The biodiversity - N cycle relationship: a 15N tracer experiment with soil from plant mixtures of varying diversity to model N pool sizes and transformation rates

Abstract We conducted a 15N tracer experiment in laboratory microcosms with field-fresh soil samples from a biodiversity experiment to evaluate the relationship between grassland biodiversity and N cycling. To embrace the complexity of the N cycle, we determined N exchange between five soil N pools (labile and recalcitrant organic N, dissolved NH4+ and NO3− in soil solution, and exchangeable NH4+) and eight N transformations (gross N mineralization from labile and recalcitrant organic N, NH4+ immobilization into labile and recalcitrant organic N, autotrophic nitrification, heterotrophic nitrification, NO3− immobilization, adsorption of NH4+) expected in aerobic soils with the help of the N-cycle model Ntrace. We used grassland soil of the Jena Experiment, which includes plant mixtures with 1 to 60 species and 1 to 4 functional groups (legumes, grasses, tall herbs, small herbs). The 19 soil samples of one block of the Jena Experiment were labeled with either 15NH4+ or 15NO3- or both. In the presence of legumes, gross N mineralization and autotrophic nitrification increased significantly because of higher soil N concentrations in legume-containing plots and high microbial activity. Similarly, the presence of grasses significantly increased the soil NH4+ pool, gross N mineralization, and NH4+ immobilization, likely because of enhanced microbial biomass and activity by providing large amounts of rhizodeposits through their dense root systems. In our experiment, previously reported plant species richness effects on the N cycle, observed in a larger-scale field experiment within the Jena Experiment, were not seen. However, specific plant functional groups had a significant positive impact on the N cycling in the incubated soil samples.

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Nitrogen dynamics after two years of elevated CO2 in phosphorus limited Eucalyptus woodland

Biogeochemistry ◽

10.1007/s10533-020-00699-y ◽

2020 ◽

Vol 150 (3) ◽

pp. 297-312

Author(s):

Louise C. Andresen ◽

Yolima Carrillo ◽

Catriona A. Macdonald ◽

Laura Castañeda-Gómez ◽

Samuel Bodé ◽

...

Keyword(s):

Carbon Dioxide ◽

Nutrient Availability ◽

N Mineralization ◽

Free Amino ◽

Organic N ◽

Limiting Factor ◽

N Availability ◽

Available N ◽

Gross N Mineralization ◽

N Cycle

Abstract It is uncertain how the predicted further rise of atmospheric carbon dioxide (CO2) concentration will affect plant nutrient availability in the future through indirect effects on the gross rates of nitrogen (N) mineralization (production of ammonium) and depolymerization (production of free amino acids) in soil. The response of soil nutrient availability to increasing atmospheric CO2 is particularly important for nutrient poor ecosystems. Within a FACE (Free-Air Carbon dioxide Enrichment) experiment in a native, nutrient poor Eucalyptus woodland (EucFACE) with low soil organic matter (≤ 3%), our results suggested there was no shortage of N. Despite this, microbial N use efficiency was high (c. 90%). The free amino acid (FAA) pool had a fast turnover time (4 h) compared to that of ammonium (NH4+) which was 11 h. Both NH4-N and FAA-N were important N pools; however, protein depolymerization rate was three times faster than gross N mineralization rates, indicating that organic N is directly important in the internal ecosystem N cycle. Hence, the depolymerization was the major provider of plant available N, while the gross N mineralization rate was the constraining factor for inorganic N. After two years of elevated CO2, no major effects on the pools and rates of the soil N cycle were found in spring (November) or at the end of summer (March). The limited response of N pools or N transformation rates to elevated CO2 suggest that N availability was not the limiting factor behind the lack of plant growth response to elevated CO2, previously observed at the site.

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Effects of Changing Temperature on Gross N Transformation Rates in Acidic Subtropical Forest Soils

Forests ◽

10.3390/f10100894 ◽

2019 ◽

Vol 10 (10) ◽

pp. 894

Author(s):

Xiaoqian Dan ◽

Zhaoxiong Chen ◽

Shenyan Dai ◽

Xiaoxiang He ◽

Zucong Cai ◽

...

