Wannan Hilly Region Torch Pine Sub-structure Control Technology Research

The regulation and control of stand structure is the core of management of the forest ecological system , diretly related to the stability of the ecological system of planted forest, the full play of the biological and ecological characteristics ,the restoration of under vegetation ,the rate of nutrient cycling ,the preservation of land capability of woodland and the output and quality of stand living beings .Therefore ,the regulation and control of stand structure is the key technological measure of continuing forest culture in management of planted torch pines (Pinus taeda L).Our study is to involve the comprehensive measures taken on the density of initial planting ,the quantity of living beings ,disengagement intermediate cuttings ,the selection and disposition of accompanying tree species in the regulation and control of stand structure of torch pines .A systematic study is made on the structural technology of regulation and control through the entire process of afforestation to the final felling .The main findings are as follows :Rational density of initial planting is the basis of regulation and control and timely intermediate cuttings are the key to them .The rational density of afforestation ranges from 1333 to 1667 plants per ha…At the middle--level management with a presevation of 90% of afforestation ,it takes 7 to 8 years for the stand to close when branches need to be pruned for the first time .Within 10 to 12 years the diameter of the tree can reach 13 to 14 cm at the height of 1:3 m . The free can grow as high as 6 to 7 m and the storage ranges from 60 to 80 m~3 per ha .. Abour 30% of the plants should be cut intermediately with about 1000 to 1100 plants per ha , left behind untouched , obtaining 12 to 16 m of storage in the intermediate cutting . For trees producing pulp ,the final felling is done after 16 to 18 years of growth whose diameter at the height of 1.3 m can reach 18to 20 m whose height 8 to 10 m and whose storage 150 to 170 m~3 . For raising wood of medium and big diameter , the second intermediate cutting is needed of another 30% of plants and the final felling is done in 22 to 25 years' time .The quantity of living beings of 11—year—growth torch pines growing in different density ranges from 100 to 145 t/ha ,the net productivity from 15.59 to 22.98 t/ha . The stand of big density has a larger quantity of living beings and net productivity . The stand of big density for the wood of big and medium diameter has a lower proportion of the quantity of living beings suitable for raising wood of small diameter and for producing pulp . The proportion of big and medium diameter of wood in the stand of big density is 98% of the totad quantity of living beings suitable for raising wood of big and medium diameter . The 11—year—growth torch pines have a higher net productivity being in their best growth period . However , China firs of the same year growth in this area have a lower net productivity being in their decreasing growth period . Therefore , in Qiu Gang Disfrict ,North Anhui , torch pines have a promising developing future . Torch pines have deep roots . The root quantity of living beings of 11—year—growth torch pines is about 26.4 t/ha , of which the root pile making up 44% , the thick root 43% and the thin one 13% . The root quantity in the soil above 40 cm makes up 80% , above 80 cm makes up 95% . Intermediate cuttings help to improve the nature of wood , the equality of wood texture and the ratio of utilization to some extent. Rational and timely regulation and control can greatly enhance the proportion of medium and big diameter of wood and the rate of producing wood and maintain a higher productivity of woodland .The accompanying tree species are chosen on the basis of their suitability , ecological economy and the multy—purpose of woodland such as schima superba ,Liriodendron Chinese , sassafras , south wild jujube , Quercus acutissima , golden larch , Zhong Shan cypress ets to establish industrial planted forest in Qiu Gang District , Anhui province . The disposition of accompanying tree species is advisable not in the form of the mixture of plant spacing and row spacing but of the mixture of strips and small patches under strict management and on the principle of applying different approaches to different land and different trees . When preparing the land for planting, we should preserve a certain proportion of primary zone of vegetation on the top , slops and foot of hills and some other important spots . The proportion of the tatal accompanying tree species is advisable at about 20% in terms of area . Pratection should be given to natural bushes and herbaceous vegetation in the planted forest on condition that they don't hinder the planted forest fromgrowing.