Red Pine seedlings were grown in the potted soils with different acidity (pH=4.5,5.5,6.5,7.5,8.0) to investigate their physiological responses to soil pH,and futher to evaluate the soil pH feasibility. Dramatic physio...Red Pine seedlings were grown in the potted soils with different acidity (pH=4.5,5.5,6.5,7.5,8.0) to investigate their physiological responses to soil pH,and futher to evaluate the soil pH feasibility. Dramatic physiological responses of Red Pine seedlings were detected under various soil pH treatments. Under soil pH 5.5,the seedling foliages grew best,with the lowest malondialdehyde content,ion leakage and soluble substance content,and the highest carotinoid content and antioxidant enzyme activities;With soil pH 7.5 and 8.0 treatments,the seedling needles developed poorest,with greater membrane lipid peroxidation and lower antioxidant enzyme activities,and the greater cell membrane injury and soluble substance content. Results suggested that Red Pine seedlings was mostly adapt to soil with pH of 5.5,followed by soils with pH of 4.5 and 6.5,and could hardly adapted to soil with pH of 7.5 and higher.展开更多
为了提高应用Sylvatest-Duo超声波测量装置进行木材质量和缺陷检测的精度,研究了该装置的探针与木材接触方式(探针触式)及其计示压强对木材中超声波传播速度和信号能量衰减幅度的影响,确定了测量过程中宜采用的最佳探针触式和最佳计示...为了提高应用Sylvatest-Duo超声波测量装置进行木材质量和缺陷检测的精度,研究了该装置的探针与木材接触方式(探针触式)及其计示压强对木材中超声波传播速度和信号能量衰减幅度的影响,确定了测量过程中宜采用的最佳探针触式和最佳计示压强。以美国红松Pinus resinosa的小规格试样材(25.4 mm×25.4 mm×407.0 mm)为研究对象,采用单因素重复试验,经SPSS统计分析中多元检验的研究结果表明:不同的探针触式对超声波测量结果影响显著(P值为0.000),探针-木材的"持续性接触"比"非持续性接触"测量偏差小,检测效果稳定;在探针"持续性接触"方式下,超声波的传播速度和信号能量衰减幅度随着计示压强增大而增加,在计示压强为275.8 k Pa(40 psi)时,两者趋于稳定。因此,建议在应用Slyvatest-Duo进行木材超声波测量过程中,宜保持探针与木材持续性接触,同时采用275.8 k Pa的计示压强,可达到最优检测精度。展开更多
Background:Many fire-dependent forests have experienced significant declines in species,structural,and functional diversity.These changes are attributed in part to traditional management approaches that were dominated...Background:Many fire-dependent forests have experienced significant declines in species,structural,and functional diversity.These changes are attributed in part to traditional management approaches that were dominated by even-aged regeneration methods such as clearcutting.Variable retention harvesting(VRH)is an ecologically based forestry practice that involves retention of some mature overstory trees and other biological structures in the postharvest stand to emulate the effects of natural disturbance events.In this study,we examined the effect of a VRH treatment on recruitment of historically dominant pine species and understory vegetation twoand six years after its implementation in a naturally regenerated mixed pine forest in the Upper Peninsula of Michigan,USA.Results:We found greater regeneration of red pine(Pinus resinosa L.)and eastern white pine(Pinus strobus L.)in VRH stands compared to the unharvested controls.Although red pine recruitment was very low during the first 2 years,both species increased significantly from year two to year six.Recruitment responses for the two species did not differ significantly between the aggregated and dispersed retention treatments.We also found high recruitment of deciduous tree species,consisting primarily of sprouts,and red pine exhibited a negative correlation with these sprouts.Treatment,time,and the interaction of treatment and time were significant factors in red pine recruitment.Time had a strong effect on the understory vegetation,with significant decreases in shrubs and ferns over time.Conclusions:The results suggest that VRH enhanced recruitment of red pine and eastern white pine and that this recruitment increased with time.We identify competition from sprouts and unfavorable seedbed conditions as the main factors that limited recruitment of red pine during the first 2 years.To reduce competing vegetation and improve seedbed conditions,we suggest following the VRH with a prescribed fire,mechanically removing sprouts,and implementing herbicide treatments.At a time when changes in global climate exacerbates the effects of traditional drivers of forest degradation,and with the need to maintain biodiversity,new ecologically based forest practices such VRH have the potential to facilitate regeneration of native trees and enhance the resilience of many fire-dependent forests.展开更多
文摘Red Pine seedlings were grown in the potted soils with different acidity (pH=4.5,5.5,6.5,7.5,8.0) to investigate their physiological responses to soil pH,and futher to evaluate the soil pH feasibility. Dramatic physiological responses of Red Pine seedlings were detected under various soil pH treatments. Under soil pH 5.5,the seedling foliages grew best,with the lowest malondialdehyde content,ion leakage and soluble substance content,and the highest carotinoid content and antioxidant enzyme activities;With soil pH 7.5 and 8.0 treatments,the seedling needles developed poorest,with greater membrane lipid peroxidation and lower antioxidant enzyme activities,and the greater cell membrane injury and soluble substance content. Results suggested that Red Pine seedlings was mostly adapt to soil with pH of 5.5,followed by soils with pH of 4.5 and 6.5,and could hardly adapted to soil with pH of 7.5 and higher.
