ROOT PRODUCTION IN FOUR COMMUNITIES IN THE GREAT DISMAL SWAMP

A sequential coring approach was used to measure root biomass and production over 1 year in four different communities within the Great Dismal Swamp. A second method, an implanted bag technique, was also used to measure root production, and values were generally lower using this technique. On all sites, fine roots were the most dynamic root component. Both biomass (1,887 g/m²) and production (354–989 g m ² yr^-1) were highest on the mixed hardwood site, the least flooded site, and second highest on the cedar site, the site with the longest duration of soil saturation (1,033 g/m² and 274–366 g m^-2 yr^-1). The maple-gum (696 g/m² and 59–91 g m^-2 yr^-1) and cypress (824 g/m² and 68–308 g m^-2 yr^-1) sites had similarly low amounts of biomass and rates of production. Environmental parameters that influenced production include frequency and duration of flooding, and soil type. Peaks in belowground production were observed on the most productive sites (mixed hardwood and cedar) in summer and late fall-winter; the other two sites exhibited little seasonal variability. The least flooded stand appears to allocate a greater percentage of net primary production belowground than the more extensively flooded stands. The ratio of above- and belowground allocation appears to change in response to a flooding gradient. This has major implications for ecosystem functions as carbon allocation patterns determine the array of litter types generated (leaves vs. roots) which affect decomposition rates and nutrient availability.     

鼎湖山森林优势种群数量动态

本文分析研究了鼎湖山森林群落优势种群的数量动态,结果表明厚壳桂和黄果厚壳桂的增长曲线是与逻辑斯谛曲线相一致,椎栗的增长曲线则是一条近似的抛物曲线。拟合组建了种群增长方程(6)、(7)、(8)、(9)、(12),并论证了可信度及生态意义。     

暖温带落叶阔叶林辽东栎枝条分解过程中有机物质的变化

应用网袋法对暖温带地区广泛分布的乔木树种辽东栎（ＱｕｅｒｃｕｓｌｉａｏｔｕｎｇｅｎｓｉｓＫｏｉｄｚ．）枝条分解进行了连续５年时间的观察,并测定了凋落物在分解过程中有机质（纤维素、木质素、蛋白质）的变化。用Ｏｌｓｏｎ的指数方程对分解枝条重量的减少进行了模拟,并预测暖温带地区辽东栎枝条完全（９５％）分解需要约２１年的时间。在各有机成分含量的变化上,表现出明显不同的分异。蛋白质的含量随着分解过程的不断进行,从３．５％增加至５．５％,半纤维素则从１６．０％下降至８．０％,而粗纤维和木质素的含量出现了上下波动的情形。经过拟合,凋落物的丢失速率符合Ｏｌｓｏｎ的指数降解曲线,含量较大的粗纤维和木质素的减少也较好地符合Ｏｌｓｏｎ的指数降解曲线,半纤维素也可以用Ｏｌｓｏｎ指数方程拟合,但蛋白质的拟合效果较差。     

LITTER NUTRIENT CONTENT AND PRODUCTION IN THE GREAT DISMAL SWAMP

Litter production was studied in the Great Dismal Swamp, Virginia in four plant communities which differ primarily in species composition and flooding regime. Greatest leaf deposition occured in the more flooded communities, maple-gum (Acer-Nyssa) with 536 gm^-2 yr^-1 and cypress (Taxodium distichum (L.) Richard) with 528 gm^-2 yr^-1, followed by the cedar (Chamaecyparis thyoides (L.) BSP) and mixed hardwood (Quercus-Acer-Nyssa-Liquidambar) communities, with 506 gm^-2 yr^-1 and 455 gm^-2 yr^-1, respectively. Apparently periodic flooding promotes production. Peaks occurring in October and November corresponded to autumn leaf fall, while peaks in January and May were due to some leaf litter combined with a large amount of woody litter. Litter nutrient concentrations were higher, except for Ca, in the most abundant species (cypress and water gum) in the frequently flooded cypress community. Higher leaf fall rates and litter nutrient concentrations resulted in greater nutrient deposition in the cypress and maple-gum communities.     

