Abstract: [Objective] As one of the important factors of stand structure, stand density has an important effect on forest ecosystem function. By analyzing and evaluating of soil quality indicators of Phyllostachys edulis forests under different long-term managements of stand density, the study was aimed to reveal the causes and mechanisms of the effects of stand density on forest sustainable productivity, and to provide theoretical basis for proper stand density management.[Method] In this paper, four P. edulis stands with stand densities of 1 200, 1 800, 2 400 and 3 000 individual·hm^-2 were selected and 18 soil quality indicators (including soil physical properties, pH-value, nutrient contents and enzyme activities) were examined in Huangshan, Anhui Province of China. One-way ANOVA was conducted to test the significance of the indicators, while the least significant difference (LSD) was applied for multiple comparisons. The indicators under different stand densities were calculated using fuzzy mathematics and multivariate statistical analysis to evaluate the soil quality.[Result] No consistent pattern of changes with stand densities were found for the soil physical properties. Soil bulk density of the stand density of 3 000 individual·hm^-2 was the largest (1.10 g·cm^-3) among the four stand densities. Soil bulk density increased with the increase of soil depth for the same stand density. Soil moisture and total porosity of the stand density of 2 400 individual·hm^-2 were the largest and decreased with the increase of soil depth. Soil pH-value and total nitrogen (N) content increased gradually with the increase of stand densities, while the content of soil organic matters, total phosphorus (P), total potassium (K), available N, available P and available K first increased and then decreased slightly; the activities of five soil enzymes, including urease, sucrase, protease, catalase and acid phosphatase, also showed a similar pattern of changes with stand densities, namely increasing first and then decreasing or stabilizing. Under the same stand density, soil nutrient contents and enzyme activities were also correlated to soil depth. The content of soil organic matters, available N, available P, available K, total P and the activities of enzymes declined with increasing soil depth. The comprehensive analysis indicated that, at the soil depth of 0-60 cm, the comprehensive evaluation index also increased firstly, and then decreased with the increase of stand densities, and the index for the stand density of 2 400 individual·hm^-2 was the largest (0.585 3) among the four stand densities, suggesting that optimal stand density could contribute to improving the soil quality in P. edulis forests. At the soil depth of 0-20 cm, the soil quality was significantly higher than the other two layers beneath under the same stand density.[Conclusion] Stand density control was an important measure for forest management. A long-term management with an appropriate stand density can be helpful for optimizing the stand structure, fully utilizing the environment factors within forest ecosystems, and improving the growth of understory vegetation and litterfall and nutrient cycling. In this study area, the soil quality differed significantly among different stand densities in P.edulis forests, and a proper density of 2 400 individual·hm^-2 would be beneficial to improve the soil quality.

Key words: Phyllostachys edulis, density, comprehensive index of soil quality, evaluation