狗牙根根系分布特征及其抗拉强度试验研究

以狗牙根为研究对象,就狗牙根根系在土壤中的分布及其抗拉强度进行了初步研究。结果表明,根系密度及根系重量随土层深度(0—40 cm)的增加而减少,其规律均服从指数函数关系分布;根系抗拉力随直径增大而增大,其分布规律均可用二次函数进行拟合;根系的平均抗拉强度为39.349 MPa,约为Ⅰ级钢筋抗拉强度的17%,能产生显著的根系"加筋作用",抗拉强度随直径增大而减小,其规律服从指数函数关系分布。根据狗牙根根系分布特征及抗拉强度特性,其固土护坡作用较大。     

Considering sink strength to model crop production under elevated atmospheric CO2

Climatic changes and elevated atmospheric CO₂ concentrations will affect crop growth and production in the near future. Rising CO₂ concentration is a novel environmental aspect that should be considered when projections for future agricultural productivity are made. In addition to a reducing effect on stomatal conductance and crop transpiration, elevated CO₂ concentration can stimulate crop production. The magnitude of this stimulatory effect (‘CO₂ fertilization’) is subject of discussion. In this study, different calculation procedures of the generic crop model AquaCrop based on a foregoing theoretical framework and a meta-analysis of field responses, respectively, were evaluated against experimental data of free air CO₂ enrichment (FACE) environments. A flexible response of the water productivity parameter of the model to CO₂ concentration was introduced as the best option to consider crop sink strength and responsiveness to CO₂. By varying the response factor, differences in crop sink capacity and trends in breeding and management, which alter crop responsiveness, can be addressed. Projections of maize (Zea mays L.) and potato (Solanum tuberosum L.) production reflecting the differences in responsiveness were simulated for future time horizons when elevated CO₂ concentrations and climatic changes are expected. Variation in future yield potential associated with sink strength could be as high as 27% of the total production. Thus, taking into account crop sink strength and variation in responsiveness is equally relevant to considering climatic changes and elevated CO₂ concentration when assessing future crop production. Indicative values representing the crop responsiveness to elevated CO₂ concentration were proposed for all crops currently available in the database of AquaCrop as a first step in reducing part of the uncertainty involved in modeling future agricultural production.     

瞬时拉力下两个生长期4种植物单根抗拉力与抗拉强度的研究

研究3～4年生柠条、沙柳、沙地柏和白沙蒿的单根(根径为0.3～3 mm)在两个生长时期内瞬时大风作用下的抗拉力和平均抗拉强度.结果表明,在生长季初期(5月初)和旺盛生长期(8月中旬),4种植物根系的单根抗拉力与直径均呈幂函数正相关关系;抗拉力和平均抗拉强度均表现为柠条＞沙柳＞沙地柏＞白沙蒿;沙柳、沙地柏、白沙蒿在生长季初期的抗拉力和平均抗拉强度大于旺盛生长期,柠条反之.     

Conversion of a tropical forest into agroforest alters the fine root-related carbon flux to the soil

Large areas of remaining tropical forests are affected by anthropogenic disturbances of various intensities. These disturbances alter the structure of the forest ecosystem and consequently its carbon budget. We analysed the role of fine root dynamics in the soil carbon budget of tropical moist forests in South-east Asia along a gradient of increasing disturbance intensity. Fine root production, fine root turnover, and the associated carbon fluxes from the fine root system to the soil were estimated with three different approaches in five stands ranging from an old growth forest with negligible anthropogenic disturbance to a cacao agroforestry system with planted shade trees. Annual fine root production and mortality in three natural forest sites with increasing canopy openness decreased continuously with increasing forest disturbance, with a reduction of more than 45% between the undisturbed forest and the forest with large timber extraction. Cacao agroforestry stands had higher fine root production and mortality rates than forest with large timber extraction but less than undisturbed forest. The amount of carbon annually transferred to the soil carbon pool through fine root mortality was highest in the undisturbed forest and generally decreased with increasing forest use intensity. However, root-related C flux was also relatively high in the plantation with planted shading trees. In contrast, the relative importance of C transfer from root death in the total above- and below-ground C input to the soil increased with increasing forest use intensity and was even similar to the C input via leaf litter fall in the more intensively managed agroforest. We conclude that moderate to heavy disturbance in South-east Asian tropical moist forests has a profound impact on fine root turnover and the related carbon transfer to the soil.     

FACE对三系杂交籼稻汕优63根系活性影响的研究

2005、2006年利用我国惟一的农田开放式空气CO2浓度增高（FACE）研究平台,设计施N量为125kg·hm^-2（LN）、250kg·hm^-2（NN）处理,研究大气CO2浓度比对照高200umol·mol^-1的FACE处理对三系杂交籼稻汕优63根系活性的影响。结果表明：（1）FACE处理使汕优63不同生育时期单位干质量根系的总吸收面积、活跃吸收面积、α-萘胺氧化量等根系活性指标均极显著小于对照。由于FACE处理促进汕优63根系发生量的大幅度增加,因此分蘖期、拔节期其单穴根系活性与对照多无明显差异,到抽穗期FACE处理单穴根系活性显著大于对照;（2）拔节期、抽穗期汕优63每穴的不定根数、不定根总长度、根系体积、根干质量与单位干质量根系活性的关系密切,根量越大单位于质量根系活性越低;（3）不同生育时期汕优63植株含氮率与单位干质量的根系活性多呈正相关,植株碳氮比与单位干质量的根系活性多呈负相关;（4）FACE处理汕优63根系生长量大、植株含氮率低、碳氮比高等可能是造成其单位干质量根系活性低于对照的重要原因。     

