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971.
Evgenii Sharapov Christian Brischke Holger Militz Elena Smirnova 《Wood material science & engineering》2020,15(4):198-204
ABSTRACT An IML-RESI PD 400 drilling tool and a standard spade drill bit (IML System GmbH, Wiesloch, Germany) were used to study the combined effect of wood moisture content (MC), drill bit rotational speed and feed rate on drilling resistance (DR) and feeding force (FF). Tests were made with Norway spruce (Picea abies (L.) Karst.) conditioned in a normal climate (20°C/65% RH), at 20°C/95% RH, vacuum-pressure impregnated in water, and oven-dried. Rotational speeds and feed rates had an impact on feed rate per cutting edge for the major cutting edge of the drill bit which was used for correlation with DR and FF for various MC. Impact of MC on DR and FF depended on rotational speeds and feed rates of the drill bit. For feed rates per cutting edge less than 0.09?mm, DR was higher for water saturated (WS) specimens. Negligible differences between DR for various MC were found for feed rates per cutting edge between 0.09 and 0.15?mm. DR was higher at low MC for feed rates per cutting edge which were higher than 0.15?mm. FF extremely increased in conditioned (20°C/95% RH) and WS specimens at feed rates per cutting edge less than 0.1?mm. 相似文献
972.
几个沙棘品种抗逆性试验研究 总被引:1,自引:0,他引:1
根据寒温带半干旱地区的自然条件,选择耐盐碱性、耐寒性、耐水湿三项指标在温室盆钵内对HF-14、HF-4两个沙棘优良无性系及对照品种(楚伊)进行人工模拟抗逆性测定。其结果为:3个无性系对盐碱的耐受性均较强并无明显差别,可在中度以下盐碱地上栽培;3个无性系具有一定的耐旱能力,但在长期持续干旱条件下,生长量明显下降,生长势衰弱,增加感病机会,应给予灌溉,3个无性系的耐旱次序为HF-4>HF-14>楚伊;3个无性系对水湿条件的耐受力基本相同,在长期积水的条件下,根系不发育,生长受到抑制,栽植沙棘不应选择低洼内涝,排水不良的地块。 相似文献
973.
974.
975.
通过组织褐变法、膜脂脂肪酸含量分析和电导法配合Logistic方程求拐点温度的方法,对引种的4个种源抗寒力进行研究评价。结果表明:(1)印楝是一种不耐寒的植物,0℃以下的短暂低温可对其嫩叶造成伤害,低于-1℃保持1h即可造成部分幼苗死亡;(2)印楝种源间抗寒能力差异不显著;(3)叶膜脂脂肪酸组成含量与抗寒力大小无明显相关关系;(4)印楝4种源半致死温度分别为-1 651、-1 675、-1 750、-1 682℃。根据上述试验研究和冷冻处理实验结果,4个印楝种源抗寒力大小排序为IND95003>IND95004>IND95001>IND95002,在我国有低温寒害的地区引种印楝应该慎重,在轻霜地区可选择抗寒力稍强的IND95003种源先行试验性引种。 相似文献
976.
杨树微纤丝角的变异及其与木材性质的相关关系 总被引:6,自引:0,他引:6
微纤丝角为细胞次生壁S2层微纤丝排列方向与细胞主轴所形成的夹角,与木材的物理性质、力学性质和化学性质都有着直接的关系。应用x射线衍射法测定了7个杨树无性系(14株样木)胸径处各年轮的微纤丝角,并对应分析和测定了各年轮的木材基本密度、纤维长度、纤维宽度和纤维素含量。研究结果表明,杨树微纤丝角在年轮间存在显著差异,其径向变异规律为从髓心向外以微纤丝角逐渐降低,年轮间的平均微纤丝角在7.8旱?8褐洌荒静幕久芏取⑾宋ざ取⑾宋矶群拖宋睾吭谀曷旨湟泊嬖谙灾钜臁O喙胤治霰砻鳎⑾怂拷怯肽静幕久芏取⑾宋ざ取⑾宋矶群拖宋睾看嬖谙灾母合喙毓叵??0.01),相关系数分别为-0.450、-0.586、-0.516和-0.660。回归分析结果表明,多项式方程可较好地描述杨树微纤丝角与所测定的木材性质的关系,相关系数均在-0.45以上(n=125)。本文的研究结果认为,在今后针对杨树材性改良的育种计划中,微纤丝角是一个重要的选育和改良指标。图3表3参34。 相似文献
977.
