Responses of plant community biomass to nitrogen and phosphorus additions in natural and restored grasslands around Qinghai Lake Basin

doi:10.17521/cjpe.2016.0048

Abstract

Abstract:

Aims Plant biomass reflects the primary productivity of community vegetation, and is the main resource of carbon input in the terrestrial ecosystem. It is usually limited by nitrogen (N) and phosphorus (P) availability in the soil. Alpine grassland around Qinghai Lake Basin has experienced extensive land-use changes due to the cultivation of native grassland and vegetation recovery on cropped land. In this experiment, two grassland types were chosen, natural alpine grassland (NG) and its adjacent restored grassland (RG), to determine the responses of plant community biomass to N and P additions with different land-use. Methods NH₄NO₃and Ca(H₂PO₄)₂·H₂O were added in a completely randomized block design, with medium levels of 10 g N·m^-2 and 5 g P·m^-2. Soil NO₃^--N and available P contents, and the plant community biomass were measured in the two grasslands. Two-way ANOVA was used to determine the effects of nutrient additions on all measured indicators, and regression analysis was used to analyze the correlations between plant biomass and soil NO₃^--N and available P contents.Important findings Results showed: (1) N and P additions both increased grass biomass in the NG, and significantly elevated the total aboveground biomass, with the promoting effect of N addition higher than that of P addition; N addition significantly increased both grass and forb biomass in the RG, and markedly promoted the total aboveground biomass, while P addition had no effects on the functional groups and total aboveground biomass (p > 0.05). (2) N and P additions both had no effects on the belowground and total biomass in the NG, whereas N addition significantly increased the total biomass by 34% in the RG, which suggested that the effect of N limitation on the vegetation primary productivity was stronger in the RG at present stage. (3) The aboveground biomass in the NG increased with soil NO₃^--N content (p < 0.05), and the above- and below-ground as well as the total biomass were all positively correlated with soil NO₃^--N content in the RG (p < 0.01). These results indicated that the plant growth in alpine grassland around Qinghai Lake Basin was prone to N limitation, and the effect of P limitation changed with land-use. Soil available N might be the key limiting factor for vegetation restoration and reconstruction in the RG. The “Grain for Green” project (the land-use policy) and atmospheric N deposition are benefiting both plant growth and C accumulation in the alpine grassland ecosystem around Qinghai Lake Basin.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201610005

Key words: alpine grassland, plant community biomass, nitrogen addition, phosphorus addition, restored grassland, Qinghai Lake Basin

Chun-Li LI, Qi LI, Liang ZHAO, Xin-Quan ZHAO. Responses of plant community biomass to nitrogen and phosphorus additions in natural and restored grasslands around Qinghai Lake Basin[J]. Chin J Plant Ecol, 2016, 40(10): 1015-1027.

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土壤深度 Soil depth (cm)	草地类型 Grassland type	pH	容重 Bulk density (g·m^-3)	土壤有机碳 Soil organic carbon (g·kg^-1)	全氮 Total nitrogen (g·kg^-1)	全磷 Total phosphorus (g·kg^-1)
0-10	NG	8.02 ± 0.03	0.73 ± 0.02	54.84 ± 1.52	5.76 ± 0.09	0.74 ± 0.02
0-10	RG	8.34 ± 0.01	0.75 ± 0.02	31.74 ± 0.95	2.94 ± 0.06	0.80 ± 0.02
10-20	NG	8.33 ± 0.03	0.80 ± 0.05	41.04 ± 1.19	4.27 ± 0.15	0.71 ± 0.01
10-20	RG	8.51 ± 0.02	0.85 ± 0.05	26.23 ± 0.61	2.82 ± 0.07	0.61 ± 0.02
20-30	NG	8.42 ± 0.02	0.85 ± 0.03	29.44 ± 1.54	3.06 ± 0.13	0.62 ± 0.04
20-30	RG	8.65 ± 0.02	1.07 ± 0.04	24.21 ± 1.59	2.18 ± 0.08	0.63 ± 0.03

