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作为我国二级保护物种之一的毛红椿(Toona ciliata Roem.var.pubescens(Franch.)Hand.-Mazz.[1],因其速生、珍贵、濒危,近年来越来越受到学者关注。目前,在毛红椿天然种群生态特征[2]、群落结构特征[3]、群体遗传结构[4-5]、结实特性及生殖力[6-7]、种子萌发的影响因素[8-9]和毛红椿资源保护对策和育苗技术[10-12]等方面开展了研究,本课题组探讨了天然林毛红椿种子库、林下幼苗数量、基株个体大小和枯落物厚薄等生境因素对毛红椿天然更新的影响[2, 6, 9]。植物种群更新限制主要来自三种机制:一是种子可获得性低,导致有效传播率低,引起种源限制;二是种子不能扩散到合适地点而受到传播限制;三是扩散到微生境后,受生物和非生物因素影响而不能生长成幼树,导致建成限制[13-15]。微生境生态因子包含多种限制因素,如土壤、水分、光照、枯落物、植物邻居等,这些因子决定着幼树的建成,不同种植物的主导因子存在差异[16]。土壤作为林木生长的重要生态因子,其物理、化学及生物学性质直接影响森林的更新过程[17],森林群落植物的组成及分布,还与其森林系统根系分泌物的化感效应存在密切联系[18]。本文在毛红椿天然优势群落中,研究根区土壤、土壤真菌及土壤性质等对种子萌发和幼苗建成的影响,研究结果有助于寻找制约该物种生存和发展的主要因子,更好理解毛红椿天然更新的障碍因素,为珍稀阔叶树种毛红椿致濒提供有效的保护策略和保育技术。
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2015年3月,在江西九连山国家级自然保护区大丘田、电站和虾公塘等3个毛红椿天然林群落,以较小径级基株受邻体干扰的有效距离10.0 m为限[2],在距离毛红椿成年大树2.5、5.0、7.5 m树根附近采集除去枯落物0~10 cm表层土壤作为根区土,以远离大树25 m以外的土壤作为非根区土带回实验室,每个群落采取3株毛红椿9个根区土样和3个非根区土样,共36个土样,每个土样采集2.0 kg,分成3份,分别用于播种、土壤理化分析和微生物检测。以新鲜河沙、沙壤土、菜地土为对照,其中,沙壤土为细沙与黄壤土按7∶3均匀混合。供试种子采自九连山毛红椿天然林群落母树,千粒质量7.345 g。3个群落及母树基本情况见表 1。
表 1 九连山毛红椿天然林群落及母树基本情况
Table 1. Geographic location and the mother trees of nature populations T.ciliata var.pubescens stands in Jiulianshan
群落
Stand地形
Geomorphic types经度(E)
Longitude纬度(N)
Latitude海拔
Altitude/m毛红椿相对密度
Relative density of Toona ciliate var. pubescens/%母树平均高度
Mean height of the mother tree/m母树平均胸径
DHB of the mother tree/cm大丘田Daqiutian 山谷Valley 114°26′ 24°34′ 501 37.93 23.5 40.0 电站Dianzhan 山坡Hillside 114°30′ 24°36′ 575 49.22 21.0 29.8 虾公塘Xiagongtang 山谷Valley 114°27′ 24°31′ 760 22.22 22.5 31.9 -
在不同群落土壤中,毛红椿种子的萌发趋势基本一致,即第4天开始萌发,第8~10天达到高峰,第10天全部种子发芽结束。幼苗数呈先上升后下降的趋势,林地根区土幼苗数下降速度比非根区土的快,18 d以后非根区土幼苗数均比根区土的高(图 1)。
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表 2表明:种子发芽率为62.33%~77.67%,幼苗保存率为15.70%~ 67.14%,各群落2.5、5.0、7.5 m处根区土毛红椿幼苗保存率均低于非根区土。方差分析表明:大丘田、电站和虾公塘3个群落间及不同距离根区间种子发芽率的差异均不显著;大丘田、电站和虾公塘不同距离土壤间幼苗保存率差异显著(F=10.222,P=0.004;F=4.172,P=0.047;F=4.794,P=0.034)。多重比较结果(表 2)表明:大丘田和虾公塘群落2.5、5.0、7.5 m处根区土的毛红椿幼苗保存率均显著低于非根区土的;电站2.5 m处根区土的幼苗保存率显著低于非根区土的,2.5、5.0、7.5 m处根区土间的幼苗保存率差异不显著;2.5、5.0、7.5 m处根区土的毛红椿幼苗保存率总均值间差异不显著,但与非根区土间差异极显著(F=15.135,P=0.000<0.01)。以上结果表明:毛红椿根区土、非根区土种子发芽率差异不显著,而根区土与非根区土间幼苗保存率差异显著,说明根区土对毛红椿幼苗保存有较大影响;2.5、5.0、7.5 m处根区土毛红椿种子发芽率及幼苗保存率总均值间差异不显著,说明在距母树一定周径范围内根区土对毛红椿种子发芽和幼苗保存影响一致。
表 2 距毛红椿母树不同距离的种子发芽率与幼苗保存率
Table 2. Seedling survival rate and seed germination rate of T.ciliata var. pubescens in different distances from the mother tree
离母树距离
Distances from the mother tree发芽率seed germination rate/% 保存率seedling survival rate/% 大丘田
Daqiutian虾公塘
Xiagongtang电站
Dianzhan总均值
Total mean大丘田
Daqiutian虾公塘
Xiagongtang电站
Dianzhan总均值
