Introduction
Many genera and species of termites have been brought from other countries inside shipments of wood and lumber, making them endemic permanent inhabitants [
1]. According on its genealogy, termite colonies live in enclosed nests that are either subterranean (underground nests), arboreal (nests associated with trees), or epigeal (soil mounds) as referred by Li and Greening [
2]. The effect of three main ecological factors; vegetation, rainfall and landform on the distribution and abundance of five termite genera commonly found in Saudi Arabia has been studied. Five genera include Anacanthotermes, Psammotermes, Microcerotermes, Amitermes and microtermes. With the exception of termites of the genus Microtermes, those of the remaining 4 genera seem to have almost similar requirements. They prefer open scrubs (regions containing herbs and shrubs), moderate mean annual rainfall (ranging between 50 and 150ram), and are more abundant in plateau areas. On the contrary, Microtermes has 50 % of its sampling sites located in open scrubs and about 40 % in large trees/grass areas. It prefers relatively higher mean annual rainfall (ranging between 250 and 500 mm), and are more abundant in plains [
3,
4].
Numerous termite species, both native (endemic) and some introduced cosmopolitan species, are found in rural, urban, and suburban habitats [
5]. The subterranean termites were classified ecologically into four groups, namely drywood termites, dampwood termites, and formosan termites [
6,
7].
Microtermes najdensis, a small underground termite of the Termitidae family, was discovered at Hada Al-Sham [
7,
8]. In addition, termites belonging to the Kaloter-mitidae, Hodotermitidae, Rhinotermitidae, and Termitidae families were discovered in Saudi Arabia at all. The first three of them are lesser termite families, whereas the fourth one is a high developed family termed as Termitidae [
8]. The annual losses due to their heavy infestations in human life have reached a great level leading to apply prophylactic and preventive methods [8-12].
Nests provide a tight enclosure that protects the colony from predators including but not limited to ants, lizards and/or birds [
13]. Termite nests are among the most diverse and complicated structures among the vast array of those constructed by animals [
13]. Their intricate architectures and how termites use them have fascinated mankind for centuries, whether as part of local agricultural practice, a simple landscape feature, an inspiration for societal collective building, or a scientific study object on its own [
13]. However, their nests are less well studied than those of many ants, social wasps, and social bees, particularly honey bees and stingless bees, because termites that create mounds or other prominent structures are of modest ecological relevance [
13].
It was reported by Johst [
13] and Turner and Soar [
14] that termites’ nest structures have been used as exemplars of bioinspired designs, in buildings, for air-conditioning control (adjusting internal temperature and relative humidity), balancing each of energy and gas- exchanging between inner and outer nest’ system. Termite nests’ constructions are often quite species-dependent meaning that different species in the same habitat can create nests of varying firmness. The chemical structure of their saliva and faecal material, as well as the clay/sand ratio, influence nest solidity [
13].
Wood is constituted structurally from polysaccharides (cellulose and hemicelluloses) and lignin [
15]. Cellulose has a homopolymeric structure which composed of [1→4]-β-D-glucopyranose monomers, understanding its conformation and the 3D-packing manner in microfibrils is still remains largely a mystery [16-18]. A cellulosic chain is made up of repeating cellobiose units, which provide a variety of structures, reactions, and uses, hence enhancing its significance [
19]. Approximately 10.000 glucopyranose subunits (monomers) or more can be found in a single cellulose chain [
20]. Hydrogen bonds along with Van der Waals forces help the neighboring chains stick together. Bio-hydrolyzing cellulose needs three cellulolytic enzymes at least to be synergized: endo-β-[1, 4]-glucanase which is able to hydrolyze β-1, 4-bonds of cellulose chains, exo-β-[1, 4]-cellobiohydrolase that librates cellobiose from the cellulose’ s non-reducing ends, and β-glucosidase that hydrolyses cellobiose or longer chains releasing glucose monomers [
21,
22].
