Effects of nitrogen and phosphorus addition on root characteristics of alpine meadow

doi:10.11686/cyxb2020327

Abstract

Abstract:

This research studied root characteristics， including standing root biomass， root mortality， root production and root life span in alpine meadow in Northwest Sichuan. Our methodology combined ‘minirhizotron’ root viewing tubes and indoor analysis to evaluate effects of nitrogen and phosphorus （NP） addition. The fertilization gradients were 0 （CK）， 10 （NP₁₀）， 20 （NP₂₀） and 30 g·m^-2 （NP₃₀）， respectively. We also discuss the relationships between root characteristics and soil physical and chemical properties. It was found that nitrogen and phosphorus addition increased the levels of total phosphorus， available phosphorus and available nitrogen in the 0-10 cm soil layer， decreased the pH and C∶P， but had little effect on soil total nitrogen and organic carbon levels. Also， N and P addition prolonged root life. Compared to CK， standing root length increased by 8.79 and 13.21 mm·cm^-3 in NP₂₀ and NP₃₀ treatments， respectively and the production and mortality increased by 3.17 mm·cm^-3 and 2.92 mm·cm^-3， respectively， for NP₃₀. However， in the deep soil layer （10-20 cm）， the standing root length decreased by 8.85 mm·cm^-3 for NP₁₀ and 5.37 mm·cm^-3for NP₃₀， the production decreased by 1.63 mm·cm^-3 for NP₁₀ and 1.43 mm·cm^-3 for NP₂₀， and the mortality decreased by 2.14 mm·cm^-3 for NP₁₀ and 1.78 mm·cm^-3 for NP₃₀. In addition， there was a significant correlation between standing root length， root production， root mortality and soil available nutrients （P<0.01）. In summary， NP addition made the distribution of plant roots shallower through change in the content of soil available nitrogen and phosphorus. Addition of NP slowed down root turnover by prolonging root life， reduced the carbon consumption of the root system and enhanced its carbon sink function， thus changing the carbon distribution pattern of the studied alpine meadow ecosystem.

Key words: alpine meadow, nitrogen and phosphorus addition, root characteristics, soil physical and chemical properties, minirhizotron

Li-tao TANG, Rui MAO, Chang-ting WANG, Jie LI, Lei HU, Hong-biao ZI. Effects of nitrogen and phosphorus addition on root characteristics of alpine meadow[J]. Acta Prataculturae Sinica, 2021, 30(9): 105-116.

Figures/Tables 7

References 73

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项目Item	0~10 cm	10~20 cm
生产量Production	6.31±1.40	5.50±0.83
死亡量Mortality	7.27±1.03	5.06±0.61
现存量Standing root length	30.36±3.77	25.06±2.13

项目Item	0~10 cm	10~20 cm
生产量Production	6.31±1.40	5.50±0.83
死亡量Mortality	7.27±1.03	5.06±0.61
现存量Standing root length	30.36±3.77	25.06±2.13

项目 Item	0~10 cm				10~20 cm
项目 Item	CK	NP₁₀	NP₂₀	NP₃₀	CK	NP₁₀	NP₂₀	NP₃₀
土壤含水量Soil water content （SWC，%）	30.21±0.72Aa	26.22±0.23Bc	26.11±0.06Bc	28.25±0.76Bb	31.35±1.13Aa	30.12±0.60Aa	29.38±0.45Aa	31.92±0.38Aa
土壤紧实度Soil compactness （SC，Pa）	223.12±5.49Ba	227.83±1.83Ba	233.66±14.30Ba	236.33±21.39Ba	257.83±26.29Ab	272.33±1.67Aa	279.67±4.83Aa	292.33±10.57Aa
pH	5.77±0.05Aa	5.61±0.03Aa	5.62±0.07Aa	5.70±0.02Aa	5.73±0.04Aa	5.50±0.07Ab	5.33±0.03Bb	5.38±0.06Ab
土壤有机碳Soil organic carbon （SOC，g·kg^-1）	64.34±3.57Aa	69.32±3.24Aa	73.48±2.98Aa	74.83±2.77Aa	54.87±4.01Aa	53.20±3.66Ba	49.83±2.78Ba	50.24±3.34Ba
全氮Total N （TN，g·kg^-1）	6.38±0.43Aa	6.92±0.49Aa	7.34±0.33Aa	7.41±0.73Aa	5.34±0.36Aa	5.61±0.25Aa	5.08±0.52Aa	5.10±0.57Aa
速效氮Available N （AN，mg·kg^-1）	343.36±4.23Ab	359.73±5.34Ab	380.35±7.23Aa	394.45±8.24Aa	290.33±4.44Ba	230.30±6.77Bb	271.95±5.57Ba	286.65±4.72Ba
全磷Total P （TP，g·kg^-1）	0.73±0.05Ac	0.88±0.05Ac	2.22±0.18Aa	1.03±0.09Ab	0.93±0.07Aa	0.82±0.05Aa	0.88±0.06Ba	0.80±0.04Aa
速效磷Available P （AP，mg·kg^-1）	5.40±0.47Ab	5.50±0.29Ab	10.20±0.71Aa	7.20±0.34Aa	5.35±0.57Aa	3.60±0.47Aab	3.05±0.69Bb	4.30±0.85Bab
碳氮比C∶N	10.35±1.48Aa	10.24±1.35Aa	10.21±1.26Aa	10.29±1.26Aa	10.66±1.81Aa	9.81±1.63Aa	10.22±1.85Aa	10.27±1.85Aa
碳磷比C∶P	88.67±2.45Aa	78.92±1.38Ab	33.12±0.64Bd	72.54±0.81Ac	65.09±0.50Ba	59.16±0.07Bb	56.55±0.09Ab	62.61±0.33Bb
氮磷比N∶P	8.99±1.52Aa	8.01±1.18Aa	8.33±0.34Aa	7.28±0.97Aa	5.88±0.99Aa	7.02±1.20Aa	5.91±1.05Aa	6.52±0.19Aa

