| Keteleeria fortunei var.Cyclolepis belongs to Keteleeria.It is an ev-ergreen tree endemic to China and is the national key protected wild plant.An well-preserved Keteleeria fortunei var.cyclolepis natural community,located in Junzifeng National Nature Reserve in Mingxi county,Fujian Province,is mainly comprised of 6 old Keteleeria fortunei var.Cyclolepis,who own straight stems and beautiful crown forms,and is the locally-fa-mous Fengshui forest.This study is based on community ecology and pop-ulation dynamics,aiming to clarify the survival status and development trend of Keteleeria fortunei var.cyclolepis species in the community,so as to provide theoretical grounds for protective measures.The main results are as follows:（1）A total of 159 species of vascular plants are recorded in the Keteleeria fortunei var.Cyclolepis community,belonging to 54 families and 97 genera.There are 10 dominant families and 13 dominant genera.And 25 families and 73 genera of single species,these species account for the majority.The geographical composition of flora is dominated by pan-tropical distribution,but the warm temperate distribution also owns a cer-tain position,showing the transition from subtropical to warm temperate.Pedigree composition analysis showed that all seed plants in the commu-nity are divided into four categories,and the same category of plants had close genetic relationship.Keteleeria fortunei var.Cyclolepis,Pinus mas-soniana and Cunninghamia lanceolata are in the first group,and these spe-cies belong to gymnosperms with similar origins.（2）The community of Keteleeria fortunei var.Cyclolepis is an une-ven-aged forest composed of different age tree species.The vertical strati-fication is clear.It can be divided into seven levels,with a height between2.8 m and 38.5 m.Keteleeria fortunei var.Cyclolepis has the largest height and use light resources.There are 77 tree species in the tree layer,mainly including Keteleeria fortunei var.Cyclolepis,Cunninghamia lanceolata,Castanopsis eyrei,Pinus massoniana,Alniphyllum fortunei and Cho-erospondias axillaris.The large trees of Keteleeria fortunei var.Cyclole-pis occupy an absolute advantage,with a maximum diameter of 159.5 cm and an average diameter of 90.3 cm.The population is dominated by young and old individuals,the number of middle-aged individuals is rare,and the diameter class structure is intermittent.There were 1,846 plants（clumps）of 88 species in the shrub layer,mainly covered by Indocalamus tessellatus,with a height of 0.8 m～2.0 m and a coverage of 90%.There were only 8species and 304 plants（clusters）in herbaceous layer.There were 25 spe-cies and 381 plants（clusters）in the interlayer.A large number of Keteleeria fortunei var.Cyclolepis seedlings were distributed in the regen-eration layer.（3）The study of species diversity and community stability shows that Margalef richness index（DM）:shrub layer（11.568）>tree layer（11.387）>herb layer（1.224）.Simpson dominance index（D）:tree layer（0.947）>shrub layer（0.833）>herb layer（0.714）.Shannon-Wiener diversity in-dex（H）:tree layer（3.501）>shrub layer（3.033）>herb layer（1.429）.Pielou evenness index（E）:tree layer（0.806）>herb layer（0.687）>shrub layer（0.677）.The intersection coordinates of M.Godron stability measure are（32.15,67.85）,and the Euclidean distance is 17.18,which is relatively far from the community stability point（20,80）,indicating that the commu-nity stability is poor.（4）The study of niche and interspecific association shows that the niche breadth of Cunninghamia lanceolata in tree layer is the largest,and its B（SW）i and B（L）i were 1.67 and 5.04,respectively.The niche breadth of Keteleeria fortunei var.Cyclolepis ranks third,B（SW）i and B（L）are 1.62 and4.46,respectively.The niche breadth of Indocalamus tessellatus in shrub layer is the largest,with B（SW）i and B（L）were 1.78 and 5.87,respectively.The average value of Pianka niche overlap of tree layer and shrub layer are0.58 and 0.66,respectively,and the average value of niche similarity are0.51 and 0.56.The overall correlation of the dominant species in tree layer and shrub layer are not significantly negatively correlated.Pearson corre-lation coefficient and Spearman rank correlation coefficient test results are consistent.The number of negatively correlated species is more than that of positively correlated species,and most species pairs are not significant.Compared with the x2 test,Pearson correlation coefficient and Spearman rank correlation coefficient test are more sensitive.The dominant species in tree layer can be divided into four ecological species groups by PCA two-dimensional sorting.（5）Population structure and dynamics demonstrates that there are 334Keteleeria fortunei var.Cyclolepis in the community,and the population shows a dynamic relationship of“growth-stability-decline-growth-de-cline”,and the survival curve is Deevey-Ⅲ type.The number of Keteleeria fortunei var.Cyclolepis are insufficient,only 29,and the seed-ling mortality rate is very high.Combined with the four survival functions,the number of Keteleeria fortunei var.Cyclolepis decreases sharply in the seedling stage,and remains stable or decreases slightly in the middle and old age.In the population time series prediction,with the passage of time,the seedlings are seriously lacking,the number of young individuals is small,the renewal ability is weak,the population is mainly small and me-dium trees,and the number of elderly trees fluctuates non-significantly.In conclusion,there are regeneration obstacles in the seedlings of Keteleeria fortunei var.cyclolepis,and the population size is gradually shrinking.In order to protect the natural community of Keteleeria fortunei var.cyclolepis more effectively,it is suggested to take measures such as implementing in-situ protection measures,strengthening scientific research on seedlings,and properly carrying out ex-situ protection measures to expand the distribution range,so as to ensure the effective pro-tection and restoration of K.fortunei var.cyclolepis population,expecting to boost the breeding and growth of the population. |
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