| The depletion of fossil fuel and the emerging environmental issues world-wide has promoted the utilizations of renewable natural resources and the green and environmental friendly products.Bamboo has played a vital role in the manufacturing of forest products because of its characteristics such as fast growth,high yield,and excellent performance.In order to stratify the demands in bamboo on industrial production,people begin to pay more and more attention on silviculture practices to improve the yield.However,the bamboo produced from different silviculture practices especially for industrial purpose still remains unknown.The properties of the harvested bamboo timbers should be evaluated prior to its use.Therefore,it is essential to perform the bamboo timber properties analysis as bridge to connect the silviculture practices and its end utilization.And such an eco-chain of bamboo will not only benefit the bamboo product industry but also promote the economic and social profits to the local residents.In this study,N affinis bamboo was selected and its applicability to industrial use was first elucidated,followed by the study of its growth pattern of culm morphologies and timber properties.The variation in properties between four research sites was also studied.Based on the aforementioned analysis,a "3414"fertilization experiment was set up for investigating the influence of fertilizations on the properties of bamboo.With fertilized for one year,bamboo culms with different ages were harvested and the anatomical,physical,and mechanical properties were determined.The main results and contribution of this research were as follows:1.The culm height and breast height diameter of N affinis in Sichuan province is 8-14m and 35-70cm,respectively.The N affinis culm wall was composted of parenchyma cells and vascular bundles.The vascular bundle type of N affinis is "Open" type,which is consisted of fiber brands and vessels.N affinis bamboo fibers were long,thicken cells with small cavity,pits on the fiber wall were.Compared with Dendrocalamus farinosus,Dendrocalamus latiflorus,Phyllostachys edulis,and Bambusa pervariabilis×Dendrocalamopsis Daii,N affinis had the thinnest culm wall,while N affinis had the minimum initial moisture content(58%),which was merely 1/3 and 1/2 of that for Dendrocalamus farinosus and Bambusa pervariabilis×Dendrocalamopsis Daii,respectively.The fiber length for N affinis was longer than that for Phyllostachys edulis,while they had similar value in fiber cell wall thickness.The basic density,compressive strength,and shear strength for N affinis was 0.69g/cm3,66.49 MPa,12.86 MPa,respectively,the basic density was the largest among the five bamboo species.The fiber morphology testified that N affinis was an excellent resources for pulping.The lower initial moisture content,longer internode,high density,stable dimension,and strong mechanical strength made N affinis an appropriate material for engineering and constructions.2.The culm height growth pattern of N affinis fits well with the pattern ofslow-fast-slow.During the fast growing stage,the average growing rate of culm height was 26.3cm/day.The regression relationship between the average culm height,nodes number,and internode length of N affinis and days during the height growth period were exponential function,power function,and exponential function,respectively.At both the height growth and properties maturation stages,with increasing in nodes number starting from the bottom of the culm,the internode length first increased and then gradually decreased.A good cubic function regression between internode length and nodes number were found.The change in internode diameter with respect to node number was similar to that of internode length.The culm wall thickness showed a decreasing trend with increasing the node number,and significant power function regression was found between culm wall thickness and node number.The growing period and sites had no significant influence on the growing patterns of culm diameter and culm wall thicknesss with culm,which was just the reflection of gene characteristics of N affinis bamboo.3.After growing 40-55 days,fiber cells differentiated from parenchymas begin to thicken,and existed significance in cell wall thickness with parenchymas.There are three elongation growth stages for N affinis bamboo fiber,i.e.,the fast growth stage,the slow growth period,and the aging stage,which took place in the culm height growth period,the fresh bamboo period,and the maturing period,respectively.During the fast growing period,the fiber elongated from 1.60mm to 2.50 mm showing a linear growth pattern.The growth of fiber length was well consisted with that of the internode length.During the culm height growth period,the fiber wall gradually thickened,and then the fiber wall thickness dramatically increased in the fresh bamboo period and became stable in the maturing stage.From the end of the culm height growth period to the end of the fresh bamboo period,thefiber wall cell increased from 4.68 to 9.59 μm.The growth pattern of the fiber cell lumen was opposite to that of the cell wall.The fiber length and wall thickness showed no specific growth pattern with respect bamboo culm ages during the properties maturing period.4.The cell proportion showed no specific pattern with respect to the growing period,and the variation was insignificant.From the beginning of the culm height growth period to the maturing period,the basic density gradually increased,and showed a significant quadratic function regression with the growing period.During the maturing period,the volume shrinkage showed a decreasing trend,and a significant quadratic function regression was found between the volume shrinkage and the bamboo age.Similar to the relationship between bamboo culm age and basic density,the mechanical including compressive strength and shear strength