广东森林群落排序分析

本文应用极点排序和位置向量排序的方法对广东13个森林群落进行排序分析,并分别用极点排序图和位置向量排序的二维图和三维图表示排序的结果。同时对排序图的生态学意义及排序方法的优缺点进行讨论。结果表明,三维位置向量排序图能较好地把性质相近的群落类型聚在一起,可作为植被分类的辅助方法;积点排序图从一定程度上反映了植被的连续变化;极点排序与位置向量排序虽然取得一定结果,但由于同属线性排序,损失的信息量较多,寻求非线性排序方法是研究的方向。     

广东森林群落的组成结构数量特征

本文探索森林群落组成结构水平的定量描述方法。通过用Shannon—Wiener多样性指数、Simpson生态优势度指标以及群落均匀度指标,测定广东范围内22个森林群落的物种多样性、生态优势度和群落均匀度。结果表明这三种指标值能有效地表征群落的组成结构特征;广东亚热带常绿阔叶林群落的物种多样性指数为4—5左右,群落均匀度为0.7—0.8左右,生态优势度为0.08—0.12左右。文章还对测定结果进行分析,进一步探讨了三种指标值的相互关系,三种指标值在群落学研究中的意义,以及在林业实践上的作用等。     

广东亚热带森林群落的生态优势度

本文应用simpson优势度指标,测定广东亚热带14个森林群落的生态优势度。对测定结果深入分析,说明了生态优势度指标在森林群落分析上有较大的意义,可以衡量不同的群落类型,作为群落分类的辅助指标;能反映群落生境变化对群落结构的影响,以及说明森林群落演替过程群落结构的变化;广东亚热带森林在自然状况下向气候顶极群落的演替过程中,生态优势度指标逐渐下降。 本文还进一步探讨生态优势度的生态学涵义。说明生态优势度指标的群落生态学意义,指出与物种多样性指数、群落均匀度在概念上的联系与差别,以及三者在应用上的异同。     

四川缙云山森林群落林窗边缘效应的研究

 本文运用Shannon—Wiener物种多样性指数、Simpson生态优势度指标以及边缘效应强度指数,对缙云山亚热带森林群落林窗的边缘效应现象进行了初步研究。29个林窗样地不同部位上述指标的测定表明用物种多样性指数拟合边缘效应测度通式,缙云山亚热带森林群落林窗的边缘效应强度值为1—3左右;而用生态优势度值拟合边缘效应强度测式,则上述边缘效应强度值为0.1一1.2左右。研究表明林窗边缘区由于边缘效应的作用有增大物种多样性的趋势。而林窗面积、所处坡向以及林窗所在的森林群落类型,都对处于不同发育阶段的林窗的边缘效应强度具有影响。在此基础上,本文对林窗边缘效应强度的变化规律、效应性质、测定意义以及对森林营造和优化管理上的作用进行了一定探讨。     

暖温带地区3种森林群落叶面积指数和林冠开阔度的季节动态

以辽东栎(Quercus liaotungensis)为主的落叶阔叶林、华北落叶松(Larix principis-rupprechtii)林和油松(Pinus tabulaeformis)林是暖温带林区具有代表性的森林群落类型。该研究应用国内外流行的半球图方法,通过对这3种森林群落叶面积指数和林冠开阔度的测定和综合比较,分析了叶面积指数和林冠开阔度的季节动态,揭示了暖温带地区不同类型森林群落叶面积指数和林冠开阔度的特征。研究结果表明,落叶阔叶林(优势种为辽东栎、棘皮桦(Betula dahurica)和五角枫(Acer mono))和华北落叶松林两种落叶森林群落的叶面积指数值均随生长季的到来而呈现增长的趋势,最大值出现在8月;林冠开阔度值随着生长季的到来而下降,最大值出现在11月。落叶阔叶林的叶面积指数和林冠开阔度的季节动态较之华北落叶松林明显。油松是常绿树种,其群落叶面积指数和林冠开阔度的变化程度均不明显,但林冠开阔度的变化趋势也是与叶面积指数的变化趋势相反。通过计算得出叶面积指数和林冠开阔度相关显著,并且呈现指数回归的关系。此研究结果为以遥感途径获取暖温带地区叶面积指数提供了地面校正依据,为研究该地区植被林冠的异质性及其造成的影响,以及进一步对该地区林分、景观和区域尺度上碳、水分和通量等方面的模拟提供了基础数据。     

