土壤增温、氮添加及其交互作用对杉木幼苗细根生产的影响

doi:10.17521/cjpe.2016.0274

摘要/Abstract

摘要：

为了揭示杉木(Cunninghamia lanceolata)人工林地下部分对全球变暖和氮沉降的响应, 在福建省三明市开展了杉木幼苗土壤增温和氮添加双因子试验, 包括对照、增温、低氮、高氮、增温低氮、增温高氮6个处理, 用微根管法探讨试验第1年土壤增温、氮添加及其交互作用对杉木幼苗细根生产量(以每根管细根一年总出生数量作为表征)的影响。结果表明: (1)土壤增温对细根生产量有显著影响; 氮添加、土壤增温与氮添加交互作用对细根生产量并没有显著影响。(2)土壤增温、径级、土壤增温和径级的交互作用对细根生产量有显著影响; 土壤增温显著增加了0-1 mm径级细根的生产量, 表明小径级的吸收根对于增温的响应更具有可塑性。(3)土壤增温、季节、土壤增温和季节的交互作用, 以及土壤增温、氮添加和季节三者的交互作用对细根生产量的影响均达到显著水平。春季, 土壤增温、土壤增温和氮添加的交互作用对细根生产量有显著的促进作用; 而在夏季, 土壤增温、氮添加以及两者的交互作用对细根生产量有显著的抑制作用。(4)土壤增温、土层, 以及土壤增温和土层的交互作用对细根生产量有显著影响, 土壤增温仅对20-30 cm土层的细根生产有显著的促进作用, 表明土壤增温促使细根向更深层土壤分布。由此可见: 土壤增温促进了杉木幼苗细根生产, 但其影响因径级、季节和土层而异; 氮添加则对细根生产没有影响; 土壤增温和氮添加仅在春季和夏季才存在显著的交互作用。

关键词: 土壤增温, 氮添加, 杉木, 微根管, 细根生产

Abstract:

Aims There have been a large number of studies on the independent separate responses of fine roots to warming and nitrogen deposition, but with contradictory reporting. Fine root production plays a critical role in ecosystem carbon, nutrient and water cycling, yet how it responds to the interactive warming and nitrogen addition is not well understood. In the present study, we aimed to examine the interactive effects of soil warming and nitrogen addition on fine root growth of 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings in subtropical China.
Methods A mesocosm experiment, with a factorial design of soil warming (ambient, +5 °C) and nitrogen addition (ambient, ambient + 40 kg·hm^-2·a^-1, ambient + 80 kg·hm^-2·a^-1), was carried out in the Chenda State-owned Forest Farm in Sanming City, Fujian Province, China. Fine root production (indexed by the number of fine roots emerged per tube of one year) was measured biweekly using minirhizotrons from March of 2014 to February of 2015.
Important findings (1) The two-way ANOVA showed that soil warming had a significant effect on fine root production, while nitrogen addition and soil warming × nitrogen addition had no effect. (2) The three-way ANOVA (soil warming, nitrogen addition and diameter class) showed that soil warming, diameter class and soil warming × diameter class had significant effects on fine root production, especially for the number of fine roots in 0-1 mm diameter class that had been significantly increased by soil warming. Compared with the 1-2 mm roots, the 0-1 mm roots seemed more flexible. (3) Repeated measures of ANOVA (soil warming, nitrogen addition and season) showed that soil warming, season, soil warming × season, and soil warming × nitrogen addition × season had significant effects on fine root production. In spring, the number of fine roots was significantly increased both by soil warming and soil warming × season, while soil warming, nitrogen addition, soil warming × nitrogen addition significantly decreased fine root production in the summer. (4) Soil warming, soil layer, soil warming × soil layer had significant effects on fine root production. The number of in-growth fine roots was significantly increased by soil warming at the 20-30 cm depth only. It seemed that warming forced fine roots to grow deeper in the soil. In conclusion, soil warming significantly increased fine root production, but they had different responses and were dependent of different diameter classes, seasons and soil layers. Nitrogen addition had no effect on fine root production. Only in spring and summer, soil warming and nitrogen addition had significant interactive effects.

