为阐明南亚热带4个主要树种——海南红豆(Ormosia pinnata)、马占相思(Acacia mangium)、木荷(Schima superba)和马尾松(Pinus massoniana)幼苗生长对不同氮添加量和添加方式的响应差异, 进行了幼苗模拟氮添加实验。实验设置3个氮添加水平(对照: 背景大气氮沉降量5.6 g N·m-2·a-1, 中氮: 15.6 g N·m-2·a-1, 高氮: 20.6 g N·m-2·a-1), 每个水平分两种添加方式(幼苗冠层施氮和土壤表层施氮), 共6个处理: (1)土壤对照(S-CK); (2)土壤中氮(S-MN); (3)土壤高氮(S-HN); (4)冠层对照(C-CK); (5)冠层中氮(C-MN); (6)冠层高氮(C-HN), 每个处理设置6个重复。研究结果表明: 不同氮添加量下, 土壤施氮和冠层施氮对植物幼苗生长的影响不同, 氮添加量、氮添加方式和物种3个因子之间存在显著的交互效应。与对照相比, S-MN增加了马占相思和木荷幼苗的生物量, 降低了马尾松的株高和生物量, 而C-MN仅增加了马占相思的生物量, 对其他3个树种没有影响; S-HN增加了马占相思的生物量, 显著降低了马尾松的基径、株高和生物量(p < 0.01), C-HN增加了马占相思、木荷和马尾松的基径、株高和生物量(p < 0.01)。不同氮添加量和氮添加方式对幼苗生长的影响因物种而异, 所有氮处理下海南红豆和马占相思的生长均明显快于木荷和马尾松; 木荷和马尾松幼苗的生长在两种氮添加方式间差异显著, 冠层施氮比土壤施氮对其幼苗生长的促进作用更大。由此可见: 在氮沉降背景下, 阔叶豆科植物(海南红豆、马占相思)比阔叶非豆科植物(木荷)生长快; 阔叶树种(海南红豆、马占相思和木荷)比针叶树种(马尾松)生长快。在长期氮沉降环境下, 不同物种生长的差异响应有可能导致亚热带森林物种组成发生变化。
Aims Numerous studies have been carried out concerning the effects of atmospheric nitrogen (N) deposition on forest ecosystems. However, most of previous experiments were conducted by adding N fertilizer to the surface soil directly. Realistically simulated canopy N deposition and comparison of the effects of soil N addition and canopy N addition on ecosystems were rare. Our purpose is to better understand the effects of two N addition regimes at different N addition levels on seeding growth in major tree species of subtropical China.
Methods A 2-year pot experiment was conducted, with seedlings of four species (Ormosia pinnata, Acacia mangium, Schima superba, Pinus massoniana) grown in pots subjected to treatments of three levels (ambient, medium, and high) and two regimes (in soil vs. on canopy) of N addition, specifically including S-CK (ambient N addition in soil), S-MN (medium N addition in soil), S-HN (high N addition in soil), C-CK (ambient N addition on canopy), C-MN (medium N addition on canopy), and C-HN (high N addition on canopy). The total amounts of added N in the three N levels were 5.6, 15.6 and 20.6 g·m-2·a-1, respectively. Tree basal diameter and tree height were measured in June and December 2012, and November 2013. All trees were harvested in November 2013, and then the biomass was calculated according to the dry-mass of roots, shoots and leaves; the root-shoot ratios were calculated.
Important findings N treatments affected seeding growth, along with significant interactive effects among N addition level, N addition regime and species. Compared to CK, S-MN stimulated the biomass in seedlings of A. mangium and S. superba, but decreased the tree height and biomass in seedlings of P. massoniana; C-MN increased the biomass in seedlings of A. mangium; S-HN promoted the biomass in seedlings of A. mangium, but significantly decreased the biomass, basal diameter and tree height in seedlings of P. massoniana (p < 0.01); C-HN led to the greater growth in seedlings of A. mangium, S. superba and P. massoniana (p < 0.01). N addition responses were dependent upon plant species: while seedlings in O. pinnata and A. mangium grew faster than S. superba and P. massoniana under all N treatments, the differences in the growth of S. superba and P. massoniana seedlings between the two N addition regimes were more pronounced than in O. pinnata and A. mangium seedlings. We concluded that legumes (O. pinnata and A. mangium) grew faster than non-legumes (S. superba). And growth stimulation in broadleaved trees (O. pinnata, A. mangium, and S. superba) by N addition was significantly greater than in coniferous trees (P. massoniana). Our findings suggest that the relatively high and chronic atmospheric N deposition in subtropical forest ecosystems may lead to changes in species composition.
