关键词: 人参根际土壤, 酚酸物质, 人参锈腐病, 化感效应, 连作障碍

Abstract: Based on the Landsat datasets in five different periods during the past four decades in combination with the plot investigation data along the main stream of Tarim River, Xinjiang, this paper explored the dynamic change of desert riparian vegetation. The results showed that: (1) The mean vegetation coverage along the main stream of Tarim River was about 15%, with a significant spatial variation. The vegetation coverage was the highest (20%) in the upstream area, and the lowest (9%) in the downstream area, and re〖JP2〗ached up to 17% on the north side and 12% on the south side. In addition, vegetation zone width had the same distribution patterns as the vegetation coverage. (2) The vegetation coverage had an increased trend in the main stream area of Tarim River, with an average rising rate of 0.0038·10 a^-1. The vegetation coverage in the upstream and midstream areas increased at 0.0083·10 a^-1 and 0.0013·10 a^-1, respectively, while the vegetation coverage in the downstream had a decline trend, with a decline rate of -0.0003·10 a^-1. (3) The lowmedium vegetation coverage reflecting desert riparian forest was in a declined trend, while the high vegetation coverage reflecting farmland and artificial vegetation had a rising trend. (4) The expansion of the artificial oasis was the main factor for the rise of vegetation zone width and vegetation coverage in the upstream area, with the expense of sacrificing ecological environment in the downstream area.

Key words: root rot of ginseng, allelopathic effect, phenolic compounds, ginseng rhizosphere, continuous cropping obstacle