Beside cellulose, hemicelluloses are the second division of polysaccharides found in plant cell walls. It is made up of simple sugars’ monomers, namely glucose, galactose, mannose, xylose, arabinose, and glucuronic acid. It has equatorial skeleton with β- [1→4]-linkages [
15]. Hemicelluloses are found as different compounds spreading at all plants such as xylans, glucomannans, xyloglucans, mannans as well as beta-[1→3, 1→4]-glucans which are confined essentially to Poales [
15]. Due to species and cell types, the structure of hemicellulose varies greatly in nature. Hemicelluloses' role in fortifying the cell wall is achieved by its interaction with other biopolymers. It was indicated that glycosyltransferases present at the Golgi membranes synthesize hemicelluloses [
23]. In the primary walls of dicotyledons, xyloglucan predominates, and it significantly helps cellulosic microfibrils to be cross-linked together [
24]. Moreover, pectins are a kind of heterogeneous polysaccharides that contain 1→4-linked α-D-galactosyluronic acid. From primary plant cell walls, homogalacturonan [HG], rhamnogalacturonan-I, and substituted galacturonans are three detected forms of pectin.
A phenolic polymer called lignin accounts for 15–36% of the biomass in wood. It performs a number of activities in plants' extracellular matrix [
25]. It consists of phenylpropane monomers cross-linked by various chemical linkages is what gives lignin its complexity.
For the termite diets, it was reported that many xylophagous insects have symbiotic bacteria and/or protozoa in their digestive systems that help break down cellulose, but some of them, like the termite from the Termitidae family, have their own cellulose enzyme. Additionally, termites depend on a mutualistic gut microbiota to mediate the fermentation and hydrolysis of lignocellulose, which produces acetate, hydrogen (H
2), and methane as well as improves carbon and nitrogen cycles and modifies soil structures [
2].
The main source of food for termites is wood, grass, leaves, humus, animal excrement from herbivores, and plant-based goods including paper, cardboard, and cotton. The numerous cellulosic-based foods from other dead or living plants are consumed by subterranean termites [2,26-28]. It makes sense that termites require three things to survive: food, water, and air. For nutrition, it was reported by Ulyshen [
29] that some termites’ groups depends on nutrition produced from decayed wood arisen by numerous developing fungi. The amazing and extraordinary behavior of these termites’ species is their transferring fungus' spores by unique structures on their bodies called mycangia [
29]. After that, they spread these spores within their nests’ floor in order the spores will be able to continue their growth cycle. This process can be viewed as a farming practice [
30,
31].
For water needed for the termites within their nests, both dry wood- and damp wood-termites do not depend on the ground water but get water it from their food sources [dry wood] or from damp, dead, rotten wood, respectively [
32]. Contrarily, subterranean termites are compelled to contact with soil to fulfill their thirst for water and moisture. As a result, subterranean termites have evolved into the most costly and damaging to human property, woodwork, stored goods, buildings, and wooden infrastructure [
11].
It has been extensively recorded how termites forage or swarm to disperse in search of food or to build new nests and colonies. It is thought that some procedural swarming activity, which can occur indoors or outside, gives homeowners an early warning for early infestation by this insect [33-42].
Due to their stealthy eating habits, subterranean termites are nearly impossible to be detected unless their galleries, such as earth tubes and tunnels, are visible together with a significant infestation of wood that has been hollowed out and filled with fine earth particles [43-45].
The diet of termites is basically rich in cellulose and hemicelluloses as well as lignin or its derivatives. Termites digest lignocellulosic compounds due to the synergizing of their own enzymes and exogenous enzymes from microorganisms. Termites are divided into six feeding groups according to their diets, namely wood feeding, dry-wood feeding, wood and litter feeding, soil feeding, fungus growing and grass feeding termites. The termite gut promotes very specialized cellulolytic and hemicellulolytic microorganisms. The association between certain xylophagous termites and their hindgut protozoa is the fascinating nutritional symbiosis [
21,
46,
47].
Hemicellulose has a random, amorphous structure with weak strength and is easily hydrolyzed by dilute reagents (acid, base, or numerous hemicellulase enzymes) in contrast to cellulose, which is crystalline, robust, and resistant to hydrolysis. Accordingly, hemicellulose is more easily broken down by termites than cellulose and is digested with high efficiency ranging from 49 to 78%. Hence the fundamental constituents of hemicellulose, known as xylans, are polysaccharides created from xylose units. Hemicellulose chain is broken down when beta-1, 4-xylan is broken down by the enzyme xylanase into xylose. Endo-1, 4-xylanase enzyme catalysis is required for the process. Termites can also have various carbohydrases, including sucrase, maltase, trehalase, and raffinase. Chitinase activity, which is made by microbial symbionts, was observed in
Neotermes bosei. When there is a food shortage, cannibalism occurs [
21,
48].
