Luận án ảnh hưởng của tuổi cây, vị trí trên cây đến cấu tạo và tính chất của luồng (dendrocalamus barbatus hsueh et d z li) làm cơ sở định hướng sử dụng11

MINISTRY OF AGRICULTURE AND MINISTRY OF EDUCATION AND RURAL DEVELOPMENT TRAINING VIETNAM NATIONAL UNIVERSITY OF FORESTRY NGUYEN VIET HUNG EFFECTS OF AGE, POSITION ON THE STRUCTURE AND PROPERTIES OF BAMBOO (Dendrocalamus barbatus Hsueh et D Z Li) AS THE BASIS FOR USAGE ORIENTATION Majority: Forestry Processing Technology Code: 9.54.90.01 SUMMARY OF ENGINEERING DOCTORAL THESIS Ha Noi – 2022 Research work is completed at: Vietnam National University of Forestry Trường Đại học Lâm nghiệp Việt Nam Scientific instructors: Professor, Dr Pham Van Chuong Reviewer 1:…………………………………………… Reviewer 2:…………………………………………… Reviewer 3:…………………………………………… The defense will be taken in front of the Institutional Board of Thesis Evaluation at: Vietnam National University of Forestry At: … time, Date ….Month… Year 2022Thn The thesis can be found in the libraries: National Library; Vietnam National University of Forestry Library học INTRODUCTION Currently, the harvesting of D barbatus for production purposes is usually in the ages above and On the other hand, the reality shows that production facilities have also used different tree positions for products However, the exploitation at different ages, and the use of positions on the trunk that have not been scientifically proven will reduce the use value of Luong, not taking advantage of the best properties of the D barbatus with age and positions on the trunk, which leads to waste and inefficient use of this plant According to many studies in the world and in the country, the properties of bamboo in general are closely related to the age of growth and the position on the trunk The anatomical characteristics, chemical composition, physical properties and mechanical properties of bamboo tend to be better as the tree is cut down at an older age However, in each different bamboo species, the variation in structure, properties and chemical composition at different age levels and positions on the tree follows different rules Therefore, each species of bamboo needs to have specific studies for that species in order to have appropriate views, analyzes and orientations for each different species Studies on structural variation, properties of D barbatus between positions on the trunk and the age of the tree are not available Therefore, the research to find out the law of variation in the structure and properties of D barbatus according to age and positions on the trunk serves as a scientific basis to determine the appropriate age of D barbatus for use From those issues, we conducted a study on the thesis "Effects of age and height position on the structure and properties of Dendrocalamus barbatus as the basic for usage orientation " Chapter RESEARCH SITUATION OVERVIEW 1.1 Overview of research on changes in structure and properties of bamboo according to age and positions on the trunk and use orientation 1.1.1 Research situation abroad There have been many studies on bamboo in the world, those studies have studied the changes in the structure and properties of bamboo according to the age of the tree and the positions on the trunk Each study has shown certain rules according to different species, different growing regions However, there is no research on D barbatus in Vietnam 1.1.2 Research in the country In Vietnam, there have been many research projects on bamboo In which, there are basic studies changes in some properties of bamboo according to tree age and position on the trunk There have not been any researches on structural changes, chemical composition and physical and mechanical properties of D barbatus in Vietnam 1.2 Conclusions drawn from the review 1.2.1 Conclusions from related research Through the results of an overview of related research, we summarize and make some comments as follows: - Researches in the world have confirmed: Different tree species, tree age, positions on the trunk, site conditions, harvesting season all affect the structure, chemical composition, physical and mechanical properties of bamboo to varying degrees - Previous studies have not analyzed the correlation between the structure and the physical and mechanical properties of bamboo species, so the nature of the fluctuations in the physical and mechanical properties of bamboo has not been clear according to age and position on the trunk according to structure - There have been a few works in the country related to the research problem (Effect of tree age and location on the trunk on some properties of bamboo in general) For D barbatus in Vietnam, studies have only stopped studying the structure, chemical composition, physical and mechanical properties of age level and a certain position on the tree trunk There is a study on the variation in density, static flexural strength, and longitudinal compressive strength of D barbatus grown in Phu Tho from the age of to 4, but in a specific positions, the variation in grade has not been studied age and different positions on the trunk There have been no studies on the change in structure, chemical composition, physical and mechanical properties of D barbatus in Thanh Hoa according to tree age and positions on the trunk 1.3.2 Research direction of the thesis Based on the above research results, we found that finding a law of variation in the structure, properties and correlation between the structure and properties of a bamboo species with age and positions on the tree trunk harvested on a specific site condition have scientific and practical significance - Research bamboo species: Dendrocalamus barbatus, harvested in Quan Hoa district, Thanh Hoa province at age levels 1, 2, 3, 4, years Reasons for choosing species and age level: D barbatus is currently being grown popularly and with large reserves across the country in general and Thanh