Characteristics Of The Sap Flow Rate Of The Eucalyptus And Its Response To Environmental Factors In Tropical Semi-humid And Semi-arid Areas

Eucalyptus have rapid growth,short rotation and well-adapted characteristics.It is suitable for intensive management and high-yield cultivation.Eucalyptus has became the Fast-growing strategy tree species in the south of china,and holds a large proportion in the plantation cultivation.Hainan in the Midwest for special habitat in tropical semi-humid,semi-arid area,it is also one of the important Eucalyptus forest tree planting area in china.Although the fast-growing Eucalyptus can bring us a good economic profit,there is a controversy will make negative ecology effect for the surrounding water and soil.Danzhou Forest Farm, which lies in western Hainan Island, was chosen as a research area,We selected Eucalyptus trees and Cocos trees with adjacent space and similar natural conditions as our experimental plots.Comparing different years between woodlands and soil water. Select 3a Eucalyptus plantation plots, using TDP measurement system to measure the Eucalyptus sap flow rate,analysis flow density of solar radiation, relative humidity,air temperature and different soil water response.To explore the change characteristics of the sap flow density of the young Eucalyptus and its relationships with environmental factors,and estimates 3a large-scale Eucalyptus plantations transpiration water consumption,provide a scientific basis for clarifying the impact of Eucalyptus cultivation on soil water ecology and for the Eucalyptus plantations sustainable operation and management.The results showed that:(1) In the area of solar radiation,air temperature,relative humidity,vapor pressure diurnal changes significantly,while rainfall and soil water change complex;rainfall concentrated in 6 to 10 months,and from 11 to 5 of next year rainfall is less. Soil moisture content decreased continuously from January to April, fluctuated in May and June, increased to the annual maximum between July and October, and descended slightly during the remaining months. compared with the Cocos forest and Eucalyptus forest, short-rotation Eucalyptus forests consumed more water in the deep soil.(2) The diurnal variation of Eucalyptus sap flow density takes on the same change rule that mostly are single curve,but in sunny, cloudy and rainy days, the stem sap flow density were significant differences. The daily change of flow density takes on typical single curve in sunny days and atypical single curve or polymodal curve in cloudy days, but the diurnal variation is not obvious and the flow density is smaller. The average daily maxinum peak and daily average of Eucalyptus whose diameter class is 6.5cm are 2.27 times,1.50 times in cloudy days and 7 times、3.74 times in rainy days.The 5.6 diameter class flow density peak of the Eucalyptus is over 12 m L·cm-2·h-1 in sunny days,and it is more earlier;However the flow density peak from Semtemper 2014 to January 2015 is below 8 cm-2·h-1in sunny days,and it appeared relatively late.(3) Satistics do show a positive correlation between solar radiation and the density of sap flow in sunny days.while it does show a negative correlation in relative humidity,and the influence of solar radiation is greater;In cloudy days,the flow density has a positive correlation to the air temperature and solar radiation,while it does show a negative correlation between the flow density and relative humidity,and the influence of solar radiation is greater for the flow density.In rainy days,the sap flow density has a positive correlation to the air temperature and solar radiation,and the air temperature has greater impact for the flow density.The sap flow density In the cloudy and rainy days has no correlation to the soil water,and it does show a negatively correlation between flow density and soil water in sunny days.(4) DBH is 5.6cm、6.8 cm、8.8 cm、10.8 cm、12.4 cm for Eucalyptus standard wood sapwood area is 24.97 cm2、36.30 cm2、60.8 cm2、91.60 cm2、120.70 cm2, increased to 30.18 cm2、39.57 cm2、70.85 cm2、107.46 cm2、130.63 cm2 from 8 June 2014 to 31 January 2015.Each diameter class is according to the standard wood accumulation and the sap flux respectively is 239.21、454.82、1432.93、1513.19、1500.10L;3a large-scale Eucalyptus plantations transpiration water consumption 2668366.52L?hm-2 or 266.84 mm,the average daily 1.12 mm, accounting for about 29%of the local annual average rainfall over the same period.