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林窗式疏伐指通过砍伐特定的冠层林木形成林冠空窗,是一种模拟林窗干扰的近自然林业措施,对森林可持续经营管理具有重要意义。林窗式疏伐降低了余留木的竞争,改变了资源可利用性,进而影响其生长[1-2]。叶作为林木主要的同化器官,其形态和生理特性对林窗式疏伐的响应是决定疏伐后余留木生长响应的关键因素。常绿树种包含从几天到几年不等叶龄的叶片,因此同化过程比落叶树种更为复杂[3-4]。之前的研究多关注于当年生叶光合特性对疏伐的响应,对多年生叶了解较少。然而多年生叶在常绿树种叶总生物量中占有很大的比例[3],对整株林木生长发挥重要作用[5]。因此,了解余留木各个叶龄叶光合特性对林窗式疏伐的响应对全面评估其响应机制和准确预估余留木生长动态具有重要意义。
林窗式疏伐后余留木叶光合特性的改变主要是由其光照、水分和养分条件的改变导致的。光照强度、光照时长和光合有效辐射均随着林窗面积增大而升高[6-8],温度、土壤水分和养分可利用性也与林窗大小紧密相关[9-10]。通常大林窗对余留木生长的促进效应高于小林窗[10]。因此,研究叶光合特性对不同大小林窗疏伐的响应差异可为林业经营管理措施的制定提供理论依据。
叶光合特性对林窗式疏伐的响应主要分为两种方式。一是通过改变叶的形态或者解剖特征更大程度的增加光捕获,提高光合速率。比叶重(LMA)是反映叶光捕获能力的一个重要指标。前人研究表明疏伐通常会增加叶的厚度、密度、叶肉细胞的数量或改变叶肉细胞的排列等[1-2, 11],导致LMA升高。另外一种是通过增加叶氮含量或者改变氮在捕光组分、1, 5-二磷酸核酮糖羧化酶和生物力能学组分中的分配比例[12-13],提高羧化速率和电子传导速率[14]。然而,不同年龄叶形态、化学组成和生理生态特性具有明显差异[15-16]。例如,LMA随着叶龄增大而升高[3-4, 17],但是叶形态可塑性、氮含量和光合氮利用效率随着叶龄增大而逐渐降低[4]。因此,不同叶龄叶形态和生理特性对林窗式疏伐的响应可能存在很大差异。Li等[18]利用双同位素方法发现疏伐导致当年生和1年生叶光合速率的增加,但是对2~4年生叶影响不显著。但是有研究却发现疏伐后最大净光合速率(Amax)的提高主要表现在成熟叶(<2年叶)和老龄叶上(>2年生叶),而对当年生叶影响不明显[1, 19]。
华山松(Pinus armandii Franch.)和油松(Pinus tabuliformis Carr.)是我国青藏高原东缘亚高山地区常见的栽培树种,叶寿命2~4年[20]。各叶龄针叶光合特性对林窗式疏伐的响应,是解释华山松和油松生长响应差异的重要方面。本研究通过对比研究华山松和油松当年生、1年生、2年生叶LMA、叶绿素含量、叶氮含量、Amax、光合氮利用效率(PNUE)对林窗式疏伐的响应差异,探讨林窗大小、叶龄和树种对林窗式疏伐后叶光合特性响应的影响。
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随着叶龄增大,叶LMA逐渐升高,Amax和PNUE逐渐降低(表 1,图 1和图 2)。不同叶龄叶光合特性对林窗疏伐的响应具有明显差异:华山松、油松当年生叶LMA、Chl a、Chl b、Chl a+b、Chl a:b、N、Amax、PNUE在不同林窗疏伐处理间差异均不显著,但是其1年生和2年生叶光合特性对林窗疏伐响应明显(表 1和图 1~4)。
表 1 叶光合特性线性混合模型分析的F值
Table 1. F values based on linear mixed-effect model analyses for leaf photosynthetic characteristics
项目
Items比叶重
LMA叶绿素a
Chl a叶绿素b
Chl b叶绿素a+b
Chl a+b叶绿素a:b
Chl a:b氮含量
N最大净光合速率Amax 光合氮利用效率PNUE 树种Species 28.097** 44.412** 55.007** 46.437** 5.865* 14.948** 5.616* 1.315 叶龄Age 27.315** 3.870* 5.205** 4.574* 14.558** 0.684 33.365** 12.770** 林窗大小Gap size 0.804 5.135* 6.770* 5.748* 4.215* 1.379 4.026* 1.554 树种×叶龄Species×Age 0.518 2.075 2.739 2.047 0.772 1.836 0.342 0.828 树种×林窗大小
Species×Gap size0.474 1.202 0.956 1.112 0.612 0.212 0.165 1.425 年龄×林窗大小
Age×Gap size1.091 3.457* 3.920** 3.951** 0.154 1.954 1.323 1.935 树种×年龄×林窗大小
Species×Age×Gap size1.093 1.394 1.320 1.396 1.248 1.034 0.896 1.531 *P < 0.05, **P < 0.01 图 1 华山松和油松比叶重LMA对林窗式疏伐的响应
Figure 1. LMA responses of Pinus armandii and P. tabuliformis to gap-model thinning
图 2 华山松和油松最大净光合速率Amax和光合氮利用效率PNUE对林窗式疏伐的响应
Figure 2. Leaf Amax and PNUE responses of Pinus armandii and P. tabuliformis to gap-model thinning
