Leaf macro- and micro-morphological altitudinal variability of Carpinus betulus in the Hyrcanian forest (Iran)

We investigated the altitudinal variation of Carpinus betulus L. in the Hyrcanian forest using leaf macro-morphological and micro-morphological traits. We collected a total of 1600 leaves from two locations. In each location, we sampled six populations along an altitudinal gradient ranging from 100 m to 1,150 m. We found that trees in the higher elevations have smaller leaf lamina than those in the lower elevations. In contrast, leaf mass per area was high at low altitudes and increased newly at the higher ones. Stomatal dimension was negatively correlated with elevation, while stomatal density was positively correlated with elevation. We also found that two transects showed the same plasticity trend. Leaf area showed the highest plasticity, while the number of veins showed the lowest plasticity. This study shows that altitude, and related temperature and rainfall, represents an important driving force in Carpinus betulus leaf morphological variation. Moreover, our results suggest that leaf area, leaf mass per area and stomatal density could influence the species responses to different ecological conditions.     

Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin IV: Species dependency

Flat-sawn specimens of eight wood species, albizia (Paraserianthes falkata, 0.23 g/cm³), Japanese cedar (Cryptomeria japonica, 0.31 g/cm³), red lauan (Shorea sp., 0.36 g/cm³), European spruce (Picea abies, 0.44 g/cm³), Douglas fir (Pseudotsuga douglasii, 0.50 g/cm³), elm (Ulmus sp., 0.51 g/cm³), Japanese beech (Fagus crenata, 0.64 g/cm³), and Japanese birch (Betula maximowicziana, 0.71 g/cm³), were impregnated with low molecular weight phenol-formaldehyde (PF) resin and their compressive deformations were compared. The volume gain (VG) and weight gain due to 20% resin solution impregnation were different among species. Furthermore, the specific volume gain (VG/specific gravity), indicating the degree of swelling of the cell wall, also varied from 17.7% for European spruce to 26.4% for elm. Oven-dried specimens of each species were compressed using hot plates fixed to an Instron testing machine. The deformation behavior of resin-impregnated wood up to 10MPa was significantly different among the species. Stress development during cell wall collapse for low density wood was minimal. As a consequence, a significant increment of density occurred up to 2MPa for low density wood such as albizia and Japanese cedar. When PF resin-impregnated wood was compressed up to 2MPa and the pressure was kept constant for 30min, the density of Japanese cedar reached 1.18g/cm³, about 30% higher than the density of compressed Japanese birch, which possesses an original density that is 2.5 times higher than that of Japanese cedar. The mechanical properties of resin-impregnated wood, especially low density wood, increased with density. Hence, it is manifested that low density wood species have an advantage as raw materials for obtaining high-strength wood at low pressing pressure.     

Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin V: effects of steam pretreatment

This study evaluated the potential of steam pre-treatment for making highly compressed phenol-formaldehyde (PF) resin-impregnated wood at a low pressing pressure. Sawn veneers of Japanese cedar (Cryptomeria japonica) were first subjected to saturated steam at different steaming temperatures (140°-200°C), followed by impregnation with a 20% low molecular weight PF resin aqueous solution resulting in a weight gain of around 50%-55%. Four oven-dried treated veneers were laminated and compressed up to a pressing pressure of 1 MPa at a pressing temperature of 150°C and pressing speed of 5 mm/min, and the pressure was held for 30 min. Steam treatment, causing partial hydrolysis of hemicellulose, accelerated the compressibility of Japanese cedar in the PF resin-swollen condition. As a consequence, a discernible increment in density was achieved at a pressing pressure of 1 MPa due to steam pretreatment between 140° and 200°C for 10 min. It was also found that even a short steaming time such as 2 min at 160°C is sufficient for obtaining appreciable compression of PF resin-impregnated wood. The density, Young’s modulus, and bending strength of steam-treated (200°C for 10 min) PF resin-impregnated wood composite reached 1.09 g/cm³, 20 GPa, and 207MPa, respectively. In contrast, the values of untreated PF resin-impregnated wood composite were 0.87 g/cm³, 13 GPa, and 170MPa, respectively.     

车载电源多电动机测试平台耦合分析与解耦控制研究

为研究纯电动汽车车载电源性能在环测试,提出了由异步电动机-直流电动机组成的测试平台,是集机、电、磁于一体的复杂机电耦合系统。首先对该测试平台进行了机电耦合分析,建立了其机电耦合模型。根据α阶积分逆系统原理构建了伪线性系统,实现了对该复杂机电耦合系统的线性化。在此基础上,将自适应模糊神经网络与逆系统结合,构造出自适应模糊神经网络逆系统对原系统进行解耦控制。仿真和实验结果表明:自适应模糊神经网络逆系统控制取得了较好的解耦效果;异步电动机的反馈转速和直流电动机的反馈转矩均较好地跟踪了参考转速和参考转矩。此外,通过该测试平台可得到在整个循环工况中与异步电动机相连的电池电压、电流以及功率的变化曲线,为复合电源的在环测试提供了理论依据。     

