Plant derived natural fibers have been widely investigated as alternatives to synthetic fibers in reinforcing polymers.Researchers over the years have explored many plant fibers using different extraction processes to...Plant derived natural fibers have been widely investigated as alternatives to synthetic fibers in reinforcing polymers.Researchers over the years have explored many plant fibers using different extraction processes to study their physical,chemical,and mechanical properties.In this context,the present study relates to the extraction,characterization,and optimization of Typha angustata L.stem fibers.For this purpose,desirability functions and response surface methodology were applied to simultaneously optimize the diameter(D),linear density(LD);yield(Y),lignin fraction(L),and tenacity(T)of Typha stem fibers.Typha stems have been subjected to both alkali(NaOH)and enzymatic(pectinex ultra-SPL)treatments.Three levels of process variables including enzyme concentration(10,15,and 20 ml/L)and treatment duration(10,15,and 20 days)were used to design the experiments according to the factorial design.Experimental results were examined by analysis of variance and fitted to second order polynomial model using multiple regression analysis.The Derringer’s desirability function released that the values of process variables generating optimized diameter,linear density,yield,lignin ratio and tenacity are 20 ml/L and 20 days for concentration of pectinex ultra-SPL enzyme and treatment duration,respectively.Confirmation was performed and high degree of correlation was found between the experimental and statistical values.Moreover,the morphological structure has been investigated by the scanning electron microscope,showing a crenelated structure of ultimate fiber bundles of cellulose composing the Typha fiber.Compared to Typha stem non-treated fibers(TSNTF),Typha stem combined treated fibers(TSCTF),brings to improve mechanical properties.This change in mechanical properties is affected by modifying the fiber structure showing alpha cellulose of(66.86%)and lignin ratio of(10.83%)with a crystallinity index of(58.47%).展开更多
氮(N)是陆地生态系统初级生产力的重要限制因子,大气N沉降的增加将会对植物的化学元素含量和生物量产生重要影响,进而影响凋落物的化学计量特征及其养分归还。高寒灌丛是陆地生态系统的重要组成部分,但有关N沉降对高寒灌丛凋落物尤其是...氮(N)是陆地生态系统初级生产力的重要限制因子,大气N沉降的增加将会对植物的化学元素含量和生物量产生重要影响,进而影响凋落物的化学计量特征及其养分归还。高寒灌丛是陆地生态系统的重要组成部分,但有关N沉降对高寒灌丛凋落物尤其是凋落枝的化学元素和生物量的研究还较为缺乏,难以深入揭示N沉降对高寒灌丛土壤碳(C)和养分循环的影响机理。基于此,以青藏高原东部地区的优势高寒灌丛类型—窄叶鲜卑花(Sibiraea angustata(Rehd.)Hand.-Mazz.)灌丛为研究对象,连续4年人工模拟N沉降,分析了凋落枝C、N、磷(P)、木质素和纤维素化学计量特征及其归还量对不同N添加浓度(0、20、50、100 kg hm^(-2)a^(-1))的响应趋势。结果表明:(1)N添加对凋落枝C、N含量无显著性影响(P>0.05),而对P、木质素和纤维素含量有显著性影响(P<0.05),但不同年份间的影响趋势不一致;(2)4年的N添加并未改变凋落枝的C/N、N/P,但显著降低了凋落枝的木质素/N(第3年)、C/P(第1年和第4年)和C/N/P(第1年);(3)随着N添加浓度的增加,凋落枝C、N、P、木质素和纤维素4年累积归还量呈显著的二次方变化趋势(P<0.05),并在中N处理(50 kg hm^(-2)a^(-1))下达到最大。研究认为,N添加对凋落枝化学计量特征的影响具有较大的年际变异,短期、适当的N添加通过增加凋落枝的生物量而并非改变其化学计量特征促进了凋落枝碳和养分的归还。展开更多
开展土壤呼吸对大气氮沉降增加的响应研究对预测陆地生态系统碳循环具有重要意义。采用外施氮肥模拟氮沉降,结合壕沟法分离土壤呼吸组分,研究青藏高原东缘主要的灌丛类型——窄叶鲜卑花(Sibiraea angustata)灌丛土壤呼吸对不同施氮水平(...开展土壤呼吸对大气氮沉降增加的响应研究对预测陆地生态系统碳循环具有重要意义。采用外施氮肥模拟氮沉降,结合壕沟法分离土壤呼吸组分,研究青藏高原东缘主要的灌丛类型——窄叶鲜卑花(Sibiraea angustata)灌丛土壤呼吸对不同施氮水平(N0(对照)、N2、N5和N10分别相当于0、2、5和10 g N m-2a-1浓度的氮沉降)的短期响应。结果表明:试验期间(2012年5—10月份),(1)土壤呼吸呈现明显的季节变化,施氮对生长季土壤总呼吸、异养呼吸无显著影响,而对自养呼吸有显著的抑制作用(P<0.05)。(2)土壤呼吸也存在显著的日变化,施氮对一天中土壤总呼吸及其组分均有显著影响(P<0.001)。总体上,施氮促进了土壤总呼吸、异养呼吸,而抑制了自养呼吸。(3)施氮对土壤总呼吸、异养呼吸平均每月排放CO2通量无显著影响,而对自养呼吸平均每月排放CO2通量有显著的抑制作用(P<0.05),并在不同月份对土壤呼吸及其组分的影响不同。(4)土壤总呼吸、异养呼吸与地下5 cm土壤温度之间具有较好的指数关系(P<0.001),而与土壤含水量相关性较弱。关于土壤呼吸各组分对大气氮沉降响应差异的机理有待进一步研究。展开更多
