杉木竞争密度效果分析

用竞争密度（C－D）效果的倒数式分析了杉木的生长过程,随着时间的推移,C－D曲线在双对数图上向上移动,随着物理时间t的增加,生物时间被定义为逻辑斯蒂生长曲线中生长系数λ（t）的积分）倾向于增加到最大值,C－D效果倒数式中的系数A和B被求出,随着生物时间τ的增加,系数A急剧增加到最大值后下降,倾向于稳定在一个常数,而系数B呈指数下降,倾向于接近零,随林分的生长,6生长系数λ（t）倾向于下降。     

I-69杨竞争密度效果分析

用竞争密度效果的倒数式分析了I－69杨（Populus deltoids）的生长过程。随着时间的推移,C－D线在双对数图上向上移动。生物时间τ（τ被定义为逻辑斯蒂生长曲线中生长系数λ（t）的积分）与物理时间t的关系可以用双曲线方程表示。C－D效果倒数式（即1／w＝Aρ＋B,式中w和ρ分别代表平均单株材积和密度）中的系数A和B被求出。随着生物时间τ的增加,系数A急剧增另到最大值后逐渐下降。而系数B呈指数下降,倾向于接近零。随着林分的生长,生长系数λ（t）倾向于下降。     

环境和生物因子对黄河三角洲滨海湿地净生态系统CO2交换的影响

通过涡度相关和微气象观测技术,对黄河三角洲滨海湿地净生态系统CO₂交换(NEE)以及环境、生物因子进行了观测,探究湿地NEE变化规律及环境和生物因子对NEE的影响. 结果表明: 在日尺度上,生长季NEE呈明显“U”型曲线,非生长季变幅较小;在季节尺度上,NEE生长季波动较大,表现为碳汇,非生长季波动较小,表现为碳源;在年尺度上,滨海湿地生态系统表现为碳汇,总净固碳量为-247 g C·m^-2. 白天NEE主要受控于光合有效辐射(PAR),且生态系统表观量子产量(α)与白天生态系统呼吸(R_eco,d)均于8月达到最大值,最大光合速率(A_max)于7月达到最大值;夜间NEE随气温(T_a)呈指数增加趋势,生态系统的温度敏感系数(Q₁₀)为2.5,且土壤含水量(SWC)越高,Q₁₀值越大.非生长季NEE只与净辐射(R_n)呈显著的线性负相关,与其他环境因子无显著相关关系.生长季NEE与R_n、T_a、土壤10 cm温度(T_{s 10})等环境因子以及叶面积指数(LAI)呈显著的线性负相关,但与地上生物量(AGB)无显著相关关系.多元回归分析表明,R_n和LAI对生长季NEE的协同影响达到52%.     

环境和生物因子对黄河三角洲滨海湿地净生态系统CO2交换的影响

通过涡度相关和微气象观测技术,对黄河三角洲滨海湿地净生态系统CO₂交换(NEE)以及环境、生物因子进行了观测,探究湿地NEE变化规律及环境和生物因子对NEE的影响. 结果表明: 在日尺度上,生长季NEE呈明显“U”型曲线,非生长季变幅较小;在季节尺度上,NEE生长季波动较大,表现为碳汇,非生长季波动较小,表现为碳源;在年尺度上,滨海湿地生态系统表现为碳汇,总净固碳量为-247 g C·m^-2. 白天NEE主要受控于光合有效辐射(PAR),且生态系统表观量子产量(α)与白天生态系统呼吸(R_eco,d)均于8月达到最大值,最大光合速率(A_max)于7月达到最大值;夜间NEE随气温(T_a)呈指数增加趋势,生态系统的温度敏感系数(Q₁₀)为2.5,且土壤含水量(SWC)越高,Q₁₀值越大.非生长季NEE只与净辐射(R_n)呈显著的线性负相关,与其他环境因子无显著相关关系.生长季NEE与R_n、T_a、土壤10 cm温度(T_{s 10})等环境因子以及叶面积指数(LAI)呈显著的线性负相关,但与地上生物量(AGB)无显著相关关系.多元回归分析表明,R_n和LAI对生长季NEE的协同影响达到52%.     

