Effects of soil hardness on the growth of seeded and planted Pinus densiflora Sieb. et Zucc.seedlings were investigated. Soil hardness was managed for 5 levels (10, 15, 20, 25 and 30 mm of soil hardness index for Yamanaka Type), and P. densiflora was planted and seeded in each treatment. The root length,the state of root system, stem height, stem basal diameter, biomass of above- and below-ground were investigated. The planted seedling had thinner and shorter roots and the number of roots was more than that of the seeded plant. The main root of the planted plant disappeared in each soil hardness treatment, but the seeded plant remained the main root in every treatment. The ratio of root length to stem height in the seeded plant increased with the soil hardness increasing (2.1, 3.3 and 5.8 when soil hardness was 10 mm, 25 mm and 30mm, respectively). On the other hand, the ratio of root length to stem height in the planted plant decreased when soil hardness became harder (4.0, 2.5 and 2.4 when soil hardness was 10 mm, 25 mm and 30 mm,respectively). This means that the root of the seeded plant grow more preferentially than the growth of stem under hard soil conditions. When the plant was planted in the soil harder than 25mm, seedlings could not extend their roots beyond the planting holes and the root system became twisted. These differences between seeded and planted seedlings will effect plant growth, stability of trees, soil conservation ability and the tolerance to the consequence of variation of climate such as dryness. Thus, when we restore forest in degraded lands, soil modifying and the choice of restoring strategy of seeding will be important and necessary to facilitate forest succession and develop balanced forest population.%以赤松为实验材料,研究土壤硬度对播种苗和栽植苗根系发育的差异性.土壤硬度被设计为5个等级(用山中式土壤硬度计测定分别为10,15,20,25和30mm).分别调查播种苗与栽植苗根长、根系形态、苗高以及地上部和地下部生物量.结果表明:与播种苗相比,栽植苗形成细、短的根系,但根系数量较多;所有处理的栽植苗的主根丧失,而播种苗的主根则相对较为完整;播种苗的根径比随着土壤硬度的增加而增加(土壤硬度为10,25和30mm时的根径比分别为2.1,3.3和5.8),而栽植苗的根径比则随着土壤硬度的增加而减小(土壤硬度为10,25和30mm时的根径比分别为4.0,2.5和2.4).这就意味着在紧实的土壤条件下,播种苗的根系生长要优先于地上部的生长;当土壤硬度大于25mm时,栽植苗的根系很难穿透植树穴,从而使根系发生缠绕.播种苗与栽植苗根系发育的这些差异,将会影响到树木的生长量、稳定性、水土保持能力以及对气候变化如干旱等的适应能力.因此,当恢复退化土地的植被时,进行土壤改良并采用播种恢复技术,将是成功恢复植被、形成稳定的森林群落的重要和必要的积极措施.
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