Abstract:

With the elevation gradient as one-dimension resource states, and with the important values as the resource state descriptor of the niche, the niche breadths, niche proportional similarity and overlaps of the dominant shrub populations in a Quercus aquifoliodes shrub community in Wolong Nature Reserve were measured using Levins, Hurlbert and Schoener methods. The results showed that the Quercus aquifoliodes shrub community was predominant in the dimension resource states. The results, obtained with the two methods, were basically consistent. The niche breadths of Quercus aquifoliodes, Cotoneaster dielsianus,Salix dissa and Daphne tangutica were relatively greater. The Levins and Hurlberts niche breadths were respectively 0.594 9,0.452 4,0.551 1,0.451 6 and 0.956 0, 0.570 3, 0.783 4, 0.571 1. There was a typical negative correlation between the niche breadths and the variance coefficient of the important values of the species. The two species with broader niche breadths or the two species with narrower niche breadths had greater similarity in niche proportion. The niche proportional similarity of most species ranged from 0 to 0.7, mostly between 0.4 to 0.6, accounting for 36.37% of total species pairs. The number of species that had niche overlaps was 112 pairs, accounting for 84.85%; and 39 pairs overlapped more than 0.2, making up 29.55%. Two populations with broad niche breadth could result in greater overlap with each other, and one population with broad niche could also had greater overlap with one population with narrow niche; On the contrary, the niche overlaps between a populations with narrow niche breadth and another population with broad niche breadth were much smaller. The proportions of L_hi and L_hi whose value exceeded 0.08 were 72.74% and 65.16% respectively, those results demonstrated that the trend of resource sharing was relatively obvious and the Quercus aquifoliodes shrub community was relatively stable.

Key words: Wolong Nature Reserve, Quercus aquifoliodes, woody populations, niche breadth, proportional similarity, niche overlap