Comparison of Plants Diversity Undergrowth in Different Forests in Semi-humid Rolling Loess Region of Northern Shaanxi

According to the study on the diversity of undergrowth plants in planted and natural forests in semi-humid rolling loess region of northern Shaanxi,life form spectrum of undergrowth in most forests do dominated by phanerophytes except for the forests of Populus.simonii in which therophtes were dominant species instead.The order of the coverage of undergrowth in forests was Robinia pseudoacacia(100.71%)R.pseudoacacia+Pinus tabulaeformis(70.95%)Larix principis-rupprechtii(53.57%)Platycladus orientalis(45.02%)Platycladus orientalis+Quercus liaotungensis,Pinus tabulaeformis+Q.liaotungensis(30.80%～32.60%)Pinus tabulaeformis,Betula platyphylla,Populus simonii,Q.liaotungensis(16.27%～22.35%)grassland(11.58%)Pinus armandii,Pinus armandii+Q.liaotungensis(1.00%～1.34%).The dominant shrubs species undergrowth altered with forest types and popular with Rosa hugonis,Acer ginnala and Sophora davidii.Meanwhile,herbs species undergrowth dominated absolutely by Carex rigescens and companied by Agropyron cristatum,Lespedeza formosa,Anemone vitifolia and Artemisia.The order of indicess of plant diversity was L.principis-rupprechtii(8.37)Pinus tabulaeformis + Q.liaotungensis,Pinus orientalis,B.platyphylla,Pinus tabulaeformis(6.09～6.43)Pinus orientalis + Q.liaotungensis(5.55)Pinus armandii + Q.liaotungensis,Populus simonii(4.58～4.73)Pinus armandii,R.pseudoacacia + Pinus tabulaeformis(3.28～3.39)R.pseudoacacia,Q.liaotungensis(2.60～2.76).In additon,except for forests of Populus simonii,the plant diversities of shrubs-layers were more than herbs-layers.The difference of coverage and diversity of under-trees layers between different forests reflects double influences of community environment and forest soil on plant amount and species composition,which can be taken as indicator of different environments of forest communities and soil properties and basis of forestland management.