Lignin or its derivatives, cellulose, and hemicelluloses are abundant in the termites' diet. Termites may digest lignocellulosic materials thanks to the collaboration of their own enzymes and foreign enzymes from microbes. Termites can be divided into six feeding categories based on what they prefer to eat: wood, dry wood, wood and litter, soil, fungus, and grass. The termite stomach supports highly specialized cellulolytic and hemicellulolytic microbes. Certain xylophagous termites form an unusual nutritional relationship with their hindgut protozoa. Furthermore, termites and cockroaches' foreguts and midguts, as well as their salivary glands, showed cellulose activity, according to Slaytor [
49]. These areas are the typical sites where digestive enzymes are secreted, and there are no or very few microorganisms present. Therefore, there is no proof that termite cellulose digestion is mediated by bacteria.
Lower and higher termites were reported to be differed in their abilities to digest cellulose. The lower termites produce many endogenous enzymes, including beta-glucosidases, exoglucanases, endoglucanases, chitinases which secreted particularly by their salivary glands as well as foregut. On the other hand, higher termites no longer consume healthy wood due to their deficient symbiotic bacteria in their gut, thus they favor partially fungal-decayed wood, or they raise fungi in elaborate gardens as a source of nutrients (fungus-growing termites). In the tropical regions of Africa and Asia, termites that cultivate fungi coexist in an unusual mutualism with basidiomycete fungi of the genus Termitomyces [
21,
47,
48,
50].
Since cellulose is reinforced by lignin in the higher plants’ cell walls [
13] preventing its bio-digestion, accordingly, the symbiotic fungi starts with disturbing lignin to ensure accessibility for the termites' own cellulose [
47,
51,
52].
The efficiency degrading and consuming cellulose and hemicelluloses from wood by termites using wood was estimated to range from 59 to 99%. Acetate, CO
2, and H
2 are produced when protozoa or a termite's own cellulolytic enzymes directly ferment cellulose under anaerobic conditions. The acetate is subsequently absorbed by the termites, who utilize it as their primary source of oxidizable energy [
21,
49].
Although some organisms, like white-rot fungus and actinomycetes, have the capability of releasing the essential enzymes to break down lignin, it has been demonstrated that lignin is resistant to biochemical effects. Extracellular lignin and manganese peroxidases mediate the first reactions as illustrated by Crawford [53-61] and Kirk and Farrell [
61]
It was indicated by Haug [
62] that increasing lignin content in wood decreases the surface area accessible for enzymatic penetration and activity since lignin is the most resistant component of plant cell walls.
Concerning to nest constructing materials, they prepared mainly by termite themselves else from the woody-degraded residues including organic matter residues and Klason lignin as well as the earth-based materials collected and transported by these insects themselves. For the earth materials, sand, silt, loam, clay, and loose forms of soil with various levels of organic matter contents were all types of soil that the termites themselves used to build their nests [
63,
64]. For the woody-degraded residues, lignin polymer is the main binder used in construction of the termite nests. Similar to how lignin provides mechanical support to plant vasculature, its polymeric network that reinforces termite skeletons was reported to serve as a barrier against microbe attack and a water-tight seal [
21].
White rot fungi can degrade lignin aerobically inside their cells by oxidative enzymes (ligninase peroxidase, manganese peroxidase, and laccases) faster than other organisms [
65]. According to the lignin degradation theory, symbiotic fungus can degrade lignin, allowing termites' own cellulase to consume cellulose [
51,
52]. The absence of any known lignin-degrading bacteria in termite guts and the lack of a known location for lignin degradation both lend credence to the theory [
19]. Since lignin’s polyphenolic structure is more resistant than that of other wood polymers, it has long been thought to be a significant source of stable carbon in soils [
66]. In addition, turnover studies of lignin revealed that large allocations of it was decomposed within a year of when embedded in soils [
66]. Furthermore, Furthermore, the lignin content in older nests was found to be only half that of younger nests. These results are adapted to those indicated by Rückamp et al. [
66].
Termite nests are often rich in organic material. Given that most termite species can't degrade lignin, which was 15 times more abundant at 10 cm depth of the reference soils, lignin might be a useful tracer of the organic matter incorporated into termite nests and released into nest surrounds [
67].
It was indicated that elevated lignin contents were found at 60 cm distance from the nest border as well as up to 60 cm soil depth beneath the nests. The lignin content in older nests was only half that of younger nests, and the influence on the nest surroundings was less prominent. Moreover, savanna termite
C. silvestrii were found to enriches lignin in its earth mounds, but that only a minor part enters the soil-protected lignin fraction when nests decay, as most of the lignin is lost during nest aging [
67].
