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苗木品质是影响造林效果的首要因子,选择品质高的苗木不仅能够提高造林成活率,而且能达到良好的造林效果[1]。施肥是改善苗木品质,提高苗木自身竞争力的重要手段。氮素是植物生长所必需的矿质营养元素之一,它可以调控植物的生长发育,影响植物的光合作用,是组成各种重要有机化合物不可或缺的部分,氮素需求一直是研究热点。目前,常采用的施肥方法主要有常规施肥(CF)和指数施肥(EF)。常规施肥是指在生长期内重复施用同样剂量的肥料。指数施肥则是根据植物在各生长阶段对养分的需求规律,采用指数递增的养分添加方式的一种施肥方法[2-3]。该方法可诱导植株稳态奢侈养分消耗,有效提高苗木体内养分载荷,增强苗木的竞争能力,从而使苗木更好地适应造林地的立地条件[4-5],相对于常规施肥,指数施肥培育的苗木成活率更高,生长效果更好[6],也能避免因肥料过量施用造成的土壤污染。目前,国外用于指数施肥研究的树种有黑云杉Picea mariana[7],日本落叶松Larix kaempferi[8],西铁杉Tsuga heterophylla[9]和花旗松Pseudotsuga menziesii[10]等,且研究成果已经达到应用水平,指数施肥已逐渐成为国外苗木培育的主要施肥方式。近年来,国内利用稳态养分理论对栓皮栎Quercus variabilis[11],山桃稠李Padus maackii[12],楸树Catalpa bungei[13],檀香Santalum album[14]和红楠Machilus thunbergii[15]等树种开展了指数施肥的研究。杉木Cunninghamia lanceolata是中国南方16省区最重要的造林树种之一,是中国特有的速生商品树种,生长快,材质好。与实生苗相比,采用杉木优良无性系造林,林相整齐,林分生长一致,便于集约经营,其产量可增加58.7%[16],且无性系的木材材性均匀一致,收获期一致,是营造工业用材林的最佳材料[17]。因此,无性系造林已逐渐成为杉木造林的主要方法,而无性系优质苗木是成功营造杉木人工林的基础。指数施肥可有效促进杉木实生苗的生长,改善苗木的营养状态[18],推测指数施肥对杉木无性系苗木可能有相似的效果,但目前指数施肥对杉木无性系苗育苗的效果尚不清楚。本研究以1年生杉木无性系苗为研究对象,设置不同的氮素施入方式和用量,在盆栽条件下研究在一个生长季内杉木无性系苗的生长和氮养分的积累对不同施肥处理的响应,旨在揭示杉木无性系幼苗对氮素的需求规律,确定适宜的施氮量,为杉木无性系育苗的营养管理提供参考。
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施肥促进了杉木苗高和地径的生长(图 2)。与对照相比,4个施肥处理的杉木苗高增长34.1%~60.5%,地径增粗20.5%~40.4%,差异均达显著水平(P<0.05)。与常规施肥(CF)相比,指数施肥处理苗高增长了4.1%~19.8%,地径增粗了4.6%~19.8%,苗高和地径均以EF2处理为最佳,显著高于常规施肥(CF)(P<0.05)。
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如表 1所示:不同处理根生物量为10.14~14.13 mg·株-1,差异并不显著(P>0.05)。4个施肥处理的茎、叶和全株生物量与对照相比,增加了113.9%~166.9%,158.0%~230.9%,96.4%~128.9%,差异达显著水平(P<0.05);其中指数施肥EF2处理的茎、叶和全株生物量最高,与常规施肥(CF)相比,分别增加12.2%,27.1%,13.9%。
表 1 不同施肥处理杉木不同器官生物量
Table 1. Biomass of Chinese fir under different fertilization treatments
施肥处理 根/(g·株-1) 茎/(g·株-1) 叶/(g·株-1>) 全株/(g·株-1) 对照 10.14 ± 2.84 a 5.33 ± 1.58 b 7.68 ± 2.11 b 23.15 ± 6.40 b 常规施肥CF 13.84 ± 3.33 a 12.68 ± 1.92 a 19.99 ± 4.79 a 46.51 ± 9.35 a 指数施肥EF1 14.13 " 2.24 a 12.16 ± 0.47 a 19.81 ± 1.86 a 46.10 ± 4.08 a 指数施肥EF2 13.35 ± 2.29 a 14.23 ± 3.61 a 25.41 ± 2.99 a 52.99 ± 8.85 a 指数施肥EF3 12.74 ± 1.38 a 11.40 ± 3.16 a 21.32 ± 2.82 a 45.45 ± 6.97 a -
