同龄纯林密度效应新模型的研究

根据植物种群生物量增长模式和最终产量恒定理论,提出一种新的同龄纯林密度效应模型：V^-β=AN^β B。这里N和V分别为林分密度和平均单株材积;A、B、β分别是随生长阶段而变化的参数。采用杉木人工林密度试验材料进行验证,表明该模型能很好地拟合实际的观测资料,明显优于目前常用的密度效应倒数模型和二次效应模型,显示了较大的优越性和较高的准确性。在新的密度效应模型中,取β=1可得密度效应倒数模型,即密度效应倒数模型仅为本文新模型的一个特例。     

纯林自然稀疏研究综述

自然稀疏是林分内的个体由于部分有限的资源而引起的一部分个体死亡的现象。评述40a来世界上有关纯林自然稀疏的研究内容,包括了自然稀疏法则,异速生长模型、平均个体重与密度的时间轨线,种的自然稀疏线和自然稀疏动力线的关系,自然稀疏线的斜率与生物量的生物量的关系,自然稀疏的机理。     

白石砬子国家级自然保护区天然林的自然稀疏

以白石砬子自然保护区14个天然林为研究对象,利用近30 a间14次的连续定位观测数据,分析了各林分自然稀疏过程中Reineke方程指数β值的变化范围,阐明了β值恒定的机制与影响因素。结果表明,白石砬子自然保护区天然林随着林分密度的降低,林分平均胸径逐年提高;14个天然林中,平均胸径与林分密度的幂函数相关性均达到极显著水平,其中9个天然林的幂指数β值约为1.5;5个天然林β值变化范围较大,在0.44-1.80之间。对β值波动的5个林分进一步分析,1、9、56号林分受到明显的人为干扰;22、23号林分分别在林分密度较大和胸径生长量较高的时间范围内,β值约为1.5。在天然林的自然稀疏过程中,枯损林木呈左偏单峰状分布,大径阶木死亡数量较低,中小径阶的被压木死亡数量较大,形成了树木间的负反馈关系。综合本研究表明,白石砬子自然保护区天然林的自然稀疏是连续的过程,符合-3/2自疏法则,β值恒定,约为3/2;而β值是否恒定,与立地、树种组成等因素无关,与人为干扰有关;林木之间的负反馈机制是发生自然稀疏的根本原因,光是影响自然稀疏的主要因子。     

油松植物种群自疏规律模型的研究

根据植物生长的密度理论和有关生物学假设,推导出一种新的植物各自疏规律模型,即Ｎ＝ｅｘｐ（ａｌｎ＾２Ｂ＋ｂｌｎＢ＋ｃ）,这里Ｎ和Ｂ分别为种群密度和植物种群平均重量或平均胸高断面积,ａ,ｂ,ｃ为参数。将该模型应用于油松种群密度变化规律研究中,证明该模型能很好地拟合实际的观测资料,并且具有表达式简单等特点,因而,该模型是油松植物种群自疏规律的有效描述。     

格氏栲种群调节模型的研究

在前人对植物种群自然稀疏过程的研究基础上,结合自适应通用增长模型,推导出一种能描述密度变化全过程的理论模型,ｌｎＮ＝ａｌｎ＾２Ｓ＋ｂｌｎＳ＋ｃ,其中Ｎ和Ｓ分别为种群密度和单株基面积,ａ、ｂ、ｃ为参数。     

长白松自然同龄种群分布格局的研究

以长白松（Ｐｉｎｕｓｓｙｌｖｅｓｔｒｉｆｏｒｍｉｓ）种群为例,通过种群发展历史、种群大小结构研究,发现种群的胸径服从正态分布Ｎ（１６．８７,６．８０２）,确认该种群为自然同龄种群．种群的空间分布格局呈很高的均匀性,趋于随机分布甚至均匀分布,分布格局动态表现出由均匀分布向随机分布变化的趋势．     

民勤沙区人工梭梭林自然稀疏过程研究

通过实地样方调查,对民勤沙区人工梭梭林的自然稀疏过程进行分析,以探讨其自然稀疏机理。结果表明:(1)民勤沙区梭梭经过自然稀疏,15~32 a林龄的密度为387.14株.hm-2。(2)梭梭林内乔木、灌木、草本植物对不同层次土壤水分利用的分异比较明显,草本植物和灌木分别主要利用0~20 cm和0~100 cm的土壤水分,梭梭主要利用60~120 cm的土壤水分。(3)在梭梭林成长过程中,沙丘水分递减,梭梭因水分亏缺而自然稀疏化,且在10 a林龄以内自然稀疏过程最明显。(4)当林龄达到15 a以上时,植株普遍枯梢,生长不良,植株个体增大缓慢。(5)对于15 a及其以上成龄梭梭林进行人工补灌没有显著恢复效果,只是增加草本植物的密度和盖度。     

