桐粮间作林带的配置方式与农作物产量关系的研究

以桐粮间作为例,研究了林带的不同配置结构、林带冠覆盖率及小麦产量之间的关系。结果表明,林带距（Ｘｄ）、小麦相对产量（Ｙ）及间作年（Ａ）之间的关系为：Ｙ＝９０．３２９０－１．９９８２Ａ＋１．１９２４Ｘｄ－０．３３４９Ａ＾２＋０．２９１０ＡＸｄ－０．００３２ＡＸｄ＾２;林带冠覆盖率（Ｘｃ）与小麦相对产量（Ｙ）之间的关系为：Ｙ＝－０．０４６Ｘｃ＾２＋１．１５３９Ｘｃ＋９８．１７３（Ｘｃ≤２８％）,Ｙ＝ｅ     

农桐复合系统林带结构优化模式的研究

以麦桐复合经营为例,研究了林带的不同配置结构、林带覆盖率与小麦产量之间的关系,并通过一系列数学方法实现了林带结构的优化．结果表明,在一个轮伐期内,泡桐林带覆盖率累计均值为１０．１％～１０．９％时,小麦相对产量累计均值最大（１０５．４）,为最优林带覆盖率累计均值．最优林带距（Ｄ）与轮伐期（Ｔ）之间的关系为：Ｄ＝０．６００＋１１．０４２Ｔ－０．７８７Ｔ２＋０．０２７３Ｔ３（Ｒ２＝９９．９％）．     

灌草与林带搭配条件下防护效应的数值模拟

在对林带和灌草进行参数化的基础上,将有、无灌草带存在情况下绕林带流场进行了数值模拟,分析比较了两种流场中沿流相对风速、不同断面风速廓线及湍动能的变化。结果表明,灌草在防护林体系中起着重要作用,在林带迎风面和带后一定区域内,均使风速减小。最后将数值模拟结果与实验结果进行了对比,并从实验角度分析了灌草的作用。     

林带中阻力分布的理论与实验研究

推导了风向垂直于林带走向时林带内的阻力分布的解析式,比较了３种所面形状林带的阻力分布特点,并用风洞实验资料进行了验证,简析了在实际生产中的应用．     

杨树林带生长阶段与林木分级的研究

依据林带的特殊性,结合树木生长发育和林带结构变化规律,将林带生长阶段划分为幼龄期、中龄期（速生期）和防护成熟期３个时期;采用径级离散度、防护成熟龄、更新龄等量化指标,以杨树林带为例,将３个生长时期定量化;同时依据林带树木对防护效益的贡献和树木的生长状况,将林带树木划分为４级;并给出各生长发育时期的相应的经营措施．     

辽宁省清原县森林资源结构及其空间优化配置

利用RS、GIS技术和多目标灰色局势决策方法,综合森林的经济效益指标(生物量、林分生产力)和生态效益指标(涵养水源量、固土量),对清原县现有森林类型进行空间优化配置.结果表明: 经优化配置后,清原县森林类型的结构比例发生了明显的变化,其中针叶林和阔叶林面积由43%、51%减少到23%、31%,针阔混交林面积由3%增加到43%,灌木林面积保持不变;森林生态系统生物量、林分生产力分别增加0.6%、2.1%,而涵养水源功能增加31.7%,固土功能基本保持不变,在保留较高木材生产效益的同时,可充分发挥涵养水源功能,实现森林生态系统经济效益和生态效益的最大化.     

基于累积耗费距离理论的石羊河流域水土资源优化配置

选择干旱内陆河石羊河流域为研究区,以流域内水资源和土地资源利用优化为目标,依据累积耗费距离理论,采用最小累积阻力表面(MARS)和耗费距离表面(MCR)模型,借助表面扩散技术,研究了流域水土资源类型间进行能量交换、传递的阻力大小和耗费阻力空间分区,并进行了空间统计分析。结果表明:石羊河流域代表水土资源的生态核心源为河网、其他水域、耕地和建设用地4类,其中建设用地累积耗费阻力值最大,对生态系统能量流动和传递阻碍作用最大,河网累积耗费阻力值最小;根据水土资源配置方法和分区原则可划分为5种类型:重点优化配置区、有待优化配置区、重点关注区、关注区、生态治理与保护区。需要进行水土资源优化配置的区域在重点优化配置区,这些区域集中在绿洲核心区,且承载了85%以上的城镇和人口,因此要扩大绿洲边缘区以防止外围荒漠逼近,绿洲与荒漠交接区要大力植树造林,提高水源涵养能力并减少耗水作物种植,使抗生态风险能力进一步提高。     

