桂西南石漠化山区灌草丛对青冈和蒜头果直播造林的影响

为探讨石漠化山区立地类型对青冈(Cyclobalanopsis glauca)和蒜头果(Malania oleifera)直播造林的影响及其机理,本研究采取小区播种试验方法,并监测这2个树种在石漠化山区3种立地类型(灌丛、草丛和裸地)中种子萌发、幼苗存活与生长量情况,以及各立地类型中枯落物储量和小气候环境因子特征。结果显示,灌丛和草丛中枯落物储量分别为(182.55±47.94)g/m2和(99.88±35.76)g/m2;灌丛和草丛距离地面150cm处的光照强度和气温显著低于裸地、空气湿度显著高于裸地,且距离地面越近效果越明显;灌丛和草丛地下5cm处的土壤温度显著低于裸地;青冈种子萌发率、幼苗保存率和幼苗生长量在3种立地类型间差异不显著(P0.05);蒜头果种子萌发率在裸地和灌丛间差异显著(P=0.014),一年生幼苗株高生长量在裸地和灌丛之间、草丛和灌丛之间差异显著(P=0.011和P=0.041),幼苗基径生长量在裸地和灌丛之间差异显著(P=0.043),在草丛和灌丛之间差异极显著(P=0.003)。本实验结果表明,在桂西南石漠化山区灌、草丛的保育作用下,蒜头果种子发芽率较高,幼苗生长较快,可选择种子直播方式造林;而青冈因一年生幼苗越冬后死亡率很高,需要改进幼苗抚育措施或改变造林方式,才能取得较理想的效果。

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.