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
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Journal ArticleDOI
Experimentally increased water and nitrogen affect root production and vertical allocation of an old-field grassland
Zhuwen Xu,Haiyan Ren,Mai-He Li,Ivano Brunner,Jinfei Yin,Heyong Liu,Deliang Kong,Xiao-Tao Lü,Tao Sun,Jiangping Cai,Ruzhen Wang,Yongyong Zhang,Peng He,Xingguo Han,Shiqiang Wan,Yong Jiang +15 more
TL;DR: In this article, the authors investigated changes of BNPP and its vertical allocation along the soil profile to 40 cm in depth in response to simultaneous increases in water and nitrogen availability over 11 years in an old-field grassland in northern China.
Journal ArticleDOI
Response of Kobresia pygmaea and Stipa purpurea Grassland Communities in Northern Tibet to Nitrogen and Phosphate Addition
Jingsheng Wang,Jingsheng Wang,Zhikai Wang,Xianzhou Zhang,Yangjian Zhang,Congqian Ran,Jun-long Zhang,Baoxiong Chen,Bingsong Zhang +8 more
TL;DR: With increasing nitrogenous fertilizer, the height, coverage, biomass, and importance value of the K. pygmaea population decreased whereas the population of S. purpurea exhibited the opposite trend, and the mixed fertilizer was beneficial to aboveground grass recovery.
Journal ArticleDOI
Nitrogen–phosphorous interactions in young northern hardwoods indicate P limitation: foliar concentrations and resorption in a factorial N by P addition experiment
Kara Gonzales,Ruth D. Yanai +1 more
TL;DR: The results suggest that decades of anthropogenic N deposition may have tipped the balance to P limitation in Temperate forests on glaciated soils, but long-term N × P manipulations in this biome are lacking.
Journal ArticleDOI
Soil and climate effects on leaf nitrogen and phosphorus stoichiometry along elevational gradients
TL;DR: In this paper, the contribution of climate and soil nutrients on leaf nitrogen and phosphorus concentrations across plant life-forms (trees, shrubs, and herbs) was investigated, especially along elevational gradients.
Journal ArticleDOI
Soil extracellular enzyme activities and the abundance of nitrogen-cycling functional genes responded more to N addition than P addition in an Inner Mongolian meadow steppe.
Hong Xiao,Helong Yang,Mengli Zhao,Thomas A. Monaco,Yuping Rong,Ding Huang,Qian Song,Kun Zhao,Deping Wang +8 more
TL;DR: The importance of soil N availability in regulating microbial metabolism and soil N-loss potential is highlighted, and the understanding of the mechanisms responsible for variation in microbial nutrient cycling in meadow steppe soils is enhanced.
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.