Effects of nitrogen enrichment on root exudative carbon inputs in Sibiraea angustata shrubbery at the eastern fringe of Qinghai-Xizang Plateau

doi:10.17521/cjpe.2016.0329

Abstract

Abstract:

Aims Understanding the responses of root exudative carbon (C) to increasing nitrogen deposition is important for predicting carbon cycling in terrestrial ecosystems. However, fewer studies have investigated the dynamics of root exudation in shrubbery ecosystems compared to forests and grassland ecosystems. This objective of this study was to determine the effects of nitrogen fertilization on the rate and C flux of root exudates.Methods Three levels of nitrogen addition treatments were applied to a Sibiraea angustata shrubbery ecosystem situated at the eastern fringe of Qinghai-Xizang Plateau, including N₀(without nitrogen application), N₅(nitrogen addition rate of 5 g·m^-2·a^-1), and N₁₀(nitrogen addition rate of 10 g·m^-2·a^-1), respectively, in 5 m ´ 5 m plots. Root exudates were collected in June, August and October of 2015, using a modified culture-based cuvette system. Root biomass in each plot was measured with root core method.Important findings The rates of root exudates on biomass, length, and surface area basis all displayed apparent seasonal variations during the experimental period, with the magnitude ranked in the order of: August > June > October, consistent with changes in soil temperature at 5 cm depth. With increases in the nitrogen addition rate, the rate of root exudates on biomass, length, and area basis all trended lower. Compared with the control (N₀), the N₅ and N₁₀ treatments significantly reduced fine root biomass in the Sibiraea angustata shrubbery, by 23.36% and 33.84%, respectively. The decreasing root exudation and fine root biomass in response to nitrogen addition significantly decreased C flux of root exudates. Our results provide additional evidences toward a robust theoretical foundation for better understanding soil C-nutrient cycling process mediated by root exudation inputs in Alpine shrubbery ecosystems under various environmental changes.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201706002

Key words: Sibiraea angustata shrubbery, nitrogen addition, root exudation, root biomass, root exudation flux

Wei HE, Xue-Ying YANG, Juan XIAO, Zi-Liang ZHANG, Zheng JIANG, Yuan-Shuang YUAN, Dong WANG, Qing LIU, Hua-Jun YIN. Effects of nitrogen enrichment on root exudative carbon inputs in Sibiraea angustata shrubbery at the eastern fringe of Qinghai-Xizang Plateau[J]. Chin J Plant Ecol, 2017, 41(6): 610-621.

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Figures/Tables 9

References 58

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植物类型 Plant type	文献来源 Reference source	植物种 Plant species	单位根生物量根系分泌物C输入速率 Root exudative C input rate per root biomass (μg·g^-1·h^-1)	单位根长根系分泌物C输入速率 Root exudative C input rate per root length (μg·cm^-1·h^-1)	单位根表面积根系分泌物C输入速率 Root exudative C input rate per root surface area (μg·cm^-2·h^-1)
草本 Herbs	Personeni et al., 2007	玉米 Zea mays	-	-	2.10
	Li & Chen, 2011	美人蕉 Canna indica	175.42	-	-
		风车草 Cyperus flabelliformis	220.00	-	-
		水鬼蕉 Hymenocallis littoralis	16.79	-	-
	Cheng at al., 2016	小麦 Triticum aestivum	4.07-1.19	0.056-0.012
		平均值 Mean	83.50	0.03	2.10
乔木 Trees	Phillips et al., 2009	火炬松 Pinus taeda	2.00-40.00	-	-
	Phillips et al., 2011	火炬松 Pinus taeda	8.00-17.00	0.10-6.00	-
	Meier et al., 2013	火炬松 Pinus taeda	32.00	-	-
	Yin et al., 2013a	云杉 Picea asperata	-	0.70	9.30
	Yin et al., 2013a	冷杉 Abies faxoniana	-	0.50	4.90
	Yin et al., 2013b	云杉 Picea asperata	663.91-414.94	0.67-0.39	7.99-5.53
	Yin et al., 2014	北美鹅掌楸 Liriodendron tulipifera 糖枫 Acer saccharum	9.58	-	-
	Yin et al., 2014	北美红栎 Quercus rubra 美洲水青冈木 Fagus grandifolia	17.50	-	-
	Zhang et al., 2016	云杉 Picea asperata	396.76	-	-
	Li at al., 2014a	9年生云杉人工林 9-year-old Picea asperata	441.86	3.20	2.75
		13年生云杉人工林 13-year-old Picea asperata	284.88	3.66	1.01
		31年生云杉人工林 31-year-old Picea asperata	315.89	3.56	1.52
	Xiao, 2013	云杉幼苗 Picea asperata seedlings	79.16	0.70	9.30
	Xiao, 2013	冷杉幼苗 Abies faxoniana seedlings	65.55	0.50	4.90
	Qiao, 2015	云杉 Picea asperata	570.93	0.50	4.44
	Qiao, 2015	冷杉 Abies faxoniana	579.71	0.51	5.52
	Xiong et al., 2015	杉木 Cunninghamia lanceolata	173.68-138.04	0.37-0.14	1.67-0.46
	Xiong et al., 2015	米槠 Castanopsis carlesi	92.72-56.16	0.34-0.06	1.27-0.24
		平均值 Mean	203.07	1.29	4.05
灌木 Shrubs	本研究 This study	窄叶鲜卑花 Sibiraea angustata	26.22	0.02	0.29