南京市不同纯林群落结构参数与夏季降温增湿效应关系研究

以往关于植物降温增湿效应主要基于绿带等大尺度测量和利用光合仪对叶片进行微观测量分析研究,模糊了植物群落结构差异的影响。该研究基于纯林群落的小尺度实测,采用stata虚拟变量回归分析法,探讨了降温增湿作用与群落疏透度、郁闭度的影响关系,并提出群落参数的最优阈值。结果表明:郁闭度和降温、增湿作用均呈显著的正相关,而疏透度和降温、增湿作用分别呈正相关和负相关,但影响都不显著。郁闭度在0.81~0.85,疏透度在0.31~0.35时,植物群落降温作用和增湿作用最优。同时,该文将树种类型作为一个相关因素,得出在降温作用上,枫香林和紫荆林的降温效果和广玉兰林相比无显著差异,而樱花林、鸡爪槭林、香樟林、红枫林的降温效果呈极显著性差异;在增湿作用上,桂花林、香樟林和红枫林的增湿效果和广玉兰林相比无显著差异,而乌桕、紫荆林的增湿效果差异显著。该研究结果为通过城市绿化建设缓解热岛效应的植物配置选择提供了科学依据,同时为城市绿地缓解热岛效应评价体系提供了量化的参考模式。     

日本落叶松人工林种群自然稀疏规律的研究

一、前言日本落叶松(Larix kaempferi)原产日本。种群地理分布范围为北纬35°20′—38°10′,东经136°45′—140°30′,海拔高度为1000—2800m。1900年引入我国,以其较强的适应性“定居”下来,而且生长速度在抚顺地区远比长白落叶松(L.olgensis var.changpaiensis)、兴安落叶松(L.gmelinii)为快;我国黑龙江、吉林、辽宁、山东、山西、陕西、北京、河南、河北、江西、湖北、四川以及新疆等地都有人工栽培,而以吉林、辽宁东部栽培面积较大,在年平均气温2.5—12.0℃、年降水量500—1400mm 的水热条件下能正常生长。     

杉木林自疏过程密度调节规律的研究

提出了森林自然稀疏过程中密度调节规律新模型,应用收缩扩张算法以山杨、云南松等树种森林自疏过程中密度资料对新模型进行了验证。验证结果表明：所提出的森林自疏规律模型能很好拟合实际的观测资料,具有良好的使用价值;所采用的非线性方程最优拟合方法是科学的,从而丰富了该领域的研究方法。交提出的森林自然稀疏过程密度调节规律模型应用于杉木林自疏过程密度变化规律研究,效果很理想,可为杉木林经营管理提供参考。     

黄河上游玛曲段春季浮游生物群落结构特征

为了了解黄河上游玛曲段的水质状况,于2006年4—5月对黄河玛曲段干流浮游生物的群落组成进行了调查。结果表明：全段的浮游植物共有5门23种（属）,浮游植物密度为3.2×10⁴～54×10⁴ cells·L^-1,平均密度为19.7×10⁴ cells·L^-1,生物量为0.069～0.464 mg·L^-1,平均生物量为0.228 mg·L^-1,其中密度最高的为齐哈玛,生物量最高的为玛曲大桥;浮游动物共有2门10种（属）,密度为670～1273 cells·L^-1,平均为881.56 cells·L^-1,生物量为0.044～0.089 mg·L^-1,平均为0.064 mg·L^-1;该河段浮游生物组成多以冷水性为主;浮游植物多样性指数介于2～3,表明黄河上游玛曲段水质呈轻度污染;浮游生物丰富度与均匀度值均较低,群落结构组成不稳定,易受外界环境的干扰。     

Density effects on organs in self-thinning <Emphasis Type="Italic">Pinus densiflora</Emphasis> Sieb. et Zucc. stands

Although much research on the density effect in nonself-thinning populations has been conducted, there has been very little research on density effects in self-thinning populations. Furthermore, the density effect of plant organs in self-thinning populations is little reported. The present study analyzed the yield–density (Y–D) effects on organs, such as stem, branch and leaf, together with that on stands of self-thinning Pinus densiflora Sieb. et Zucc.. The stand yield- and organ Y–D effects were well described by reciprocal and parabolic equations, respectively, throughout the experiment. The value of coefficient B in the reciprocal equation decreased monotonically with increasing stand age and became significantly closer to zero at the end of experiment (33-year-old stand), indicating that the constant final stand yield was established regardless of the density realized. The value of the relative growth coefficient h in the allometric equation between mean organ weight and mean aboveground weight was significantly smaller than 1.0 for stem, indicating that stem yield increases monotonically with increasing realized density. The h-value was significantly larger than 1.0 for branch throughout the experiment, and for leaf except at 33 years old, indicating that optimum densities exist. The h-value for leaf was not significantly different from 1.0 at 33 years old, indicating that the leaf yield reached a constant level regardless of realized density. The constant final leaf yield was established at almost the same growth stage as the establishment of constant final stand yield.     

