张昊 邢鸿林 唐国儒 袁天贺 杨玲
摘 要:为解决云杉(Picea)属树种早期生长缓慢影响大径材用材林的培育周期,可通过合理施肥和抚育措施结合处理,促进树高生长和地径增加。以落叶松林下红皮云杉(Picea koraiensis)10 年生人工幼龄林木为研究对象,随机设置12块10 m×10 m 的固定样地,肥料类型选择氮(N-尿素)、氮磷(NP-尿素+过磷酸钙)、氮磷钾(NPK-尿素+过磷酸钙+磷酸钾)。设置2种施肥时间,1)生长季前中后期施肥。每年在生长季初(5月中旬)、中(7月中旬)、后期(8月中旬)施肥3次,连续重复施肥4 a;2)生长季前中末期施肥。每年在生长季初(5月中旬)、中(7月中旬)、末期(9月中旬)施肥3次,连续重复施肥4 a。透光抚育设置,施肥一个生长季后对上层落叶松林木进行生长伐, 抚育后林分郁闭度为0.6。通过研究施肥和透光抚育对林木生长的影响, 旨在开发促进红皮云杉幼树生长的施肥管理技术, 以缩短幼龄林生长周期。施NPK肥促进红皮云杉幼树树高和地径生长的效果好于只施单一肥料或氮磷2种肥料的混合肥。生长季前中末期施加NPK肥处理的树高、地径年生长量比生长季前中后期施加NPK肥的处理分别高41.11%和49.81%。透光抚育后不同年份之间林木的树高年生长量差异不显著,地径年生长量差异显著,3个生长季后树高和地径的年生长量与抚育前相比差异不显著。生长季前中后期施肥结合透光抚育处理2个生长季后树高和地径的年生长量与对照差异显著,3个生长季后只有地径的年生长量与对照差异显著。生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育处理3个生长季后,地径年生长量分别高出对照和生长季前中后期施氮磷钾肥(NPK1)结合透光抚育的处理153.16%和10.31%。施肥与透光抚育结合处理可以提高红皮云杉地径的年生长量,在连续施肥4 a时达到显著水平,生长季前中末期施肥效果好于前中后期施肥。研究结果为解决林下造林红皮云杉人工林木幼龄期生长缓慢、缩短红皮云杉大径材用材林培育周期奠定了基础。
关键词:红皮云杉;施肥;透光撫育;幼龄人工林;林木生长
中图分类号:S722.8 文献标识码:A 文章编号:1006-8023(2023)03-0021-09
Abstract:The period of cultivation of large-diameter timber stands is affected by the relatively slow initial growth of Picea species. The combination of fertilization and nurturing measures can promote the growth of tree height and ground diameter. In this paper, 12 fixed plots of 10 m×10 m were randomly set up in a larch understory with 10 a juvenile Picea koraiensis plantations as the study subjects. Fertilizer types were selected as N (N - urea), NP (NP - urea+superphosphate), NPK (NPK - urea+superphosphate+potassium phosphate). Two types of fertilization time were set: (1) pre-middle-late growing seasons fertilization: fertilizer was applied per year at the beginning (mid-May), middle (mid-July), and late (mid-August) of the growing season, with fertilization repeated for four consecutive years. (2) Pre-middle-end growing seasons fertilization: fertilizer was applied per year at the beginning (mid-May), middle (mid-July) and end (mid-September) of the growing season, with fertilization repeated for four consecutive years. Light-felling was set as follows, after one growing season of fertilization, accretion cutting the upper larch trees, and the stand density was 0.6 after tending. By studying the effects of fertilization and light-felling on the growth of trees, the aim was to develop fertilization management techniques to promote the growth of juvenile P. koraiensis, so as to shorten the growth cycle of young plantation. The effect of applying NPK fertilizer on promoting the height and diameter growth of juvenile P. koraiensis was better than applying only a single fertilizer or a mixture of nitrogen and phosphorus fertilizers. The annual tree height and ground diameter growth were 41.11 % and 49.81 % higher in the treatments NPK fertilizer applied pre-mid-end growing seasons than those treated with NPK in the pre-mid-late growing seasons. After light-felling, the annual growth of tree height between different years was not significantly different, but that of the ground diameter was significantly different. The annual growth of tree height and ground diameter after three growing seasons were not significantly different from that before light-felling. By combining fertilizer application in the pre-middle-late growing seasons with light-felling treatments, the annual growth of tree height and ground diameter were significantly different from the control group after two growing seasons, only the annual growth of ground diameter was significantly different from the control group after three growing seasons. After three growing seasons of nitrogen, phosphorus and potassium fertilizers (NPK2) combined with light-felling in the pre-mid-end of growing seasons, the annual growth of ground diameter was 153.16 % and 10.31 % higher than that of the control and pre-middle-late of growing seasons NPK fertilizers (NPK1) combined with light-felling. The combination of fertilization and light-felling treatments can increase the annual growth of P. koraiensis ground diameters, reaching a significant level at four consecutive years of fertilization. Fertilizer application at the pre-mid-end stages of the growing season is more effective than at pre-mid-late stages. The research provides a basis for solving the problem of slow growth of P. koraiensis plantation at a young age and shortening the cultivation period of large-diameter timber plantation of P. koraiensis.