Keyword(s):

Temperature Change ◽

N Mineralization ◽

Organic N ◽

Mineralization Rate ◽

Soil N ◽

Autotrophic Nitrification ◽

N Transformation ◽

Gross N Transformation ◽

Increasing Temperature ◽

N Pool

Soil temperature change caused by global warming could affect microbial-mediated soil nitrogen (N) transformations. Gross N transformation rates can provide process-based information about abiotic–biotic relationships, but most previous studies have focused on net rates. This study aimed to investigate the responses of gross rates of soil N transformation to temperature change in a subtropical acidic coniferous forest soil. A 15N tracing experiment with a temperature gradient was carried out. The results showed that gross mineralization rate of the labile organic N pool significantly increased with increasing temperature from 5 °C to 45 °C, yet the mineralization rate of the recalcitrant organic N pool showed a smaller response. An exponential response function described well the relationship between the gross rates of total N mineralization and temperature. Compared with N mineralization, the functional relationship between gross NH4+ immobilization and temperature was not so distinct, resulting in an overall significant increase in net N mineralization at higher temperatures. Heterotrophic nitrification rates increased from 5 °C to 25 °C but declined at higher temperatures. By contrast, the rate of autotrophic nitrification was very low, responding only slightly to the range of temperature change in the most temperature treatments, except for that at 35 °C to 45 °C, when autotrophic nitrification rates were found to be significantly increased. Higher rates of NO3− immobilization than gross nitrification rates resulted in negative net nitrification rates that decreased with increasing temperature. Our results suggested that, with higher temperature, the availability of soil N produced from N mineralization would significantly increase, potentially promoting plant growth and stimulating microbial activity, and that the increased NO3− retention capacity may reduce the risk of leaching and denitrification losses in this studied subtropical acidic forest.

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The soil N cycle: new insights and key challenges

SOIL ◽

10.5194/soil-1-235-2015 ◽

2015 ◽

Vol 1 (1) ◽

pp. 235-256 ◽

Cited By ~ 87

Author(s):

J. W. van Groenigen ◽

D. Huygens ◽

P. Boeckx ◽

Th. W. Kuyper ◽

I. M. Lubbers ◽

...

Keyword(s):

N Cycling ◽

Greenhouse Gas Mitigation ◽

Future Research ◽

N Fixation ◽

Gaseous Emissions ◽

Soil N ◽

Personal View ◽

Total N ◽

N Cycle ◽

Soil N Cycle

Abstract. The study of soil N cycling processes has been, is, and will be at the centre of attention in soil science research. The importance of N as a nutrient for all biota; the ever-increasing rates of its anthropogenic input in terrestrial (agro)ecosystems; its resultant losses to the environment; and the complexity of the biological, physical, and chemical factors that regulate N cycling processes all contribute to the necessity of further understanding, measuring, and altering the soil N cycle. Here, we review important insights with respect to the soil N cycle that have been made over the last decade, and present a personal view on the key challenges of future research. We identify three key challenges with respect to basic N cycling processes producing gaseous emissions: 1. quantifying the importance of nitrifier denitrification and its main controlling factors; 2. characterizing the greenhouse gas mitigation potential and microbiological basis for N2O consumption; 3. characterizing hotspots and hot moments of denitrification Furthermore, we identified a key challenge with respect to modelling: 1. disentangling gross N transformation rates using advanced 15N / 18O tracing models Finally, we propose four key challenges related to how ecological interactions control N cycling processes: 1. linking functional diversity of soil fauna to N cycling processes beyond mineralization; 2. determining the functional relationship between root traits and soil N cycling; 3. characterizing the control that different types of mycorrhizal symbioses exert on N cycling; 4. quantifying the contribution of non-symbiotic pathways to total N fixation fluxes in natural systems We postulate that addressing these challenges will constitute a comprehensive research agenda with respect to the N cycle for the next decade. Such an agenda would help us to meet future challenges on food and energy security, biodiversity conservation, water and air quality, and climate stability.

