Abstract:

Changes in the understory plant species diversity in Larix gmelinii pure plantations were investigated after carrying on a close-to-nature stand transformation with different gap sizes and various soil disturbances, with conventional uniform thinning as the control. Increases in species number, quantity, coverage, mean height and diversity indexes (Simpson’s diversity index, Shannon-Wiener index, Pielou’s evenness index) of herbaceous species were detected in the transformed stands in the 1^st and 2^nd year; and significant differences ( P <0.05) were detected for all the indices except for evenness index in the 2^nd year. Among the dominant herbaceous species, hygrophilous ones increased dramatically in the gaps of the transformed stands. No significant differences were found in species number, quantity, coverage, mean height and diversity index of herbaceous species with different gap size. In the 1^st year after transformation supplemented with scratching the floor, the herbaceous species had significantly greater quantity,coverage and mean height in comparison to that without scratching the floor; but the differences diminished in the 2^nd year. No significant differences in species number, quantity, coverage, mean height and diversity indexes of woody species were detected between the close-to-nature transformation and the ordinary uniform thinning. Our results suggest that the close-to-nature transformation favors the development of understory herbs, and promotes the diversity. However, more work should be done to determine the influence of the transformation and soil disturbances on the development of woody species.

Key words: Larix gmelinii, plantation forests, close-to-nature transformation, gap, uniform thinning, forest floor scratch, plant diversity