大青沟森林植物群落主要木本植物种群分布格局及动态的研究

本文运用方差／均值比率法及聚集强度的某些指数研究了大青沟森林植物群落主要木本植物种群的分布格局及其动态。主要木本植物种群的分布格局大多为集群型,只有部分群落中大果榆、色木槭及家榆种群为随机分布。格局动态的分析表明,水曲柳、黄菠萝、春榆、大果榆种群幼苗—幼树—小树—中树—大树分布格局由集群分布逐渐变为随机分布,而蒙古栎由于较强的萌生性,大树阶段仍为集群分布。分析表明影响种群分布格局的因子大致可归纳为两类：一是物种本身的生物学特性,二是由环境条件引起的种内种间竞争;方差／均值比率法是一种较好的分析种群分布格局的方法。     

鼎湖山森林群落的光能利用效率

本文研究了鼎湖山自然保护区,亚热带季风常绿阔叶林和针叶阔叶混交林的光能利用效率。根据群落的垂直结构和成层现象,应用红外线CO_2气体分析法,分层测定了主要植物22种58株的光合速率.计算了群落的生产力;用量子传感器分层测定了两个群落的光合有效辐射,并计算其光能利用效率。结果表明:阔叶林总生产力的光能利用效率为14.28%,混交林为12.01%,说明了不同森林类型对光能资源的利用效率。     

GIS支持下陕西省植被生产有机物价值研究

 在地理信息系统的支持下,利用改进的周广胜NPP模型,根据陕西省植被图和陕西省相关的气候资料,充分考虑植被类型和覆盖度,以植被类型为单位估算了陕西省陆地生态系统NPP物质量进行了测定,结果为：陕西省陆地植被总产量为195.339 5 t·hm－2·a－1,单位面积平均产量为7.25 TDM·hm－2·a-1。得到陕西省植被NPP值列表。以第一性生产物质量为基础,采用能量比市场价格法测定了陕西省各种植被类型的生产力价值,结果是：陕西省的27个植被类型总净第一性生产力价值为358.50亿元。单位面积的生产力价值     

DETECTION OF ORGANIC MATTER IN INTERSTELLAR GRAINS

Star formation and the subsequent evolution of planetary systems occurs in dense molecular clouds, which are comprised, in part, of interstellar dust grains gathered from the diffuse interstellar medium (DISM). Radio observations of the interstellar medium reveal the presence of organic molecules in the gas phase and infrared observational studies provide details concerning the solid-state features in dust grains. In particular, a series of absorption bands have been observed near 3.4~2940 cm^–1) towards brightinfrared objects which are seen through large column densities of interstellar dust. Comparisons of organic residues, produced under a variety of laboratory conditions, to the diffuse interstellar medium observations have shown that aliphatic hydrocarbon grains are responsible for the spectral absorption features observed near 3.4 ~2940cm^–1). These hydrocarbons appear to carry the –CH₂– and –CH₃ functional groups in the abundance ratio CH₂/CH₃ ~ 2.5, and theamount of carbon tied up in this component is greater than 4% of the cosmic carbon available. On a galacticscale, the strength of the 3.4 band does notscale linearly with visual extinction, but instead increases more rapidly for objects near the Galactic Center. A similar trend is noted in the strength of the Si–O absorption band near 9.7. The similarbehavior of the C–H and Si–O stretching bands suggests that these two components may be coupled, perhaps in the form of grains with silicate cores and refractory organic mantles. The ubiquity of the hydrocarbon features seen in the near infrared near 3.4throughout our Galaxy and in other galaxies demonstrates the widespread availability of such material for incorporation into the many newly forming planetary systems. The similarity of the 3.4features in any organic material with aliphatic hydrocarbons underscores the need for complete astronomical observational coverage in the 2–30 region, oflines of sight which sample dust in both dense and diffuse interstellar clouds, in order to uniquely specify the composition of interstellar organics. This paper reviews the information available from ground-based observations, although currently the Infrared Satellite Observatory is adding to our body of knowledge on this subject by providing more extensive wavelength coverage. The Murchison carbonaceous meteorite has also been used as an analog to the interstellar observations and has revealed a striking similarity between the light hydrocarbons in the meteorite and the ISM; therefore this review includes comparisons with the meteoritic analog as well as with relevant laboratory residues. Fundamental to the evolution of the biogenic molecules, to the process of planetary system formation, and perhaps to the origin of life, is the connection between the organic material found in the interstellar medium and that incorporated in the most primitive solar system bodies.     

