Intraspecific and interspecific competition of Quercus liaotungensis in Malan forest region of Loess Plateau

The intraspecific and interspecific competition intensity of Quercus liaotungensis in Malan forest region of Loess Plateau were quantitatively analyzed using Hegyi's single tree competition index model.The results showed:(1) The intensity of the intraspecific competition in Q.liaotungensis population and interspecific competition of all associated species were approximately equal.They both decreased gradually with the increase of Diameter Breast Height(DBH) of objective tree and obeyed power function rule with DBH.Such competition mostly happened when the DBH of Q.liaotungensis was less than 15 centimeters;(2) The influence degree(competition intensity) of every species was descending as Q.liaotungensis,Pinus tabulaeformis,Betula platyphylla,Populus davidiana,Pyrus betulaefolia,Crataegus hupehensis,Acer ginnala,Carpinus shensiensis and A.grosseri;(3) P.tabulaeformis,the subdominant species in this region,given the maximal competition pressure to Q.liaotungensis in interspecific relationship.There was a possibility that this forest would become a mixed forest that Pinus tabulaeformis at the dominant status;(4) Intraspecific and interspecific competition was the main reason to make the death of Q.liaotungensis with DBH less than 15 centimeters.Felling would be the reason for the death of Q.liaotungensis when its DBH exceeded 15 centimeters.We suggested that P.tabulaeformis should be at a proper density in mixed forest,especially when it mixed with an immature Q.liaotungensis population that has many young trees.To nurture the mixed forest at a proper density and make it stable as soon as possible,P.tabulaeformis that superabundant and Q.liaotungensis that are ill growing should be picked to cut down.