高寒草原土壤交换性盐基离子对氮添加的响应: 以紫花针茅草原为例

doi:10.17521/cjpe.2017.0100

摘要/Abstract

摘要：

土壤交换性盐基离子(Ca ²⁺、Mg ²⁺、K ⁺、Na ⁺)在维持土壤养分与缓冲土壤酸化中起着重要作用, 了解其对氮添加的响应有助于准确评估氮沉降背景下生态系统结构与功能的动态变化。然而, 目前关于土壤交换性盐基离子对氮添加响应的相关研究主要集中在酸性土中。鉴于目前在碱性土中研究相对较少的现状, 该研究以青藏高原高寒草原为研究对象, 依托氮添加控制实验平台, 通过连续3年(2014-2016)的测定, 考察了8个不同施氮水平(0、1、2、4、8、16、24、32 g·m ^-2·a ^-1)下土壤交换性盐基离子含量变化及其可能原因。结果显示: 随着施氮量的增加, 土壤交换性盐基离子, 尤其是Mg ²⁺与Na ⁺含量显著降低。并且, 盐基离子含量与植物地上生物量显著负相关(p < 0.05), 说明氮添加通过促进植物生长, 加速植物对盐基离子的吸收, 进而导致土壤中盐基离子含量降低。此外, 盐基离子含量也与土壤无机氮含量呈显著负相关(p < 0.05)关系, 说明施氮还通过提高土壤中无机氮含量进而导致更多NH₄ ⁺与土壤吸附的盐基离子交换, 同时加剧NO₃ ^-淋溶, 带走等电荷阳离子。需要指出的是, 虽然连续施氮导致土壤pH值下降, 但该土壤目前仍处于碳酸盐缓冲阶段, 说明通常在酸性土中报道的“因缓冲土壤酸化引起的盐基离子损失机制”在碱性土中并不成立。这些结果意味着持续的氮输入会造成碱性土中盐基离子损失, 进而影响土壤缓冲能力与植被生产力, 未来草原生态系统管理中应重视这一问题。

关键词: 交换性盐基离子, 氮沉降, 碱性土, 植物吸收, 缓冲阶段

Abstract:

Aims Soil exchangeable base cations (BCs) play important roles in keeping soil nutrient and buffering soil acidification, which may be disturbed by anthropogenic nitrogen (N) input. Considering relatively limited evidence from alkaline soils, this study was designed to explore the effects of N addition on soil exchangeable BCs in a typical alpine steppe on the Qinghai-Xizang Plateau.

Methods From May 2013, eight levels of N addition (0, 1, 2, 4, 8, 16, 24, 32 g·m ^-2·a ^-1) in the form of NH₄NO₃ were added in the alpine steppe, where soil is alkaline. During the following three years (2014-2016), we collected soil samples in mid-August in each year. By measuring the concentrations of exchangeable BCs, we examined their changes along the N addition gradient. We also explored the relationships between BCs and other plant and soil properties.

Important findings Continuous N addition resulted in significant loss of exchangeable BCs, especially Mg ²⁺ in all three years and Na ⁺in two years. The concentrations of BCs were found to be negatively related to above-ground biomass and the concentration of soil inorganic N (p < 0.05). These results indicated that increase in N availability stimulated plant growth, which in turn led to more uptake of BCs by plants. Moreover, enhanced NO₃ ^- leaching resulted in the loss of BCs due to the charge balance in soil solution. In addition, increased NH₄ ⁺ displaced BCs binding to soil surface and made them easy to be leached out of soils. Different from acid soils, soil acidification caused by N deposition in alkaline soils is mainly buffered by calcium carbonate, having less effect on BCs. Our results suggest that N addition results in the loss of exchangeable BCs in alkaline soils, leading to poor buffering capacity and decreased plant productivity over long time period, which needs to be considered during grassland management in the future.