不同退耕年限撂荒地植物多样性及生物量分析

退耕还林(草)作为黄土高原水土流失综合治理的主要生态建设措施,经过几十年的开展,黄土高原生态环境得到极大恢复,林草覆盖率明显增加。以安塞县纸坊沟流域为研究区,选取坡耕地(0a)为对照,研究了退耕年限(3～5,10,18,28,37a)对撂荒地植物多样性和生物量的影响。结果表明,随退耕年限的延长,物种丰富度指数、多样性指数、均匀度指数、相同土层根长密度都表现为增大—减小—增大的趋势;植被盖度和地上生物量表现为37a>28a>18a>3～5a>10a>0a;撂荒地植被根系生物量、根长密度均随土层深度增加而减少;不同退耕年限撂荒地,相同层根系生物量表现为28a>37a>18a>3～5a>10a>0a。     

不同干燥方式对全蛋粉冲调性能的影响

为提高全蛋粉的品质和冲调性能,采用热风干燥,真空冷冻干燥、微波干燥、喷雾干燥和红外干燥对鲜蛋液进行干燥制粉,研究不同干燥方式对全蛋粉营养成分和润湿下沉性、水合能力、溶解指数、结块率及稳定系数等冲调性能关键评价指标的影响.结果表明:喷雾干燥全蛋粉的营养成分保留率最高,冲调性能最好,其中润湿下沉时间为198.24 s、水合...     

硒的价态与浓度水平对6种植物种子发芽和根际生长的影响

本文研究了硒的价态（Se6＋和Se4＋）和浓度水平（0～100mgSe·L-1）对6种植物（大麦、小麦、花椰菜、萝卜、苜蓿和欧芹）种子萌发和根际生长特性的影响。结果表明,低浓度硒（〈1mgSe·L-1）对种子发芽促进作用不明显,而高浓度硒（〉4mgSe·L-1）则有显著抑制作用,不同种子对硒的抗性表现不同。根长和芽长的测定结果表明,低浓度对花椰菜和小麦种子生长具有显著促进作用,对欧芹种子表现出抑制作用。较高浓度（1～4mg·L-1）即对花椰菜、苜蓿和欧芹的根生长表现出抑制作用,高浓度对小麦、大麦和萝卜根生长有抑制作用,且使芽生长受到抑制的硒浓度高于根生长。比较价态,低硒时六价对花椰菜生长的促进作用显著高于四价,高硒时小麦和苜蓿对硒的抗性表现为六价硒强于四价硒,其余科属差异不显著。不同科属对硒的抗性为禾本科小麦和大麦最强,十字花科花椰菜和萝卜次之,豆科苜蓿较差,伞形科欧芹最差。     

岩溶区典型根系地下生境的土壤质量分析

选择岩溶区三种不同的典型根系地下生境类型土壤为研究对象(类型Ⅵ——白云岩水平产状多层空间类型、类型Ⅸ——白云岩倾斜产状多层空间类型及类型Ⅺ——白云岩直立产状多层空间类型),根据不同类型的土壤物理、化学及生物学指标,计算土壤肥力的综合指标值,对其土壤质量进行综合分析评价。结果表明:(1)不同植物根系地下生境类型和不同空间土壤层次的土壤指标值差异极显著;(2)不同类型的土壤质量存在差异,且具有明显的层次性,土壤质量表现为白云岩倾斜产状多层空间类型最好,且三种类型的土壤质量均呈现出随土壤深度的增加而逐渐降低的趋势。该文揭示了根系地下生境的土壤质量差异,这为岩溶石漠化区的植被恢复技术研究和治理均有积极的作用。     

Response of Rice Seedlings to Copper Toxicity and Acidity

Metal toxicity and soil acidity affect plant growth. A hydroponic experiment was conducted to simulate effects of pH and copper concentration [Cu] on early growth and biomass production of high-yielding rice seedlings (Oryza sativa L. cv. ‘NIAB 6’). The rice seedlings were allowed to grow in Yoshida nutrient solution with 1 (control), 8, 16, and 32 μM Cu at buffered pH levels of 4.5, 5.0, and 5.5, respectively. Shoot and root growth, leaf chlorophyll content, and root lipid peroxidation and K⁺ leakage of 15-day-old rice seedlings were determined. Results show that [Cu] had significant adverse effects on rice seedlings. Shoot height and root length were reduced by 18%–60% and 7%–69%, respectively, compared with the control, and shoot and root weight decreased by 26%–56%, and 25%, respectively, in response to progressive increases in [Cu]. Similarly, leaf chlorophyll content decreased by 150%–245% compared with the control treatment. Rice seedling roots suffered from significant increases in lipid peroxidation followed by K⁺ leakage (> 8–23 times) in response to increasing [Cu]. Averaged across [Cu], seedling growth and biomass were greater at pH 5.5 than at other pH treatments. In some instances, increasing pH minimized the adverse effects of Cu at low concentrations on rice seedlings.