Abstract: The elevational differentiation pattern of understory plant diversity and its relationship with soil factors are vital for diversity research of forests. We examined understory plant diversity and soil factors at different elevations (400-600, 600-800, 800-1000, and 1000-1220 m) and their relationship in a sandstone peak forest in the Zhangjiajie National Forest Park. The results showed that: (1) species with the highest importance values in the shrub and herbaceous layers differed among elevations, with the richest understory species in the 1000-1220 m elevation and the poorest in the 400-600 m elevation; (2) the diversity index H and richness index D of the shrub and herbaceous layers differed significantly among elevations (P<0.05), while the dominance index H′ and uniformity index J_sw were not significantly different (P>0.05); (3) total phosphorus (TP), magnesium (TMg), and calcium (TCa) contents were significantly different (P<0.05), while soil pH, total potassium (TK), total nitrogen (TN), total carbon (TC), N/P, C/P, and C/N ratios were not significantly different (P>0.05) among elevations; (4) Elevation and soil C content were the main environmental factors affecting herbaceous diversity differentiation, but shrub diversity was not affected by environmental factors. Our results indicated a certain correlation between understory plant diversity and environmental factors, and provided a new consideration for the study of species diversity in the sandstone peak forest area.

Key words: sandstone peak forest, elevation gradient, understory plant diversity, soil factor, redundancy analysis.