Responses of plant community biomass to nitrogen and phosphorus additions in an alpine meadow on the Qinghai-Xizang Plateau

doi:10.3724/SP.J.1258.2014.00014

Abstract

Abstract:

Aims Rising soil temperature under the warming process stimulates microbial activity in soils on the Qinghai- Xizang Plateau. Moreover, the eastern edge of Qinghai-Xizang Plateau has been experiencing distinct atmospheric nitrogen deposition with an increasing trend. All of these have led to an increase in the available nutrients in soils. This study was aimed to determine the responses of carbon fixation in the alpine meadow to nitrogen and phosphorus additions on the Qinghai-Xizang Plateau.
Methods The study was conducted in an alpine meadow ecosystem at the Haibei National Field Research Station of Alpine Grassland Ecosystem, Northwest Institute of Plateau Biology, Chinese Academy of Sciences. Four treatments were set up in 2009, including control, nitrogen addition only (N), phosphorus addition only (P), and combined nitrogen and phosphorus additions (NP). Nutrients were added in June or July each year. The aboveground biomass of functional groups and the above- and belowground biomass of plant communities were measured by harvesting in 2012.
Important findings (1) N and P additions increased the aboveground biomass of grass, and the proportion of grass biomass in the community, but decreased the proportion of forb biomass in the community. Only P addition decreased the aboveground biomass of sedge, and the proportion of sedge biomass in the community. (2) N and P additions increased the aboveground biomass by 24% and 52%, respectively, compared with the control. (3) N addition had no effect on the belowground biomass, whereas P addition slightly increased the belowground biomass. (4) N addition had no effect on the total biomass, whereas P addition significantly increased the total biomass. Therefore, N and P additions could relieve the nutrient limitation and stimulate plant growth. Furthermore, the results suggest that the Qinghai-Xizang Plateau could be more limited by P than N on plant growth.

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Key words: alpine meadow, biomass, functional groups, nitrogen addition, phosphorus addition, Qinghai-Xizang Plateau

YANG Xiao-Xia, REN Fei, ZHOU Hua-Kun, HE Jin-Sheng. Responses of plant community biomass to nitrogen and phosphorus additions in an alpine meadow on the Qinghai-Xizang Plateau[J]. Chin J Plant Ecol, 2014, 38(2): 159-166.

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Figures/Tables 6

Fig. 1 Effects of nitrogen addition (A) and phosphorus addition (B) on aboveground biomass of three different functional groups (mean ± SE). **, p < 0.01; ***, p < 0.001.

Fig. 2 Effects of nitrogen addition (A) and phosphorus addition (B) on the proportions of the three different functional groups aboveground biomass of the community biomass (mean ± SE). *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Table 1 Two way ANOVA of the effects of nitrogen and phosphorous additions on aboveground biomass of different functional groups and their proportions of the community biomass

	氮添加 N addition		磷添加 P addition		氮磷交互作用 N × P interaction
	F	p	F	p	F	p
莎草生物量 Sedge biomass	0.28	0.611	15.60	0.006	2.75	0.141
莎草生物量 Sedge biomass (%)	0.01	0.910	17.53	0.004	0.79	0.403
禾本生物量 Grass biomass	15.24	0.006	39.95	<0.001	0.80	0.400
禾本生物量 Grass biomass (%)	12.78	0.009	19.64	0.003	0.19	0.676
杂类草生物量 Forb biomass	1.91	0.210	0.13	0.730	0.97	0.358
杂类草生物量 Forb biomass (%)	9.91	0.016	9.34	0.018	0.04	0.844

Table 2 Two-way ANOVA of the effects of nitrogen and phosphorus additions on aboveground biomass (AGB), belowground biomass (BGB), total biomass (TB) and the ratio of belowground biomass to aboveground biomass (R/S)

	氮添加 N addition		磷添加 P addition		氮磷交互作用 N × P interaction
	F	p	F	p	F	p
AGB (g·m^-2·a^-1)	13.61	0.008	66.38	< 0.001	0.95	0.363
BGB (g·m^-2·a^-1)	1.80	0.216	4.82	0.060	0.02	0.880
TB (g·m^-2·a^-1)	0.002	0.969	15.22	0.008	1.54	0.260
R/S	3.50	0.086	1.24	0.309	0.07	0.806

Fig. 3 Effects of nitrogen and phosphorus additions on aboveground biomass (A), belowground biomass (B) and total biomass (C) (mean ± SE). **, p < 0.01; ***, p < 0.001.

Table 3 Aboveground biomass (AGB), belowground biomass (BGB) and total biomass (TB) carbon stock under different treatments (mean ± SE)

	对照 CK	氮添加 N addition	磷添加 P addition	氮磷添加 N, P addition
AGB (g C·m^-2)	146.5 ± 14.0^a	204.8 ± 7.8^b	250.9 ± 12.7^c	281.5 ± 7.9^d
BGB (g C·m^-2)	558.0 ± 68.4^a	510.5 ± 36.8^a	709.1 ± 49.5^b	598.8 ± 101.3^a
TB (g C·m^-2)	704.6 ± 64.3^a	715.3 ± 40.9^a	960.0 ± 41.8^b	880.3 ± 95.8^ab

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