Keywords:Picea koraiensis; fertilization; light-felling; young plantation; tree growth
基金项目:国家重点研发项目(2017YFD0600600)
第一作者简介:张昊,硕士研究生。研究方向为人工林定向培育。E-mail: zhanghao010015@163.com
*通信作者:杨玲,博士,教授,博士生导师。研究方向为人工林定向培育。E-mail: yangl-cf@nefu.edu.cn
0 引言
云杉(Picea)属广布北半球欧、亚和北美大陆,构成高纬度和低纬度高海拔植被区的主要顶级群落建群种,在我国属第4大树种之一,是我国林业产业的基础。红皮云杉是松科(Pinaceae)云杉属常绿乔木,可作为园林观赏植物。红皮云杉具有成活率高,成林、成材把握大,抗病虫害力强,适应力强的特点,在立地条件差的地方也能成林;但是由于其初期生长缓慢(10 a后生长迅速)[1]及生长期较长的缺点,限制了大径材林木的供应。幼树生长速度缓慢,需要人为改善環境以促进红皮云杉幼树生长。促进幼树生长的抚育措施技术主要有间伐、施肥和除草等。施肥与透光抚育措施结合处理可减少郁闭度、增加光照强度、促进幼树生长[2-4]。人为补充土壤中的养分,为植物生长提供充足的养分,可促进植物快速生长缩短成材时间,提高树木的成材率[5]。目前林木施肥研究多集中以氮、磷、钾配比施肥试验[6],不同氮磷钾肥料的配比,对树木生长、生理以及养分积累程度的影响差异较大[7-8]。除研究配比肥料之外,为了减少实际生产的成本,利用市场已有的不同类型复合肥,满足树木在生长时期的养分需求[9]。
国内外研究者针对人工林施肥已经取得了很多宝贵经验[10]。Bergh等[11]对瑞典北部挪威云杉(Picea abies)重复施肥发现,施肥后的挪威云杉生长速度明显地上升,达到对照组的3倍。现阶段对于红皮云杉的研究发现,施肥处理影响了红皮云杉菌根真菌和AM真菌生态系统的多样性。不同肥种及不同施肥量对红皮云杉幼苗生长有差异显著[12],此外,有关根系形态对不同氮形式的适应情况和对不同类型氮肥的需求规律也有研究[13]。光环境对幼树的横向、纵向发育的影响明显[14]。目前对施肥和透光抚育等措施结合处理的研究尚少,且对红皮云杉对不同施肥处理组合连续多年重复施肥的响应情况了解不足。
本研究以红皮云杉10 年生幼树为研究对象,在黑龙江省佳木斯市孟家岗林场做了施肥与透光试验,通过调查红皮云杉的生长指标,分析不同施肥措施(肥料配比、施肥时间)、透光抚育以及二者结合的经营效果,归纳总结施肥结合透光抚育对红皮云杉幼树生长的影响,研究建立合理的施肥透光抚育机制,对红皮云杉幼树加速生长有重要意义。
1 试验地概况与试验方法
1.1 试验地概况
试验地点位于黑龙江省佳木斯市孟家岗林场,地理位置为130°32″42′~130°52″36′ E, 46°20″16′~46°30″50′ N,海拔170~575 m,属于东亚大陆性季风气候。全年最高气温为35.6℃,最低气温为-38.6 ℃,年均气温为2.7 ℃,年均降水量为550 mm,无霜期为120 d左右,全年日照时间为1 955 h。土壤主要以暗棕壤为主,还有少量白浆土、草甸土、泥炭土和沼泽土。试验地土壤养分基本情况见表1。
1.2 样地设置和施肥方法