It was reported that higher lignin content was discovered 60 cm from the edge of the nest and up to 60 cm into the soil beneath the nests. Older nests had lignin contents that were about half as high as those of younger nests, and their influence on the area around the nest was less pronounced. Furthermore, it was discovered that the savanna termite
C. silvestrii enriched lignin in its earth mounds; however, only a little portion of this lignin enters the soil-protected lignin fraction when nests degrade because the majority of the lignin is lost during nest aging [
67].
The crystallinity of cellulose is defined as the ratio of the amount of crystalline cellulose to the total amount of sample material including crystalline and amorphous parts. The CCs comprise different types of cellulose-based materials including microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose nanorods (CNR), cellulose nanowiskers (CNW), cellulose microfibrils (CMF), and cellulose nanofibrils (CNF) [68-76]
The MCC is pure partially depolymerized cellulose synthesized from α-cellulose precursor. The MCC can be synthesized by different processes such as reactive extrusion, enzyme mediated, steam explosion and acid hydrolysis. The later process can be done using mineral acids such as H
2SO, HCl, HBr, ionic liquids, bioenzymes. The role of these reagents is to destroy the amorphous regions remaining the crystalline domains [
69].
Because of its exceptional dry binding capabilities, MCC is a beneficial ingredient in pharmaceutical applications as a tablet binder, as well as in food and cosmetic applications as an anticaking, thickener, texturizer, emulsifier, and bulking agent [
69]. Moreover, due to its high strength, flexibility, and aspect ratio, MCC is also used in paints, paper and nonwoven textiles, oil field services, medicine, and composites.
The NCC is a nano-scale that having at least one dimension less than 100 nanometers in size [
68]. The size, dimensions, and shape of NCCs are determined by the type of the cellulose supply as well as the hydrolysis conditions such as duration, temperature, ultrasonic treatment, and material purity [
71]. In addition, regarding to its high thermal stability, NCC can be regarded as a high potential filler for industrial nanocomposite applications. The charged CNCs’ particles create an anisotropic liquid crystalline phase above a certain concentration [
70].
Several scientists investigated the construction and composition of termite nests referring only to their macro- and micro-scaled materials including lignin, sand, clay and organic matter contents, but no one detected the incorporation of crystalline celluloses (MCC and MCC) within the skeleton of termite nests. Accordingly, one of the current investigation’ target was planned to be studied.
Many farmers and customers are suffering from infestation of their timber trees by termites, accordingly, utilization of such infected woody raw materials as a heat sink can reduce economic loss arisen from the termites’ infection. According to reports, sustainability in energy recovery from biomass is becoming more appealing because biomass emits no new greenhouse gases into the environment [
77,
78]. Timber trees' potential as plantation species is becoming more widely acknowledged in Saudi Arabia, particularly for fast-growing species. In addition to their value as windbreaks and shelterbelts, wood is used as a source of energy through direct burning, particularly in rural locations, villages, and during Muslim pilgrimage at Mena and Araft camps, to provide heat for cooking and other traditional uses. Firewood and charcoal [77-82] are commercially marketed in various locations of Saudi Arabia at large public markets as well as traditional stores. The widespread use of firewood in Saudi Arabia stems from Saudi customs and a preference for Arabic cooking flavors [
78]. Lignocellulosic species were argued to be better suited as fuelwood species due to their high density wood, low ash content, and low nitrogen content. Gross heat of combustion (GHC) of wood is an important property that determines suitability of such wood species for renewable energy supply. It was found a strong relationship between the GHCs of woody materials and their contents of lignin, fixed carbon, and volatile matter contents
[77-82
].
Since in Saudi Arabia, especially the Western region, few systematic field investigations were available only for some metropolitan few cities where grave damage have been reported on wood used in construction or infrastructure or in heavy infestation on agricultural crops, this study were conducted to investigate: 1) The most infected tree species by the small Najdian Termite, Microtermes najdensis located at Hada Al-Sham village Makkah Al-Mukarramah Province, 2) Studying the manner applied to adjust the internal atmosphere: temperature and ventilation (air and humidity) within the termite nest (TN), 3) Studying the mortar blend used for constructing the TN, 4) Inspiring the discovered findings to be realized in living buildings as well as be converted into novel ecofriendly natural composite products, 5) The suitability of the partially-infected wood to be used as a renewable energy resource.
