Seedlings Recruitment of a Timberline Tree (Larix chinensis Beissn) in Taibai Mountain, China

Larix chinensis Beissn forms a subalpine timberline on Taibai mountain, Shaanxi, China. Seed emergence and survival of seedlingswere studied by seed sowing experiments across an altitudinal gradient (3150–3400 m a.s.l). Three main factors were considered: seed addition, shrubshadowing and disturbance. In three different habitats (from low altitude to high: the Abies fargesiiforest, the Larix chinensis forest and the shrubmeadow), seeds emergence was examined and the seedlingnumber and growth in every plot were recorded continuously over 4 years. Kruskal-Wallis ANOVA was used to analyze the relationship between seedlingemergence/recruitment and the explanatory variables in every stand. The results showed that seed addition in disturbed plots always caused significantly increased seedlingemergence and recruitment in the A. fargesii forest and the L. chinensis forest, but not in undisturbed plots under the canopy of forests. It demonstrated that recruitment of L. chinensis was limited by seed and micrositeavailability under closed forest, and litter is one of the factors leading to micrositelimitation. However, in the shrubmeadow, no treatments improved recruitment, indicating that the shrubmeadow was not suitable for seedlingestablishment because of more intense light and lower temperature. In the L. chinensis forest and the A. fargesii forest, more recruited seedlingsindicated that these two forests are safer for L. chinensis seedlingestablishment, though seeds limitation and the litter obstacle had seriously constrained the regeneration of L. chinensis.