如表 2所示:不同施肥处理杉木幼苗叶的氮质量分数大小为EF3(23.36 g·kg-1)>EF2(17.45 g·kg-1)>EF1(17.22 g·kg-1)>CF(14.00 g·kg-1)>对照(9.92 g·kg-1)。常规施肥(CF)处理比对照高41.1%;指数施肥EF处理比对照高73.6%~135.5%,显著高于CF处理,其中EF3处理又显著高于EF2和EF1处理(P<0.05)。根中氮质量分数大小为EF2(13.95 g·kg-1)>EF3(13.86 g·kg-1)>CF(10.73 g·kg-1)>EF1(9.43 g·kg-1)>对照(7.69 g·kg-1)。与对照相比,常规施肥CF处理氮质量分数增加了39.6%,指数施肥EF处理增加了22.6%~81.4%,EF2和EF3处理显著高于CF和EF1处理(P<0.05)。茎中氮质量分数大小为EF3(13.77 g·kg-1)>EF2(10.14 g·kg-1)>EF1(6.94 g·kg-1)>CF(6.36 g·kg-1)>对照(5.45 g·kg-1)。与对照相比,常规施肥CF处理茎的氮质量分数减少了16.6%,差异不显著(P>0.05),指数施肥EF处理增加了27.3%~152.6%,达到显著性水平(P<0.05)。指数施肥EF处理显著高于常规施肥CF处理(P<0.05),增加了9.1%~116.5%。
表 2 不同施肥处理杉木幼苗不同器官氮质量分数和氮积累量
Table 2. Nitrogen concentration and accumulation of Chinese fir under different fertilization treatments
施肥处理 氮质量分数/(g·kg-1) 氮积累量/(mg·株-1) 根 茎 叶 根 茎 叶 对照 7.69 ± 0.26 c 6.44 ± 0.35 c 9.92 ± 0.51 d 77.98 ± 2.67 c 34.33 ± 1.88 c 76.22 ± 3.93 e 常规施肥CF 10.73 ± 0.27 b 5.94 ± 0.77 c 14.00 ± 0.27 c 148.57 ± 3.73 b 75.34 ± 9.72 b 279.84 ± 5.39 d 指数施肥EF1 9.43 ± 0.54 b 6.94 ± 0.35 bc 17.22±0.13 b 133.17 ± 7.73 b 84.33 ± 4.21 b 341.19 ± 2.67 c 指数施肥EF2 13.95 ± 0.62 a 10.14 ± 0.86 b 17.45 ± 0.48 b 186.19 ± 8.27 a 144.31 ± 12.23 a 443.49 ± 12.32 b 指数施肥EF3 13.86 ± 0.35 a 13.77 ± 0.14 a 21.31 ± 0.35 a 176.53 ± 4.46 a 156.49 ± 1.54 a 504.35 ± 7.47 a -
不同施肥处理下,杉木无性系幼苗叶的氮积累量大小为EF3(504.4 mg·株-1)>EF2(443.5 mg·株-1)>EF1(341.2 mg·株-1)>CF(279.8 mg·株-1)>对照(76.2 mg·株-1),5个处理之间差异均达到显著性水平(P<0.05)。与对照相比,施肥处理显著增加267.2%~561.7%(P<0.05);其中,指数施肥EF处理比常规施肥CF处理显著高出10.9%~66.2%(P<0.05)。根的氮积累量大小为EF2(186.2 mg·株-1)>EF3(176.5 mg·株-1)>CF(148.6 mg·株-1)>EF1(133.17 mg·株-1)>对照(80.0 mg·株-1)。与对照相比,施肥处理的根氮积累量显著增加了70.8%~138.8%(P<0.05),其中,指数施肥EF2和EF3处理显著高于常规施肥CF处理(P<0.05),分别高出25.3%,18.8%。茎的氮积累量大小为EF3(156.5 mg·株-1)>EF2(144.3 mg·株-1)>EF1(84.3 mg·株-1)>CF(75.3 mg·株-1)>对照(34.33 mg·株-1)。与对照相比,施肥处理增加了119.5%~355.8%,差异达显著性水平(P<0.05)。其中指数施肥EF处理与常规施肥CF处理相比,增加了11.9%~107.7%,EF2和EF3处理显著高于CF处理(P<0.05)。