Figure 1.
The management plan for: (A) studying the termite system’s elements: (a1) Air temperature, (a2) Soil, (a3) healthy wood (Wh), (a4) termite nests skeleton (TNS); (B) termite system’ characterization: (b1) air temperature, (b2) soil in open field and the TNS (b3) healthy wood, (b4) termite nests skeleton (TNS).
Figure 1.
The management plan for: (A) studying the termite system’s elements: (a1) Air temperature, (a2) Soil, (a3) healthy wood (Wh), (a4) termite nests skeleton (TNS); (B) termite system’ characterization: (b1) air temperature, (b2) soil in open field and the TNS (b3) healthy wood, (b4) termite nests skeleton (TNS).
Figure 4.
Particle size distribution of the parent soil just beneath each of the six infected tree species.
Figure 4.
Particle size distribution of the parent soil just beneath each of the six infected tree species.
Figure 5.
Electrical conductivity (EC) of the parent soil just beneath the infection sites and the termite nest skeleton (TNS) occupied trunks of the six tree species.
Figure 5.
Electrical conductivity (EC) of the parent soil just beneath the infection sites and the termite nest skeleton (TNS) occupied trunks of the six tree species.
Figure 8.
Optical images of the infection aspects of Zizyphus spina Christi’ s wood infected by the Najdian Termite, Microtermes najdensis: (a) a fall crosscut woody log featured by its degraded sapwood, while its heartwood is still intact; (b) a still living infected trunk featured by its swollen peeled bark, (c) a tunnel shielded by a ceiling made up of a thick layer of the mortar; (d) mortar of the termite nest skeleton (TNS), e,f) entryways noticed at the southwest direction.
Figure 8.
Optical images of the infection aspects of Zizyphus spina Christi’ s wood infected by the Najdian Termite, Microtermes najdensis: (a) a fall crosscut woody log featured by its degraded sapwood, while its heartwood is still intact; (b) a still living infected trunk featured by its swollen peeled bark, (c) a tunnel shielded by a ceiling made up of a thick layer of the mortar; (d) mortar of the termite nest skeleton (TNS), e,f) entryways noticed at the southwest direction.
Figure 9.
Particle size distribution (PSD) of the termite nest skeleton (TNS) occupied trunks of the six tree species.
Figure 9.
Particle size distribution (PSD) of the termite nest skeleton (TNS) occupied trunks of the six tree species.
Figure 10.
Organic matter content (OMC) and mineral content (MiC) of termite nest skeleton (TNS) occupied trunks of the six tree species: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera.
Figure 10.
Organic matter content (OMC) and mineral content (MiC) of termite nest skeleton (TNS) occupied trunks of the six tree species: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera.
Figure 11.
The allocation of organic matter content (OMC) and the Klason lignin content (KLC) from old nests (KLC-O) and recent nests (KLC-R) skeletons within the trunks of the six tree species: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera.
Figure 11.
The allocation of organic matter content (OMC) and the Klason lignin content (KLC) from old nests (KLC-O) and recent nests (KLC-R) skeletons within the trunks of the six tree species: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera.
Figure 14.
SEM micrographs of the microcrystalline cellulose (MCC) synthesized naturally by termites’ enzymatic hydrolysis of cellulose as detected in the termit nest skeleton (TNS) within the six infected tree species: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera.
Figure 14.
SEM micrographs of the microcrystalline cellulose (MCC) synthesized naturally by termites’ enzymatic hydrolysis of cellulose as detected in the termit nest skeleton (TNS) within the six infected tree species: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera.
Figure 18.
Ultimate compressive stress (UCS) of the termite nest skeleton (TNS) constructed in the six infected tree species.
Figure 18.
Ultimate compressive stress (UCS) of the termite nest skeleton (TNS) constructed in the six infected tree species.
Figure 19.
Stress–strain graphs of the termite nest skeleton (TNS) constructed in the six infected tree specie: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera showing proportionality limit (PL) and ultimate compressive stress (UCS).
Figure 19.
Stress–strain graphs of the termite nest skeleton (TNS) constructed in the six infected tree specie: (a) Tamarix aphylla, (b) Pithecellobium duce, (c) Zizyphus spina Christi, (d) Leucaena leucocephala, (e) Ficus infectoria, and (f) Phoenix dactylifera showing proportionality limit (PL) and ultimate compressive stress (UCS).
Figure 20.