全 文 :植物生态学报 2015, 39 (10): 950–961 doi: 10.17521/cjpe.2015.0092
Chinese Journal of Plant Ecology http://www.plant-ecology.com
——————————————————
收稿日期Received: 2015-01-29 接受日期Accepted: 2015-08-13
* 通讯作者Author for correspondence (E-mail: ljxiu@scbg.ac.cn)
不同氮添加量和添加方式对南亚热带4个主要树种
幼苗生长的影响
刘双娥1,2 李义勇1,2 方 熊1,2 黄文娟1 龙凤玲1,2 刘菊秀1*
1中国科学院华南植物园, 广州 510650; 2中国科学院大学, 北京 100049
摘 要 为阐明南亚热带4个主要树种——海南红豆(Ormosia pinnata)、马占相思(Acacia mangium)、木荷(Schima superba)和
马尾松(Pinus massoniana)幼苗生长对不同氮添加量和添加方式的响应差异, 进行了幼苗模拟氮添加实验。实验设置3个氮添
加水平(对照: 背景大气氮沉降量5.6 g N·m–2·a–1, 中氮: 15.6 g N·m–2·a–1, 高氮: 20.6 g N·m–2·a–1), 每个水平分两种添加方式(幼
苗冠层施氮和土壤表层施氮), 共6个处理: (1)土壤对照(S-CK); (2)土壤中氮(S-MN); (3)土壤高氮(S-HN); (4)冠层对照(C-CK);
(5)冠层中氮(C-MN); (6)冠层高氮(C-HN), 每个处理设置6个重复。研究结果表明: 不同氮添加量下, 土壤施氮和冠层施氮对植
物幼苗生长的影响不同, 氮添加量、氮添加方式和物种3个因子之间存在显著的交互效应。与对照相比, S-MN增加了马占相
思和木荷幼苗的生物量, 降低了马尾松的株高和生物量, 而C-MN仅增加了马占相思的生物量, 对其他3个树种没有影响;
S-HN增加了马占相思的生物量, 显著降低了马尾松的基径、株高和生物量(p < 0.01), C-HN增加了马占相思、木荷和马尾松的
基径、株高和生物量(p < 0.01)。不同氮添加量和氮添加方式对幼苗生长的影响因物种而异, 所有氮处理下海南红豆和马占相
思的生长均明显快于木荷和马尾松; 木荷和马尾松幼苗的生长在两种氮添加方式间差异显著, 冠层施氮比土壤施氮对其幼苗
生长的促进作用更大。由此可见: 在氮沉降背景下, 阔叶豆科植物(海南红豆、马占相思)比阔叶非豆科植物(木荷)生长快; 阔
叶树种(海南红豆、马占相思和木荷)比针叶树种(马尾松)生长快。在长期氮沉降环境下, 不同物种生长的差异响应有可能导
致亚热带森林物种组成发生变化。
关键词 生物量, 高氮, 豆科植物, 冠层加氮
引用格式: 刘双娥, 李义勇, 方熊, 黄文娟, 龙凤玲, 刘菊秀 (2015). 不同氮添加量和添加方式对南亚热带4个主要树种幼苗生长的影响. 植物生态学
报, 39, 950–961. doi: 10.17521/cjpe.2015.0092
Effects of the level and regime of nitrogen addition on seedling growth of four major tree
species in subtropical China
LIU Shuang-E1,2, LI Yi-Yong1,2, FANG Xiong1,2, HUANG Wen-Juan1, LONG Feng-Ling1,2, and LIU Ju-Xiu1*
1South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; and 2University of Chinese Academy of Sciences, Beijing 100049,
China
Abstract
Aims Numerous studies have been carried out concerning the effects of atmospheric nitrogen (N) deposition on
forest ecosystems. However, most of previous experiments were conducted by adding N fertilizer to the surface
soil directly. Realistically simulated canopy N deposition and comparison of the effects of soil N addition and
canopy N addition on ecosystems were rare. Our purpose is to better understand the effects of two N addition re-
gimes at different N addition levels on seeding growth in major tree species of subtropical China.
Methods A 2-year pot experiment was conducted, with seedlings of four species (Ormosia pinnata, Acacia
mangium, Schima superba, Pinus massoniana) grown in pots subjected to treatments of three levels (ambient,
medium, and high) and two regimes (in soil vs. on canopy) of N addition, specifically including S-CK (ambient N
addition in soil), S-MN (medium N addition in soil), S-HN (high N addition in soil), C-CK (ambient N addition
on canopy), C-MN (medium N addition on canopy), and C-HN (high N addition on canopy). The total amounts of
added N in the three N levels were 5.6, 15.6 and 20.6 g·m–2·a–1, respectively. Tree basal diameter and tree height
were measured in June and December 2012, and November 2013. All trees were harvested in November 2013,
and then the biomass was calculated according to the dry-mass of roots, shoots and leaves; the root-shoot ratios
刘双娥等: 不同氮添加量和添加方式对南亚热带 4个主要树种幼苗生长的影响 951
doi: 10.17521/cjpe.2015.0092
were calculated.
Important findings N treatments affected seeding growth, along with significant interactive effects among N
addition level, N addition regime and species. Compared to CK, S-MN stimulated the biomass in seedlings of A.
mangium and S. superba, but decreased the tree height and biomass in seedlings of P. massoniana; C-MN in-
creased the biomass in seedlings of A. mangium; S-HN promoted the biomass in seedlings of A. mangium, but
significantly decreased the biomass, basal diameter and tree height in seedlings of P. massoniana (p < 0.01);
C-HN led to the greater growth in seedlings of A. mangium, S. superba and P. massoniana (p < 0.01). N addition
responses were dependent upon plant species: while seedlings in O. pinnata and A. mangium grew faster than S.
superba and P. massoniana under all N treatments, the differences in the growth of S. superba and P. massoniana
seedlings between the two N addition regimes were more pronounced than in O. pinnata and A. mangium seed-
lings. We concluded that legumes (O. pinnata and A. mangium) grew faster than non-legumes (S. superba). And
growth stimulation in broadleaved trees (O. pinnata, A. mangium, and S. superba) by N addition was significantly
greater than in coniferous trees (P. massoniana). Our findings suggest that the relatively high and chronic atmos-
pheric N deposition in subtropical forest ecosystems may lead to changes in species composition.
Key words biomass, high N addition levels, legumes, N addition on the canopy
Citation: Liu SE, Li YY, Fang X, Huang WJ, Long FL, Liu JX (2015). Effects of the level and regime of nitrogen addition on seed-
ling growth of four major tree species in subtropical China. Chinese Journal of Plant Ecology, 39, 950–961. doi: 10.17521/cjpe.2015.
