Interaction Effects between Improved Varieties and Planting Densities in Young Chinese Fir Plantations
[Objective]In order to identify the influence of different improved varieties and initial planting densities on young Chinese fir plantations(Cunninghamia lanceolata),it is necessary to investigate the ef-fects of various improved varieties and densities on the dynamic growth of young Chinese fir plantations and their interaction.[Method]In the state-owned forestry farm of Weimin,Shaowu,Fujian Province,an interactive test forest of improved varieties and initial planting densities of Chinese fir was constructed in 2012.The dynamic effects under the interaction of two improved generations of seed orchard(1st and 3rd generations)and four initial planting densities[1 667,3 333,5 000 and 6 667 trees·hm-2]were analyzed using data from 11 years of observation.[Result]The initial planting density was negatively correlated with height,DBH,crown width,and stem volume.Excelp for crown width,the negative effects of density in-creased with increasing age.The initial planting density was positively correlated with both the stand volume and the basal area,and the positive effect of density increased with increasing age.Under low and middle densities[1 667 and 3 333 trees·hm-2],the third generation improved variety performed better than the first generation in terms of tree height,DBH,stem volume,stand volume,and basal area growth dur-ing 10-11 years old.Additionally,the increase effect of low planting density on growth was more pro-nounced.It was obvious that under this density treatment,the growth advantage of the higher generation improved variety was fully utilized.However,there was no noticeable difference in crown width between the two improved varieties at this density.The difference in all stand factors between the various improved varieties decreased with increasing density,and the differences are small when at high densities[5 000 and 6 667 trees·hm-2].The relative contribution of improved varieties to tree height fluctuated greatly with the increase of age,but after 5 years old,the relative contribution of improved varieties was much lower than that of initial planting densities.At 5 years old,the relative contribution of the improved varieties to DBH and crown width reached its maximum and was much higher than that of the densities.Following that,as the stand age increased,the relative contribution of improved varieties dropped yearly until 9 years old.The relative contribution of improved varieties to stem volume,stand volume,and basal area was whole less than the densities.[Conclusion]A certain high planting density is feasible to increase the early yield of Chinese fir plantation.The range of planting density can be appropriately 3 333 trees·hm-2 when planting with the third generation improved variety,because the low and medium density conditions are more beneficial to the growth of higher generation improved varieties.And there is no statistically signific-ant difference in the yield between the 3 333 and the 5 000 and 6 667 trees·hm-2.When planting with the first generation improved variety,the yields of 5 000 and 6 667 trees·hm-2 are significantly higher than those of 1 667 and 3 333 trees·hm-2.
Chinese firimproved varietyinitial planting densityyoung forestgrowth
万方数据
维普