Hoa in particular The harvest and actual use is mainly from the age of to the age of 5, In order to see the change in age to the structure and properties of the Stream, it is necessary to analyze the age levels continuously The use of tree positions has not been studied in depth for different age levels Therefore, the thesis selects age levels from age to age to study the variation of properties by age level and positions on the trunk and the relationship between structure and properties of this species Research results have important implications for applied research, practice of using and trading Luong for different purposes - Orientation of research content: Study of changes in structure, chemical composition, physical properties and mechanical properties of D barbatus by tree age and positions on the trunk In particular, determine the nature of the influence (correlation) between the structure and the physical and mechanical properties of D barbatus according to tree age and positions on the trunk 1.4 Object and limitations of the thesis 14.1 Research object of the thesis Variation in structure and some properties according to tree age and position on the trunk of D barbatus grown in Thanh Hoa, Vietnam 1.4.2 Research limitations of the thesis - D barbatus tree is grown in Quan Hoa district, Thanh Hoa province (Coordinates UTM 48Q 0491274, 2254852); - Analysis of changes in structure and properties from age to age 5; - Structure and properties of D barbatus are determined in the internodes at positions: bottom, Middle and top; - Determine the structural parameters of Luong: wall thickness, fiber length, fiber diameter, vascular bundle density, vascular bundle destruction, vascular bundle size, fiber cell wall thickness; - Determination of chemical composition: Holo-cellulose content, cellulose content and lignin content; - Determination of physical properties: density, shrinkage and moisture; - Determination of mechanical properties: compressive strength along the grain, static bending strength, elastic modulus of static bending, shear strength along the grain; 1.5 Objectives of the study 1.5.1 Overall objectives Determining the changes in structure, chemical composition, physical properties and mechanical properties of D barbatus according to tree age, position on the trunk, as a scientific and practical basis for business and rational use of D barbatus in Vietnam 1.5.2 Detail goal - Determine the influence of tree age and position on the trunk on the structure and chemical composition of D barbatus - Determine the influence of tree age and position on the trunk on the physical and mechanical properties of D barbatus - Orientation to harvest age and reasonable use of Luong trunk for different uses 1.6 Scientific significance 1.6.1 Scientific significance Research results contribute to clarifying the nature of changes in structure, chemical composition of D barbatus age and positio on the trunk; relationship between structure and physical and mechanical properties of D barbatus 1.6.2 Practical significance The research results are the basis for determining the reasonable harvest age, and the orientation of using and trading Luong trees for different purposes in Vietnam 1.7 New contributions of the thesis - The thesis is the first work in Vietnam to study in detail the structural changes, chemical composition, physical properties and mechanical properties of Luong with age and position on the tree trunk; - The thesis has studied the correlation between the two factors age, position on the trunk to the change in structure, chemical composition, physical and mechanical properties of D barbatus ; - Research results will contribute to clarifying the nature of changes in physical and mechanical properties of D barbatus with age, position on the trunk through changes in structure; - The research results are the basis for determining the reasonable harvest age, and the orientation for using and trading D barbatus in Vietnam Chapter RESEARCH CONTENTS AND METHODS 2.1 Research content - Effect of age and position on the trunk on the structure of D barbatus - Effect of age and position on the trunk on the chemical composition of D barbatus - Effect of age and position on the trunk on the physical properties of D barbatus - Effect of age and position on the trunk on mechanical properties of D barbatus - Harvest orientation, use according to age and position on the trunk of D barbatus 2.2 Research Methods 2.2.1 Experimental methods 2.2.2.1 Select tree, sampling location and cutting Method of selecting sampling trees according to the Standard GB/T 157801995) Method of determining the age To get the most accurate results, the thesis has applied a combination of methods (1) Based on the development of new outcrops through the stem that easily grows horizontally from the base of the existing stem, and then develops into a new outgrowth (2) The method of determining the age of bamboo shoots is by counting the number of leaf scars on the branches In winter, bamboo leaves fall for about 12-15 months Soon new leaves are sprouted from the proximal node of the fallen leaves, leaving leaf scars on the branches For Luong, the leaves will be changed once a year, so the scars left behind will be counted as year (3) Determining the age of bamboo based on the color change on the bamboo trunk The color of one-year-old stems is usually bright green, and the surface of the trunk is thinly grooved As the stems age two and three, their color becomes more yellow From the age of four on, the color of the trunk almost turns gray and fungi and moss appear on the surface of the trunk 2.2.2.2 Microscopy preparation method and fiber size The process of cutting specimens and performing fibroblasts was carried out at the laboratory of Wood Science Department, Forest Industry Research Institute, Vietnam Academy of Forestry Science + Optical microscope Olympus