Environmental Controls of Diurnal and Seasonal Variations in the Stem Radius of Platycladus orientalis in Northern China

Chemotaxonomic Variation in Volatile Component Contents in Ancient Platycladus orientalis Leaves with Different Tree Ages in Huangdi Mausoleum

To gain insight into the differences in the composition and volatile components content in ancient Platycladus orientalis leaves with different tree ages in Huangdi Mausoleum, the volatile components were identified by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) method. The volatile components were statistically analyzed by orthogonal partial least squares discriminant analysis and hierarchical cluster analysis, and the characteristic volatile components were screened. The results exhibited that a total of 72 volatile components were isolated and identified in 19 ancient Platycladus orientalis leaves with different tree ages, and 14 common volatile components were screened. Among them, the contents of α-pinene (6.40-16.76%), sabinene (1.11-7.29%), 3-carene (1.14-15.12%), terpinolene (2.17-4.95%), caryophyllene (8.04-13.53%), α-caryophyllene (7.34-14.41%), germacrene D (5.27-12.13%), (+)-Cedrol (2.34-11.30%) and α-terpinyl acetate (1.29-25.68%) were relatively higher (>1%), accounting for 83.40-87.61% of the total volatile components. Nineteen ancient Platycladus orientalis trees were clustered into three groups through the HCA method based on the 14 common volatile components content. Combined with the results of OPLS-DA analysis, (+)-cedrol, germacrene D, α-caryophyllene, α-terpinyl acetate, caryophyllene, β-myrcene, β-elemene and epiglobulol were the differential volatile components to distinguish ancient Platycladus orientalis with different tree ages. The results revealed that the composition of the volatile components in ancient Platycladus orientalis leaves with different tree ages was different, showing different aroma characteristics, which provided a theoretical reference for the differential development and application of volatile components in ancient Platycladus orientalis leaves.

Dynamic Effects of Structure-Based Forest Management on Stand Spatial Structure in a Platycladus orientalis Plantation

Structure-based forest management (SBFM) is a method for improving forest structure and quality based on nearest-neighbor analysis. Stand spatial structure directly affects the health and stability of forest ecosystems. Research on the effects of SBFM on the distribution of spatial structure parameters is needed to provide a scientific basis for further development and implementation of SBFM technology in forestry. The present study was conducted on six permanent plots (20 m × 20 m) established within a Platycladus orientalis (L.) Franco plantation in Beijing, China. Changes in stand spatial structure parameters (SSSPs) were evaluated in managed and control plots at three time points: before SBFM and after 2 and 7 years of SBFM. The results showed that SBFM gradually accelerated the development of the P. orientalis plantation toward a random distribution pattern, reaching a significant difference within 2 years. SBFM promoted the growth of medium and dominant trees, with a significant difference between SBFM and control stands after 7 years. It led to a slight increase in mingling compared to the control, although no significant differences were observed between treatments. SBFM generally decreased the proportions of disadvantageous microstructures (disadvantaged trees with non-randomly distributed, disadvantaged trees with a low degree of mingling, and non-randomly distributed trees with a low degree of mingling). It also improved the ratio of torch (R2) units to dumbbell (R1) units, gradually improving the stability of the plantation forest. The results of this study suggest that SBFM optimized the spatial structure of a P. orientalis plantation in Beijing, China, and was conducive to tree growth and forest stand productivity.