Abstract: Studying the clonal growth characteristics of rhizomatous grasses would help understand their adaptive strategy. In this study, we selected three rhizomatous grasses based on examining the aboveground and belowground clonal growth patterns from 24 rhizomatous grass species. After that, we conducted a field experiment to monitor the seasonal variations of bud banks and clonal traits of the three rhizomatous grasses using a soil-unit exaction sampling method. The results showed that: (1) there were three types of clonal growth patterns, i.e., type Ⅰ, short rhizo matous grasses with horizontal expansions (Bromus inermis), type Ⅱ, long rhizomatous grasses with horizontal expansions (Leymus secalinus), and type Ⅲ, long rhizomatous grasses with spatial layer expansions (Pennisetum centrasiaticum). (2) P. centrasiaticum had the highest tiller density (540-680 tillers·m^-2), internode density (3200-4600 internodes·m^-2) and total bud density (350-1000 buds·m^-2) among three rhizomatous grasses, indicating the strongest spatial clonality (P≤0.05). L. secalinus had a higher internode density (1300-1700 internodes·m^-2) and internode length (3.5-4.0 cm) than that (70-320 internodes·m^-2, 1.0-1.5 cm) of B. inermis (P≤0.05), showing a higher clonality with rhizome expansions relative to the latter. (3) B. inermis displayed a phalanx growth form with a positive relationship between tiller density and axillary shoot bud, and a negative relationship between tiller density and vertical apical rhizome bud (P≤0.05). L. secalinus had a phalanx-guerilla growth form with positive relationships of tiller density (or internode density) with axillary shoot bud, axillary rhizome bud, vertical apical rhizome bud, and horizontal apical rhizome bud. P. centrasiaticum had a guerilla growth form with a positive relationship of tiller density (or internode density) with axillary rhizome bud. In the study site with the characteristics of drought, high temperature in summer, cold in winter, and nutrient-poor soil, L. secalinus, featured with phalanx-guerilla clonal growth, can monopolize resources, exploit patchy resources and develop dominant populations more easily than two other species. Understanding the clonal growth characteristics through analyzing the structure and quantitative relations among bud banks and clonal traits is essential for revealing species distribution within communities and thus provides a useful reference for the restoration of degraded grasslands.

Key words: bud bank density, tiller density, internode density, clonal growth pattern.