以40 年生落叶松林下定植的10 a红皮云杉人工林为研究对象,施肥前试验幼树平均树高为0.92 m,平均地径为2.36 cm,郁闭度为0.9。将全部试验样地设置为12块10 m×10 m 的固定样地。每种施肥类型设置3组重复,分别施用氮肥(N)、氮磷肥(NP)、氮磷钾复合肥(NPK)。设置2种施肥时间,1)生长季前中后期施肥:每年在生长季初(5月中旬)、中(7月中旬)、后期(8月中旬)施肥3次,连续重复施肥4 a;2)生长季前中末期施肥:于生长季前期(5月中旬)和中期(7月中旬)、生长季末期(9月中旬)施NPK肥3次,连续重复施肥4 a。施肥前先将试验幼树半径50 cm以内的穴面杂草清除。施肥方法为所施的肥料沿幼树两侧10 cm 处、深7~10 cm沟内一次性施入。其中,施氮量为每株100 g,施磷量为每株50 g,施钾量为每株100 g。根据季节温度变化调节施肥量,5月份施30%、7 月份施40%、8 月份施30%。具体单株和各月份施肥量见表2。按照黑龙江省地方标准《森林采伐更新技术规程》(DB/2300B 64001—88)的规定操作,2018年生长季结束后对样地内40 a落叶松进行30%株数强度的采伐。
1.3 透光抚育处理和生长量调查
2018年冬季对上层落叶松林木进行生长伐,采伐按照黑龙江省地方标准《森林采伐更新技术规程》(DB/2300B 64001—88)的规定操作,抚育后林分郁闭度为0.6。每年生长季结束后对样地内红皮云杉幼树进行生长指标测量,连续调查3个生长季。每样地红皮云杉幼树数量为40~75株。使用卷尺对苗高与冠幅进行测量,精确到0.1 cm,使用游标卡尺对地径进行测量,精确到0.1 mm。
1.4 数据处理与分析
用Microsoft Excel 2019进行数据处理,使用IBM SPSS Statistics 19 统计分析软件在显著水平为5%条件下进行单因素方差分析比较。数据结果均用“平均值±标准误”表示。
2 结果与分析
2.1 透光抚育前施肥对红皮云杉幼龄林林木生长的影响
透光抚育前的生长季前中后期不同施肥处理的树高年生长量差异显著(P<0.05),地径年生长量差异不显著(P>0.05)。各处理中,生长季前中后期施氮磷钾复合肥的处理(NPK1)的地径年生长量均高于其他处理组,比对照组高5.78%,见表3。
透光抚育前,生长季前中末期施肥处理的红皮云杉树高年生长量均差异显著(P<0.05),地径年生长量的差异不显著(P>0.05)。施加NPK肥后,树高和地径年生长量分别高于对照组17.05%和58.47%,生长季前中末期施加NPK肥处理的树高、地径年生长量比生长季前中后期施加NPK肥的处理分别高41.11%和49.81%,见表4。
2.2 透光抚育对红皮云杉幼龄林林木生长的影响
透光抚育后连续调查3 a未施肥处理的样地,发现不同年份之间红皮云杉幼龄林的树高年生长量差异不显著(P>0.05),地径的年生长量差异显著(P<0.05)。透光抚育3个生长季后(2021年),树高和地径的年生长量与抚育前相比差异不显著(P>0.05),见表5。
2.3 施肥与透光抚育结合处理对红皮云杉幼龄林林木生长的影响
2.3.1 生长季前中后期施肥与透光抚育结合处理的影响
生长季前中后期施肥与透光抚育结合处理的影响,如图1所示。施肥处理结合透光抚育后的第1个生长季的树高和地径的年生长量与对照无显著差异。不同施肥处理树高和东西冠幅的年生长量均低于对照,但差异不显著(P>0.05)。地径年生长量由大到小依次为:NP、NPK1、N、CK(P>0.05),而南北冠幅由大到小依次为:NPK1、CK、NP、N(P>0.05)。施肥处理结合透光抚育后的第2个生长季的树高和地径的年生长量与对照差异显著。不同施肥处理树高年生长量均低于对照(P<0.05);施加NP、NPK肥结合透光抚育的地径年生长量显著大于对照组,分别为170.7%和156.6%(P<0.05)。南北冠幅生长量由大到小依次为:N、CK、NP、 NPK1(P<0.05),而东西冠幅由大到小依次为:N、CK、NPK1、NP(P<0.05)。施肥处理结合透光抚育后的第3个生长季的树高的年生长量与对照差异不显著(P>0.05),地径的年生长量与对照差异显著(P<0.05)。施加NPK1肥结合透光抚育的地径年生长量显著大于對照组和其他施肥处理(P<0.05)。南北冠幅生长量差异不显著(P>0.05),而东西冠幅由大到小依次为:CK、N、NP、NPK1(P<0.05)。
