断根对杨树切口处细根序级结构与形态特征的影响

Effect of root pruning on the architecture and morphological characteristics of different fine root orders in the incision of poplar trees

为探讨断根对欧美I-107杨切口处细根序级结构和形态特征的作用效果,通过大田试验,研究4-2（4倍胸径两侧）、6-2（6倍胸径两侧）、8-2（8倍胸径两侧）、10-2（10倍胸径两侧）和12-2（12倍胸径两侧）等不同断根处理对杨树切口处1-5级根的分支比例、直径、根长和比根长的影响.结果表明,同对照（未断根）相比,各断根处理的细根不同序级分支比例均呈升高的趋势,其中8-2处理的各分支比例均显著高于其他处理.随着根序的升高,各处理的细根直径和根长逐渐增大,而比根长却减小.在断根处理中,8-2处理1-2级根的直径和根长最小、比根长最大,而3-5级根的直径和根长最大、比根长最小,并均与其他处理差异达显著水平;4-2、6-2、10-2和12-2处理1-2级根之间的直径、根长和比根长均无显著性差异;而4-2和12-2处理3-5级根的直径和根长显著小于6-2和10-2处理,比根长则显著高于6-2和10-2处理.此外,8-2处理的材积平均生长率显著高于其他处理.综上,断根强度对杨树切口处不同根序细根的分支结构和形态特征具有显著的影响,其中8-2处理更利于切口处细根的萌发,并能显著增强根系的吸收能力与运输功能,进而有助于促进林木的生长;本研究结果可为杨树人工林的高产栽培提供技术参考.

This study investigated the effects of root pruning on the architecture and morphological characteristics of different fine root orders in the incision of Populus euramericana ＇Neva.＇ A field experiment was designed and performed. The root systems of five-year-old poplars were manually pruned with a sharp spade at four （4-2）, six （6-2）, eight （8-2）, ten （10-2）, and twelve （12-2） times the diameter at breast height （DBH） respectively, along both inter-row sides, to investigate the effects of different root pruning treatments on branching ratios, diameter, length, and specific root length of the first five root orders in poplar incision. The results showed that in comparison with the unpruned control （CK）, each root pruning treatment caused an increase in the branching ratios of fine root orders, which were highest in roots under the 8-2 treatment. With the increase of root order, root diameter and length increased gradually, while the specific root length decreased. The root diameter and length of the first two orders of 8-2 treated roots were the lowest, and the specific root length was the highest in the same group. However, a reverse trend was observed from the third to fifth root orders; all of which showed statistically significant differences in characteristics compared with the other treatments. There was no significant difference in root diameter, length, or specific root length among the treatments of 4-2, 6-2, 10-2, and 12-2. Root diameter and length from the third to fifth root orders under the 4-2 and 12-2 treatments were significantly lower than those of roots under the 6-2 and 10-2 treatments, whereas the specific root lengths were notably higher. Additionally, the average increase in the volume of 8-2 treated roots was significantly higher than the volume of roots under other treatments. To sum up, pruning intensity significantly affects the architecture and morphological characteristics of different branch orders of fine roots during the incision of P. euramericana ＇Neva.＇ Root pruning at adistance of eight times the DBH along both inter-row sides is more beneficial to the germination of fine roots in the incision and can significantly enhance the absorption ability and transport function of root systems, thus promoting the growth of P. euramericana ＇Neva.＇ This study provides technical reference for the high-yield cultivation in poplar plantations.