Seasonal population dynamics of Eisenia fetida (Savigny, 1826) (Oligochaeta, Lumbricidae) in the field

In order to assess the response of epigeic earthworms to seasonal changes we monitored the population dynamics of Eisenia fetida (Oligochaeta, Lumbricidae) in a manure heap in the field during a year. Earthworms were hand-sorted from five 0.25 x 0.25 x 0.20 m blocks around the heap in November (autumn) 1999 and in January (winter), April (spring) and August (summer) 2000 to determine earthworm population dynamics. Earthworms of each block were classified into different age classes: mature, preclitellate, juvenile, hatchling and cocoon, and afterwards counted and weighed. Seasonality had a strong effect on the density, biomass and reproductive activity of the population. The population of E. fetida was characterized by a high density of individuals and the predominance of mature individuals throughout the year. Maximum density, mating activity and size of cocoons were achieved in spring, but there were not changes in the number of cocoons per mature earthworm throughout the year. Unexpectedly, the smallest cocoons were produced in winter by the largest individuals. These results suggest that E. fetida is able to allocate resources to growth and/or reproduction in response to environmental fluctuations.     

Population dynamic consequences of competition within and between age classes

We investigate the population dynamics of a semivoltine species whose juvenile development takes two years to complete, and is followed by a very short reproductive adult stage. Reproduction is synchronized so at any given time the juvenile population consists of two cohorts. Coexistence of the two cohorts requires that the strength of intea-cohort competition exceeds that of inter-cohort competition, an extension of the competitive exclusion principle. The population may exhibit population cycles with low integer period. We identify two mechanisms for two-year cycles, and note that four-year cycles are a natural consequence of overcompensation. Three year cycles can occur and we discuss the mechanisms involved.     

北京地区黑线仓鼠年龄鉴定及种群年龄组成的研究

鼠类种群年龄组成的研究是种群生态学的基础内容。种群年龄组成的变化,直接关系到鼠类数量的波动。黑线仓鼠(Cricetulus barabensis)是北京地区农田的主要害鼠之一,为探讨该鼠种在农田生态系统中的作用,并控制其危害,研究其种群年龄组成及变化是非常必要的。     

中华鲟年龄鉴别和繁殖群体结构的研究

本文研究中华鲟的年龄鉴别和葛洲坝枢纽工程大江截流后1981—1982年群集于坝下的宜昌至石首江段的中华鲟繁殖群体结构的特点。根据匙骨大小与中华鲟长度呈显著相关推算了中华鲟在海洋中的生长速度,计算了体长和体重的函数值及尾叉体长、体重和胸围的复相关。根据鳍条骨和匙骨年轮排列格局特点计算了中华鲟初次产卵和重复产卵的比例,同时,就宽区宽带轮和狭区狭带轮交替过程反映的生物学特征作了初步分析与探讨。     

不同放牧率对大针茅种群结构的影响

 采用连续放牧的方式研究了不同放牧率对大针茅(Stipa grandis)种群结构的影响。研究结果表明：在一定放牧率范围内,单丛分蘖密度随着放牧率的增加而增加,超过这个范围,单丛分蘖密度下降;单位面积生殖枝数、结实数和种子重随放牧率的增加而下降,种子千粒重在轻度和中度放牧率下最大;不同年龄株丛的分蘖密度存在很大差异,老龄株丛的分蘖密度最大,其次是成年株丛,幼龄株丛最小;轻度和中度放牧率能够刺激成年和老龄株丛分蘖,增加其单丛分蘖密度;老龄株丛在种群的有性生殖中占有重要地位,其生殖枝数目高于成年株丛。     

洞庭平原褐家鼠年龄分组及种群年龄动态分析

本文采用1986年10月—1989年12月在洞庭平原收集的褐家鼠(Rattus norvegicus)标本,以胴体重作指标,参考繁殖特征,将褐家鼠划分5个年龄组:Ⅰ.幼体组,雌鼠<60克,雄鼠<70克;Ⅱ.亚成体组,雌鼠60—99克,雄鼠70—119克;Ⅲ.成体Ⅰ组,雌鼠100—139克,雄鼠120—169克;Ⅳ.成体Ⅱ组,雌鼠140—189克,雄鼠170—219克;Ⅴ.老体组,雌鼠>190克,雄鼠>220克。种群年龄结构的季节动态特征是:开春时以Ⅲ、Ⅳ组占优势,初夏时Ⅰ、Ⅱ组明显增加,7、8、9月各年龄组比例较均匀,冬季以Ⅱ、Ⅲ组为主。还探讨了年龄与体重、体长、尾长及繁殖率的相互关系。     

