| The quest for general rules linking body size and metabolism has concerned plant ecologists for decades. As sap flow and stem temperature can indicate hydrothermal conversion between individuals and environment they are crucial for the understanding of metabolism process. Analyzing the difference and relationship of sap flow/stem temperature between vertical layers and individuals in plant communities is crucial for understanding species coexistence and community assembly.We conducted the study in a Schima superba community located in Tiantong, Zhejiang province. Tree architecture and physiological characteristics of light utilization and water transport capacity were measured. Light utilization and water transport characteristics include sap flow (Js), stem temperature (Ts), maximum photosynthetic rate (P), light compensation point (LC), saturation point (LS), stomatal density (Sd), xylem vessel density (Vd), vessel diameter (Vdia), wood density (WD), hydraulic conductivity, specific conductivity sapwood. While tree architecture characteristics include height (H) and diameter at breast height (DBH). Paired T test and One-way ANOVA were used to test the difference of Js/Ts between vertical layers and different seasons respectively. Further, Linear regression were used to test the WBE model. Principal Component Analysis (PCA) and Pearson correlation analysis were used to investigate the relationship between plants architecture characteristic and Light utilization and water transport characteristics. The results were as follows:(1) Based on one day’s trends, Plants sap flow reached the maximum value at high noon, while keeping a lower level at night, and tend to be higher in tree layer than in shrub layer. Based on one year’s trends, the sap flow was highest at summer, while lowest at winter, and still higher in tree layer. The sap flow was positively correlated to Photon Flux, air temperature, soil temperature and soil temperature, while negatively correlated to air humidity.(2) The stem temperature both of tree and shrub showed high at daytime, low at nighttime. But tree stem temperature was lower at day and higher at night than shrub, moreover, the maximum/minimum temperature of trees appeared lagging behind shrubs about one or two hours. On the stem temperature dynamic throughout the year, highest at summer and lowest at winter. For daily range of Stem temperature, shrubs were bigger than trees at four seasons. There were positive correlation between stem temperature and PAR Photon Flux, Air temperature, Soil temperature, Soil water content, Air humidity, while negative correlation between stem temperature and wind speed.(3) The exponential function based on sap flow, sap daily transpiration, difference of stem temperature and maximum photosynthesis rate were tends to be identical with the WBE model.(4) In this study, tree height was positively correlated to sap flow, mean leaf area, vessel diameter, twig lumen area, stomatal density, maximum photosynthesis rate, Light saturation point, Light compensation point, Hydraulic conductivity and Sapwood specific conductivity, while negatively correlated to specific leaf area and wood density.(5) leaf functional traits, light utilization and water transport capacity characteristics were different between tree and shrub, which lead to different position along the height economic spectrum:Trees trend to be Acquisitive, while shrubs act more conservative.In summary, this study analyzed the hydraulic and temperature dynamic of two growth form, metabolic relationships and economic spectrum. These results verified the metabolism rate of the WBE model and clarified the plant water-light utilization difference in vertical layers, which revealing the growth strategies in different growth forms and can help us better understanding the theory of species coexistence and community assembly. |