文摘为了提高应用Sylvatest-Duo超声波测量装置进行木材质量和缺陷检测的精度,研究了该装置的探针与木材接触方式(探针触式)及其计示压强对木材中超声波传播速度和信号能量衰减幅度的影响,确定了测量过程中宜采用的最佳探针触式和最佳计示压强。以美国红松Pinus resinosa的小规格试样材(25.4 mm×25.4 mm×407.0 mm)为研究对象,采用单因素重复试验,经SPSS统计分析中多元检验的研究结果表明:不同的探针触式对超声波测量结果影响显著(P值为0.000),探针-木材的"持续性接触"比"非持续性接触"测量偏差小,检测效果稳定;在探针"持续性接触"方式下,超声波的传播速度和信号能量衰减幅度随着计示压强增大而增加,在计示压强为275.8 k Pa(40 psi)时,两者趋于稳定。因此,建议在应用Slyvatest-Duo进行木材超声波测量过程中,宜保持探针与木材持续性接触,同时采用275.8 k Pa的计示压强,可达到最优检测精度。
基金the Joint Fire Science Program(JFSP),The Ohio State University,Seney National Wildlife Refuge(SNWR)Seney Natural History Association.
文摘Background:Many fire-dependent forests have experienced significant declines in species,structural,and functional diversity.These changes are attributed in part to traditional management approaches that were dominated by even-aged regeneration methods such as clearcutting.Variable retention harvesting(VRH)is an ecologically based forestry practice that involves retention of some mature overstory trees and other biological structures in the postharvest stand to emulate the effects of natural disturbance events.In this study,we examined the effect of a VRH treatment on recruitment of historically dominant pine species and understory vegetation twoand six years after its implementation in a naturally regenerated mixed pine forest in the Upper Peninsula of Michigan,USA.Results:We found greater regeneration of red pine(Pinus resinosa L.)and eastern white pine(Pinus strobus L.)in VRH stands compared to the unharvested controls.Although red pine recruitment was very low during the first 2 years,both species increased significantly from year two to year six.Recruitment responses for the two species did not differ significantly between the aggregated and dispersed retention treatments.We also found high recruitment of deciduous tree species,consisting primarily of sprouts,and red pine exhibited a negative correlation with these sprouts.Treatment,time,and the interaction of treatment and time were significant factors in red pine recruitment.Time had a strong effect on the understory vegetation,with significant decreases in shrubs and ferns over time.Conclusions:The results suggest that VRH enhanced recruitment of red pine and eastern white pine and that this recruitment increased with time.We identify competition from sprouts and unfavorable seedbed conditions as the main factors that limited recruitment of red pine during the first 2 years.To reduce competing vegetation and improve seedbed conditions,we suggest following the VRH with a prescribed fire,mechanically removing sprouts,and implementing herbicide treatments.At a time when changes in global climate exacerbates the effects of traditional drivers of forest degradation,and with the need to maintain biodiversity,new ecologically based forest practices such VRH have the potential to facilitate regeneration of native trees and enhance the resilience of many fire-dependent forests.