牧民定居后季节草场优化配置的研究

草地畜牧业季节草场在牧民定居后新的生产力水平下应采取怎样的利用模式,是生产中亟待解决的问题。本文采用调查与实测相结合的方法,遵循草畜平衡及能物流高效持续利用原则,研究提出了新疆天山北坡中段季节草场时空优化配置模式(暖季放牧,冷季舍饲 放牧)。此模式不仅实现了草畜平衡,使生态环境得以保护和改善,且能取得显著的经济和社会效益。     

闽东山区鼠类群落的空间配置和结构的研究

1984年3月-1985年1月对闽东山区鼠类群落的调查结果表明,根据鼠种类和数量组成,该区可划分为针毛鼠+社鼠;黑线姬鼠+黄毛鼠、黄毛鼠+黑线姬鼠;褐家鼠+小家鼠+黄胸鼠等4个鼠类群落。不同鼠类群落的组成和数量有不同的季节变化。本文比较了不同鼠类群落的多样性指数、均匀性指数和相对生物量。     

麻阳铜矿植被组成特征及优势种植物铜含量

对麻阳铜矿的Cu矿脉地表露头区、废弃采坑口、矿洞塌陷区和Cu矿石矿渣散落区进行土壤和植被调查,旨在筛选潜在的金属型植物。结果表明,土壤总Cu含量和DTPA提取态Cu含量分别为3250和393mg·kg-1,而Zn、Pb和Cd含量相对较低。共计录到28科47属54种植物,其中菊科、禾本科、豆科、蓼科植物共27种。头花蓼(Polygonum capitatum)、酸模(Rumex acetosa)和地枇杷(Ficus tikoua)是上述生境中的优势植物,其地上部Cu含量分别为120、203和133mg·kg-1,生物富集系数介于0.01～0.1。表明,麻阳铜矿土壤高Cu含量是影响植物自然定居的主要限制因子;3种优势植物可能以低积累或排异型的方式适应高Cu含量土壤,可以作为候选金属型地被植物用于重金属污染土壤的植物稳定或绿化。     

农田防护林可持续集约经营模型的应用

选择具有典型代表的辽宁北部平原区、河北坝上农牧交错区和渭北旱塬区农田防护林为研究对象,以主栽树种杨树林带为研究材料,针对每个特定类型区的主要自然灾害因子和防护目的,统计分析调查研究数据,确定了辽宁北部、河北坝上和渭北旱塬3类型区农田防护林可持续集约经营模型的最优经营参数.其中林带最适疏透度分别为0.25～0.35、0.20～0.30和0.275～0.375;主林带间距分别为450～500m、200m和200～250m;副林带间距分别为500～1000m、500m和350～450m;林带带面宽度分别为8m、9m和4.5～8m;林带行数分别为3～4、6和2～4;林带树木株行距分别为2m×1.5～3m、1.5m×1.5m和1.5～3m×1.5～3m,主栽树种的防护成熟龄分别为15～16a、14～15a和12～14a;防护成熟期分别为10a、10～11a和12～14a;最佳更新方式分别为隔带更新、半带嫁接更新和隔带更新.     

东北地区农田防护林高效多功能经营的指标体系及标准研究

从单条林带和林网两个尺度出发,建立了农田防护林高效多功能经营的指标体系,并通过分析各个指标之间的机理关系,提出了9个主要评价指标,对于单条林带,用林带疏透度,有效防护距离,初始防护成熟龄,防护成熟期,林带产投比,更新方式等可作为度量林带经营状态的指标;对于林网体系,用林网带斑比,林网连接度,环度,林网优势度等可作为度量林网经营状态的指标;依据主要指标的数量化界定,提出了农田防护林高效多功能经营的标准,可进行综合评价,这些评价指标及其标准,在宏观上确定了主要林网体系的布局,在微观上确定了单条林带的结构,成为衡量是否可持续经营的依据,为其高效多功能经营提供了导向。     

Temporal and spatial patterns in littoral-zone fish assemblages of a reservoir (Lake Texoma,Oklahoma-Texas,U.S.A.)

