scholarly journals Soil Nitrate Mediates the Responses of Plant Community Production to the Frequency of N Addition in a Temperate Grassland: A Decadal Field Experiment

2021 ◽  
Author(s):  
Changchun Song ◽  
Yuqiu Zhang ◽  
Zhengru Ren ◽  
Haining Lu ◽  
Xu Chen ◽  
...  
Keyword(s):  
Plant Community ◽  
Net Primary Productivity ◽  
Northern China ◽  
N Deposition ◽  
Temperate Grassland ◽  
N Addition ◽  
Aboveground Net Primary Productivity ◽  
Atmospheric N Deposition ◽  
N Enrichment

Abstract PurposeNitrogen (N) enrichment through either artificial N application or atmospheric N deposition often increases ecosystem aboveground net primary productivity (ANPP). Therefore, results from N addition experiments have been used to assess the effects of atmospheric N deposition on ecosystems. However, the frequency of atmospheric N deposition is higher than that of artificial N addition. Whether the frequency of N addition alters the long-term response of ecosystem ANPP remains unclear. MethodsWe conducted a N addition frequency experiment from 2010 in a temperate grassland, northern China. Plant community ANPP was collected in 2019 and 2020, and soil physicochemical properties were measured in 2020. ResultsPlant community ANPP was significantly enhanced by N addition, whereas these increments declined with the frequency of N addition. The responses of the grasses ANPP to the frequency of N addition were similar to those of the plant community ANPP. Forbs ANPP was not significantly altered by the frequency of N addition. Meanwhile, soil ammonium and nitrate (NO3−–N) concentrations decreased with increasing N addition frequency, while the soil water content (SWC) and pH were similar among the frequencies of N addition. Moreover, SWC and soil NO3−–N jointly promoted grasses ANPP, ultimately increasing the plant community ANPP. ConclusionOur findings extend the water and N co-limitation hypothesis by specifying the preference for NO3−–N in arid/semi-arid regions. This study also illustrates that a higher frequency of N addition is more suitable for assessing the long-term impacts of atmospheric N deposition on ecosystems.

scholarly journals Fungi exposed to chronic nitrogen enrichment are less able to decay leaf litter

2016 ◽  
Author(s):  
Linda T.A. van Diepen ◽  
Serita D. Frey ◽  
Elizabeth A. Landis ◽  
Eric W. Morrison ◽  
Anne Pringle
Keyword(s):  
Growth Rates ◽  
Common Garden ◽  
N Deposition ◽  
Plant Litter ◽  
Atmospheric N Deposition ◽  
Saprotrophic Fungi ◽  
Soil C ◽  
Litter Decay ◽  
N Enrichment

AbstractSaprotrophic fungi are the primary decomposers of plant litter in temperate forests, and their activity is critical for carbon (C) and nitrogen (N) cycling. Simulated atmospheric N deposition is associated with reduced fungal biomass, shifts in fungal community structure, slowed litter decay, and soil C accumulation. Although rarely studied, N deposition may also result in novel selective pressures on fungi, affecting evolutionary trajectories. To directly test if long-term N enrichment reshapes fungal behaviors, we isolated decomposer fungi from a longterm (28 year) N addition experiment and used a common garden approach to compare growth rates and decay abilities of isolates from control and N amended plots. Both growth and decay were significantly altered by long-term exposure to N enrichment. Changes in growth rates were idiosyncratic, but litter decay by N isolates was generally lower compared to control isolates of the same species, a response not readily reversed when N isolates were grown in control (low N) environments. Changes in fungal behaviors accompany and perhaps drive previously observed N-induced shifts in fungal diversity, community composition, and litter decay dynamics.

