Root Adaptability of Clonal Plant Iris japonica and Its Role in Understory Vegetation Restoration in Chongqing, SW China

A clonal herb species, Iris japonica, is used for constructing understory horticultural landscape, and it has high adaptability in understory condition. Root characteristics differences between I. japonica and other herb species in two typical natural habitats, Open area at forest edge (OAFE) and Bamboo forest (BF) were carried out on Jinyun Mountain, Chongqing, China, and a reciprocal transplant-replant experiment was conducted to investigate root production and adaptability of above two populations. The results were as follows: Root length density, surface area density, volume density, biomass density and below-ground biomass ratio of I. japonica were significantly higher than those of total other herbs in two habitats (p <; 0.05). Root characteristics (length density, surface area density and volume density) of both I. japonica and total other herbs in BF were significantly higher than those in OAFE (p <; 0.05). Root characteristics of coarse root (D > 2 mm), fine root (D <; 2 mm) and all 7 root diameter classes of I. japonica were significantly higher in BF than those in OAFE (p <; 0.05). Root length (density or ratio), surface area (density or ratio) and volume (density or ratio) were significantly higher in fine root than in coarse root, whether OAFE or BF habitats. Root characteristics and root biomass density of BN and BS were significantly higher than those of ON and OS (p <; 0.05). Even root system of ON and OS were well-developed. Origin types had significant effect on coarse root (length, surface area, volume and RLD), both Origin and Growth habitat had effect on all features of fine root. Therefore, I. japonica can develop dominant root system, and it has the high root adaptability through its clonality in different habitats, which indicate that clonality well-developed population may play significant role in understory vegetation restoration (with moderate shading) for improvement soil space by large root system.