Budgets of fixed nitrogen in the Orinoco Savannah Region: Role of pyrodenitrification

Sanhueza, Eugenio; Crutzen, Paul J.

doi:10.1029/98gb02314

Cited by 23 publications

(22 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The transferring rate of N from the agricultural soils of Asia to aquatic systems was estimated in this study with Asian-specific leaching and runoff factors. For N introduced into upland agricultural soils, runoff and leaching factors were observed as 11.8% (34) and 2.4% (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37), respectively. In addition, Asiaspecific data indicate that Nr losses from rice paddies by leaching and runoff occur at a rate of 26.9 kg N ha -1 yr -1 , ranging from 9.2 to 46.0 kg N ha -1 yr -1 (18,34,38).…”

Section: Anthropogenic Nr and Its Fatesmentioning

confidence: 97%

“…We set a factor of 7.08%, which was determined in Asian upland fields (39), for N 2 emission from N introduced into aerobic systems with anaerobic microsites, including upland soils and other manure management systems. The factor of N 2 emission by biomass burning was observed as 46.7% (30). We used this factor to estimate N 2 emission from N containing in burned crop residues and manure.…”

Section: Anthropogenic Nr and Its Fatesmentioning

confidence: 99%

See 1 more Smart Citation

The Asian Nitrogen Cycle Case Study

Zheng¹,

Fu²,

Xu³

et al. 2002

AMBIO: A Journal of the Human Environment

162

View full text Add to dashboard Cite

We analyzed nitrogen budgets at national and regional levels on a timeline from 1961-2030 using a model, IAP-N 1.0. The model was designed based upon the Inter-governmental Panel on Climate Change (IPCC) methods using Asia-specific parameters and a Food and Agriculture Organization of the United Nations (FAO) database. In this paper we discuss new reactive-nitrogen and its various fates, and environmental nitrogen enrichment and its driving forces. The anthropogenic reactive nitrogen of Asia dramatically increased from approximately 14.4 Tg N yr-1 in 1961 to approximately 67.7 Tg N yr-1 in 2000 and is likely to be 105.3 Tg N yr-1 by 2030. Most of the anthropogenic reactive-nitrogen has accumulated in the environment. We found that an increasing demand for food and energy supplies and the lack of effective measures to improve the efficiency of fertilizer nitrogen use, as well as effective measures for the prevention of NOx emissions from fossil-fuel combustion, are the principal drivers behind the environmental nitrogen-enrichment problem. This problem may be finally solved by substituting synthetic nitrogen fertilizers with new high-efficiency nitrogen sources, but solutions are dependent on advances in biological technology.

show abstract

Section: Anthropogenic Nr and Its Fatesmentioning

confidence: 97%

Section: Anthropogenic Nr and Its Fatesmentioning

confidence: 99%

The Asian Nitrogen Cycle Case Study

Zheng¹,

Fu²,

Xu³

et al. 2002

AMBIO: A Journal of the Human Environment

162

View full text Add to dashboard Cite

show abstract

“…However, the preliminary balance was strongly negative without including inputs through BNF. A more recent attempt to balance the N budget for the Orinoco savannas was published by Sanhueza and Crutzen (1998). In their budget (summarized in Table 1), the most uncertain numbers are those of N input via biological fixation, particularly in nodulated legumes.…”

Section: Nitrogen Fixationmentioning

confidence: 99%

Nitrogen cycling in tropical and temperate savannas

et al. 2006

View full text Add to dashboard Cite

Savannas are the most common vegetation type in the tropics and subtropics, ranging in physiognomy from grasslands with scattered woody plants to woodlands with heterogeneous grass cover. Productivity and organic matter turnover in savannas are controlled by interactions between water and nutrient availability, and this basic environmental structure is modified by fire frequency and land management practices. We compared temperate and tropical savannas in order to understand the strength of nitrogen (N) limitation of productivity. American tropical and temperate savannas are N limited systems, and the N cycle differs according to the woody plant density, fire frequency, land use change, N deposition and N fixation. Grazing and conversion to pasture have been the predominant land-use changes in most savannas. In the Cerrado and the Llanos tropical savannas, intensified use of fire for pasture management is leading to decreased woody plant density. Oppositely, in the Chaco and North American temperate savannas, fire suppression and grazing are leading to increases in woody density. In addition, the higher soil P availability in the Gran Chaco and the higher N deposition in North American savannas may be contributing to increases of N cycling and net productivity rates. Some aspects of the N budget for savannas of the American continent are still unclear and require further analysis to determine rates of N fixation, and to understand how spatial and temporal soil heterogeneity control N fluxes through soil solution and into streams.

show abstract

“…obs.). Assuming that our model species are representative of other savanna grasses and legumes, herbaceous legumes are unlikely to be an important N source in these ecosystems, as has sometimes been assumed (Bate 1981, Zietsman et al 1988, Medina & Bilbao 1991, Sanhueza & Crutzen 1998, Laclau et al 2005. For our study area we estimated a N-input from herbaceous legumes of o 0.36 kg N/ ha/yr (Table 4), and Reuss and Innis (1977) and Woodmansee (1978) estimated a value of o 2 kg N/ha/yr for American C 4 grasslands.…”

Section: Discussionmentioning

confidence: 97%

Why is Abundance of Herbaceous Legumes Low in African Savanna? A Test with Two Model Species

2010

View full text Add to dashboard Cite

Although fire is frequent in African savanna ecosystems and may cause considerable loss of nitrogen (N), N 2 -fixing herbaceous legumes-which could be expected to benefit from low N conditions-are usually not abundant. To investigate possible reasons for this scarcity, we conducted a pot experiment using two common plants of humid African savannas as model species, the legume Cassia mimosoides and the C 4 grass Hyperthelia dissoluta. These species were grown at different levels of water, N and phosphorus (P), both in monoculture and in competition with each other. In the monocultures, yields were significantly increased by the combined addition of N and P in pots receiving high water supply. In pots with interspecific competition, the legume grew poorly unless P was added. Foliar d 15 N values of legume plants grown in mixtures were considerably lower than those in monocultures, suggesting that rates of symbiotic N-fixation were higher in the presence of the grass. Grass d 15 N values, however, were also lower in mixtures, while N concentrations were higher, indicating a rapid transfer of N from the legume to the grass. We conclude that the main reason for the low abundance of C. mimosoides is not low P availability as such, but a greater ability of H. dissoluta to compete for soil N and P, and a much higher N-use efficiency. If other C 4 grasses have a similar competitive advantage, it could explain why herbaceous legumes are generally sparse in African savannas. We encourage others to test these findings using species from other types of savanna vegetation.

show abstract

Budgets of fixed nitrogen in the Orinoco Savannah Region: Role of pyrodenitrification

Cited by 23 publications

References 65 publications

The Asian Nitrogen Cycle Case Study

The Asian Nitrogen Cycle Case Study

Nitrogen cycling in tropical and temperate savannas

Why is Abundance of Herbaceous Legumes Low in African Savanna? A Test with Two Model Species

Contact Info

Product

Resources

About