To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release...To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release of internal stress in the thickness direction in a hydrothermal environment,which increased their warpage.TBLCs showed increased warpage in the width and diagonal directions upon increasing the temperature.The warpage of Type E increased by 155.88%and 66.67%in the width and diagonal directions,respectively,when the temperature increased from 25C to 100C.The symmetrical TBLC with cross-lay-up and odd layers displayed better hydrothermal stability.We revealed that the deformation of the TBLCs could be regulated under the synergistic effect of water and temperature.These results provide a scientific basis for improving the uniformity of bamboo bundle composite materials and for developing thin bamboo bundle fiber composite materials with designable structures and controllable performance.展开更多
In order to investigate the effect of the relative motion of nano CaCO_(3)reinforced bamboo pulp fiber(BPF)/HDPE composite components on the mechanical performance,a comparative study was performed.BPF was treated by ...In order to investigate the effect of the relative motion of nano CaCO_(3)reinforced bamboo pulp fiber(BPF)/HDPE composite components on the mechanical performance,a comparative study was performed.BPF was treated by nano CaCO_(3)blending(BM)and impregnation modification(IM)technology.The composites were produced using hot press(HPMP),extrusion(EMP)and injection molding process(IMP).The physical morphology of BPF was similar at different manufacturing processes.Compared to the samples manufactured by HPMP,a decrease in the(specific)flexural strength of BPF/HDPE composites and an increase in those of composites treated by nano CaCO_(3)manufactured by EMP and IMP were observed.The injection molded composites exhibited the best values in the(specific)impact strength,(specific)tensile properties.IM had a greater effect on the rheological behavior of the composites than BM,and nano CaCO_(3)treatment most effectively affected the performance of the extrusion molded composites.展开更多
Countries are duly focusing more on biomass resources because of the increasing oil crisis.Owing to their excellent properties,such as natural characteristics,good mechanical performance,and outstanding chemical prope...Countries are duly focusing more on biomass resources because of the increasing oil crisis.Owing to their excellent properties,such as natural characteristics,good mechanical performance,and outstanding chemical properties,cellulose-based materials are highly valued as promising bioderived nanomaterials,especially bacterial cellulose(BC).The main advantage lies in eliminating the problem of removing lignin and hemicellulose from woody cellulose.Moreover,the use of BC reduces the consumption of wood,the excessive use of which aggravates global warming.Herein,we summarize the applications of BC composites in filter,medical,and conductive materials,and other fields.This review contributes to further expand the applications of this renewable polymer.展开更多
Drop weight impact tester was used to accurately measure the bending impact resistance of various parts of Phyllostachys edulis,commonly known as moso bamboo,with a growth cycle of 3–8 years.Cellulose crystallinity i...Drop weight impact tester was used to accurately measure the bending impact resistance of various parts of Phyllostachys edulis,commonly known as moso bamboo,with a growth cycle of 3–8 years.Cellulose crystallinity in the bottom(B),middle(M)and top(T)of bamboo at different ages was calculated using peak height analysis in X-ray diffraction.Heatmap of Spearman correlation analysis was used to represent the correlation between chemical composition and impact mechanics.The breaking load(BL),fracture energy(FE)and impact deflection(ID)of 3–8-year-old bamboo were found to be in the range of~670–2120 N,~5.17–15.55 J,and~3.60–~17.76 mm,respectively.As the growth period of bamboo rises,the cellulose crystallinity at the B and T decreases first and then increases,while that for the M increases first and then remains stable.Similarly,the bending impact performance of bamboo was found to become stable with its growth and age.The flexural impact and toughness of the 4-year-old bamboo base material were better than other specimens.The enhancement in the bending impact properties of bamboo at different growth periods was influenced by the lignin content,while the value of FE was mainly positively correlated with ash,cold and hot water extracts and benzyl alcohol content.However the content of holocellulose and pentosan,air-dry density and,base density negatively influenced the FE.With the change in the height of the bamboo,the correlation between its impact mechanical properties and chemical composition gradually decreased.This study provides data support and theoretical basis for the age-appropriate thinning and application of moso bamboo.展开更多
Litter decomposition is key to ecosystem carbon(C)and nutrient cycling,but this process is anticipated to weaken due to projected more extensive and prolonged drought.Yet how litter quality and decomposer community co...Litter decomposition is key to ecosystem carbon(C)and nutrient cycling,but this process is anticipated to weaken due to projected more extensive and prolonged drought.Yet how litter quality and decomposer community complexity regulate decomposition in response to drought is less understood.Here,in a five-year manipulative drought experiment in a Masson pine forest,leaf litter from four subtropical tree species(Quercus griffthii Hook.f.&Thomson ex Miq.,Acacia mangium Willd.,Pinus massoniana Lamb.,Castanopsis hystrix Miq.)representing different qualities was decomposed for 350 d in litterbags of three different mesh sizes(i.e.,0.05,1,and 5 mm),respectively,under natural conditions and a 50%throughfall rain exclusion treatment.Litterbags of increasing mesh sizes discriminate decomposer communities(i.e.,microorganisms,microorganisms and mesofauna,microorganisms and meso-and macrofauna)that access the litter and represent an increasing complexity.The amount of litter C and nitrogen(N)loss,and changes in their ratio(C/N_(loss)),as well as small and medium-sized decomposers including microorganisms,nematodes,and arthropods,were investigated.We found that drought did not affect C and N loss but decreased C/N_(loss)(i.e.,decomposer N use efficiency)of leaf litter irrespective of litter quality and decomposer complexity.However,changes in the C/N_(loss)and the drought effect on C loss were both dependent on litter quality,while drought and decomposer complexity interactively affected litter C and N loss.Increasing decomposer community complexity enhanced litter decomposition and allowing additional access of meso-and macro-fauna to litterbags mitigated the negative drought effect on the microbial-driven decomposition.Furthermore,both the increased diversity and altered trophic structure of nematode due to drought contributed to the mitigation effects via cascading interactions.Our results show that litter quality and soil decomposer community complexity co-drive the effect of drought on litter decomposition.This experimental finding provides a new insight into the mechanisms controlling forest floor C and nutrient cycling under future global change scenarios.展开更多