Key words: exchangeable base cations, nitrogen deposition, alkaline soil, plant uptake, buffering phase

秦书琪, 房凯, 王冠钦, 彭云峰, 张典业, 李飞, 周国英, 杨元合. 高寒草原土壤交换性盐基离子对氮添加的响应: 以紫花针茅草原为例. 植物生态学报, 2018, 42(1): 95-104. DOI: 10.17521/cjpe.2017.0100

QIN Shu-Qi, FANG Kai, WANG Guan-Qin, PENG Yun-Feng, ZHANG Dian-Ye, LI Fei, ZHOU Guo-Ying, YANG Yuan-He. Responses of exchangeable base cations to continuously increasing nitrogen addition in alpine steppe: A case study of Stipa purpurea steppe. Chinese Journal of Plant Ecology, 2018, 42(1): 95-104. DOI: 10.17521/cjpe.2017.0100

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2017.0100

https://www.plant-ecology.com/CN/Y2018/V42/I1/95

图/表 9

表1 不同氮水平下土壤与植物基本理化性质(平均值±标准误差)

Table 1 Soil and plant properties under different nitrogen rates (mean ± SE)

	年 Year	N0	N1	N2	N4	N8	N16	N24	N32
pH值 pH value	2014	8.9 ± 0.10^b	9.2 ± 0.06^a	9.2 ± 0.08^a	9.1 ± 0.07^ab	9.1 ± 0.08^ab	9.1 ± 0.07^ab	9.0 ± 0.03^ab	9.1 ± 0.10^ab
	2015	9.0 ± 0.07^bc	9.1 ± 0.06^a	9.0 ± 0.03^ab	9.0 ± 0.05^ab	8.9 ± 0.03^cd	9.0 ± 0.04^ab	8.8 ± 0.04^d	8.8 ± 0.05^d
	2016	8.5 ± 0.11^a	8.5 ± 0.05^a	8.5 ± 0.09^a	8.4 ± 0.07^ab	8.3 ± 0.07^bc	8.6 ± 0.02^a	8.2 ± 0.05^c	8.2 ± 0.05^c
TIN (mg·kg^-1)	2014	34.3 ± 2.6^cd	37.8 ± 3.1^bcd	35.9 ± 3.7^bcd	33.1 ± 0.9^d	52.6 ± 9.1^a	46.8 ± 3.4^ab	43.5 ± 1.8^abcd	45.5 ± 1.4^abc
	2015	9.5 ± 0.3^e	11.4 ± 1.5^e	11.8 ± 1.1^e	11.9 ± 0.7^e	22.4 ± 2.5^d	41.8 ± 2.5^c	56.7 ± 5.0^b	69.6 ± 7.1^a
	2016	32.0 ± 0.9^d	32.3 ± 1.5^cd	31.2 ± 2.0^d	32.9 ± 2.0^cd	37.4 ± 1.9^bc	41.4 ± 2.8^ab	43.2 ± 3.0^a	41.1 ± 2.1^ab
AGB (g·m^-2)	2014	126.9 ± 10.0^d	142.2 ± 17.8^d	152.4 ± 13.9^cd	186.7 ± 13.9^c	256.6 ± 14.3^ab	241.2 ± 21.4^b	271.7 ± 26.1^ab	284.9 ± 27.6^a
	2015	146.0 ± 11.6^c	146.8 ± 8.3^c	175.7 ± 14.7^c	180.4 ± 13.6^c	265.1 ± 23.5^b	287.5 ± 21.0^b	350.4 ± 13.3^a	373.0 ± 18.6^a
	2016	93.7 ± 9.3^e	117.0 ± 17.8^de	127.0 ± 19.3^cde	144.2 ± 9.3^bcd	181.2 ± 18.4^ab	161.9 ± 8.3^abc	190.2 ± 21.1^a	195.7 ± 7.1^a

图1 氮添加对土壤交换性盐基离子含量的影响(平均值±标准误差)。N0-N32, 氮添加量分别为: 0、1、2、4、8、16、24、32 g·m-2·a-1。不同字母表示各施氮量下差异显著(p < 0.05)。

Fig. 1 Effects of nitrogen addition on soil exchangeable base cations (mean ± SE). N0-N32, nitrogen addition 0, 1, 2, 4, 8, 16, 24, 32 g·m-2·a-1, respectively. Different letters indicate significant differences among treatments (p < 0.05).