0092
工业革命以来, 由于化石燃料的燃烧、施肥和
其他工业活动向大气中排放大量氮氧化物, 导致温
带和热带地区的氮沉降量急剧增加(Galloway et al.,
2004)。据研究报道, 亚洲地区氮沉降量从1961年的
14 Tg N·a–1增加到2000年的68 Tg N·a–1, 预计到
2030年, 全球氮沉降量将达到105 Tg N·a–1 (Zheng
et al., 2002)。目前, 我国已成为全球第三大氮沉降
区(Galloway & Cowling, 2002), 大气氮沉降量在中
国南方部分森林中达到30–73 kg N·hm–2·a–1 (任仁
等, 2000; Mo et al., 2006)。
氮沉降对陆地森林生态系统的影响引起了科学
家们的关注和深入研究 (George & Seith, 1998;
Gundersen et al., 2006)。早期的氮沉降研究主要集中
在氮沉降严重的欧洲和北美温带森林地区, 如20世
纪80年代在瑞典针叶林进行的长期氮饱和实验
(NITREX)表明氮沉降对森林生态系统结构和功能
产生了严重影响(Gundersen et al., 1998)。氮沉降改
变了生态系统中的氮循环并影响生态系统生产力和
物质能量流动, 从而间接地影响了生态系统碳循环
(Gruber & Galloway, 2008)。大量研究表明: 在氮素
缺乏的森林生态系统中, 氮沉降能提高叶片光合作
用速率, 对植物生物量积累有促进作用, 从而可增
加陆地生态系统的植被碳储量; 而在氮饱和的生态
系统中, 外源性氮输入会抑制植物生长, 减少生态
系统生产力(Nohrstedt, 2001; Magill et al., 2004)。
不同物种对氮沉降的响应也存在差异(Nakaji et
al., 2001; 李德军等, 2003, 2005), 特别是在不同功
能型之间差异更大。氮沉降通过改变植物养分的可
供给性, 有利于适应高氮水平物种生存, 从而改变
物种组成(Bobbink et al., 1998)。豆科植物由于其固
氮作用, 高氮环境有利于其生长(Dyhrman et al.,
2006; 赵亮等, 2011); 不同森林氮沉降模拟实验比
较发现阔叶树种比针叶树种的氮促进效应更大(Xia
& Wan, 2008), 物种间长期的差异响应将导致群落
的物种组成发生变化, 进而改变生态系统结构。
目前, 国内外模拟森林氮沉降的研究多为直接
向土壤表层添加氮, 忽略了氮沉降过程中植物冠层
对氮的吸收和截留。植物冠层直接吸收的这部分氮
对植物生长有重要的作用。有研究表明, 森林生态
系统冠层对大气氮沉降的吸收能满足植物2%–8%
的总氮需求(Boyce et al., 1996)。Wilson (1992)通过
研究两种针叶树冠层对NH4+和NO3–的吸收发现,
叶片能通过质流快速地吸收NH4+, 叶片直接吸收的
无机氮对植物体内氮饱和有重要的贡献; 美国云冷
杉林叶冠的净氮吸收量是1.8–5.4 kg·hm–2·a–1, 这部
分氮会导致植物碳存储量增加250–1 350 kg C·hm–2·
a–1 (Sievering et al., 2000)。由于冠层对氮的吸收和
截留, 真实的冠层氮沉降对植物生长的影响可能并
没有向土壤直接添加氮剧烈, 从而导致已有研究高
估了植物生长对氮的响应, 同时由于冠层直接吸收
952 植物生态学报 Chinese Journal of Plant Ecology 2015, 39 (10): 950–961
www.plant-ecology.com
氮对植物生长有促进作用, 也可能低估了氮对植物
生长的促进作用。不同氮沉降量对生态系统的影响
有差异, 那么不同氮水平下模拟冠层氮添加和土壤
氮添加对植物生长的影响是否存在显著差异, 冠层
施氮是否比土壤施氮对植物生长的促进作用更大?
不同物种对氮添加的响应是否一致?为弄清这些问
题, 我们设置了3个氮添加水平, 每个氮添加水平分
两种施氮方式(幼苗冠层施氮、土壤表层施氮), 模拟
不同氮添加水平下土壤施氮和冠层施氮对南亚热带
4个不同树种幼苗生长的影响, 以揭示不同物种对
氮添加量和氮添加方式的响应差异, 探讨氮沉降量
增加背景下亚热带森林生态系统中物种组成变化,
并为氮沉降量增加背景下南亚热带森林动态及其经
营管理提供参考。
1 材料和方法
1.1 研究区概况
实验地点位于广州市近郊的中国科学院华南植
物园科研区(23.16° N, 113.35° E)。该地属于亚热带
季风气候区, 全年平均可见光辐射总量为4 367.2–
4 597.3 MJ·m–2, 年平均气温21.5 ℃, 年降水量约
1 700 mm, 4–9月的降水量约占全年降水量的80%,
平均相对湿度77%。土壤类型为地带性赤红壤, 植
被类型属于典型的南亚热带季风常绿阔叶林, 其主
要的优势树种是木荷(Schima superba)、黄果厚壳桂
(Cryptocarya concinna)、锥栗(Castanea henryi)。该
地区受工业影响, 大气污染严重, 是我国的高氮沉
降地区 , 2006年试验地的大气氮沉降量为56 kg
N·hm–2·a–1 (Liu et al., 2008)。
1.2 实验设计
本试验参考广州2006年大气氮沉降量(56 kg
N·hm–2·a–1)以及以往类似研究的设计 (Mo et al.,
2006; Liu et al., 2011), 采用裂区试验设计, 设置3个
氮添加水平, 每个氮添加水平分别用2种喷洒方法
(幼苗冠层喷洒和土壤表层喷洒), 共6个实验处理,
每个处理设置6个重复。供试土壤采自华南植物园游
览区季风林表层土壤(0–20 cm), 土壤理化参数背景
值见表1。四种南亚热带主要树种分别是海南红豆
(Ormosia pinnata)、马占相思(Acacia mangium)、木
荷(Schima superba)和马尾松(Pinus massoniana), 其
中海南红豆和马占相思为豆科树种, 木荷和马尾松
为非豆科树种, 马尾松为针叶树种, 其余均为阔叶
树种。
1.3 实验处理
2012年3月29日, 从苗圃地选择株高、基径及生
长状况基本一致的海南红豆、马占相思、木荷和马
尾松幼苗各36株移栽至温室的144个花盆中, 花盆