图 3 华山松和油松叶绿素含量对林窗式疏伐的响应
Figure 3. Leaf chlorophyll responses of Pinus armandii and P. tabuliformis to gap-model thinning
图 4 华山松和油松叶氮含量N对林窗式疏伐的响应
Figure 4. Leaf nitrogen content responses of Pinus armandii and P. tabuliformis to gap-model thinning
华山松1年生叶LMA、Chl a、Chl b、Chl a+b、Chl a:b、N含量在不同林窗疏伐处理间均无显著差异(图 1、3、4),SG显著提高了其Amax和PNUE(图 2b)。IG和SG边缘华山松2年生叶LMA、N含量与对照林木差异不显著(图 1c和图 4c),但其叶绿素含量显著低于对照(图 3),Amax和PNUE高于对照(图 2c)。
油松叶LMA、叶绿素含量、N、Amax高于华山松,油松1年生和2年生叶对林窗疏伐的响应也与华山松存在很大差异。油松1年生叶LMA和PNUE在对照样地和林窗样地差异不显著(图 1b和图 2b),但IG边缘油松1年生叶叶绿素和N含量显著高于CK(图 3和图 4),IG和SG边缘叶Amax显著高于CK(图 2b)。油松2年生叶LMA、N含量在不同林窗疏伐处理间没有显著差异(图 1c和图 4c),但SG边缘油松1年生叶绿素含量低于CK(图 3),Amax和PNUE略高于CK(图 2c和图 2f)。
华山松、油松不同叶龄针叶光合特性对林窗式疏伐的响应
Differential Responses of Age-related Leaf Photosynthetic Characteristics of Pinus armandii and Pinus tabuliformis to Gap-model Thinning
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摘要:
目的 通过对比研究华山松和油松不同叶龄针叶形态、光合速率、叶绿素和叶氮含量对林窗式疏伐的响应,探讨林窗大小、叶龄和树种对林窗式疏伐后叶光合特性响应的影响。 方法 2008年在30年生华山松和油松混交人工林中,设置对照、小林窗(80 m2)和中林窗(110 m2)处理,2013年以对照样地内和林窗边缘华山松和油松为研究对象,测定其当年生、1年生和2年生叶比叶重(LMA)、单位叶面积叶绿素a(Chl a)、叶绿素b含量(Chl b)、氮含量(N)、最大净光合速率(Amax)、光合氮利用效率(PNUE)等指标。 结果 小林窗和中林窗疏伐对叶光合特性影响一致,均对当年生叶影响不显著,但显著改变了1年生和2年生叶绿素含量、N和PNUE,提高了其Amax。华山松叶LMA、叶绿素含量、N、Amax均低于油松,两树种多年生叶对林窗式疏伐的响应也明显不同:林窗边缘华山松1年生和2年生叶LMA和N与对照差异不显著,但叶绿素含量低于对照,PNUE和Amax显著高于对照;林窗边缘油松1年生和2年生叶LMA和PNUE与对照差异不显著,但N和Amax显著高于对照。 结论 80~110 m2林窗疏伐显著改变叶光合特性,提高其光合潜力;林窗疏伐影响1年生和2年生叶光合特性,对当年生叶影响不显著;华山松和油松对林窗式疏伐的响应特征存在差异。 Abstract:Objective To study the responses of age-related leaf morphology, photosynthetic rate, photosynthetic pigments, and leaf nitrogen of Pinus armandii and P. tabuliformis to gap-model thinning, intending to explore the influences of gap size, leaf age, and species on leaf characteristics after thinning. Method The small gaps (80 m2), intermediate gaps (110 m2) and a control were set in a 30-year-old mixed P. tabuliformis and P. armandii plantation in 2008. The P. armandii and P. tabuliformis in control plots and gap-edged pines were chosen as test materials, and the leaf mass per area (LMA), area-based chlorophyll a, chlorophyll b, nitrogen content (N), maximum photosynthetic rate (Amax), and photosynthetic nitrogen use efficiency (PNUE) of current year, one-year-old, and two-year-old leaves were measured in 2013. Result Small and intermediate gaps had no significant influences on current-year leaves of P. armandii and P. tabuliformis, while significantly altered chlorophyll, N