Priming effect of litter mineralization: the role of root exudate depends on its interactions with litter quality and soil condition

Tian, Kai; Kong, Xiangshi; Yuan, Liuhuan; Lin, Hong; He, Zaihua; Yao, Bei; Ji, Yanli; Yang, Junbo; Sun, Shucun; Tian, Xingjun

doi:10.1007/s11104-019-04070-5

Cited by 46 publications

(19 citation statements)

References 72 publications

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“…The calibrated values for these two parameters -the maximum depolymerization rate of POM and maximum decay rate of stable MAOM -were 0.0033 and 0.00034 d −1 , respectively, which indicated the average turnover time for sMAOM was an order of magnitude slower than POM. This generally aligns with a wealth of experimental data quantifying average turnover times of these two SOM fractions (von Lützow et al, 2007;Tiessen and Stewart, 1983).…”

Section: Measurable Poolssupporting

confidence: 84%

“…While this method is relatively simple and parsimonious, it fails to capture plant-microbe feedbacks that regulate N flows. For example, microbiota may alter exoenzyme production or mine SOM (Mooshammer et al, 2014) to access N to meet their needs, and plants may increase exudate production to stimulate these processes (Tian et al, 2019). Failing to represent N dynamics resulting from plant-microbe feedbacks may lead to inaccuracies in model predictions.…”

Section: Introductionmentioning

confidence: 99%

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Simulating measurable ecosystem carbon and nitrogen dynamics with the mechanistically defined MEMS 2.0 model

et al. 2021

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Abstract. For decades, predominant soil biogeochemical models have used conceptual soil organic matter (SOM) pools and only simulated them to a shallow depth in soil. Efforts to overcome these limitations have prompted the development of the new generation SOM models, including MEMS 1.0, which represents measurable biophysical SOM fractions, over the entire root zone, and embodies recent understanding of the processes that govern SOM dynamics. Here we present the result of continued development of the MEMS model, version 2.0. MEMS 2.0 is a full ecosystem model with modules simulating plant growth with above- and belowground inputs, soil water and temperature by layer, decomposition of plant inputs and SOM, and mineralization and immobilization of nitrogen (N). The model simulates two commonly measured SOM pools – particulate and mineral-associated organic matter (POM and MAOM, respectively). We present results of calibration and validation of the model with several grassland sites in the US. MEMS 2.0 generally captured the soil carbon (C) stocks (R2 of 0.89 and 0.6 for calibration and validation, respectively) and their distributions between POM and MAOM throughout the entire soil profile. The simulated soil N matches measurements but with lower accuracy (R2 of 0.73 and 0.31 for calibration and validation of total N in SOM, respectively) than for soil C. Simulated soil water and temperature were compared with measurements, and the accuracy is comparable to the other commonly used models. The seasonal variation in gross primary production (GPP; R2 = 0.83), ecosystem respiration (ER; R2 = 0.89), net ecosystem exchange (NEE; R2 = 0.67), and evapotranspiration (ET; R2 = 0.71) was well captured by the model. We will further develop the model to represent forest and agricultural systems and improve it to incorporate new understanding of SOM decomposition.

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Section: Measurable Poolssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Simulating measurable ecosystem carbon and nitrogen dynamics with the mechanistically defined MEMS 2.0 model

et al. 2021

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“…The roots of Pinus massoniana Lamb could exudate a variety of organic acids, which was conducive to the leaching of base ions in the soils. Under the higher temperature, the forest litter and topsoil organic matter of sites S3 and S4 were easy to decompose [87,88], a thinner (about 1-2 cm) O horizon was found in pedons S3 and S4, and the SOC content in surface horizon was also obviously lower in the two pedons than that in other forest soils at higher elevation (Table 2). The decomposition of these organic matters made more CO 2 dissolve in the soil water, which could accelerate the corrosion of limestone fragments and the leaching of Ca 2+ and Mg 2+ in the soils.…”

Section: Classification and Evolution Determinationsmentioning

confidence: 97%

The Pedogenesis of Soil Derived from Carbonate Rocks along a Climosequence in a Subtropical Mountain, China

