Quantity characteristics of plants community under tree-layers of forests in semi-humid gullied rolling region of Loess Plateau

【Objective】 The study on the quantities characteristics of plant community under tree-layer of forest can give scientific basis for the construction and management of forests.【Method】 Standard plot+Sample plot was taken to investigate the plants community under tree-layers of forests in semi-humid gullied rolling region of loess plateau(Yan'an).【Result】(1) Life form spectrum of plants under tree-layers in forests of Populus simonii,Betula platyphylla,Pinus tabulaeformis,Pinus tabulaeformis+Populus simonii,Pinus tabulaeformis+Betula platyphylla take phanerophytes as major type,while forests of Ulmus pumila,Robinia pseudoacia,Hippophae rhamnoides,Acer ginnala and Platycladus orientalis take therophtes instead.(2)The order of total plants coverage under tree-layers in forests is Populus simonii,Robinia pseudoacia(22.22%-22.65%)Pinus tabulaeformis+Populus simonii,Betula platyphylla,Ulmus pumila(9.78%-14.11%)Platycladus orientalis,Hippophae rhamnoides,Acer ginnala,Pinus tabulaeformis+ Betula platyphylla(3.72%-5.20%)Pinus tabulaeformis(2.38%).(3)The dominant shrub species under tree-layers alter with forest types and popular with Lonicera standishii,Elaeagnus umbellate,Periploca sepium and Sophora davidii.Meanwhile,herb species under tree-layers dominate absolutely with Carex rigescens and companied with Agropyron cristatum,Lespedeza formosa,Urena lobata and Aremisia.(4)The order of indexes sum of plant diversity under tree-layers of forests is Populus simonii(7.29)Robinia pseudoacia,Betula platyphylla,Pinus tabulaeformis(6.03-6.61)Platycladus orientalis,Pinus tabulaeformis+Populus simonii(5.72-5.90)Acer ginnala,Pinus tabulaeformis+Betula platyphylla(4.44-4.85)Ulmus pumila,Hippophae rhamnoides(3.49-3.50).【Conclusion】 Coverage and species diversities of plant communities under tree-layer of planted forests in this region are generally not high and they are relatively richer in most broad-leaved forests than those in needle-leaved forests and shrubs.So,introducing broad-leaved trees into needle-leaved forest and forming mixture is an effective way to increase plant diversity under tree-layer and maintain ecosystem stability and sustainable development of forest.