| Spatial pattern analysis is an important method for studying population characteristics,interspecies relationships,as well as the relationships between population and environment.In this study,three types of Cunninghamia lanceolate mixed forest with similar site conditions in the Experimental Center of Tropical Forestry,Chinese Academy Of Forestry,Pingxiang,Guangxi,China have been selected as research objects.The three plantations are the mixed stand of C.lanceolate-M.macclurei and C.lanceolate-M.laosensis,the stand of C.lanceolate.The species composition,species characteristic value,diameter structure and species diversity of different communities in different types of C.lanceolate stand were compared and analyzed.The spatial pattern and spatial correlation of main populations were analyzed at multiple scales by the O-ring functions of single variable and double variables.It provides scientific basis for the sustainable management of C.lanceolate plantation in southern China.The main research results are as follows:(1)The composition of tree species in the three communities is diverse.The tree species which DBH≥ 1 cm in C.lanceolata-M.macclurei mixed forest were 58,they belong to 24 families and 42 genera respectively;The tree species of C.lanceolata-M.laosensis mixed forest were 77,they belong to 33 families,61 genera;the tree species in pure forest of Cunninghamia lanceolata is 63 species,which belong to 30 families and 50 genera.There were dominant families in the three communities,and most of them were Lauraceae,Rubiaceae,Euphorbiaceae and Moraceae.Ficus and Alpinia were the main genera in the sample plot,and they were dominant in all genera.(2)The popultions which important value is top six in the mixed forest of C.lanceolata-M.macclurei were in order of C.lanceolate,M.macclurei,Evodia lepta,Litsea variabilis,Macaranga denticulata,Aphanamixis grandifolia.The main population composition were concentrated.The important values of C.lanceolata and M.macclurei accounted for 48.03% of the stand,the other four main populations were less than 6%.The main population in the mixed forest of C.lanceolata and M.laosensis were in order of C.lanceolata,M.laosensis,E.lepta,Saurauia tristyla,Castanopsis hystrix and Ficus lanceolata,while pure forest of C.lanceolata were consisted of C.lanceolata,W.uvariifolia,E.lepta,S.tristyla,Oreocnide obovata and Ficus lanceolata.The species composition of the two communities were similar,the important values of dominant species were 32.32% and 36.06% respectively.the other five main populations ranged from 3.28% to 7.17%.The important values of E.lepta in the three communities ranked third,and it was the main companion tree specie of C.lanceolate plantation in this area.(3)The total diameter class structure of all individuals in the three communities showed a bimodal distribution,the small trees showed inverted J-type distribution,and the medium and large trees showed normal distribution.From the analysis of the diameter structure of the main populations,the diameter distribution of C.lanceolate and M.laosensis were approximate normal distribution,mainly medium trees,with a wide range of diameter distribution.The diameter distribution of M.macclurei was complex and multi-peak,the diameter distribution range was continuous and wide.The diameter distribution of other natural succession populations was mainly inverted J-type,and the majority of them was small trees.However,a certain number of medium and large trees appeared in individual populations,which have a wide distribution range.(4)In terms of species diversity,there were some differences in species richness and diversity index among the three C.lanceolate plantation communities.From the perspective of community analysis,The rank of Margalef richness index,Simpson diversity index,Shannon-Wiener index and Pielou evenness index were mixed forest of C.lanceolate-M.laosensis > pure forest of C.lanceolate > mixed forest of C.lanceolate-M.macclurei.From different hierarchical structure analysis,the order of the four indexes in tree layer was consistent with the result of community diversity,and the order was mixed forest of C.lanceolate-M.laosensis > pure forest of C.lanceolate >mixed forest of C.lanceolate and M.macclurei.In shrub layer,except for Margalef index,Simpson index,Shannon-Wiener index and Pielou index showed that the species diversity of mixed forest was better than pure forest,and the results of Simpson index,Shannon-Wiener index and Pielou index were mixed forest of C.lanceolate-M.macclurei,mixed forest of C.lanceolate-M.laosensis and C.lanceolate pure forest.(5)The spatial distribution patterns of the main populations in different communities showed similar regularity,mainly focusing on the aggregation distribution.the E.lepta,L.variabilis,and M.denticulate in the mixed forest of Cunninghamia lanceolata and Photinia fragrans showed clumped distribution at the some areas,while A.grandifolia did not.E.lepta,S.tristyla and F.lanceolata in the mixed forest of C.lanceolata and M.laosensis showed obvious clumped distribution in the sample plot,while the C.hystrix did not show obvious spatial difference.The spatial distribution of W.uvariifolia,E.lepta,S.tristyla,O.obovata and F.lanceolata in pure forest of C.lanceolata showed obvious clumped distribution.(6)The spatial association of dominant tree species were different with other main population in every communications.In the mixed forest of C.lanceolata and M.macclurei,spatial association of C.lanceolata with E.lepta was mostly unrelated,it showed positive correlation with L.variabilis on small scale and no correlation on large scale,it showed negative correlation with M.denticulate and A.grandifolia.In the mixed forest of C.lanceolata and M.laosensis,there was no relationship between C.lanceolata with M.laosensis and C.hystrix,while spatial association of C.lanceolata with S.tristyla and F.lanceolata were mainly positive.M.laosensis showed no correlation with E.lepta,S.tristyla and C.hystrix,and on the small scale,it showed positive or no relationship between M.laosensis and F.lanceolata.In pure Chinese fir forests,there was no correlation between C.lanceolate and W.uvariifolia on the smaller scale,but existed positive correlation on the larger scale,no correlation with E.lepta and O.obovata,and negative correlation with S.tristyla and F.lanceolata.(7)In the mixed forest of C.lanceolata and M.macclurei,the correlation between E.lepta and L.variabilis and A.grandifolia was mainly unrelated or negative.The correlation between L.variabilis and M.denticulate was similar.With the increase of spatial scale,the connection with E.lepta and M.denticulate were from positive correation to unraleted and negative correltion in the end.The correlation between L.variabilis-A.grandifolia、M.denticulate-A.grandifolia were no connection mainly.In the mixed forest of C.lanceolata and M.laosensis,E.lepta was negatively correlated or not correlated with S.tristyla,F.lanceolata and C.hystrix on the small scale,and showed a positive correlation with the increase of the spatial scale.The relationship between E.lepta with C.hystrix,S.tristyla,C.hystrix were mainly unraleted,that between S.tristyla and F.lanceolata was positive correlation.In pure forest of C.lanceolate,W.uvariifolia and E.lepta was mainly positively correlated,its correlation with O.obovatawas negative,but no relationship with S.tristyla and F.lanceolata.E.lepta was negatively correlated with S.tristyla and O.obovata,but negative correlation or no relationship with F.lanceolata.The relationships between S.tristyla with O.obovata and F.lanceolata were positive.With the increase of spatial scale,the correlation of O.obovata and F.lanceolata showed a tred from positive correlation to no correlation and then negative correlation. |
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