高30 cm, 上口直径40 cm。幼苗移栽至花盆待缓苗
后进行氮添加处理。6个实验处理分别是: (1)土壤
对照处理 : 背景大气氮沉降量 5.6 g·N·m–2·a–1
(S-CK); (2)土壤中氮处理: 15.6 g·N·m–2·a–1 (S-MN);
(3)土壤高氮处理: 20.6 g·N·m–2·a–1 (S-HN); (4)冠层对
照处理: 背景大气氮沉降量5.6 g N·m–2·a–1 (C-CK);
(5)冠层中氮处理: 15.6 g·N·m–2·a–1 (C-MN); (6)冠层
高氮处理: 20.6 g·N·m–2·a–1 (C-HN)。实验添加的氮均
为硝酸铵(NH4NO3), 从6月1日开始, 每周五将对
照、中氮、高氮处理所需1.85、5.16和6.81 g NH4NO3
分别与4.8 L水混匀后放入花洒中从幼苗顶端和土
壤表层喷洒。
1.4 幼苗基径、株高、生物量测定及计算
分别于2012年6、12月和2013年11月测定所有幼
苗的基径和株高。2013年11月, 所有树苗采用全收
割法进行收割。收割后, 先将根系的泥土洗净, 再按
照粗根(直径> 2 mm)、细根(直径< 2 mm)、茎枝、
叶称取鲜质量, 然后选定各部位单位质量的部分样
品放入60 ℃烘箱内烘干至恒定质量, 分别称其干
物质量, 通过干、鲜质量比计算出整株植物根、茎
枝及叶的干物质量, 得到每株树苗各部位的生物量
和总生物量, 同时计算植株的根冠比。在植物全收
割的同时采集土壤样品, 带回实验室测土壤pH值和
水分系数(附录I)。
1.5 土壤理化参数分析
土壤装盆前全部混合均匀。随机采取部分土壤
样品进行化学分析获得土壤理化参数背景值。土壤
表1 氮添加处理前土壤理化参数背景值(平均值±标准偏差, n = 12)
Table 1 Background values of soil physicochemical properties at beginning of the experiment (mean ± SD, n = 12)
土壤深度
Soil depth (cm)
pH值
pH value
有效磷
Available phosphorus (mg·kg–1)
硝态氮
Nitrate nitrogen (mg·kg–1)
铵态氮
Ammonium nitrogen (mg·kg–1)
有机质
Organic matter (g·kg–1)
0–20 3.99 ± 0.096 0.84 ± 0.072 17.39 ± 1.34 6.01 ± 0.69 22.72 ± 1.20
刘双娥等: 不同氮添加量和添加方式对南亚热带 4个主要树种幼苗生长的影响 953
doi: 10.17521/cjpe.2015.0092
有机质用重铬酸钾氧化-外加热法测定。有效P用
HCl-氟化铵浸提-钼锑抗比色法分析。铵态氮和硝态
氮采用KCl浸提-紫外分光光度计比色法测定。背景
和最后一次土壤样品的pH值采用电极法测定(称取
10 g土加入25 mL去离子水混合均匀)。
1.6 数据处理
所有数据均运用SPSS 17.0统计软件进行分析,
对基径和株高以及生物量进行物种、添氮量和添氮
方式多因素方差分析。对照、中氮和高氮之间以及
土壤和冠层两种氮添加方式间的基径、株高和生物
量(2013年11月)差异显著性用单因素方差分析以及
Duncan氏多重比较, 显著性水平设定为α = 0.05; 土
壤pH值和水分系数分析时, 每2盆土壤混合成一个
样品, n = 3。
2 结果和分析
2.1 不同氮添加量和0添加方式对4种不同乡土树
种基径与树高的影响
经过两个生长季, 4种幼苗的株高和基径在物种
间差异显著(p < 0.001), 所有氮处理下, 海南红豆和
马占相思的株高和基径均高于木荷和马尾松。并且
氮添加量、添加方式和物种三因素间存在着明显的
交互效应(p < 0.001)(表2)。不同氮添加量对基径和
株高的影响有差异, 与对照(CK)相比, S-MN仅降低
了马尾松的株高, 对其他物种没有影响, S-HN降低
了海南红豆的基径以及马尾松的株高和基径 ;
C-MN对4个树种影响不明显, C-HN处理明显促进
了木荷和马尾松的基径和株高(图1, 图2)。
两种氮添加方式间海南红豆和马占相思的基径
和株高没有差异, 但木荷和马尾松的株高和基径差
异较大。木荷在CK、MN、HN 3个氮添加水平下, 冠
层氮添加的基径和株高均高于土壤氮添加, 冠层氮
添加比土壤氮添加更能促进木荷的生长; 马尾松在
CK和MN处理下, 土壤氮添加的株高和基径明显高
于冠层氮添加, HN处理下则相反(图1, 图2)。
2.2 不同氮添加量和添加方式对4种不同乡土树种
总生物量及其分配的影响
总生物量在物种间的差异也极为明显 (F =
122.901, p < 0.001)。所有氮处理下, 海南红豆和马
占相思总生物量积累均高于木荷和马尾松。总生物
量在不同氮添加量间差异明显, 且氮添加量、添加
方式和物种三因素间存在着明显的交互效应(p <
0.001) (表2)。与CK相比, S-MN增加了海南红豆、马
占相思和木荷的总生物量, 明显降低了马尾松的总
生物量(p < 0.01), C-MN仅增加了马占相思的总生
物量, 对其他3个树种幼苗没有影响; S-HN增加了
马占相思的总生物量, 但显著降低了马尾松总生物
量(p < 0.01), C-HN明显增加了马占相思和马尾松的
总生物量。总生物量在氮添加方式之间的响应差异
与基径、株高基本一致(图3)。
表2 氮添加量和氮添加方式对4种树种幼苗生长的影响(三因素方差分析)
Table 2 Effects of N addition level and regime on seedling growth in four major tree species (three-way ANOVA)
基径
Basal diameter
株高
Tree height
生物量
Biomass
土壤pH
Soil pH
主要因素及相互作用
Main factors and interactions
F and p values d.f. F and p values d.f. F and p values d.f. F and p values d.f.
