Simulated recruitment of riparian trees and shrubs under natural and regulated flow regimes on the Wisconsin River,USA

Models that link ecological responses to hydrologic changes are important for assessing the effects of flow regulation on aquatic and riparian ecosystems. Based on the Recruitment Box Model, a graphical model used to prescribe environmental flows for cottonwood (Populus spp.) recruitment, we designed a simulation model to represent the influence of river flow dynamics on seedling recruitment of riparian pioneer woody plants. The model simulates the influence of temporal patterns of river stage on dispersal, germination, initial recruitment and over‐winter survival of first‐year seedlings of riparian pioneer shrubs and trees. We used the model to simulate seedling recruitment patterns for five species (Acer saccharinum, Betula nigra, Populus deltoides, Salix nigra and Salix exigua) on the Wisconsin River (Wisconsin, USA) under three flow scenarios: historic (1935–2002), simulated natural (1915–1975) and simulated regulated flows (1915–1975). Simulation results agreed well with field‐observed relative differences among years (1997–2000) in seedling densities for the five focal species. Simulated successful recruitment years were highly synchronous among species, but species differed in their sensitivity to flows at different times during the growing season, consistent with among‐species differences in seed dispersal timing. Comparison of simulated natural and regulated flows for 1915–1975 showed that flow regulation decreased monthly flow variability, increased late summer to winter baseflow and reduced the magnitude of spring peaks. Simulated recruitment and over‐winter survival of tree seedlings of all species was enhanced under the regulated flow scenario, likely due to increased summer baseflow and reductions in peak flood magnitude. Our analyses show the utility of extending the Recruitment Box Model to include multiple species of riparian shrubs and trees, and the effects of post‐colonization flows on their recruitment success. However, some key functional relationships between flow patterns and woody seedling demography (e.g. shear stress thresholds for seedling mortality) have not been adequately quantified and merit further study. Copyright © 2006 John Wiley & Sons, Ltd.     

Alleviation Effect of Lanthanum on Cadmium Stress in Seedling Hydroponic Culture of Kidney Bean and Corn

Since1970s,rare earths(RE)have been exten-sively used as micro-fertilizers for crops in China.Ithas already been proved that REcani mprove the pro-duction and quality of crops.However,there havebeen a fewinvestigations about using RE as regulatorin pollution ecology.For example,An et al[1]studiedthe effects of O3on wheat growth and the protectiveeffect of RE.Yan and Zhou et al[2,3]discussed theprotective effect of RE on plants under acid rainstress.Jia et al[4]and Hu et al[5]reported th…     

基于电子鼻系统的番茄苗不同种类损伤的区分效果研究

通过对早疫病病害番茄苗、灰霉病病害番茄苗、机械损伤番茄苗和对照番茄苗的电子鼻响应信号的对比,可以看出不同处理的番茄苗样本电子鼻的响应信号是不同的,表明用电子鼻响应信号对番茄苗不同种类损伤进行预测是可行的.从PCA结果来看,早疫病病害的番茄苗和灰霉病病害的番茄苗能很好区分开,机械损伤的番茄苗和正常处理的番茄苗产生了重叠现...     

Persistence of nonprotein seed amino acid s-(β-carboxyethyl)-cysteine in young leaves ofCalliandra rubescens Ecological implications

The insecticidal nonprotein amino acid S-(-carboxyethyl)-cysteine (S-CEC) is the major free amino acid in the seeds of severalCalliandra spp. where it accounts for up to 2.9 % of dry weight. Lesser amounts of other related S-containing amino acids and an array of nonprotein imino acids derived from pipecolic acid are other constituents. High concentrations of imino acids, which also show insecticidal activity, are maintained in the mature leaves, but sulfur compounds are lacking. In this study the disappearance of S-CEC from the germinating seeds and young seedlings ofC. rubescens was monitored over time. After 10 weeks, S-CEC continues to be found in high concentrations in the stems and new leaves. As young leaves mature, sulfur compounds quickly decrease in concentration. Traces of S-CEC are found in new leaves of plants up to nine months after germination. Whether high concentration of S-CEC in young leaves is due to transportation from the seed or de novo synthesis is unclear. The ecological implications are discussed.     

