关键词: 镰孢菌, 粗毒素, 甜瓜, 连作障碍, 化感作用

Abstract: Based on field investigation and by using Levins and Pianka formula, the niches of seven bryophyte species in Hani Peatland of Changbai Mountains were studied. The results showed that the average niche breadth in nine environmental factors (total nitrogen, total phosphorous, K+ and Ca2+ in peat, pH，and electrical conductivity of surface water, tree coverage, shrub coverage, and depth to water table) of the seven species decreased in the order of Aulacomnium palustre＞Sphagnum fallax＞S. magellanicum＞S. capillifolium=Polytrichum juniperinum＞S. palustre＞S. fuscum. S. fuscum tended to be niche-specific species, while A. palustre tended to be niche-general species. Among the nine environmental factors, surface water electrical conductivity had the highest mean overlap value, while depth to water table, tree coverage, surface water pH, and shrub coverage had the lowest one, being the main environmental factors affecting the distribution of bryophytes. Most bryophyte species differentiated in their niches in the factors of depth to water table, tree coverage, surface water pH, and shrub coverage; while a few bryophyte species had higher overlap value in all of the test environmental factors due to their collaboration relationships in water use. This higher overlap value could offer indirect evidence of interspecific competition of bryophytes.

Key words: Fusarium, crude toxin, Cucumis melo, continuous cropping obstacle, allelopathic effect.