Density effects and self-thinning in even-aged pure stands ofEucalyptus camaldulensis Dehn

The competition density effect and changes of mean total tree weight (w) and stand density (ρ) during course of self-thinning were examined in even-aged pure stands ofEucalyptus camaldulensis Dehn. which were planted in the tropical monsoon region. The level of competition was controlled by changing the initial stand density from 625 trees ha⁻¹ to 40,000 trees ha⁻¹. Hozumi's model was used to describe thew-ρ trajectory with aging of each stand and thew-ρ relation between stands of different densities at each time. The higher density produced trees of smaller mean tree sizes. The higher the density, the sooner self-thinning began. The growth curve ofE. camaldulensis followed the logistic growth curve where both maximum size and intrinsic growth rate change with time. Mean intrinsic growth rate was maximized at initiation of growth after lag time and then gradually decreased as time progressed. Hozumi's model was considered to be the best model with wide applicability for describing and comparing the growth characteristics during the course of self-thinning among different species, especially in tropical forest plantations, in which many diverse species were used for reforestation.     

马尾松林节肢动物群落的组成及多样性

在不采取任何营林和治虫措施的皖南九连山林场马尾松纯林中设林分相似的2块样地,面积均为22m×22m。1997年1月～1998年12月,每月1次垂直分层对两样地节肢动物群落的调查表明每样地植食性、捕食性、寄生性昆虫和蜘蛛类群的物种数占该样地总物种数的百分比分别约52%、14%、8%和20%;每样地的益害物种数之比都约为11.2;益害个体数之比是15.7和16.6;相同林间层次的优势目昆虫或优势种蜘蛛相同;每样地的物种数量都是以灌木草本层最多,依次为乔木层、枯枝落叶层和土壤层。两样地乔木层、灌木草本层、土壤层和枯枝落叶层的节肢动物平均个体数百分率分别为39.6%、33.1%、22.8%和4.6%。3～8月物种数和多样性指数较大,5、8月为物种数高峰期。主成分分析显示群落的稳定性较差。     

Optimisation of metric matrix embedding by genetic algorithms

Summary To improve the convergence properties of embedding distance geometry, a new approach was developed by combining the distance-geometry methodology with a genetic algorithm. This new approach is called DG-OMEGA (DG, optimised metric matrix embedding by genetic algorithms). The genetic algorithm was used to combine well-defined parts of individual structures generated by the distance-geometry program, and to identify new lower and upper distance bounds within the original experimental restraints in order to restrict the sampling of the metrisation algorithm to promising regions of the conformational space. The algorithm was tested on cyclosporin A, which is notorious for its intrinsic difficult sampling properties. A set of 58 distance restraints was employed. It was shown that DG resulted in an improvement of convergence behaviour as well as sampling properties with respect to the standard distance-geometry protocol.     

广义Schumacher模型的改进及其应用

通过对前人提出的生长方程的具体分析,提出了一种改进的Schumacher生长方程．该模型包含了Gompenz函数、Schumacher方程及广义Schumacher方程,具有很强的自适应性和实用性．采用遗传算法。利用该模型对珍稀植物长苞铁杉和侧柏生长资料分别进行了拟合．结果表明,改进的Schumacher方程的拟合精度明显优于Schumache,方程和广义Schumacher方程,也优于经典的Logistic模型和李新运等自适应模型。可以在林木生长动态模拟及种群增长动态研究中广泛应用．     

Study of the genetic code adaptability by means of a genetic algorithm

We used simulated evolution to study the adaptability level of the canonical genetic code. An adapted genetic algorithm (GA) searches for optimal hypothetical codes. Adaptability is measured as the average variation of the hydrophobicity that the encoded amino acids undergo when errors or mutations are present in the codons of the hypothetical codes. Different types of mutations and point mutation rates that depend on codon base number are considered in this study. Previous works have used statistical approaches based on randomly generated alternative codes or have used local search techniques to determine an optimum value. In this work, we emphasize what can be concluded from the use of simulated evolution considering the results of previous works. The GA provides more information about the difficulty of the evolution of codes, without contradicting previous studies using statistical or engineering approaches. The GA also shows that, within the coevolution theory, the third base clearly improves the adaptability of the current genetic code.     

广州白云山风景名胜区主要林分类型凋落物的研究

1　引　　言在森林生态系统功能的研究中 ,凋落物是重要的研究对象 ,历来受到重视[1～ 3 ,8] .凋落物是森林生态系统内物质循环的重要环节 ,是实现植物营养元素生物小循环的载体 ,是林地具有自肥功能的根本原因 .它还对森林资源的保护和永续利用以及水源涵养和水土保持有重要意义 .白云山是广州著名的风景名胜区 ,被誉为广州的“肺腑” ,对广州市的环境建设有举足轻重的作用 .由于白云山的林分供休闲游憩 ,不能施用有异味的有机肥和化肥 ,森林凋落物成为林分生长的重要养分来源 .因此 ,研究白云山主要林分类型的凋落物数量、季节动态、养分…