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Implications of carbon saturation model structure for simulated nitrogen mineralization dynamics

Biogeosciences Discussions ◽

10.5194/bgd-11-9667-2014 ◽

2014 ◽

Vol 11 (6) ◽

pp. 9667-9695 ◽

Cited By ~ 3

Author(s):

C. M. White ◽

A. R. Kemanian ◽

J. P. Kaye

Keyword(s):

Soil Properties ◽

N Mineralization ◽

Storage Capacity ◽

Clay Content ◽

N Cycling ◽

Transfer Efficiency ◽

Net N Mineralization ◽

Saturation Ratio ◽

Carbon Saturation ◽

C And N

Abstract. Carbon (C) saturation theory suggests that soils have a~limited capacity to stabilize organic C and that this capacity may be regulated by intrinsic soil properties such as clay content and mineralogy. While C saturation theory has advanced our ability to predict soil C stabilization, we only have a weak understanding of how C saturation affects N cycling. In biogeochemical models, C and N cycling are tightly coupled, with C decomposition and respiration driving N mineralization. Thus, changing model structures from non-saturation to C saturation dynamics can change simulated N dynamics. Carbon saturation models proposed in the literature calculate a theoretical maximum C storage capacity of saturating pools based on intrinsic soil properties, such as clay content. The extent to which current C stocks fill the storage capacity of the pool is termed the C saturation ratio, and this ratio is used to regulate either the efficiency or the rate of C transfer from donor to receiving pools. In this study, we evaluated how the method of implementing C saturation and the number of pools in a model affected net N mineralization from decomposing plant residues. In models that use the C saturation ratio to regulate transfer efficiency, C saturation affected N mineralization, while in those in which the C saturation ratio regulates transfer rates, N mineralization was independent of C saturation. When C saturation ratio regulates transfer efficiency, as the saturation ratio increases, the threshold C : N ratio at which positive net N mineralization occurs also increases because more of the C in the residue is respired. In a single-pool model where C saturation ratio regulated the transfer efficiency, predictions of N mineralization from residue inputs were unrealistically high, missing the cycle of N immobilization and mineralization typically seen after the addition of high C : N inputs to soils. A more realistic simulation of N mineralization was achieved simply by adding a second pool to the model to represent short-term storage and turnover of C and N in microbial biomass. These findings increase our understanding of how to couple C saturation and N mineralization models, while offering new hypotheses about the relationship between C saturation and N mineralization that can be tested empirically.

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ANALISIS C-ORGANIK, NITROGEN DAN C/N TANAH PADA LAHAN AGROWISATA BEKEN JAYA DI KABUPATEN KUANTAN SINGINGI

Jurnal AGROSAINS dan TEKNOLOGI ◽

10.24853/jat.5.1.11-18 ◽

2020 ◽

Vol 5 (1) ◽

pp. 11

Author(s):

Trinop Sagiarti ◽

Deno Okalia ◽

Gusti Markina

Keyword(s):

Land Use ◽

Random Sampling ◽

Soil Analysis ◽

Chemical Properties ◽

Chemical Characteristic ◽

Soil Samples ◽

Organic N ◽

Total N ◽

Gas Drilling ◽

Very High

Soil fertility determined by land management . Land use in the farmers to Beken Jaya in Kuantan Singingi has been going on for seven years to technique fertilizing not recommended, so it is important to knew soil chemical characteristic are now being to sustainable agriculture.This research in the soil samples uses the method purposive random sampling in 15 points gas drilling land as deep as 20 cm.Parameter examined is pH , C-organic , N-total , N-available and ratio C / N. All the data compared to table criteria of the chemical properties the ground by LPT 1993. Based on the results of the soil analysis in Agrowisata Beken Jaya can be concluded features chemical pH 5,88 -6,41 ( criteria midle acid ) , C-organik 0.25 % - 1,18 % ( criteria very low until low ) , N-total 0,30 -1,16 % ( criteria moderate to very high ), and C/N 0,24-3,97 (criteria very low)

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How does simulated climate change affect the susceptibility of SOM to priming by LMWOS in the Subarctic?

10.5194/egusphere-egu21-10220 ◽

2021 ◽

Author(s):

Meng Na ◽

Mingyue Yuan ◽

Lettice Hicks ◽

Johannes Rousk

Keyword(s):