Korean pine(Pinus koraiensis) and broadleaved mixed forest in Northeast China has been changed regressively into secondary forest with almost no conifers.Planting Korean pine trees under the canopy of secondary fore...Korean pine(Pinus koraiensis) and broadleaved mixed forest in Northeast China has been changed regressively into secondary forest with almost no conifers.Planting Korean pine trees under the canopy of secondary forest is a feasible approach for recovering Korean pine and broadleaved mixed forest.For establishing an effective growth promotion method for under-canopy planted young Korean pine trees,two stands were selected as the experiment plots,Stand A(planted in 1989) and Stand B(planted in 1982),and an experiment of microenvironment regulation was conducted relying mainly on Opening degree(K=1,K=1.5,K=2,CK) in 2004.The results were shown that the adjustment had promoted growth of diameter and height of Korean pine planted in Stand A and Stand B,and had a significant influence on the growth rate of basal diameter,diameter at breast height and height in the two growth stands.The four years periodic increment of mean diameter and height of Korean pine planted in 1989 and in 1982 after regulation in K=1 level were 63.4%(D0) and 82.7%(H),64.8%(D1.3) and 69.7%(H) higher than that of control respectively.Quantitative regulation had significant influence on specific leaf area of Korean pine planted in 1989,and the current year specific leaf area(SLA) was lager than perennial year SLA.Quality indexes of natural pruning capacity,normal form quotient and crown size was not significantly changed but shown a positive tendency.The regulation scheme of Opening degree K=1 might be proper for adjusting the microenvironment of Korean pine trees planted under the canopy of secondary forest when the Korean pine trees were in the growth period of 15 to 26 years old in the experiment region.展开更多
Retrofitting of existing ancient and modern timber structures has been an important project recently.And it triggers a need of excellent strengthening methods,so does the strengthening of newly built architecture.Trad...Retrofitting of existing ancient and modern timber structures has been an important project recently.And it triggers a need of excellent strengthening methods,so does the strengthening of newly built architecture.Traditional strengthening methods have shortcomings such as high costing and destroying the aesthetic of the structure,many of which can be overcome by means of using fiber reinforced polymer(FRP)composites.However,the behavior of FRP-towood systems has yet to be thoroughly researched compared with their FRP-toconcrete or FRP-to-steel counterparts.As FRP retrofitting and strengthening timber structures has a promising future,better understanding of their failure modes will enable more precise designs balancing safety and cost.Three of the most common FRP-to-wood systems in the literature are discussed in this paper,namely,the externally bonded reinforcement(EBR),the near-surface mounted(NSM)and the glued-in rods(GiR)techniques.Debonding of the FRP from the substrate is one of the most common failure modes,which exhibits the significance of the interface bond between FRP laminates and wood.Hence,bond properties and behavior of FRP-to-wood composite systems are described,parameters influencing the composite action are summarized in this paper,previous works on the bond interface of FRP and timber element are reviewed and future topics are also suggested.This work can provide a reference for future research and engineering applications.展开更多
Background:It is still not clear whether the effects of N deposition on soil greenhouse gas(GHG)emissions are influenced by plantation management schemes.A field experiment was conducted to investigate the effects of ...Background:It is still not clear whether the effects of N deposition on soil greenhouse gas(GHG)emissions are influenced by plantation management schemes.A field experiment was conducted to investigate the effects of conventional management(CM)versus intensive management(IM),in combination with simulated N deposition levels of control(ambient N deposition),30 kg N·ha^(−1)·year^(−1)(N30,ambient+30 kg N·ha^(−1)·year^(−1)),60 kg N·ha^(−1)·year^(−1)(N60,ambient+60 kg N·ha^(−1)·year^(−1)),or 90 kg N·ha^(−1)·year^(−1)(N90,ambient+90 kg N·ha^(−1)·year^(−1))on soil CO_(2),CH_(4),and N_(2)O fluxes.For this,24 plots were set up in a Moso bamboo(Phyllostachys edulis)plantation from January 2013 to December 2015.Gas samples were collected monthly from January 2015 to December 2015.Results:Compared with CM,IM significantly increased soil CO_(2) emissions and their temperature sensitivity(Q_(10))but had no significant effects on soil CH_(4) uptake or N_(2)O emissions.In the CM plots,N30 and N60 significantly increased soil CO_(2) emissions,while N60 and N90 significantly increased soil N_(2)O emissions.In the IM plots,N30 and N60 significantly increased soil CO_(2) and N_(2)O emissions,while N60 and N90 significantly decreased soil CH_(4) uptake.Overall,in both CM and IM plots,N30 and N60 significantly increased global warming potentials,whereas N90 did not significantly affect global warming potential.However,N addition significantly decreased the Q_(10) value of soil CO_(2) emissions under IM but not under CM.Soil microbial biomass carbon was significantly and positively correlated with soil CO_(2) and N_(2)O emissions but significantly and negatively correlated with soil CH_(4) uptake.Conclusion:Our results indicate that management scheme effects should be considered when assessing the effect of atmospheric N deposition on GHG emissions in bamboo plantations.展开更多