Synopsis We sampled the littoral-zone fish fauna of Lake Texoma reservoir by electrofishing from January through December 1986 to examine species abundance, species associations and assemblage structure. Although total fish abundance differed significantly across seasons, only one common species (Dorosoma cepedianum) exhibited significant seasonal movement into or out of the littoral zone. Overall littoral-zone assemblage structure (based on rank order of species abundance) was concordant across seasons and habitat types, (vegetation, wood, open). However, within individual seasons and habitat types, assemblage structure was likely influenced by temporal and spatial differences in habitat availability and physicochemical conditions. Associations characteristic of species in natural aquatic environments were not well developed among species in this partly artificial, evolutionarily short-lived reservoir assemblage. Conditions related to water-level fluctuation appeared to deter the formation of persistent species associations and assemblage structure, especially in vegetation and open littoral zone habitats of this multi-purpose reservoir.Senior author     

TESS3: fast inference of spatial population structure and genome scans for selection

Geography and landscape are important determinants of genetic variation in natural populations, and several ancestry estimation methods have been proposed to investigate population structure using genetic and geographic data simultaneously. Those approaches are often based on computer‐intensive stochastic simulations and do not scale with the dimensions of the data sets generated by high‐throughput sequencing technologies. There is a growing demand for faster algorithms able to analyse genomewide patterns of population genetic variation in their geographic context. In this study, we present TESS3 , a major update of the spatial ancestry estimation program TESS . By combining matrix factorization and spatial statistical methods, TESS3 provides estimates of ancestry coefficients with accuracy comparable to TESS and with run‐times much faster than the Bayesian version. In addition, the TESS3 program can be used to perform genome scans for selection, and separate adaptive from nonadaptive genetic variation using ancestral allele frequency differentiation tests. The main features of TESS3 are illustrated using simulated data and analysing genomic data from European lines of the plant species Arabidopsis thaliana.     

择伐对思茅松自然种群结构和空间分布格局的影响

思茅松是云南省重要的材脂兼用树种,而择伐是思茅松天然林管理的有效手段,也是获取木材的重要途径。基于对云南省景谷县思茅松天然林的样地调查数据,采用种群径级结构代替年龄结构、Ripley的L函数点格局等方法,对思茅松天然林在不同强度择伐10a后的种群结构和空间分布格局及其不同发育阶段在不同尺度下的相互关系进行了系统研究和分析。结果表明:择伐10a后3种类型的思茅松自然种群的胸径、树高之间呈显著的正相关且可用幂指数模拟预测模型。未择伐的思茅松种群呈衰退型,轻度择伐(12.9%)后种群呈稳定型,中度择伐(29.3%)后的种群属增长型,适当的中度择伐有利于自然种群的更新;未择伐与中度择伐后的思茅松种群分布格局整体呈随机型,但后者较前者更趋向于均匀分布,轻度择伐后的思茅松种群分布格局随着尺度的增加由随机转向聚集分布。择伐对不同径级思茅松天然林种群空间分布格局有重要影响,未择伐的思茅松自然种群随着发育阶段的发展,多数尺度上由随机分布逐渐转变为聚集分布,至大树则又以随机分布为主;轻度择伐和中度择伐的思茅松自然种群则随着发育阶段的发展而由完全的随机分布逐渐转变为聚集分布,中度择伐的聚集分布则更为明显。思茅松不同发育阶段间在所有尺度上基本都呈显著正相关,表明思茅松种群种内竞争弱,有利于种群的维持。     

Immobilized Marasmius oreades agglutinin: use for binding and isolation of glycoproteins containing the xenotransplantation or human type B epitopes