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由图 3可知:不同施肥处理下,杉木无性系幼苗各器官的氮素分配率大小顺序总体表现为:叶>根>茎,其中叶氮积累量所占比例大小为EF3(60.2%)>EF1(61.1%)>EF2(57.3%)>CF(55.5%)>对照(40.4%),根中氮所占比例大小为对照(41.4%)>CF(29.5%)>EF2(24.1%)>EF1(23.8%)>EF3(21.1%),茎中氮积累量所占比例大小为EF3(18.7%)>EF2(18.6%)>对照(18.2%)>EF1(15.1%)>CF(15.0%),可以看出氮的主要储存器官是叶片,施氮可显著增加杉木叶片中氮积累量所占比例,降低根的氮积累量所占比例,使杉木幼苗的氮积累量由根向叶转移,而施氮对茎的氮积累量无明显差异。
Growth and N accumulation in seedlings of Cunninghamia lanceolata clones with N exponential fertilization
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摘要: 杉木Cunninghamia lanceolata是中国特有的速生商品材树种。培育优质无性系苗木是杉木造林成功的关键。探讨了氮素指数施肥对杉木幼苗生长及养分积累的影响,为杉木苗木培育提供基础。以1年生无性系杉木幼苗为材料,采用温室盆栽方法,设定不施肥(对照)、常规施肥(CF)和指数施肥(EF1,EF2,EF3)共5个处理,纯氮施用总量分别为0,0.5,0.5,1.0,2.0 g·株-1,共施氮20次,间隔为10 d。至生长结束后,分别测定杉木的苗高、地径、生物量及氮素质量分数。结果表明:① 施肥显著促进了杉木无性系的苗高、地径和生物量的生长,以指数施肥EF2处理为最佳,分别为59.0 cm,6.0 mm,52.99 g·株-1;② 杉木无性系苗木不同器官的氮质量分数和氮积累量表现为叶>根>茎。与对照相比,常规施肥的根、茎、叶的氮质量分数增加39.6%,16.6%和41.1%,氮积累量增加90.5%,119.5%和267.2%;指数施肥的根、茎、叶的氮质量分数分别增加22.6%~81.4%,27.3%~152.6%和73.6%~135.5%,氮积累量分别增加70.8%~138.8%,145.7%~355.8%和347.6%~561.7%。除EF1处理外,杉木幼苗根、茎和叶的氮质量分数和氮积累量均表现为指数施肥显著大于常规施肥(P < 0.05)。施氮显著提高了杉木无性系幼苗的生长,其中施氮量为1 g·株-1的指数施肥是杉木幼苗温室培育的适宜方法。Abstract: High quality cloned seedlings of Chinese fir (Cunninghamia lanceolata), a fast-growing China-specific plant species dominant in south China, play an important role in Chinese fir forestation. To understand the effects of N exponential fertilization on seedling growth and nutrient content of Chinese fir, pot experiments were conducted in a greenhouse. One-year-old cloned seedlings were used with five N treatments per seedling including no fertilizer (ck) (0 g), conventional fertilization (CF) (0.5 g), and exponential fertilizations of EF1 (0.5 g), EF2 (1.0 g), and EF3 (2.0 g). Replications N fertilization was conducted 20 times at 10 d intervals. Height, ground diameter, biomass, and N absorption were measured after seedling growth. Analyses included state the sampling method and size. Results showed that fertilization of Chinese fir clones significantly promoted seedling height, ground diameter, and biomass (P < 0.05) with the EF2 treatment being optimal having the highest values of 59.0 cm for height, 6.0 mm for diameter (P < 0.05). N concentration and N content