content, and PNUE, enhanced Amax of one-year-old and two-year-old leaves. P. armandii had lower LMA, chlorophyll content, N, and Amax. Moreover, older leaves of P. armandii and P. tabuliformis showed differentiated responses to gap-model thinning:gap-edged P. armandii showed lower chlorophyll content, higher Amax and PNUE than the control, while the LMA and N were no significantly different with the control; gap-edged P. tabuliformis had higher Amax and N than the control, while LMA and PNUE had no obvious difference with the control. Conclusion Gaps in size of 80-110m2 can alter the leaf characteristics and improve its photosynthetic capacity. Gap-model thinning has significant influences on the older leaves, while has no influence on current leaves. P. armandii and P. tabuliformis have different responding strategies to gap-model thinning. -
表 1 叶光合特性线性混合模型分析的F值
Table 1. F values based on linear mixed-effect model analyses for leaf photosynthetic characteristics
项目
Items比叶重
LMA叶绿素a
Chl a叶绿素b
Chl b叶绿素a+b
Chl a+b叶绿素a:b
Chl a:b氮含量
N最大净光合速率Amax 光合氮利用效率PNUE 树种Species 28.097** 44.412** 55.007** 46.437** 5.865* 14.948** 5.616* 1.315 叶龄Age 27.315** 3.870* 5.205** 4.574* 14.558** 0.684 33.365** 12.770** 林窗大小Gap size 0.804 5.135* 6.770* 5.748* 4.215* 1.379 4.026* 1.554 树种×叶龄Species×Age 0.518 2.075 2.739 2.047 0.772 1.836 0.342 0.828 树种×林窗大小
Species×Gap size0.474 1.202 0.956 1.112 0.612 0.212 0.165 1.425 年龄×林窗大小
Age×Gap size1.091 3.457* 3.920** 3.951** 0.154 1.954 1.323 1.935 树种×年龄×林窗大小
Species×Age×Gap size1.093 1.394 1.320 1.396 1.248 1.034 0.896 1.531 *P < 0.05, **P < 0.01 -
[1] Jones T A, Thomas S C. Leaf-level acclimation to gap creation in mature Acer saccharum trees[J]. Tree Physiology, 2007, 27(2):281-290. doi: 10.1093/treephys/27.2.281 [2] Medhurst J L, Beadle C L. Photosynthetic capacity and foliar nitrogen distribution in Eucalyptus nitens is altered by high-intensity thinning[J]. Tree Physiology, 2005, 25(8):981-991. doi: 10.1093/treephys/25.8.981 [3] Li M H, Krauchi N, Dobbertin M. Biomass distribution of different-aged needles in young and old Pinus cembra trees at highland and lowland sites[J]. Trees-Structure and Function, 2006, 20(5):611-618. doi: 10.1007/s00468-006-0076-0 [4] Sellin A. Morphological and stomatal responses of Norway spruce foliage to irradiance within a canopy depending on shoot age[J]. Environment Experiment and Botony, 2001, 45(2):115-131. doi: 10.1016/S0098-8472(00)00086-1 [5] Drenkhan R, Kurkela