土壤深度 Soil depth (cm)	草地类型 Grassland type	pH	容重 Bulk density (g·m^-3)	土壤有机碳 Soil organic carbon (g·kg^-1)	全氮 Total nitrogen (g·kg^-1)	全磷 Total phosphorus (g·kg^-1)
0-10	NG	8.02 ± 0.03	0.73 ± 0.02	54.84 ± 1.52	5.76 ± 0.09	0.74 ± 0.02
0-10	RG	8.34 ± 0.01	0.75 ± 0.02	31.74 ± 0.95	2.94 ± 0.06	0.80 ± 0.02
10-20	NG	8.33 ± 0.03	0.80 ± 0.05	41.04 ± 1.19	4.27 ± 0.15	0.71 ± 0.01
10-20	RG	8.51 ± 0.02	0.85 ± 0.05	26.23 ± 0.61	2.82 ± 0.07	0.61 ± 0.02
20-30	NG	8.42 ± 0.02	0.85 ± 0.03	29.44 ± 1.54	3.06 ± 0.13	0.62 ± 0.04
20-30	RG	8.65 ± 0.02	1.07 ± 0.04	24.21 ± 1.59	2.18 ± 0.08	0.63 ± 0.03

	草地类型 Grassland type	氮添加 N addition		磷添加 P addition		氮磷交互作用 N × P interaction
	草地类型 Grassland type	F	p	F	p	F	p
禾草生物量 Grass biomass	NG	25.350	< 0.001	9.036	0.007	0.168	0.686
禾草生物量 Grass biomass	RG	81.215	< 0.001	0.044	0.836	0.149	0.704
禾草百分比 Grass percentage	NG	3.080	0.095	2.339	0.142	0.001	0.978
禾草百分比 Grass percentage	RG	1.098	0.307	0.665	0.424	0.999	0.329
杂类草生物量 Forb biomass	NG	0.196	0.663	0.215	0.648	0.007	0.934
杂类草生物量 Forb biomass	RG	4.908	0.039	2.072	0.165	2.792	0.110
杂类草百分比 Forb percentage	NG	3.080	0.095	2.339	0.142	0.001	0.978
杂类草百分比 Forb percentage	RG	1.098	0.307	0.665	0.424	0.999	0.329
地上生物量 Aboveground biomass	NG	28.837	< 0.001	7.113	0.015	0.685	0.418
地上生物量 Aboveground biomass	RG	174.985	< 0.001	0.089	0.769	0.002	0.969
地下生物量 Belowground biomass	NG	0.636	0.435	0.526	0.477	0.205	0.655
地下生物量 Belowground biomass	RG	1.282	0.271	0.000	0.989	0.031	0.862
总生物量 Total biomass	NG	1.117	0.303	0.725	0.404	0.241	0.629
总生物量 Total biomass	RG	14.692	< 0.01	0.004	0.953	0.038	0.847

	草地类型 Grassland type	氮添加 N addition		磷添加 P addition		氮磷交互作用 N × P interaction
	草地类型 Grassland type	F	p	F	p	F	p
禾草生物量 Grass biomass	NG	25.350	< 0.001	9.036	0.007	0.168	0.686
禾草生物量 Grass biomass	RG	81.215	< 0.001	0.044	0.836	0.149	0.704
禾草百分比 Grass percentage	NG	3.080	0.095	2.339	0.142	0.001	0.978
禾草百分比 Grass percentage	RG	1.098	0.307	0.665	0.424	0.999	0.329
杂类草生物量 Forb biomass	NG	0.196	0.663	0.215	0.648	0.007	0.934
杂类草生物量 Forb biomass	RG	4.908	0.039	2.072	0.165	2.792	0.110
杂类草百分比 Forb percentage	NG	3.080	0.095	2.339	0.142	0.001	0.978
杂类草百分比 Forb percentage	RG	1.098	0.307	0.665	0.424	0.999	0.329
地上生物量 Aboveground biomass	NG	28.837	< 0.001	7.113	0.015	0.685	0.418
地上生物量 Aboveground biomass	RG	174.985	< 0.001	0.089	0.769	0.002	0.969
地下生物量 Belowground biomass	NG	0.636	0.435	0.526	0.477	0.205	0.655
地下生物量 Belowground biomass	RG	1.282	0.271	0.000	0.989	0.031	0.862
总生物量 Total biomass	NG	1.117	0.303	0.725	0.404	0.241	0.629
总生物量 Total biomass	RG	14.692	< 0.01	0.004	0.953	0.038	0.847