非洲菊切花保鲜剂的研究

本文研究由蔗糖、硝酸银、8-HQ(8-羟基喹啉)配制的不同保鲜剂对非洲菊切花插瓶寿命、水分平衡、鲜重变化及观赏值等指标的影响。结果表明：4％蔗糖 200mg／L硝酸银 200mg／L硫酸铝 320mg／L8-HQ的保鲜效果最好。     

土壤-植被系统演变对生物防沙工程的影响

包兰铁路横穿腾格里沙漠的沙坡头段 ,全长近 5 0km ,这里年降水量 186mm ,流动沙丘相对高度 2 0m以上 ,以 4m·a- 1 的速度向东南方向移动。无灌溉条件下、工程措施与生物措施相结合的防沙固沙工程体系始建于195 6年 ,近半个世纪以来该体系确保了包兰铁路的畅通无阻 ,累计经济效益逾百亿人民币。虽然当初的建设者充分考虑了耐旱的乡土树种、有效的工程固沙系统 ,但很难想到几十年后的土壤 -植被系统的演变会危及整个防护体系的稳定性。植被在从人工系统向自然系统的演变中经历了覆盖度从增加到减少的自疏过程、从灌木到半灌木到草本的变化 ,其降低风速和防风的功能减弱 ;土壤从流动风沙土发育成钙积旱成土 ,地表生物结皮发育 ,增加了表土的抗风蚀的能力 ;土壤 -植被系统的演变使得降水在生态系统中的再分配过程已经彻底改变 ,并由于防护林体系配置不完善 ,在 5 0～ 5 0 0cm的土层深度一个生物成因的干旱层逐渐形成 ,新的水分平衡格局明显威胁到现有的防风固沙体系。     

民勤绿洲荒漠过渡区辐射特征与热量平衡规律研究

根据巴丹吉林沙漠与腾格里沙漠交汇处的民勤绿洲荒漠过渡区的长期连续实测资料 ,分析了该地区的辐射特征 ,研究了热量平衡各分量的变化特征及热量平衡规律。在绿洲荒漠过渡区 ,其太阳辐射、净辐射和反射辐射具有明显的日进程和季节变化规律 ;太阳辐射月总量最大值 (12 0 2 3 3kW·m- 2 )出现在 8月份 ,最小值(5 2 0 6 5kW·m- 2 )出现在 11月份 ;流动沙丘表面的反射率高于有植被覆盖的红柳和白刺灌丛沙丘表面的反射率 ,在植被生长季节更为明显 ,反射率日最大值分别为流动沙丘 (37 5 % ) >白刺沙丘 (2 9 7% ) >红柳沙丘 (2 7 9% ) ;流动沙丘表面接受的净辐射是植被覆盖区的 5 0 %～ 70 %左右。在绿洲荒漠过渡区生态系统的热量平衡中 ,占比例最大的是潜热通量 ,其次为感热通量和土壤热通量。随着荒漠化程度的加深 ,生态系统反射率增加 ,净辐射减少 ,而且热量平衡中感热通量和土壤热通量所占比例增加 ,而潜热通量比例减小。     

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N₂ fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the ¹⁵N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg [N] ha^–1 yr^–1) originated from N₂ fixation. Grass production averaged 13 Mg ha^–1 yr^–1 and N export in cut grass was 195 kg [N] ha^–1 yr^–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha^–1 yr^–1. Carbon sequestration averaged 1.9 Mg [C] ha^–1 yr^–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha^–1 yr^–1, corresponding to 30% of N₂ fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha^–1 yr^–1) and litter decomposition (40 kg [N] ha^–1 yr^–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. This revised version was published online in June 2006 with corrections to the Cover Date.     

A split-root apparatus for examining the effects of hydraulic lift by trees on the water status of neighbouring crops

We describe a split-root system for examining the effects of hydraulic lift by trees on crop growth. In this system, upper lateral tree roots were grown in a container set on the ground through which the taproot of the tree could penetrate into the moist soil below. The container, with a radius of 0.5 m and a height of 0.20 m, consisted of two compartments divided by a waterproof barrier. A markhamia tree (Markhamia lutea (Benth.) Schumann) and upland rice (Oryza sativa (L.)) plants were planted in one compartment, with only rice plants planted in the other compartment. Irrigation of the container was ceased at the start of the experiment. The stomatal conductance of the rice plants in the associated side, in which both trees and rice plants were grown, declined more rapidly during the first drying period than in the rice-only compartment, suggesting that there was competition for water between the tree and the crop plants. However, during the later drying period, the rice plants in the associated side were green and viable, while those in the rice-only side became desiccated. Rice roots were seen intermingling with tree roots, and the soil water content in the associated site tended to be higher than in the rice-only side. It is likely that hydraulic lift occurred in the associated side and that water that had been transferred to the surface roots was released into the soil, enabling the rice plants in this compartment to remain viable. This novel system is useful for examination of the effects of hydraulic lift by trees on the growth of neighbouring crops. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparative water use by dryland trees in Parklands in Senegal

