This article was downloaded by: [Selcuk Universitesi]On: 21 December 2014, At: 15:40Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK

Acta Agriculturae Scandinavica, Section B — Soil &Plant SciencePublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/sagb20

Nitrification and denitrification in an alpine meadowsoil of the eastern Tibetan PlateauY. Gao a , P. Luo a , N. Wu a & H. Chen aa Chengdu Institute of Biology, Chinese Academy of Sciences , Chengdu, ChinaPublished online: 12 Dec 2007.

To cite this article: Y. Gao , P. Luo , N. Wu & H. Chen (2008) Nitrification and denitrification in an alpine meadow soilof the eastern Tibetan Plateau, Acta Agriculturae Scandinavica, Section B — Soil & Plant Science, 58:1, 93-96, DOI:10.1080/09064710701228320

To link to this article: http://dx.doi.org/10.1080/09064710701228320

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

SHORT COMMUNICATION

Nitrification and denitrification in an alpine meadow soil of the easternTibetan Plateau

Y. GAO, P. LUO, N. WU & H. CHEN

Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China

Introduction

Nitrification and denitrification represent two of the

main biological processes involved in the N cycle,

which contribute to the regulation of NO3� avail-

ability to plants reduction to N2 (Vitousek et al.,

1982; Conen et al., 2000). Moreover, they represent

the main source of the greenhouse gas N2O in

terrestrial ecosystems (Williams et al., 1992). Both

processes are directly limited by substrate availability

(NH4�, NO3

�, organic C) and low temperatures, and

indirectly by water content and soil capacity to retain

water (Granli & Bøkman, 1994). In an alpine

meadow ecosystem on the Tibetan Plateau, being

characterized by an extreme climate with low tem-

peratures and a short vegetation season, inorganic

(available) N is usually present in low concentra-

tions, although alpine meadow soils are noted for

their large quantities of total N; most of this resides

in organic (unavailable) form (Cao & Zhang, 2001).

Therefore, knowledge of N transformation in highly

N limited and fragile alpine ecosystems is necessary

for managing both the N supply to the pasture grass

crop and the potential N losses to the environment.

However, there are no available data on soil nitrifica-

tion and denitrification activities in the region. In

this study we measured the seasonal dynamics of

nitrification and denitrification in an alpine meadow

soil on the eastern Tibetan Plateau.

Materials and methods

The study site is approximately 16 ha and located at

Hongyuan County, Sichuan Province, China

(33803?N, 102836?E, 3462 m a.s.l.). Annual pre-

cipitation averages 752.4 mm, with about 86.4%

received from May to September. Mean annual

temperature is 1.18C and there is no absolute frost-

free period. The highest monthly mean temperature

is 10.98C in July and the lowest is �/10.38C in

January. The soil of the study site is classified as Mat

Cry-gelic Cambisol (Chinese soil taxonomy research

group, 1995). Soil properties are shown in Table I

and were determined with standard methods (Lu,

2000). The dominant species in the study area were:

Roegneria nutans, Deschampsia caespitosa, Clinelymus

nutans, Kobresia setchwanensis, Aster alpinus, Gera-

nium phlzowianum, and Gueldenstaedtia diversifolia.

In June 2005, five 10�/10 m plots were randomly

established for soil and plant sampling on the site.

Soil and plants were sampled in the middle of June,

July, August, and September 2005. At each sam-

pling, 30 intact soil cores (5.6 cm diameter, 4 cm

depth) from the uppermost 5 cm were collected

randomly in each plot. Every five soil cores were

combined as one sample. With each plot, three

samples (15 soil cores) were using to measure gross

rates of nitrification, denitrification and N2O emis-

sions and the subsamples were using to measure soil

moisture, NH4��/N and NO3

��/N. The cores were

cooled with freezer blocks and returned to the

laboratory in insulated boxes for analysis. Above

ground biomass was measured by harvesting three

50�/50 cm quadrats in each plot. All plant samples

were oven-dried for 48 h at 658C and weighed.

