Characteristics of Photosynthesis and Water Use of Dominant Tree Species in Two Typical Forests and Related Factors in the Semiarid Region of Loess Plateau, China
|School||Graduate School,Chinese Academy of Sciences|
|Keywords||Loess Plateau Typical Forests Photosynthetic Transpiration Water Consumption Semi-arid areas|
Very fragile ecosystem of semi-arid areas of the Loess Plateau. Serious soil erosion and drought are two major ecological problems facing the region. Sustainable recovery of the vegetation is the fundamental way to regional ecological security in the area of ??governance and water resources protection. Contradiction revegetation and water shortage in the ecological restoration of the area, the semi-arid areas of the Loess Plateau two typical stand Liaodong oak natural secondary forest and locust plantation in Yan'an City Road, Forest Area, the application of LI-6400 portable photosynthesis system on two typical stand species leaf photosynthesis, transpiration characteristics and its influencing factors were studied. TDP sap flow measurement system and automatic weather station positioning observation of a single the wooden water consumption characteristics of two typical stand species and corresponding environmental factors; systematic analysis of the two typical stand each species trunk sapwood liquid circulation The influencing factors of the amount of density; estimate the 2008 growing season, two typical stand transpiration. The main results are as follows: 1, the two main species of Typical Forests locust and oak Photosynthetic diurnal growing season sunny bimodal or single peak curve, two of the main tree species are obvious \The reasons for the two species \The impact of the two species \Locust is higher than the maximum photosynthetic capacity the Liaodong oak maximum photosynthetic capacity, but the average daily photosynthetic rate was less than the average photosynthetic rate of the the Liaodong oak growing season day. The two species leaf net photosynthetic rate and stomatal conductance, intercellular CO2 concentration, photosynthetically active radiation, air temperature, CO2 concentration, air water vapor pressure difference and the relative humidity of the air very significant or significant related. The dominant factors that affect the net photosynthetic rate of the two species is a physiological factor (Gs and Ci), ecological factors may indirectly affect leaf photosynthesis of trees through the leaves of the two species Gs and Ci. Light response curve analysis showed that aggravated soil drought, the blade carbon sequestration capacity of the two species and the ability to take advantage of the low light and bright light reduced. 2 showed a single peak in the diurnal variation of the growing season, locust and oak leaf transpiration rate curve or irregular multimodal shaped curve. Seasonal differences in the process of leaf transpiration rate of the two species may be associated with the biological characteristics of the two different species, it may be due to differences of the growing season in different periods of the ecological factors. Different periods during the growing season, the two species leaf transpiration rate and stomatal conductance, photosynthetic active radiation, air temperature, relative humidity and air water vapor pressure difference has a very significant or significant relationship. The growing season in different periods of physiological and ecological factors affect the two species leaf transpiration rate. 3, locust plantations and oak natural secondary forest species sapwood flow flux density diurnal variation on sunny days with daily solar radiation and water vapor pressure difference similar trend. Two typical stand species (locust, oak and wild apricot) of different diameter trees there are significant differences in the sapwood flow flux density. All sorts of tree growing season average the sapwood flow flux density with the corresponding DBH There was no significant correlation between the two major Typical Forests species the sapwood flow flux density may be affected by the constraints of multiple physiological and ecological factors. Typical Forests growing season average species stands the the sapwood flow flux densities date change in the sunny typical single-peak curve, overall bimodal curve in cloudy and overcast. Each species average daily stand sapwood flow flux density showed a sunny gt; cloudy days gt; cloudy day, may be related to the significant differences in various ecological factors under different weather conditions. The start-up time of two typical stand each species liquid flow, flow duration, average edge material flow flux density peak and peak time differences in different months. Daily maximum the sapwood flow flux density value of the overall performance of the growing season early (April) and late (10 months) is low and growth high peak seasonal dynamics. Each species sapwood flow flux density in the growing season, most of the time by solar radiation, air temperature, relative humidity and air water vapor pressure of the combined effects of poor ecological factors. Average major tree species of the growing season in different periods typical stand sapwood flow flux density and ecological factors of optimal multivariate linear regression model were highly significant level of ecological factors using multiple linear regression model can explain the large some trees the average sapwood flow flux density changes. Using a power curve model can be fitted regression equation between the locust plantation and oak natural secondary forest species (locust, oak and wild apricot) sapwood area and DBH, combined investigate major species single wooden stand DBH can calculate the corresponding trees sapwood area. Plantation of black locust and oak natural secondary forest each species stands average sapwood flow flux density has obvious seasonal dynamics characteristics. The average sapwood flow flux density of each species stands seasonal variation may be associated with different biological rhythm of each species leaves during growing season, changes in meteorological factors and soil moisture content. The stand transpiration measured period of two typical stand each month can stand each species transpiration water consumption during the day and the average daily water vapor pressure difference between the non-linear regression model to estimate. During the growing season from May to July for two typical stand transpiration higher period. Locust plantations in the 2008 growing season and oak natural secondary forest transpiration total water consumption were 73.8 mm and 127.85 mm; daily stand transpiration water consumption were 0.41 mm day-1 and 0.63 mm day-1. Two typical stand the relatively low average daily stand transpiration water consumption may be smaller leaf area index and stand and stand sapwood area. 5, except the surface 0 ~ 10cm of Liaodong oak natural secondary forest of soil bulk density higher than Acacia Forests; the 100cm depth woodland soil bulk density remained constant. Of two typical stand the dynamic changes of soil moisture with the outside world climate change and stand Transpiration Water Consumption rhythm of closely related; 0 to 300cm soil layer soil moisture changes are larger; 300 ~ 500cm soil layer soil moisture to maintain a relatively stable low value. The Liaodong oak natural secondary forest ground deep (underground 300 ~ 500cm) average soil moisture and water storage capacity is higher than the average soil moisture and water storage capacity of the corresponding layers of the locust plantation; native species Liaodong oak constructive species of natural secondary forest under soil moisture conditions is superior to the other than to the main plantation species locust.