increased with increasing bamboo culm age.From the point view of construction purpose,the harvesting age for N affinis bamboo is the fourth year.The correlations between fiber length and intemode length,fiber wall thickness and basic density,basic density and mechanical strength were found significant.The correlations between bamboo properties were in accordance with the growth of the culm morphologies.5.Negative relationship between fiber proportion and rainfall,temperature sunshine duration of the cell differentiating period was found,while the parenchyma proportion was positively related with these climate factors.The vessel proportions was positively related with rainfall and sunshine duration and negatively related with temperature.A significantly positive relationship between rainfall in the culm height growth period and fiber length was found,while the fiber length was negatively related with temperature and sunshine duration.A significantly negative relationship between shear strength and annual average temperature and a significantly positive relationship between volume shrinkage and total sunshine duration were found.The maximum water holding captivity,minimum water holding captivity,and total porosity were positively related with fiber length,basic density,mechanical strength,and were negatively related with fiber cell wall thickness,lumen,width,and volume shrinkage.A weak relationship between fiber length and total nitrogen content was found,and the relationship between available phosphorus and available potassium was negative.The mechanical properties were positively related with total nitrogen and were negatively related with available phosphorus.6.The adequate rainfall,proper temperature and sunshine duration will promote the elongation growth of N affinis fiber,while plenty rainfall,low temperature,and short sunshine duration will go against the thickening of fiber wall.The appreciated climate environment for sites in Yaan was proper for the planting and cultivation of pulping bamboo plantations.The preferable water holding captivity and permeability and low pH of the soil was suitable for both the pulping and construction bamboo plantations.Yaan and Meishan were confirmed to be appreciated regions for cultivating both the pulping and construction plantations due to their proper soil properties.7.All the thirteen fertilization practices could increase the parenchyma proportions and volume shrinkage,while decrese the fiber lengh,fiber proportion,vesell proportion,and basic density.No specific variation patters of the other bamboo properties index such as fiber wall thickness,fiber lumen diameter,and mechanical properties with respect to the changes of fertilizer element and its level was observed.Meanwhile,the culm ages alsohad effect on the bamboo properties response to fertilization practices.The effect of fertilization on parenchyma proportion,fiber proportion,and fiber length of the one-year-old bamboo culm was larger than those of the two and three-year-old bamboo culms,while the effect on fiber lumen,wall thickness,basic density,volume shrinkage,and mechanical strength of the two and three-year-old bamboo culms was larger than that of the one-year-old bamboo culms.8.The variation in parenchyma proportion,fiber proportion,vessel proportion,fiber length,fiber lumen diameter,fiber wall thickness induced by fertilization was smaller than that induced by culm individulas and portions,while the variation in basic density,volume shrinkage,and mechanical properties induced by fertilization was larger than that induced by culm individuals and portions.This result indicated that fertilization had difference influence pattern on various bamboo properties.Though,difference in bamboo properties among different fertilization practices and bamboo culm ages was observed,the variation pattern of bamboo properties with respect to bamboo culm age was not affected by fertilization indicating that the growth patterns of N affinis bamboo properties was the reflection of its gene characteristics.9.The changes in fertilizer type and amount applied into the soil resulted in different effects on the properties of N affinis with different culm ages.The application of nitrogen and phosphorus had negative effect on most of the properties of N affinis bamboo,and the effect of each fertilizer on the properties of one-year-old bamboo was larger than those of the two and three-year old bamboo culms.The potassium fertilizer had no obvious effect on the properties of N affinis bamboo.In order to avoid the significant effect of fertilizations on the properties of N affinis for pulping purpose,the application of fertilizers should be performed in the period from January to April.The amount of nitrogen and phosphorus application should be lower than 0.3kg/clump/year and 0.15kg/clump/year,respectively.The amount of potassium fertilizer can be dependent on the requirement of the bamboo culm growth.To be conclusion,N affinis could be used as a potential raw material for pulping and the manufacturing of biological based materials.The variation and or growths patterns of bamboo properties were the reflection of its gene characteristics.For the purpose of pulping,climatic factors such as rain,temperature,.and sunshine duration should be carefully considered.The soil conditions for Yaan and Meishan verified that areas in Southwest Sichuan were ideal regions for the planting of both pulping and structural raw materials.The application of fertilizer N and P should be properly controlled,and the fertilization practice should be performed between January to April.Effect of more fertilization practices such as fertilization pattern,the application of dedicated bamboo fertilizer on the influence of bamboo properties should be under considercation in the near future research. |
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