环青海湖地区天然草地和退耕恢复草地植物群落生物量对氮、磷添加的响应

doi:10.17521/cjpe.2016.0048

摘要/Abstract

摘要：

植物群落生物量反映了植被的初级生产能力, 是陆地生态系统碳(C)输入的最主要来源, 往往受到自然界中氮(N)、磷(P)元素供应的限制。该试验以青藏高原环青海湖地区的高寒草原为研究对象, 探讨了天然草地和退耕恢复草地植被群落生物量对N (10 g·m^-2)、P (5 g·m^-2)养分添加的响应。N、P添加显著增加了天然草地禾草的生物量, 进而促使地上总生物量显著提高。退耕恢复草地禾草和杂类草的生物量对N添加均有一致的正响应, 从而促使地上总生物量显著增加174%, 群落地上和地下总生物量显著增加34%; 而P添加对恢复草地生物量各项参数均无显著影响。回归分析显示: 天然草地植物群落地上生物量随土壤中NO₃^--N含量的增加而增加(p < 0.05), 退耕恢复草地植被地上、地下和总生物量均与土壤NO₃^--N含量显著正相关(p < 0.01), 说明环湖地区高寒草原植物生长主要受N供应的限制, P的限制作用随土地利用方式的转变和群落演替阶段的不同而变化; 相比天然草地, 恢复草地在现阶段植被初级生产力受N的限制作用更强烈, 土壤中可利用N含量是限制其植被自然恢复和重建的关键因子。

关键词: 高寒草原, 植物群落生物量, 氮添加, 磷添加, 退耕恢复草地, 青海湖流域

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.

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

李春丽, 李奇, 赵亮, 赵新全. 环青海湖地区天然草地和退耕恢复草地植物群落生物量对氮、磷添加的响应. 植物生态学报, 2016, 40(10): 1015-1027. DOI: 10.17521/cjpe.2016.0048

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. Chinese Journal of Plant Ecology, 2016, 40(10): 1015-1027. DOI: 10.17521/cjpe.2016.0048

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https://www.plant-ecology.com/CN/Y2016/V40/I10/1015

图/表 8

表1 环青海湖地区土壤理化性质(平均值±标准误差, n = 6)

Table 1 Chemical and physical properties of the soil around Qinghai Lake Basin (mean ± SE, n = 6)

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

图1 N、P添加对天然草地(NG)和退耕恢复草地(RG) NO3--N (A, C)和速效磷(B, D)含量的影响(平均值±标准误差)。***, p < 0.001。

Fig. 1 Effects of nitrogen and phosphorus additions on the contents of soil NO3--N (A, C) and available phosphorus (B, D) in the natural alpine grassland (NG) and restored grassland (RG) (mean ± SE). ***, p < 0.001.

图2 N、P添加对天然草地(A)与退耕恢复草地(B)禾草和杂类草地上生物量的影响(平均值±标准误差)。*, p < 0.05; **, p < 0.01; ***, p < 0.001。

Fig. 2 Effects of nitrogen and phosphorus additions on aboveground biomass of grass and forb in the natural grassland (A) and restored grassland (B) (mean ± SE). *, p < 0.05; **, p < 0.01; ***, p < 0.001.

表2 氮、磷添加对群落生物量(g·m-2·a-1)和不同功能群植物比例(%)影响的双因素方差分析

Table 2 Two-way ANOVA of the effects of nitrogen and phosphorous additions on plant community biomass and percentage contribution of different functional groups

	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

图3 N、P添加对天然草地地上生物量(A)和N添加对退耕恢复草地地上生物量(AGB)和总生物量(TB) (B)的影响(平均值±标准误差)。*, p < 0.05; **, p < 0.01; ***, p < 0.001。

Fig. 3 Effects of nitrogen and phosphorus additions on aboveground biomass in the natural grassland (A), and effects of nitrogen addition on aboveground biomass (AGB) and total biomass (TB) (B) in the restored grassland (mean ± SE). *, p < 0.05; **, p < 0.01; ***, p < 0.001.

图4 天然草地(NG)与退耕恢复草地(RG)禾草生物量(A)、杂类草生物量(B)、地上生物量(C)、地下生物量(D)和总生物量(C, D)在对照和N添加处理下的比较(平均值±标准误差)。*, p < 0.05; **, p < 0.01; ***, p < 0.001。

Fig. 4 Comparisons of grass biomass (A), forb biomass (B), aboveground biomass (C), belowground biomass (D) and total biomass (C, D) between natural grassland (NG) and restored grassland (RG) under control and N addition treatments (mean ± SE). *, p < 0.05; **, p < 0.01; ***, p < 0.001.

图5 天然草地地上生物量、禾草生物量与土壤NO3--N (A, C)和速效磷(B, D)含量的关系。

Fig. 5 Relationships between plant biomass and soil NO3--N (A, C), plant biomass and soil available phosphorus (B, D) in the natural grassland.

图6 退耕恢复草地群落生物量与土壤NO3--N含量的关系。

Fig. 6 Relationships between plant biomass and soil NO3--N in restored grassland.

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