In this study,natural bamboo fiber was prepared combining chemical pretreatment with mechanical disc refining,opening,and carding.An orthogonal experiment was designed based on four factors and three levels;thereafter...In this study,natural bamboo fiber was prepared combining chemical pretreatment with mechanical disc refining,opening,and carding.An orthogonal experiment was designed based on four factors and three levels;thereafter,the manufacturing process was optimized.The length,diameter,tensile strength,and elastic modulus of the bamboo fiber were determined,and the crystallinity and morphology of the fiber were analyzed using X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results showed that the optimum parameters for the chemical pretreatment were a cooking temperature of 130℃,heating time of 2 h,NaOH dosage of 2%,and Na2SO3 dosage of 10%.The cooking yield of bamboo chips was 89.5%,and the carding yield of natural bamboo fiber was 43.0% under the optimum conditions.The length,diameter,tensile strength,and elastic modulus of the obtained fiber were 36.71 mm,0.285 mm,407 MPa,and 27.7 GPa,respectively.XRD analysis and SEM observations showed that the technology used in this study can produce bright and compact natural bamboo fibers with high crystallinity.展开更多
Background:There are many studies on disentangling the responses of autotrophic(AR)and heterotrophic(HR)respiration components of soil respiration(SR)to long-term drought,but few studies have focused on the mechanisms...Background:There are many studies on disentangling the responses of autotrophic(AR)and heterotrophic(HR)respiration components of soil respiration(SR)to long-term drought,but few studies have focused on the mechanisms underlying its responses.Methods:To explore the impact of prolonged drought on AR and HR,we conducted the 2-year measurements on soil CO_(2) effluxes in the 7th and 8th year of manipulated throughfall reduction(TFR)in a warm-temperate oak forest.Results:Our results showed long-term TFR decreased HR,which was positively related to bacterial richness.More importantly,some bacterial taxa such as Novosphingobium and norank Acidimicrobiia,and fungal Leptobacillium were identified as major drivers of HR.In contrast,long-term TFR increased AR due to the increased fine root biomass and production.The increased AR accompanied by decreased HR appeared to counteract each other,and subsequently resulted in the unchanged SR under the TFR.Conclusions:Our study shows that HR and AR respond in the opposite directions to long-term TFR.Soil microorganisms and fine roots account for the respective mechanisms underlying the divergent responses of HR and AR to long-term TFR.This highlights the contrasting responses of AR and HR to prolonged drought should be taken into account when predicting soil CO_(2) effluxes under future droughts.展开更多
Pretreatment is important for achieving high-value utilization of biomass.This study is conducted to evaluate the destruction of the Moso bamboo cell wall via hydrothermal pretreatment at different temperatures and pH...Pretreatment is important for achieving high-value utilization of biomass.This study is conducted to evaluate the destruction of the Moso bamboo cell wall via hydrothermal pretreatment at different temperatures and pH values.Compositional and morphological analyses and subsequent enzymatic hydrolysis of the solid fractions indicate that the destruction of the cell wall,instead of the degradation or removal of hemicellulose and lignin,or the configuration transition of the cellulose crystal structure,is the most critical aspect for improving bioconversion efficiency.Although only an 8%-10%weight loss is incurred and similar crystalline indexes are achieved after mild hydrothermal treatments,the recovery of glucose is doubled,whereas the recovery of xylose from pretreated samples is approximately 35%.展开更多
There are two distinct types of domains,design-and cross-classes domains,with the former extensively studied under the topic of small-area estimation.In natural resource inventory,however,most classes listed in the co...There are two distinct types of domains,design-and cross-classes domains,with the former extensively studied under the topic of small-area estimation.In natural resource inventory,however,most classes listed in the condition tables of national inventory programs are characterized as cross-classes domains,such as vegetation type,productivity class,and age class.To date,challenges remain active for inventorying cross-classes domains because these domains are usually of unknown sampling frame and spatial distribution with the result that inference relies on population-level as opposed to domain-level sampling.Multiple challenges are noteworthy:(1)efficient sampling strategies are difficult to develop because of little priori information about the target domain;(2)domain inference relies on a sample designed for the population,so within-domain sample sizes could be too small to support a precise estimation;and(3)increasing sample size for the population does not ensure an increase to the domain,so actual sample size for a target domain remains highly uncertain,particularly for small domains.In this paper,we introduce a design-based generalized systematic adaptive cluster sampling(GSACS)for inventorying cross-classes domains.Design-unbiased Hansen-Hurwitz and Horvitz-Thompson estimators are derived for domain totals and compared within GSACS and with systematic sampling(SYS).Comprehensive Monte Carlo simulations show that(1)GSACS Hansen-Hurwitz and Horvitz-Thompson estimators are unbiased and equally efficient,whereas thelatter outperforms the former for supporting a sample of size one;(2)SYS is a special case of GSACS while the latter outperforms the former in terms of increased efficiency and reduced intensity;(3)GSACS Horvitz-Thompson variance estimator is design-unbiased for a single SYS sample;and(4)rules-ofthumb summarized with respect to sampling design and spatial effect improve precision.Because inventorying a mini domain is analogous to inventorying a rare variable,alternative network sampling procedures are also readily available for inventorying cross-classes domains.展开更多