BX41, Magnification 40, 100, 400, 1000 (10x eyepiece equivalent, with wide field of view F.N=20 mm), Glasses combined with Pax-it!2 software on computer to measure sample size + Microm slide cutter HM440E can cut samples with thickness 1100 µm 2.2.2.3 Method for determining the physical and mechanical properties of Threads The mechanical and physical properties of the Thread are determined in accordance with GB/T Standard 15780-1995 2.2.2.4 Determination of the chemical composition of Stream Determination of cellulose content Determination of cellulose content by method (Kiursher – Hofft) based on standard TPPI T 17 wd – 70 Determination of holo-cellulose content: determined according to ASTM D 1104-56 standard Determination of lignin content: The lignin content was determined according to the standard (TAPPI-T 222 om-02) Chapter RESEARCH RESULTS AND DISCUSSION 3.1 Effect of tree age and position on tree structure 3.1.1 Effect of tree age, position on the trunk on wall thickness Table 3.1 Thread wall thickness at different ages and positions (mm) Ages (years) Bottom 13,68 14,08 15,00 15,76 16,09 Middle 6,56 6,69 7,19 7,77 8,09 Top 4,70 4,74 5,00 5,51 5,92 Through the data recorded in Table 3.1, it shows that D barbatus wall thickness fluctuates with age and position on the tree trunk According to tree age, in positions, the thickness of Luong Thanh wall changes with tree age from age to age 5, but that variation is not much According to the position on the trunk, there is a variation in the thickness of the D barbatus wall at all age levels from bottom to top position Through analysis of variance, it was found that tree age and position on the trunk were different for the thickness of the wall thickness The age does not affect the wall thickness according to the position on the trunk The position on the tree trunk has a more obvious effect on the D barbatus wall thickness, the age has a negligible effect on the D barbatus 's wall thickness The age group between age and age 2, age and age have no difference in wall thickness 3.1.2 Effect of age and position on the trunk on the arrangement and size of vascular bundles 3.1.2.1 Effect of tree age, position on the stem on the arrangement and density of vascular bundles Table 3.2 Vascular bundle density of D barbatus at different ages and position (bundle/mm2) Ages (years) Bottom 3,03 3,09 3,21 3,02 2,86 Middle 3,99 3,95 4,20 4,24 4,08 Top 4,94 4,95 5,18 5,43 5,17 Through the results recorded in Table 3.2, we can see that the density of vascular bundles varies according to age At the bottom, the vascular bundle density increased gradually from age to age and decreased slightly to age and 5, ranging from 2.86 to 3.21 bundles/mm2 However, the variation in vascular bundle density with tree age was not significant According to stem height position, at all age levels, the density of vascular bundles increases from bottom to top The results of the analysis of variance showed that there was a difference in the density of vascular bundles when changing the age and the position on the stem Plant age affects the density of vascular bundles according to the position on the trunk Position has a clear influence on vascular bundle density, while age has no significant effect on vascular bundle density Age group and age 2, age group and age 5, age group and age 5, age group and age had no difference in vascular bundle density of D barbatus The results of the correlation analysis between the density of vascular bundles with the age and the position on the stem are shown by equation 3-1: Dv = 2,681 + 2,608X1 + 0,35X2 R2=93,8% (3-1) In there: Dv- density of vascular bundles, bundles/mm2 X1- position, % trunk height; X2- ages, years Position 3.1.2.2 Effect of age, position on the stem on vascular bundle size Table 3.4 Vascular bundle size of D barbatus at different age and position on the trunk Ages Position Middle 0,431 0,387 0,445 0,389 0,479 0,359 0,478 0,393 0,438 0,387 Bottom Top XT (mm) 0,499 0,400 TT (mm) 0,370 0,412 XT (mm) 0,533 0,432 TT (mm) 0,384 0,382 XT (mm) 0,535 0,408 TT (mm) 0,388 0,362 XT (mm) 0,524 0,444 TT (mm) 0,366 0,367 XT (mm) 0,549 0,422 TT (mm) 0,388 0,382 - Note: XT- Radial, TT- Tangent Table 3.4 shows that the size of radial vascular bundles between ages does not differ much The size of the vascular bundle in the radial direction of the trunk and apex of D.barbatus at the age of was larger than that of the rest of the age classes The size of the vascular bundle in the radial direction tends to decrease from bottom to top In the tangential direction, the difference in vascular bundle size according to age and position on the trunk is not much 3.1.2.3 Effect of age, position on the stem on the area of vascular bundles Table 3.8 Vascular bundle area of Luong at different ages and position (mm2) Ages (years) Bottom 0,427 0,485 0,588 0,536 0,510 Middle 0,528 0,535 0,618 0,677 0,673 Top 0,550 0,548 0,684 0,819 0,711 Means 0,502 0,523 0,630 0,678 0,632 Through the results recorded in Table 3.8, it shows that the area of vascular bundles on the cross-section of the interstitium increased gradually from age to age 3, age 4, decreased at age 5, but the difference in vascular bundle area between grades According to the height position on the stem, at all age levels, the vascular bundle area increased gradually from base to top Position 11 The results shown in Table 3.12 show that the content of holocellulose fluctuates gradually from bottom to top at all ages in the range of 68,81-75,45% According to age, the fluctuation of holo-cellulose content increased gradually from the age of to and was stable at the age of 5, but the difference between the age groups was not much With that volatility of Streams is explained by: According to the position from bottom to top, from age to age 5, vascular bundle density and vascular bundle area increased from bottom to top Meanwhile, the content of