Dynamics of soil soluble nitrogen and plant productivity in artificial pastures on the Qingzang Plateau

doi:10.17521/cjpe.2020.0279

Abstract

Abstract:

Aims Nitrogen is the most limiting factor to artificial pastures. It is distributed unevenly in time and space, and has different forms, which are correlated with cultivation approaches and above-ground net primary productivity (ANPP). This study investigated the dynamics of soil nitrogen and productivity in artificial pastures of Bromus inermis, Elymus sibiricus, E. nutans, Festuca ryloviana, F. sinensis, Poa pratensis var. anceps ‘Qinghai’, P. crymophila and Puccinellia tenuiflora in pure species cultivations in the Tongde farm of Qinghai Province. The dynamics of soil soluble nitrogen pools in each artificial pasture type and their relationships with ANPP were examined.
Methods The pastures were planted in 2013 without fertilizer application, and mowed to the level with 5 cm stubble in mid-September every year. The soil ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), soluble organic nitrogen (SON) and soluble total nitrogen (STN) content were measured during growing seasons. ANPP was determined in September each year.
Important findings (1) The average ANPP across the eight pasture types ranged between 329.67-794.67 g·m ^-2, with the ANPP of 794.67 g·m ^-2 for the E. nutans significantly higher than other pasture types. (2) From the second to fourth year following planting, the content of soil NO₃ ^--N, SON and STN significantly decreased, but that of the NH₄⁺-N significantly increased. (3) SON accounted for the highest proportion of STN, varying between 45.11%-88.76% in the 0-10 cm soil layer and 47.75%-88.18% in the 10-20 cm soil layer, followed by NO₃^--N in ranges of 5.81%-34.85% (0-10 cm) and 6.08%-40.42% (10-20 cm), respectively; NH₄⁺-N had the least proportion at 3.41%-22.18% (0-10 cm) and 3.09%-19.56% (10-20 cm), respectively. (4) The non-metric multidimensional scale analysis (NMDS) shows that the temporal effect on soil soluble nitrogen content by different pasture types diverged for the 0-10 cm soil layer, but converged for the 10-20 cm soil layer, and that the effect of pasture types on soil soluble nitrogen content was related to soil depth. (5) Soil SON and STN contents were positively correlated with ANPP, and negatively with inorganic nitrogen (IN) content. In summary, nitrogen fertilizer application is one of the key factors for maintaining the productivity of artificial pasture from three to four years. The above results provide a scientific basis for a more in-depth understanding of the dynamics of soil soluble nitrogen and the maintenance of productivity and stability of artificial pastures on the Qingzang Plateau.

Key words: artificial pasture, soil soluble nitrogen pool, soil inorganic nitrogen pool, Qingzang Plateau

LIU Pan, WANG Wen-Ying, ZHOU Hua-Kun, MAO Xu-Feng, LIU Yan-Fang. Dynamics of soil soluble nitrogen and plant productivity in artificial pastures on the Qingzang Plateau[J]. Chin J Plant Ecol, 2021, 45(5): 562-572.