2.3.2 生长季前中末期施肥与透光抚育结合处理的影响
生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育后的第1个生长季的树高和地径的年生长量与对照相比差异显著。生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育处理的树高、地径和南北冠幅的年生长量均显著高于对照和生长季前中后期施氮磷钾肥处理(NPK1)(P<0.05)。东西冠幅的年生长量与对照和生长季前中后期施氮磷钾肥处理(NPK1)相比差异均不显著(P>0.05)。生长季前中末期施加NPK肥处理的树高、地径年生长量比生长季前中后期施加NPK肥的处理分别高36.00%和13.98%。
生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育后的2个生长季的树高、地径、南北和东西冠幅的年生长量与对照及生长季前中后期施氮磷钾肥处理(NPK1)结合透光抚育的处理相比均差异不显著。生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育处理的地径、东西冠幅年生长量高于对照组22.3%和10.31%,树高、南北冠幅年生长量低于对照组39.68%和3.80%。生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育处理的树高、地径的年生长量比生长季前中后期施氮磷钾肥处理(NPK1)结合透光抚育的处理相比分别低5%和52.2%,南北、东西冠幅年生长量分别提高了80.95%和15.05%。
生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育后的3个生长季的树高年生长量与对照相比差异不显著,地径年生长量与对照相比差异显著。生长季前中末期施氮磷钾肥处理(NPK2)结合透光抚育处理的地径年生长量分别高出对照和生长季前中后期施氮磷钾肥(NPK1)结合透光抚育的处理153.16%和10.31%(P<0.05),如图2所示。
3 讨论与结论
3.1 讨论
施肥是1项人工林管理措施,旨在提高土壤生产力,从而增加树木的横向生长。在北方森林环境条件下,氮(N)是最重要的生长限制因子[15]。在透光抚育前的生长季前中后期连续施3次不同组合肥料对林木的影响有所不同。NPK1施肥效果均高于其他施肥处理组,其中对地径的生长量影响最大,比对照组高5.78%。大量的施肥试验表明,在生长季进行不同的施肥处理均可对幼树的生长产生正向影响,其中所有处理中对幼树横向数据影响明显,树木横向数据是表达树木生长状况的重要参考。Loewe-Munoz等[16]对意大利石松(Pinus pinea)施肥研究结果表明施肥对直径生长有重要影响。施肥促进树冠和茎的快速生长。主要原因是施肥促进了植物的生长,进而导致根部和茎部碳水化合物含量的下降[17]。施肥增加径部生长与碳储备呈负相关,施肥处理提高了根系向上运输碳水化合物的有效性,从而提高了林木冠幅的伸长[18]。Haynes等[19]发现施肥可以提高林木生长最快时期(夏季)的胸径生长量,施肥处理的夏季每日胸径生长量可达0.06 mm,是对照处理的3倍。同时施肥可以增加光合能力(通过增加叶面积指数或提高叶片的光合效率),或减少碳分配到细根生长,从而释放碳以促进茎生长。在肥沃的地方长期对苏格兰松 (Pinus sylvestris)施氮肥,枝条生物量增加了25%[20]。谈锋等[21]的研究进一步表明,氮磷钾复合肥比单一肥料更有效提高柳树(Salix babylonica)的苗高和地径,促进横向生长主要原因为氮肥是林木体内蛋白质重要组成元素,促进生长,充足的磷肥可以促进植物发育,促进生殖器官发育。而钾肥则是影响林木根系发育,使得植物茎发育粗壮。
