Effects Of Decay Classes And Diameter Classes On Physico-chemical Properties And Decomposition Rate Of Pinus Koraiensis Log

Log is an important component for most of forest ecosystems.It plays crucial roles in maintaining soil fertility,sustaining biodiversity and cycling of carbon(C)and nutrient.However,physico-chemical properties and decomposition rate of logs vary with decay classes and diameter classes.Our objective was to study effects of decay classes and diameter classes on physico-chemical properties and decomposition rate of logs in a typical mixed broadleavedKorean pine forest in northern China.In this study,logs of Pinus koraiensis were chosen as it was the constructive species in the typical mixed broadleaved-Korean pine forest.Logs of P.koraiensis at each decay classes(I–V)were divided into four diameter classes,including diameter class i ≤ 10.0 cm,diameter class ii: 10.1–30.0 cm,diameter class iii: 30.1–50.0 cm,and diameter class iv > 50.0 cm.Then,we explored effects of different decay classes,diameter classes and their interactions on the physico-chemical properties and decomposition rate of logs for both the heartwood and sapwood.1)The results showed that the physico-chemical properties of heartwood and sapwood generally exhibited similar variations.Their moisture content both increased with an increasing decay class,whereas wood density both decreased with an increased decay class and diameter class.The carbon concentrations of the sapwood showed a trend of gradual increasing during decomposition,and there was an accumulation in nitrogen(N)and phosphorus(P)concentrations of the heartwood and sapwood with an increased decay class,simultaneously.Only N and P concentrations of the heartwood increased and then decreased with an increasing diameter class.The cellulose content decreased with an increasing decay class.In contrast to the cellulose,the lignin content increased with an increased decay class.However,cellulose and lignin contents exhibited no distinct trend among diameter classes.The moisture content of logs had a significant positive correlation with C,N,P concentrations and lignin content(except P concentrations of the heartwood)(P<0.05),but had a significant negative correlation with the cellulose content(P<0.05).The wood density was negatively correlated with C,N,P concentrations and the lignin content(P<0.05),but it was positively correlated with the cellulose content(P<0.05).2)With the increase of decay class,decay class I and II had low decomposition rates,and then increased significantly at decay class III,and subsequently decreased at decay class IV until decay class V.The overall performance was: decay class V > decay class III > decay class IV > decay class II > decay class I.Decomposition rate of logs increased and then decreased with an increasing diameter class.Decomposition rate of logs had a significant positive correlation with N,P concentrations(P<0.05),but had a significant negative correlation with the lignin content(P<0.05).