Neutral responses of plant community Ca concentration to nitrogen enrichment in a semi-arid grassland

2021 ◽  
Author(s):  
Shuang-Li Hou ◽  
Xiao-Tao Lü ◽  
Jun-Jie Yang
Keyword(s):  
Functional Group ◽  
Northern China ◽  
N Deposition ◽  
N Addition ◽  
Health It ◽  
Essential Nutrient ◽  
N Enrichment ◽  
Open Question ◽  
Semi Arid

Abstract Aims Calcium (Ca) is an essential nutrient for plant growth and Ca concentrations in forage have important implications for ruminant diet and health. It remains an open question whether forage Ca concentration would be decreased by increasing nitrogen (N) deposition. Methods We manipulated the increasing rates of N addition (2008-2015) in a semi-arid grassland, northern China. Plant Ca concentrations for all species were examined in each plot under N treatment. The Ca concentrations at functional group and community levels were calculated based on the concentration of each species presented and their relative biomass in each plot. Important findings We found that community-level Ca concentration remained stable across a gradient of wide-ranged N addition rates, although Ca concentration at both species and functional group levels showed negative responses to N enrichment. Given that forbs had higher Ca concentration than grasses, the increasing relative biomass of forbs canceled out the negative responses of species-level and functional group-level Ca concentration. Our results further showed that community Ca pool showed a positive but saturating response to N addition, with a threshold at the rate of 10 g N m -2 yr -1. Our findings highlight the role of changes in plant relative biomass in controlling the responses of forage Ca concentration and stock to N enrichment.

scholarly journals Contrasting Responses of Soil Respiration Components in Response to Five-Year Nitrogen Addition in a Pinus tabulaeformis Forest in Northern China

Forests ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 544 ◽  
Author(s):  
Bo Zhao ◽  
Yan Geng ◽  
Jing Cao ◽  
Lu Yang ◽  
Xiuhai Zhao
Keyword(s):  
Soil Respiration ◽  
Microbial Biomass Carbon ◽  
Northern China ◽  
Nitrogen Addition ◽  
N Deposition ◽  
Fine Root Biomass ◽  
Pinus Tabulaeformis ◽  
N Availability ◽  
N Addition ◽  
N Enrichment

Increasing atmospheric nitrogen (N) deposition has profound effects on carbon (C) cycling in forest ecosystems. As an important part of belowground C dynamics, soil respiration is potentially affected by changing N availability. However, the responses of total soil respiration (RST) and its three components, soil respiration derived from plant roots (RSR), root-free soil (RSS) and the litter layer (RSL), to such N enrichment remains poorly understood. To assess the effects of N enrichment on soil respiration components, three levels of N addition, namely low (LN, 50 kg N ha−1 year−1), medium (MN, 100 kg N ha−1 year−1) and high (HN, 150 kg N ha−1 year−1), were conducted over five growing seasons from 2011 to 2015 in a temperate Chinese pine (Pinus tabulaeformis) forest in northern China. A control plot without N addition (CK) was also established. The five-year mean annual rate of RST was 2.18 ± 0.43 μmol m−2 s−1, and the contributions of RSR, RSS and RSL were 8.8 ± 3.1%, 82.2 ± 4.5% and 9.0 ± 5.5%, respectively. Compared with CK, RST was significantly increased by 16.5% in the HN plots, but not in the LN or MN treatments. RSS was significantly decreased by 18.1%, 26.6% and 18.4% in the LN, MN and HN plots, respectively, due to the reduction of both microbial biomass carbon (MBC) and enzyme activity. In contrast, RSR was increased by more than twice under the MN treatment, which promoted root growth and activity (higher fine root biomass and N concentration). A significant elevation in RSL was only detected in the HN plots, where the increased litter input enhanced litter decomposition and hence RSL. Our findings clearly demonstrated that N addition of different intensities had different effects on soil components. In particular, the above- and belowground components of heterotrophic respiration, RSL and RSR, showed contrasting responses to high level addition of N. Thus, we highlight that the response of soil respiration components to N addition should be examined individually. Our results may contribute to a better understanding of soil respiration dynamics under future N scenarios, and have important implications in forest management.

scholarly journals Impacts of long-term nitrogen addition on nitrous oxide in a temperate grassland

2021 ◽  
Vol 293 ◽  
pp. 01001
Author(s):  
Si Chen ◽  
Tianpeng Gao ◽  
Tianxiang Hao ◽  
Kaihui Li ◽  
Xuejun Liu
Keyword(s):  
Nitrous Oxide ◽  
Structural Equation ◽  
Industrial Revolution ◽  
Nitrogen Addition ◽  
N Deposition ◽  
Temperate Grassland ◽  
Equation Modeling ◽  
Limiting Factor ◽  
N Addition