Bamboo, with its advantages of fast growth, short renovation, easy propagation and rich in cellulose and hemicellulose, is a potential feedstock for bioethanol or other biofuels production. The objective of this study...Bamboo, with its advantages of fast growth, short renovation, easy propagation and rich in cellulose and hemicellulose, is a potential feedstock for bioethanol or other biofuels production. The objective of this study was to examine the feasibility of microwave assistant KOH pretreatments to enhance enzymatic hydrolysis of bamboo. Pretreatment was carried out by immersing the bamboo in KOH (12% and 8% w/w bamboo) solutions and exposing the slurry to microwave radiation power of 400 W for 30min. Chemical composition of the pretreated substrates and spent liquor was analyzed. Pretreated substrates were enzymatic hydrolyzed, and glucose and xylose in the hydrolysate were analyzed. The results showed that the pretreated substrate with microwave assisted KOH had significantly higher sugar yield than the untreated samples. The fermentation inhibitors formic acid, furfural, HMF and levulinic acid were much lower than acid pretreatment reported.展开更多
Nitrogen(N)present in drinking water as dissolved nitrates can directly affect people’s health,making it important to control N pollution in water source areas.N pollution caused by agricultural fertilizers can be co...Nitrogen(N)present in drinking water as dissolved nitrates can directly affect people’s health,making it important to control N pollution in water source areas.N pollution caused by agricultural fertilizers can be controlled by reducing the amount of fertilizer applied,but pollution caused by soil and water erosion in hilly areas can only be controlled by conservation forests.The catchment area around Fushi Reservoir was selected as a test site and mechanisms of N loss from a vertical spatial perspective through field observations were determined.The main N losses occurred from June to September,accounting for 85.9-95.9%of the annual loss,with the losses in June and July accounting for 46.0%of the total,and in August and September for 41.9%.The N leakage from the water source area was effectively reduced by 38.2%through the optimization of the stand structure of the conservation forests.Establishing well-structured forests for water conservation is crucial to ensure the security of drinking water.This preliminary research lays the foundation for revealing then loss mechanisms in water source areas and improving the control of non-point source pollution in these areas.展开更多
Root-associated microbes play an essentialrole in mediating plant growth,health,and habitat adaptability.However,it is unknown which microbial taxa help develop host fitness and how habitats shape root-associated micr...Root-associated microbes play an essentialrole in mediating plant growth,health,and habitat adaptability.However,it is unknown which microbial taxa help develop host fitness and how habitats shape root-associated microbial assembly patterns.As an endemic species of subalpine forests in western Sichuan,China,Minjiang fir(Abies fargesii var.faxoniana)is dominant on cold-shaded northwestern slopes while absent on warm sunlit southwestern slopes.In this study,fungal and bacterial communities were investigated in three spatial compartments(endosphere,rhizosphere,and bulk soil)associated with Minjiang fir saplings on a cold-shaded northwestern slope and a warm sunlit southwestern slope.Habitats differentiated the microbial communities regardless of the spatial compartment and microbial taxa.Slope aspect variations caused shifts in root-associated(rhizosphere and endosphere)microbial compositions.Compared with the southwestern slope,the cold-shaded northwestern slope harbored a higher abundance of the growth-promoting bacteria Burkholderia and ectomycorrhizal fungi Cortinarius and Piloderma.The slope aspect had stronger effects on fungal diversity than bacterial diversity,with higher fungal endemism and lower bacterial endemism.Slope aspect variations were the dominant drivers of root-associated microbial communities,with lower contribution by soil properties and higher contribution by plant traits on the northwestern slope.Findings from this study could improve the understanding of plant habitat adaptability from the perspective of microbial community assembly.It is suggested that forest management should consider root-associated microbiomes for enhancing species fitness and habitat adaptability.展开更多
INTRODUCTION Bamboo and rattan are valuable resources that can be used as nature-based solutions to several pressing global challenges by contributing to poverty reduction,the development of green industries and trade...INTRODUCTION Bamboo and rattan are valuable resources that can be used as nature-based solutions to several pressing global challenges by contributing to poverty reduction,the development of green industries and trade,the adaptation and mitigation of climate change,and the preservation of the environment.Largely growing in less-developed regions of the tropics and subtropics,the two plant groups are welcomed by local communities as they provide a wide variety of ecofriendly,sustainable products,livelihood opportunities,and ecosystem services.展开更多
Bamboo is a typical biological material widely growing in nature with excellent physical and mechanical properties.It is lightweight with high strength and toughness.The naturally optimized bamboo structure,which has ...Bamboo is a typical biological material widely growing in nature with excellent physical and mechanical properties.It is lightweight with high strength and toughness.The naturally optimized bamboo structure,which has inspired global material scientists and engineers for decades,is significantly important for the bionic design of novel structural materials with ultra-light,ultra-strong,or ultra-tough and comprehensive properties.Typical literature on innovative composite materials and structural members inspired by bamboo are reviewed in this paper,and the research progress and prospects in this field are expounded in three parts.First,the structural characteristics of the bamboo wall layer along the thickness and height directions are described in terms of chemical composition,gradient structure,pore structure,and hollow structure with variable cross-section.Second,this paper summarizes the research progress on new composite materials and structural components by applying bamboo’s structural features from the perspective of sustainability,designability,and customization.Finally,given the limitations of current research,the biomimetic scientific research on bamboo’s structural characteristics is prospected from the interpretation of bamboo structure,new bamboo-like materials,and structural design optimization perspectives,providing a reference for future research on biomimetic aspects of biomass.展开更多
基金supported by the Youth Top-notch Talent Program of Science and Technology Innovation for Forestry and Grassland(2019132606).