holo-cellulose is mainly concentrated in the vascular bundles The results of the analysis of variance showed that the age and the position on the trunk were different to the holo-cellulose content Age did not affect the holo-cellulose content by postion on the trunk Age group and age 2, age group and age had no difference in holocellulose content 3.2.2 Effect of age and position on trunk on cellulose content Bảng 3.13 Cellulose content at different ages and positions on the trunk (%) Age (year) Bottom 53,01 51,82 53,42 53,68 53,94 Middle 54,99 53,84 54,70 54,51 55,10 Top 55,97 54,97 55,79 55,68 55,40 Means 54,66 53,54 54,64 54,62 54,82 The results shown in Table 3.13 show that the cellulose content fluctuates gradually from bottom to top at all ages in the range of 51,8255,79% According to age, the cellulose content at age and age was similar, increased at age and stabilized at age 5, the difference in cellulose content between age groups was not significant The results of the analysis of variance showed that the position on the trunk and the age had a difference on the cellulose content However, the variation between plant age and cellulose content was not significant Plant age did not affect the cellulose content by position on the trunk The age group and the age group had the largest difference in cellulose content, but there was no difference between the other age groups The position on the stem had a greater influence than the age of the plant on the cellulose content Position 12 3.2.3 Effect of age and trunk position on Lignin content Table 3.14 Lignin content of D.barbatus at age and position on the trunk, % Age (years) Bottom 28,48 30,39 31,00 30,07 29,61 Middle 26,23 28,43 27,76 27,54 27,65 Top 25,51 27,74 26,43 26,30 26,01 Means 26,74 28,86 28,40 27,97 27,76 Through the results in Table 3.14, we can see that, according to the position on the trunk: the ligin content at all age levels has a decreasing variation from the bottom to the top (25,51-30,40%) According to the age at the bottom of the tree, the Lignin content increased gradually from the age of to the age of 3, decreased at the age of and 5, in the trunk and tops increased from the age of to the age of and decreased at the age of to However, the change was not significant The results of analysis of variance showed that age and position on the trunk had differences on lignin content However, the difference between age and lignin content was not significant Age did not affect lignin content by position on the trunk The age group 1, and had a difference in lignin content, while for the age group 3, and 5, there was no difference 3.3 Effect age, position on the trunk on physical properties 3.3.1 Effect age, position on trunk on density Position Table 3.15 Density at 12% moisture of Thread at age grade and different positions on the trunk Position Bottom Middle Top Means Density when sample moisture 12% (g/cm3) Age Age Age Age Age 0,56 0,58 0,65 0,63 0,61 0,60 0,62 0,75 0,76 0,73 0,66 0,66 0,79 0,79 0,79 0,61 0,62 0,73 0,73 0,71 Table 3.16 Basic Density of Streams by age and position on the trunk Position Bottom Middle Top Means Age 0,42 0,44 0,47 0,45 Basic density (g/cm3) Age Age Age 0,45 0,51 0,51 0,48 0,59 0,61 0,50 0,62 0,63 0,48 0,57 0,58 Age 0,50 0,58 0,64 0,57 13 Table 3.15, 2.16 shows that, according to the position on the trunk: from the age of to the age of 5, the density increases from the bottom to the top According age, the density at age is the smallest and increases gradually to age 3, stabilizes to age and decreases at age Through analysis of variance, it was found that both density, age and posions on the trunk affected the difference in density Age affects density by postion in the trunk Position has a more pronounced effect on density than age The analysis results also show that, the dry density (at 12% moisture) between age group and age 2, age group and age 4, age group and is no difference The baseline density of age group 3, age and age did not differ The correlation between age, position on the trunk and dry density is shown by linear regression equation 3-4 ρ12 = 0,506 + 0,167X1+ 0,030X2 R2=55,3% (3-4) In there: ρ12- density at moisture 12%, g/cm ; X1- position, % trunk hieght; X2- age, years The correlation between age, position on trunk and dry density is shown by linear regression equation 3-5 ρy = 0,367 + 0,118X1 + 0,035X2 R2=61,6% (3-5) In there: ρy- basic density, g/cm ; X1- position, % trunk height; X2- age, years Correlation between vascular bundle area and density ρ12 = 0,244 + 0,735*S R2 = 88,4% (3-6) In there: ρ12- density at moisture 12%, g/cm3; S- vascular bundle area, mm2 Ρy = 0,140 + 0,660*S R2 = 86,6% (3-7) In there: ρy- basic density g/cm ; Correlation between vascular bundle density and density 12 = 0,397 + 0,069*Dv R2 = 59,6% (3-8) In there: ρ12- density at moisture 12%, g/cm3; DV- vascular bundle density, bundle/mm2 Correlation between fibrous cell wall thickness and density with age 12 = 0,44 + 0,03*WT R2 = 79,5% (3-9) Trong đó: ρ12- density at moisture 12%, g/cm3; WT- cell wall thickness, µm 14 3.3.2 Effect of age and position on the trunk on moisture content Bảng 3.17 Moisture at different age and positions on the trunk Moisture content (%) Age Age Age Age Age Bottom 163,53 149,70 112,18 113,51 123,13 Middle 149,80 145,14 94,87 94,71 100,23 Top 120,13 120,74 76,40 77,06 80,95 Means 144,87 138,53 94,48 95,09 101,45 Through the results in Table 3.17, we see: According to the age, the moisture content decreases from the age of to the age of and the age of to increases again According to location on the trunk, at all age levels moisture drops from bottom to top The results of the analysis of the effects between the subjects showed that the age of the tree and the position on the trunk affect the difference in moisture content Plant age affects the moisture difference by position on the trunk D barbatus Plant age affects