处理水平
Level
6.721
0.002
2 4.013
0.021
2 3.608
0.039
2 70.555
<0.001
2
施氮方式
Regime
0.906
0.344
1 0.544
0.463
1 6.421
0.017
2 107.545
<0.001
1
物种
Species
48.661
<0.001
3 386.887
<0.001
3 122.901
<0.001
3 31.299
<0.001
3
水平×施氮方式
Level × regime
19.591
<0.001
2 1.799
0.171
2 12.949
<0.001
2 7.314
0.002
3
水平×物种
Level × species
5.293
<0.001
6 2.088
0.062
6 12.266
<0.001
6 1.681
0.146
6
施氮方式×物种
Regime × species
7.207
<0.001
3 8.017
<0.001
3 11.592
<0.001
3 3.458
0.023
3
水平×施氮方式×物种
Level × regime × species
9.227
<0.001
6 1.673
0.136
6 10.981
<0.001
6 5.313
<0.001
6
误差 Error 95 95 103 48
表中数据为4个树种的基径、株高、生物量和土壤pH三因素(氮添加水平、氮添加方式和物种)方差分析及交互作用下t检验的F值、p值以及自由度, 加
粗字体的p值均为差异显著(p < 0.05)。
Data in the table are F values, degrees of freedom (d.f.) and p values of t-test for basal diameter, tree height, biomass, soil pH in four major tree species in
three-way ANOVA of N addition level, N addition regime, and species. p-values with bold indicate significant differences (p < 0.05).
954 植物生态学报 Chinese Journal of Plant Ecology 2015, 39 (10): 950–961
www.plant-ecology.com
图1 不同氮添加量和氮添加方式对幼苗基径的影响(平均值±标准偏差)。不同小写字母(a, b)和大写字母(A, B)分别表示土壤
氮添加和冠层氮添加下低氮、中氮、高氮处理间差异显著(p < 0.05); *表示两种施氮方式间有差异(Duncan多重比较; * p < 0.05,
** p < 0.01)。CK, 对照处理; HN, 高氮处理; MN, 中氮处理。CN, 冠层氮添加; SN, 土壤氮添加。AM, 马占相思; OP, 海南红
豆; PM, 马尾松; SS, 木荷。
Fig. 1 Effects of N addition level and regime on tree basal diameter in four tree species (mean ± SD). Different lowercase letters (a,
b) and capital letters (A, B) above the error bars indicate significant differences among N addition levels in soil and on canopy, re-
spectively, in each species (p < 0.05); * above the error bars indicate significant difference between two N addition regimes (Duncan
multiple range test; * p < 0.05, ** p < 0.01). CK, ambient N addition; HN, high N addition; MN, medium N addition. CN, N addition
on canopy; SN, N addition in soil. AM, Acacia mangium; OP, Ormosia pinnata; PM, Pinus massoniana; SS, Schima superba.
不同氮添加量和氮添加方式对4个树种粗根和
茎生物量积累的影响与总生物量一致, 但对叶和细
根生物量影响更明显(图4)。其中, S-HN明显降低了
海南红豆的细根生物量, 增加了其叶生物量; 4个树
种C-HN细根生物量均高于S-HN细根生物量。
3 讨论
3.1 不同氮添加量对植物幼苗生长的影响
已有研究表明, 在氮缺乏或尚未饱和的生态系
统中, 适量的氮添加会增加土壤有效氮, 对植物生
长有促进作用, 但长期过量的氮输入反而会降低植
物的初级生产力, 这是由于高氮量会导致土壤酸
化、营养元素不平衡, 不利于幼苗的生长(Aber et
al., 1998; Bauer et al., 2004; Lu et al., 2014)。与对照
相比, 土壤和冠层MN、HN均促进了木荷和马占相
思的生长, 但S-HN明显抑制了马尾松的生长; 海南
红豆、木荷和马尾松S-MN下的生物量明显高于
S-HN, 说明土壤中氮比高氮对植物生长有利。其他
一些氮添加实验也得到类似的结果, 如: Magill等
(2004)在哈佛森林氮处理实验中, 松林生物量随着
氮输入量的增多而减少; 高氮添加抑制了日本赤松
(Pinus densiflora)幼苗的生长(Nakaji et al., 2001);
李德军等(2004)研究了氮添加对南亚热带木荷、黄
果厚壳桂2种常绿阔叶树种幼苗生长的影响, 发现
中等程度的氮处理促进了幼苗的生长, 而高氮处理
对幼苗生长产生了负面效应。
本研究中, 叶和细根生物量对氮添加量的响应
比较明显。有研究表明氮添加会改变植株生物量的
分配进而影响幼苗的生长, 一定量的氮添加使土壤
有效氮含量增加 , 促进植物地上部分的积累
(Flückiger & Braun, 1998; 段洪浪等, 2009)。本实验
中, S-MN增加了海南红豆、马占相思和木荷的叶生
刘双娥等: 不同氮添加量和添加方式对南亚热带 4个主要树种幼苗生长的影响 955
doi: 10.17521/cjpe.2015.0092
图2 不同氮添加量和氮添加方式对幼苗株高的影响(平均值±标准偏差)。不同小写字母(a, b)和大写字母(A, B)分别表示土壤
氮添加和冠层氮添加下低氮、中氮、高氮处理间差异显著(p < 0.05); *表示两种施氮方式间有差异(Duncan多重比较; * p < 0.05,
** p < 0.01)。CK, 对照处理; HN, 高氮处理; MN, 中氮处理。CN, 冠层氮添加; SN, 土壤氮添加。AM, 马占相思; OP, 海南红
豆; PM, 马尾松; SS, 木荷。
Fig. 2 Effects of N addition level and regime on tree height in four tree species (mean ± SD). Different lowercase letters (a, b) and
capital letters (A, B) above the error bars indicate significant differences among N addition levels in soil and on canopy, respectively,
in each species (p < 0.05); * above the error bars indicate significant differences between two N addition regimes (Duncan multiple
range test; * p < 0.05, ** p < 0.01). CK, ambient N addition; HN, high N addition; MN, medium N addition. CN, N addition on can-
opy; SN, N addition in soil. AM, Acacia mangium; OP, Ormosia pinnata; PM, Pinus massoniana; SS, Schima superba.
