两种亚热带榕属乔木植冠损伤后的位置依赖性枝发生

三峡库区需要大量植株用于三峡工程所涉及的诸多建设(如铁路、公路、建筑)之后的植被恢复和绿化。由于具有优美树冠和耐瘠薄土壤的能力,榕(Ficus microcarpa L.)和黄桷树(F. virens Ait. var. sublanceolata (Miq.) Cornor)在三峡库区作为绿化和行道树木大量栽植。在三峡库区,这两种树种苗木的培育主要通过切枝扦插的方式进行。大量切枝损伤植株植冠并且使叶组织数量减少,对植株生长有很大影响。植株生长与植株的枝发生格局有很大关系,为明确植冠损伤对植株生长的可能影响,对榕和黄桷树植冠损伤后的枝发生进行了研究。实验发现,切枝造成的植冠损伤对榕和黄桷树植株侧枝上的枝发生没有影响,不同损伤强度之间和不同损伤发生时间之间都不存在明显的差异。但是,植冠损伤后,榕和黄桷树植株主茎上的枝发生是位置依赖性的。植冠损伤不影响榕和黄桷树植株损伤处理后新生主茎段和具侧枝主茎段上的枝发生,却促进了损伤处理后裸露主茎段上的枝发生,并且裸露主茎段上枝发生的数量和密度随植冠损伤强度的升高而增大。此外,实验结果表明, 秋季植冠损伤植株裸露主茎段上的枝发生要高于春季植冠损伤植株裸露主茎段上的枝发生; 在榕和黄桷树的枝发生中,仅有裸露主茎段上增强的枝发生会促进植冠损伤植株对叶组织的生物量投

Position-dependent Shoot Production of Two Subtropical Fig Tree Species Following Crown Damage

In Three Gorges reservoir region, a great many of trees are needed for vegetation restorationand land greening following the massive constructions (e.g. construction of roads, highways, buildings)associated with the great dam project at Three Gorges of Yangtze River. Ficus microcarpa L. and F. virensAit. var. sublanceolata (Miq.) Cornor (Moraceae) are chosen and widely planted in this region as ornamentaltrees and/or shade trees due to their shapely crowns and ability of growing on soils with low fertility.Vegetative multiplication, which uses branch cuttings to cultivate saplings, is the main way for treepropagation of the two species in Three Gorges reservoir region. Obtaining branch cuttings causes thedamage of tree crown and probably affects the growth of trees. In this study, the shoot production patternof two Ficus tree species following crown damage, which is crucial to the regrowth of trees, was investigated.Data from a crown damage experiment with two damage seasons and a series of damage intensities wereanalyzed. It was shown that crown damage, regardless of damage intensity and damage season, had noeffect on the shoot production of lateral branches of both species. However, the shoot production on themain stem was position-dependent in both F. microcarpa and F. virens trees. Crown damage, conductedeither in spring or in autumn, did not affect the number and density of new shoots on the newly grownupper stem parts and the branched stem parts within the residual crown, but facilitated the shoot productionon the bare stem parts beneath the residual crown in terms of both shoot number and density. Shootproduction on the bare stem parts increased with damage intensity. In addition, it was found that damage inautumn led to a stronger emergence of shoots from the bare stem parts than spring damage. Somemechanisms which could be involved in these results are discussed. Based on the experimental results, itis suggested that among all investigated variables, only the enhanced shoot production on the bare stemparts may increase the biomass partitioning to leaves and benefit the regrowth of damaged trees.