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- Feng, Zhaozhong, et al.
(författare)
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Constraints to nitrogen acquisition of terrestrial plants under elevated CO2
- 2015
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 21:8, s. 3152-3168
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Tidskriftsartikel (refereegranskat)abstract
- A key part of the uncertainty in terrestrial feedbacks on climate change is related to how and to what extent nitrogen (N) availability constrains the stimulation of terrestrial productivity by elevated CO2 (eCO2), and whether or not this constraint will become stronger over time. We explored the ecosystem-scale relationship between responses of plant productivity and N acquisition to eCO2 in Free-Air CO2 Enrichment (FACE) experiments in grassland, cropland and forest ecosystems and found that: (i) In all three ecosystem types, this relationship was positive, linear, and strong (r2 = 0.68), but exhibited a negative intercept such that plant N acquisition was decreased by 10% when eCO2 caused neutral or modest changes in productivity. Since the ecosystems were markedly N limited, plants with minimal productivity responses to eCO2 likely acquired less N than ambient CO2-grown counterparts because access was decreased, and not because demand was lower. (ii) Plant N concentration was lower under eCO2, and this decrease was independent of the presence or magnitude of eCO2-induced productivity enhancement, refuting the long-held hypothesis that this effect results from growth dilution. (iii) Effects of eCO2 on productivity and N acquisition did not diminish over time, while the typical eCO2-induced decrease in plant N concentration did. Our results suggest that, at the decennial time scale covered by FACE studies, N limitation of eCO2-induced terrestrial productivity enhancement is associated with negative effects of eCO2 on plant N acquisition rather than with growth dilution of plant N or processes leading to progressive N limitation.
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| 2. |
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| 3. |
- Schmidt, Hans Peter, et al.
(författare)
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Fourfold Increase in Pumpkin Yield in Response to Low-Dosage Root Zone Application of Urine-Enhanced Biochar to a Fertile Tropical Soil
- 2015
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Ingår i: Agriculture (Basel). - : MDPI AG. - 2077-0472. ; 5:3, s. 723-741
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Tidskriftsartikel (refereegranskat)abstract
- A widely abundant and invasive forest shrub, Eupatorium adenophorum, was pyrolyzed in a cost- efficient flame curtain kiln to produce biochar. The resulting biochar fulfilled all the requirements for premium quality, according to the European Biochar Certificate. The biochar was either applied alone or mixed with fresh cow urine ( 1: 1 volume) to test its capacity to serve as slow release fertilizer in a pumpkin field trial in Nepal. Treatments included cow- manure compost combined with ( i) urine- only; ( ii) biochar- only or ( iii) urine- loaded biochar. All materials were applied directly to the root zone at a biochar dry matter content of 750 kg . ha- 1 before seeding. The urine- biochar treatment led to a pumpkin yield of 82.6 t . ha- 1, an increase of more than 300% compared with the treatment where only urine was applied, and an 85% increase compared with the biochar- only treatment. This study showed for the first time that a low- dosage root zone application of urine- enhanced biochar led to substantial yield increases in a fertile silt loam soil. This was tentatively explained by the formation of organic coating of inner pore biochar surfaces by the urine impregnation, which improved the capacity of the biochar to capture and exchange plant nutrients.
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| 4. |
- Seibert, Ruben, et al.
(författare)
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Plant Functional Types Differ in Their Long-term Nutrient Response to eCO(2) in an Extensive Grassland
- 2022
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Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 25, s. 1084-95
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Tidskriftsartikel (refereegranskat)abstract
- Increasing atmospheric CO2 enhances plant biomass production and may thereby change nutrient concentrations in plant tissues. The objective of this study was to identify the effect of elevated atmospheric CO2 concentrations on nutrient concentrations of grassland biomass that have been grown for 16 years (1998–2013). The grassland biomass grown at the extensively managed Giessen FACE experiment, fumigated with ambient and elevated CO2 (aCO2; eCO2; +20%) was harvested twice annually. Concentrations of C, N, P, K, Ca, Mg, Mn, Fe, Cu and Zn were determined separately for grasses, forbs and legumes. Under eCO2, the concentration of N was reduced in grasses, Ca was reduced in grasses and forbs, P was reduced in grasses but increased in legumes, Mg concentration was reduced in grasses, forbs and legumes and K was reduced in grasses but increased in forbs. The nutrient yield (in g nutrient yield of an element per m-2) of most elements indicated negative yield responses at a zero biomass response to eCO2 for grasses. K and Zn nutrient yields responded positively to eCO2 in forbs and Mn and Fe responded positively in forbs and legumes. The results suggest that under eCO2 the nutrient concentrations were not diluted by the CO2 fertilization effect. Rather, altered plant nutrient acquisitions via changed physiological mechanisms prevail for increased C assimilation under eCO2. Furthermore, other factors such as water or nutrient availability affected plant nutrient concentrations under eCO2.
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