过量施氮对冬小麦生产力的影响

设置0、70、140、210和280 kg N·hm ^-2 5个施N梯度, 对冬小麦(Triticum aestivum)旗叶光合速率(A_leaf)、群体冠层光合速率(A_canopy)、作物生长速率(CGR)和籽粒产量(GY) 4个生产力水平进行综合观测研究, 结果发现: 在0-210 kg N·hm ^-2区间, A_leaf、A_canopy、CGR和GY都随施N量的增大而增大; 在施N量由210增加到280 kg N·hm ^-2时, GY没有显著变化, 而灌浆期A_leaf、开花期和灌浆期A_canopy、开花-成熟阶段CGR有显著减小。综合分析认为: 1)过量施N (280 kg N·hm ^-2)能显著降低灌浆期冬小麦A_leaf、A_canopy和CGR, 进而抑制GY; 2)过量施N对冬小麦光合生产力的抑制作用主要发生在灌浆期; 3)在A_leaf、A_canopy、CGR和GY 4个生产力指标中, A_canopy对过量施N的反应最敏感。     

以松毛虫为基质培养的冬虫夏草菌丝体中多糖的提取研究

研究了不同方法对冬虫夏草发酵菌丝体（以枯叶蛾科昆虫马尾松毛虫为基质发酵所得）中多糖提取的影响。结果表明,采用微波辅助水提法所得多糖的产率最高,影响提取的关键因素为液料比、微波提取时间、微波功率;采用Box-Behnken设计及响应面分析法对这3个因素进行优化,并通过回归拟合,建立了预测虫草多糖提取的多项式模型Y=6.87+0.058A+0.085B+0.075C+0.032AB+0.046AC+0.069BC-0.16A²-0.37B²-0.11C²。经响应面最优化分析,获得冬虫夏草发酵菌丝体中多糖的最优提取工艺参数为：液料比（mL/g）6.3:1、微波功率520W、微波提取时间326s,此工艺提取验证后的提取率达到6.76%。     

黄土高原生物结皮对SCS-CN模型初损率的影响

水文模型是水文过程研究的有效工具,初损率(λ)是径流模型SCS-CN模型的参数,对模拟流域水文过程具有重要意义。为了确定生物结皮对λ的影响,提高该模型在黄土高原生物结皮广泛分布的退耕地的预测精度,本研究以陕西省定边县鹰窝山涧流域不同盖度的生物结皮坡面为对象,采用模拟降雨试验,分析土壤潜在最大入渗量(S)与实际入渗量(F)的关系,以及生物结皮盖度对λ的影响,并修订了λ;在此基础上,采用陕西省安塞县纸坊沟流域生物结皮径流小区的模拟降雨试验数据校验了参数修订后的模型。结果表明: 生物结皮坡面S与F的关系式为: S/F=2.5×60/T(其中T为降雨历时);模型参数λ与生物结皮盖度(C_BSC)呈极显著负相关关系,二者关系式为: λ=0.0791×e^{(-0.015×C_BSC}),R²=0.60;较λ取标准值,依生物结皮盖度修订λ后,SCS-CN模型Nash效率系数提高338.7%,合格率提升16.1%。研究结果为黄土高原生物结皮坡面λ的确定提供了科学依据,对准确评估黄土高原退耕还林(草)工程的水文效应具有重要意义。     

我国落叶松林生物量碳计量参数的初步研究

通过整理归纳落叶松(Larix)天然林和人工林的生物量文献数据,研究探讨了有关生物量碳计量参数,结果表明:1) 落叶松生物量转化与扩展因子(Biomass conversion and expansion factor, BCEF)的平均值为0.683 4 Mg·m^-3 (n=113, SD=0.355 1),其中天然林为0.555 1 Mg·m^-3 (n=56, SD=0.058 2),明显小于人工林的0.809 5 Mg·m^-3 (n=57, SD=0.465 0)(p<0.05);生物量扩展因子(Biomass expansion factor,BEF)的平均值为1.349 3 (n=134, SD=0.384 4),其中天然林为1.176 3 (n=63, SD=0.039 9),也明显小于人工林的1.502 9 (n=71, SD=0.478 0)(p<0.05)。天然林与人工林的BCEF和BEF随林龄(Stand age, A)、平均胸径(Diameter at breast height, DBH)和林分密度(Stand density, D)的增加呈现相反的变化趋势。天然林的BCEF和BEF随A和DBH的增加而增加,随D的增加而呈降低趋势。人工林随A和DBH的增加呈指数降低并趋于稳定值,随D的增加而呈增加趋势。2) 根茎比(Root∶shoot ratio,R)的平均值为0.245 6 (n=156, SD=0.092 6),其中天然林为0.237 6 (n=64, SD=0.061 8)),人工林为0.251 1 (n=92, SD=0.109 0),二者无明显差异(p<0.05)。天然林的R随A和DBH的增加分别呈明显的指数和幂函数增加,而随D的增加呈幂函数下降,而人工林的R与A、DBH和D没有显著相关性(p<0.05)。3) 群落生物量扩展因子(Community biomass expansion factor,CBEF)的平均值为1.079 2 (n=49, SD=0.100 5),其中天然林为1.103 9 (n=29, SD=0.114 9),明显大于人工林的1.043 4 (n=20, SD=0.061 4) (p<0.05)。由于天然林和人工林的某些碳计量参数(如BCEF、BEF、CBEF)间存在明显差异,在进行落叶松林生物量碳计量时需分别天然林和人工林计算,在使用有关参数时还需考虑A、DBH和D等因素,有利于降低计量中的不确定性。但是人工林的有些参数(如人工林BCEF和BEF与D的关系、天然林和人工林的CBEF等)尚需进一步研究。     