Climate Change ◽

Plant Communities ◽

N Mineralization ◽

Fungal Growth ◽

N Fertilization ◽

C Mineralization ◽

Soil C ◽

Gross N Mineralization ◽

Simulated Climate ◽

Simulated Climate Change

Soil organic matter (SOM) stabilization plays an important role in the long-term storage of carbon (C). However, many ecosystems are undergoing climate change, which will change the soil C balance via altered plant communities and productivity that change C inputs, and altered C losses via changes in SOM decomposition. The ongoing change of aboveground plant communities in the Subarctic (&#8220;greening&#8221;) will increase rhizosphere inputs containing low molecular weight organic substances (LMWOS), which will likely affect C-starved microbial decomposers and their subsequent contribution to SOM mineralization (priming effect).In the present study, we simulated the effects of climate change with N fertilization (simulating warming enhanced nutrient cycling) and litter additions (simulating arctic greening) in Abisko, Sweden. The 6 sampled field-treatments included a full factorial combination of 3-years of chronic N addition and litter additions, as well as, a single year of extreme climate change (3x N fertilizer or litter additions in one growth season). We found that N treatments changed plant community composition and productivityand that the associated shift in belowground LMWOS induced shifts in the soil microbial community. In the chronic N fertilization treatments, plant productivity, and therefore belowground LMWOS input, increased. This coincided with a tendency for more bacterial dominated decomposition (lower fungi/bacterial growth ratio). However, N treatments had no effect on soil C mineralization, but increased gross N mineralization.These responses in belowground communities and processes driven by rhizosphere input prompted the next question: how does simulated climate change affect the susceptibility of SOM to priming by LMWOS? To assess this question and determine the microbial mechanisms underpinning priming of SOM mineralization, we added a factorial set of additions including 13C-glucose with and without mineral N, and 13C-alanine semi-continuously (every 48 hours) to simulate the effect of rhizosphere LMWOS on SOM mineralization and microbial activity. We incubated these samples for 2 weeks and assessed the priming of soil C and gross N mineralization, bacterial and fungal growth rates, PLFAs, enzyme activities, and microbial C use efficiency (CUE). We found that alanine addition primed soil C mineralization by 34%, which was higher than soil C priming induced by glucose and glucose with N. Furthermore, glucose primed fungal growth, whereas the alanine primed bacterial growth, but microbial PLFAs did not respond to either treatment. The C enzyme acquisition activity was higher than N enzyme acquisition activity in all the treatments, while P enzyme acquisition activity was higher than C for all the treatments. Surprisingly, this suggested a chronic microbial limitation by P, which was unaffected by field and lab treatments. LMWOS additions generally reduced microbial CUE. Responses of microbial mineralization of N from SOM to LMWOS suggested a directed microbial effort towards targeting resources that limited bacterial or fungal growth, suggesting that microbial SOM-use shifted to N-rich components (selective microbial &#8220;N-mining&#8221;), in contrast with enzyme results. Surprisingly, alanine primed the highest N mineralization compared other additions indicating that there was strong N-mining even if N was sufficient.

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Nitrogen Cycling

Structure and Function of an Alpine Ecosystem ◽

10.1093/oso/9780195117288.003.0019 ◽

2001 ◽

Author(s):

Melany C. Fisk ◽

Paul D. Brooks

Keyword(s):

Spatial Variation ◽

Water Availability ◽

Growing Season ◽

N Cycling ◽

Alpine Tundra ◽

N Transformations ◽

Cold Temperatures ◽

Niwot Ridge ◽

N Cycle ◽

Large N

In this chapter, we discuss the current understanding of internal N cycling, or the flow of N through plant and soil components, in the Niwot Ridge alpine ecosystem. We consider the internal N cycle largely as the opposing processes of uptake and incorporation of N into organic form and mineralization of N from organic to inorganic form. We will outline the major organic pools in which N is stored and discuss the transfers of N into and from those pools. With a synthesis of information regarding the various N pools and relative turnover of N through them, we hope to provide greater understanding of the relative function of different components of the alpine N cycle. Because of the short growing season, cold temperatures, and water regimes tending either toward very dry or very wet extremes, the alpine tundra is not a favorable ecosystem for either production or decomposition. Water availability, temperature, and nutrient availability (N in particular) all can limit alpine plant growth (chapter 9). Cold soils also inhibit decomposition so that N remains bound in organic matter and is unavailable for plant uptake (chapter 11). Consequently, N cycling in the alpine often is presumed to be slow and conservative (Rehder 1976a, 1976b; Holzmann and Haselwandter 1988). Nonetheless, studies reveal large spatial variation in primary production and N cycling in alpine tundra across gradients of snowpack accumulation, growing season water availability, and plant species composition (May and Webber, 1982, Walker et al., 1994, Bowman, 1994, Fisk et al. 1998; chapter 9). Furthermore, evidence for relatively large N transformations under seasonal snowcover (Brooks et al., 1995a, 1998) and maintenance of high microbial biomass in frozen soils (Lipson et al. 1999a) provide a complex temporal component of N cycling on Niwot Ridge. Our discussion of N cycling on Niwot Ridge will focus on two main points: first, the spatial variation in N turnover in relation to snowpack regimes and plant community distributions; and second, the temporal variability of N transformations during both snow-free and snow-covered time periods.

