根系功能性状对干瘠立地适应的种间差异--以北京石质山地主要观赏树种为例

Interspecific trait variation in the adaptation of root functional traits to dry⁃barren sites:A case study of the main ornamental tree species in stony mountainous region of Beijing

分析干瘠立地中不同树种根功能性状的变化及差异,研究不同树种对干瘠环境的适应对策。试验材料为林龄、林分密度相对一致的石质山区主要观赏树种(黄栌、山桃、栓皮栎),采用挖掘法获取树木细根,测定细根形态参数。根据田间持水量和石砾含量分别设置4个干瘠梯度(轻度、中度、重度、极度),对比分析北京干瘠地3种树种根功能性状,探讨干瘠立地中不同树种根系形态的差异及其对特殊生境的适应。结果表明:干旱、瘠薄均对树木的根功能性状产生影响,但对不同性状以及不同树种的影响程度具有差异,其中对山桃根系的影响最大;3种树种根功能性状在不同干瘠等级下存在显著变化,同一性状的变化因树种不同而异。从轻度到极度干旱,3种树种的RL均逐渐减小,但是黄栌变化不显著;黄栌、栓皮栎RTD随干瘠的加剧而减小,而山桃随干瘠的加剧而增加;黄栌和山桃SRL随干旱、瘠薄的加剧,表现出一致的规律,即从轻度到极度,其SRL随即减小,而栓皮栎SRL随干旱、瘠薄的加剧而增大;随干瘠的加剧,黄栌SRA显著减小,山桃、栓皮栎SRA随干瘠的加剧而增大。树木对干瘠环境的变化都有一定的响应能力及适应对策,能够通过自身的形态变化来适应不断变化的环境,但不同物种对干瘠环境变化的适应途径不同,通过权衡碳分配、碳消耗采取了相应的生态适应策略,不同树种间存在明显差异。本研究3种树种中,黄栌在干瘠环境下根系性状变化不显著,耐干瘠能力较强;干瘠胁迫对山桃根系性状影响显著,山桃通过主动调节根系形态变化来适应不断变化的环境,具有较强的抗干瘠能力;栓皮栎的细根数量多,吸收土壤水分、养分能力较强,能够在干瘠环境中快速生长。

The changes and differences of root functional traits of different tree species in dry⁃barren site were analyzed,and the adaptive strategies of different tree species to dry⁃barren environment were studied.The experimental materials were mainly ornamental tree species(C.coggygria,Amygdalus davidiana and Quercus variabilis)in the shallow mountain area with same age and stand density.Fine roots of trees were obtained by digging,and morphological parameters of fine roots were measured.According to the field water holding capacity and gravel content of the sample plots,four dry and barren gradients(light,moderate,heavy and extreme)were set.The root functional traits of three ornamental tree species were analyzed and compared,and then the difference of root morphology of different tree species in dry⁃barren site and their adaptability to special habitats were studied.The results showed that drought and barrenness had an impact on the root functional traits of trees,but the degree of influence on different traits and different tree species was different,and the impact on Amygdalus davidiana was the largest;The root functional traits of the three tree species varied significantly under different dry⁃barren grades,and the change of the same traits varied with tree species.From mild drought to extreme drought,the root link length(RL)of the three tree species decreased gradually,but the change of C.coggygria was not significant;The root tissue density(RTD)of C.coggygria and Quercus Variabilis variabilis decreased with the increase of dry and barren,but the Amygdalus davidiana increased with the increase of dry and barren;The specific root length(SRL)of C.coggygria and Amygdalus davidiana decreased from mild to extreme,and the SRL of Quercus variabilis increased with the increase of drought and barrenness;The specific root area(SRA)of C.coggygria increased with the increase of dry and barren soil,while the SRA of Amygdalus davidiana and Quercus variabilis decreased with the increase of dry and barren.Trees had a certain ability to respond and adapt to changes in dry⁃barren environments,which could adapt to the changing environment through their own morphological changes.Different species had different ways to adapt to the dry⁃barren environment,corresponding ecological adaptation strategies were adopted by balancing carbon allocation and carbon consumption.There were obvious differences between different tree species.Of the three tree species in this study,the root functional traits of C.coggygria did not change significantly in dry⁃barren environment,and the ability to tolerate dry and barren was strong;Dry and barren stress had a significant impact on the root traits of Amygdalus davidiana.By actively adjusting the morphological changes of the root system to adapt the changing environment,Amygdalus davidiana had a strong ability to resist dryness and barren;The fine roots of Quercus variabilis were abundant,so it could absorb soil moisture and nutrients,and could grow quickly in dry⁃barren environment.