in different organs were leaves > roots > stems. Compared with ck, for conventional fertilization groups the N concentration increased in roots 39.6%, stems 16.6%, and leaves 41.1% with N content increasing 90.5% in roots, 119.5% in stems, and 267.2% in leaves; and for exponential fertilization groups the N concentration increased 22.6%-81.4% in roots, 27.3%-152.6% in stems, and 73.6%-135.5% in leaves with N content increasing 70.8%-138.8% in roots, 145.7%-355.8% in stems, and 347.6%-561.7% in leaves. Thus, N application rate had strong effect on growth of Chinese fir with the best method for cultivating Chinese fir cloned seedlings, considering seedling growth, N concentration, and N accumulation, being exponential N of 1 g·seedling-1.
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表 1 不同施肥处理杉木不同器官生物量
Table 1. Biomass of Chinese fir under different fertilization treatments
施肥处理 根/(g·株-1) 茎/(g·株-1) 叶/(g·株-1>) 全株/(g·株-1) 对照 10.14 ± 2.84 a 5.33 ± 1.58 b 7.68 ± 2.11 b 23.15 ± 6.40 b 常规施肥CF 13.84 ± 3.33 a 12.68 ± 1.92 a 19.99 ± 4.79 a 46.51 ± 9.35 a 指数施肥EF1 14.13 " 2.24 a 12.16 ± 0.47 a 19.81 ± 1.86 a 46.10 ± 4.08 a 指数施肥EF2 13.35 ± 2.29 a 14.23 ± 3.61 a 25.41 ± 2.99 a 52.99 ± 8.85 a 指数施肥EF3 12.74 ± 1.38 a 11.40 ± 3.16 a 21.32 ± 2.82 a 45.45 ± 6.97 a 表 2 不同施肥处理杉木幼苗不同器官氮质量分数和氮积累量
Table 2. Nitrogen concentration and accumulation of Chinese fir under different fertilization treatments
施肥处理 氮质量分数/(g·kg-1) 氮积累量/(mg·株-1) 根 茎 叶 根 茎 叶 对照 7.69 ± 0.26 c 6.44 ± 0.35 c 9.92 ± 0.51 d 77.98 ± 2.67 c 34.33 ± 1.88 c 76.22 ± 3.93 e 常规施肥CF 10.73 ± 0.27 b 5.94 ± 0.77 c 14.00 ± 0.27 c 148.57 ± 3.73 b 75.34 ± 9.72 b 279.84 ± 5.39 d 指数施肥EF1 9.43 ± 0.54 b 6.94 ± 0.35 bc 17.22±0.13 b 133.17 ± 7.73 b 84.33 ± 4.21 b 341.19 ± 2.67 c 指数施肥EF2 13.95 ± 0.62 a 10.14 ± 0.86 b 17.45 ± 0.48 b 186.19 ± 8.27 a 144.31 ± 12.23 a 443.49 ± 12.32 b 指数施肥EF3 13.86 ± 0.35 a 13.77 ± 0.14 a 21.31 ± 0.35 a 176.53 ± 4.46 a 156.49 ± 1.54 a 504.35 ± 7.47 a -
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https://zlxb.zafu.edu.cn/article/doi/10.11833/j.issn.2095-0756.2017.03.011