Soil temperature was monitored at 0�5 cm soil depth

with specific probes (CS615, 107Temperature

probe, Campbell Scientific Inc.). Soil moisture

was determined gravimetrically. Soil extracts

were analysed for NH4��/N with the potassium

chloride-indiphenol blue colorimetric method, and

Correspondence: N. Wu, Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu 610041, China. Tel: �/86 28 85213782.

Fax: �/86 28 85222753. E-mail: wuning@cib.ac.cn

Acta Agriculturae Scandinavica Section B � Soil and Plant Science, 2008; 58: 93�96

(Received 15 December 2006; accepted 19 January 2007)

ISSN 0906-4710 print/ISSN 1651-1913 online # 2008 Taylor & Francis

DOI: 10.1080/09064710701228320

Dow

nloa

ded

by [

Selc

uk U

nive

rsite

si]

at 1

5:40

21

Dec

embe

r 20

14

NO3��/N with the calcium sulphate-phenol disul-

phonic acid method (Lu, 2000). Gross rates of

nitrification, denitrification and N2O emissions

were determined using the BaPS (Barometric Pro-

cess Separation) technique (Ingwersen et al., 1999).

Five intact soil samples were directly filled into the

BaPS instrument and the system was closed gas-

tight and incubated at the monthly mean soil

temperature (13.3, 16.6, 15.7 and 13.38C for

June, July, August and September, respectively).

The processes for incubating lasted approximately

12 h.

Results and discussion

Soil temperature and moisture showed a similar

variation pattern over the study period, which

increased from June to July and then declined until

September (Figure 1). Above ground biomass in-

creased rapidly beginning in June and reached a

maximum of 539 g m�2 in August, which corre-

sponded well with a previous study in the same area

reported by Wu et al. (2004).

The concentration of NH4��/N in the soil tended

to increase from June to August and decreased until

September, but there was no marked difference

between July (6.40 mg kg�1) and August (6.61 mg

kg�1) (Figure 2). On the contrary, soil NO3��/N

tended to decrease between June and August and

then slight increase in September. In July, soil

temperature and moisture reached a maximum,

which benefits soil N mineralization, and accord-

ingly soil NH4��/N increased (Joergensen, 1990; Fisk

et al., 1998). Also increases in plant biomass could

potentially increase NH4��/N availability in soil

through an increase of root-derived carbon (Lata

et al., 2004). The decreases in soil NO3��/N during

the growing season can be attributed to high rates of

NO3��/N uptake by rapidly growing plants. In

September, plants gradually went into a desiccating

period and plant uptake decreased; accordingly,

slight increases in the accumulation of NO3��/N in

soil occurred. Xu et al. (2004) reported that alpine

plants preferentially use NO3��/N.

Gross rates of nitrification and denitrification

increased rapidly from June to July and then

decreased until September (Figure 3). The concen-

tration of NH4��/N regulates nitrification (Binnerup

et al., 1992). In our study, the seasonal pattern of

NH4��/N was different from that of nitrification,

but it was in accordance with soil temperature and

moisture. Burns et al. (1996) and Maag and

Vinther (1996) found an increase in nitrification

rates with an increase in soil moisture content.

Nitrification in soil is known to increase with soil

water content and then progressively to decrease

with the formation of anaerobic zones (Linn &

Doran, 1984). Although denitrification rate is a

function of NO3��/N and it is common for a higher

Table I. Soil properties at the study site. Values are mean9/S.D., n�/5.

Organic C (g kg�1) Total N (g kg�1) C/N Bulk density (g cm�3) pH

38.69/6.2 3.49/0.5 11.39/0.4 1.29/0.1 6.09/0.1

10

12

14

16

18

20

6 7 8 9

Month

6 7 8 9

Month

Soil

tem

pera

ture

(C

)

25

30

35

40

45

Soil

moi

stur

e (%

)

100

200

300

400

500

600

700

6 7 8 9

Month

Abo

vegr

ound

bio

mas

s

(g m

-2)

Figure 1. Soil temperature, moisture and above ground biomass

on four sampling dates in the study site. Vertical bars indicate

S.D., n�/5.