T, Hanso M, et al. The relationship between the needle age and the growth rate in Scots pine (Pinus sylvestris): a retrospective analysis by needle trace method (NTM)[J]. European Journal of Forest Research, 2006, 125(4):397-405. doi: 10.1007/s10342-006-0131-9 [6] Canhanm C D, Denslow J S, Plantt W J, et al. Light regimes beneath closed canopies and tree-fall gaps in tmperate and tropical forests[J]. Canadian Journal of Forest Research, 1990, 20(5):620-631. doi: 10.1139/x90-084 [7] Gray A N, Spies T A, Easter M J, et al. Microclimatic and soil moisture responses to gap formation in coastal Douglas-fir forests[J]. Canadian Journal of Forest Research, 2002, 32(2):332-343. doi: 10.1139/x01-200 [8] 陈梅, 朱教君, 闫巧玲, 等.辽东山区次生林不同大小林窗光照特征比较[J].应用生态学报, 2008, 19(12):2555-2560. [9] 刘聪, 朱教君, 吴祥云, 等.辽东山区次生林不同大小林窗土壤养分特征[J].东北林业大学学报, 2011, 39(1):79-81. doi: 10.3969/j.issn.1000-5382.2011.01.025 [10] Zhao Q X, Pang X Y, Bao W K, et al. Effects of gap-model thinning intensity on the radial growth of gap-edge trees with distinct crown classes in a spruce plantation[J]. Tree-Structure and Function, 2015, 29(6):1861-1870. doi: 10.1007/s00468-015-1267-3 [11] Rabelo G R, Vitória Ậ P, da Silva M V A, et al. Structural and ecophysiological adaptations to forest gaps[J]. Trees, 2013, 27(1):259-272. doi: 10.1007/s00468-012-0796-2 [12] Chen J W, Kuang S B, Long G Q, et al. Steady-state and dynamic photosynthetic performance and nitrogen partitioning in shade-demanding plant Panax notoginseng under different levels of growth irradiance[J]. Acta Physiologiace Plantarum, 2014, 36(9):2409-2420. doi: 10.1007/s11738-014-1614-9 [13] 唐敬超, 史作民, 罗达, 等.遮荫处理对灰木莲幼苗叶片光合氮利用效率的影响[J].生态学报, 2017, 37(22):1-10. [14] Han Q, Chiba Y. Leaf photosynthetic responses and related nitrogen changes associated with crown reclosure after thinning in a young Chamaecyparis obtusa stand[J]. Journal of Forest Research, 2009, 14(6):349-355. doi: 10.1007/s10310-009-0146-4 [15] Puchalska E, Czajkowska B, Kielkiewicz M. Morphological, anatomical and chemical characterization of white spruce (Picea glauca 'Conica') differently aged needles and hypotheses on their influence on Oligonychus ununguis infestation[J]. Acta Physiologiae Plantarum, 2008, 30(2):225-232. doi: 10.1007/s11738-007-0111-9 [16] Li C, Wu C, Duan B, et al. Age-related nutrient content and carbon isotope composition in the leaves and branches of Quercus aquifolioides along an altitudinal gradient[J]. Trees, 2009, 