Study On The Efficiency Of Mixed Forest With Fokienia Hodginsii And Michelia Macelurei In Productivity And Soil Nutrient

Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy are high quality timber wood that are suitable to extent in the south of china energetically.And it play important effects and positions in short-period industry raw forest,forest sustainable management,abundant forest germplasm resources and so on.We choiced artificial pure and mixed Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy forest which located in Tongan zone ,Xiamen city,Fujian province in 1982 as research object.We choiced pure and mixed Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy forest in suburban forest.Research content include diameter step distributiom in artificial pure and mixed forest,biomass distribution in forest different hierarchy,change of forest volume,soil nutrition comaparison and soil C reserves.These results provide scientific basises in guide and scientific management in south Fujian mountain land about sustainable management and basic datas to cope with future climate negotiation.The main results are as follows:(1)The diameter step distributiom of mixed Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy forest shows large and small diameter occupied low proportion,while middle diameter occupied high proportion.And distributions shows normal distribution and benefit to community balance.The large diameter of Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy in mixed forest is more 26% and 36% than two pure forests respectively.The mixed forest have thinner branch,smaller angle,better natural pruning,higher under branch,smaller and less dead knot than pure forest.It showed that while we mixed Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy forest together,we can promote forest stem form development and improve timber-produced rate.The wood quality of mixed forest is better than pure forest.(2)The diameter total growth and tree hight total growth of Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy increase with the tree age expansion. The diameter,tree hight,volume of Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy grow rapidly in 10 to 15 years,but gradually decreased after 10 to 15 years.The current annual increment and average increment of Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy are"zero"in the beginning,then the volume increased with forest age and gradually decreased after a certain age.(3)The biomass and organ distribution's size order of individual average tree about Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy is:trunk>root>branch>bark>leaf. The biomass and organ distribution's size order of tree layer about Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy is:trunk>root>bark>branch>leaf and trunk>root>branch >bark>leaf.The size order in each level biomass of pure and mixed Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy forest is: tree layer>litter layer>herb layer>shrub layer. The trunk and bark's biomass of average tree concentrate lower layer of sample trees mainly,Decr- eased with the hight of trunk.(4)The results of modle fitting show:Regard biomass as dependent variable,when we use the modle fitting which introduces the diameter,the tree hight and the volume as independent variable is superior to log regression relation,polynomaial model and others.(5)In the different density of artificial forest land, the proportion that biomass of average tree's trunk and bark occupies individual tree increases with the forest density increase;While the proportion that biomass of average tree's branch and leaf occupies individual tree decreases with the forest density increase.(6)The soil bulk density of each kinds of forest land increase with soil depth.The soil water content,maximum moisture capacity and minimum moisture capacity,capillary pore and total porosity of mixed forest are all improved than pure Fokienia hodginsii Henry et Thomas and Michelia macelurei Dandy forest.But the non-capillary pore descend than the pure forest.Through planting the forest,we modify the soil structure,loosen the soil,promote the storage capacity and ventialation.The organic matter content in surface and subsurface of mixed forest is higher than the pure forest.The organic matter content,total nitrogen content,hydrolyzable nitrogen,total phosphorus and available phosphorus of soil all decline with soil depth increased.The total potassium size order is: pure Michelia macelurei Dandy>pure Fokienia hodginsii Henry et Thomas>mixed forest. The available potassium size order is: pure Fokienia hodginsii Henry et Thoma >pure Michelia macelurei Dandy>mixed forest.(7)The average content of SOC in 0-80 centimeter of mixed forest,pure Fokienia hodginsii Henry et Thoma and pure Michelia macelurei Dandy are 21.83 g·kg-1,20.90 g·kg-1 and 20.12 g·kg-1 respectively. The SOC of soil surface increase significantly after afforestation.The soil enrichment coefficient is more than one in 0-20 centimeter soil depth and less than one in 20-80 centimeter. The soil enrichment coefficient is biggest in 0-10 centimeter and the enrichment effect is most significantly.The C reserves of mixed forest,pure Fokienia hodginsii Henry et Thoma and pure Michelia macelurei Dandy in 0-80 centimeter are: 173.58t·hm-2,188.46 t·hm-2 and 178.53t·hm-2.The C of forest land's soil shows increasing trend and become a important C influx.