| Forest plays an important role in ecosystem, which can intercept precipitation, deposit water, reduce runoff, prevent soil erosion and improve environment and climate. However, forest also consumes large amounts of water. With the development, water shortage problem is more and more serious. The huge water which trees consume has become a prominent contradiction. It will reduce the water consumption by selecting appropriate trees and stand structure in the afforestation and restoration process in Shandong province.The plant transpiration research has become a focus of plant physiological ecology. Now, more and more methods have been developed to measure plant transpiration, from leaves level to the individual level and then to group level, there are a large number of research methods. The sap flow of plants stem is driven by the plants water uptake, so it can represent plants transpiration. The sap flow was detected by the stem-heat-balance or the heat pulse method.In this study, four main plantation species in the warm temperate zone in Shandong province are selected as the objects, which are Platycladus orientalis, Armeniaca sibirica, Diospyros lotus, Robinia pseudoacacia. The sap flows of four plants and environment factors in fast growing season have been collected by the plant-circadian-measure-system named Phytalk system, in order to discover the patterns of transpirations and analyze the response to environment factors, and then establish the model between sap flow and environmental factors. It will provide basic data and theory on water deprivation patterns, water use efficiency and vegetation restoration in specific area.During the rapid growing season, the sap flow rate and the daily cumulative volume of four plants showed relatively consistent patterns. The curves of sap flow were single-peak curves and double-peak curves, which were consisted of five parts, the stationary phase before dawn, rising phase, acrophase, decline stage and stationary phase again after dark. The sap flow rate showed differences between different plants. In most of time, and Robinia pseudoacacia were double-peak curves with a midday rest phenomenon, Armeniaca sibirica and Diospyros lotus were single-peak curves. The cumulative amount of stem flow showed S-shaped curve. The four plants showed the same rule, but the cumulative amount of sap flow were varied, the smallest was P. orientalis. Robinia pseudoacacia, Armeniaca sibirica and Diospyros lotus displayed discordantly in different months.The sap flow rate of four plants showed changes within different species. The average transpiration rates were varied between different species. The sap flow rates of broad-leaved plants were faster than the conifers. The sap flow rate variation between different species, which was relative to the biological characteristics.The sap flow rate was affected by environmental factors, which include solar radiation, air temperature, wind speed, air humidity and soil moisture. Solar radiation, air temperature and wind speed have positive correlation with the sap flow rate, air humidity and soil moisture have negative correlation with sap flow rate. Environmental factors were analyzed by principal component analysis (PCA), and divided into two main components, meteorological factors and soil factors. Meteorological factors included solar radiation, air temperature, air humidity and wind speed. The curve between meteorological factors and sap flow rate was secondary curve or logarithmic curve. In a certain range, sap flow rate was accelerated in pace with the increase of meteorological factors, then reached the maximum, meteorological factors continued to increase, but sap flow rate remained constant or decreased. Soil factors had a complex relationship with sap flow rate. We did not get a higher fitting equation. But on the whole, the sap flow rate had an accelerated trend when soil moisture rose. |
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