表3 不同氮添加量和氮添加方式下幼苗的根冠比(平均值±标准偏差)
Table 3 Root-shoot ratios under different nitrogen (N) treatments (mean ± SD)
冠层施N N addition on canopy 土壤施N N addition in soil 物种
Species CK MN HN CK MN HN
海南红豆 Ormosia pinnata 0.275 ± 0.029 0.307 ± 0.003 0.315 ± 0.067 0.453 ± 0.103a 0.332 ± 0.018ab 0.253 ± 0.009b
马占相思 Acacia mangium 0.251 ± 0.071 0.222 ± 0.039 0.317 ± 0.059 0.262 ± 0.059 0.235 ± 0.005 0.391 ± 0.175
木荷 Schima superba 0.514 ± 0.128 0.489 ± 0.021 0.754 ± 0.241 0.575 ± 0.055 0.544 ± 0.124 0.608 ± 0.008
马尾松 Pinus massoniana 0.336 ± 0.119 0.277 ± 0.021 0.223 ± 0.070 0.170 ± 0.035b 0.299 ± 0.075ab 0.343 ± 0.003a
表中不同的小写字母(a, b)表示同一施氮方式下3种氮添加量之间差异显著(Duncan多重比较; p < 0.05)。CK, 对照处理5.6 g N·m–2·a–1; HN, 高氮处理20.6
g N·m–2·a–1; MN, 中氮处理15.6 g N·m–2·a–1。
Different lowercase letters (a, b) indicate significant differences among N addition levels within the same regimes (Duncan multiple range test; p < 0.05). CK,
ambient N addition 5.6 g N·m–2·a–1; HN, high N addition 20.6 g N·m–2·a–1 ; MN, medium N addition 15.6 g N·m–2·a–1.
物量, 说明适量的氮添加有效地促进了地上部分生
物量的积累, 根冠比下降(表3)。NITREX实验发现
氮沉降在一定程度上对地上部分的生长有促进作
用, 但同时对根系的生长不利(Persson et al., 1998)。
Mo等(2008)在广东省鼎湖山自然保护区3种成熟森
林中进行的氮添加实验表明: 过量氮沉降危害根系
生长, 不利于细根生物量的生长和养分的吸收。本
研究中, S-HN降低了海南红豆、马尾松的根生物量,
尤其是细根生物量明显减少(p < 0.05)(图4), 可能原
因是土壤高氮引起的土壤酸化不利于细根的生长
956 植物生态学报 Chinese Journal of Plant Ecology 2015, 39 (10): 950–961
www.plant-ecology.com
图3 不同氮添加量和氮添加方式对幼苗生物量的影响(平均值±标准偏差)。不同小写字母(a, b)和大写字母(A, B)分别表示土
壤氮添加和冠层氮添加下低氮、中氮、高氮处理间差异显著(p < 0.05); *表示两种施氮方式间有差异(Duncan多重比较; * p <
0.05, ** p < 0.01)。CK, 对照处理; HN, 高氮处理; MN, 中氮处理。CN, 冠层氮添加; SN, 土壤氮添加。AM, 马占相思; OP, 海
南红豆; PM, 马尾松; SS, 木荷。
Fig. 3 Effects of N addition level and regime on biomass in four tree species (mean ± SD). Different lowercase letters (a, b) and
capital letters (A, B) above the error bars indicate significant differences among N addition levels in soil and on canopy, respectively,
in each species (p < 0.05); * above the error bars indicate significant differences between two N addition regimes (Duncan multiple
range test; * p < 0.05, ** p < 0.01). CK, ambient N addition; HN, high N addition; MN, medium N addition. CN, N addition on can-
opy; SN, N addition in soil. AM, Acacia mangium; OP, Ormosia pinnata; PM, Pinus massoniana; SS, Schima superba.