Key words: soil warming, nitrogen addition, Cunninghamia lanceolata, minirhizotron, fine root production

史顺增, 熊德成, 邓飞, 冯建新, 许辰森, 钟波元, 陈云玉, 陈光水, 杨玉盛. 土壤增温、氮添加及其交互作用对杉木幼苗细根生产的影响. 植物生态学报, 2017, 41(2): 186-195. DOI: 10.17521/cjpe.2016.0274

Shun-Zeng SHI, De-Cheng XIONG, Fei DENG, Jian-Xin FENG, Chen-Sen XU, Bo-Yuan ZHONG, Yun-Yu CHEN, Guang-Shui CHEN, Yu-Sheng YANG. Interactive effects of soil warming and nitrogen addition on fine root production of Chinese fir seedlings. Chinese Journal of Plant Ecology, 2017, 41(2): 186-195. DOI: 10.17521/cjpe.2016.0274

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2016.0274

https://www.plant-ecology.com/CN/Y2017/V41/I2/186

图/表 12

图1 不同处理(以对照(不增温、不添加额外氮素的处理, ▲)和土壤增温处理(+5 ℃、不添加额外氮素的处理, ■)为例) 0-10 cm土壤温度(A)和含水率(B)的年变化(平均值±标准偏差)。

Fig. 1 Annual changes of soil (0-10 cm) temperature (A) and moisture (B) under different treatments (mean ± SD). ▲, control treatment (ambient, ambient); ■, soil warming treatment (+5 °C, ambient).

图2 不同处理0-20 cm土壤氮有效性(平均值±标准偏差)。NH4+, 铵态氮。NO3- + NO2-, 硝态氮。CT, 对照(不增温、不添加额外氮素); HN, 高氮(不增温, +80 kg·hm-2·a-1, 指自然氮沉降背景下, 再额外添加的氮素量,下同); LN, 低氮(不增温, +40 kg·hm-2·a-1); W, 土壤增温(+5 ℃, 不添加额外氮素); WHN, 土壤增温+高氮(+5 ℃, +80 kg·hm-2·a-1); WLN, 土壤增温+低氮(+5 ℃, +40 kg·hm-2·a-1)。不同大写字母表示不同处理间差异显著(p < 0.05)。

Fig. 2 Soil (0-20 cm) nitrogen availability under different treatments (mean ± SD). NH4+, ammonium nitrogen. NO3- + NO2-, nitrate nitrogen. CT, control treatment (ambient, ambient); HN, high nitrogen addition (ambient, ambient + 80 kg·hm-2·a-1); LN, low nitrogen addition (ambient, ambient + 40 kg·hm-2·a-1); W, soil warming (+5 °C, ambient); WHN, soil warming plus high nitrogen addition (+5 °C, ambient + 80 kg·hm-2·a-1); WLN, soil warming plus low nitrogen addition (+5 °C, ambient + 40 kg·hm-2·a-1). Different capital letters indicate significant differences among treatments (p < 0.05).

表1 土壤增温、氮添加及其交互作用对土壤温度、含水率和土壤有效氮影响的双因素方差分析p值

Table 1 p-value of two-way ANOVA on the effects of soil warming, nitrogen addition and their interaction on soil temperature, soil moisture and soil nitrogen availability

因子 Factor	土壤温度 Soil temperature (℃)	土壤湿度 Soil moisture (%)	铵态氮 Ammonium nitrogen	硝态氮 Nitrate nitrogen	土壤有效氮(铵态氮和硝态氮) Soil nitrogen availability (ammonium nitrogen and nitrate nitrogen)
W	<0.001	0.005	<0.001	<0.001	<0.001
N			<0.001	<0.001	<0.001
W × N			<0.001	0.317	<0.001

表2 土壤增温、氮添加及其交互作用对每根管细根一年总出生数量影响的双因素方差分析p值

Table 2 p-value of two-way ANOVA on the effects of soil warming, nitrogen addition and their interaction on total number of fine roots emerged per tube of one year

