Plant nitrogen dynamics and nitrogen-use strategies under altered nitrogen seasonality and competition.
OBJECTIVE
Numerous studies have examined the effects of climatic factors on the distribution of C(3) and C(4) grasses in various regions throughout the world, but the role of seasonal fluctuations in temperature, precipitation and soil N availability in regulating growth and competition of these two functional types is still not well understood. This report is about the effects of seasonality of soil N availability and competition on plant N dynamics and N-use strategies of one C(3) (Leymus chinensis) and one C(4) (Chloris virgata) grass species.


METHODS
Leymus chinensis and C. virgata, two grass species native to the temperate steppe in northern China, were planted in a monoculture and a mixture under three different N seasonal availabilities: an average model (AM) with N evenly distributed over the growing season; a one-peak model (OM) with more N in summer than in spring and autumn; and a two-peak model (TM) with more N in spring and autumn than in summer.


RESULTS
The results showed that the altered N seasonality changed plant N concentration, with the highest value of L. chinensis under the OM treatment and C. virgata under the TM treatment, respectively. N seasonality also affected plant N content, N productivity and N-resorption efficiency and proficiency in both the C(3) and C(4) species. Interspecific competition influenced N-use and resorption efficiency in both the C(3) and C(4) species, with higher N-use and resorption efficiency in the mixture than in monoculture. The C(4) grass had higher N-use efficiency than the C(3) grass due to its higher N productivity, irrespective of the N treatment or competition.


CONCLUSIONS
The observations suggest that N-use strategies in the C(3) and C(4) species used in the study were closely related to seasonal dynamics of N supply and competition. N seasonality might be involved in the growth and temporal niche separation between C(3) and C(4) species observed in the natural ecosystems.
Yuan
Zhiyou
Z
Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
Liu
Weixing
W
Niu
Shuli
S
Wan
Shiqiang
S
D002244:Carbon / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D006109:Poaceae / Q000254:growth & development / Q000378:metabolism*; D011157:Population Dynamics; D012621:Seasons; D012987:Soil; D013045:Species Specificity
D012987:Soil; D002244:Carbon; D009584:Nitrogen
New Phytol. 1994 Aug;127(4):635-674
33874383
Plant Physiol. 1987 Jul;84(3):959-63
16665551
Oecologia. 1997 May;110(4):550-556
28307249
J Exp Bot. 2007;58(6):1351-63
17322550
Monogr Popul Biol. 1982;17:1-296
7162524
Oecologia. 1976 Mar;23(1):1-12
28309208
Oecologia. 1999 Jan;118(1):50-8
20135160
Oecologia. 2006 Jul;148(4):564-72
16708228
Oecologia. 1998 May;114(4):441-454
28307893
J Exp Bot. 2005 Nov;56(421):2867-76
16203757
Ecology. 2006 Jan;87(1):5-14
16634292
Proc Natl Acad Sci U S A. 2004 Jan 13;101(2):562-7
14701908
Ying Yong Sheng Tai Xue Bao. 2005 Apr;16(4):605-9
16011152
Oecologia. 2001 Jan;126(2):174-181
28547615