ◽  
N2o Production

Abstract. The contributions of long-lived nitrous oxide (N2O) to the global climate and environment have received increasing attention. Especially, atmospheric nitrogen (N) deposition has substantially increased in recent decades due to extensive use of fossil fuels in industry, which strongly stimulates the N2O emissions of the terrestrial ecosystem. Several models have been developed to simulate N2O emission, but there are still large differences in their N2O emission simulations and responses to atmospheric deposition over global or regional scales. Using observations from N addition experiments in a subtropical forest, this study compared six widely-used N2O models (i.e. DayCENT, DLEM, DNDC, DyN, NOE, and NGAS) to investigate their performances for reproducing N2O emission, and especially the impacts of two types of N additions (i.e. ammonium and nitrate: NH4+ and NO3−, respectively) and two levels (low and high) on N2O emission. In general, the six models reproduced the seasonal variations of N2O emission, but failed to reproduce relatively larger N2O emissions due to NH4+ compared to NO3− additions. Few models indicated larger N2O emission under high N addition levels for both NH4+ and NO3−. Moreover, there were substantial model differences for simulating the ratios of N2O emission from nitrification and denitrification processes due to disagreements in model structures and algorithms. This analysis highlights the need to improve representation of N2O production and diffusion, and the control of soil water-filled pore space on these processes in order to simulate the impacts of N deposition on N2O emission.

scholarly journals Responses of nitrous oxide emissions to nitrogen and phosphorus additions in two tropical plantations with N-fixing vs. non-N-fixing tree species

2014 ◽  
Vol 11 (18) ◽  
pp. 4941-4951 ◽  
Author(s):  
W. Zhang ◽  
X. Zhu ◽  
Y. Luo ◽  
R. Rafique ◽  
H. Chen ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Tree Species ◽  
N2o Emission ◽  
N Deposition ◽  
Tree Plantations ◽  
N2o Emissions ◽  
N Addition ◽  
Leguminous Tree ◽  
Tropical Plantations ◽  
P Addition

Abstract. Leguminous tree plantations at phosphorus (P) limited sites may result in excess nitrogen (N) and higher rates of nitrous oxide (N2O) emissions. However, the effects of N and P applications on soil N2O emissions from plantations with N-fixing vs. non-N-fixing tree species have rarely been studied in the field. We conducted an experimental manipulation of N and/or P additions in two plantations with Acacia auriculiformis (AA, N-fixing) and Eucalyptus urophylla (EU, non-N-fixing) in South China. The objective was to determine the effects of N or P addition alone, as well as NP application together on soil N2O emissions from these tropical plantations. We found that the average N2O emission from control was greater in the AA (2.3 ± 0.1 kg N2O–N ha−1 yr−1) than in EU plantation (1.9 ± 0.1 kg N2O–N ha−1 yr−1). For the AA plantation, N addition stimulated N2O emission from the soil while P addition did not. Applications of N with P together significantly decreased N2O emission compared to N addition alone, especially in the high-level treatments (decreased by 18%). In the EU plantation, N2O emissions significantly decreased in P-addition plots compared with the controls; however, N and NP additions did not. The different response of N2O emission to N or P addition was attributed to the higher initial soil N status in the AA than that of EU plantation, due to symbiotic N fixation in the former. Our result suggests that atmospheric N deposition potentially stimulates N2O emissions from leguminous tree plantations in the tropics, whereas P fertilization has the potential to mitigate N-deposition-induced N2O emissions from such plantations.

scholarly journals Responses of nitrous oxide emissions to nitrogen and phosphorus additions in two tropical plantations with N-fixing vs. non-N-fixing tree species

2014 ◽  
Vol 11 (1) ◽  
pp. 1413-1442 ◽  
Author(s):  
W. Zhang ◽  
X. Zhu ◽  
Y. Luo ◽  
R. Rafique ◽  
H. Chen ◽  
...  
Keyword(s):  
Tree Species ◽  
N2o Emission ◽  
N Deposition ◽  
Tree Plantations ◽  
N2o Emissions ◽  
N Addition ◽  
Leguminous Tree ◽  
Tropical Plantations ◽  
P Addition ◽  
The Eu

Abstract. Leguminous tree plantations at phosphorus (P) limited sites may result in higher rates of nitrous oxide (N2O) emissions, however, the effects of nitrogen (N) and P applications on soil N2O emissions from plantations with N-fixing vs. non-N-fixing tree species has rarely been studied in the field. We conducted an experimental manipulation of N and P additions in two tropical plantations with Acacia auriculiformis (AA) and Eucalyptus urophylla (EU) tree species in South China. The objective was to determine the effects of N- or P-addition alone, as well as NP application together on soil N2O emissions from tropical plantations with N-fixing vs. non-N-fixing tree species. We found that the average N2O emission from control was greater in AA (2.26 ± 0.06 kg N2O-N ha−1 yr−1) than in EU plantation (1.87 ± 0.05 kg N2O-N ha−1 yr−1). For the AA plantation, N-addition stimulated the N2O emission from soil while P-addition did not. Applications of N with P together significantly decreased N2O emission compared to N-addition alone, especially in high level treatment plots (decreased by 18%). In the EU plantation, N2O emissions significantly decreased in P-addition plots compared with the controls, however, N- and NP-additions did not. The differing response of N2O emissions to N- or P-addition was attributed to the higher initial soil N status in the AA than that of the EU plantation, due to symbiotic N fixation in the former. Our results suggest that atmospheric N deposition potentially stimulates N2O emissions from leguminous tree plantations in the tropics, whereas P fertilization has the potential to mitigate N deposition-induced N2O emissions from such plantations.