The significance of life history strategies in the developmental history of mixed beech (Nothofagus) forests,New Zealand

Size and age structure analysis, dated past disturbances, treefall replacement patterns, and spatial pattern analysis were used to reconstruct the developmental history of two old-growth Nothofagus fusca/N. menziesii stands, South Island, New Zealand. Diameter and height class distributions suggested that N. menziesii was replacing N. fusca, however, stand history reconstruction analysis showed that both species had regenerated intermittently after small-scale disturbances. Although large-scale disturbances such as blowdowns may occasionally generate even-aged stands, gap-phase regeneration maintains the forests in compositional equilibrium. In the absence of other competing tree species and understorey plants the two species appear to coexist by way of different life history strategies, where one species (N. menziesii) has low juvenile mortality and the other (N. fusca) has faster height growth rates and greater longevity and adult survivorship.     

大沙鼠的年龄鉴定与种群年龄组成

在鼠类生态学的研究中 ,对鼠类年龄的鉴定是一项重要的工作。年龄组成是种群的重要特征之一 ,它有助于了解种群的年龄结构以及种群数量变动的规律。大沙鼠 (Ｒｈｏｍｂｏｍｙｓｏｐｉｍｕｓ)是中亚地区荒漠及半荒漠草原的重要害鼠之一 ,在内蒙古西部的梭梭 (Ｈａｌｏｘｙｌｏｎａｍｍｏｄｅｎｄｒｏｎ)林区 ,由于大沙鼠的啃咬 ,影响了该地区梭梭林的正常结实 ,从而降低了结实量[1 ] 。同时 ,大沙鼠又是鼠疫和皮肤利什曼病的重要宿主。对大沙鼠的年龄鉴定与种群年龄组成进行研究 ,将有助于了解其种群数量变动的规律 ,从而为有效防治大沙鼠鼠…     

水毛茛种群生态学研究

本文根据6年定位研究结果,讨论了东北山溪激流中整株越冬的草本植物─-水毛茛的有关种群生态方面的问题;诸如水毛茛种群的空间分布格局、种群年龄区段结构和种群数量的周期性变动等;并利用观测数据编制了水毛茛种群的静态生命表,绘制了种群的存活曲线和死亡动态曲线,根据种群生殖力表计算了种群的内禀增长能力.利用逻辑斯蒂标准曲线对植物种群数量增长曲线进行拟合.最后对年龄区段的划分及其在生命表中的作用、种群数量变动及其影响因素、迁入与迁出对水毛茛种群大小的影响等进行了探讨.     

东灵山两个落叶阔叶林中辽东栎种群结构和动态

对北京东灵山地区的两个辽东栎种群的结构和数量动态进行了研究。在研究种群的空间分别格局时,分别将两个种群中的每个辽东栎个体在样地中进行定位。将辽东栎个体按不同尺度大小分为４类,在每一尺度中,按不同格子尺度进行机取样,分别计算Ｍｏｒｉｓｔａ的分布指数,聚块性指数,方差／均值比。用这些指数判断辽东栎不同大小级别以及不同取样尺度上的格局强度。结果表明,两个种群的格局强度都随尺度的不同而变化。５０龄辽东栎林     

沙地云杉种群结构与动态的研究

本文用种群大小结构代替年龄结构研究了沙地云杉种群的大小结构、分布格局和动态规律。结果表明,样地1、2、3、5的沙地云杉种群属于增长型,样地4的沙地云杉种群为稳定型,将样地1、2、3作为一块样地,其分布格局为集群型,但从幼树到大树,则由集群分布变为随机分布。     

Population ecology of an afro-tropical savanna herb,Lapeirousia rivularis,in Zambia