图2 氮添加对土壤交换性Ca2+、Mg2+、K+、Na+的影响(平均值±标准误差)。A, Ca2+。B, Mg2+。C, K+。D, Na+。N0-N32, 氮添加量分别为: 0、1、2、4、8、16、24、32 g·m-2·a-1。不同字母表示各施氮量下差异显著(p < 0.05)。

Fig. 2 Effects of nitrogen addition on soil exchangeable Ca2+, Mg2+, K+, Na+ (mean ± SE)。A, Ca2+. B, Mg2+. C, K+. D, Na+. N0-N32, nitrogen addition 0, 1, 2, 4, 8, 16, 24, 32 g·m-2·a-1, respectively. Different letters indicate significant differences among treatments (p < 0.05).

图3 2015年交换性盐基离子与地上生物量和土壤总无机氮含量的关系。A, 地上生物量(AGB)。B, 土壤总无机氮(TIN)。直线与阴影部分分别表示拟合曲线与95%置信区间。

Fig. 3 Relationships of soil exchangeable base cations with above-ground biomass and soil total inorganic nitrogen in 2015. A, above-ground biomass (AGB). B, soil total inorganic nitrogen (TIN). The black lines represent the fitted curves and shades for 95% confidence intervals.

图4 不同年份土壤交换性Mg2+与地上生物量以及土壤总无机氮含量的关系。A, 2014年AGB。B, 2014年TIN。C, 2015年AGB。D, 2015年TIN。E, 2016年AGB。F, 2016年TIN。AGB, 地上生物量, TIN, 土壤总无机氮。直线与阴影部分分别表示拟合曲线与95%置信区间。

Fig. 4 Relationships of soil exchangeable Mg2+ with above-ground biomass and soil total inorganic nitrogen in different years. A, AGB in 2014. B, TIN in 2014. C, AGB in 2015. D, TIN in 2015. E, AGB in 2016. F, TIN in 2016. AGB, above-ground biomass, TIN, soil total inorganic nitrogen. The black lines represent the fitted curves and shades for 95% confidence intervals.

图5 不同年份土壤交换性Na+与土壤总无机氮含量的关系。A, 2014年。B, 2015年。TIN, 土壤总无机氮。直线与阴影部分分别表示拟合曲线与95%置信区间。

Fig. 5 Relationships of soil exchangeable Na+ with soil total inorganic nitrogen in different years. A, 2014. B, 2015. TIN, soil total inorganic nitrogen. The black lines represent the fitted curves and shades for 95% confidence intervals.

附件I 青藏高原高寒草地表层土壤pH值的频度分布。数据来自杨元合课题组于2013-2014年间在青藏高原草地样带调查的173个样地

Appendix I Frequency distribution of pH values on the Qinghai-Xizang Plateau. Data from 173 sampling sites along a grassland transect across Qinghai-Xizang alpine grasslands during 2013-2014, which were collected by members from Dr. Yuanhe Yang’s group

附件II 氮添加对植物地上部分Mg库的影响(平均值±标准误差)。A, 2014年。B, 2015年。C, 2016年。N0-N32, 氮添加量分别为: 0、1、2、4、8、16、24、32 g·m-2·a-1。不同字母表示各施氮量下差异显著(p < 0.05)

Appendix II Effects of nitrogen addition on Mg pool in aboveground plant (mean ± SE). A, 2014. B, 2015. C, 2016. N0-N32, nitrogen addition 0, 1, 2, 4, 8, 16, 24, 32 g·m -2·a -1, respectively. Different letters indicate significant differences among treatments (p < 0.05)

附件III 2016年氮添加对表层0-10 cm土壤NO3-淋溶量的影响(平均值±标准误差)。N0-N32, 氮添加量分别为: 0、1、2、4、8、16、24、32 g·m-2·a-1。不同字母表示各施氮量下差异显著(p < 0.05)

Appendix III Effects of nitrogen addition on NO3 - leaching in top 0-10 cm soil in 2016 (mean ± SE). N0-N32, nitrogen addition 0, 1, 2, 4, 8, 16, 24, 32 g·m -2·a -1, respectively. Different letters indicate significant differences among treatments (p < 0.05)

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