Direction effects on plant diversity, earthworm diversity, and soil organic matter of natural secondary forest in dawuling mountains

Investigations were made on plant diversity, earthworm diversity, and soil organic matter in different directions of natural secondary forest in Dawuling Mountains. Four slopes,east-facing slope (EFS),south-facing slope (SFS),west-facing slope (WFS), and north-lacing slope (NFS) of Datianding Hill and Qieding Hill,were sampled. In the Dawuling Mountain, 1)the number of tree was lower on SFS that other directions, the densities of on SFS of Datianding Hill and Qieding Hill being 0 Ind·m~(-2) and 0.06 Ind·m~(-2), respectively, but there was no difference of tree diversity among directions, Shannon-Weaver index of tree ranging from 0 to 2.24, Margalef index from 0 to 3.15; 2) the number of shrub was not dominant in any directions, but SFS had the lowest shrub diversity, Shannon-Weaver index and Margalef index of SFS of Datianding Hill being 1.52 and 1.70, respectively, those of Qieding Hill being 2.05 and 2.33, respectively; 3) the number of herb on SFS was the highest among those or all directions, the densities of herb on SFS of Datianding Hill and Qieding Hill being 87 Ind·m~(-2), and 44 Ind·m~(-2),respectively, and SFS also had the highest herb diversity, Shannon-Weaver index and Margalef index of herb on SFS of Datianding Hill being 2.46 and 3.36, respectively; 4) the number of earthworm was low on SFS. the densities of earthworm on SFS of Datianding Hill and Qieding Hill being 7 Ind·m~(-2) and 0 Ind·m~(-2), respectively, but the earthworm diversities was insignificantly influenced by direction, Shannon-Weaver index of earthworm ranging from 0 to 1.63. Margalef index from 0 to 2.20; and 5) direction had no influence on the content of soil organic matter, and the soil within 50 cm from the surface had 11.2～40.6% of organic matter, that between 50 cm and 100 cm from the surface having 5.6～17.5% of organic matter. Because of direction effects on biological sources, different methods should be used to manage natural secondary forest according to slope-exposure.