Jin

Song

et al. 2021

Forests

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Revealing the pedogenesis of soil on carbonate rocks is a key step in determining the boundaries of soil types along a climosequence. However, related research is lacking for a subtropical mountain. In this study, eight pedons were sampled across an elevation gradient (789–2322 m) having large variation in mean annual precipitation (MAP) (1189–1764 mm) and mean annual temperature (MAT) (5.7–14.9 °C). General processes were performed, including physical, chemical, and morphological characterizations, X-ray diffraction (XRD), total elements’ content, and soil classification of the carbonate rock. In the climo-toposequence, the illite had been transformed into illite-smectite below 1300–1500 m of elevation, 1300–1370 mm of MAP, and above 10.5–11.5 °C of MAT, and into vermiculite above this climate. These findings indicated that the effects of temperature on soil mineral transformation had weakened with the gradual increases in elevation. The pedon at 861 m of elevation, 1206 mm of MAP, and 14.5 °C of MAT, which accounted for the argic horizons, was divided into Argosols after human activities. The finding revealed that changes from forest to cultivated land could potentially accelerate the formation of argic horizons, and it provided a theoretical basis for global carbonate rocks’ weathering conditions and ecological problems in subtropical mountains. When the soils reached approximately 1100–1200 m of elevation, 1250–1300 mm of MAP, and 11.5–13.5 °C of MAT, the argic horizons of the soil could be accounted for, as evolved from the Cambosols in Chinese Soil Taxonomy (CST) (Inceptisols in Soil Taxonomy (ST), Cambisols in the World Reference Base for Soil Resources (WRB)) to the Argosols in CST (Alfisols in ST, Luvisols or Alisols in WRB) under natural vegetation. Therefore, it was indicated that the soil types changed significantly in the CST, ST, and WRB with increases of MAP and decreases of MAT, which provides a reference for determining the boundaries of the soil types along a climosequence in subtropical mountains.

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“…This contrasts with the detritusphere, which has a relatively higher proportion of aromatic N and lignoproteins. Protease enzyme activity has been shown to be enhanced by litter addition [18] and root exudates [19], as well as vary with type of plant litter [20,21]. Obviously, these spatial habitats (rhizosphere and detritosphere) can overlap-as when a root initially grows through bulk soil, or when a growing root begins to age and resemble detritus.…”

Section: Introductionmentioning

confidence: 99%

Expression of macromolecular organic nitrogen degrading enzymes identifies potential mediators of soil organic N availability to an annual grass

Sieradzki

Nuccio

Pett‐Ridge

et al. 2020

Preprint

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Nitrogen is a common limiting nutrient in soil in part because most N is present as macromolecular organic compounds, not directly available to plants. The microbial community present in soil near roots (rhizosphere) is in many ways analogous to the human gut microbiome, transforming nutrients present in organic substrates to forms available to plants through extracellular enzymes. Many recent studies have focused on the genetic potential for nitrogen cycling by bacteria in the rhizosphere, and on measuring inorganic N pools and fluxes. Between those two bodies of knowledge, there is scarce information on functionality of macromolecular nitrogen decomposing bacteria and fungi and how it relates to life stages of the plant. This is particularly important as many soil bacteria identified in community composition studies can be inactive or not viable. Here we use a time-series of metatranscriptomes from rhizosphere and bulk soil bacteria and fungi to follow extracellular protease and chitinase expression during rhizosphere aging. In addition, we explore the effect of adding plant litter as a source of macromolecular carbon and nitrogen. Expression of extracellular proteases increased over time in the absence of litter, more so in the presence of roots, whereas the dominant chitinase (chit1) was upregulated with exposure to litter. Structural groups of proteases were surprisingly dominated by serineproteases, possibly due to the importance of betaproteobacteria and actinobacteria in this grassland soil. Extracellular proteases of betaprotebacterial origin were more highly expressed in the presence of roots, whereas deltaroteobacteria and fungi responded to the presence of litter. We found functional guilds specializing in decomposition of proteins in the rhizosphere, detritusphere and in the vicinity of aging roots. We also identify a guild that appears to specialize in protein decomposition in the presence of roots and litter and increases its activity in aging rhizosphere, which may imply that this guild targets rhizodeposits or the senescing root itself as a protein source. Different temporal patterns of guilds imply that rather than functional redundancy, microbial decomposers operate within distinct niches.

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Priming effect of litter mineralization: the role of root exudate depends on its interactions with litter quality and soil condition

Cited by 46 publications

References 72 publications

Simulating measurable ecosystem carbon and nitrogen dynamics with the mechanistically defined MEMS 2.0 model

Simulating measurable ecosystem carbon and nitrogen dynamics with the mechanistically defined MEMS 2.0 model

The Pedogenesis of Soil Derived from Carbonate Rocks along a Climosequence in a Subtropical Mountain, China

Expression of macromolecular organic nitrogen degrading enzymes identifies potential mediators of soil organic N availability to an annual grass

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