23(5):1109-1121. doi: 10.1007/s00468-009-0354-8 [17] Mediavilla S, Gonzalez-Zurdo P, Garcia-Ciudad A, et al. Morphological and chemical leaf composition ofMediterranean evergreen tree species according to leaf age[J].Trees, 2011, 25(4):669-677. doi: 10.1007/s00468-011-0544-z [18] Li R S, Yang Q P, Zhang W D, et al. Thinning effect on photosynthesis depends on needle ages in a Chinese fir (Cunninghamia lanceolata) plantation[J]. Science of the Total Environment, 2017, 580:900-906. doi: 10.1016/j.scitotenv.2016.12.036 [19] Goudiaby V, Brais S, Grenier Y, et al. Thinning effects on Jack Pine and Black Spruce photosynthesis in Eastern Boreal Forests of Canada[J]. Silva Fennica, 2011, 45(4):595-609. [20] 衣宁, 赵文倩, 刘倩, 等.油松新生叶与老叶光合功能的比较[J].林业科技, 2014, 39(6):10-14. [21] 赵庆霞, 包维楷.华山松和油松冠型结构对林窗式疏伐的响应[J].四川农业学报, 2016, 34(1):24-28. [22] 谭辉, 朱教君, 康宏樟, 等.林窗干扰研究[J].生态学杂志, 2007, 26(4):587-594. doi: 10.3321/j.issn:1000-4890.2007.04.025 [23] 唐艳, 王传宽.东北主要树种光合作用可行的离体测定方法[J].植物生态学报, 2011, 35(4):452-462. [24] 刘秀丽, 宋平, 孙成明, 等.植物叶绿素测定方法的探讨[J].江苏农业研究, 1999, 20(3):46-47. [25] Gravatt D A, Chambers J L, Barnett J P, et al. Temporal and spatial patterns of net photosynthesis in 12-year-old loblolly pine five growing seasons after thinning[J]. Forest Ecology and Management, 1997, 97(1):73-83. doi: 10.1016/S0378-1127(97)00055-8 [26] Peterson J A, Seiler J R, Nowak J, et al. Growth and physiological responses of young loblolly pine stands to thinning[J]. Forest Science, 1997, 43(4):529-534. [27] Tang Z M, Chambers J L, Sword M A, et al. Seasonal photosynthesis and water relations of juvenile loblolly pine relative to stand density and canopy position[J]. Trees-Structure and Function, 2003, 17(5):424-430. doi: 10.1007/s00468-003-0256-0 [28] Niinemets ü, Cescatti A, Rodeghiero M. Leaf internal diffusion conductance limits photosynthesis more strongly in older leaves of Mediterranean evergreen broad-leaved species[J]. Plant Cell and Environment, 2010, 28(12):1552-1566. [29] Ethier G J, Livingston N J, Harrison D L, et al. Low stomatal and internal conductance to CO2 versus Rubisco deactivation as determinants of the photosynthetic decline of ageing evergreen leaves[J]. Plant Cell and Environment, 2010, 29(12):2168-2184. [30] 李勇, 韩海荣, 唐峰峰, 等.油松人工林冠层光合生理特性的空间异质性[J].东北林业大学学报, 2013, 41(4):32-35. doi: 10.3969/j.issn.1000-5382.2013.04.008 [31] 梁军生, 陈晓鸣, 杨子祥, 等.云南松与华山松人工混交林针叶光合速率对光及CO2浓度的响应特征[J].林业科学研究, 2009, 22(1):21-25. doi: 10.3321/j.issn:1001-1498.2009.01.004