(Nakaji et al., 2001)。
3.2 不同氮添加量下两种氮添加方式对幼苗生长
的影响
本研究结果表明, 不同氮添加方式对幼苗生长
的影响不同, 特别是生物量差异明显(p = 0.017), 且
物种、氮添加量和施氮方式间存在着明显的交互效
应(表2), 这表明氮添加方式对幼苗生长的影响因
不同物种和不同氮添加量而异。不同氮添加方式对
固氮树种海南红豆和马占相思的生长没有影响 ,
而对非固氮树种木荷和马尾松的基径、株高和生物
量影响较大。木荷在3个氮添加水平下, 冠层施氮
幼苗的生长均明显快于土壤施氮幼苗的生长; 马
尾松在HN水平下, 冠层施氮促进了幼苗的生长,
而土壤施氮抑制了幼苗的生长。冠层施氮促进植物
生长的作用大于土壤施氮, 可能包括两个方面的
机制: 一方面, 植物叶冠能直接吸收一部分氮促进
植物的生长, Tomaszewski等(2003)研究了科罗拉多
亚高山森林冠层对大气中氮的吸收, 结果表明在生
长季冠层能吸收氮2–3 kg·hm–2, 占叶片生长所需氮
的10%–15%, Sievering等(2007)在美国西部针叶林
的氮沉降研究表明生长季约20%净生态系统碳交换
量(NEE)是由冠层吸收氮导致的; 另一方面, Morris
等(2003)也指出冠层截留后的穿透雨中NH4+和NO3–
分别减少了73%和47%, 到达土壤中的无机氮明显
减少, 能够缓和土壤氮含量过高, 土壤酸化程度
较轻。
两种氮添加方式对幼苗细根和叶生物量的影响
不同。HN水平下, 4个树种细根生物量在土壤施氮方
式下均低于冠层施氮, 当土壤氮过量时, 植物体会
减少细根生物量以减少氮的吸收(Zhu et al., 2013);
刘双娥等: 不同氮添加量和添加方式对南亚热带 4个主要树种幼苗生长的影响 957
doi: 10.17521/cjpe.2015.0092
图4 不同氮添加量和氮添加方式下对幼苗各部位(粗根、细根、茎和叶)生物量积累的影响(平均值±标准差)。不同小写字母(a,
b)和大写字母(A, B)分别表示土壤氮添加和冠层氮添加下低氮、中氮、高氮处理间差异显著(p < 0.05); *表示两种施氮方式间
有差异(Duncan多重比较; * p < 0.05, ** p < 0.01)。CK, 对照处理; HN, 高氮处理; MN, 中氮处理。CN, 冠层氮添加; SN, 土壤
氮添加。AM, 马占相思; OP, 海南红豆; PM, 马尾松; SS, 木荷。
Fig. 4 Effects of N addition level and regime on biomass accumulation in leaves, stem and coarse-roots and fine-roots (mean ± SD).
Different lowercase letters (a, b) and capital letters (A, B) above the error bars indicate significant differences among N addition lev-
els in soil and on canopy, respectively, in each species (p < 0.05); * above the error bars indicate significant differences between two
N addition regimes (Duncan multiple range test; * p < 0.05, ** p < 0.01). CK, ambient N addition; HN, high N addition; MN, me-
dium N addition. CN, N addition on canopy; SN, N addition in soil. AM, Acacia mangium; OP, Ormosia pinnata; PM, Pinus mas-
soniana; SS, Schima superba.
两种添加方式对幼苗叶生物量的影响差异因物种而
异, 这可能与不同树种叶片氮吸收特性和叶片对氮
添加的敏感度有关。以上结果表明: 对于非固氮植
物, 冠层氮添加比土壤氮添加对植物生长的促进效
应更大, 植物冠层直接吸收的这部分氮对植物生长
的促进作用很重要, 但被以前的研究所忽略, 可能
低估了氮沉降对植物生长的正效应。向土壤直接添
加高氮也夸大了对植物生长的负面效应(马尾松),
从而导致已有氮沉降研究高估了植物生长对高氮的
响应。
3.3 不同树种对氮添加量和氮添加方式的响应
差异
物种因本身的氮利用特性不同, 对不同氮水平
的适应能力存在差异。长期的氮沉降会改变物种的
组成, 从而影响群落结构, 降低森林植物的多样性,
最终影响群落的演替(Robbink et al., 1998; Suding et
al., 2005; Liu et al., 2011)。氮沉降效应在不同功能型
之间差异显著, 有研究表明豆科植物在高氮环境下
比非豆科植物更有优势(Dyhrman et al., 2006)。本研
究中4个树种对氮处理的响应差异极显著(p < 0.001),
958 植物生态学报 Chinese Journal of Plant Ecology 2015, 39 (10): 950–961
www.plant-ecology.com
图5 不同氮添加量和氮添加方式对土壤pH值的影响(平均值±标准偏差)。不同小写字母(a, b)和大写字母(A, B)分别表示土壤
氮添加和冠层氮添加下低氮、中氮、高氮处理间差异显著(p < 0.05); *表示两种施氮方式间有差异(Duncan多重比较; * p < 0.05,
** p < 0.01)。CK, 对照处理; HN, 高氮处理; MN, 中氮处理。CN, 冠层氮添加; SN, 土壤氮添加。AM, 马占相思; OP, 海南红
豆; PM, 马尾松; SS, 木荷。
Fig. 5 Effects of N addition level and regime on soil pH value (mean ± SD). Different lowercase letters (a, b) and capital letters (A,
B) above the error bars indicate significant differences among N addition levels in soil and on canopy, respectively, in each species (p
< 0.05); * above the error bars indicate significant differences between two N addition regimes (Duncan multiple range test; * p <
0.05, ** p < 0.01). CK, ambient N addition; HN, high N addition; MN, medium N addition. CN, N addition on canopy; SN, N addi-
tion in soil. AM, Acacia mangium; OP, Ormosia pinnata; PM, Pinus massoniana; SS, Schima superba.