Total mean2.5 m根区2.5 m root zone 77.00±6.25a 63.33±14.98a 77.67±7.09a 72.67±11.29a 15.70±18.24c 38.84±4.85 b 27.82±14.35b 27.45±15.52B 5.0 m根区5.0 m root zone 66.33±5.13a 73.67±6.35 a 73.67±7.64a 71.22±6.47a 40.89±3.91b 25.77±16.19b 34.54±22.59ab 33.73±15.50B 7.5 m根区7.5 m root zone 62.33±4.93a 70.33±9.87a 77.67±6.51a 70.11±9.23a 35.00±5.32bc 32.52±20.08b 40.92±10.99ab 36.14±12.33B 非根区Non-root zone 71.00±9.85a 77.33±1.51a 72.00±2.65a 73.44±5.94a 64.03±9.42a 63.80±0.61a 67.14±3.88a 64.99±5.35A 注:同列不同小写字母间表示差异显著(P<0.05),同列不同大写字母间表示差异极显著(P<0.01),下同。
Note:Different lowercase letter along the column indicate significant difference at P<0.05,Different capital letter along the column indicate extremely significant difference at P<0.01,the same as below.表 3表明:林地土(根区土、非根区土)种子发芽率的总均值(71.86%)与非林地土(河沙、沙壤土、菜地土)对照的种子发芽率总均值(72.67%)差异不显著,但林地土的保存率总均值(40.58%)极显著低于非林地土的(70.02%)(F=5.352,df=49,P=0.000<0.01);林地根区土与非根区土的种子发芽率差异不显著,但幼苗保存率差异极显著(F=30.074,P=0.000<0.01),林地根区土幼苗存活率较低,仅32.44%。以上结果进一步表明,林地土毛红椿幼苗保存率低的原因主要来源于根区土的影响。
表 3 不同类型土壤毛红椿种子发芽率与幼苗保存率
Table 3. Seedling survival rate and seed germination rate of T.ciliata var. pubescens in different soils
土壤类型Soil type 发芽率Seed germination rate/% 保存率Seedling survival rate/% 均值Mean 总均值Total mean 均值Mean 总均值Total mean 林地土Forest soil 根区土Root zone soil 71.33±8.96a 71.86±8.78a 32.44±14.45B 40.58±19.13B 非根区土Non-root zone soil 73.44±5.94a 64.99±5.35A 非林地土Non-forest soil 河沙River sand 62.00±7.58b 72.67±9.29a 74.74±11.04A 70.02±5.43A 沙壤土Sandy soil 77.00±7.58a 64.09±22.31A 菜地土Vegetable soil 79.00±10.25a 71.24±5.44A -
鉴于非根区土壤幼苗保存率与3种非林地土均差异不显著,故探讨林地土壤(根区土和非根区土)性状与毛红椿幼苗保存率间的关系。
九连山毛红椿林地土部分理化性质和酶活性见表 4。独立样本t检验结果表明:毛红椿根区土的pH值显著高于非根区土的(F=0.049,df=34,P=0.016<0.05),但毛红椿根区土和非根区土的含水率、蔗糖酶、纤维素酶、有机质、铵态氮、硝态氮差异不显著。
表 4 九连山林地土壤的理化性质和酶活性
Table 4. Enzyme activity and physical-chemical properties of Jiulianshan forest soil
土壤性状
Soil traits根区Root zone 非根区Non-root zone 大丘田Daqiutian 虾公塘Xiagongtang 电站Dianzhan 大丘田Daqiutian 虾公塘Xiagongtang 电站Dianzhan 含水率Water content/% 32.57±1.42 34.97±3.82 26.34±3.84 37.67±8.72 39.24±3.65 28.60±3.00 pH值pH value 5.39±0.29 5.40±0.22 6.09±0.14 5.11±0.29 4.90±1.83 5.68±0.36 有机质SOM/(g·kg-1) 15.16±5.44 10.56±0.48 7.40±2.34 17.00±4.37 11.36±0.51 9.36±0.54 蔗糖酶Invertase/(mg·g-1) 4.34±3.24 3.17±0.99 5.61±3.81 6.40±2.37 5.33±3.66 3.72±2.98 纤维素酶Cellulose/(mg·g-1) 1.38±0.86 1.92±0.57 1.41±0.85 7.86±0.79 2.38±0.19 0.95±0.26 铵态氮(NH4+)N/(mg·kg-1) 13.60±5.86 32.55±2.82 21.01±10.33 21.13±11.03 33.13±1.96 16.71±7.43 硝态氮(NO3-)N/(mg·kg-1) 1.61±0.61 1.63±0.28 1.34±0.39 1.86±0.65 1.71±0.40 1.13±0.42 相关分析结果(表 5)表明:不同类型土壤指标与种子发芽率和幼苗保存率相关不显著。
表 5 九连山林地土壤理化性质、酶活性与种子发芽率和幼苗保存率相关分析
Table 5. Correlation of seed germination rate, seedling survival rate and soil physical-chemical properties, enzyme activity of Jiulianshan forest soil
