9Jurgensen M F,Harvey AE, Graham RT. Impact of timber havesting on soil organic matter, nitrogen ,productivity and health of Inland Northwest Forests[J]. Forest Science, 1997,43(2):234-250.
10Aughstol, Bonnaud P, Ranger J. Impacf of tree species on Forest Soil acidification[J]. Forest Ecology and mancgement, 1998, 105:67 - 78.