根系损伤强度对不同规格白杨物候及生长特性的影响

[Objective]This study aims to investigate the effects of different morphological sizes and root pruning intensities on the phenological changes and growth characteristics of Populus tomentosa within the same year,providing a theoretical basis and guidance for understanding the response and mitigation strategies of Populus tomentosa to root damage based on morphological differences.[Methods]A two-factor experimental design was employed,selecting large(height:308.75 cm,DBH:15.94 mm,basal diameter:28.47 mm),medium(height:238.00 cm,DBH:11.07 mm,basal diameter:24.20 mm),and small seedlings(height:138.92 cm,DBH:6.59 mm,basal diameter:14.87 mm)from one-year-old"Beilin Male No.1"Populus tomentosa planted in 20-gallon containers.In March of the following year,root pruning intensities were simulated based on the basal diameter to create low(P1-15 times basal diameter),medium(P2-7.5 times basal diameter),and high(P3-3.75 times basal diameter)damage levels,along with an undamaged control group(CK).Post-treatment,survival rate and dieback rate were observed,phenological phases of leaves and roots were periodically monitored,and tree height,DBH,and basal diameter growth were measured monthly.Logistic growth curves were fitted to determine key phenological indicators during the rapid growth period,and final growth characteristics at the end of the growing season were analyzed to assess the response of seedlings to root damage.[Results]Root damage intensity and seedling size significantly affected the phenological changes and growth characteristics of Populus tomentosa.As seedling size and root damage intensity increased,the dieback rate rose significantly,with large trees showing particularly pronounced responses to medium and high damage intensities.Increased size and root damage significantly delayed the leafing start and full leaf stages but advanced the end-of-season defoliation period.Single leaf area during the rapid growth period decreased significantly with increased root damage,and new root initiation occurred earlier in all damage treatments compared to the control.Logistic model curves showed that trees with root damage had flatter growth curves than the control group.As size increased,the maximum growth rate of the basal diameter decreased.For large and medium seedlings,increased damage intensity significantly reduced the maximum growth rates of stem height and DBH,while small seedlings showed no significant differences in growth rates.Survival rate,start and end dates of the rapid growth period,and its duration did not differ significantly across treatments.At the end of the season,as seedling size increased,tree height,DBH,basal diameter,H/RCD,and DBH/RCD all increased,while basal diameter increment decreased.Tree height and DBH increments increased with tree height in the control and low damage treatments,but decreased under medium and high damage treatments.H/DBH showed no clear pattern.With increasing damage intensity,tree height,DBH,basal diameter,their increments,H/RCD,and DBH/RCD all decreased.PCA analysis confirmed the correlations and trends among phenological and growth variables.[Conclusion]Moderate and severe root damage had adverse effects on Populus tomentosa of different sizes,reducing growth indicators and delaying leaf phenology,but advancing root initiation time.Responses to the same damage intensity varied among different-sized seedlings,with larger seedlings being more affected by root damage,whereas basal diameter increment showed the opposite trend.Therefore,it is crucial to consider the combined effects of seedling size and root pruning intensity,which is significant for understanding the mechanisms of Populus tomentosa transplantation survival in the first year.