moisture more clearly than position on the trunk Age group and had no difference in moisture content The correlation between age, position on the trunk and moisture content is shown by linear regression equation 3-11 W = 176,829 – 46,661X1 – 12,924X2 R2=69,9% (3-11) In there: W- subject moisture, %; X1- position, % trunk height ; X2- age, years Correlation between vascular bundle area and moisture W = 259,763 – 244,447*S R2 = 81,5% (3-12) In there: W- moisture, %; S- vascular bundle area, mm2 Correlation between fiber cell wall thickness and moisture (3-13) W  216,107  11,613 *WT R2 = 81,2% In there: W- moisture, %; WT- fibrous cell wall thickness, µm 3.3.3 Effect of age and position on shrinkage Vị trí Table 3.18 Radial shrinkage to 12% moisture in age and position Position Bottom Middle Top Means Radial shrinkage to moisture 12% (%) Age Age Age Age Age 9,55 8,62 6,56 5,47 4,99 11,32 9,43 6,85 5,72 5,69 12,05 10,37 7,19 6,42 6,15 10,93 9,48 6,86 5,87 5,61 15 Table 3.19 Radial shrinkage to 0% moisture at age and position on the trunk Position Bottom Middle Top Means Radial shrinkage to moisture 0% (%) Age Age Age Age Age 11,27 10,51 8,30 7,09 6,77 13,58 11,48 8,81 7,50 7,38 14,76 12,37 9,14 8,26 7,85 13,15 11,45 8,75 7,62 7,34 Table 3.20 Tangential shrinkage to 12% moisture at tree age and location Position Bottom Middle Top Means Tangential shrinkage to moisture 12% (%) Age Age Age Age Age 8,77 6,23 5,62 4,47 4,37 8,54 6,44 5,87 4,49 4,38 9,19 7,17 6,40 4,97 4,83 8,83 6,61 5,96 4,65 4,53 Table 3.21 Tangential shrinkage to 0% moisture at tree age and location Tangential shrinkage to moisture 0% (%) Age Age Age Age Age Bottom 10,93 8,17 7,55 6,49 6,37 Middle 10,52 8,31 7,66 6,51 6,39 Top 11,22 9,13 8,18 6,77 6,63 Means 10,89 8,54 7,80 6,59 6,46 From the results in Table 3.18 to Table 3.21, it shows that, according to age, when the age increases from age to age 5, the radial and tangential shrinkage at positions tends to decrease However, the largest variation was from age to age 3, and from age to age the difference was not much According to position, shrinkage increases gradually from bottom to top The results of examining the influence of factors show that: The position in the trunk has a difference to the radial and tangential shrinkage Trunk position has a more pronounced effect on radial and tangential shrinkage relative to age Age group and age had no difference in shrinkage The results of the linear regression analysis between shrinkage and age and position on the trunk are shown by equation 3-14 to 3-17 𝐵𝑤𝑥𝑡 = 11,159 + 1,734𝑋1 − 1,426𝑋2 R2 = 78,1% (3-14) 𝐵𝑤𝑡𝑡 = 8,890 + 0,763𝑋1 − 1,054𝑋2 R = 73,2% (3-15) 𝐵𝑚𝑎𝑥𝑥𝑡 = 13,256 + 2,097𝑋1 − 1,548𝑋2 R = 80,0% (3-16) 𝐵𝑚𝑎𝑥𝑡𝑡 = 10,979 + 0,592𝑋1 − 1,075𝑋2 R2 = 72,7% (3-17) Position 16 In there: Bwxt, Bwtt- are the radial, tangential shrinkage when D barbatus moisture 12%, %; Bmaxxt, Bmaxtt- are the maximum radial and tangential shrinkage, %; X1- position, % trunk height; X2 -age, years 3.4 Effect of age and position on the mechanical properties 3.4.1 Effect of age, position on the trunk on the compressive strength along the grain Table 3.22 Longitudinal compressive strength at age and positions on the trunk Longitudinal compressive strength (MPa) Age Age Age Age Age Bottom 35,00 35,20 46,55 42,27 42,54 Middle 40,81 41,22 47,10 52,49 50,63 Top 42,43 43,10 48,45 59,70 52,14 Means 39,34 39,88 47,36 51,69 48,42 From the experimental results in Table 3.22, it can be seen that, (1) According to the position on the trunk, from the age of to the age of 5, the compressive strength along the grain fluctuates gradually from bottom to top, ranging from 35,00 MPa đến 59,70 MPa (2) With age, the compressive strength along the grain increased from age to age or age 4, decreased at age 5, ranging from 39,42 MPa đến 51,49 MPa Through analysis of variance, it was found that the age and the position on the trunk affected the difference in compressive strength along the grain The age has an effect on the compressive strength along the grain according to the position Age has a more pronounced effect on compressive strength along the grain than position Age group: age group and age 2, age group and age have no difference The results of the linear regression analysis are shown through the regression equation 3-18  = 30,788 + 11,082𝑋1 + 3,033𝑋2 R2 = 56,2% (3-18) In there: - longitudinal compressive strength, MPa; X1- position, % trunk height; X2- age, years Correlation between vascular bundle area and longitudinal compressive strength 𝜎12 = 63,0757𝑆 + 7,9024 R2 = 95,2% (3-19) In there: 𝜎12 - compressive strength along the grain at sample moisture 12%, MPa; S- vascular bundle area, mm2 Position 17 Correlation between density and longitudinal compressive strength 𝜎12 = 74,707 ∗ ρ − 5,489 R2 = 81,6% (3-20) In there: 𝜎12- compressive strength along the grain at sample moisture 12%, MPa; ρ- density at moisture 12%, g/cm3 Correlation between fiber cell wall thickness and longitudinal fiber compressive strength with age 𝜎12 = 2,661 ∗ Wt + 22,090 R2 = 88,3% (3-21) In there: 𝜎12- compressive strength along the grain at sample moisture 12%, MPa; WT- fiber cell wall thickness, µm 3.4.2 Effect of age, position on static bending strength (MOR) Table 3.23 Static bending strength at different ages and positions in the trunk MOR (MPa) Age Age Age Age Age Bottom 72,72 83,36 98,60 87,67 87,23 Middle 86,28 88,41 103,10 115,87 115,23 Top 87,46 87,88 115,21 129,30 119,00 Mean 82,43 86,57 105,61 111,75 107,43 Table 3.23 shows that, (1) According to the height of the trunk: from the age of to the age of 5, the MOR fluctuates gradually from bottom to top, varies from 72,72-129,30 MPa (2) According to age, the MOR increased from age to age 3, stabilized at age 4, and decreased to age 5, fluctuated between 82,43-111,15 MPa The results of analysis of variance showed that the age and position had a difference to the MOR Age also