植物类型 Plant type	文献来源 Reference source	植物种 Plant species	单位根生物量根系分泌物C输入速率 Root exudative C input rate per root biomass (μg·g^-1·h^-1)	单位根长根系分泌物C输入速率 Root exudative C input rate per root length (μg·cm^-1·h^-1)	单位根表面积根系分泌物C输入速率 Root exudative C input rate per root surface area (μg·cm^-2·h^-1)
草本 Herbs	Personeni et al., 2007	玉米 Zea mays	-	-	2.10
	Li & Chen, 2011	美人蕉 Canna indica	175.42	-	-
		风车草 Cyperus flabelliformis	220.00	-	-
		水鬼蕉 Hymenocallis littoralis	16.79	-	-
	Cheng at al., 2016	小麦 Triticum aestivum	4.07-1.19	0.056-0.012
		平均值 Mean	83.50	0.03	2.10
乔木 Trees	Phillips et al., 2009	火炬松 Pinus taeda	2.00-40.00	-	-
	Phillips et al., 2011	火炬松 Pinus taeda	8.00-17.00	0.10-6.00	-
	Meier et al., 2013	火炬松 Pinus taeda	32.00	-	-
	Yin et al., 2013a	云杉 Picea asperata	-	0.70	9.30
	Yin et al., 2013a	冷杉 Abies faxoniana	-	0.50	4.90
	Yin et al., 2013b	云杉 Picea asperata	663.91-414.94	0.67-0.39	7.99-5.53
	Yin et al., 2014	北美鹅掌楸 Liriodendron tulipifera 糖枫 Acer saccharum	9.58	-	-
	Yin et al., 2014	北美红栎 Quercus rubra 美洲水青冈木 Fagus grandifolia	17.50	-	-
	Zhang et al., 2016	云杉 Picea asperata	396.76	-	-
	Li at al., 2014a	9年生云杉人工林 9-year-old Picea asperata	441.86	3.20	2.75
		13年生云杉人工林 13-year-old Picea asperata	284.88	3.66	1.01
		31年生云杉人工林 31-year-old Picea asperata	315.89	3.56	1.52
	Xiao, 2013	云杉幼苗 Picea asperata seedlings	79.16	0.70	9.30
	Xiao, 2013	冷杉幼苗 Abies faxoniana seedlings	65.55	0.50	4.90
	Qiao, 2015	云杉 Picea asperata	570.93	0.50	4.44
	Qiao, 2015	冷杉 Abies faxoniana	579.71	0.51	5.52
	Xiong et al., 2015	杉木 Cunninghamia lanceolata	173.68-138.04	0.37-0.14	1.67-0.46
	Xiong et al., 2015	米槠 Castanopsis carlesi	92.72-56.16	0.34-0.06	1.27-0.24
		平均值 Mean	203.07	1.29	4.05
灌木 Shrubs	本研究 This study	窄叶鲜卑花 Sibiraea angustata	26.22	0.02	0.29

	施N N fertilization	采样日期 Sampling date	采样日期×施N Sampling date × N fertilization
单位根生物量根系分泌物C输入速率 Root exudative C input rates per root biomass	<0.001	<0.001	0.255
单位根长根系分泌物C输入速率 Root exudative C input rates per root length	<0.001	0.019	0.844
单位根表面积根系分泌物C输入速率 Root exudative C input rates per root surface area	<0.001	<0.001	<0.001

	施N N fertilization	采样日期 Sampling date	采样日期×施N Sampling date × N fertilization
单位根生物量根系分泌物C输入速率 Root exudative C input rates per root biomass	<0.001	<0.001	0.255
单位根长根系分泌物C输入速率 Root exudative C input rates per root length	<0.001	0.019	0.844
单位根表面积根系分泌物C输入速率 Root exudative C input rates per root surface area	<0.001	<0.001	<0.001

处理 Treatment	单位根生物量根系分泌物C输入速率 Root exudative C input rate per root biomass (mg·g^-1·d^-1)	细根生物量 Fine root biomass (g·m^-2)	根系分泌物C通量 C flux of root exudates (g·m^-2·a^-1)
N₀	0.68 ± 0.02^a	169.17 ± 47.83^a	16.89 ± 0.31^a
N₅	0.57 ± 0.04^b	129.65 ± 81.71^b	9.58 ± 0.24^b
N₁₀	0.36 ± 0.02^c	111.93 ± 58.49^c	5.81 ± 0.12^c