| Quercus variabilis is an important deciduous native tree species with straight,dominant taproots,and its taproot penetrates deep soil layers to access moisture and nutrient,explaining why Quercus variabilis has an advantage in dry,disturbed site and is widely distributed in China.In addition,it is one of the main afforestation tree species in north China,with well ecological function and economic value.However,root deformation is common challenge in container seedlings for its vigorous taproot,especially in soft-walled polybags,and can adversely affect seedling quality and field performance.In this study we examined how radicle pruning,container type affected root characteristic,growth,nutrient storage and field performance to found out themechanisms of cultivate techniques on Quercus variabilis seedling quality and early field performance,and chose the best radicle pruning time and intensity treatment and the most suitable container type for Quercus variabilis container seedlings,then provide an insight for container seedling cultivation of vigorous-rooted tree species.The main result showed that:(1)Radicle pruning time and intensity significantly interacted root characteristic,growth,nutrient storage and field performance,indicating the necessity of combining the two approaches.For the main effects,Late radicle pruning(T3)had adverse effect on seedling quality and field performance;2/3 radicle pruning increased the number of taproots but decreased root deformation,seedling height and RCD of 2/3 radicle pruning were increased at nursery stage,and stem dry mass and stein K content were also increased at the end of the first outplanting season.1/3 radicle pruning increased root dry mass,root N and K content.Overall the combination of early and severe radicle pruning(2/3T1)has the best potential to cultivate Quercus variabilis seedlings in polybags.Compared with CK,seedling height,stem dry mass and stem N and K content of 2/3T1 treatment were increased 56.0%.28.6%,19.9%and 26.8%,respectively at nursery stage.Seedling height,root and stem dry mass of 2/3T1 treatment were increased 33.6%,116.0%and 184.7%at the end of the first outplanting season,and seedling nutrient content of 2/3T1 treatment were over 2 times higher than CK.Thus the combination of early and severe radicle pruning(2/3T1)can increase Quercus variabilis seedling quality and field performance greatly.(2)D60 containers promoted seedling quality and field performance.Compared with other four treatments,root dry mass of seedlings in D60 containers was increased over 32%at nursery stage.Root dry mass and root N content of seedlings in D60 containers were increased over 37.8%and 55.9%at the end of the second outplanting season.D40 container increased the growth of lateral roots,the proportion of lateral root surface area and volume to total root surface area and volume were highest.Seedling quality and field performance of seedlings in D40 containers were only worse than seedlings in D60 containers.Jiffy containers promoted biomass and nutrient content assigned to aboveground part.The proportion of seedling stem dry mass to the total biomass in Jiffy containers accounting for 35.5%,and the proportion of stem N,P and K content to total N,P and K content were 29.2%?32.1%and 27.4%,respectively.However,there was no significant difference between seedlings performance in Jiffy and D60 containers except N content at the end of the second outplanting season.Based on seedling quality and two years field performance,D60 container has the best potential to cultivate Quercus variabilis seedlings,but it had cost consumption.D40 container increased root growth,and Jiffy container increased the growth of aboveground part,the performance of nursery and field were the middle level.Slit and An containers with high water consumption in containerized seedling production,and had adverse effect on seedling growth,so Slit and An containers failed to cultivate Quercus variabilis seedlings.Considering the costs of container and transportation,Jiffy and D40 container can be prior to consideration for container seedling production of Quercus variabilis seedlings.(3)Container type and radicle pruning signif icantly interacted root characteristic and nutrient storage,indicating the necessity of combining the two approaches.Compared with Slit container,D40 container increased root and aboveground growth.Increased seedling growth was observed in D40 container at the end of the first outplanting season.However,the advantage disappeared at the end of the second outplanting season.Radicle pruning in D40 and Slit container decreased the growth of coarse root and had adverse effect on seedling height,RCD and root dry mass.Decreased height and RCD were observed in radicle pruning treatments at the end of the first outplanting season.However,radicle pruning treatment decreased survival while improved root growth and nutrient uptake at the end of the second outplanting season.Based on seedling quality and two years field performance,along with produce real,the optimum combination of D40 container and non-radicle pruning was recommended for container seedling production of Quercus variabilis seedlings.In conclusion,radicle pruning increased the number of taproots,optimized root architecture,and decreased root deformation of seedlings grow in ploybags.The combination of early and severe radicle pruning(2/3T1)can increase Quercus variabilis seedling quality and field performance greatly.Slender hard-plastic containers(D60?D40)and non-woven bags could eliminate root deformation and were the best represented in the root characteristic,seedling growth,nutrient status and field performance. |
PDF Full Text Request