Effects of Shrub-grass on Direct Seeding of Cyclobalanopsis glauca and Malania oleifera in Rocky Desertification Mountains in Southwest Guangxi

Seed germination by direct seeding and the survival rate and growth of seedlings for two tree species, Cyclobalanopsis glauca and Malania oleifera, were monitored by field plot experiment in three site types (bare, grass and shrub lands) in rocky desertification mountains of southwest Guangxi.The litter reserves and microclimate in summer were also surveyed in the three sites.Results showed that the litter reserves in shrub and grass land were (182.55 ± 47.94) g/m² and (99.88 ± 35.76) g/m², respectively.Compared with bare land, grass and shrub land obviously reduced light intensity and air temperature and increased relative air humidity in a range of 150 cm from the ground, with the effects becoming more obvious nearer to the ground.In addition, grass and shrub land also markedly decreased soil temperature underground to a depth of 5 cm.The seed germination, seedling survival rate and height increment of C.glauca did not significantly vary among the three sites (P> 0.05).However, for M.oleifera, seed germination was obviously different between bare land and shrub land (P= 0.014), height increment of seedling was obviously different between bare land and shrub land and between grass land and shrub land (P= 0.011 and P= 0.041, respectively), and seedling basal diameter growth was significantly different between bare land and shrub land (P= 0.043) and between grass land and shrub land (P= 0.003).Our results preliminarily indicated that seed germination was higher and seedlings grew faster for M.oleifera under shrub and grass conditions, and should be considered for afforestation in rocky desertification mountains in Southwest Guangxi.Due to the very high mortality rate of annual C.glauca seedlings over winter, seedling treatment and care should be improved or other afforestation methods taken to achieve the desired results.