affects the MOR Position has a more pronounced effect on MOR than age There was no difference between age group and age in MOR of Stream The results of the linear regression analysis are shown in Equation 3-22 𝑀𝑂𝑅 = 62,494 + 27,050𝑋1 + 7,521𝑋2 R2 = 58,9% (3-22) Trong đó: X1- position, % trunk height; X2- age, years Correlation between vascular bundle area and MOR 𝑀𝑂𝑅 = 158,892 ∗ 𝑆 + 4,266 R2 = 97,3% (3-23) In there: 𝑀𝑂𝑅- Static bending strength when object moisture 12%, MPa S- vascular bundle area, mm2 Correlation between density and MOR 𝑀𝑂𝑅 = 194,691𝜌 − 33,8877 R2 = 89,2% (3-24) In there: 𝑀𝑂𝑅- Static bending strength when object moisture 12%, MPa ρ- density at moisture 12%, mm Position 18 Correlation between fiber cell wall thickness and MOR by age 𝑀𝑂𝑅12 = 6,5755𝑊𝑡 + 41,1290 R2 = 91,3% (3-25) In there: 𝑀𝑂𝑅12 - Static bending strength when object moisture 12%, MPa; WT- fiber cell wall thickness with age, µm 3.4.3 Effect age, position on the trunk modulus of static bending Bảng 3.24 Static bending modulus of Luong at age and tree positions MOE (MPa) Age Age Age Age Age Bottom 7006,4 7281,6 8335,4 8011,2 7972,8 Middle 9645,1 9640,0 9843,6 10895,1 11056,9 Top 10381,2 12032,8 12145,1 12720,5 12339,7 Mean 9073,4 9651,4 10105,0 10629,5 10500,2 From the results in Table 3.24, it is shown that, (1) According to the position of the trunk height from to years old, MOE increases gradually from bottom to top (2) For age, MOE gradually increased from age to age and stabilized at age Specifically, at position, the MOE bottom position increased from age to age 3, decreased at age and 5; at the trunk and apical positions, we can see that the MOE increases from age to age and Through analysis of variance, it was shown that there is a difference in the age and position to the MOE, and the age affects the MOE according to the position on the trunk The location affects the MOE more clearly than the age, the group of subjects showed that the age group of age group and age 2, age group and age 3, age group and age had no difference in MOE The results of linear regression analysis between MOE with age and position on the trunk are shown through regression equation 3-26 MOE = 6195,767 + 5232,462X1 + 380,910X2 R2=59,9 (3-26) In there: MOE- static bending modulus, MPa X1- position, % trunk height; X2- age, years Correlation between bundle density and MOE of D barbatus 𝑀𝑂𝐸 = 2014,702𝐷𝑣 + 1721,754 R2 = 90,1% (3-27) Dv- vascular bundle density of Thread, bundle/mm2 Correlation between vascular bundle area and MOE 𝑀𝑂𝐸 = 15168,171𝑆 + 959,101 R2 = 67,2% (3-28) Where: S- vascular bundle area, mm Correlation between fiber cell wall thickness and the MOE by age 𝑀𝑂𝐸 = 330,886𝑊𝑡 + 7067,441 R2 = 99,6% (3-29) Position 19 Where: WT- fiber cell wall thickness, µm Correlation between density and MOE 𝑀𝑂𝐸 = 20042,0681𝜌 − 3673,4443 R2 = 71,6% Where: 𝜌- Density when moisture 12%, g/cm3 Correlation between cellulose content and MOE 𝑀𝑂𝐸 = 1408,767𝑋 − 66760,108 R2 = 73,2% Where: X- cellulose content, % 3.4.4 Effect of age and position on shear strength (3-30) (3-31) Table 3.25 Longitudinal shear strength at different ages and positions Longitudinal shear strength (MPa) Age Age Age Age Age Bottom 4,85 5,45 6,10 6,41 5,89 Middle 5,86 5,66 7,11 6,84 6,00 Top 6,10 6,00 7,10 6,74 6,84 Mean 5,59 5,71 6,76 6,66 6,24 From the experimental results shown in Table 3.25, it can be seen that, at age to and age 5, the longitudinal shear strength of D barbatus fluctuates from bottom to top, but the difference is not large Age and age longitudinal shear strength increased from bottom to middle and stabilized to top For age, the longitudinal fiber shear strength at the bottom position increased from age to age 4, decreased at age 5; At the trunk and apical positions, it was found that the longitudinal shear strength increased from age to age and decreased at age and Through analysis of variance, it was shown that age and position had a difference in the shear strength along the grain of D barbatus Plant age has an effect on shear strength according to position, but the correlation is low Age group: age group and age 2, age group and age are not different Correlation between vascular bundle area and longitudinal shear strength 𝜏 = 4,881𝑆 + 3,298 R2 = 62,1% (3-32) Where: 𝜏- shear strength along grain when moisture 12%, MPa; S- vascular bundle area, mm2 Correlation between density and longitudinal shear strengt 𝜏 = 7,0204𝜌 + 1,4228 R2 = 77,9% (3-33) Where: 𝜏- shear strength along grain when moisture 12%, MPa; ρ- density at moisture 12%, g/cm3 Position 20 3.5 Orientation for exploitation and use for each age and position 3.5.1 Orientation of mining age Based on the fluctuation of the properties of D barbatus with the age, it shows that the properties have the best value in terms of mechanics, the dimensional stability of the D barbatus at the age of and From that, it shows that, for the purpose of using for industrial production, using D barbatus in load-bearing products, the exploitation and use of D barbatus that the research topic is most suitable for is at the age of and 3.5.2 User Orientation To conduct an analysis of the usage orientation of D barbatus by position on the trunk, it is necessary to delve into the two main factors that affect the usability of Streams in practice today The age of the tree and the position on the trunk are the factors that clearly affect the mechanical strength of the D barbatus In the same age level: The position on the trunk affects the tree diameter and wall thickness of the D barbatus These are factors that will greatly influence the choice of location for different uses of D barbatus 3.5.2.1 Use the whole tree directly The D barbatus can be used for house construction Therefore, it is possible to use the whole body or use the top with high bearing capacity and it is appropriate to use D barbatus at the age of and for this area Especially, the top of D barbatus