文摘To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release of internal stress in the thickness direction in a hydrothermal environment,which increased their warpage.TBLCs showed increased warpage in the width and diagonal directions upon increasing the temperature.The warpage of Type E increased by 155.88%and 66.67%in the width and diagonal directions,respectively,when the temperature increased from 25C to 100C.The symmetrical TBLC with cross-lay-up and odd layers displayed better hydrothermal stability.We revealed that the deformation of the TBLCs could be regulated under the synergistic effect of water and temperature.These results provide a scientific basis for improving the uniformity of bamboo bundle composite materials and for developing thin bamboo bundle fiber composite materials with designable structures and controllable performance.
基金This study is financially supported by the Basic Research Operating Expenses Program of International Centre for Bamboo and Rattan(1632021002).
文摘In order to investigate the effect of the relative motion of nano CaCO_(3)reinforced bamboo pulp fiber(BPF)/HDPE composite components on the mechanical performance,a comparative study was performed.BPF was treated by nano CaCO_(3)blending(BM)and impregnation modification(IM)technology.The composites were produced using hot press(HPMP),extrusion(EMP)and injection molding process(IMP).The physical morphology of BPF was similar at different manufacturing processes.Compared to the samples manufactured by HPMP,a decrease in the(specific)flexural strength of BPF/HDPE composites and an increase in those of composites treated by nano CaCO_(3)manufactured by EMP and IMP were observed.The injection molded composites exhibited the best values in the(specific)impact strength,(specific)tensile properties.IM had a greater effect on the rheological behavior of the composites than BM,and nano CaCO_(3)treatment most effectively affected the performance of the extrusion molded composites.
基金supported by grants from the National Key Research and Development Program of China(2022YFD2200804)National Natural Science Foundation of China(No.31770622).
文摘Countries are duly focusing more on biomass resources because of the increasing oil crisis.Owing to their excellent properties,such as natural characteristics,good mechanical performance,and outstanding chemical properties,cellulose-based materials are highly valued as promising bioderived nanomaterials,especially bacterial cellulose(BC).The main advantage lies in eliminating the problem of removing lignin and hemicellulose from woody cellulose.Moreover,the use of BC reduces the consumption of wood,the excessive use of which aggravates global warming.Herein,we summarize the applications of BC composites in filter,medical,and conductive materials,and other fields.This review contributes to further expand the applications of this renewable polymer.
基金Fundamental Research on Impact Toughness and Response Mechanism of Bamboo-woven Structural Materials Funded of International Center for Bamboo and Rattan(1632020016).
文摘Drop weight impact tester was used to accurately measure the bending impact resistance of various parts of Phyllostachys edulis,commonly known as moso bamboo,with a growth cycle of 3–8 years.Cellulose crystallinity in the bottom(B),middle(M)and top(T)of bamboo at different ages was calculated using peak height analysis in X-ray diffraction.Heatmap of Spearman correlation analysis was used to represent the correlation between chemical composition and impact mechanics.The breaking load(BL),fracture energy(FE)and impact deflection(ID)of 3–8-year-old bamboo were found to be in the range of~670–2120 N,~5.17–15.55 J,and~3.60–~17.76 mm,respectively.As the growth period of bamboo rises,the cellulose crystallinity at the B and T decreases first and then increases,while that for the M increases first and then remains stable.Similarly,the bending impact performance of bamboo was found to become stable with its growth and age.The flexural impact and toughness of the 4-year-old bamboo base material were better than other specimens.The enhancement in the bending impact properties of bamboo at different growth periods was influenced by the lignin content,while the value of FE was mainly positively correlated with ash,cold and hot water extracts and benzyl alcohol content.However the content of holocellulose and pentosan,air-dry density and,base density negatively influenced the FE.With the change in the height of the bamboo,the correlation between its impact mechanical properties and chemical composition gradually decreased.This study provides data support and theoretical basis for the age-appropriate thinning and application of moso bamboo.
基金jointly funded by the National Natural Science Foundation of China(No.31930078)the National Key R&D Program of China(No.2021YFD2200405)+3 种基金Science and Technology Cooperation Projects between governments of China and the European Union(No.2023YFE0105100)the Fundamental Research Funds for ICBR(No.1632021023)Sanya Research Base of ICBR(No.1630032023002)the Scientific and Technological Innovation Team for Qinghai-Tibetan Plateau Research in Southwest Minzu University(No.2024CXTD10)。
文摘Litter decomposition is key to ecosystem carbon(C)and nutrient cycling,but this process is anticipated to weaken due to projected more extensive and prolonged drought.Yet how litter quality and decomposer community complexity regulate decomposition in response to drought is less understood.Here,in a five-year manipulative drought experiment in a Masson pine forest,leaf litter from four subtropical tree species(Quercus griffthii Hook.f.&Thomson ex Miq.,Acacia mangium Willd.,Pinus massoniana Lamb.,Castanopsis hystrix Miq.)representing different qualities was decomposed for 350 d in litterbags of three different mesh sizes(i.e.,0.05,1,and 5 mm),respectively,under natural conditions and a 50%throughfall rain exclusion treatment.Litterbags of increasing mesh sizes discriminate decomposer communities(i.e.,microorganisms,microorganisms and mesofauna,microorganisms and meso-and macrofauna)that access the litter and represent an increasing complexity.The amount of litter C and nitrogen(N)loss,and changes in their ratio(C/N_(loss)),as well as small and medium-sized decomposers including microorganisms,nematodes,and arthropods,were investigated.We found that drought did not affect C and N loss but decreased C/N_(loss)(i.e.,decomposer N use efficiency)of leaf litter irrespective of litter quality and decomposer complexity.However,changes in the C/N_(loss)and the drought effect on C loss were both dependent on litter quality,while drought and decomposer complexity interactively affected litter C and N loss.Increasing decomposer community complexity enhanced litter decomposition and allowing additional access of meso-and macro-fauna to litterbags mitigated the negative drought effect on the microbial-driven decomposition.Furthermore,both the increased diversity and altered trophic structure of nematode due to drought contributed to the mitigation effects via cascading interactions.Our results show that litter quality and soil decomposer community complexity co-drive the effect of drought on litter decomposition.This experimental finding provides a new insight into the mechanisms controlling forest floor C and nutrient cycling under future global change scenarios.