玉米地土壤呼吸作用对土壤温度和生物因子协同作用的响应

基于2005年玉米(Zea mays)生长季土壤呼吸作用及其影响因子的动态观测资料,分析了玉米地土壤呼吸作用的日和季动态及其对土壤温度和生物因子协同作用的响应。结果表明,玉米地土壤呼吸作用的日变化为不对称的单峰型,其最小值和最大值分别出现在6∶00~7∶00和13∶00左右;玉米生长季中,土壤呼吸速率波动较大,其均值为3.16 μmol CO₂·m^-2·s^-1,最大值为4.87 μmol CO₂·m^-2·s^-1,出现在7月28日,最小值为1.32 μmol CO₂·m^-2·s^-1,出现在5月4日。在土壤呼吸作用日变化中,土壤呼吸速率(SR)与10 cm深度土壤温度(T)呈显著的线性关系:SR=αT+β。在整个生长季节,玉米净初级生产力(NPP)与直线斜率(α)呈显著正相关,生物量(B)也明显影响直线的截距(β)。基于此,建立了玉米地土壤呼吸作用动态模型SR=(aNPP+b)T+cB²+dB+e。土壤呼吸作用季节变化的大部分(97%)可以由土壤温度、NPP和生物量的季节变化来解释。当仅考虑土壤温度对土壤呼吸作用的影响时,指数方程会过大或过小地估计了土壤呼吸强度。该文的结果强调了生物因子在土壤呼吸作用季节变化中的重要作用,同时指出土壤呼吸作用模型不仅要考虑土壤温度的影响,在生物因子影响土壤呼吸作用的温度敏感性时,还应该把生物因子纳入模型。     

坡度和植被盖度对粉砂质河岸带坡面流侵蚀水动力特征的影响

揭示坡面水流水动力参数特征对于深入了解坡面土壤侵蚀的内在机制具有重要意义.本试验在黄河下游河岸带原生坡面上,采用野外模拟径流冲刷的方法,研究了4个坡度(5°、10°、15°、20°)和3个植被盖度(0%、15%、30%)在特定放水量(15 L·min^-1)条件下坡面薄层水流剥蚀土壤的水动力学过程,分析了径流剪应力(τ)、水流功率(ω)、径流能量(F)等水动力学参数的变化及其对坡度、植被盖度以及二者交互作用的响应差异.结果表明: 在坡度和植被盖度的影响下,τ、ω和F变化规律明显,坡度不变情况下,τ随着植被盖度的增加而增加,ω和F随着植被盖度的增加而减小;植被盖度不变情况下,τ、ω和F均随坡度的增加而增加.坡度小于10°时,坡度和植被盖度的变化对坡面土壤侵蚀的影响不明显;坡度大于10°时,相同坡度条件下植被盖度越大减蚀效果越明显,相同植被盖度下坡面侵蚀量随坡度的增大而增加.τ、ω均与土壤剥蚀率呈显著的线性关系,在土壤侵蚀发生时均存在临界剪应力和临界功率;F与土壤剥蚀率则呈现良好的对数关系.双因素方差分析表明,坡度和植被盖度对τ、ω和F的影响显著,两者的交互作用对ω影响显著,但对τ、F的影响不显著.     

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.     