Detailed demographic studies of herbaceuos plants in afro-tropicalsavannas are extremely rare in published literature. I studied phenology andpopulation dynamics of a perennial herb, Lapeirousiarivularis Wanntorp, at a savanna site in Zambia over a 4-yearperiod, from 1997 to 2001, using enumeration techniques in permanent andtemporary quadrants. The age of the plants was accurately determined frompersistent annual sheaths that accumulate around the corm throughout the lifeofthe plant while the estimated survivorship of the 1998 cohort was developedfroma mathematical model based on the observed mortality of the cohort over a3-yearperiod.L. rivularis completed its annual phenological cycle in asingle rainy season. Plants sprouted from perennating corms in early December,flowered, fruited and dispersed seeds by end of January. Seeds germinatedimmediately after dispersal and seedlings produced small corms before aerialparts died early in the dry season. L. rivularis has twomorphs: a vegetative morph and a reproductive morph; the latter bears severalleaves and flower stalks. In the vegetative morph, the corm is renewed annuallywhile the corms of the reproductive morph did not appear to be renewed. Insteadcorms grew larger and produced lateral daughter corms that became independentramets the following rainy season.Most L. rivularis plants reached reproductive maturitywhen they were 6–10 years old. Reproductive success, seedlingestablishment and recruitment varied from year to year in the grassland plotperhaps because of fluctuations in weather conditions and heavy episodic insectherbivory. The survivorship curve of L. rivularis wascharacteristically concave due to high juvenile mortality (0.2–0.5) andvery low adult mortality (0.03). Although about 3% of the plants live to be upto 30–35 years, the mean age of the population in 2001 was 6.4 yearsbecause of the predominance of juvenile plants. The production of a protectivesheath at the end of the rainy season and the accumulation of old sheathsaroundthe fleshy corm are apparent adaptations against desiccation during the longdryseason drought when the topsoil remains below wilting point. The high juvenilemortality during the dry season is probably caused by inadequate protection bythe few sheaths around the corm against desiccation.Population dynamics in L. rivularis were caused byvariable annual recruitment and high juvenile mortality. Population densitydoubled in 1999 due to good fruiting success in the previous season that wasassociated with good weather conditions and negligible herbivory. Althoughcultivation had a significant negative effect on the population of L.rivularis, it increased consistency in fruiting success andproduction of fruits per plant, presumably because of improvement insoil-moisture status, reduction in plant competition and by providing temporalescape from insect herbivory through delayed flowering. The phenology and lifehistory of L. rivularis exhibit adaptations to a savannaenvironment that is characterized by disturbance and stress caused by seasonaldrought, fire, episodic herbivory and cultivation.     

臭鼠的种群年龄结构研究

１９８６年１月至１９９３年１２月,作者在浙江萧山围垦农区采用体重法将臭　种群分为５个年龄组。雄体：Ⅰ．幼年组（体重≤３０８）、Ⅱ．亚成年组（体重＞３０９,≤４０ｇ）、Ⅲ．成年１组（体重＞４０ｇ,≤５２ｇ）、Ⅳ．成年ＩＩ组（体重＞５２８,≤６４８）、Ⅴ．老年组（体重＞６４ｇ）;雌体：幼年组（体重≤２４ｇ）,Ⅱ．亚成年组（体重＞２４ｇ;≤３６ｇ）．Ⅲ．成年Ⅰ组（体重＞３６９,≤４６ｇ）,Ⅳ．成年Ⅱ组（体重＞４６８,≤５４ｇ）,Ⅴ．老年组（体重＞５４ｇ）。各年龄组的繁殖特性存在差异。种群以成年Ⅰ组为主,但其种群的年龄结构存在有性别差异,雄性种群以成年Ⅰ组、成年Ⅱ组和老年组为主,雌性种群以亚成年组和成年Ⅰ组为主。种群的年龄结构存在季节性变化。在室内,雄性在春季和冬季以成年Ⅱ组为主,夏季和秋季以老年组为主;在室外春季、秋季和冬季均以成年Ⅰ组为主,夏季则以成年Ⅱ组为主。室内雌性在各季节均以成年Ⅰ组为主,而在室外春季和冬季以亚成年组为主,夏季和秋季以成年Ⅰ组为主。其种群年龄结构存在有年变化。     