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Variations of belowground C and N cycling between arbuscular mycorrhizal and ectomycorrhizal forests across China

Soil Research ◽

10.1071/sr19377 ◽

2020 ◽

Vol 58 (5) ◽

pp. 441 ◽

Cited By ~ 1

Author(s):

Jiwei Li ◽

Zhouping Shangguan ◽

Lei Deng

Keyword(s):

Soil Respiration ◽

Forest Ecosystems ◽

Arbuscular Mycorrhizal ◽

N Cycling ◽

Microbial Biomass C ◽

N Cycle ◽

Positive Effects ◽

Litter Input ◽

C And N ◽

C And N Cycling

Forests associating with arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi may have distinct belowground carbon (C) and nitrogen (N) cycle processes. However, there are little available data providing evidence for the effects of trees associating with mycorrhizal type on belowground C and N cycling in forest ecosystems in China. Here, we collected a database of 26 variables related to belowground C and N cycling from 207 studies covering 209 sampling sites in China, to better understand the variations in belowground C and N cycling between the two mycorrhizal types in forest ecosystems along a climatic gradient. The AM forests had significantly lower soil total C and N contents, and soil microbial biomass C and N, than ECM forests, probably due to differences in litter quality (N and C/N) between AM and ECM forest types. In contrast, AM forests had significantly higher litter input, litter decomposition and soil respiration than ECM forests. Temperature and precipitation had significant positive effects on litter input and decomposition, soil total C and N contents, and soil respiration in AM and ECM forests. Overall, our results indicated that mycorrhizal type strongly affected belowground C and N cycle processes in forest ecosystems. Moreover, AM forests are likely more sensitive and ECM forests have a greater ability to adapt to global climate change.

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Seasonal trends of gross N mineralization in a natural calcareous grassland

Global Change Biology ◽

10.1046/j.1365-2486.1999.00232.x ◽

1999 ◽

Vol 5 (4) ◽

pp. 423-431 ◽

Cited By ~ 30

Author(s):

Nicola Jamieson ◽

RosS. Monaghan ◽

Declan Barraclough

Keyword(s):

N Mineralization ◽

Calcareous Grassland ◽

Gross N Mineralization ◽

Seasonal Trends

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Relationship between mineral N content and N mineralization rate in disturbed and undisturbed soil samples incubated under field and laboratory conditions

Soil Research ◽

10.1071/sr9920477 ◽

1992 ◽

Vol 30 (4) ◽

pp. 477 ◽

Cited By ~ 21

Author(s):

J Sierra

Keyword(s):

N Mineralization ◽

Negative Relationship ◽

Feedback Mechanism ◽

Soil Samples ◽

Mineralization Rate ◽

Mineral N ◽

Undisturbed Soil ◽

N Content ◽

Undisturbed Samples

An investigation of in situ N mineralization, using undisturbed soil samples, indicated a negative relationship between the mineral N content [(NO3+NH4)-N] at the beginning of the experiment and the mineral N produced during it. This suggests that a maximum value of mineral N accumulation in intact soil cores could be calculated from the relationship between mineral N content and N mineralization rate. This value would be related to the size of the mineralizable N pool. If this hypothesis is true, the amount of mineralizable N could be estimated from in situ incubations and utilized in the modelling of N mineralization in the field. The aim of this work was to verify this hypothesis. The relationship between the mineral N content and the N mineralization rate was analysed for in situ and laboratory incubations of disturbed and undisturbed soil samples. A negative relationship between the two variables was only obtained for the experiments carried out with undisturbed samples (in the field and laboratory incubations) when the soil moisture content was not limiting for N mineralization. Futhermore, in undisturbed samples, a negative relationship between mineralization rates of consecutive incubation periods was observed, i.e. the soil sample producing relatively more, during a given period, produced relatively less in the following period. This relationship suggests a feedback mechanism operating in N mineralization which would be related to a mineralization-immobilization process in soil microsites. Thus, the N mineralization pattern was more complex than that described by initial hypothesis. The possible consequence of this feedback mechanism on in situ N dynamics is discussed.

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