Journal ArticleDOI
Tradeoffs and thresholds in the effects of nitrogen addition on biodiversity and ecosystem functioning: evidence from inner Mongolia Grasslands
Yongfei Bai,Jianguo Wu,Jianguo Wu,Christopher M. Clark,Shahid Naeem,Qingmin Pan,Jianhui Huang,Lixia Zhang,Xingguo Han +8 more
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TLDR
It is suggested that the critical threshold for N-induced species loss to mature Eurasian grasslands is below 1.75gNm � 2 yr � 1, and that changes in aboveground biomass, species richness, and plant functional group composition to both mature and degraded ecosystems saturate at N addition rates of approximately 10.5 gNm� 2 yr� 1.Abstract:
Nitrogen (N) deposition is widely considered an environmental problem that leads to biodiversity loss and reduced ecosystem resilience; but, N fertilization has also been used as a management tool for enhancing primary production and ground cover, thereby promoting the restoration of degraded lands. However, empirical evaluation of these contrasting impacts is lacking. We tested the dual effects of N enrichment on biodiversity and ecosystem functioning at different organizational levels (i.e., plant species, functional groups, and community) by adding N at 0, 1.75, 5.25, 10.5, 17.5, and 28.0gNm � 2 yr � 1 for four years in two contrasting field sites in Inner Mongolia: an undisturbed mature grassland and a nearby degraded grassland of the same type. N addition had both quantitatively and qualitatively different effects on the two communities. In the mature community, N addition led to a large reduction in species richness, accompanied by increased dominance of early successional annuals and loss of perennial grasses and forbs at all N input rates. In the degraded community, however, N addition increased the productivity and dominance of perennial rhizomatous grasses, with only a slight reduction in species richness and no significant change in annual abundance. The mature grassland was much more sensitive to N-induced changes in community structure, likely as a result of higher soil moisture accentuating limitation by N alone. Our findings suggest that the critical threshold for N-induced species loss to mature Eurasian grasslands is below 1.75gNm � 2 yr � 1 , and that changes in aboveground biomass, species richness, and plant functional group composition to both mature and degraded ecosystems saturate at N addition rates of approximately 10.5gNm � 2 yr � 1 . This work highlights the tradeoffs that exist in assessing the total impact of N deposition on ecosystem function.read more
Citations
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Journal ArticleDOI
Inter-annual precipitation variability alters the effects of soil resource enrichment and mycorrhizal suppression on plant communities in desert steppe
Peer ReviewDOI
Improving nitrogen safety in china: nitrogen flows, pollution and control
TL;DR: Wang et al. as discussed by the authors reviewed the historical trends of N flows in China and identified the critical threats of N loss, and described some recent success stories of N management, and finally indicated barriers to N pollution control.
Journal ArticleDOI
Alterations in substrate stoichiometry control the responses of soil diazotrophs to nutrient enrichment
Shuijin Hu,Sunil Sharma +1 more
TL;DR: In this article , the authors show that the abundance and community composition of diazotrophs responded distinctly to gradients of long-term N and P additions in an Inner Mongolia steppe.
Journal ArticleDOI
Soil Organic Carbon and pH Dominate the Effects of Nitrogen Addition on Soil Microarthropods in a Poplar Plantation in Coastal Eastern China
TL;DR: In this paper , the authors examined the response of soil microarthropods across three soil depths (0, 15 cm, 15-25 cm, 25-40 cm) to five N input levels ( 0, 5, 10, 15, 30 g N m−2 year−1) over four seasons.
Journal ArticleDOI
Relationship between species diversity and plant biomass of understory ferns in high-nitrogen habitat
TL;DR: In this paper , the authors explored the relationship between species diversity of understory ferns and plant biomass in high-nitrogen habitats in China and found that species richness had no significant effect on plant biomass under both nitrogen habitats.
References
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Journal ArticleDOI
Human alteration of the global nitrogen cycle: sources and consequences
Peter M. Vitousek,John D. Aber,Robert W. Howarth,Gene E. Likens,Pamela A. Matson,David W. Schindler,William H. Schlesinger,David Tilman +7 more
TL;DR: In this article, a review of available scientific evidence shows that human alterations of the nitrogen cycle have approximately doubled the rate of nitrogen input into the terrestrial nitrogen cycle, with these rates still increasing; increased concentrations of the potent greenhouse gas N 2O globally, and increased concentration of other oxides of nitrogen that drive the formation of photochemical smog over large regions of Earth.
Journal ArticleDOI
Nitrogen limitation on land and in the sea: How can it occur?
TL;DR: In this paper, the authors examine both how the biogeochemistry of the nitrogen cycle could cause limitation to develop, and how nitrogen limitation could persist as a consequence of processes that prevent or reduce nitrogen fixation.
Book ChapterDOI
Nitrogen - inorganic forms.
TL;DR: In this article, Bremner et al. defined the nonexchangeable NHt as the NHt in soil that cannot be replaced by a neutral potassium salt solution (SSSA, 1987), in contrast to NHt which is extractable at room temperature with such a solution.