94 Y. Gao et al.

Dow

nloa

ded

by [

Selc

uk U

nive

rsite

si]

at 1

5:40

21

Dec

embe

r 20

14

denitrification rate to be found where NO3��/N is

higher (Chan & Knowles, 1979), our result showed

a negative response in denitrification to decreasing

NO3��/N from June to July and increasing NO3

��/N

from August to September. This also can be

explained by the variation of soil temperature and

moisture. Hill (1988) reported that positive rela-

tionships between denitrification and soil tempera-

ture are usually shown. Denitrification also can be

enhanced by higher soil moisture content (Elmi

et al., 2003). The results indicated that soil tem-

perature and moisture were the primary factors

limiting nitrification and denitrification in this

alpine meadow soil. N2O flux rate was highest in

July and lowest in September, which is similar to

nitrification and denitrification (Figure 3). N2O is

mainly produced in soils by nitrification and

denitrification (Williams & Hutchinson, 1992).

Denitrification is considered to be the major source

of N2O under most situations, while nitrification is

reported to make a substantial contribution to N2O

emissions under aerobic conditions (Williams et al.,

1998). In this study it is impossible to distinguish

the contribution of nitrification and denitrification

to N2O. Further work is needed to determine which

process between nitrification and denitrification is

actually responsible for N2O emission in this alpine

meadow.

Acknowledgements

This study was financially supported by the Chinese

Academy of Science (KSCXI-07, KSCX2-01-09),

Chinese Science and Technology Ministry

(2001BA606A-05) and Sichuan Science and Tech-

nology Bureau (03ZQ026-043). The authors thank

J. Chen and J. Pei for their help in laboratory work,

and T. Wei for his help on identification of plant

species.

References

Binnerup, S.J., Jensen, K., Revsbech, N.P., Jensen, M.H., &

Sorensen, J. (1992). Denitrification, dissimilatory reduction

of nitrate to ammonium, and nitrification in a bioturbated

estuarine sediment as measured with 15N and microsensor

3

4

5

6

7

8

6 7 8 9

Month

NO

3- -N (

mg

kg-1

)

3

4

5

6

7

8

6 7 8 9

Month

NH

4+-N

(m

g kg

-1)

Figure 2. NO3��/N and NH4

��/N in soil on four sampling dates.

Vertical bars indicate S.D., n�/5.

20

40

60

80

100

120

6 7 8 9

Month

N2O

flu

x ra

te0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

6 7 8 9Month

Den

itri

fica

tion

(mg

N k

g-1d-1

)(m

g N

kg-1

d-1)

(ug

N k

g-1d-1

)

0

5

10

15

20

25

6 7 8 9Month

Gro

ss N

itri

fica

tion

Figure 3. Gross rates of nitrification, denitrification and N2O

flux rate in soil on four sampling dates. Vertical bars indicate S.D.,

n�/5.

Nitrification in Tibetan alpine meadow soils 95

Dow

nloa

ded

by [

Selc

uk U

nive

rsite

si]

at 1

5:40

21

Dec

embe

r 20

14

techniques. Applied and Environmental Microbilogy, 58, 303�313.

Burns, L.C., Stevens, R.J., & Laughlin, R.J. (1996). Production of

nitrite in soil by simultaneous nitrification and denitrifica-

tion. Soil Biology & Biochemistry, 28, 609�616.

Cao, G.M. & Zhang, J.X. (2001). Soil nutrition and substance

cycle of Kobersia meadow. In XM Zhou (Ed.), Chinese

Kobersia Meadow. (pp. 188�216). Beijing: China Science

Press. (in Chinese).

