USGS Science⌕ Search
Home/Archive/USGS

USGS · 70179191

Simulated effects of nitrogen saturation the global carbon budget using the IBIS model

Xuehe Lu·Hong Jiang·Jinxun Liu·Xiuying Zhang·Jiaxin Jin·Qiuan Zhu·Zhen Zhang·Changhui Peng
View original source ↗Export metadata ↓

Abstract

Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr −1 , respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO 2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling.

Explore related subjects

Scientific ReportsArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Xuehe Lu, Hong Jiang, Jinxun Liu, Xiuying Zhang, Jiaxin Jin, Qiuan Zhu, Zhen Zhang, Changhui Peng. 2016-12-14. Simulated effects of nitrogen saturation the global carbon budget using the IBIS model. https://doi.org/10.1038/srep39173

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Spontaneous combustion of metal sulfide minerals and implications for seafloor massive sulfide mining

Metal sulfide minerals are abundant phases in many environments on earth, including seafloor massive sulfide (SMS) deposits, which occur at hydrothermal vents throughout the global ocean. These deep-sea settings are currently undergoing exploration for potential future mining. Here, we describe rocks from Escanaba Trough on the southern Gorda Ridge that underwent spontaneous combustion during laboratory processing. We compared the mineralogy, composition, and thermogravimetric behavior of the combusting samples to rocks from the same location that did not combust. We then used thermodynamic analyses to evaluate the exothermic nature of different metal sulfide oxidation reactions. The combusting rocks are primarily composed of nanocrystalline marcasite pseudomorphing blades of primary pyrrhotite. These altered, nanocrystalline rocks are less stable than their primary predecessors. Typically, recrystallization decreases reactivity as minerals trend towards steady state; however, both of the combusting samples we characterized are secondary, and demonstrate the instability of this metastable intermediate phase. Further, thermodynamic calculations indicate that metal sulfide oxidation is more exothermic when oxygen serves as the oxidant, as occurs in seawater or air. The distinct mineralogy, texture, and setting of SMS deposits in the modern oceans thus suggests a greater potential for self-heating in comparison to their ancient analogues.

Scientific Reports↗
USGS2026

Rewilding the upper Klamath River Basin: Rapid recolonization of Chinook salmon following the world’s largest dam removal

Habitat fragmentation is a global driver of decline in biodiversity, yet evaluations of ecological response following re-connection remain rare. In 2024, four hydroelectric dams on the Klamath River were removed, reconnecting over 640 km of anadromous habitat and marking the largest dam removal project completed to date. We used a stationary high-resolution multi-beam imaging SONAR to quantify adult Chinook salmon ( Oncorhynchus tshawytscha ) passage into newly reopened reaches during the first two migratory seasons following dam removal. An estimated 7,742 (95% CI: 7,702–7,778) Chinook salmon migrated upstream in 2024 and 13,310 (95% CI: 12,876–13,733) in 2025, representing 18–19% of fish returning to the Klamath River Basin. Within this period, Chinook salmon recolonized 88% of their documented historical distribution, expanding into 345 km of reconnected habitats and reaching elevations of up to 1,250 m. Recolonization required fish to swim through dam removal sites, complex hydraulic corridors and engineered fishways, demonstrating the propensity for rapid recolonization at basin scale despite these challenges. These findings provide the first quantitative assessment of salmon response to the world’s largest dam removal and demonstrate how reconnection can catalyze large-scale recolonization in historically fragmented river networks.

California, Oregon↗
USGS2026

Rapid intensification of Karenia brevis red tides after hurricane Milton revealed by PACE-OCI hyperspectral unmixing

Estuarine and coastal systems, shaped by transient physical–biological interactions and recurrent harmful algal blooms, often undergo episodic shifts in phytoplankton community composition (PCC). We present PhytoUnmix , a deep learning spectral unmixing framework applied to NASA’s hyperspectral PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) mission, to resolve PCC dynamics during a red tide bloom following Hurricane Milton (2024) on the West Florida Shelf, USA. PACE-derived PCC, together with upper-ocean physical observations, revealed contrasting phytoplankton community patterns across distinct post-hurricane hydrographic conditions: offshore wind-curl induced upwelling exhibited higher relative abundance of diatoms, whereas nearshore regions affected by northerly winds and Ekman transport along with enhanced upwelling were associated with coastal Karenia brevis bloom. For the first time, synergistic observations using PACE and Surface Water and Ocean Topography (SWOT) showed a rapid rise in dinoflagellates nearshore, with concurrent declines in diatoms and chlorophytes, while cryptophytes co-increased. These transient shifts likely reflected not only physical stirring but also biological responses, as freshwater inputs increased nutrient availability, and coincided with intensified red tides and spatially heterogeneous phytoplankton responses, such as, initial increases in diatoms and cyanobacteria followed by Karenia brevis dominance. Together, PACE and SWOT provide unprecedented capacity to resolve physical–biological linkages in coastal ecosystems.

Florida↗