Quantity characteristics of plant community under tree-layers of planted forests in semi-arid windy area of north Shaanxi Province

【Objective】 As plant community under tree-layer of forest is visual display of soil dynamics and affects the stability,sustainable development and functions of the ecosystem,study on the quantity characteristics of plant community under tree-layer of forest has great significance for the management practice of forests.【Methods】 Method of Standard plot×Sample plot is taken to investigate the plants community and its diversity under tree-layers of planted forests in semi-arid windy area of north Shaanxi province(Jingbian county).【Result】(1) Geophytes and therophytes are the major types(34%-88% of total species) in the life form spectrum of plants under tree-layers in planted forests.(2) The order of total plants coverage under tree-layers in planted forests is Salix matsudana(26.18%)Populus simonii×Pinus tabulaeformis,Robinia pseudoacia(8.76%-11.77%)Populus simonii and Populus simonii×Caragana microphylla(2.77%-3.16%)Pinus tabulaeformis,Hippophae rhamnoides,Pinus tabulaeformis×Caragana microphylla,Caragana microphylla and natural grassland(CK)(1.06%-1.57%)Populus simonii×Hippophae rhamnoides and Amorpha fruticosa(0.72%-0.77%).(3) The dominant species under tree-layers are similar to planted forest types,in which,shrubs dominate with Artemisia desertorum and Hippophae rhamnoides while herbs dominate with Pennisetum alopecuroides,Carex rigescens,Agriophyllum squarrosum and Agropyron cristatum.(4) The order of indexes sum of plant diversity under tree-layers of forests is Salix matsudana,Robinia pseudoacia,Populus simonii(6.00-7.18)Populus simonii×Caragana microphylla,Populus simonii×Pinus tabulaeformis and Pinus tabulaeformis(4.87-5.38)Hippophae rhamnoides,Pinus tabulaeformis×Caragana microphylla,Caragana microphylla and Populus simonii×Hippophae rhamnoides(4.06-4.49)Amorpha fruticosa and natural grassland(CK)(2.15-2.76).The species diversities of herbal layers in all planted forests are more than that of shrubs layers.【Conclusion】 Coverage and species diversities of plant communities under tree-layer of planted forests in semi-arid windy area of North Shaanxi Province are generally lower and richer in broad-leaved forests than in needle-leaved forests and shrubs.So,introducing broad-leaved trees into needle-leaved forest and forming mixture is an available way to increase plant diversity under tree-layer and maintain ecosystem stability and sustainable development of planted forest.