项目Items 相关分析
Correlation含水率
Water contentpH值
pH value有机质
SOM蔗糖酶
Invertase纤维素酶
Cellulose铵态氮
(NH4+)N硝态氮
(NO3-)N发芽率
Seed germination rate皮尔森相关系数Pearson Correlation 0.127 0.033 -0.063 0.210 -0.022 0.054 -0.038 显著性Sig. 0.462 0.848 0.716 0.218 0.900 0.758 0.830 样本数N 36 36 36 36 36 35 35 保存率
Seedling survival rate皮尔森相关系数Pearson Correlation 0.038 -0.107 -0.104 0.114 0.031 0.037 -0.070 显著性Sig. 0.824 0.536 0.546 0.509 0.858 0.832 0.687 样本数N 36 36 36 36 36 35 35 -
根区土死亡的幼苗表现为苗茎或其叶子着生处感染褐化干枯而死,疑似真菌感染所致。因此,从幼苗死亡率较高的根区土壤中分离出真菌(RS2和RS3来自大丘田群落距毛红椿大树2.5 m处根区土壤,RS5来自虾公塘群落距毛红椿大树5 m处根区土壤),分别用其水(RS2W、RS3W、RS5W)或毛红椿根系分泌物孢子悬液(RS2R、RS3R、RS5R)对毛红椿健康幼苗灌根接种,无菌水(W)和根系分泌物(R)为对照,幼苗保存结果见图 2。
图 2 根区土壤真菌孢子悬浮液对毛红椿幼苗保存率的影响
Figure 2. Effect of the soil-borne fungal spore suspension on the survival of T. ciliata var. pubescens seedlings
方差分析结果表明:处理间差异极显著(F=20.802,df=7,P=0.000<0.01)。多重比较表明:2个对照间差异不显著,无菌水悬浮液RS2W、RS5W和根系分泌物悬浮液RS2R、RS5R处理的幼苗保存率均显著低于其相应的对照;RS3W和RS3R孢子悬浮液处理的幼苗保存率与无菌水(W)和根系分泌物(R)的差异不显著;RS2R处理的幼苗保存率显著低于RS2W处理的,RS5R处理的幼苗保存率低于RS5W处理的,但差异不显著(图 2)。以上结果表明:RS2和RS5真菌可能为毛红椿潜在致病菌,且毛红椿根系分泌物能显著增强RS2真菌的致病力。
林地土壤及其真菌对毛红椿种子发芽及幼苗保存的影响
Effects of Forest Soil and Soil-borne Fungi on Seed Germination and Seedling Survival of Toona ciliata var. pubescens
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摘要:
目的 通过不同群落毛红椿天然林林地土壤及其真菌对种子萌发和幼苗存活影响的研究,探讨影响毛红椿天然更新的障碍因素。 方法 在江西九连山国家级自然保护区内的3个毛红椿天然优势群落中,分别取距离毛红椿母树3个不同距离(2.5、5.0、7.5 m)处的根区土壤和远离毛红椿母树(25 m以外)的非根区土壤,以非林地土为对照开展室内模拟播种和以根区土壤真菌的水或根系分泌物悬液对毛红椿幼苗进行灌根接种,观察种子萌发、幼苗存活和幼苗感病情况。 结果 各群落土壤中种子发芽均呈先上升后下降规律,且基本在第8~10天达到高峰;林地土与非林地土种子发芽率差异不显著,但林地根区土幼苗的存活率极显著低于非林地土和林地非根区土;距母树3个不同距离根区土的幼苗存活率差异不显著。灌根接种不同处理间幼苗存活率差异极显著,具体表现为接种RS2、RS5根区真菌的幼苗感病率显著高于根系分泌物及无菌水空白对照,且RS2真菌的根系分泌物悬浮液幼苗感病率显著高于其无菌水悬浮液。 结论 毛红椿种子萌发不受土壤环境的影响,但幼苗建成受根区范围内土壤的影响,根系分泌物和致病菌的互作显著降低幼苗保存率。由此推断,毛红椿根区土壤内存在幼苗的潜在致病菌及根系分泌物可增强其致病性。 Abstract:Objective The barrier factors influencing the natural regeneration of Toona ciliata var. pubescens were explored through investigating the effects of forest soil and fungi in different natural communities on seed germination and seedling survival. Method Soil samples were collected from the root zone at three distances (2.5, 5.0, and 7.5 m) from the mother trees as well as the natural forest stands 25 m away from the mother trees in Jiulianshan National Nature Reserve. The seed germination trial on soils was carried out in the laboratory with non-forest soil as the control. In addition, the seedling infection trial in soil was also performed in the laboratory with root irrigation by fungi isolated from root zone soil and suspended with water or root exudates. The seed germination, seedling survival and seedling susceptibility were observed. Result