Differential response of microbial respiration to supplied nitrogen forms in 3 contrasting alpine meadow soils on the Tibetan Plateau

Zeng, Xiaoyang

doi:10.1590/1678-4499.139

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SOIL AND PLANT NUTRITION • Bragantia 76 (3) • Jul-Sept 2017 • https://doi.org/10.1590/1678-4499.139 copy

Differential response of microbial respiration to supplied nitrogen forms in 3 contrasting alpine meadow soils on the Tibetan Plateau

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

An incubation experiment was conducted to examine the effects of nitrogen (N) applications in different forms (NH₄NO₃, NH₄Cl, and KNO₃) on microbial respiration considering 3 different alpine meadow soils (C poor soil, pH = 8.1, 1.6% C; C moderate soil, pH = 6.0, 5.0% C; C rich soil, pH = 7.1, 7.4% C) in the Tibetan Plateau. The addition of NH₄NO₃ and NH₄Cl increased the microbial respiration in C poor soil, but KNO₃ had no effect. The inorganic N forms had no effects on C rich soil, but decreased microbial respiration in C moderate soil. Soil microbial respiration levels across the different types were ordered as follows: C poor soil < C rich soil < C moderate soil, regardless of N addition. These results suggest that the effect of N on microbial respiration in alpine meadow soils is more dependent on the initial soil pH than on soil C availability.

Key words
C cycling; microbial activity; N deposition; soil properties; high-altitude region

	C poor soil	C moderate soil	C rich soil
Location	lat 34°43′N, long 92°53′E	lat 32°50′E, long 102°36′E	lat 37°37′N, long 101°19′E
Altitude (m)	4,754	3,462	3,240
Mean annual air temperature (°C)	-5.3	1.1	-1.7
Mean annual precipitation (mm)	269.7	752.4	560.5
Dominant species	Kobresia pygmaea	Kobresia setchwanensis	Kobresia humilis
Organic carbon (g∙kg^-1)	15.71 ± 0.74	50.24 ± 2.63	74.33 ± 3.71
Total N (g∙kg^-1)	1.53 ± 0.05	4.28 ± 0.18	6.89 ± 0.40
C/N	10.27 ± 0.72	11.75 ± 0.17	10.82 ± 0.89
Dissolved organic carbon (mg∙kg^-1)	16.46 ± 1.21	33.28 ± 2.07	56.29 ± 3.69
Available N (mgkg^-1)	141.28 ± 3.36	378.40 ± 26.40	508.14 ± 30.55
Total P (g∙kg^-1)	0.65 ± 0.03	1.31 ± 0.03	1.15 ± 0.11
Available P (mgkg^-1)	5.48 ± 0.69	15.87 ± 0.71	14.75 ± 0.98
pH (H₂O)	8.06 ± 0.06	6.02 ± 0.05	7.14 ± 0.08

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