Modulus of Elasticity (MoE) of the termite nest skeleton (TNS) constructed naturally within the six infected tree species.
Figure 20.
Modulus of Elasticity (MoE) of the termite nest skeleton (TNS) constructed naturally within the six infected tree species.
Table 3.
Initial physical and chemical analyses of the virgin soil surrounding the infected sites that would be used by termites to construct their nests.
Table 3.
Initial physical and chemical analyses of the virgin soil surrounding the infected sites that would be used by termites to construct their nests.
Variables |
Valuem % |
Clay % |
9.7 |
Silt % |
15.5 |
Sand % |
74.8 |
Texture class |
Sandy loam |
Bulk density (g/cm3) |
1.87 |
Air porosity (%) |
29.4 |
Organic matter (%) |
0.65% |
EC [1:1 soil extraction] (dS m-1) |
0.366 |
pH (1:1 soil suspension) |
7.70 |
Table 4.
Mean values 1,2 for specific gravity (SG), ash content (AC), total extractives content (TEC), holocelluloses (HC), Klason lignin content (KLC) and gross heat of combustion (GHC) of wood samples taken from healthy trees of the six species.
Table 4.
Mean values 1,2 for specific gravity (SG), ash content (AC), total extractives content (TEC), holocelluloses (HC), Klason lignin content (KLC) and gross heat of combustion (GHC) of wood samples taken from healthy trees of the six species.
Species |
SG g/cm3
|
AC4 % |
TEC4 % |
HC4 % |
KLC4 % |
GHC calories/g |
Tamarix aphylla |
0.71 ± 0.04 |
5.43 ± 0.048 |
15.76 ± 0.35 |
51.8 ± 2.08 |
27.9 ± 0.56 |
4393 ± 91.3 |
Pithecellobium duce |
0.61 ± 0.02 |
3.8 ± 0.08 |
6.91 ± 0.31 |
69.41 ± 2.34 |
20.3 ± 0.45 |
4763 ± 102.7 |
Zizyphus spina christi |
0.72 ± 0.018 |
1.9 ± 0.02 |
18.89 ± 0.32 |
59.5 ± 2.42 |
19.71 ± 0.61 |
4814 ± 105.4 |
Leucaena leucocephala |
0.59 ± 0.03 |
1.22 ± 0.02 |
9.74 ± 0. 34 |
70.82 ± 1.73 |
18.86 ± 0.14 |
4206 ± 86.7 |
Ficus infectoria |
0.54 ± 0.032 |
2.44 ± 0.018 |
10.54 ± 0.26 |
61.59 ± 2.85 |
25.43 ± 1.31 |
4367 ± 78.4 |
Phoenix dactylifera |
0.42 ± 0.015 |
6.71 ± 0.71 |
18.3 ± 0.42 |
53.57 ± 2.29 |
22.43 ± 1.07 |
4102 ± 82.49 |
Table 5.
The common absorption bands and their reasons for the alpha cellulose (Cα), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC) within the six infected tree species.
Table 5.
The common absorption bands and their reasons for the alpha cellulose (Cα), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC) within the six infected tree species.
Wavenumber cm−1
|
Reason of band appearance |
1050 |
C–C ring stretching band and C–O–C glycosidic ether band. |
1283 |
Scissoring motion of the CH2-group. |
1583 |
O-H bending of the absorbed water. |
1658 |
C-O stretching vibration for the acetyl and ester linkages. |
2850 |
C-H stretching. |
3367 |
O-H stretching (axial vibration) intramolecular hydrogen bonds. |
Table 6.
Proportionality limit (PL) and ultimate compressive stress (UCS) of the six infected tree species.
Table 6.
Proportionality limit (PL) and ultimate compressive stress (UCS) of the six infected tree species.
Species |
StressType |
StressMPa |
Strain |
Tamarix aphylla |
PL |
0.865 |
0.188 |
UCS |
1.973 |
0.58 |
Pithecellobium duce |
PL |
0.814 |
0.375 |
UCS |
1.992 |
0.878 |
Zizyphus spina christi |
PL |
0.84 |
0.301 |
UCS |
2.037 |
0.805 |
Leucaena leucocephala |
PL |
1.116 |
0.305 |
UCS |
2.092 |
0.858 |
Ficus infectoria |
PL |
0.936 |
0.339 |
UCS |
1.987 |
0.685 |
Phoenix dactylifera |
PL |
0.664 |
0.251 |
UCS |
1.733 |
0.927 |