关键词: 长期施肥, 黄壤性稻田, 土壤性质, 杂草种子, 稗草

Abstract: Niche structure is a major foundation for protection of rare and endangered plants. In order to understand the niche structure of Loropetalum subcordatum (Benth.) Oliv., we investigated L. subcordatum communities at Maolan, Libo County, China. Importance value was used as an index of resource state, the niche structure of tree, shrub and herb layers in L. subcordatum communities were calculated using the indices of Levins breadth (B_i), Shannon breadth (B_s) and Pianka overlap. The similarity of niche breadth was analyzed by using Bray-Curtis clustering. The results showed that: (1) The niche breadth of L. subcordatumwas relatively large.The B_i and B_s values were 4.32 and 1.53 in tree layer, 3.95 and 1.49 in shrub layer, and 4.55 and 1.56 in herb layer, respectively, reflecting the strong ability of resource use of L. subcordatum.The Bray-Curtis similarity analysis showed that the niche breadth of Cornus controversa, Mallotus philippensis, Miscanthus floridulusand Murraya exotica was similar to that of L. subcordatum. (2) The value of niche overlap of L. subcordatum with the other species was 0.66-0.97, 0.55-0.99 and 0.51-0.96 in tree layer, shrub layer and herb layer, respectively. Specially, the value of niche overlap of L. subcordatumwith the deciduous species in tree layer, shrub layer and herb layer was 0.75-0.88, 0.82 and 0.51-0.80, respectively. These results indicated that L. subcordatumand deciduous species maybe have a complementary demand for resources. (3) The potential competition with evergreen species (especially in shrub layer) may be one of the most important reasons for the danger of L. subcordatum.

Key words: Echinochloa, yellow paddy field, weed seed, soil properties., long-term fertilization