透光抚育前的生长季前中末期施肥同样可以对红皮云杉幼树的生长起到促进作用。在缺乏常规施肥的情况下,当幼树的生物量继续积累时,氮储量通常在秋季被稀释,从而产生秋季施氮的必要性[22]。秋季施肥(生长季末期施肥)是一项重要的栽培和管理措施,用于在生长季节结束时的硬化阶段提供养分、增强养分储备并在第2个春季促进额外的生长[23]。Rikala等[24]在挪威云杉(Picea abies)常规施肥和秋季施肥结果比较中发现,秋季施肥处理后的幼苗树高、地径等生长指标远高于常规施肥,而且新长出的叶片和枝条的数量是常规施肥的2倍。主要原因是秋季施肥可以提供大量养肥为幼树下一年的生长贮存养分[25],休眠结束后能够较快地生长发育。秋季施肥能缓解苗木生长后期的养分稀释效应,保持一定的养分含量,在苗木中储存充足的养分,比春季施肥、夏季施肥更能促进生物量和养分积累[26]。只透光抚育处理不施肥对红皮云杉幼龄林木的生长影响不显著。透光抚育和施肥可以共同促进林分发育,但径向生长会随着抚育强度的增加而增加,而高强度抚育措施才对纵向生长有促进作用[27]。马尾松(Pinus massoniana)林随着间伐时间的增加,林下植被总生物量随间伐强度的增幅也会在一定程度内相应增大[28]。间伐后直径增加的类似结果在许多研究中呈现[29]。合理的间伐强度能够促进林分生长及其林下植被发育。间伐可以增加树冠的开放度(光照可用性),改变土壤温度和水分条件,影响植物养分的吸收,最终影响林下幼树的生长发育[30-32]。在本研究中,透光抚育后造成红皮云杉年生长量减少的原因可能是采伐强度不够。
本研究发现,透光抚育结合生长季前中后期、生长季前中末期施氮磷钾肥处理3个生长季的地径年生长量均显著高于对照。Brockley[33]对黑松(Pinus thunbergii)幼龄林抚育结合施肥的研究表明,间伐强度不足会对下层幼龄林造成光照的不足从而使得光合作用等反应减弱,生长速率也会随之降低。根据分析得到30%透光抚育措施产生的林窗,对红皮云杉幼树的树高生长率没有显著促进作用。上层树木被间伐后,树木在施肥的帮助下立即有一个扩展的树冠空间,从而导致更高的单树树冠生長,整体增加体积增长。间伐后林分光照增加,树枝只要接收到光就可以存活,从而使幼树的光合作用可以继续进行。施肥后到冠高无明显差异,这表明限制高度的是光照而不是养分。
3.2 结论
施肥可以促进红皮云杉幼树生长。施氮磷钾复合肥促进红皮云杉幼树树高和地径生长的效果好于只施单一肥料或氮磷两种肥料的混合肥。透光抚育3个生长季后树高和地径的年生长量与抚育前相比差异不显著。生长季前中后期施肥结合透光抚育处理2个生长季后树高和地径的年生长量显著增加,3个生长季后只有地径的年生长量显著增加。生长季前中末期施氮磷钾肥结合透光抚育处理3个生长季后,地径年生长量分别高出对照和生长季前中后期施氮磷钾肥结合透光抚育的处理153.16%和10.31%。因此认为,施肥与透光抚育结合处理可以提高红皮云杉地径的年生长量,且在连续施肥4 a时达到显著水平;生长季前中末期施肥对红皮云杉幼龄林木生长的促进效果好于前中后期施肥。
红皮云杉幼龄林木施肥可以解决林下造林红皮云杉人工林木幼龄期生长缓慢的问题,可为缩短红皮云杉大径材用材林培育周期奠定了基础。
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