基金supported by the Project of AGRFUND from Ministry of Science and Technology of the People's Republic of China (Project No. 2007GB24320427)
文摘Korean pine(Pinus koraiensis) and broadleaved mixed forest in Northeast China has been changed regressively into secondary forest with almost no conifers.Planting Korean pine trees under the canopy of secondary forest is a feasible approach for recovering Korean pine and broadleaved mixed forest.For establishing an effective growth promotion method for under-canopy planted young Korean pine trees,two stands were selected as the experiment plots,Stand A(planted in 1989) and Stand B(planted in 1982),and an experiment of microenvironment regulation was conducted relying mainly on Opening degree(K=1,K=1.5,K=2,CK) in 2004.The results were shown that the adjustment had promoted growth of diameter and height of Korean pine planted in Stand A and Stand B,and had a significant influence on the growth rate of basal diameter,diameter at breast height and height in the two growth stands.The four years periodic increment of mean diameter and height of Korean pine planted in 1989 and in 1982 after regulation in K=1 level were 63.4%(D0) and 82.7%(H),64.8%(D1.3) and 69.7%(H) higher than that of control respectively.Quantitative regulation had significant influence on specific leaf area of Korean pine planted in 1989,and the current year specific leaf area(SLA) was lager than perennial year SLA.Quality indexes of natural pruning capacity,normal form quotient and crown size was not significantly changed but shown a positive tendency.The regulation scheme of Opening degree K=1 might be proper for adjusting the microenvironment of Korean pine trees planted under the canopy of secondary forest when the Korean pine trees were in the growth period of 15 to 26 years old in the experiment region.
基金supported by the Key Laboratory of National Forestry and Grassland Administration/Beijing for Bamboo&Rattan Science and Technology,the National Natural Science Foundation of China(Nos.51878354&51308301)the Natural Science Foundation of Jiangsu Province(Nos.BK20181402&BK20130978)+1 种基金Postgraduate Research&Practice Innovation Program of Jiangsu Province,Six talent peak high-level projects of Jiang-su Province(No.JZ-029)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Retrofitting of existing ancient and modern timber structures has been an important project recently.And it triggers a need of excellent strengthening methods,so does the strengthening of newly built architecture.Traditional strengthening methods have shortcomings such as high costing and destroying the aesthetic of the structure,many of which can be overcome by means of using fiber reinforced polymer(FRP)composites.However,the behavior of FRP-towood systems has yet to be thoroughly researched compared with their FRP-toconcrete or FRP-to-steel counterparts.As FRP retrofitting and strengthening timber structures has a promising future,better understanding of their failure modes will enable more precise designs balancing safety and cost.Three of the most common FRP-to-wood systems in the literature are discussed in this paper,namely,the externally bonded reinforcement(EBR),the near-surface mounted(NSM)and the glued-in rods(GiR)techniques.Debonding of the FRP from the substrate is one of the most common failure modes,which exhibits the significance of the interface bond between FRP laminates and wood.Hence,bond properties and behavior of FRP-to-wood composite systems are described,parameters influencing the composite action are summarized in this paper,previous works on the bond interface of FRP and timber element are reviewed and future topics are also suggested.This work can provide a reference for future research and engineering applications.
基金This study was funded by the National Natural Science Foundation of China(Grant Nos.31270517 and 31470529).
文摘Background:It is still not clear whether the effects of N deposition on soil greenhouse gas(GHG)emissions are influenced by plantation management schemes.A field experiment was conducted to investigate the effects of conventional management(CM)versus intensive management(IM),in combination with simulated N deposition levels of control(ambient N deposition),30 kg N·ha^(−1)·year^(−1)(N30,ambient+30 kg N·ha^(−1)·year^(−1)),60 kg N·ha^(−1)·year^(−1)(N60,ambient+60 kg N·ha^(−1)·year^(−1)),or 90 kg N·ha^(−1)·year^(−1)(N90,ambient+90 kg N·ha^(−1)·year^(−1))on soil CO_(2),CH_(4),and N_(2)O fluxes.For this,24 plots were set up in a Moso bamboo(Phyllostachys edulis)plantation from January 2013 to December 2015.Gas samples were collected monthly from January 2015 to December 2015.Results:Compared with CM,IM significantly increased soil CO_(2) emissions and their temperature sensitivity(Q_(10))but had no significant effects on soil CH_(4) uptake or N_(2)O emissions.In the CM plots,N30 and N60 significantly increased soil CO_(2) emissions,while N60 and N90 significantly increased soil N_(2)O emissions.In the IM plots,N30 and N60 significantly increased soil CO_(2) and N_(2)O emissions,while N60 and N90 significantly decreased soil CH_(4) uptake.Overall,in both CM and IM plots,N30 and N60 significantly increased global warming potentials,whereas N90 did not significantly affect global warming potential.However,N addition significantly decreased the Q_(10) value of soil CO_(2) emissions under IM but not under CM.Soil microbial biomass carbon was significantly and positively correlated with soil CO_(2) and N_(2)O emissions but significantly and negatively correlated with soil CH_(4) uptake.Conclusion:Our results indicate that management scheme effects should be considered when assessing the effect of atmospheric N deposition on GHG emissions in bamboo plantations.