Atmospheric nitrogen (N) deposition has increased dramatically due to increased human activities since the industrial revolution. However, it is still unclear what the responses of soil nitrous oxide (N2O) is to long-term elevated N deposition in a temperate grassland. Here, we conducted an in situ field experiment to investigate these responses to long-term high N addition on a temperate steppe in Inner Mongolia, China, from April 2017 to October 2018. Soil N2O emissions significantly increased by long-term N addition, use of structural equation modeling (SEM) showed that topsoil (0-5 cm) NH4+-N content was the most important limiting factor for N2O emission. Our results indicate that long-term high N addition showed a significantly increase in N2O emission in this temperate grassland.

Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long term field manipulation and modelling study 

2021 ◽  
Author(s):  
Christopher Taylor ◽  
Victoria Janes-Bassett ◽  
Gareth Phoenix ◽  
Ben Keane ◽  
Iain Hartley ◽  
...  
Keyword(s):  
N Deposition ◽  
Calcareous Grassland ◽  
Organic P ◽  
N Addition ◽  
Soil C ◽  
P Limitation ◽  
P Cycling ◽  
Nutrient Manipulation ◽  
N And P Cycling

<p>In ecosystems where nitrogen (N) limits plant productivity, N deposition can stimulate plant growth, and consequently, promote carbon (C) sequestration by increasing input of detrital C and other forms of plant C to the soil. However, other forms of nutrient limitation such as phosphorus (P) limitation and N-P co-limitation are widespread and may increase in prevalence with N deposition. Our understanding of how terrestrial ecosystem C, N and P cycling may be affected by N deposition when N is not the sole limiting resource is fairly limited. In this work, we investigate the consequences of enhanced N addition on C, N and P cycling in grasslands that exhibit contrasting forms of nutrient limitation.</p><p>We do so by collecting data from a long-term nutrient manipulation experiment on two N-P co-limited grasslands; an acidic grassland of stronger N-limitation and a calcareous grassland of stronger P limitation, and integrating this into a mechanistic C, N and P cycling model (N14CP). To simulate the experimental grasslands and explore the role of P access mechanisms in determining ecosystem state, we allowed P access to vary, and compared the outputs to plant-soil C, N and P data. Combinations of organic P access and inorganic P availability most closely representing data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation.</p><p>The modelled grasslands showed contrasting responses to simulated N deposition. In the acidic grassland, N addition greatly increased C stocks by stimulating biomass productivity, but the same N treatments reduced the organic C pool in the calcareous grassland. Nitrogen deposition exacerbated P limitation in the calcareous grassland by reducing the size of the bioavailable P pool to plants, reducing biomass input to the soil C pool. Plant acquisition of organic P played an important role in determining the nutrient conditions of the grasslands, as both simulated grasslands increased organic P uptake to meet enhanced P demand driven by N deposition. Greater access to organic P in the acidic grassland prevented a shift to P limitation under elevated levels of N deposition, but organic P access was too low in the calcareous grassland to prevent worsening P limitation.</p><p>We conclude that grasslands of differing limiting nutrients may respond to N deposition in contrasting ways, and stress that as N deposition shifts ecosystems toward P limitation, a globally important carbon sink risks degradation.</p>

scholarly journals 15N natural abundances in two podsol soils of two spruce forests differing in their atmospheric N deposition conditions

2011 ◽  
Vol 51 (No. 9) ◽  
pp. 416-422 ◽  
Author(s):  
S.P. Sah
Keyword(s):  
Mineral Soil ◽  
Vertical Gradient ◽  
N Deposition ◽  
Climatic Conditions ◽  
Organic Layer ◽  
Atmospheric N Deposition ◽  
Spruce Forests ◽  
Humus Layer ◽  
N Enrichment ◽  
Deposition Conditions

