Effects of nitrogen addition on root dynamics in an alpine meadow, Northwestern Sichuan

doi:10.17521/cjpe.2017.0255

Abstract

Abstract:

Aims Our aim was to characterize the effects of nitrogen (N) addition on plant root standing crop, production, mortality and turnover in an alpine meadow on the Northwestern plateau of Sichuan Province, China.

Methods A N addition experiment was conducted in an alpine meadow on the Northwestern plateau of Sichuan Province since 2012. Urea was applied at four levels: 0, 10, 20 and 30 g·m ^-2·a ^-1, referred to as CK, N10, N20 and N30. Root samples in surface (0-10 cm) and subsurface layers (10-20 cm) were observed using Minirhizotron from May 10th to Sept. 27th in 2015. The root standing crop, production, mortality and turnover rate were estimated using WinRHZIO Tron MF software. Repeated-measure ANOVA, one-way ANOVA and Pearson correlation were performed to analyze the effect of N addition on soil and root characteristics.

Important findings N addition significantly increased soil available N content and decreased soil pH value, but did not alter soil total N and SOM contents under all treatments. N addition did not exhibit any significant effects on the mean root standing crop and cumulative root production in the 0-10 cm, but significantly reduced mean root standing crop and cumulative root production in 10-20 cm soil layer by 195.3 and 142.3 g·m ^-2 (N10), 235.8 and 212.1 g·m ^-2 (N20) and 198.0 and 204.4 g·m ^-2(N30), respectively. The cumulative root mortality was significantly decreased by 206.1 g·m ^-2in N10 treatment and root turnover rate was significantly increased with 17% for N30 treatment at the 0-10 cm soil depth, but the cumulative root mortality and root turnover rate was not significantly different at 10-20 cm soil depth. In addition, cumulative root production, mortality and turnover rate in 0-10 cm soil layer were significantly correlated with the soil available N content, whereas no significant associations were observed in 10-20 cm soil. Taken together, these results demonstrate that N addition alters the soil N availability and thus induces the root dynamics and changes in root distribution as well as C allocation in alpine meadow.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201801005

Key words: alpine meadow, nitrogen addition, plant roots, minirhizotron

ZI Hong-Biao, CHEN Yan, HU Lei, WANG Chang-Ting. Effects of nitrogen addition on root dynamics in an alpine meadow, Northwestern Sichuan[J]. Chin J Plant Ecol, 2018, 42(1): 38-49.

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Figures/Tables 6

References 64

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土层 Soil layer (cm)	处理 Treatment	pH值 pH value	有机质 SOM (g·kg^-1)	速效氮 AN (mg·kg^-1)	全氮 TN (g·kg^-1)
0-10 cm	CK	5.74 ± 0.10^Aa	110.92 ± 10.48^Aa	343.00 ± 9.40^Ac	6.38 ± 0.84^Aa
	N10	5.42 ± 0.14^Bb	119.61 ± 19.21^Aa	323.40 ± 9.96^Ad	7.01 ± 0.81^Aa
	N20	5.50 ± 0.25^Ab	121.68 ± 25.26^Aa	392.00 ± 2.46^Ab	6.95 ± 0.70^Aa
	N30	5.44 ± 0.08^Ab	124.58 ± 11.78^Aa	418.95 ± 9.15^Aa	7.27 ± 0.97^Aa
10-20 cm	CK	5.73 ± 0.08^Aa	94.60 ± 11.23^Aa	290.33 ± 7.99^Bb	5.34 ± 0.93^Aa
	N10	5.69 ± 0.27^Aa	88.10 ± 24.43^Ba	276.85 ± 8.20^Bb	5.20 ± 0.71^Aa
	N20	5.62 ± 0.19^Ab	91.91 ± 17.75^Ba	328.30 ± 6.12^Ba	5.40 ± 0.83^Aa
	N30	5.48 ± 0.16^Ab	95.30 ± 16.64^Ba	316.05 ± 4.85^Ba	5.64 ± 0.85^Aa