表4 不同树种幼苗生长对氮添加方式和氮添加量响应差异(Duncan多重比较)
Table 4 Differential responses of seedling growth to N addition regime and level among different tree seedlings (Duncan multiple range test)
土壤施N N addition in soil 冠层施N N addition on canopy
CK MN HN CK MN HN
豆科与非豆科相比
Legumes versus non-legumes
基径
Base diameter
18.450
0.001
36.161
<0.001
5.461
0.038
5.747
0.03
15.424
0.002
3.38
0.087
株高
Tree height
46.039
<0.001
32.859
<0.001
8.979
0.011
16.937
0.001
9.629
0.008
9.111
0.009
生物量
Biomass
9.126
0.029
21.174
0.006
30.829
0.002
0.932
0.379
11.908
0.026
6.263
0.046
阔叶与针叶相比
Broadleaf versus conifers
基径
Basal diameter
0.679
0.338
1.262
0.276
24.355
<0.001
23.799
<0.001
32.911
<0.001
1.297
0.269
株高
Tree height
2.516
0.129
6.264
0.022
7.065
0.018
11.620
0.003
17.643
<0.001
10.767
0.004
生物量
Biomass
0.110
0.750
10.299
0.013
8.170
0.017
16.323
0.004
33.324
0.001
1.11
0.323
表中数值为基径、株高、生物量在相同添加方式和氮添加量下豆科(海南红豆、马占相思)与非豆科(木荷), 阔叶树种(海南红豆、马占相思、木荷)与针
叶树种(马尾松)间多重比较的F值和p值, 表中加粗字体的p值均为差异显著(p < 0.05)。CK, 对照处理; HN, 高氮处理; MN, 中氮处理。
Data in the table are F values and p values for basal diameter, tree height, and biomass (Duncan multiple range test) for comparison between Legumes (Ormosia
pinnata and Acacia mangium) and non-legumes (Schima superba), and between broadleaf (Ormosia pinnata, Acacia mangium, and Schima superba) and coni-
fers (Pinus massoniana) within same N addition levels and regimes. p-values with bold indicate significant differences (p < 0.05). CK, ambient N addition; HN,
high N addition; MN, medium N addition.
刘双娥等: 不同氮添加量和添加方式对南亚热带 4个主要树种幼苗生长的影响 959
doi: 10.17521/cjpe.2015.0092
同为阔叶树种的豆科植物(海南红豆、马占相思)和
非豆科植物(木荷)之间差异明显(表4), 在所有氮添
加处理下, 豆科植物的株高、基径和总生物量均大
于非豆科植物, 豆科植物由于生物固氮作用比非豆
科植物在氮利用上有优势; 同时豆科植物还可以利
用细胞外的磷酸酯酶分解有机P, 从而提高P的利用
率(Houlton et al., 2008)。不同氮添加量和氮添加方
式对海南红豆生长无显著差异, 海南红豆是典型的
固氮树种, 具有根瘤固氮作用, 氮素的增加并不能
显著促进植物的生长; 但同为豆科植物的马占相
思, 中氮和高氮促进了其幼苗生长, 且高氮比中氮
的促进作用更大, 马占相思在氮沉降增加背景下比
其他几个乡土树种生长更快, 这说明豆科植物对氮
的响应机制是复杂的。
不同氮添加量和氮添加方式对非豆科植物影响
很大, 中氮和高氮均促进了木荷幼苗的生长, 且冠
层施氮对植物生长的促进作用比土壤施氮更大。马
尾松(针叶)幼苗在S-HN处理下植物生长受到明显的
抑制, 其幼苗死亡率达到50%, 土壤高氮不利于马
尾松幼苗的生长可能与土壤酸化有关, 土壤pH值随
着氮添加量增加而下降, 马尾松S-HN处理下pH值
最低, 仅为3.52 (图5), 氮沉降引起的土壤酸化导致
可利用性P以及其他阳离子的流失使生产力下降
(Matson et al., 1999)。庞丽等(2014)通过氮添加对马
尾松幼苗的生长研究也表明氮处理增加了马尾松根
系有机酸和酸性磷酸酶的分泌, 使植株极度缺磷,
抑制了幼苗的生长。在氮沉降量增加的背景下, 阔
叶树种比针叶树种在生长上更有优势。其他研究也
得到相似的结论, 如Xia和Wan (2008)经过Meta分析
表明氮沉降对阔叶树种生长的促进作用比针叶树种
更大; Magill等(2004)在美国哈佛实验林的研究也证
实了氮素对植物生长的影响因森林类型、植物种类
而不同。不同树种对氮处理响应差异的原因是复杂
的, 与物种本身的氮利用特性、氮处理时间、氮沉
降量、植株生长的自然环境、生长策略等有关, 这
有待于我们今后做进一步研究。
基金项目 广东省林业科技创新专项资金(2012-
KJCX019-02)和国家自然科学基金(31370530)。
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责任编委: 杨元合 责任编辑: 王 葳
附录I 两种氮添加方式下土壤含水量(平均值±标准偏差)
Supplement I Soil water content (%) under two N addition regimes (mean ± SD)
对照 Ambient N addition 中氮 Medium N addition 高氮 High N addition 物种
Species 土壤施氮
SN
冠层施氮
CN
土壤施氮
SN
冠层施氮
CN
土壤施氮
SN
冠层施氮
CN
海南红豆 Ormosia pinnata 17.11 ± 1.68 14.07 ± 1.40 18.28 ± 1.08 15.74 ± 1.99 17.06 ± 1.25 16.67 ± 1.01
马占相思 Acacia mangium 17.63 ± 2.17 13.87 ± 2.48 19.69 ± 0.39a 13.83 ± 2.74b 16.65 ± 1.12 14.33 ± 3.51
木荷 Schima superba 18.14 ± 1.13 16.73 ± 1.61 19.18 ± 0.80a 16.03 ± 1.68b 17.22 ± 0.81 15.70 ± 0.60
马尾松 Pinus massoniana 17.39 ± 2.49 15.52 ± 1.72 18.03 ± 1.18 17.28 ± 0.33 17.60 ± 0.74 15.85 ± 0.93
表中不同的小写字母(a, b)表示两种氮添加方式间有差异(p < 0.05)。
Different lowercase letters (a, b) indicate significant differences between two N addition regimes within same N addition levels (Duncan multiple range test; p <
0.05); SN, N addition in soil; CN, N addition on canopy.