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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 ( R 2 =0.73), and total radiation exerted the most prominent effect on leaf thickness ( R 2 =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.

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.

To examine the change of runoff and its reason is an important scientific issue in forest hydrology. In this study, we performed the trend and inflection analysis on the time series of daily precipitation and runoff in the Pengchongjian small watershed from 1983 to 2014 by Mann-Kendall test method, a site with abundant precipitation . Using the empirical statistics method, we analyzed the effects of precipitation variation and vegetation restoration on the runoff and its contribution rates. Furthermore, we calculated the critical value of the hydrological effect of vegetation restoration on the annual precipitation. The results showed that the year 2003 was a consistent abrupt point for annual precipitation and runoff. Compared to the baseline period (1983-2003), annual precipitation and the depth of runoff in the changing period (2004-2014) decreased by 8.7% and 29.2%, with the averaged annual decrease of 12.7 and 22.1 mm, respectively. The averaged depth of runoff in spring, summer, autumn, winter, and in the whole year decreased by 100.2, 105.8, 25.2, 23.4, and 243.0 mm, respectively. The contribution rates of the depth of runoff to precipitation varia-tion were 58.9%, 71.6%, 65.5%, 35.0%, and 57.1%, respectively, while the contribution rates of vegetation restoration were 41.1%, 28.4%, 34.5%, 65.0%, and 42.9%, respectively. The hydrological effect of vegetation restoration was attributed to the annual precipitation, with a critical value of 1181 mm. Vegetation restoration increased annual depth of runoff when annual precipitation was less than the critical value, and increased that when annual precipitation was higher than the critical value. Therefore, the critical value might help to explain the difference in contribution rates of vegetation restoration to runoff in different watersheds and serve as one of the important reasons for the debate and divergence of forest restoration impacts on runoff.