指标 Index	因子 Factor
指标 Index	W	N	W × N
每根管细根一年总出生数量 Total number of fine roots emerged per tube of one year (No.·tube^-1·a^-1)	0.005	0.616	0.483

图3 不同处理每根管细根一年总出生数量(A)和细根径级分布(B)(平均值±标准偏差)。不同大写字母表示不同处理差异显著(p < 0.05), 不同小写字母表示相同处理不同径级间差异显著(p < 0.05)。CT, 对照(不增温、不添加额外氮素); HN, 高氮(不增温, +80 kg·hm-2·a-1, 指自然氮沉降背景下, 再额外添加的氮素量,下同); LN, 低氮(不增温, +40 kg·hm-2·a-1); W, 土壤增温(+5 ℃, 不添加额外氮素); WHN, 土壤增温+高氮(+5 ℃, +80 kg·hm-2·a-1); WLN, 土壤增温+低氮(+5 ℃, +40 kg·hm-2·a-1)。

Fig. 3 Total number of fine roots emerged of one year (A) under different treatments and number of different diameter class (B) (mean ± SD). Different capital letters indicate significant differences among treatments (p < 0.05). Different lowercase letters indicate significant differences among diameters (p < 0.05). CT, control treatment (ambient, ambient); HN, high nitrogen addition (ambient, ambient + 80 kg·hm-2·a-1); LN, low nitrogen addition (ambient, ambient + 40 kg·hm-2·a-1); W, soil warming (+5 °C, ambient); WHN, soil warming plus high nitrogen addition (+5 °C, ambient + 80 kg·hm-2·a-1); WLN, soil warming plus low nitrogen addition (+5 °C, ambient + 40 kg·hm-2·a-1).

表3 土壤增温、氮添加和径级对每根管细根一年总出生数量影响的方差分析p值

Table 3 p-value of ANOVA on the effects of soil warming, nitrogen addition and diameter class on total number of fine roots emerged per tube of one year

指标 Index	因子 Factor
指标 Index	W	N	D	W × N	W × D	N × D	W × N × D
每根管细根一年总出生数量 Total number of fine roots emerged per tube of one year (No.·tube^-1·a^-1)	0.004	0.624	<0.001	0.491	0.002	0.44	0.431

表4 不同径级、不同季节、不同土层中的土壤增温、氮添加及其交互作用对每根管细根一年总出生数量影响的双因素方差分析p值

Table 4 p-value of two-way ANOVA on the effects of soil warming, nitrogen addition and their interaction on total number of fine roots emerged per tube of one year in different diameter classes, seasons and soil layers

指标 Index	因子 Factor		W	N	W × N
每根管细根一年总出生数量 Total mumber of fine roots emerged per tube of one year (No.·tube^-1·a^-1)	径级 Diameter class	0-1 mm	0.004	0.535	0.465
	径级 Diameter class	1-2 mm	0.137	0.182	0.505
	季节 Season	春季 Spring	<0.001	0.529	0.010
		夏季 Summer	0.003	0.001	0.041
		秋季 Autumn	0.226	0.555	0.971
		冬季 Winter	0.702	0.175	0.313
	土层 Soil layer	0-10 cm	0.547	0.488	0.423
		10-20 cm	0.158	0.114	0.052
		20-30 cm	0.005	0.424	0.892
		30-40 cm	0.124	0.379	0.892

表5 土壤增温、氮添加和季节对每根管细根一年总出生数量影响的重复测量方差分析的p值

Table 5 p-value of repeated measures ANOVA on the effects of soil warming, nitrogen addition and season on total number of fine roots emerged per tube of one year

指标 Index	因子 Factor
指标 Index	W	N	S	W × N	W × S	N × S	W × N × S
每根管细根一年总出生数量 Total number of fine roots emerged per tube of one year (No.·tube^-1·a^-1)	0.005	0.616	<0.001	0.483	<0.001	0.193	0.025