Despite the clear evidence of competition for water between trees and crops, there have been very few studies comparing simultaneous water use by differing tree species in drylands. Comparative water use by dryland trees was measured in Senegal using heat balance gauges at the end of the wet season and in the dry season. Significant differences between tree species were found for maximum rates of water use per unit leaf area. Indigenous species may be better adapted to the dry environment than exotic species but the indigenous species Acacia seyal Del. used more water per unit leaf area than all other species. The exotic species Azadirachta indica Adr. Juss. consistently used less water per unit leaf area than most other species. There were significant differences in amounts of water used per unit leaf area by differing provenances of the same tree species. Water use in the dry season varied by a factor of three between two provenances of Acacia aneura F. Muell ex Benth. indicating potential to select provenances for drylands based on their water use characteristics. Absolute rates of water use as well as differences in sapflow between species were greatest when soils were moist suggesting that comparative sapflow studies will be most informative when carried out during the wet season. Water use rankings of the differing tree species were broadly maintained irrespective of season.This revised version was published online in November 2005 with corrections to the Cover Date.     

Energy and carbon dioxide (CO2) balance of logging residues as alternative energy resources: system analysis based on the method of a life cycle inventory (LCI) analysis

Using the method of a life cycle inventory (LCI) analysis, the energy balance and the carbon dioxide (CO₂) emission of logging residues from Japanese conventional forestry as alternative energy resources were analyzed over the entire life cycle of the residues. The fuel consumption for forestry machines was measured in field experiments for harvesting and transporting logging residues at forestry operating sites in Japan. In addition, a total audit of energy consumption was undertaken. It involved an assessment of materials, construction, and the repair and maintenance of forestry machines as well as the costs associated with an energy-conversion plant. As a result, the ratio of energy output to input was calculated to be 5.69, indicating that the system examined in this study could be feasible as an energy production system. The CO₂ emission per MWh_e (e: electricity) of the biomass-fired power generation plant was calculated to be 61.8kgCO₂/MWh_e, while that of coal-fired power generation plants in Japan is 960kgCO₂/MWh_e. Therefore, the reduction in the amount of CO₂ emission that would result from replacing coal with biomass for power generation by as much as 3.0 million dry-t/year of logging residues in Japan was estimated to be 1.66 million tCO₂/year, corresponding to 0.142% of the national CO₂ emission. This study provides evidence that Japan could reduce its domestic CO₂ emission by using logging residues as alternative energy resources.     

Process studies in aPinus radiata-pasture agroforestry system in a subhumid temperature environment. I. Water use and light interception in the third year

In this study we determined soil moisture storage, evapotranspiration (ET) and light interception in an agroforestry trial consisting of pine trees grown over (1) control (bare ground), (2) ryegrass/clovers (Lolium perene/Trifolium spp.), (3) lucerne (Medicago sativa), and (4) ryegrass only during the third growing season between 1992 and 1993. The results show that:

The carbon budget of an adult <Emphasis Type="Italic">Pinus cembra</Emphasis> tree at the alpine timberline in the Central Austrian Alps

We investigated carbon (C) uptake and respiratory losses of an adult Pinus cembra tree at the alpine timberline throughout an entire year by means of an automated, multiplexing gas exchange system. These chamber measurements were then combined with biomass data for scaling up the C budget to the tree level. Integrated over an entire year, the cumulative C gain of the tree under study was 23.5 kg of C in 2002. The daily C balance was negative for 5 months and the estimated total wintertime respiratory losses were 9% of the amount of C fixed during the growing season. The total annual C loss of the tree consumed 55% of the annual net C gain and the remaining surplus was stored in new tissues (36%) and used for fine root growth (9%). Thus, the overall C budget of P. cembra at the upper timberline is balanced fairly well, although the C sink strength in fine roots is strongly limited owing to low root zone temperatures when compared to conifers at lower elevation sites.     

单株平衡法的建立

单株平衡法的建立孙长忠，黄宝龙（西北林学院林学系杨陵７１２１００）（南京林业大学南京２１００３７）关键词黄土高原，蒸腾量，蒸发量，单株平衡法，单株平衡方程，蒸发偏量在黄土高原地区，水分因素对植物生长及生存具有强烈的限制作用。研究植物生长与环境水分条件...