التفاصيل البيبلوغرافية
| العنوان: |
Release of non-exchangeable $$ {}^{{{\text{15}}}}{\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ from subgrade, decomposed granite substrates and uptake by non-mycorrhizal and mycorrhizal California native annual grass, Vulpia microstachys. |
| المؤلفون: |
Rider, D. E.1 derider@ucdavis.edu, O'Dell, R. E.1, Claassen, V. P.1 |
| المصدر: |
Plant & Soil. Nov2007, Vol. 300 Issue 1/2, p83-94. 12p. 3 Charts, 5 Graphs. |
| مصطلحات موضوعية: |
*VULPIA, *PLANT biomass, *IGNEOUS rocks, *BIOMASS, *MYCORRHIZAS, *SILICATE minerals, *MICROORGANISMS, *PLANTS |
| مصطلحات جغرافية: |
CALIFORNIA |
| مستخلص: |
Release rates of recently fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ from non-exchangeable interlayer sites in 2:1 silicate minerals were determined for decomposed granite (DG) saprolites from three locations in California, USA. Recently-fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ release from the DG substrate was quantified by extracting diffused $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ with H-resin, as well as a native, annual grass Vulpia microstachys. The $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ release data varied with via the method of extraction, which included H-resin pre-treatments (Na+ or H+) and V. microstachys uptake (mycorrhizal inoculated or uninoculated). After 6 weeks (1008 h), more $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ was recovered from fixed interlayer positions by the H-resins as compared to uptake by V. microstachys. The H+ treated H-resins recovered more released $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ (≈94 mg $${\text{NH}}^{{\text{ + }}}_{{\text{4}}} - {\text{N}}\;{\text{kg}}^{1} $$ or (12%) of total fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ ) in two of the three DG samples as compared to the Na+ treated resins, (which recovered ≈70–78 mg $${\text{NH}}^{{\text{ + }}}_{{\text{4}}} - {\text{N}}\;{\text{kg}}^{{{\text{ - 1}}}} $$ (or 9–10%) of the total fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ ). The V. microstachys assimilated 8–9% of the total fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ with mycorrhizal inoculum as compared to only 2% without a mycorrhizal inoculum, over the same time period. The fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ release kinetics from the H-resin experiments were most accurately described by first order and power function models, and can be characterized as biphasic using a heterogeneous diffusion model. Uptake of both the 15N and ambient, unlabelled N from the soils was closely related to plant biomass. There was no significant difference in percent of N per unit of biomass between the control and mycorrhizal treatments. The findings presented here indicate that observed, long-term $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ release rates from DG in studies utilizing resins, may overestimate the levels of fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ made available to plants and microorganisms. Additionally, the study suggested that mycorrhizae facilitate the acquisition and plant uptake of fixed $$ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $$ , resulting in markedly increased plant biomass production. [ABSTRACT FROM AUTHOR] |
| قاعدة البيانات: |
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