Research On Effects Of Environmental Temperature On The Trunk Moisture Content And Ice Content Of Standing Trees

China's northeast forest region in temperate and cold temperate zone,about 37% of the national forest area.One of the most important factors in this region is the environmental temperature.Trees grow without water.Then different environmental temperature affects the forest community structure,species composition,tree growth,growing material and so on.Therefore,it is necessary to research the effects of moisture content(MC)of standing trees on environmental temperature,and improve the utilization rate of wood and achieve precise wood nondestructive testing.In order to reveal the effects of environmental temperature on the electrical internal MC and ice content of standing trees,two(Larix gmelinii and Populus simonii)standing tree specimens were selected and tested in different outdoor temperatures(26.0??-23.5?).Through field long time tests,some electrical impedance two-dimensional images of cross section of specimens were then obtained by using electrical impedance tomography instrument,continuous variation of electromagnetic wave propagation time were then obtained by using time domain reflectometer instrument,then deduced the MC and ice content.And calibrated the laboratory data through laboratory instruments.Through the different angles observated the effects of environmental temperature on the MC and ice content of standing trees,analysised of different environmental temperature caused by MC and ice content.Finally,a mathematical model was established to predict the environmental temperature,MC and ice content,verificated and calibrated model.Research results show that:1)In a longer period of time(2014.11.06~2014.12.22),the MC of the sample trees decreased with the decline of daily average tree temperature(3.5?~-15.2?),ice content increased.The change rate of MC and ice content variation curves of Larix gmelinii samples with environmental temperature are higher above-6.3?,less below-6.3?.The change rate were 14.75%/? and 0.94%/?.The change of Populus simonii was similar to it and the change jump point is-6.9?.2)The relationship between environmental temperature and MC could be described as three polynomial relationship,their coefficient of determination of R2 were higher than 0.62.The relationship between environmental temperature and ice content could be described as three polynomial relationship too,their coefficient of determination of R2 were higher than 0.77.So the environmental temperature could be used to predict the MC and ice content of standing trees.3)The correlation between the temperature in the tree and environmental temperature is significant(P<0.01).The environmental temperature could be predicted by using temperature in the tree.Then it is feasible to predict the MC and ice contents of standing trees.4)As environmental temperature decreases,the two samples resistance value were increases.There is a highly significant exponential regression model between them(P<0.01).The trend line of resistance value and environmental temperature jumping at zero temperature.When section resistance value more than 20000?,ice crystal formed.The reasons of environmental temperature transform on MC and ice contents of standing trees,mainly because the decrease of the activation energy of wood is due to the decrease of temperature.Free water content decreased,free ions moved slow down,then the internal conductivity decreased,resistance increased,overall MC decreased.When the temperature below 0?,a portion of the free water is slowly converted to ice,then ice content increased and the resistance value increased in geometric multiples.This is due to the water phase transition.In conclusion,the research provide strong theoretical support for real-time,accurately determine the standing trees internal MC and ice content,for the more accurate judgment of wood defects in different states,for the normal growth and development,effective implementation of water-saving technology system and so on.And hope to provide a theoretical basis for the low temperature high quality nondestructive testing unit,as provide a scientific basis for wood trunk cracking,low temperature brittle fracture and frost resistance of trees.