scholarly journals Responses of Ecosystem CO2Fluxes to Short-Term Experimental Warming and Nitrogen Enrichment in an Alpine Meadow, Northern Tibet Plateau

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Ning Zong ◽  
Peili Shi ◽  
Jing Jiang ◽  
Minghua Song ◽  
Dingpeng Xiong ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Global Change ◽  
Alpine Meadow ◽  
N Deposition ◽  
Plant Production ◽  
Tibet Plateau ◽  
N Availability ◽  
Soil N ◽  
N Addition ◽  
Alpine Ecosystems

Over the past decades, the Tibetan Plateau has experienced pronounced warming, yet the extent to which warming will affect alpine ecosystems depends on how warming interacts with other influential global change factors, such as nitrogen (N) deposition. A long-term warming and N manipulation experiment was established to investigate the interactive effects of warming and N deposition on alpine meadow. Open-top chambers were used to simulate warming. N addition, warming, N addition × warming, and a control were set up. In OTCs, daytime air and soil temperature were warmed by 2.0°C and 1.6°C above ambient conditions, but soil moisture was decreased by 4.95 m3 m−3. N addition enhanced ecosystem respiration (Reco); nevertheless, warming significantly decreased Reco. The decline of Reco resulting from warming was cancelled out by N addition in late growing season. Our results suggested that N addition enhanced Reco by increasing soil N availability and plant production, whereas warming decreased Reco through lowering soil moisture, soil N supply potential, and suppression of plant activity. Furthermore, season-specific responses of Reco indicated that warming and N deposition caused by future global change may have complicated influence on carbon cycles in alpine ecosystems.

Above-and below-ground trait linkages of dominant species shape responses of alpine steppe composition to precipitation changes in the Tibetan Plateau

2021 ◽  
Author(s):  
Zhi Zheng ◽  
Yue Zhang ◽  
Shihu Zhang ◽  
Qun Ma ◽  
Dajie Gong ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Community Composition ◽  
Plant Community ◽  
Dominant Species ◽  
The Tibetan Plateau ◽  
Plant Community Composition ◽  
Alpine Steppe ◽  
Precipitation Regimes ◽  
Below Ground ◽  
Precipitation Changes

Abstract Aims Human activities and global changes have led to alterations in global and regional precipitation regimes. Despite extensive studies on the effects of changes in precipitation regimes on plant community composition across different types of grassland world-wide, few studies have specifically focused on the effects of precipitation changes on high-altitude alpine steppe at community and plant species levels in the Tibetan Plateau. Methods We investigated the effects of growing-season precipitation changes (reduced precipitation by 50%; ambient precipitation; enhanced precipitation by 50%) for 6 years on plant community composition in an alpine steppe of Tibetan Plateau by linking above-ground to below-ground traits of dominant species. Important Findings We found that reduced precipitation shifted community composition from dominance by bunchgrass (primarily Stipa purpurea) to dominance by rhizomatous grass (primarily Leymus secalinus). Roots and leaf traits of L. secalinus and S. purpurea differed in their responses to reduced precipitation. Reduced precipitation enhanced root vertical length and carbon (C) allocation to deep soil layers, and decreased the leaf width in L. secalinus, but it did not change the traits in S. purpurea. Moreover, reduced precipitation significantly enhanced rhizome biomass, length, diameter and adventitious root at the rhizome nodes in L. secalinus. These changes in traits may render rhizomatous grass greater competitive during drought stress. Therefore, our findings highlight important roles of above-ground and below-ground traits of dominant species in plant community composition of alpine steppe under precipitation change.

Effects of nitrogen deposition on litter decomposition and nutrient release mediated by litter types and seasonal change in a temperate forest

2020 ◽  
Vol 100 (1) ◽  
pp. 11-25 ◽  
Author(s):  
Guoyong Yan ◽  
Xiongde Dong ◽  
Binbin Huang ◽  
Honglin Wang ◽  
Ziming Hong ◽  
...  
Keyword(s):  
Mass Loss ◽  
Litter Decomposition ◽  
Nutrient Release ◽  
N Deposition ◽  
Pinus Koraiensis ◽  
N Addition ◽  
Entire Study ◽  
Mixed Litter ◽  
Negative Effect ◽  
Four Levels

We conducted a field experiment with four levels of simulated nitrogen (N) deposition (0, 2.5, 5, and 7.5 g N m−2 yr−1, respectively) to investigate the response of litter decomposition of Pinus koraiensis (PK), Tilia amurensis (TA), and their mixture to N deposition during winter and growing seasons. Results showed that N addition significantly increased the mass loss of PK litter and significantly decreased the mass loss of TA litter throughout the 2 yr decomposition processes, which indicated that the different responses in the decomposition of different litters to N addition can be species specific, potentially attributed to different litter chemistry. The faster decomposition of PK litter with N addition occurred mainly in the winter, whereas the slower decomposition of TA litter with N addition occurred during the growing season. Moreover, N addition had a positive effect on the release of phosphorus, magnesium, and manganese for PK litter and had a negative effect on the release of carbon, iron, and lignin for TA litter. Decomposition and nutrient release from mixed litter with N addition showed a non-additive effect. The mass loss from litter in the first winter and over the entire study correlated positively with the initial concentration of cellulose, lignin, and certain nutrients in the litter, demonstrating the potential influence of different tissue chemistries.

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