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Figures/Tables 6

References 37

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处理 Treatment	年龄Age (a)	0-10 cm土层 0-10 cm soil layer				10-20 cm土层 10-20 cm soil layer
处理 Treatment	年龄Age (a)	铵态氮/ 可溶性总氮 NH₄⁺-N/STN (%)	硝态氮/ 可溶性总氮 NO₃^--N/STN (%)	无机氮/ 可溶性总氮 IN/STN (%)	可溶性有机氮/可溶性总氮 SON/STN (%)	铵态氮/ 可溶性总氮 NH₄⁺-N/STN (%)	硝态氮/ 可溶性总氮 NO₃^--N/STN (%)	无机氮/ 可溶性总氮 IN/STN (%)	可溶性有机氮/可溶性总氮 SON/STN (%)
无芒雀麦 Bromus inermis	2	8.53	18.83	27.36	72.64	10.62	34.97	45.59	54.41
	3	9.22	14.06	23.28	76.72	7.76	10.95	18.71	81.29
	4	21.31	29.70	51.01	48.99	16.16	32.65	48.80	51.20
老芒麦 Elymus sibiricus	2	4.11	25.46	29.58	70.42	4.02	30.94	34.96	65.04
	3	8.41	11.57	19.98	80.02	7.88	14.37	22.25	77.75
	4	17.34	34.52	51.85	48.15	18.68	33.57	52.25	47.75
垂穗披碱草 E. nutans	2	4.76	22.10	26.86	73.14	5.59	31.63	37.22	62.78
	3	7.90	15.45	23.35	76.65	4.99	8.68	13.66	86.34
	4	21.61	33.28	54.89	45.11	17.63	26.96	44.59	55.41
西北羊茅 Festuca ryloviana	2	3.41	21.63	25.03	74.97	3.69	34.93	38.61	61.39
	3	7.30	12.14	19.44	80.56	4.80	10.28	15.08	84.92
	4	22.18	30.79	52.98	47.02	19.56	25.19	44.75	55.25
中华羊茅 F. sinensis	2	5.91	28.37	34.28	65.72	4.87	33.10	37.97	62.03
	3	5.99	16.15	22.14	77.86	5.49	11.04	16.53	83.47
	4	20.13	34.85	54.98	45.02	15.41	30.43	45.85	54.15
青海扁茎早熟禾 Poa pratensis var. anceps ‘Qinghai’	2	4.06	18.54	22.59	77.41	3.09	40.42	43.51	56.49
	3	5.42	5.81	11.24	88.76	8.43	12.23	20.66	79.34
	4	20.12	29.03	49.16	50.84	17.48	30.74	48.23	51.77
星星草 Puccinellia tenuiflora	2	4.33	27.73	32.06	67.94	4.32	33.36	37.68	62.32
	3	8.18	20.37	28.55	71.45	5.74	6.08	11.82	88.18
	4	21.18	32.90	54.09	45.91	18.33	29.73	48.07	51.93
冷地早熟禾 Poa crymophila	2	5.07	29.05	34.12	65.88	4.19	40.99	45.18	54.82
	3	7.70	8.96	16.65	83.35	3.29	14.35	17.65	82.35
	4	18.46	30.38	48.84	51.16	18.36	29.47	47.83	52.17

处理 Treatment	年龄Age (a)	0-10 cm土层 0-10 cm soil layer				10-20 cm土层 10-20 cm soil layer
处理 Treatment	年龄Age (a)	铵态氮/ 可溶性总氮 NH₄⁺-N/STN (%)	硝态氮/ 可溶性总氮 NO₃^--N/STN (%)	无机氮/ 可溶性总氮 IN/STN (%)	可溶性有机氮/可溶性总氮 SON/STN (%)	铵态氮/ 可溶性总氮 NH₄⁺-N/STN (%)	硝态氮/ 可溶性总氮 NO₃^--N/STN (%)	无机氮/ 可溶性总氮 IN/STN (%)	可溶性有机氮/可溶性总氮 SON/STN (%)
无芒雀麦 Bromus inermis	2	8.53	18.83	27.36	72.64	10.62	34.97	45.59	54.41
	3	9.22	14.06	23.28	76.72	7.76	10.95	18.71	81.29
	4	21.31	29.70	51.01	48.99	16.16	32.65	48.80	51.20
老芒麦 Elymus sibiricus	2	4.11	25.46	29.58	70.42	4.02	30.94	34.96	65.04
	3	8.41	11.57	19.98	80.02	7.88	14.37	22.25	77.75
	4	17.34	34.52	51.85	48.15	18.68	33.57	52.25	47.75
垂穗披碱草 E. nutans	2	4.76	22.10	26.86	73.14	5.59	31.63	37.22	62.78
	3	7.90	15.45	23.35	76.65	4.99	8.68	13.66	86.34
	4	21.61	33.28	54.89	45.11	17.63	26.96	44.59	55.41
西北羊茅 Festuca ryloviana	2	3.41	21.63	25.03	74.97	3.69	34.93	38.61	61.39
	3	7.30	12.14	19.44	80.56	4.80	10.28	15.08	84.92
	4	22.18	30.79	52.98	47.02	19.56	25.19	44.75	55.25
中华羊茅 F. sinensis	2	5.91	28.37	34.28	65.72	4.87	33.10	37.97	62.03
	3	5.99	16.15	22.14	77.86	5.49	11.04	16.53	83.47
	4	20.13	34.85	54.98	45.02	15.41	30.43	45.85	54.15
青海扁茎早熟禾 Poa pratensis var. anceps ‘Qinghai’	2	4.06	18.54	22.59	77.41	3.09	40.42	43.51	56.49
	3	5.42	5.81	11.24	88.76	8.43	12.23	20.66	79.34
	4	20.12	29.03	49.16	50.84	17.48	30.74	48.23	51.77
星星草 Puccinellia tenuiflora	2	4.33	27.73	32.06	67.94	4.32	33.36	37.68	62.32
	3	8.18	20.37	28.55	71.45	5.74	6.08	11.82	88.18
	4	21.18	32.90	54.09	45.91	18.33	29.73	48.07	51.93
冷地早熟禾 Poa crymophila	2	5.07	29.05	34.12	65.88	4.19	40.99	45.18	54.82
	3	7.70	8.96	16.65	83.35	3.29	14.35	17.65	82.35
	4	18.46	30.38	48.84	51.16	18.36	29.47	47.83	52.17

