Research On The Technology Of Artificial Promotion Of The Natural Regeneration For Pinus Tabulaeformis In Western Liaoning

Pinus tabulaeformis plantation is the main part of forests in western Liaoning Province,accounting for about 50%of the forest area.However,due to the limited forest management methods,economic and technical conditions,most of Pinus tabulaeformis plantation management levels are not satisfactory and stays in the level of passive maintenance and protection.Most of Pinus tabulaeformis plantations in western Liaoning were planted in the60s-80s of the last century and of which the majority are near-mature forests or mature forests.The tree vigor begins to weaken and the renewal problem needs to be solved urgently.This study mainly adopts the combined methods of“fixed test sites observation”and“temporary standard plots research”to systematically study the technology and model of artificial promotion of the natural regeneration of Pinus tabulaeformis in western Liaoning province.The results are as follows:The results of artificial promotion techniques of natural regeneration show that thinning has important influence on the natural regeneration of Pinus tabulaeformis and different thinning levels has different effect on the natural regeneration process.According to the natural regeneration effect,the thinning intensity is divided into four grades as such:A.more than 1500 plants/hm~2;B.1200 to 1500 plants/hm~2;C.450 to 1200 plants/hm~2;D.75 to450 plants/h hm~2.It provides a scientific basis for the shelter-wood cutting natural regeneration process.For the condition of shady slope and semi-shade slope,the width of the cutting strip should be around 8 to 12 m in the case of no younger trees.With reasonable amount of younger trees,the natural regeneration of Pinus tabulaeformis in the 30 m-wide cutting strip is in good condition.The broad leaf tree plantation in the pure Pinus tabulaeformis cutting strip can be used to induce mixed forests of different ages and the width of the cutting strip should be around 10-30 m.Tree species that are suitable for planting in the cutting strip include Robinia pseudo-acacia,Prunus sibirica,Prunus dabian,Cotinus coggygria,Acer truncatum,Amorpha fruticosa,Hippophae rhamnoides,etc.The soil preparation can significantly improve the natural regeneration quality of Pinus tabulaeformis,and the soil preparation must be carried out in conjunction with a good seed harvest year;Herbal shrubs sometimes have an important impact on the quality of natural regeneration of Pinus tabulaeformis.For grassland with dense shrubs,cutting and weeding are important measures to ensure natural regeneration of Pinus tabulaeformis.Naturally regenerated Pinus tabulaeformis younger trees and seedlings are usually in the aggregated and clustered distribution,so the transplant and replanting(reseeding)is very necessary.Closing hillsides to facilitate afforestation is one of the guaranteed methods for the successful natural regeneration of Pinus tabulaeformis and the period of closure is generally 5 to 10 years.Through the study of artificial promotion technology of natural regeneration for Pinus tabulaeformis,this thesis has put forward 8 models of artificial promotion of natural regeneration for Pinus tabulaeformis in the semi-arid regions of western Liaoning as well as their applicable conditions and technical key points.These models included artificial promoting natural regeneration in open forest land,glade and forest edge of Pinus tabulaeformis;strip cutting of Pinus tabulaeformis for natural regeneration;strip cutting of Pinus tabulaeformis with broad-leaved trees plantation for artificial and natural mixed regeneration;shelter-wood cutting of Pinus tabulaeformis for natural regeneration;selective cutting of Pinus tabulaeformis for natural regeneration;clear cutting but the parent trees of Pinus tabulaeformis for natural regeneration;planting the parent trees of Pinus tabulaeformis on barren hills for natural regeneration;and planting Pinus tabulaeformis in erosion gully for natural regeneration.This study provided a certain theoretical basis and technical support for the scientific management of Pinus tabulaeformis forest in western Liaoning Province.