Inhibitions of cotton seedling growth by volatile ketones emitted by cover crop residues

Low-input, sustainable agriculture (LISA) systems can include soil incorporation of residues of weeds and legume cover crop species. However, both seed germination and seedling growth of crops, including cotton (Gossypium hirsutum L.), are inhibited by volatile organic compounds emitted by these residues during decomposition. A cotton seedling-growth assay was used to demonstrate that C₄ through C₉ ketones released by decomposing legume residues significantly inhibited root and shoot elongation, root and shoot fresh and dry weight gain, and cotyledon expansion. Seedling root and shoot water relationships were relatively insensitive to those components of plant residue volatile emissions. Concentration (0.0, 0.5, 1.0, 1.5, or 2.0M/cm³ sterile greenhouse soil mix) and root-zone temperature (20 or 30°C) altered the activity of the more inhibitory ketones. Molecular weight (carbon chain length), carbon chain branching, and position of the carbonyl group also influenced ketone inhibitory activity.Mention of a commercial or proprietary product does not constitute an endorsement by the U.S. Department of Agriculture.     

生物农药防治玉米土传性病害药效的测定

采用美国生产的ＢＧ－２、Ｓｏｉｌｇａｒｄ两种生物农药和国内生产的生物型种衣剂（ＺＳＢ）对玉米茎腐病和纹枯病苗期和成株期的防治试验表明：两种生物农药均可在一定程度上防治茎腐病菌在苗期引起的根腐病,其中ＢＧ－２对镰孢菌的防治效果高达５５．１４％;Ｓｏｉｌｇａｒｄ对腐霉菌的防治效果达５５．５７％。ＢＧ－２对纹枯病的防治效果比ＺＳＢ好。田间试验表明：ＺＳＢ对纹枯病比对茎腐病的防治效果好。１：４０的种子包衣量为最佳。粉锈宁与ＺＳＢ混用比单独粉锈宁拌种防治茎腐病的效果好。     

油松容器苗生长和生理指标的主分量分析

本试验通过主分量分析,对油松(Pinus tabulaeformis)容器苗的质量指标从生长和生理两个方面进行了综合研究。结果表明:反映油松容器苗的质量指标不同于裸根苗;油松容器苗的质量主要决定于苗木顶芽的休眠状态,体内养分状况和根团的质量;苗木的地径、顶芽干重、可溶性糖的含量是反映容器苗质量的最重要的指标,根系活力、单株干重、地上和地下干重也是主要的指标;苗高、冠幅、主根长、侧根数、鲜重以及叶绿素含量对反映油松容器苗的质量不是有效指标。     

不同插秧量对东北杂交稻与常规稻产量结构的影响

对东北杂交稻与常规稻的产量形成过程和产量结构进行了分析。结果表明：杂交稻比常规稻增产的主要原因在于杂交稻的经济系数显高于常规稻，这主要得益于杂交稻后期光合产物向籽粒的转移率较高。在产量结构上，杂交稻的穗粒数多、千粒重大，但穗粒数的优势主要来源于二次枝梗，这也造成了杂交稻的结实率偏低，成为限制杂交稻产量潜力发挥的瓶颈。进一步发挥杂交稻的杂种优势，需要从提高后期光合能力和提高结实率两方面人手。杂交稻与常规稻有各自适宜的栽培方式，插单苗有利于提高杂交稻的平均穗重、千粒重、结实率，并最终使产量提高；而插3苗更适于常规稻生产力的发挥。     

穴盘播种器双轴协调控制系统的研究

摆臂和穴盘双轴协调控制是穴盘播种器的自动控制系统的关键。根据播种器的工作特性，设计了双轴系统合理的控制方案，针对摆臂的动作要求设计了严格的摆臂行程控制策略。运用实时性软件设计思想编写了系统控制程序，提高了控制系统的实时性。     

水稻气力抛秧原理与方案研究

在对国内外水稻钵苗移植机械综合分析的基础上提出了气力抛秧的原理，并进行了方案设计和研究。结果表明，气力抛秧原理是可行的，能有效地解决目前机械抛秧存在的问题。