Root Growth of Quercus variabilis Seedlings in Response to the Environmental Heterogeneity | 栓皮栎幼苗根系发育对环境异质性的响应

Chinese. 为了阐明生境差异对栓皮栎幼苗根系生长的影响,在秦岭南坡（商州林区）,秦岭北坡高、中、低海拔地区（太白山和楼观台林区）,以及黄土高原（黄龙林区）设置样地,对1～ 4年生栓皮栎幼苗根系的形态和干质量进行测定,分析不同区域的根系发育特点及其与生境因素的关系。结果表明：随着纬度由南向北和海拔由低到高,幼苗生长减缓,根系形态指标和干质重下降;在秦岭南坡,栓皮栎幼苗直径≤0.5 mm侧根数量、表面积和长度最大,而在秦岭北坡低海拔地区幼苗〉1 mm的侧根数量和表面积最大;在秦岭北坡高海拔地区,栓皮栎幼苗侧根数量、表面积、长度和干质量均较小,而比根长最大;在黄土高原,幼苗主根和侧根的各项特征较小。通过PCA对10个环境因子降维,前3个主分量可以解释影响幼苗生长因素的85.2%。Pearson相关系数表明：年均温度、年均积温与幼苗主根和侧根干质量正相关;土壤中速效氮和速效磷含量分别与侧根长度、比根长和表面积呈显著正相关。温暖生境更有利于栓皮栎幼苗根系干物质的积累,增加林地土壤氮、磷含量,可以促进栓皮栎根系发育。

English. One-year- to four-year-old seedlings of Chinese cork oak（ Quercus variabilis） were sampled in high,medium,and low altitudes in the northern slope of Qinling Mountains,Loess Plateau and the southern slope of Qinling Mountains. The morphology and dry weight of the seedlings roots were measured to investigate the effects of various environmental factors on the root growth. The results showed that the roots morphological parameters and dry weight decreased with the increasing latitude and altitude. The seedlings in the southern slope of Qinling Mountains had most number of lateral roots with diameter ≤0. 5 mm and the largest surface area and longest length. The seedlings in the low altitude of the northern slope of Qinling Mountains had the greatest number and largest surface area of lateral roots with diameter 1 mm. The seedlings in the high altitude of northern slope of Qinling Mountains had relatively less root number,smaller surface area,shorter length and lighter weight of lateral roots,however their specific root length of lateral roots were greater than that in other sites. The morphology and weight of both seedling tap and lateral roots were the minimum value in Loess Plateau. Through the Principle Components Analysis（ PCA）,10 environmental factors were reduced to the three principle components that interpreted 85. 2% of variance of seedling growth. The annual temperature and accumulated temperature exerted stronger positive effect on the biomass accumulation of both tap and lateral roots.Phosphorus content in the soil was positively correlated with the specific root length and surface area of lateral roots,while the nitrogen content had significant positive effect on lateral root length. It is concluded that appropriate temperature favors the biomass accumulation of seedling roots,and higher contents of phosphorus and nitrogen are favorable to the growth of lateral roots.