摘要
小枝与叶片间的关系能够很好地反映植物对环境的适应策略。目前,从枝叶间权衡关系的角度研究树木对庇荫环境适应性的报道尚少,其中主要包括"生长-生长"权衡和"生长-生存"权衡两种假说。因此,为了探讨灌木在庇荫环境中,是否会在小枝和叶性状间采取权衡策略,来提高光照资源的利用能力或增强生存和防御能力,在城市绿地的林隙和林冠下两种光环境中,选择了没有人工修枝、整形等经营措施的金银木(Lonicera maackii)、小花溲疏(Deutzia parviflora)和连翘(Forsythia suspensa)等11种、79株观赏灌木作为研究对象,采集其当年生小枝,观测并计算了每棵灌木所处环境的有效光合辐射(PAR)相对累积光量和红光/远红光(R/FR),以及灌木的小枝干重(TDW)、单位小枝叶干重(LDW)、出叶强度(LN/TDW)、叶面积支持效率(LA/TDW)、比枝长(TL/TDW)和单叶面积(ILA) 6个性状。对数据进行标准化和数据转换后,运用Pearson相关检验分析光环境指标和灌木枝叶性状间的相关性;采用标准化主轴估计法进行异速生长方程的参数估计;使用多元回归分析不同光强下各性状的相互关系。结果表明:(1) PAR相对累积光量和R/FR与TDW和LDW呈极显著(P<0.01或P<0.001)正相关,与TL/TDW、LA/TDW、LN/TDW呈极显著(P<0.001)负相关,与ILA相关性不显著(P> 0.05)。整体上,R/FR与各灌木性状的相关性大于PAR相对累积光量;(2) TDW和LDW存在极显著(P<0.001)的异速生长正相关关系。随着光强的减小,灌木当年生小枝和叶片的生物量都趋于减小,但是表现出相对偏向于叶片生物量的投资偏好;(3) LA/TDW和TL/TDW存在极显著(P<0.001)的等速生长正相关关系。但随着光强的减小,比枝长随叶面积支持效率增加而增加的速率却减小,说明灌木在庇荫条件下,更倾向于采取忍耐型的光资源利用策略;(4) ILA和LN/TDW呈极显著(P<0.001)异速生长负相关关系。随着光强的减小,灌木趋向于表现出单位小枝上着生大量小叶的现象。所以总体上,庇荫环境下的观赏灌木存在投资偏好和权衡,倾向于通过枝叶生长提高光截获能力来适应弱光环境,与"生长-生长"的权衡假说相符,但整体上,观赏灌木的耐阴性较差,故不建议种植在庇荫环境中。
Understanding the relationships between twig and leaf traits provides valuable insights into the adaptive strategies of plant species. There are limited studies addressing the shade tolerance of woody species regarding trade-offs between twig and leaf traits. However,there are two contrasting hypotheses regarding the characteristics of shade tolerance; whethershade-tolerant species prefer maximized light interception and low respiration in the shade or are characterized by tough structures because of a reduction in organ turnover and promotion of plant survival. In this study,our objectives were to reveal whether the twigs and leaves of shrubs exerted trade-offs in the shade. Thus,twig dry weight( TDW),leaf dry weight unit twig( LDW),leafing intensity( LN/TDW),specific twig length( TL/TDW),leaf area supporting efficiency( LA/TDW),and individual leaf area( ILA) were measured for 11 shrub species,which have a relatively high ornamental value and limited management under the canopy at the Beijing Forestry University campus. In addition,the relative light summation of photosynthetically active radiation( PAR) and spectral ratio of red light and far-red light( R/FR) were measured for the habitats of target shrubs. Relationships between twig and leaf traits were determined using standardized major axis estimation( SMA). Effects of shade on relationships between twig and leaf traits were estimated using a multiple regression analysis. The study showed that( 1) light( relative light summation of PAR and R/FR) has significant positive relationships( P<0.01) with TDW and LDW and significant negative relationships( P<0.001) with TL/TDW,LA/TDW,and LN/TDW,whereas no significant relationship( P>0.05) was observed with ILA. In addition,the interactions between light and traits were more significant for R/FR than the relative light summation for PAR;( 2) furthermore,there was a significant positive correlation( P < 0. 001) and allometric relationship between TDW and LDW. A direct relation was observed between light and biomass of twigs and leaves,as biomass of both significantly decreased with decreasing light.However,shrubs reflected a relative bias in investment of leaf biomass;( 3) LA/TDW also showed significant( P<0.001)positive correlations and isometric relationships with TL/TDW. However,the steepness for TL/TDW-LA/TDW relationships in the lower R/FR decreased,indicating that shrubs presented a relatively conservative strategy for light interception in the shade;( 4) ILA showed a significant( P<0.001) negative correlation and allometric relationship with LN/TDW,implying that the twigs of shrubs tended to be made up of many smaller leaves in the shade. Therefore,together,the trade-offs of ornamental shrubs were similar to the hypothesis that suggested shade-tolerant species exert trade-offs in growth performance.However,generally,the shade tolerance of these shrubs was too weak to allow them to grow in the shade as ornamental species.
作者
龙嘉翼
赵宇萌
孔祥琦
陈治羊
王秀松
赵凯
曹然
黄丽莎
吕娇
崔义
余玉磊
徐程扬
LONG Jiayi;ZHAO Yumeng;KONG Xiangqi;CHEN Zhiyang;WANG Xiusong;ZHAO Kai;CAO Ran;HUANG Lisha;LU Jiao;CUI Yi;YU Yulei;XU Chengyang(Key Laboratory for Forest Silviculture and Conservation of Ministry of Education,Beijing 100083,China;Key Laboratory for Silviculture and Forest Ecosystem in Arid and Semi-arid Areas of State Forestry Administration,Beijing 100083,China)
出处
《生态学报》
CAS
CSCD
北大核心
2018年第22期8022-8030,共9页
Acta Ecologica Sinica
基金
林业公益性行业重大专项(20140430102)