图4 不同季节每根管细根一年总出生数量(平均值±标准偏差)。不同大写字母表示相同季节不同处理间差异显著(p < 0.05), 不同小写字母表示相同处理不同季节间差异显著(p < 0.05)。CT, 对照 (不增温、不添加额外氮素); HN, 高氮(不增温, +80 kg·hm-2·a-1, 指自然氮沉降背景下, 再额外添加的氮素量,下同); LN, 低氮(不增温, +40 kg·hm-2·a-1); W, 土壤增温(+5 ℃, 不添加额外氮素); WHN, 土壤增温+高氮(+5 ℃, +80 kg·hm-2·a-1); WLN, 土壤增温+低氮(+5 ℃, +40 kg·hm-2·a-1)。

Fig. 4 Total number of fine roots emerged per tube of one year under different seasons (mean ± SD). Different capital letters indicate significant differences among treatments in the same season (p < 0.05). Different lowercase letters indicate significant differences among seasons in the same treatment (p < 0.05). CT, control treatment (ambient, ambient); HN, high nitrogen addition (ambient, ambient + 80 kg·hm-2·a-1); LN, low nitrogen addition (ambient, ambient + 40 kg·hm-2·a-1); W, soil warming (+5 °C, ambient); WHN, soil warming plus high nitrogen addition (+5 °C, ambient + 80 kg·hm-2·a-1); WLN, soil warming plus low nitrogen addition (+5 °C, ambient + 40 kg·hm-2·a-1).

图5 不同土层每根管细根一年总出生数量(平均值±标准偏差)。不同大写字母表示相同土层不同处理间差异显著(p < 0.05); 不同小写字母表示相同处理不同土层间差异显著(p < 0.05)。CT, 对照(不增温、不添加额外氮素); HN, 高氮(不增温, +80 kg·hm-2·a-1, 指自然氮沉降背景下, 再额外添加的氮素量,下同); LN, 低氮(不增温, +40 kg·hm-2·a-1); W, 土壤增温(+5 ℃, 不添加额外氮素); WHN, 土壤增温+高氮(+5 ℃, + 80 kg·hm-2·a-1); WLN, 土壤增温+低氮(+5 ℃, + 40 kg·hm-2·a-1)。

Fig. 5 Total number of fine roots emerged per tube of one year under different soil layer (mean ± SD). Different capital letters indicate significant differences among treatments in the same soil layer (p < 0.05). Different lowercase letters indicate significant differences among soil layers in the same treatment (p < 0.05). CT, control treatment (ambient, ambient); HN, high nitrogen addition (ambient, ambient + 80 kg·hm-2·a-1); LN, low nitrogen addition (ambient, ambient + 40 kg·hm-2·a-1); W, soil warming (+5 °C, ambient); WHN, soil warming plus high nitrogen addition (+5 °C, ambient + 80 kg·hm-2·a-1); WLN, soil warming plus low nitrogen addition (+5 °C, ambient + 40 kg·hm-2·a-1).

表6 土壤增温、氮添加和土层对每根管细根一年总出生数量影响的方差分析p值

Table 6 p-value of ANOVA on the effects of soil warming, nitrogen addition and soil layer on total number of fine roots emerged per tube of one year

指标 Index	因子 Factor
指标 Index	W	N	L	W × N	W × L	N × L	W × N × L
每根管细根一年总出生数量 Total number of fine roots emerged per tube of one year (No.·tube^-1·a^-1)	0.001	0.563	0.06	0.419	0.025	0.256	0.765

图6 土壤增温和氮添加对杉木幼苗细根生产的影响机制。“+”表示促进; “-”表示抑制; “NS”表示无显著影响。红色箭头表示受土壤增温的影响; 黑色箭头表示受氮添加的影响。

Fig. 6 Proposed mechanism on the effects of soil warming and nitrogen addition on fine root production. “+” means increase; “-” means decrease; “NS” means have no significant effect. The red arrows mean effects by soil warming; while the black arrows mean effects by nitrogen addition.

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