长白山次生林繁殖鸟的群落结构

研究了长白山次生林繁殖鸟的群落结构及其与森林植被的关系。在３块林龄相同而样地面积不等的次生林中,繁殖鸟种类有随样地面积增加的趋势,繁殖鸟数量随面积的增加而增加更为明显。相似性指数测定表明,３样地鸟类群落组成基本相似,多样性指数也无显著差异。鸟类物种多样性与植被剖面层次多样性相关。边缘种随林缘长度的增加,种－数系数不断增加。由林缘至林内５０ｍ宽的地带为鸟类高密度带。由边缘至林内３００ｍ后,鸟类密度有     

贵州部分森林群落物种多样性初步研究

 本文根据贵州省178个森林群落样地的数据研究了群落物种的多样性。测定的指标有群 落物种丰富度,群落Simpson多样性指数和群落均匀度。测定结果表明;不同垂直带生物气 候条件下的森林群落有不同的多样性。相同垂直带生物气候条件下,基质生境相同时,不同森林植被亚型的群落的多样性近似,基质生境不同时,群落多样性则不同;同一群落类型的各个样地的多样性也有变化,结构不同的群落个体,其多样性指数不同,演替趋势也不同。乔木第二亚层的多样性普遍地高于乔木第一亚层。同一演替系列中,越接近顶极阶段多样性越高。多样性指数与群落物种丰富度,均匀度呈紧密的正相关,与群落个体总数没有相关。认为多样性测定在比较、说明群落的结构、类型、组织特征、生境、演替等方面有一定意义。     

大熊猫栖息环境的森林凋落物动态研究

本文以王朗自然保护区冷杉、云杉暗针叶林为对象,在定位测定森林凋落量及其动态和枯枝落叶贮量的基础上,研究了凋落物分解速率及其主要营养元素含量的变化,结果表明：(1)地表枯枝落叶总贮量变化在30.0—91.8t／ha,其中未分解层4.9—17.8,半分解层11.5—19.7,腐殖质层13.6—57.3t／ha。(2)森林凋落的枯枝落叶量因林型不同而略有差异,平均为2.8 t／ha·yr,其凋落高峰期分别在生长季开始的5月和生长季末的10月。(3)每年以凋落物形式返回林地的养分,氮为35.5kg／ha、磷为5.7kg／ha、钾为7.0kg／ha、镁为6.8kg／ha、钙为62.9kg／ha。(4)森林各种凋落物的混合物年分解率为0.3041g／g。95%的凋落物被分解需时约10年,在分解一段时间后,凋落物中的氮、钙、镁含量略有上升,钾明显减少,而磷含量变化不大。(5)森林凋落物的混合物腐解过程中,养分释放速率大小的顺序为：K>P>Mg>Ca>N,大熊猫主食竹的凋落叶则为：K>N>Ca>Mg>P。     

广东亚热带部分森林群落排序分析

本文应用极点排序、主坐标分析和位置向量排序等3种排序技术,对广东亚热带11个森林群落进行排序。探索了这3种方法在广东亚热带植被分析上的应用效果;经过对排序结果的分析,说明了11个森林群落的相互关系,在一定程度上揭示了植被变化的生态学原因。