课堂教学提升大学生综合素质的对策分析

大学生素质的高低决定大学生是否成才,以及是否能够成功的走向社会.良好的大学生素质也是高校人才培养的目标.在高校教学中,教师在课堂上对大学生素质的培养至关重要,本文提出了教师在课堂上提高大学生心理素质、专业技能素质、道德素质和沟通素质的相应对策.     

海南岛尖峰岭热带山地雨林下层乔木中华厚壳桂光合生理生态特性的研究

2001年旱季,用Li 6400便携式光合测定仪对尖峰岭热带山地雨林下层乔木中华厚壳桂主要光合生理生态因子进行了初步测定,结果显示:冠层不同部位叶片的净光合速率无明显差异;中华厚壳桂具有较低的光饱和点(800μmol·m-2·s-1)、光补偿点(15～20μmol·m-2·s-1)和最大光合速率(≤7μmolCO2·m-2·s-1)等耐荫性光合特性,并且缺乏对高光强改变的光合调节能力,但对光斑却有快速的光合响应能力;短期内高CO2浓度会使其光合速率增加,但对气孔导度和蒸腾作用却有抑制作用;在光合最适温度范围内,温度的升高将明显促进光合作用,温度升高4℃能够使其净光合速率平均提高1 6倍,但一旦超过此范围,温度的升高却将抑制光合作用的进行。在自然条件下净光合速率与光照、温度、CO2浓度及气孔导度并无明显的相关关系,而在控制条件下却呈显著的曲线相关。     

祁连山主要植被下土壤对降雨分配的研究

以祁连山主要植被类型下的土壤为研究对象，对其物理性质、渗透率、渗流速度及其地表径流进行研究，结果表明：土壤的物理性质决定着土壤对降雨的分配情况，有林地将降雨全部分配成入渗水，而牧坡草地根据降雨强度和持续时间不同将降雨按不同的比例分配成入渗水和地表径流水2部分，不同植被的土壤蓄水量也各不相同。林地土壤100cm土层蓄水量为320．2～509．7mm，比牧坡草地高5．4％～60．47％，灌丛云杉和高山灌丛土壤蓄水量最高；轻度放牧的草地土壤蓄水量比强度放牧的高33．48％。     

Growth performance and management of a mixed rainforest tree plantation

Monoculture plantations of Pinus, Eucalyptus and Acacia have beenestablished on rainforest lands throughout the world. However, this type of reforestation generally supplies low quality timber and contributes to landscape simplification. Alternatives to exotic monoculture plantations are now beginning to gain momentum with farmers and landholders attempting to establish a variety of rainforest trees in small plantations. When compared to the well studied commercial species, knowledge concerning the growth and management of many of these rainforest species is in its infancy. To help expand this limited knowledge base an experimental plantation of 16 rainforest tree species in a randomised design was established near Mt. Mee, in south-eastern Queensland, Australia. Changes in growth, form (based on stem straightness, branch size and branchiness), crown diameters and leaf area of each species were examined over 5 years. Patterns of height growth were also measured monthly for 31 months. Species in this trial could be separated into three groups based on their overall growth after 5 years and their growth patterns. Early successional status, low timber density, high maximum photosynthetic rates and large total leaf areas were generally correlated to rapid height growth. Several species (including Araucaria cunninghamii, Elaeocarpus grandis, Flindersia brayleyana, Grevillea robusta and Khaya nyasica) had above average form and growth, while all species in the trial had considerable potential to have increased productivity through tree selection. As canopy closure occurred at the site between years four and five, growth increments declined. To reduce stand competition a number of different thinning techniques could be employed. However, simple geometric or productivity based thinnings appear to be inappropriate management techniques for this mixed species stand as they would either remove many of the best performing trees or nearly half the species in the trial. Alternatively, a form based thinning would maintain the sites diversity, increase the average form of the plantation and provide some productivity benefits.     

Leaf-litter decomposition of 15 tree species in a lowland tropical rain forest in Sarawak: dynamics of carbon,nutrients, and organic constituents

The effects of tree species on the dynamics of nutrient transformations during leaf-litter decomposition are not well understood in tropical rain forests. To examine differences in the dynamics of C, nutrients, and organic constituents during decomposition among tree species, the leaf-litter decomposition of 15 trees was assessed using a litter-bag method in a lowland tropical rain forest in Sarawak. The dynamics of C was parallel to that of weight loss. The dynamics of nutrients were grouped into three patterns. The dynamics of K was characterized by a high leaching loss in the initial stages, and that of Ca and Mg generally showed a gradual decrease over the course of decomposition. The dynamics of N and P showed highly different patterns with the weight loss, and was characterized by relatively higher remaining mass at the end of the experiment. The variations or exceptions of nutrient dynamics among tree species were considered to be related to the initial concentration of each nutrient. For the dynamics of organic constituents, water-soluble carbohydrates disappeared quickly at the initial stages, and acid-soluble carbohydrates were the second fastest decomposing fraction; the decomposition of acid-insoluble residue (AIS) was the slowest. The release of limiting nutrients (N and P) generally followed the disappearance of AIS, but was independent of the disappearance of AIS when the initial concentrations of these nutrients were very low.     