has high mechanical properties, but the diameter and wall thickness are thin, which can not be used for products requiring large diameter and wall thickness, so it can be utilized and prioritized for use in the field 3.5.2.2 Utilization of D barbatus through industrial processing Based on product size, plank structure, material requirements for each type of board and thickness of positions on trunk We aim to use D barbatus with suitable positions for boards: (1) Using bamboo in the form of peeled boards and thin spokes Bamboo veneer: The D barbatus used at the bottom and middle position is suitable, for the top with a small diameter and wall thickness, it is not suitable for peeled boards Plybamboo: The bottom and middle will be divided into parts The base part at 1.5 m height with large wall thickness will be used as the innermost layer The second and third parts will be used as the face layer of the board, the fourth part with the thinnest thickness will be used as the innermost layer like the first part but erect the bar 21 (2) Use bamboo stick form Bamboo flooring - Single-layer bamboo flooring: Suitable for the position of this type of board, it is necessary to use D barbatus at the base and trunk position (wall thickness is 7.17-15.76 mm) Wall thickness D barbatus at the top is not suitable for the manufacture of this type of flooring - 3-layer bamboo flooring with a lying middle layer: Compare with the product and material requirements for this board it shows, Therefore, the D barbatus tree used for the purpose of creating this type of flooring is the position of the bottom and the middle, the wall thickness is in the range of 7,17-15,76 mm - 3-layer bamboo board, with a vertical middle layer: The D barbatus can be used for this type of board in any position The bottom and middle positions have a bamboo wall thickness greater than 7mm, suitable for the production of the top and bottom layers of boards The top position with wall thickness less than mm can be used for the middle layer to perform vertical grafting to create products with required product sizes of 15 mm and 18 mm Bamboo – wood flooring: The product that creates the top and bottom layers from the top of the D barbatus gives us better stiffness and surface density because the mechanical properties of the top of the D barbatus are higher than the middle and the bottom (3) Using bamboo in the form of chips and fibers Using the top for this type of board results in a product with a higher density However, it is necessary to pay attention to increasing the taperedness of the fibers in the process of making the chips and fibers If using the same part close to the bottom and top for this product, it will affect the quality of the product (4) Using bamboo to make composite materials Bamboo block board: The wall size is not required, but high mechanical strength is required Therefore, D barbatus will choose 3-4 years old to create this product and can use the entire trunk for the block-grafted bamboo product Composite Bamboo – Wood: The position of the trunk and base of D barbatus is suitable for the production of bamboo-wood composite boards with plybamboo in the middle and arranged bamboo walls For boards with a vertical middle layer and boards with an outer bamboo layer, the top of the D barbatus can be used (5) Producing household goods and handicrafts 22 For this product, it is possible to take advantage of the position of the D barbatus with a small diameter, a thin wall thickness like the top is suitable CONCLUSIONS AND RECOMMENDATIONS Conclusion On the basis of the research contents of the thesis on the influence of age and trunk height position on some structures and properties of D barbatus From the research results of the thesis, we make the following main conclusions: (1) Influence of age and position on the trunk on some structures of D barbatus - Age clearly affects some structures: Wall thickness, increasing from age to age 4, stabilizing at age (4,18-7,34 µm) and fiber length increased from age to age 4, decreased at age (2,60-3,65 mm) Age does not significantly affect some structures: Wall thickness, increases from age to age (8,31-10,03 mm), bundle density (3,98-4,23 bundle/mm2) and vascular bundle area (0,502-0,680 mm2) increase from age to age 3, decrease at age and Plant age did not affect fiber diameter (17,54-18,11 µm) and vascular bundle size (0,38-0,39 mm) - According to position on the trunk, some structures increase from bottom to top: Vascular bundle density (3,05-5,13 bó/mm2), vascular bundle area (0,50-0,66 mm2), fibers length of D barbatus age to age (3,06-3,31 mm) Some structures decrease from bottom to top: wall thickness (5,17-14,92 mm), Fibrous cell wall thickness (4,89-7,13 µm), fibers length (3,09-3,50) Fiber diameter is not significantly affected by age (17,40-18,41 µm) - Position clearly affects tree age on the structure of D barbatus (2) Effect of age and position on the trunk on the chemical composition of D barbatus - Age did not significantly affect holo-cellulose and lignin content: Holo-cellulose content, increased from to years old, stable at years old (70,07-73,59%) and lignin content increased from age to age 2, decreased at age 3, stabilized at age 4, age (26,74-28,85%) Age did not affect the cellulose content of Luong (53,53-54,81%) - The position on the stem clearly affects the chemical composition of D barbatus: The holo-cellulose content increases from bottom to top (70,08-73,69%), cellulose content increased from root to tip (51,8255,97%) and lignin content decreased from root to tip (25,51-31,00%) 23 - The position has a more obvious influence than the age on the chemical composition (3) Effect of age, position on the trunk on some physical properties of D barbatus - According to age: Density increases from age to age 3, stable until age (y: 0,45-0,58 g/cm3, 12: 0,61-0,73 g/cm3) Moisture decreases from age