Abstract: By using Levins and Hurlbert formulae of niche breadth and Pianka formula of niche overlap, this paper analyzed the niche characteristics of 20 trees and 26 shrub populations in natural Pinus tabulaeformis communities in Qinling Mountains. In canopy layer, P. tabulaeformis, Quercus aliena var. acutiserrata, P. armandii, and Toxicodendron vernicifluum were the dominant populations; in shrub layer, the dominant populations were Corylus heterophylla, Euonymus alatus, Lonicera japonica, and Viburnum dilatatum. The dominant populations in canopy layer had the largest niche breadth, and were the main body of the communities; while the V. dilatatum, Elaeagnus pungens, E. alatus, and C. heterophylla in shrub layer had a larger niche breadth than the other populations. In canopy layer, there was a lower niche overlap between the dominant populations, but the Populus purdomiiDendrobenthamia anguwstata, Rhus chinensisPopulus davidiana, and Populus simoniiBetula platyphylla had a higher niche overlap. In shrub layer, more dominant populations appeared niche overlap, and E. alatus-E. schensianus, Spiraea salicifoliaLonicera japonica, Cotinus coggygria var. glaucophylla-Smilax scobinicaulis, and Rhododendron lapponicum-Salix cathayana showed a larger niche overlap. The dominant populations in the communities had a larger niche breadth and a higher niche overlap with other populations, but no positive correlation was observed between the niche breadth and niche overlap.

Key words: Brassica campestris, winter rapeseed, safety wintering, division, economic benefit.