Promotion of the population growth of pinewood nematode in 4-month-old Japanese black pine seedlings by pretreatment with simulated acid rain

Simulated acid rain (SAR) at three pH levels (pH 4, 3, 2) was applied to only the top or both the top and roots of 4-month-old Japanese black pine seedlings repeatedly for two months. Then the seedlings were inoculated with a virulent isolate (S10) of pinewood nematode,Bursaphelenchus xylophilus. The exposure to SAR at any level did not kill the seedlings. When inoculated with nematodes, however, the nematode population build-up was significantly higher in the seedlings pretreated with SAR at any level than in the control at the 7th and 17th day after inoculation, and subsequent disease symptom development was also significantly accelerated by the exposure to SAR at pH 2 and 3. This result indicates that even acid rain at pH 4 has the potential for promoting population growth of pinewood nematodes in 4-month-old Japanese black pine seedlings.     

海南霸王岭热带山地雨林森林循环与群落特征研究

以海南霸王岭1hm^2热带山地雨林的网格样方调查数据为基础，首先对全林分的群落特征进行了分析，然后以森林循环理论为指导，研究了热带山地雨林的种群与群落特征。结果表明：热带山地雨林中不同生活型的树种在利用垂直和水平生态资源上是相对分离的，绝大部分的灌木或小乔木树种的水平生态位宽度较大，垂直生态位宽度较小，中、大乔木则正好相反，而那些低密度、稀有种的生态位宽度最小。随森林循环过程的进行，各树种在不同阶段斑块内出现的频度也会发生相应的变化。霸王岭热带山地雨林中占优势的乔灌木树种大都呈聚集分布的格局，个体数中等的树种大都呈均匀分布的格局，而那些个体数少的低密度种则大都呈随机分布的格局。随着森林循环过程的推进，每个树种所拥有的个体数和所占据的面积是逐渐减少的。森林循环不同阶段内的树种数随着个体数的增加呈现出逐渐减少的总趋势，尤其是由单个体和双个体所对应的物种数较多，3个以上个体对应的树种数则呈现出明显的下降。不同斑块之间组成相似性的大小在一定程度上表明了热带山地雨林森林循环斑块动态的连续性，相邻阶段斑块之间的相似性大于不相邻阶段斑块。以森林循环阶段为基础计算的生态位宽度表明，热带山地雨林中大部分低密度的树种或只集中分布在森林循环的少数阶段斑块内的树种对不同阶段斑块的生态资源利用较少，而那些在森林循环的不同阶段都出现，且个体数或断面积中等的树种，对森林循环不同阶段斑块的生态资源利用较大。     

Leaf-litter decomposition of 15 tree species in a lowland tropical rain forest in Sarawak: decomposition rates and initial litter chemistry

In a lowland tropical rain forest in Sarawak, leaf-litter decomposition and the initial litter chemistry of 15 tree species were studied. During 13 months of field experiment, weight loss of litter samples was between 44% and 91%, and calculated decomposition rate constants (k) ranged from 0.38 to 2.36 year⁻¹. The initial litter chemistry also varied widely (coefficients of variation: 19%–74%) and showed low N and P concentrations and high acid-insoluble residue (AIS) concentration. For nutrient-related litter chemistry, correlations with the decomposition rate were significant only for P concentration, C/P ratio, and AIS/P ratio (r _s = 0.59, −0.62, and −0.68, n = 15, P < 0.05, respectively). For organic constituents, correlations were significant for concentrations of AIS and total carbohydrates, and AIS/acid-soluble carbohydrate ratio (r _s = −0.81, 0.51, and −0.76, n = 15, P < 0.05, respectively). These results suggested that the relatively slow mean rate of decomposition (k = 1.10) was presumably due to the low litter quality (low P concentration and high AIS concentration), and that P might influence the decomposition rate; but organic constituents, especially the concentration of AIS, were more important components of initial litter chemistry than nutrient concentrations.     

石灰石粉施用量对重庆酸雨区马尾松林下木荷生长的影响

重庆是我国酸雨发生最早且其污染最严重的地区之一。由于长期遭受酸雨影响,这里的森林受害明显,经济和环境损失巨大。马尾松(Pinus massonianaLamb.)和木荷(Schima superbaGardn.etChamp.)都属于重庆的重要乡土树种,马尾松在造林中被广泛使用,木荷是优良的生物防火树种,并因     

近30年新疆降水量及雨日的变化特征分析

利用新疆1971-2006年98个气象站的逐日降水资料,研究了新疆年和四季降水量及雨日的气候变化特征。结果表明：新疆多年平均年降水量及雨日的空间分布均为北疆大于南疆,山区大于平原,二者长期变化的空间分布相似程度较低,有些地区甚至完全相反。南疆大部地区降水量的增加主要是由于雨日增加而造成的;北疆大部地区降水量的增加主要是...