The germination of seed in all kinds of soil revealed the tendency of increasing at initial and then decreasing, and reached the peak during the eighth to tenth day after sowing. There were no significant differences between forest soil and non-forest soil in germination rate, while the seedling survival rate of forest soil was significantly lower than that of non-forest soil. There were significant differences between root zone soil and non-root zone soil in seedling survival rate, and the seedling mortality of root zone soil was higher. It was also found that there were no significant differences in seedlings survival rate of root zone soil among different distances from the mother trees. It addition, there were extremely significant differences in seedling infection treatments, and the seedling disease incidence rates of RS2, RS5 soil-borne fungi were significantly higher than those of the two blank controls, water (W) and root exudates (R). Moreover, the disease infection rate of RS2 root exudates suspension was significantly higher than that of RS2 water suspension. Conclusion Forest soil of different natural communities has no effect on seed germination of T. ciliata var. pubescens, However, the seedling establishment is disturbed by root zone soil of the same species; the interaction between root exudates and pathogens can significantly reduce the seedling survival rate. It could be inferred that there are potential pathogens in root zone soil of T. ciliata var. pubescens and root exudates can enhance their pathogenicity. -
Key words:
- Toona ciliata var. pubescens
- / seed germination
- / seedling survival
- / soil-borne fungi
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表 1 九连山毛红椿天然林群落及母树基本情况
Table 1. Geographic location and the mother trees of nature populations T.ciliata var.pubescens stands in Jiulianshan
群落
Stand地形
Geomorphic types经度(E)
Longitude纬度(N)
Latitude海拔
Altitude/m毛红椿相对密度
Relative density of Toona ciliate var. pubescens/%母树平均高度
Mean height of the mother tree/m母树平均胸径
DHB of the mother tree/cm大丘田Daqiutian 山谷Valley 114°26′ 24°34′ 501 37.93 23.5 40.0 电站Dianzhan 山坡Hillside 114°30′ 24°36′ 575 49.22 21.0 29.8 虾公塘Xiagongtang 山谷Valley 114°27′ 24°31′ 760 22.22 22.5 31.9 表 2 距毛红椿母树不同距离的种子发芽率与幼苗保存率
Table 2. Seedling survival rate and seed germination rate of T.ciliata var. pubescens in different distances from the mother tree
离母树距离
Distances from the mother tree发芽率seed germination rate/% 保存率seedling survival rate/% 大丘田
Daqiutian虾公塘
Xiagongtang电站
Dianzhan总均值
Total mean大丘田
Daqiutian虾公塘
Xiagongtang电站
Dianzhan总均值
