| Four typical Pinus massoniana forest type(Pinus massoniana pure forest(PF),P.massoniana-Q.acutissima mixed forest(PQM),P.massoniana-L.formosana mixed forest(PLM)and P.assoniana-P.strobilacea mixed forest(PPM))were selected from the Dabie Mountains of northern subtropical region.The changes of plant leaf functional traits,soil physical and chemical properties and understory plant diversity of four forest types of Pinus massoniana under different slope aspects were analyzed,aiming to provide theoretical reference for the production management and biodiversity protection of Pinus massoniana plantation under different environmental gradients in this area.The results showed that:(1)Among the four Pinus massoniana forest types,except for PLM forest type,the specific leaf area(SLA)of all tree species in the other three forest types showed an increasing trend from sunny slope to shady slope.Except for L.formosana,the leaf dry weight(LM)and leaf tissue density(LTD)of other tree species increased gradually from sunny slope to shady slope.Except Q.acutissima and P.strobilacea,the leaf dry matter content(LDMC)of other tree species showed a decreasing trend from sunny slope to shady slope.Leaf thickness(LT)showed : sunny slope > shady slope.In the three mixed forest types,SLA and LM of Pinus massoniana were lower than those of broad-leaved tree species in the same forest type,while LDMC,LTD and LT were higher than those of broad-leaved mixed tree species in the same forest type.(2)In the three mixed forests of Pinus massoniana,except that the leaf carbon content(LCC)of P.strobilacea in sunny slope was higher than that of Pinus massoniana,the LCC of Pinus massoniana in other mixed forests was higher than that of broad-leaved tree species in the same forest type.Except for the PLM forest type,the leaf nitrogen content(LNC)of the other two mixed forests was higher than that of Pinus massoniana under the same forest type.The leaf carbon-nitrogen ratio(C/N)of Pinus massoniana in the three mixed forests was higher than that of broad-leaved tree species in the same forest type.The average C/N of all tree species in the four forest types in this study was 24.6,which was higher than that of global forests(22.5).The leaf nitrogen-phosphorus ratio(N/P)of all tree species was less than 14,indicating that the growth of plants in this area was easily restricted by nitrogen.In the leaf nutrient characteristics and leaf stoichiometric ratio involved in this study,except for Pinus massoniana in PLM forest type and Q.acutissima,the leaf potassium content(LKC)of leaves of other forest types showed : shady slope >sunny slope.(3)The soil total nitrogen(TN),soil total phosphorus(TP),p H and soil organic matter(SOM)of four Pinus massoniana forest types were as follows : sunny slope > shady slope,and soil water content(SWC)showed a gradual increase trend from sunny slope to shady slope.Among the four P.massoniana forests,The contents of TN,TP and SOM in PQM forest were the highest in both slope aspects.,while the SWC of the PPM forest type was higher than that of other forest types on the sunny and shady slopes.In addition,the contents of TN,TP and SOM in the three P.massoniana mixed forests were higher than those in the PF forest type.The soil nutrient content(TN,TP,SOM)of PQM and PPM forest types on shady slope was higher than that of PF forest type.(4)On the sunny slope,the plant species of PLM forest type were the most abundant among the four Pinus massoniana forest types.while PF forest type was the least.On the shady slope,the plant species composition of PPM forest type is the most abundant,and the plant species composition of PF forest type is the most poor.The order of the number of understory plant species in the four Pinus massoniana forest types is : PPM > PQM >PLM > PF.In the understory herb layer,Carex ligata,Lophatherum gracile,Dryopteris fuscipes,Miscanthus sinensis and Imperata cylindrica were the species with the highest importance value and high frequency in the sunny slope.The shady slope is Eupatorium japonicum,Carex ligata,Lophatherum gracile,Dryopteris fuscipes.In the understory shrub layer,the species with high frequency on the sunny slope were Pinus massoniana,Quercus acutissima,Pistacia chinensis,Dalbergia hupehensis and Diospyros kaki.The high frequency of occurrence on the shady slope is : Pinus massoniana,Liquidambar formosana,Rubus corchorifolius,and Mallotus apelta.Among the four Pinus massoniana forest types in this study,the species diversity of PQM forest type was the highest,and the species diversity of the three mixed forests was higher than that of Pinus massoniana pure forest.The species diversity of shrub layer plants on the sunny slope is better than that on the shady slope,while the species diversity of herbaceous layer plants on the shady slope is higher than that on the sunny slope. |
