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- Niu, Guoxiang, et al.
(författare)
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Effects of nitrogen and water addition on soil carbon, nitrogen, phosphorus, sulfur, and their stoichiometry along soil profile in a semi-arid steppe
- 2023
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Ingår i: Journal of Soils and Sediments. - 1439-0108. ; 23:9, s. 3298-3309
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Although past studies have found well-constrained soil carbon (C)/nutrient ratios, the effects of increased nitrogen (N) and water inputs on these ratios across soil depths have rarely been assessed in semi-arid grasslands. Methods: In this study, we evaluated the contents of total C, N, phosphorus (P), sulfur (S), and their stoichiometric ratios in a 0–80 cm soil profile following 13 years of successive N (at rates of 5 and 15 g m−2 yearr−1) and water addition (180 mm per growing season) in a semi-arid grassland of the Mongolian Plateau. Results: In the 0–10 cm soil layer, long-term N addition tended to increase total C and N contents but decreased soil total P and S contents compared to the control. The effects of N addition, as observed in 0–10 cm soil, however, were not consistent with that in the deep 10–80 cm soil layers. Water addition increased the total C, N, and P contents across the entire soil profile but increased total S content only in 0–40 cm soil. Moreover, the combined addition of N and water generally had stronger effects on the four elements across the whole soil profile. For the stoichiometry of the four elements, a low rate of N addition (5 g m−2 year−1) increased soil C:N ratios and decreased soil P:S ratios in the 0–80 cm soils, but a high rate of N addition (15 g m−2 year−1) produced the opposite effect. Both N addition rates resulted in an increase in the soil C:P, C:S, N:P, and N:S ratios. Similarly, in plots that received water, water addition alone decreased the soil C:N ratios, while N addition caused higher fluctuations in these six elemental ratios. However, there was no consistent pattern of change in any one ratio, independent of the addition of water, when taking into account N addition rates and soil depths. Conclusion: Our findings showed that the effects of N addition on soil total C, N, P, and S contents and their stoichiometric ratios were highly influenced by the rate of N addition and the depth of soil, and that these effects could be modulated by increasing precipitation. These results need to be carefully considered while managing the ecological environment in semi-arid steppes.
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| 2. |
- Niu, Guoxiang, et al.
(författare)
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Nitrogen addition and mowing had only weak interactive effects on macronutrients in plant-soil systems of a typical steppe in Inner Mongolia
- 2023
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Ingår i: Journal of Environmental Management. - 0301-4797. ; 347
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Tidskriftsartikel (refereegranskat)abstract
- Effective management of macronutrients is pivotal in the optimization and provisioning of ecosystem services in grassland areas, particularly in degraded grasslands. In such instances where mowing and nitrogen (N) fertilization have emerged as predominant management strategies, nutrient management is especially important. However, the precise effects of these concurrent practices on the distribution of macronutrients in plant-soil systems remain unclear. Here we evaluated the effects of 12 years of N addition (2, 10, and 50 g N m−2 year−1) and mowing on the concentrations and pools of six macronutrients (i.e., N; phosphorus P; sulfur S, calcium Ca, magnesium Mg, and potassium K) in three plant components (aboveground plants, litter, and belowground roots) at the community level and in the soil in a typical steppe in Inner Mongolia. Our results revealed that N addition generally raised the N concentration in the entire plant-soil system, regardless of whether plots were mowed. Higher N addition (10 and 50 g N m−2 year−1) also led to higher concentrations of P (+22%, averaging two N addition rates), S (+16%), K (+22%), Ca (+22%), and Mg (+24%) in plants but lower concentrations of these nutrients in the litter. Similar decreases in K (−9%), Ca (−46%), and Mg (−8%) were observed in the roots. In light of the observed increases in vegetation biomass and the lack of pronounced changes in soil bulk density, we found that the ecosystem N enrichment resulted in increased pools of all measured macronutrients in plants, litter, and roots (with the exception of Ca in the roots) while concurrently decreased the pools of P (−20%, averaging two higher N addition rates), S (−12%), K (−10%), Ca (−37%), and Mg (−19%) in the soil, with no obvious effect of the mowing practice. Overall, mowing exhibited a very limited capacity to alleviate the effects of long-term N addition on macronutrients in the plant-soil system. These findings highlight the importance of considering the distribution of macronutrients across distinct plant organs and the dynamic nutrient interplay between plants and soil, particularly in the context of long-term fertilization and mowing practices, when formulating effective grassland management strategies.
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