Total mean2.5 m根区2.5 m root zone 77.00±6.25a 63.33±14.98a 77.67±7.09a 72.67±11.29a 15.70±18.24c 38.84±4.85 b 27.82±14.35b 27.45±15.52B 5.0 m根区5.0 m root zone 66.33±5.13a 73.67±6.35 a 73.67±7.64a 71.22±6.47a 40.89±3.91b 25.77±16.19b 34.54±22.59ab 33.73±15.50B 7.5 m根区7.5 m root zone 62.33±4.93a 70.33±9.87a 77.67±6.51a 70.11±9.23a 35.00±5.32bc 32.52±20.08b 40.92±10.99ab 36.14±12.33B 非根区Non-root zone 71.00±9.85a 77.33±1.51a 72.00±2.65a 73.44±5.94a 64.03±9.42a 63.80±0.61a 67.14±3.88a 64.99±5.35A 注:同列不同小写字母间表示差异显著(P<0.05),同列不同大写字母间表示差异极显著(P<0.01),下同。
Note:Different lowercase letter along the column indicate significant difference at P<0.05,Different capital letter along the column indicate extremely significant difference at P<0.01,the same as below.表 3 不同类型土壤毛红椿种子发芽率与幼苗保存率
Table 3. Seedling survival rate and seed germination rate of T.ciliata var. pubescens in different soils
土壤类型Soil type 发芽率Seed germination rate/% 保存率Seedling survival rate/% 均值Mean 总均值Total mean 均值Mean 总均值Total mean 林地土Forest soil 根区土Root zone soil 71.33±8.96a 71.86±8.78a 32.44±14.45B 40.58±19.13B 非根区土Non-root zone soil 73.44±5.94a 64.99±5.35A 非林地土Non-forest soil 河沙River sand 62.00±7.58b 72.67±9.29a 74.74±11.04A 70.02±5.43A 沙壤土Sandy soil 77.00±7.58a 64.09±22.31A 菜地土Vegetable soil 79.00±10.25a 71.24±5.44A 表 4 九连山林地土壤的理化性质和酶活性
Table 4. Enzyme activity and physical-chemical properties of Jiulianshan forest soil
土壤性状
Soil traits根区Root zone 非根区Non-root zone 大丘田Daqiutian 虾公塘Xiagongtang 电站Dianzhan 大丘田Daqiutian 虾公塘Xiagongtang 电站Dianzhan 含水率Water content/% 32.57±1.42 34.97±3.82 26.34±3.84 37.67±8.72 39.24±3.65 28.60±3.00 pH值pH value 5.39±0.29 5.40±0.22 6.09±0.14 5.11±0.29 4.90±1.83 5.68±0.36 有机质SOM/(g·kg-1) 15.16±5.44 10.56±0.48 7.40±2.34 17.00±4.37 11.36±0.51 9.36±0.54 蔗糖酶Invertase/(mg·g-1) 4.34±3.24 3.17±0.99 5.61±3.81 6.40±2.37 5.33±3.66 3.72±2.98 纤维素酶Cellulose/(mg·g-1) 1.38±0.86 1.92±0.57 1.41±0.85 7.86±0.79 2.38±0.19 0.95±0.26 铵态氮(NH4+)N/(mg·kg-1) 13.60±5.86 32.55±2.82 21.01±10.33 21.13±11.03 33.13±1.96 16.71±7.43 硝态氮(NO3-)N/(mg·kg-1) 1.61±0.61 1.63±0.28 1.34±0.39 1.86±0.65 1.71±0.40 1.13±0.42 表 5 九连山林地土壤理化性质、酶活性与种子发芽率和幼苗保存率相关分析
Table 5. Correlation of seed germination rate, seedling survival rate and soil physical-chemical properties, enzyme activity of Jiulianshan forest soil
项目Items 相关分析
Correlation含水率
Water contentpH值
pH value有机质
SOM蔗糖酶
Invertase纤维素酶
Cellulose铵态氮
(NH4+)N硝态氮
(NO3-)N发芽率
Seed germination rate皮尔森相关系数Pearson Correlation 0.127 0.033 -0.063 0.210 -0.022 0.054 -0.038 显著性Sig. 0.462 0.848 0.716 0.218 0.900 0.758 0.830 样本数N 36 36 36 36 36 35 35 保存率
Seedling survival rate皮尔森相关系数Pearson Correlation 0.038 -0.107 -0.104 0.114 0.031 0.037 -0.070 显著性Sig. 0.824 0.536 0.546 0.509 0.858 0.832 0.687 样本数N 36 36 36 36 36 35 35 -
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