Anita?Firmanti Bambang?Subiyanto Shinjiro?Takino Shuichi?KawaiEmail author 《Journal of Wood Science》2004,50(5):385-390
This study focused on the relationship between stress level and the fire resistance of structural lumber. The 210 samples were prepared from 15-year-old trees of Acacia mangium from the Forest Estate Plantation, Indonesia. Specimens were 20 ® × 20 (T) × 500mm (L) and were air-dried. Sixty samples were tested under four-point bending stress to obtain the modulus of elasticity (MOE) and the modulus of rupture (MOR) for classifying the stress grades of the remaining 150 samples. The tests were performed using a four-point load bending position at various stress level while the specimens were exposed to fire along the shear-free region. Time to failure was affected by the stress levels in an exponential trend. Despite changes in stress level, charring rate, and time to failure, the critical stress of a member from the same species was similar. The fire performance under applied load could be predicted by using simplified fire-testing methods. The developed testing apparatus is valid for evaluating the small-scale fire resistant behavior of structural lumber in bending. 相似文献
978.
Naoko?MikiEmail author Kosei?Otsuki Keiji?Sakamoto Takashi?Nishimoto Ken?Yoshikawa 《Journal of Forest Research》2003,8(3):153-161
To elucidate the differences in the leaf water relations of Pinus densiflora Sieb. et Zucc. growing in different soil moisture conditions, we examined the pressure-volume curve and the diurnal changes in the stomatal conductance, the transpiration rate, and the leaf water potential. The leaf water relations were compared using field-grown 40-year-old pine trees growing on the upper and lower parts of a slope. We also compared the leaf water relations of potted 4-year-old saplings growing at pF 4.2 and pF 1.8 soil moisture levels for almost 1 year. The values of the ratio of symplasmic water at turgor loss point to symplasmic water at saturated point (Vp/Vo) and bulk modulus of elasticity () of both the adult trees on the upper part of the slope and the potted saplings growing on pF 4.2 soil moisture were higher than those values of both the adult trees on the lower part of the slope and the potted saplings growing on pF 1.8 soil moisture, respectively. The field-grown adult tree and the potted saplings growing under long-term water stress tended to reduce their stomatal conductance in response to the acute soil drying. It is suggested that P. densiflora growing under long-term water stress rapidly closed its stomata in response to soil drying and avoided losing water, and could also rapidly absorb water with reducing water loss because of the decrease in the leaf pressure potential derived from the high values. 相似文献
979.
P.L. Mafongoya R. Chintu T.S. Chirwa J. Matibini S. Chikale 《Agroforestry Systems》2003,59(3):279-288
Seeking an alternative to Sesbania spp. tree fallows, a Tephrosia species and provenance trial was conducted at Msekera Research Station, Chipata (Zambia) to evaluate eleven Tephrosia vogelii and three Tephrosia candida provenances. They were tested for biomass production, quality of biomass, resistance to root-knot nematodes, nitrogen release,
and for their effects on soil nitrogen dynamics. At the end of 1.5 years, the T. candida provenances 02970, 02971 and 02972 from Madagascar produced two times greater amount of aboveground biomass than the T. vogelii provenances. There was little variability among the T. vogelii provenances in terms of litter and biomass production. Weed growth was significantly greater under T. vogelii than T. candida provenances. While Tephrosia vogelii provenance 98/02 from Zambia and T. candida 02972 were highly tolerant to the Meloidogyne incognita nematodes, T. vogelii provenances 02977, 98/03, 02973 from Kenya, Zambia and Malawi, respectively, were highly susceptible to the nematodes. The
Tephrosia species and provenances showed a wide variability in terms of N, lignin and polyphenol concentration in their foliage. Mineralization
of N in the foliage of T. candida provenances 02970 and 02971 and T. vogelii provenances 98/04 and 02974 from Malawi occurred rapidly within 14 weeks of incubation. At the end of the 2-year growth period,
there was significantly greater total inorganic N under T. candida provenance 02972 (12.5 mg kg−1) than T. vogelii (5 mg kg−1) provenance Mungwi 98/02. Maize (Zea mays L.) yields after T. candida provenances were greater than those after T. vogelii provenances. Further testing of the most promising provenances is needed for their effects on subsequent maize yields under
a range of farm conditions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
980.
低温引起杜鹃离体茎组织的伤害程度及其份害的可逆程度均取决于外界低温的胁迫强度和作用时间,以及受冻组织的耐寒能力。在低温处理过程中,杜鹃离体茎组织的细胞膜透性随温度下降而递增,这种变化明显地出现在外部形态变化之前,据此,可作为鉴别杜鹃品种抗寒力的依据。本试验中,不同杜鹃的抗寒力依次为迎红杜鹃>映山红>赛玉铃>无锡10F1。这与田间观察结果相一致。 相似文献