to age 3, stabilizes at age 4, and increases at age (94,48-144,87%) Shrinkage decreases from age to age 4, stabilizing at age (XT: 7,34-13,15%, TT: 6,46-10,89%) - By position on the trunk: Density increases from bottom to top (y: 0,48-0,58 g/cm3, 12: 0,61-0,74 g/cm3), Moisture decreases gradually from bottom to top (132,41-94,71%), shrinkage increases from bottom to top (XT: 8,78-10,42%, TT: 7,90-8,34%) - Fiber cell wall thickness, vascular bundle area are strongly correlated with the density and moisture content of the D barbatus: The thickness of the fiber cell wall, the increase of the vascular bundle area, the increase in density, the decrease in moisture content and vice versa (4) Effect of age, position on the trunk on some mechanical properties of D barbatus - According to tree age: Variation properties increase gradually from age to age and age 4, decrease at age 5, compress along the grain (39,33-51,69 MPa), Static bending strength (82,43-111,15 MPa), static bending modulus (9073,4-10629,5 MPa) and longitudinal shear strength (5,59-6,76 MPa) - According to the position on the trunk: The properties fluctuate from bottom to top, longitudinal compression (35,02-52,14 MPa), Static bending strength (72,43-129,00 MPa), static bending modulus (7006,412720,5 MPa) and longitudinal shear strength (4,85-7,11 MPa) - Vascular bundle area, fiber cell wall thickness, and density increase leading to an increase in longitudinal compression, static bending strength, and static bending modulus and vice versa Vascular bundle area, increased density leads to increased longitudinal shear strength and vice versa The density of vascular bundles, the increased cellulose content leads to an increase in the elastic modulus of static bending and vice versa (5) Harvest age orientation and use by positon on the trunk - In order to effectively use D barbatus for product creation purposes in industrial production, high mechanical strength and stable 24 physical properties are required, so the age of exploitation is suitable at ages and - Use orientation according to the position on the trunk of the D barbatus Bottom and middle of D barbatus: Used in construction when using whole trees (pillars, trusses ), used for production of plybamboo, production of bamboo - wood composite boards, production of block bamboo, production of verneer boards Top of D barbatus: Used in the construction of houses, tents as trusses, rafters on the roof, as construction piles In the industry, it is used to produce bamboo floorboards with the middle layer of vertical joints, to produce bamboo - wood floors in combination, bamboo composite board - a combination of wood with a bamboo layer in the middle, and bamboo - wood with bamboo as the surface layer, production of chipboard, bamboo fiber board, bent furniture, handicrafts, and household appliances 2 Recommendations On the basis of the research and limitations of the thesis, we have some recommendations as follows: (1) It is necessary to study changes in chemical composition and properties of D barbatus in different sites On that basis, there are comparisons and assessments of the site factors affecting the structure and properties of the D barbatus (2) It is necessary to study the effect of harvesting season on the chemical composition, physical properties, mechanical properties and biological properties of D barbatus (3) It is necessary to study changes in structure, chemical composition and properties of D barbatus at bamboo nodes at different age levels and positions on the trunk (4) It is necessary to study the effect of tree age and position on the trunk of D barbatus on the processing ability (cutting, gluing, painting ), from there, there are orientations for more reasonable processing methods according to age and position on the tree trunk (5) Studies on the influence of age and position on the trunk on the natural durability of D barbatus are needed 25 LIST OF PUBLICIZED ARTICLES, SCIENTIFIC WORKS RELATED TO THE THESIS Nguyen Viet Hung, Pham Van Chuong, Nguyen Thi Tuyen (2021), Study on the correlation between the structure and properties of Dendrocalamus barbatus Journal of the Austrian Society of Agricultural Economics (JASAE) ISSN: 18158129 E-ISSN: 18151027 17 (01) (Scopus, Q4) Nguyen Viet Hung, Pham Van Chuong (2019), Study on the effect of tree age and position on the trunk on physical properties of Bamboo (Dendrocalamus barbatus Hsueh et D.Z.Li), Journal of Forestry Science and Technology, No (2019), PP 95-101 Nguyen Viet Hung, Pham Van Chuong (2019), The effects of age and height position on the chemical of Bamboo (Dendrocalamus barbatus Hsueh et D.Z.Li) in Thanh Hoa, TNU Journal of Science and Technology, 202 (09), pp 53-58 Nguyen Viet Hung, Pham Van Chuong (2019), The effects of tree age, height position on the trunk to the structures of Bamboo (Dendrocalamus barbatus Hsueh et D.Z.Li) in Thanh Hoa, Science and technology Journal of Agriculture and Rural Development (Theme of sustainable agricultural development in the northern mountainous midland region), Month 11-2019, pp 142-149 Nguyen Viet Hung, Pham Van Chuong (2018), The effects of age and site on plants on the mechanical properties of Bamboo (Dendrocalamus barbatus Hsueh et D.Z.Li), Journal of Forestry Science and Technology, No (2018), pp 123-131 ... trunk on physical properties of Bamboo (Dendrocalamus barbatus Hsueh et D.Z .Li), Journal of Forestry Science and Technology, No (2019), PP 95-101 Nguyen Viet Hung, Pham Van Chuong (2019), The effects... position on the chemical of Bamboo (Dendrocalamus barbatus Hsueh et D.Z .Li) in Thanh Hoa, TNU Journal of Science and Technology, 202 (09), pp 53-58 Nguyen Viet Hung, Pham Van Chuong (2019), The... 11-2019, pp 142-149 Nguyen Viet Hung, Pham Van Chuong (2018), The effects of age and site on plants on the mechanical properties of Bamboo (Dendrocalamus barbatus Hsueh et D.Z .Li), Journal of Forestry