处理 Treatment	指标 Variable	0-10 cm	10-20 cm
无芒雀麦 Bromus inermis	NH₄⁺-N	-0.485	-0.170
	NO₃^--N	0.010	0.068
	SON	0.392	0.676^*
	STN	0.403	0.681^*
老芒麦 Elymus sibiricus	NH₄⁺-N	-0.259	-0.444
	NO₃^--N	-0.328	0.067
	SON	0.347	0.459
	STN	0.231	0.328
垂穗披碱草 E. nutans	NH₄⁺-N	-0.436	0.239
	NO₃^--N	0.190	0.096
	SON	0.224	0.360
	STN	0.219	0.331
西北羊茅 Festuca ryloviana	NH₄⁺-N	-0.414	-0.516
	NO₃^--N	-0.636^*	-0.450
	SON	0.377	0.111
	STN	0.218	-0.098
中华羊茅 F. sinensis	NH₄⁺-N	-0.449	-0.676^*
	NO₃^--N	-0.453	-0.184
	SON	0.526	0.277
	STN	0.347	0.114
青海扁茎早熟禾 Poa pratensis var. anceps ‘Qinghai’	NH₄⁺-N	-0.293	-0.134
	NO₃^--N	-0.531	-0.266
	SON	0.460	0.017
	STN	0.338	-0.155
星星草 Puccinellia tenuiflora	NH₄⁺-N	-0.241	-0.257
	NO₃^--N	-0.052	0.113
	SON	0.146	0.216
	STN	0.083	0.200
冷地早熟禾 Poa crymophila	NH₄⁺-N	-0.494	-0.548
	NO₃^--N	-0.831^*	0.177
	SON	0.350	0.828^**
	STN	0.091	0.694^*

处理 Treatment	指标 Variable	0-10 cm	10-20 cm
无芒雀麦 Bromus inermis	NH₄⁺-N	-0.485	-0.170
	NO₃^--N	0.010	0.068
	SON	0.392	0.676^*
	STN	0.403	0.681^*
老芒麦 Elymus sibiricus	NH₄⁺-N	-0.259	-0.444
	NO₃^--N	-0.328	0.067
	SON	0.347	0.459
	STN	0.231	0.328
垂穗披碱草 E. nutans	NH₄⁺-N	-0.436	0.239
	NO₃^--N	0.190	0.096
	SON	0.224	0.360
	STN	0.219	0.331
西北羊茅 Festuca ryloviana	NH₄⁺-N	-0.414	-0.516
	NO₃^--N	-0.636^*	-0.450
	SON	0.377	0.111
	STN	0.218	-0.098
中华羊茅 F. sinensis	NH₄⁺-N	-0.449	-0.676^*
	NO₃^--N	-0.453	-0.184
	SON	0.526	0.277
	STN	0.347	0.114
青海扁茎早熟禾 Poa pratensis var. anceps ‘Qinghai’	NH₄⁺-N	-0.293	-0.134
	NO₃^--N	-0.531	-0.266
	SON	0.460	0.017
	STN	0.338	-0.155
星星草 Puccinellia tenuiflora	NH₄⁺-N	-0.241	-0.257
	NO₃^--N	-0.052	0.113
	SON	0.146	0.216
	STN	0.083	0.200
冷地早熟禾 Poa crymophila	NH₄⁺-N	-0.494	-0.548
	NO₃^--N	-0.831^*	0.177
	SON	0.350	0.828^**
	STN	0.091	0.694^*