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51.
以黑龙江省带岭林业局落叶松人工林为试验点,采用4种不同的采集作业模式,应用层次分析法,综合考虑作业成本、作业效率、保留木损伤、土壤干扰以及木材损耗5个指标,定量计算平缓坡和陡坡条件下不同采集作业模式的综合效益.结果表明:择伐-畜力集材作业模式是该类型伐区最适宜的作业模式. 相似文献
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竹材防腐防霉处理研究 总被引:4,自引:0,他引:4
本文论述了三种处理方法和七种防腐剂配方处理毛竹(片材)和浙江淡竹(竹竿)。气干材用热冷槽法和常压浸渍法,生材采用竹液置换法。这些方法很适合我国的国情。热冷槽法采用1.5小时热煮,48小时冷浸;常压浸渍20天左右;竹液置换法约8天,均能达到预期的药剂吸收量和透入度。此外,还进行了防腐处理竹材的室内抗霉试验和力学强度试验。野外抗腐试验正在进行中。 相似文献
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Xu Jun-liang Ma Lv-yi 《中国林学(英文版)》2007,9(4):251-255
In order to explore the relationship between the time processes of solar radiation and sap flow, sap flow velocity (SFV) of Platycladus orientalis and Pinus tabulaeformis, effective solar radiation (ESR) and other environmental factors were synchronously monitored for one year in the Beijing Western Mountains by using a thermal dissipation probe (TDP) system and an automatic weather station. Results showed significant differences between changes in diurnal characteristics of ESR and sap flow in sunny days during three seasons. Starting times of sap flow occurred generally 1.5–3 hours later than those of solar radiation and there were small differences between Platycladus orientalis and Pinus tabulaeformis. But peak times and stopping times of sap flow varied con-siderably with large contrasts in ESR. The duration of sap flow showed clear differences among the seasons owing to the variable rhythms of climate factors in Beijing. Fluctuation amplitude in the duration of sap flow remained relatively stable during the autumn but changed greatly during spring and summer. Changes in diurnal sap flow velocity of both Platycladus orientalis and Pinus tabu-laeformis were about 0–3 hours later than those of ESR but with the same configuration. The start of sap flow was mainly induced by the sudden intensification of ESR (sunrise effect). Seasonal models of SFV indicated that a cubic equation had the best fit. It was more practical to simulate seasonal water consumption models of trees with ESR. In further investigations, these models should be optimized. 相似文献
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Nitrification is the biological conversion of organic or inorganic nitrogen compounds from a reduced to a more oxidized state.
Denitrification is generally referred to as the microbial reduction of nitrate to nitrite and further gaseous forms of nitric
oxide, nitrous oxide and molecular nitrogen. They are functionally interconnected processes in the soil nitrogen cycle that
are involved in the control of long-term nitrogen losses in ecosystems through nitrate leaching and gaseous N losses. In order
to better understand how nitrification and denitrification change during the process of ecosystem restoration and how they
are affected by various controlling factors, gross nitrification rates and denitrification rates were determined using the
barometric process separation (BaPS) technique in subalpine coniferous forests of different restoration stages. The results
showed that forest restoration stage had no significant effects on gross nitrification rates or denitrification rates (One-way
ANOVA (analysis of variance), p < 0.05). There was no significant difference in the temperature coefficient (Q
10) for gross nitrification rate among all the forest sites (One-way ANOVA, p < 0.05). Gross nitrification rates were positively correlated with water content (p < 0.05), but not with soil pH, organic matter, total nitrogen, or C/N ratios. Denitrification rates in all the forest soils
were low and not closely correlated with water content, soil pH, organic matter, or total nitrogen. Nevertheless, we found
that C/N ratios obviously affected denitrification rates (p < 0.05). Results from this research suggest that gross nitrification is more responsible for the nitrogen loss from soils
compared with denitrification.
Translated from Journal of Plant Ecology, 2006, 30(1): 90–96 [译自: 植物生态学报] 相似文献
59.
观光木播种苗生长规律及育苗技术研究 总被引:3,自引:1,他引:3
用有序样本聚类分析法将观光木1年生播种苗生长过程划分为4个时期:出苗期(2月26日-5月20日)、幼苗期(5月21日-7月20日)、速生期(7月21日-10月20日)和生长后期(10月21日-11月20日)。不同播种期的试验表明:冬播观光木比春播提早16 d萌发,苗高、地径生长量和总生物量分别比春播提高13.3%、15.1%和18.8%。采用沙藏可促进种子提早萌发和提高场圃发芽率。不同密度试验表明,观光木育苗采用60株.m-2的密度较好。 相似文献
60.
在充分考虑数控车床加工表面特征的基础上,对以往仿真模型的不足进行了分析,提出了基于螺旋曲面的加工表面模型。该模型充分考虑了数控程序中主轴转速和进给速率两个重要参数,并提出了数控车床动态加工过程仿真的时间驱动机制。 相似文献