The Response Of Pinus Massoniana Plantations To Gap Disturbance

Forest gap plays an important role in improving biodiversity and providing the theorotic basis for forest sustainable management.This paper studies forest gaps of Pinus massoniana plantation with the assistance of field investigation,laboratory analysis and various statistical analysis. We analyzed the soil physical and chemical properties, dynamics of gap species composition and biodiversity and the relationship between environmental gradient and species compositions among gaps of different size and age. The main results showed:(1)With the increasing of soil depth,the soil in different gaps appeared obvious accumulation in the surface layers except total K.With the increasing of gap age,the soil pH decreased because of improvement on nitrification and the soil organic matters increased due to increasing of vegetation composition.The change about soil N,P,K contents is complicated.Different size forest gaps had no singnificant effects on organic matters and N,P,K contents,but not PH.With the increasing of gap age,the soil bulk density and porosity shows opposite trend.The saturation moisture capacity and capillary moisture capacity obviously increased.(2) There were 147 species belonging to 15 families and 19 genera in this paper. Part of gaps appear trees. With the increasing of gap age,The dominant species has changed in different shrub layer. There are more species in herb layer than shrub layer The herb layer appears regeneration seedlings of dominant species in shrub layer and other herbaceous plants mainly from Poaceae and Cyeraceae.The importance value of dominant species in shrub layer and herb layer is different among different size.There are different common species and similarity coefficient in different gap developmental stage. The similarity coefficient in herb layer is better than shrub layer and become more and more higher with the development of gap age.(3) With the change trend of gap sizes and gap developmental stages, the richness index(R) in shrub and herb layer presented a single peak curve. The general trend of species diversity index(H) shows an upward tendency but riseing slowly while pielou evenness index(J) is more complicated. A significant difference was observed in richness index(R) and diversity index(H) between different gap size (P<0.05). There was significant differences between different gap age except diversity index(H) in shrub layer. The gap age had significant effect on richness index(R) in herb layer. The interaction between age and size has effect on diversity index(H) and evenness index(J) in shrub layer.(4)By using canonical correspondence analysis (CCA) studied the species structure and its relationships with environmental factors.We know that the soil bulk density,totle P,K, oil organic matters, quick-acting potassium,PH and totleN,Effective phosphorus, non-capillary porosity of soil represent axis land axis 2,which have more significant influences on vegetative distribution in this area.We test correlation. The test of significance (F) which between speices and environmental factors by using Monte Carlo showed that the P value between CCA axisl and environmental factors and for entirety test is 0.038 and 0.030 respectively.It means the axis and environmental factors significantly related and the result of CCA ordination agree well.