[Altitudinal variation pattern in Daphniphyllum macropodum leaf traits and influencing environmental factors in Mao'er Mountain, China]. / çŒ«å„¿å±±äº¤è®©æœ¨å¶æ€§çŠ¶æµ·æ‹”å˜å¼‚æ ¼å±€åŠå ¶çŽ¯å¢ƒå½±å“å› å­.

Analyzing the pattern of altitudinal variation in the leaf traits and their networks of a particular tree species of similar age and its influencing factors could contribute to understanding the impacts of environmental factors on leaf traits and excluding the interference of genetic factors. We investigated the stomatal, structural, chemical, and vein traits of Daphniphyllum macropodum leaves in middle-aged forests, following the altitudinal gradient (1100, 1500, and 1900 m) on Mao'er Mountain. The objectives of this study were to reveal patterns in leaf trait and leaf trait networks variation, the life strategy of the tree species, and the major environmental factors affecting the altitudinal variations. The results showed that leaf area, specific leaf area, leaf thickness, leaf dry matter content, chlorophyll content, nitrogen content, phosphorus content, C:N, C:P, vein density, and vein diameter varied significantly across altitudes. Mean annual temperature and total radiation explained 42.1% and 16.2% of leaf-trait variation, respectively. They served as key environmental factors driving the altitudinal variation in leaf traits. Mean annual temperature exhibited the greatest influence on leaf area (R2=0.73), and total radiation exerted the most prominent effect on leaf thickness (R2=0.72). Both relationships were significantly positive. D. macropodum exhibited low leaf nitrogen and phosphorus at the low altitude of 1100 m, and the overall and local trait networks were loose, adopting a conservative resource strategy. At the medium altitude of 1500 m, leaf nutrient contents were relatively high. The overall network of leaf traits was tightly connected and local network was loose. By enhancing the dependency among leaf traits, and improving phosphorus utilization efficiency, D. macropodum could cope with competition in deciduous forests and adopt resource acquisition strategies. Further, at the highest altitude of 1900 m, D. macropodum had relatively large leaf thickness, chlorophyll content, and leaf dry matter content, but relatively small leaf area. The local network connections were tight while the overall network looseness, indicating a resource conserving strategy. The trade-off relationship between C:P and leaf phosphorus content was closely related to phosphorus use efficiency, and its variation was an important indicator for identifying life strategies of D. macropodum in different altitudes.

[Tree architecture variation of plant communities along altitude and impact factors in Maoer Mountain, Guangxi, China]. / çŒ«å„¿å±±ä¸åŒæµ·æ‹”æ¤ç‰©ç¾¤è½æ ‘æœ¨æž„åž‹å·®å¼‚åŠå ¶å½±å“å› å­.

Three typical plant communities (evergreen broad-leaved forest at low-altitude 1100 m, evergreen and deciduous mixed broad-leaved forest at mid-altitude 1500 m, and evergreen conife-rous and broad-leaved mixed forest at high-altitude 1900 m) in Maoer Mountain, Guangxi, China were surveyed along an altitude gradient. We measured the tree layer plant architecture and environmental factors, to analyze the variation of plant architecture traits among the three communities and its influencing factors. The results showed that the tree layer canopy area, basal diameter at 45 cm height, diameter at breast height (DBH), and leaf convergence increased with increasing altitude, whereas tree height, branch height, and canopy thickness first increased and then decreased. Horizontal branches occurred more often in communities at lower altitude , less frequent at high altitude, and the least frequent in middle altitude communities. Correlations among tree layer plant architecture traits were stronger in the mid-altitude community than that in the other altitude communities. Results from the redundancy analysis showed that soil organic matter and total solar radiation were the main factors driving the variation of plant architecture traits in the tree layers, accounting for 39.6% and 23.9% of the total variation, respectively. Soil organic matter had a greater positive impact on canopy area and branch height, whereas total solar radiation was more influential on the DBH and 45 cm basal diameter. In conclusion, tree layer architecture of communities along the altitude gradient in Maoer Mountain was divergent, with soil organic matter and total solar radiation as the main driving forces.

Effects of stand type of artificial forests on soil microbial functional diversity.

We explored the changes of soil microbial biodiversity in response to forest ecological restoration. Soil samples were collected from the close-to nature managed Chinese fir plantation (CF), Moso bamboo plantation (MB), and natural secondary forest (NF). Soil microbial community diversity was analyzed by Biolog-Eco micro-plate technique. The results showed that plant diversity was significantly different among the three stands. Plant diversity of NF was significantly higher than MB and CF, and MB was higher than CF. Soil pH and bulk density showed a great difference, while there was no difference of other soil physiochemical properties among the three stands. Avera-ge well color development (AWCD) of soil in various stands followed the order of NF＞MB＞CF, consistent with the changes of utilization of six types of carbon sources. Shannon index of NF was the highest, and the index of MB was significantly higher than that of CF. Soil physical and chemical properties in different stands were not significantly different, except soil pH and bulk density. The Shannon diversity index (H), Shannon species richness index (S), Simpson dominance index (D) and McIntosh index (U) were the highest in NF, second in MB, and the lowest in CF. Results from principal component analysis (PCA) showed that two factors from 31 carbon sources could explain 60.0% and 12.4% of the variation and that carboxylic acids, carbohydrates and its derivatives, amino acids were the main carbon sources of the two principal component factors. Correlation analysis indicated that plant species richness and Shannon diversity indexes, soil bulk density were significantly correlated to soil microbial community diversity. The microbial community of NF was more efficient in carbon utilization than that in MB and CF, while that in MB was more efficient than that of CF. Based on plant diversity and soil microbial carbon utilization, MB is much better than CF in the artificial forest restoration and improvement in South China.

[Effects of topography on the diversity and distribution pattern of ground plants in karst montane forests in Southwest Guangxi, China].

Covariance analysis, curve-fitting, and canonical correspondence analysis (CCA) were used to explore the effects of topographic factors on the plant diversity and distribution patterns of ground flora with different growth forms in the karst mountains of Southwest Guangxi, China. A total of 152 ground plants were recorded. Among them, 37 species were ferns, 44 species herbs, 9 species lianas, and 62 species shrubs. Covariance analysis revealed that altitude significantly correlated with the individual number and richness of ground plants, and slope aspect had a significant effect on richness. Statistical analyses showed a highly significant nonlinear correlation between the individual number or richness of ground plants and altitude. Results of CCA revealed that slope aspect had a significant effect on the distribution pattern of ferns, and slope had a significant effect on the distribution patterns of herbs, lianas and shrubs. Ferns were more sensitive than herbs, lianas and shrubs to changes in heat and soil water caused by aspect. The effect of slope was stronger than that of elevation on soil water and nutrients, and it was the most important topographic factor that affected the distribution patterns of herbs, lianas and shrubs in this region.