Healing ability and diameter growth of lime-trees (<Emphasis Type="Italic">Tilia begonifolia</Emphasis> Stev.) following logging wounds

Lime-trees (Tilia begonifolia Stev.) have countless ecological and economical values in the northern forests of Iran. Bole wounds on residual trees are commonly caused by logging. The healing ability of bole wounds and the effect of bole wounds on diameter growth in lime-trees were assessed in a natural mixed uneven-age stand. The susceptibility to decay in relation to the wound severity was also evaluated. Condition and location of lime-trees before and after selective logging were determined through systematic plot sampling. The position of each lime-tree was identified on a topographical map using the global positioning system. After 10 years from wound occurrence, tree and wound characteristics were also re-measured. Overall, 68 stems (9.7 stem ha^?1) of lime-trees were found in the sampled area, 25 stems (36.8%) were damaged in the form of bole wound, and 43 stems (63.2%) were undamaged. Statistical differences between wounded or non-wounded lime-trees in terms of diameter and height were not found. Most of the wounds occurred at the height of < 1 m; the average wound size was 370.5 cm². Wound severity was related to wound size and wound position. Wound width healing rate was 6.2 mm year^?1. The wound shape was found to be a healing factor as the healing rate by width was higher than that by length. Healed wounds were only 12, 60% of bole wounds resulted in decay. Diameter growth of wounded trees was 43.5% lower than undamaged trees. The average annual diameter growth decreased by increasing wound severity. The results indicated the lime-tree is a very sensitive species to damage caused by logging (bole wound). Single-tree selection cutting needs more careful logging operations to reduce damage on residual lime-trees in order to safeguard this species, valuable in ecologic and economic terms.     

Time Prediction Models and Cost Evaluation of Cut-To-Length (CTL) Harvesting Method in a Mountainous Forest

Time equations are derived for felling with chainsaw, skidding with cable wheeled skidder, loading with grapple hydraulic loader and trucking of logs within a cut-to-length harvesting method. The continuous time study method was applied to collect data for felling, skidding, loading and a transportation model. Multiple regression analysis via SPSS software was applied to develop the time models. Felling time was found to be highly dependent on diameter at breast height. Skidding distance, winching distance, slope of the trail and piece volume were significant variables for the skidding time prediction model. The loading time model was developed considering piece volume. Transportation distance and load volume were used as independent variables in modeling the transportation time. The net production of felling was estimated at 12 trees/h (56.65 m³/h). The net production rates for skidding, loading and traveling averaged 18.51, 41.90 and 3.32 m³/h respectively. The total cost of harvesting from stand to mill was estimated 19.70 €/m³. The skidding phase was the most expensive component of the cut-to-length method. The bucking and delimbing components were less costly than the other logging phases. The results of this study can be used for harvesting planning and productivity optimization.     

Effects of silicon on the growth of maize seedlings under normal,aluminum, and salinity stress conditions

The effects of silicon on seed germination and growth parameters of maize seedlings under normal, aluminum (Al), and sodium chloride (NaCl) stress conditions were investigated. The results indicated a dose-dependent relationship between silicon and growth parameters, except for germination attributes.Application of silicon (2 mM) accelerated amylase activity, decreased abscisic acid content, and increased indoleacetic acid and gibberellic acid contents of seedling, The results suggest that the beneficial effects of silicon, at least in part, are mediated by the balance of phytohormones. Exposure to Al (10 mM) significantly decreased all growth parameters of maize seedlings. Application of 2 mM silicon, however, alleviated Al stress and restored almost all growth attributes. Decrease of Al absorption, increase of fructan content, and improvement of amylase activity were considered as the mechanisms of ameliorative function of silicon in Al-stressed maize seedlings. Exposure to silicon, however, did not show beneficial effects on growth parameters of maize seedlings under salt stress conditions.     

The effect of micronutrient foliar application on yield,seed quality and some biochemical traits of soybean cultivars under drought stress

Abstract

This experiment carried out as split plot factorial based on a randomized complete block design with three replications during two consecutive years (2015–2016). The main plot consisted of drought stress: complete irrigation, irrigation withholding at R1 stage, irrigation withholding at R2 stage and subplots included foliar application of micronutrients: distilled water (control), zinc sulfate, manganese sulfate and zinc sulfate?+?manganese sulfate and cultivar as: Williams and Zan elite. The results showed that proline and linoleic acid were increased significantly, but chlorophyll a and b, seed yield, protein percentage, oleic and linolenic acids were decreased significantly by irrigation withholding. Also, the maximum values of chlorophyll b, protein percentage and linolenic acid were achieved by Williams. The significant increasing effect of zinc was found on the maximum root and stem proline, chlorophyll b, and oleic, linolenic and linoleic unsaturated fatty acids, meanwhile the maximum leaf proline was obtained by manganese sulfate.