项目 Item	0~10 cm				10~20 cm
项目 Item	CK	NP₁₀	NP₂₀	NP₃₀	CK	NP₁₀	NP₂₀	NP₃₀
土壤含水量Soil water content （SWC，%）	30.21±0.72Aa	26.22±0.23Bc	26.11±0.06Bc	28.25±0.76Bb	31.35±1.13Aa	30.12±0.60Aa	29.38±0.45Aa	31.92±0.38Aa
土壤紧实度Soil compactness （SC，Pa）	223.12±5.49Ba	227.83±1.83Ba	233.66±14.30Ba	236.33±21.39Ba	257.83±26.29Ab	272.33±1.67Aa	279.67±4.83Aa	292.33±10.57Aa
pH	5.77±0.05Aa	5.61±0.03Aa	5.62±0.07Aa	5.70±0.02Aa	5.73±0.04Aa	5.50±0.07Ab	5.33±0.03Bb	5.38±0.06Ab
土壤有机碳Soil organic carbon （SOC，g·kg^-1）	64.34±3.57Aa	69.32±3.24Aa	73.48±2.98Aa	74.83±2.77Aa	54.87±4.01Aa	53.20±3.66Ba	49.83±2.78Ba	50.24±3.34Ba
全氮Total N （TN，g·kg^-1）	6.38±0.43Aa	6.92±0.49Aa	7.34±0.33Aa	7.41±0.73Aa	5.34±0.36Aa	5.61±0.25Aa	5.08±0.52Aa	5.10±0.57Aa
速效氮Available N （AN，mg·kg^-1）	343.36±4.23Ab	359.73±5.34Ab	380.35±7.23Aa	394.45±8.24Aa	290.33±4.44Ba	230.30±6.77Bb	271.95±5.57Ba	286.65±4.72Ba
全磷Total P （TP，g·kg^-1）	0.73±0.05Ac	0.88±0.05Ac	2.22±0.18Aa	1.03±0.09Ab	0.93±0.07Aa	0.82±0.05Aa	0.88±0.06Ba	0.80±0.04Aa
速效磷Available P （AP，mg·kg^-1）	5.40±0.47Ab	5.50±0.29Ab	10.20±0.71Aa	7.20±0.34Aa	5.35±0.57Aa	3.60±0.47Aab	3.05±0.69Bb	4.30±0.85Bab
碳氮比C∶N	10.35±1.48Aa	10.24±1.35Aa	10.21±1.26Aa	10.29±1.26Aa	10.66±1.81Aa	9.81±1.63Aa	10.22±1.85Aa	10.27±1.85Aa
碳磷比C∶P	88.67±2.45Aa	78.92±1.38Ab	33.12±0.64Bd	72.54±0.81Ac	65.09±0.50Ba	59.16±0.07Bb	56.55±0.09Ab	62.61±0.33Bb
氮磷比N∶P	8.99±1.52Aa	8.01±1.18Aa	8.33±0.34Aa	7.28±0.97Aa	5.88±0.99Aa	7.02±1.20Aa	5.91±1.05Aa	6.52±0.19Aa

因子 Factor	df	现存量Standing root length		死亡量Mortality		生产量Production
因子 Factor	df	F	P	F	P	F	P
处理Treatment	3	44.44	<0.01	18.89	<0.01	7.38	<0.01
深度Depth	1	59.82	<0.01	39.89	<0.01	25.07	<0.01
处理×深度Treatment×depth	3	0.94	0.49	1.75	0.15	2.30	0.07