基金financially supported by the National Key R&D Program of China(2017YFD0600802).
文摘In this study,natural bamboo fiber was prepared combining chemical pretreatment with mechanical disc refining,opening,and carding.An orthogonal experiment was designed based on four factors and three levels;thereafter,the manufacturing process was optimized.The length,diameter,tensile strength,and elastic modulus of the bamboo fiber were determined,and the crystallinity and morphology of the fiber were analyzed using X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results showed that the optimum parameters for the chemical pretreatment were a cooking temperature of 130℃,heating time of 2 h,NaOH dosage of 2%,and Na2SO3 dosage of 10%.The cooking yield of bamboo chips was 89.5%,and the carding yield of natural bamboo fiber was 43.0% under the optimum conditions.The length,diameter,tensile strength,and elastic modulus of the obtained fiber were 36.71 mm,0.285 mm,407 MPa,and 27.7 GPa,respectively.XRD analysis and SEM observations showed that the technology used in this study can produce bright and compact natural bamboo fibers with high crystallinity.
基金supported by the National Key R&D Program of China(No.2018YFC0507301)by Research and Development Project of RIFEEP,Chinese Academy of Forestry(99802–2020).
文摘Background:There are many studies on disentangling the responses of autotrophic(AR)and heterotrophic(HR)respiration components of soil respiration(SR)to long-term drought,but few studies have focused on the mechanisms underlying its responses.Methods:To explore the impact of prolonged drought on AR and HR,we conducted the 2-year measurements on soil CO_(2) effluxes in the 7th and 8th year of manipulated throughfall reduction(TFR)in a warm-temperate oak forest.Results:Our results showed long-term TFR decreased HR,which was positively related to bacterial richness.More importantly,some bacterial taxa such as Novosphingobium and norank Acidimicrobiia,and fungal Leptobacillium were identified as major drivers of HR.In contrast,long-term TFR increased AR due to the increased fine root biomass and production.The increased AR accompanied by decreased HR appeared to counteract each other,and subsequently resulted in the unchanged SR under the TFR.Conclusions:Our study shows that HR and AR respond in the opposite directions to long-term TFR.Soil microorganisms and fine roots account for the respective mechanisms underlying the divergent responses of HR and AR to long-term TFR.This highlights the contrasting responses of AR and HR to prolonged drought should be taken into account when predicting soil CO_(2) effluxes under future droughts.
基金This study was supported by a grant from the Natural Science Foundation of China(No.31770622).
文摘Pretreatment is important for achieving high-value utilization of biomass.This study is conducted to evaluate the destruction of the Moso bamboo cell wall via hydrothermal pretreatment at different temperatures and pH values.Compositional and morphological analyses and subsequent enzymatic hydrolysis of the solid fractions indicate that the destruction of the cell wall,instead of the degradation or removal of hemicellulose and lignin,or the configuration transition of the cellulose crystal structure,is the most critical aspect for improving bioconversion efficiency.Although only an 8%-10%weight loss is incurred and similar crystalline indexes are achieved after mild hydrothermal treatments,the recovery of glucose is doubled,whereas the recovery of xylose from pretreated samples is approximately 35%.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 2021ZY04)the National Natural Science Foundation of China (Grant No. 32001252)the International Center for Bamboo and Rattan (Grant No. 1632020029)
文摘There are two distinct types of domains,design-and cross-classes domains,with the former extensively studied under the topic of small-area estimation.In natural resource inventory,however,most classes listed in the condition tables of national inventory programs are characterized as cross-classes domains,such as vegetation type,productivity class,and age class.To date,challenges remain active for inventorying cross-classes domains because these domains are usually of unknown sampling frame and spatial distribution with the result that inference relies on population-level as opposed to domain-level sampling.Multiple challenges are noteworthy:(1)efficient sampling strategies are difficult to develop because of little priori information about the target domain;(2)domain inference relies on a sample designed for the population,so within-domain sample sizes could be too small to support a precise estimation;and(3)increasing sample size for the population does not ensure an increase to the domain,so actual sample size for a target domain remains highly uncertain,particularly for small domains.In this paper,we introduce a design-based generalized systematic adaptive cluster sampling(GSACS)for inventorying cross-classes domains.Design-unbiased Hansen-Hurwitz and Horvitz-Thompson estimators are derived for domain totals and compared within GSACS and with systematic sampling(SYS).Comprehensive Monte Carlo simulations show that(1)GSACS Hansen-Hurwitz and Horvitz-Thompson estimators are unbiased and equally efficient,whereas thelatter outperforms the former for supporting a sample of size one;(2)SYS is a special case of GSACS while the latter outperforms the former in terms of increased efficiency and reduced intensity;(3)GSACS Horvitz-Thompson variance estimator is design-unbiased for a single SYS sample;and(4)rules-ofthumb summarized with respect to sampling design and spatial effect improve precision.Because inventorying a mini domain is analogous to inventorying a rare variable,alternative network sampling procedures are also readily available for inventorying cross-classes domains.
