育苗密度对千年桐幼苗N、P利用和生物量积累的影响

以1年生千年桐幼苗为试验材料,设置5种育苗密度D1（10 cm×10 cm）、D2（15 cm×15cm）、D3（20 cm×20 cm）、D4（25c m×25 cm）、D5 （30 cm×30 cm）,研究不同育苗密度对千年桐幼苗养分吸收利用和生物量积累的影响.结果表明：不同育苗密度处理之间的千年桐幼苗,同一生长部位的N、P含量变化规律不明显,各养分含量受育苗密度影响不显著,但对N、P利用率的影响显著.随千年桐育苗密度的增大,幼苗的N、P吸收率均减小.随时间的推移,N利用率呈增加趋势,P利用率呈先增后减的趋势;在生长旺盛期,密度越小,幼苗N利用率越高;生长初期,高密度下P利用率较大,生长后期则相反.随育苗密度的增加,平均单株干质量、根干质量、叶干质量、茎干质量在9月最大;在一个生长季,地下/地上生物量表现为先减后增（均小于1）.在自然状态下D5密度最适宜千年桐幼苗的生长,结合施肥及光合作用、经济效益等其他因素考虑,也可在D5的基础上适当增加密度.

Effect of Seedling Density on Nitrogen and Phosphorus Utilization and Biomass Accumulation of Aleurites montana Seedlings

The effect of different planting densities on nutrient absorption,utilization and biomass accumulation of Aleurites montana seedlings was studied by one year old seedlings with five kinds of seedling densities as D1 （10cm × 10 cm）,D2 （15 cm × 15 cm）,D3 （20 cm × 20 cm）,D4 （25 cm × 25 cm） and D5 （30 cm × 30 cm）by single factor randomized block design.The results showed that there was no distinct rule in the content change of nitrogen （N）,phosphorus （P） in the same organ of A.montana seedlings among the treatments,and the nutrient content was not significantly affected by the densities.Whereas the utilization rate of N and P was significantly influenced by the planting densities.The N and P absorption rates were reduced as planting density increased.N utilization rate increased along with the time,while P utilization rate increased first and then decreased later.Within the vigorous growth stage,the lower density,the higher N utilization rate was.During the initial growth stage,the greater the density,the higher P utilization rate was.However,the rule in P utilization rate was opposite at the late growth stage.Besides,as planting density increased,the dry biomass weight per seedling,dry root biomass,dry leaf biomass and dry stem biomass all reached the maximum value in September.In the whole growing season,the ratio of underground biomass and aboveground biomass decreased first and then increased later,but the ratio value was always smaller than 1.There were significant differences in the growth rate among different density treatments in the late growth stage.In summary,the D5 was the best planting density for Aleurites montana＇s seedling growth under the natural conditions.Taking fertilization,photosynthesis and economic benefits into consideration,the density could be appropriately increased based on D5.