Gompertzian growth pattern correlated with phenotypic organization of colon carcinoma,malignant glioma and non-small cell lung carcinoma cell lines

Abstract. In the current study we present a Gompertzian model for cell growth as a function of cell phenotype using six human tumour cell lines (A-549, NCI-H596, NCI-H520, HT-29, SW-620 and U-251). Monolayer cells in exponential growth at various densities were quantified over a week by sulforhodamine B staining assay to produce cell-growth curves. A Gompertz equation was fitted to experimental data to obtain, for each cell line, three empirical growth parameters (initial cell density, cell-growth rate and carrying capacity – the maximal cell density). A cell-shape parameter named deformation coefficient D (a morphological relationship among spreading and confluent cells) was established and compared by regression analysis with the relative growth rate parameter K described by the Gompertz equation. We have found that coefficient D is directly proportional to the growth parameter K . The fit curve significantly matches the empirical data ( P  < 0.05), with a correlation coefficient of 0.9152. Therefore, a transformed Gompertzian growth function was obtained accordingly to D . The degree of correlation between the Gompertzian growth parameter and the coefficient D allows a new interpretation of the growth parameter K on the basis of morphological measurements of a set of tumour cell types, supporting the idea that cell-growth kinetics can be modulated by phenotypic organization of attached cells.     

The growth analysis of water hyacinth,Eichhornia crasipes solms,in different water temperature conditions

A 40-day culture experiment of water hyacinth was made in 4 different water temperatures, 15, 20, 25 and 30°C, which were combined with 4 levels of concentration of culture solution, 1/3, 1, 3 and 9-fold of the standard solution containing 28 ppm of totalN and 7.7 ppm of totalP. The optimum condition for obtaining the maximum plant growth shifted from 30°C: 3-fold condition in the early stage to 20–25°C: 3-fold condition in the later stages of the experiment. The relation between the fresh weight biomass per 100-l tank,w, and the concentration of culture solution,f, was expressed successfully by a reciprocal equation,1/w=A F/f+A F ^′f/(1-f/C F)+B F, in whichA f,A f′, andB f are time dependent coefficients andC f is the upper limit of the concentration to permit plant growth which can change with time. The relation betweenw and water temperature,T, was expressed by another reciprocal equation,1/w=A T/e ^aT+A T^′e^bT+B T, in whicha andb are constants andAt At′ andB t are time dependent coefficients. The latter formulation shows that the temperature can be breated as an exponential factor, and it suggests the possibility of the growth coefficient of the logistic growth equation, ψ, being affected by temperature.     

The effects of density and spatial distribution on selection for emergence time in Prunella vulgaris (Lamiaceae)

We investigated the effects of both overall density and variation in local density on the relationship between emergence time and final biomass in Prunella vulgaris. The relationship between emergence time and final biomass was used to quantify the pattern of selection on emergence time. Seeds were planted in flats in three different spatial distributions (hexagonal, random, high variance) at each of three overall densities (308, 769, and 3,077 seeds/m²). Individual seedlings were marked upon emergence, and their final biomass was determined after 90 days of growth. With increasing overall density, mean plant biomass decreased, but the coefficient of variation in biomass and the magnitude of directional selection for early emergence increased. Increasing variation in the spatial distribution of the plants had no effect on mean plant biomass but did significantly increase the coefficient of variation in biomass at both low and medium densities. Both the magnitude of directional selection and the curvature in the relationship between emergence time and final biomass tended to increase with increased variation in the spatial distribution. Our results suggest that both overall plant density and the spatial distribution of individuals can affect the pattern of selection on plant traits.     

Cell cycle parameters of slowly growing Escherichia coli B/r studied by flow cytometry

The cell cycle kinetics of Escherichia coli B/r A and B/r K cells were studied by flow cytometry. Three-dimensional histograms of cell cultures show the number of cells as a function of cellular DNA and protein contents and give detailed pictures of the cell cycle distribution with regard to these parameters. Histograms of slowly growing chemostat cultures showed that cell cycle periods B and C + D increase with a decreasing growth rate and that the B period occupies an increasing fraction of the cycle. The DNA replication patterns of B/r A and K were found to be quite similar. At extremely low growth rates (doubling time [T] = 17 h), B/r A cells had a B period of 0.8 T, a C period of 0.1 T, and a D period of 0.1 T, and B/r K cells (T = 16 h) had a B period of 0.6 T, a C period of 0.15 T, and a D period of 0.25 T. Mass increase, i.e., essentially protein synthesis, was seen in all three periods of the cell cycle. For B/r A cells, the average rate of mass increase was 11 times greater in the D period than in the B period, whereas for B/r K cells the rate of mass increase was twice as great in the D period as in the B period. The DNA and cell size distributions of batch cultures in exponential growth were found to vary with time, indicating that such cultures are not suitable for studies of cell cycle kinetics.     