This study aims to investigate the changes in isotope ratios in foliage and soils of the two spruce forests [Picea abies (L.) Karst.] differing greatly in their atmospheric N deposition and climatic conditions. As expected, both N concentrations and <sup>15</sup>N values in both needles and litter were found to be significantly higher in the Solling stand (N-saturated) compared to the Hyytial&auml; stand (N-poor). For the N-limited site (Hyytial&auml; plot), a typical vertical gradient of the soil <sup>15</sup>N-enrichment (both in organic and mineral soil) was observed. The N-saturated site (Solling) differs from the N-limited site (Hyytial&auml;) with respect to the <sup>15</sup>N abundance trend in organic layer. In the upper organic layer up to O-f horizon, i.e. mor layer (0&ndash;3.5 cm depth) of Solling plot, there is almost a trend of slight soil <sup>15</sup>N-depletion with increasing depth, and then there is a <sup>15</sup>N-enrichment from O-h horizon (humus layer) of organic layer to mineral soil horizons. This is explained by the presence of prominent NO<sub>3</sub><sup>&ndash;</sup> leaching at this plot

Nitrogen addition accelerates ecosystem phosphorus cycling at multiple scales in a temperate grassland of Northeast China

2020 ◽  
Author(s):  
Haiying Cui ◽  
Manuel Delgado-Baquerizo ◽  
Wei Sun ◽  
Jian-Ying Ma ◽  
Wenzheng Song ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Northeast China ◽  
Nitrogen Addition ◽  
N Deposition ◽  
Organic P ◽  
N Addition ◽  
Resorption Efficiency ◽  
P Deficiency ◽  
P Mineralization ◽  
N Enrichment

&lt;p&gt;Plant phosphorus (P) resorption, mutualistic symbiosis with mycorrhizas, such as arbuscular mycorrhizal fungi (AMF) and soil organic P mineralization are crucial strategies for acquiring sufficient P to meet plant nutrient demand. Which is the main strategy, however, responding to elevated nitrogen (N) addition to alleviate P deficiency caused by N enrichment remains unclear in terrestrial ecosystems. We explored the responses of foliar P resorption of dominate species (Leymus chinensis), soil microbial properties and organic P mineralization to multi-level N addition in a temperate meadow steppe, Northeast China. We found the enhancements in plant biomass, microbial biomass C and N (MBC, MBN), alkaline phosphatase activities (ALP), and phoD gene abundance (main gene coded soil ALP), while the reductions in soil pH, available P, microbial biomass P, and AMF abundance, and no significant responses of foliar P content under simulative N deposition. When the rates exceeded the threshold 10 g N m&lt;sup&gt;-2&lt;/sup&gt;yr&lt;sup&gt;-1&lt;/sup&gt;, plants and microbes had little additional responses to N enrichment. Notably, N addition had distinct effects on three plant P acquisition strategies, that no conspicuous increase in P resorption efficiency, reduced dependence on mutualistic with AMF symbiosis and accelerated organic P mineralization. A positive correlation between ALP activity, phoD gene abundance and P mineralization rate suggested increases in phosphatase activities and its functional gene copies play crucial roles in organic P mineralization. Nitrogen addition aggravated P deficiency to the production of plant and microbial biomass, which further accelerated soil organic P mineralization and foliar P resorption. Due to lack of plasticity in P resorption efficiency and reduced dependence on mutualistic with AMF symbiosis, however, the organic P mineralization dominated in P acquisition to meet increased P demand. Furthermore, the increase in ALP activities, activation of phoD genes and decrease in soil pH were the main pathways to accelerate organic P mineralization and consequently alleviated P deficiency caused by anthropogenic N deposition, especially at conditions of N saturation. Our results provide strong evidences that N addition can accelerate the rate of P cycling and mobilize plant P uptake strategies such as soil organic P mineralization and leaf P resorption, which are important to better maintain sustainable ecosystem development in the more fertilized word.&lt;/p&gt;&lt;p&gt;Acknowledgments: This work was supported by the National Key Research and Development Program of China (2016YFC0500602), National Natural Science Foundation of China (31570470, 31870456), the Fundamental Research Funds for the Central Universities (2412018ZD010), and the Program of Introducing Talents of Discipline to Universities (B16011). H.C. acknowledges support from Chinese Scholarship Council (CSC).&lt;/p&gt;

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.

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