文摘Plant derived natural fibers have been widely investigated as alternatives to synthetic fibers in reinforcing polymers.Researchers over the years have explored many plant fibers using different extraction processes to study their physical,chemical,and mechanical properties.In this context,the present study relates to the extraction,characterization,and optimization of Typha angustata L.stem fibers.For this purpose,desirability functions and response surface methodology were applied to simultaneously optimize the diameter(D),linear density(LD);yield(Y),lignin fraction(L),and tenacity(T)of Typha stem fibers.Typha stems have been subjected to both alkali(NaOH)and enzymatic(pectinex ultra-SPL)treatments.Three levels of process variables including enzyme concentration(10,15,and 20 ml/L)and treatment duration(10,15,and 20 days)were used to design the experiments according to the factorial design.Experimental results were examined by analysis of variance and fitted to second order polynomial model using multiple regression analysis.The Derringer’s desirability function released that the values of process variables generating optimized diameter,linear density,yield,lignin ratio and tenacity are 20 ml/L and 20 days for concentration of pectinex ultra-SPL enzyme and treatment duration,respectively.Confirmation was performed and high degree of correlation was found between the experimental and statistical values.Moreover,the morphological structure has been investigated by the scanning electron microscope,showing a crenelated structure of ultimate fiber bundles of cellulose composing the Typha fiber.Compared to Typha stem non-treated fibers(TSNTF),Typha stem combined treated fibers(TSCTF),brings to improve mechanical properties.This change in mechanical properties is affected by modifying the fiber structure showing alpha cellulose of(66.86%)and lignin ratio of(10.83%)with a crystallinity index of(58.47%).
文摘氮(N)是陆地生态系统初级生产力的重要限制因子,大气N沉降的增加将会对植物的化学元素含量和生物量产生重要影响,进而影响凋落物的化学计量特征及其养分归还。高寒灌丛是陆地生态系统的重要组成部分,但有关N沉降对高寒灌丛凋落物尤其是凋落枝的化学元素和生物量的研究还较为缺乏,难以深入揭示N沉降对高寒灌丛土壤碳(C)和养分循环的影响机理。基于此,以青藏高原东部地区的优势高寒灌丛类型—窄叶鲜卑花(Sibiraea angustata(Rehd.)Hand.-Mazz.)灌丛为研究对象,连续4年人工模拟N沉降,分析了凋落枝C、N、磷(P)、木质素和纤维素化学计量特征及其归还量对不同N添加浓度(0、20、50、100 kg hm^(-2)a^(-1))的响应趋势。结果表明:(1)N添加对凋落枝C、N含量无显著性影响(P>0.05),而对P、木质素和纤维素含量有显著性影响(P<0.05),但不同年份间的影响趋势不一致;(2)4年的N添加并未改变凋落枝的C/N、N/P,但显著降低了凋落枝的木质素/N(第3年)、C/P(第1年和第4年)和C/N/P(第1年);(3)随着N添加浓度的增加,凋落枝C、N、P、木质素和纤维素4年累积归还量呈显著的二次方变化趋势(P<0.05),并在中N处理(50 kg hm^(-2)a^(-1))下达到最大。研究认为,N添加对凋落枝化学计量特征的影响具有较大的年际变异,短期、适当的N添加通过增加凋落枝的生物量而并非改变其化学计量特征促进了凋落枝碳和养分的归还。
文摘开展土壤呼吸对大气氮沉降增加的响应研究对预测陆地生态系统碳循环具有重要意义。采用外施氮肥模拟氮沉降,结合壕沟法分离土壤呼吸组分,研究青藏高原东缘主要的灌丛类型——窄叶鲜卑花(Sibiraea angustata)灌丛土壤呼吸对不同施氮水平(N0(对照)、N2、N5和N10分别相当于0、2、5和10 g N m-2a-1浓度的氮沉降)的短期响应。结果表明:试验期间(2012年5—10月份),(1)土壤呼吸呈现明显的季节变化,施氮对生长季土壤总呼吸、异养呼吸无显著影响,而对自养呼吸有显著的抑制作用(P<0.05)。(2)土壤呼吸也存在显著的日变化,施氮对一天中土壤总呼吸及其组分均有显著影响(P<0.001)。总体上,施氮促进了土壤总呼吸、异养呼吸,而抑制了自养呼吸。(3)施氮对土壤总呼吸、异养呼吸平均每月排放CO2通量无显著影响,而对自养呼吸平均每月排放CO2通量有显著的抑制作用(P<0.05),并在不同月份对土壤呼吸及其组分的影响不同。(4)土壤总呼吸、异养呼吸与地下5 cm土壤温度之间具有较好的指数关系(P<0.001),而与土壤含水量相关性较弱。关于土壤呼吸各组分对大气氮沉降响应差异的机理有待进一步研究。
