Analysis Of The Effects Of Stem-cutting Dwarfing And Phosphorus Fertilizer Application On Female Strobilus Of Pinus Massoniana Clones

Masson pine(Pinus massoniana)has strong adaptability,excellent quality,fast growth rate and high economic value,it is the main timber tree species and resin harvesting tree species in the south of China.Seed orchard is the main way to obtain improved varieties of forest trees,but the problems such as extensive management of seed orchards,great differences in fruiting ability among clones,low yield of improved varieties and obvious shortage of years are the important factors restricting the afforestation of improved varieties in China.Therefore,this study took the clones of Masson pine with different fruiting ability as the research object to carry out the effects of truncated dwarfing and phosphorus fertilizer on cone yield and female strobilus of Masson pine,and their changes on branch growth and needle nitrogen and phosphorus nutrition.To provide a theoretical basis for improving the yield and intensive management of Masson pine seed orchard.The main results are as follows:(1)Truncated dwarfing can promote the downward movement of the seed-bearing layer of the tree.Truncation at the height of 4 m could increase cone yields,which was higher than CK29.89%in 2018,higher than CK65.63%in 2019,and truncation at the height of 2 m,the cone yield in 2018 was higher than CK10.92%,higher than CK37.50%in 2019.the female strobilus increased by 38.05%and 42.28%in 2018 and 2019,respectively.The female strobilus of high-yield and middle-yield clones increased by more than 30%after dwarfing.From 2017～2019,the female strobilus of high-yield clones was 320.01%,260.81%and 184.89%higher than that of low-yield clones,respectively.(2)The branch length and diameter of new shoots increased by year after truncated dwarfing,and increased with the increase of dwarfing intensity.From 2017～2019,truncation at the height of 2m,the branch length increased by 11.71%,12.69%and 4.34%,respectively,and the branch diameter increased by 6.18%,9.34%and 4.51%,respectively.(3)Compared with non-feitilization,the application of 800 g/plant and 1600 g/plant phosphate fertilizer could significantly increase cone yield and female strobilus,cone yields increased by 82.31%and 74.90%in 2018,46.77%and 50.88%in 2019,respectively.Female strobilus increased by 67.71%and 61.45%in 2018,20.94%and 14.45%in 2019,respectively.(4)There are differences in the response of N and P contents in needles to phosphate fertilizer among different fruiting clones.During flower primordium formation,the clones with weak fruiting ability had high N contents,the N/P was 11.5～12.5,and the clones with strong fruiting ability had high P contents,the N/P was 9.5～10.5.There were differences in P contents and N/P of needles in different height,the P contents and N/P in upper part were significantly higher than those in middle and lower parts,while N/P was significantly lower than that in middle and lower parts.The number of female strobilus in clones was significantly negatively correlated with needle N contents and N/P,and positively correlated with P contents.