The type B-specific lectin from the mushroom Marasmius oreades was immobilized onto Sepharose 4B. The immobilized lectin bound murine laminin and bovine thyroglobulin, glycoproteins that contain the Galalpha1,3Galbeta1,4GlcNAc epitope. This epitope is responsible for hyperacute rejection of xenotransplants from lower mammals to humans, Old World monkeys, or apes. The immobilized lectin also bound a fraction of serum proteins from type B human serum but little or none from type A or O(H) serum. The major protein bound from human B serum was a portion of the alpha2-macroglobulin. Treatment of this fraction with N-glycosidase F resulted in decreased molecular weight of bands associated with alpha2-macroglobulin and loss of their M. oreades lectin reactivity, whereas on treatment with coffee bean alpha-galactosidase, this bound fraction also lost reactivity with M. oreades lectin but became reactive with Ulex europaeus I lectin, suggesting the presence of L-fucosyl-alpha1,2-terminated structures. The presence of blood group epitopes on alpha2-macroglobulin has been detected previously by immunological methods, but this is the first isolation and characterization of the specifically glycosylated fraction of this serum protein. The immobilized lectin also bound a number of proteins from pig, rabbit, and rat serum that were distinct in electrophoretic mobility from the human B-serum components and presumably contain the xenotransplantation epitope among their glycan structures. This report further demonstrates the utility of immobilized lectins in isolating and characterizing glycan structures of naturally occurring glycoproteins.     

Conformational Studies of Nucleic Acids I. A Rapid and Direct Method for Generating Furanose Coordinates from the Pseudorotation Angle

Abstract

The greatest difficulty in modeling a nucleic acid is generating the coordinates of its furanoses. This difficulty arises from constraints imposed by the closed ring geometries of these sugars. We have developed a new method for modeling these furanose rings. Using this method, the coordinates of a sugar can be obtained quickly and unambiguously for any point on the pseudorotational pathway from one parameter: the phase angle of pseudorotation P. The significant difference between this and previous sugar modeling schemes is that here the endocyclic bond lengths of the five-membered sugar ring are allowed to vary a small amount according to simple, explicit, and experimentally reasonable analytic functions of P. The coefficients of these functions follow from the empirical behavior of the endocyclic bond angles and from geometrical constraints due to ring closure. The ability to model the sugars directly from one parameter greatly facilitates carrying out the global conformational studies on nucleic acid constituents which will be attempted in subsequent papers of this series.     

Two criteria for the comparison of multiple arrangements of experiments and their use to answer the question: Is it better to compare p treatment groups with p controls or with a single control

In experimental situations examining the effectiveness of p(p>1) treatments by comparing treated groups and untreated controls the following question arose: Which experimental arrangement is more appropriate, an arrangement A₁ using for the p comparisons only one single control, or an arrangement A₂ using for every comparison another control. To answer this question two criteria are formulated. The first criterion takes into consideration the expected numbers of type I and type II errors, and the second criterion the probabilities of type I and of type II errors. According to the first criterion A₁ and A₂ do not differ, generally. According to the second criterion A₁ with the comparison of means of normal distributed variables is better than A₂. Pooling of all p controls is better than A₂ according to both criteria. A₁ is better also according to the often used experimentwise type I error rate. The formulated criteria have some analogy to those of MILLER (1966). It may be possible to use them not only for comparing experimental arrangements but also tests.     

Model for the three-dimensional structure of vitronectin: predictions for the multi-domain protein from threading and docking.

The structure of vitronectin, an adhesive protein that circulates in high concentrations in human plasma, was predicted through a combination of computational methods and experimental approaches. Fold recognition and sequence-structure alignment were performed using the threading program PROSPECT for each of three structural domains, i.e., the N-terminal somatomedin B domain (residues 1-53), the central region that folds into a four-bladed beta-propeller domain (residues 131-342), and the C-terminal heparin-binding domain (residues 347-459). The atomic structure of each domain was generated using MODELLER, based on the alignment obtained from threading. Docking experiments between the central and C-terminal domains were conducted using the program GRAMM, with limits on the degrees of freedom from a known inter-domain disulfide bridge. The docked structure has a large inter-domain contact surface and defines a putative heparin-binding groove at the inter-domain interface. We also docked heparin together with the combined structure of the central and C-terminal domains, using GRAMM. The predictions from the threading and docking experiments are consistent with experimental data on purified plasma vitronectin pertaining to protease sensitivity, ligand-binding sites, and buried cysteines.