Species Difference In Response To Neighborhood Interference In Subtropical Evergreen Broad-leaved Forest

Neighborhood interference is an important factor in affecting tree growth and determining community succession.In order to prove the difference of tree species in response to neighborhood interference,we chose six tree species,the coniferous species Cunninghamia lanceolata,Pinus massoniana,deciduous broadleaved trees Alnylum fortunei,Choerospondias axilaris,evergreen broad-leaved trees Elaeocarpus duclouxii,Castanopsis carlesii as our objectives in Jiangxi Guanshan Evergreen Broad-Leaved Forest Monitoring Plot(GSP,12 hm~2).We set interference intensity as the independent variable,and tree diameter and crown structure as the dependent variables to analyze how the response of tree species differs under neighborhood interference.Leaf characteristics and nutrient distribution pattern of tree species was compared to explain the difference of tree species in response to neighborhood interference.The results are as follows:(1)Neighborhood interference to trees was quite common in GSP.,Age structure and growth state of 6 species were different under neighborhood interference.Only the age structure of E.duclouxii and C.carlesii steadily increasesd,better than that of C.lanceolata,P.massoniana,Alnylum.and C.axilaris.(2)The annual increment of basal area of the objective tree was negatively correlated with the interference intensity.With the increase of interference intensity,the increment of C.axilaris decreased sharply,followed by A.fortunei,P.massoniana,C.lanceolate,E.Duclouxii and C.carlesii.(3)Canopy structure of the six tree species varied to neighborhood interference.When under strong interference,the crowns of C.lanceolate,P.massoniana,A.fortunei,and C.axilaris became narrow with higher bole height,But the crown width of E.Duclouxii and C.carlesii increased with lower bole height.(4)There were differences on leaf characteristics among the objective trees to neighborhood interference.When under strong interference,the specific leaf area of C.lanceolata and A.fortunei decreased by 13.18%and 2.25%,while that of P.massoniana,C.axilaris,E.Duclouxii and C.carlesii increased by 113.35%,24.49%,15.98%and 7.19%,respectively.Foliage biomass of trees decreased,among which that of C.axilaris decreased most,up to51.48%,while only that of E.Duclouxii increased by 10.11%(5)Variation of nutrient content was insignificant under neighborhood interference except that of C.lanceolate.The content of total N and P decreased by 0.58 mg/g(21.58%)and 0.05 mg/g(17.10%)in tree trunk respectively.While,the content of total C decreased by 1.27 mg/g(2.52%)and the content of total N and P increased by 1.98 mg/g(12.08%)and0.17 mg/g(22.10%)respectively in leaves.Our results showed that responses of tree species under different ecotypes differs to neighborhood interference in subtropical forests.The tree species in early succession are more susceptible to neighborhood interference.The volume of crown decreases and the foliage biomass decreases.The tree growth is negatively affected.Therefore,evergreen broad-leaved trees will gradually replace coniferous and deciduous broad-leaved trees.The community will gradually vary from coniferous forest or deciduous broad-leaved forests,such as P.massoniana,C.lanceolate to evergreen broad-leaved forests.