土层 Soil layer (cm)	处理 Treatment	pH值 pH value	有机质 SOM (g·kg^-1)	速效氮 AN (mg·kg^-1)	全氮 TN (g·kg^-1)
0-10 cm	CK	5.74 ± 0.10^Aa	110.92 ± 10.48^Aa	343.00 ± 9.40^Ac	6.38 ± 0.84^Aa
	N10	5.42 ± 0.14^Bb	119.61 ± 19.21^Aa	323.40 ± 9.96^Ad	7.01 ± 0.81^Aa
	N20	5.50 ± 0.25^Ab	121.68 ± 25.26^Aa	392.00 ± 2.46^Ab	6.95 ± 0.70^Aa
	N30	5.44 ± 0.08^Ab	124.58 ± 11.78^Aa	418.95 ± 9.15^Aa	7.27 ± 0.97^Aa
10-20 cm	CK	5.73 ± 0.08^Aa	94.60 ± 11.23^Aa	290.33 ± 7.99^Bb	5.34 ± 0.93^Aa
	N10	5.69 ± 0.27^Aa	88.10 ± 24.43^Ba	276.85 ± 8.20^Bb	5.20 ± 0.71^Aa
	N20	5.62 ± 0.19^Ab	91.91 ± 17.75^Ba	328.30 ± 6.12^Ba	5.40 ± 0.83^Aa
	N30	5.48 ± 0.16^Ab	95.30 ± 16.64^Ba	316.05 ± 4.85^Ba	5.64 ± 0.85^Aa

土层 Soil layer	根系指标 Root index	取样时间 Sampling time		N添加梯度 N addition gradient		取样时间×N添加梯度 Sampling time × N addition gradient
土层 Soil layer	根系指标 Root index	F	p	F	p	F	p
0-10 cm	根系现存量 Root standing crop	81.262	< 0.001	7.468	0.010	1.579	0.239
	根系生产量 Root production	63.809	< 0.001	1.078	0.412	9.53	< 0.001
	根系死亡量 Root mortality	131.752	< 0.001	4.477	0.04	9.693	0.001
10-20 cm	根系现存量 Root standing crop	104.472	< 0.001	7.793	0.009	3.918	0.250
	根系生产量 Root production	60.200	< 0.001	3.460	0.071	12.932	< 0.001
	根系死亡量 Root mortality	138.540	< 0.001	0.482	0.704	14.224	< 0.001

土层 Soil layer	根系指标 Root index	取样时间 Sampling time		N添加梯度 N addition gradient		取样时间×N添加梯度 Sampling time × N addition gradient
土层 Soil layer	根系指标 Root index	F	p	F	p	F	p
0-10 cm	根系现存量 Root standing crop	81.262	< 0.001	7.468	0.010	1.579	0.239
	根系生产量 Root production	63.809	< 0.001	1.078	0.412	9.53	< 0.001
	根系死亡量 Root mortality	131.752	< 0.001	4.477	0.04	9.693	0.001
10-20 cm	根系现存量 Root standing crop	104.472	< 0.001	7.793	0.009	3.918	0.250
	根系生产量 Root production	60.200	< 0.001	3.460	0.071	12.932	< 0.001
	根系死亡量 Root mortality	138.540	< 0.001	0.482	0.704	14.224	< 0.001

因子 Factor	处理 Treatment		深度 Depth		处理×深度 Treatment × Depth
因子 Factor	F	p	F	p	F	p
累积根系生产量 Cumulative root production	1.328	0.300	47.14	< 0.001	2.661	0.083
平均根系现存量 Mean root standing crop	1.770	0.190	29.93	< 0.001	1.237	0.329
根系周转 Root turnovers	1.655	0.220	0.689	0.420	1.573	0.235
累积根系死亡量 Cumulative root mortality	3.280	0.050	38.11	< 0.001	2.538	0.093