Density effect, self-thinning and size distribution in Pinus densiflora Sieb. et Zucc. stands

The competition-density (C-D) effect for given times and self-thinning over time in even-aged, natural, pure stands of Pinus densiflora Sieb. et Zucc. were analyzed with the reciprocal equation of the C-D effect in self-thinning stands, and the equation describing the time-trajectory of mean stem volume and stand density. The C-D effect and self-thinning were consistently well explained by the two equations. Differences in mean stem volume and in stand density among the stands tended to merge with increasing stand age. The self-thinning line with a slope of approximately –3/2 was reached by the higher density stand prior to the medium and lower density stands. The skewness of tree height distribution showed positive values, which means that the distribution is more or less L-shaped, and in addition the skewness decreased with increasing mean tree height, which indicates that smaller trees died as the stands grew. This trend is consistent with the asymmetric (one-sided) competition hypothesis that self-thinning is driven by competition for light. The tree height distribution was analyzed using the Weibull distribution. The location parameter h _min of the Weibull distribution increased with increasing stand age, and the scale parameter a tended to increase slightly with increasing stand age. The range of the shape parameter b of the Weibull distribution corresponded to that of the skewness.     

不同精粗比底物下瘤胃真菌和纤维降解细菌共培养发酵特性及菌群变化

采用体外厌氧共培养技术,研究了瘤胃真菌和纤维降解细菌在不同精粗比(A组为全粗料,B组3∶7,C组5∶5,D组7∶3,E组为全精料)底物下菌群变化及其共培养发酵特性。结果表明:与0h相比,发酵至24h时B组和C组的厌氧真菌数量有较大幅度的上升,A组和D组则有所下降,E组未检测到真菌生长;纤维降解细菌随精粗比的增加呈上升趋势。发酵至48h时,各组均未检测到真菌生长;从A组到C组细菌数量呈上升趋势,此后急剧下降。DGGE结果表明,A、B和C组(精粗比低于5∶5)的DGGE图谱相似,有11条共有条带,但是当精粗比上升到7:3时,条带数目显著下降。随精料比例的增加,整个发酵期共培养系统中pH值显著下降(P<0.05)。整个发酵期间,共培养系统发酵产生的VFA主要为乙酸,丙酸和丁酸的量较少,乙酸与丙酸比值从A组到C组呈下降趋势,此后呈上升趋势。随精料比例的上升,发酵48h时总挥发性脂肪酸浓度从A组到C组呈上升趋势,此后呈下降趋势。发酵48h的羧甲基纤维素酶活和木聚糖酶活均以A组最高,而α-淀粉酶活从A组到D组逐渐增大,而E组最低,仅为B、C、D组的1/4~1/3。     

不同密度下沙地樟子松碳、氮、磷化学计量及养分重吸收特征

以樟子松纯林为对象,研究了6种密度(490、750、1110、1550、1930、2560株.hm-2)下不同器官(当年生叶、一年生叶、当年生枝、一年生枝和细根)的C、N、P化学计量特征及叶片N、P重吸收效率.结果表明:随着林分密度增加,当年生和一年生叶C含量及当年生和一年生枝P含量呈降低趋势(1550株.hm-2除外...     

Oscillatory behaviour and unsaturated fatty acid composition of diabetic liver mitochondria

Volume oscillations of liver mitochondria resulting from valinomycin induced K+ transport, may be represented by the equation At/Am = C'.exp(-beta t).sin(omega 1t+ psi) where At is the oscillation amplitude at time t; Am, the maximal amplitude; beta, the damping coefficient, omega 1 the oscillation frequency, and C' and psi, constants. The kinetic parameters beta and omega 1 increased as a function of valinomycin concentration. Measurement of beta and omega 1 for mitochondria from normal rats (A); diabetic rats (B), and normal rats fed corn oil or lard-supplemented diets (C and D, respectively), yielded an increase in beta (P less than 0.05) in B and D as compared with A, and a decrease in omega 1 in B and D as compared with A and C, respectively. Analysis of mitochondrial lipids revealed significant diminution of arachidonic acid and other polyenoic fatty acids in diabetic and lard-fed rats, as compared with normal rats and corn oil-fed rats, respectively. The conclusion is drawn that the abnormal oscillatory behaviour of diabetic liver mitochondria is related to the alteration of the membrane fatty acid composition.