关键词: 密云库区, 密云库区, 生态经济评估, 旅游循环农业

Abstract:

The seasonal dynamics of weed community in 16 large-scale vegetable plots of 4 cities and districts in Guangzhou region were surveyed by using inverted “W” sampling method to study weed community composition and niches of leaf-vegetable plots of south subtropics region in four seasons. The weed community was mainly consisted of Polygonum plebeium + Portulaca oleracea + Echinochloa colonum in spring, Portulaca oleracea + Cyperus iria + Amaranthus lividus in summer, Portulaca oleracea + Polygonum lapathifolium + Amaranthus lividus in autumn, and Polygonum plebeium + Cardamine hirsute + Polygonum lapathifolium in winter. The analysis of weed niches in different seasons based on improved Levins niche breadth index and Pianka niche overlap index showed that most weeds had a niche breadth of ＞0.50, and the weeds having a total niche breadth of >1.00 included Portulaca oleracea (1.22), Polygonum plebeium (1.15), Polygonum lapathifolium (1.08). For the dominant weeds, their niche overlap indices > 0.50 were appeared most in spring and least in autumn，and the 3 maximum groups were between Digitaria sanguinalis and Eleusine indica (0.87) in spring, Portulaca oleracea and Amaranthus lividus (0.82), Portulaca oleracea and Eleusine indica (0.80).