Cunninghamia lanceolata is one of the fastest growing major tree species in south China, and Iron-heart Cunninghamia lanceolata is a new cultivar with high heart-wood ratio and special characteristics of anti-corruption, but its wild population distribution range is narrow. The study of the population structure and dynamic characteristics of Iron-heart C. lanceolata can provide a theoretical basis for the restoration of Iron-heart C. lanceolata population and breeding of germplasm resources.

In this study, the hemaceria natural forest in Xiaoxi Township, Hunan Xiaoxi National Nature Reserve was selected as the research object. By conducting field investigations and replacing age groups with chest diameter, an age structure map was created; The survival, death and disappearance rate curves were made with the static life table; The survival function estimated value was used to make the survival function curve; The population dynamic change index was calculated; Predicted the population quantity time series.

1) The age class structure of the population belonged to the irregular pyramid type, the population had a certain renewal ability, the reserves of theⅠage class were abundant, but the mortality in the young stage was high, and the survival curve of the population trended to Deevey-Ⅲ type; 2) The mortality and disappearance rate curves of the Iron-heart C. lanceolata population were consistent throughout the entire age class, with a maximum value appearing at the XIII age class, followed by the I age class. Therefore, the renewal and structure of the Iron-heart C. lanceolata population are limited by spatial resources; 3) After survival analysis, it was found that the survival ability of Iron-heart C. lanceolata was relatively poor, with a severe decline in the early stage, stability in the middle stage, and decline in the later stage; 4) Time series analysis showed that the whole Iron-heart C. lanceolata population concentrates to the middle and old age. The lack of low age will lead to population decline.

We should quickly determine the ecological status of Iron-heart C. lanceolata and adopt on-site protection to ensure population renewal; At the same time, it is recommended to protect the germplasm resources of Iron-heart C. lanceolata through tissue culture and introduction cultivation, and expand its distribution range.

To reveal the leaf phenotypic diversity and its variation pattern in the natural Cunninghamia securinega population at different altitude gradients, to study the correlation between leaf phenotypic traits and altitude climate, and to provide scientific basis for the collection, conservation and utilization of the C. securinega germplasm resources.

Twelve leaf phenotypic traits from four natural C. securinega populations at different altitudes were investigated in Xiangxi National Nature Reserve, Hunan province by using nested ANOVA, correlation analysis, principal component analysis and cluster analysis.

Except for leaf width, 11 leaf phenotypic traits were significantly (P < 0.05) or highly significantly (P < 0.01) different between and within populations, with rich variation; The overall variation in leaf phenotypes among natural populations showed a decreasing trend with increasing altitude, and the populations with the highest and lowest coefficients of variation were Pop1 (18.52%) and Pop4 (13.95%), respectively; The intra-population phenotypic differentiation coefficient (77.46%) was greater than the inter-population phenotypic differentiation coefficient (22.54%), indicating that intra-population variation was the main source of variation, and the degree of population differentiation was at a low to medium level. The correlation analysis showed that needle thickness, specific leaf area, and specific leaf mass showed highly significantly negative correlations with temperature (P < 0.001) and positive correlations with precipitation (P < 0.001) as elevation increased, which suggested that the needles of hemlock exhibit stress tolerance strategies in order to adapt to the environment. Using the Ward.D2 hierarchical clustering method to analyze the clustering of the C. securinega populations, the four natural populations of the C. securinega at different elevations could be divided into four taxa.

The overall leaf phenotypic diversity of the C. securinega population showed a decreasing trend with increasing altitude and was significantly correlated with the altitude-climate factors. The phenotypic variation between and within populations was rich, but intra-population variation was dominant.