黄龙大熊猫种群数量及年龄结构调查

１９９６年６￣１０月,在野外采用路线－聚类法对黄龙寺自然保护区内大熊猫种群数量进行了调查。结果表明：保护区内现有大熊猫２３只,竹林内生态密度为０．４３９只／ｋｍ＾２。此外,首次采用了离差平方和聚类的方法,将该种群划分为４个年龄组。其中幼年组个体上占１３．３３％,青年组个体占６．６７％,成年组个体占６０％,老年组个体占２０％。最后还对结果进行了讨论。并提出了保护措施。     

大仓鼠种群年龄组存活率的估算

本文根据体重年龄组成数据和体重生长标准曲线,提出了一种估算鼠类各年龄组存活率的方法,其原理如下:设N_(i,k)为第k次取样时年龄组i的数量,DT_k为第k至k+1次间取样间隔,m为总取样次数,N_i和N_i分别为取样期年龄组i和j的总数量,T_i和T_j分别为年龄组i和j的发育历期,T_(i,j)为年龄组i到年龄组j的发育历期,φ_(i,j)为年龄组i到年龄组j的存活率,s_(i,j)为年龄组i到年龄组j的月均存活率,若DT_k相对的小,则有如下关系式:若DT_k恒定,即取样间隔一定,那么, φ_(i,j)=N_i/T_j/N_i/T_j s_(i,j)=e~[(30.Inφ_(i,j))/T_(i,j)] 根据夹捕和标志重捕资料,分别估算了1986和1988年河北省饶阳县大仓鼠(Cricetulustriton)种群各年龄组间月均存活率。在1986年,胎—Ⅱ,Ⅱ—Ⅲ,Ⅲ—Ⅳ和Ⅳ—Ⅴ月均存活率分别为0.6031,0.5874,0.7423和0.7426,平均为0.6689±0.0852;在1988年分别为0.5716,0.6417,0.5658和0.7437,平均为0.6307±0.0829。此外,还分别估算了大仓鼠雌、雄种群的月均存活率。     

黑线仓鼠种群年龄组成及其数量季节消长的研究

本文对黑线仓鼠的上臼齿磨损程度进行了系统观察,共采标本553只,结合生殖系统的解剖记录,确定以右侧上臼齿的磨损程度将黑线仓鼠划分为5个年龄组。探讨了年龄与体长、体重及繁殖力的相互关系,以及种群数量季节消长与气候条件及种群结构的关系。结果表明,黑线仓鼠年龄越大,雌鼠的繁殖力越高,但平均怀仔量并不随年龄增大而增加。体重、体长不易作为划分黑线仓鼠年龄组的指标。种群数量与大降雨量呈明显的负相关,但种群的年龄结构对数量消长起着主要作用。     

海北高寒草甸金露梅灌丛根田鼠种群生产力的研究Ⅰ.种群动态

1980—1982年在青海省海北高寒金露梅(Potentilla fruticosa)灌丛地区,用标志重捕法(CMR)对自然栖息地中的根田鼠(Microtus oeconomus)进行了野外调查。本文主要分析了根田鼠种群数量变动特点和繁殖、存活及年龄结构与种群动态的关系,并试图探讨根田鼠种群的稳定机制。     

安徽两种蜜蜂种群的春季繁殖及数量动态特征

1997～ 1999年在皖中和皖西、皖南山区对意大利蜜蜂 (ApismelliferaLigusticaSpi.)和中华蜜蜂(ApisceranaceranaFeb .)种群数量动态进行系统观察研究 .结果表明 ,蜜蜂种群数量明显受气候和蜜粉源植物的影响 ,周年呈现“两高”(春、秋 )和两低 (夏、冬 )的变化模式曲线 ;意大利蜜蜂春繁及秋季更新速度明显快于中华蜜蜂 ,但越夏效果不及中华蜜蜂 .意大利蜜蜂的性比值为 (314.4± 2 89.9)∶1～ (32 9.4± 30 5 .8)∶1,中华蜜蜂为 (334.2± 2 35 .5 )∶1～ (413 .1± 377.2 )∶1,雄蜂呈季节性出现 .蜜蜂种群内年龄组配在不断变化 .