Abstract: Forest gaps in karst region, commonly formed after medianand small scale disturbance, are important places where woody species could regenerate and exist. Exploring the maintenance and driving forces of woody species diversity has a great significance. In this study, we investigated the gap characteristics and calculated the α diversity of woody species in the gaps in the evergreen and deciduous broadleaved mixed forest in Maolan National Nature, to clarify the relationship between gap characteristics and woody species diversity. We further analyzed the effects of habitat factors on woody species diversity in the forest gaps. The results showed that Lindera communisand Nandina domestica, which had positive regeneration responses to gaps, were the dominant species in gaps. The gaps with larger area and middle age had higher woody species diversity. The accumulating explanatory rate of forest gap characteristics, topographic factors and karst microhabitat was 66.6%. Among which, the explanatory rate of gap characteristics was 36% (gap size alone accounted for 28.2%), that of topographic factor was 23.3% and that of karst microhabitat was 1.9%. The results indicated that gap characteristics were the main driving force of woody species diversity. Therefore, forest gaps with different sizes could be artificially established to promote woody species regeneration in karst forests. Our findings revealed the mechanism of natural regeneration of woody species in degraded karst forests.

Key words: karst forest, gap characteristics, topographic factor, karst microhabitat, woody species diversity.