文摘Bamboo, with its advantages of fast growth, short renovation, easy propagation and rich in cellulose and hemicellulose, is a potential feedstock for bioethanol or other biofuels production. The objective of this study was to examine the feasibility of microwave assistant KOH pretreatments to enhance enzymatic hydrolysis of bamboo. Pretreatment was carried out by immersing the bamboo in KOH (12% and 8% w/w bamboo) solutions and exposing the slurry to microwave radiation power of 400 W for 30min. Chemical composition of the pretreated substrates and spent liquor was analyzed. Pretreated substrates were enzymatic hydrolyzed, and glucose and xylose in the hydrolysate were analyzed. The results showed that the pretreated substrate with microwave assisted KOH had significantly higher sugar yield than the untreated samples. The fermentation inhibitors formic acid, furfural, HMF and levulinic acid were much lower than acid pretreatment reported.
基金supported by Zhejiang A&F University(2022LFR083)Key R&D Program of Zhejiang Province(2021C02038)the International Centre for Bamboo and Rattan(1632021006)。
文摘Nitrogen(N)present in drinking water as dissolved nitrates can directly affect people’s health,making it important to control N pollution in water source areas.N pollution caused by agricultural fertilizers can be controlled by reducing the amount of fertilizer applied,but pollution caused by soil and water erosion in hilly areas can only be controlled by conservation forests.The catchment area around Fushi Reservoir was selected as a test site and mechanisms of N loss from a vertical spatial perspective through field observations were determined.The main N losses occurred from June to September,accounting for 85.9-95.9%of the annual loss,with the losses in June and July accounting for 46.0%of the total,and in August and September for 41.9%.The N leakage from the water source area was effectively reduced by 38.2%through the optimization of the stand structure of the conservation forests.Establishing well-structured forests for water conservation is crucial to ensure the security of drinking water.This preliminary research lays the foundation for revealing then loss mechanisms in water source areas and improving the control of non-point source pollution in these areas.
基金jointly funded by the National Key Research and Development Program of China (No.2021YFD2200405)the National Natural Science Foundation of China (No.31930078)。
文摘Root-associated microbes play an essentialrole in mediating plant growth,health,and habitat adaptability.However,it is unknown which microbial taxa help develop host fitness and how habitats shape root-associated microbial assembly patterns.As an endemic species of subalpine forests in western Sichuan,China,Minjiang fir(Abies fargesii var.faxoniana)is dominant on cold-shaded northwestern slopes while absent on warm sunlit southwestern slopes.In this study,fungal and bacterial communities were investigated in three spatial compartments(endosphere,rhizosphere,and bulk soil)associated with Minjiang fir saplings on a cold-shaded northwestern slope and a warm sunlit southwestern slope.Habitats differentiated the microbial communities regardless of the spatial compartment and microbial taxa.Slope aspect variations caused shifts in root-associated(rhizosphere and endosphere)microbial compositions.Compared with the southwestern slope,the cold-shaded northwestern slope harbored a higher abundance of the growth-promoting bacteria Burkholderia and ectomycorrhizal fungi Cortinarius and Piloderma.The slope aspect had stronger effects on fungal diversity than bacterial diversity,with higher fungal endemism and lower bacterial endemism.Slope aspect variations were the dominant drivers of root-associated microbial communities,with lower contribution by soil properties and higher contribution by plant traits on the northwestern slope.Findings from this study could improve the understanding of plant habitat adaptability from the perspective of microbial community assembly.It is suggested that forest management should consider root-associated microbiomes for enhancing species fitness and habitat adaptability.
基金supported by the National Key Research and Development Program of China(2021YFD2201000)the National Natural Science Foundation of China(31971733 and 31400557).M.D.acknowledges financial support fromthe Council of Scientific and Industrial Research,India(38(1493)/19/EMR-II)and the Department of Biotechnology,India(BT/PR28859/FCB/125/3/2018 and BT/INF/22/SP45088/2022).
文摘INTRODUCTION Bamboo and rattan are valuable resources that can be used as nature-based solutions to several pressing global challenges by contributing to poverty reduction,the development of green industries and trade,the adaptation and mitigation of climate change,and the preservation of the environment.Largely growing in less-developed regions of the tropics and subtropics,the two plant groups are welcomed by local communities as they provide a wide variety of ecofriendly,sustainable products,livelihood opportunities,and ecosystem services.
文摘Bamboo is a typical biological material widely growing in nature with excellent physical and mechanical properties.It is lightweight with high strength and toughness.The naturally optimized bamboo structure,which has inspired global material scientists and engineers for decades,is significantly important for the bionic design of novel structural materials with ultra-light,ultra-strong,or ultra-tough and comprehensive properties.Typical literature on innovative composite materials and structural members inspired by bamboo are reviewed in this paper,and the research progress and prospects in this field are expounded in three parts.First,the structural characteristics of the bamboo wall layer along the thickness and height directions are described in terms of chemical composition,gradient structure,pore structure,and hollow structure with variable cross-section.Second,this paper summarizes the research progress on new composite materials and structural components by applying bamboo’s structural features from the perspective of sustainability,designability,and customization.Finally,given the limitations of current research,the biomimetic scientific research on bamboo’s structural characteristics is prospected from the interpretation of bamboo structure,new bamboo-like materials,and structural design optimization perspectives,providing a reference for future research on biomimetic aspects of biomass.