Chan, Y., & Knowles, R. (1979). Measurement of denitrification

in two freshwater sediments by an in situ acetylene inhibition

method. Applied and Environmental Microbiology, 37, 1067�1072.

Chinese soil taxonomy research group. (1995). Chinese Soil

Taxonomy. (pp. 58�147). Beijing: Science Press. (in Chi-

nese).

Conen, F., Dobbie, K.E., & Smith, K.A. (2000). Predicting N2O

emissions from agricultural land through related soil para-

meters. Global Change Biology, 6, 417�426.

Elmi, A.A., Madramootoo, C., Hamel, C., & Liu, A.G. (2003).

Denitrification and nitrous oxide to nitrous oxide plus

dinitrogen rations in the soil profile under three tillage

systems. Biology and Fertility of Soils, 38, 340�348.

Fisk, M.C., Schmidt, S.K., & Seastedt, T.R. (1998). Topographic

patterns of above- and belowground production and nitrogen

cycling in alpine tundra. Ecology, 79, 2253�2266.

Granli, T., & Bøckmann, O.C. (1994). Nitrous oxide from

agriculture. Norwegian Journal of Agricultural Science,

12(Suppl), 128�131.

Hill, A.R. (1988). Factors influencing nitrate depletion in a rural

stream. Hydrobiologia, 160, 111�122.

Ingwersen, J., Butterbach-Bahl, K., Gasche, R., Richter, O., &

Papen, H. (1999). Barometric process separation: new

method for quantifying nitrification, denitrification, and

nitrous oxide sources in soils. Soil Science Society of America

Journal, 63, 117�128.

Joergensen, R.G., Brookes, P.C., & Jenkinson, D.S. (1990).

Survival of the soil microbial biomass at elevated tempera-

tures. Soil Biology & Biochemistry, 22, 1129�1136.

Lata, J.C., Degrange, V., Raynaud, X.R., Maron, P.A., Lensi, R.,

& Abbadie, L. (2004). Grass populations control nitrification

in savanna soils. Functional Ecology, 18, 605�611.

Linn, D.M., & Doran, J.W. (1984). Effect of water-filled pore

space on carbon dioxide and nitrous oxide production in

tilled and non-tilled soils. Soil Science Society of America

Journal, 48, 1267�1272.

Lu, R.K. (2000). Analytic Handbook of Soil Agriculture Chem-

istry. (pp. 146�165). Beijing: Chinese Agricultural Science

and Technology Press, (in Chinese).

Maag, M., & Vinther, F.P. (1996). Nitrous oxide emission by

nitrification and denitrification in different soil types and at

different soil moisture contents and temperatures. Applied

Soil Ecology, 4, 5�14.

Vitousek, P.M., Gosz, J.R., Grier, C.C., Melillo, J.M., & Reiners,

W.A. (1982). A comparative analysis of potential nitrification

and nitrate mobility in forest ecosystems. Ecological Mono-

graphs, 52, 155�177.

Williams, E.J., Hutchinson, G.L., & Fehsenfeld, F.C. (1992).

NOx and N2O emissions from soil. Global Biogeochemical

Cycles, 6, 351�388.

Williams, P.H., Jarvis, S.C., & Dixon, E. (1998). Emission of

nitric oxide and nitrous oxide from soil under field and

laboratory conditions. Soil Biology & Biochemistry, 30, 1885�1893.

Wu, N., Liu, J., & Yan, Z.L. (2004). Grazing intensity on the plant

diversity of alpine meadow in the eastern Tibetan Plateau.

Rangifer, 15, 9�15.

Xu, X.L., Ouyang, H., Pei, Z.Y., & Zhou, C.P. (2004). Long-term

partition of ammonium and nitrate among different compo-

nents in an alpine meadow ecosystem. Acta Botanica Sinica,

46, 279�283.

96 Y. Gao et al.

Dow

nloa

ded

by [

Selc

uk U

nive

rsite

si]

at 1

5:40

21

Dec

embe

r 20

14