Reciprocal distribution of two congeneric trees, Betula platyphylla var. japonica and Betula maximowicziana, in a landscape dominated by anthropogenic disturbances in northeastern Japan

Aim Information has been compiled on disturbance regimes and the life‐history characteristics of Betula platyphylla var. japonica (Miq.) Hara and B. maximowicziana Regel to investigate the impact of humans on the present distribution patterns of these two congeneric tree species. Location The study area is in the central region of the northern Kitakami Mountain Range, located in the northeast of Honshu Island, Japan. Methods First, the present distributions of B. maximowicziana and B. platyphylla var. japonica were mapped at the landscape scale. To examine the factors affecting the distribution patterns, topographic features and past land use were taken into account. Second, life‐history traits of both species were clarified at various growth stages either by fieldwork or through a literature search. Previous studies have provided some information on seed production, seed dispersal, seedling dynamics, sprouting, and growth. In the present study, field observations and experiments were conducted regarding seed‐bank formation, size and age at reproduction, and the life span of canopy trees. Results Betula platyphylla var. japonica and B. maximowicziana were spatially segregated in the studied landscape (14,000 ha). The distribution of each species was correlated more strongly with land use at the beginning of the twentieth century than with site environmental factors such as altitude or slope angle. Betula platyphylla var. japonica was distributed more frequently on former grasslands, whereas B. maximowicziana was almost exclusively limited to past old‐growth forests. As typical pioneers, the two species showed similar life‐history traits but differed in several critical points. Betula platyphylla var. japonica has a vigorous sprouting ability, which might increase its resistance to burning and logging, whereas B. maximowicziana forms a persistent seed bank in the soil, indicating an advantage in regenerating in disturbances found in forest communities. Other critical differences were detected in age‐related characteristics such as minimum age of reproduction and life span. Main conclusions The earlier reproductive maturity and the shorter life span of B. platyphylla var. japonica indicate a shorter population cycle than that for B. maximowicziana. The latter would be excluded from grasslands that were burned frequently, as a result of the longer time span before initial reproduction and its poor sprouting ability. In contrast, B. platyphylla var. japonica would be excluded from old‐growth forests, where disturbance was infrequent, owing to its shorter life span and lack of a persistent seed bank.     

On threats analysis approach applied to a Mediterranean remnant wetland: Is the assessment of human-induced threats related to different level of expertise of respondents?

Naming, listing and measuring human-induced threats in protected areas are crucial in conservation. Here, we defined a check-list of direct threats in a Mediterranean remnant wetland (central Italy), managed as nature reserve, grouping them according to a taxonomically-oriented nomenclature. We assessed three regime parameters (scope, severity, and magnitude) applying an experience-based method, then comparing the assessments obtained from two different level of expertise: a panel of independent people, upper level “university students” in an applied ecology class; and a panel of “experts” as nature reserve biologists and managers. Despite observing a significant correlation among values assigned from students and experts for each regime parameter, students underestimated the scope of feral dogs, the severity of fires and the magnitude of feral dogs and water stress. Considering only the magnitude values (sum of scope and severity), students assigned the higher values to alien species, antropophilous species, aircraft, and pollution, while the experts assigned the higher values to antropophilous species, aircraft, alien species, and water stress. In an order of priority, there was an agreement between students and experts with a coincidence for three threats out of four. We suppose that a panel of students with a short academic training could be useful to a get a first order of priority in regard to a set of local selected threats, with much similarity to the assessment obtained from a panel of experts. When threat metrics are difficult to compare, experience-based approach obtained from technicians trained ad hoc (“students”) could be useful to define priorities for management strategies in nature reserves, but data obtained should be examined critically. Indeed, students may assign higher scores to regime parameters of threats more readily identified and perceivable, underestimating the threats with an inconstant regime, localized in time and space, mobile, or cryptic. If experience-based methods are used to define scale of priorities, these issues need to be considered.     

Disturbance of a Kenya Rift Valley stream by the daily activities of local people and their livestock

Human and domestic animal activities and visits to an impacted site in the Njoro River, Kenya, were recorded from 1994 to 1995. The activities of people in the humid and wet zones of the stream included linen washing, water abstraction, excretion, bathing and swimming. Human and animal visits and activities along the Njoro River were on a daily basis and were patterned according to the time of the day, weather and seasons. Women formed the first group to visit the stream at dawn, followed by men and lastly, children. The diurnal pattern of visits was bimodal, with major peaks between 0600 and 1100 h and from 1600 h until dusk. The intensity of all major activities peaked at around midday and donkeys and cattle formed the largest proportion of the domestic animals that visited the stream. Much of the small-scale water abstraction occurred between 0700 and 1100 h, coinciding with the time when most people visited the stream. Water abstraction was most intense during the dry season. A mean discharge of 1.7 litres per second was measured whilst 0.3 litre of water per second was abstracted at the impacted site, implying that about 20% of the flow volume of the Njoro River was abstracted at a single site in one day.The effects of the human and animal activities on the structure of macrozoobenthos in the wet zone of the Njoro River were studied on the impacted site in relation to an upstream reference site and a downstream reference site. Oligochaetes and chironomids dominated the fauna in all three sites. The impacted site had low patchiness and mean crowding, with the taxa distribution tending toward a randomly dispersed spatial pattern. The mean turnover (±SD) of the macroinvertebrates was 47±18, 48±26 and 36±22 in the impacted, downstream and upstream sites, respectively. The trampling of the streambed by humans and livestock could, therefore, alter the benthos structure through redistribution and reduction of faunal patchiness. The cumulative effect of small-scale, but widespread and frequent disturbances might have large impacts on whole river systems. This study demonstrated that, in the tropics, quantification of the daily activities of people and domestic animals is important for future management of the Njoro River and consequently, Lake Nakuru.     

Calcium phosphate transfection optimization for serum-free suspension culture

Aim of this study was to identify optimal conditions for suspension transfection in the absence of serum. Transfection parameters for suspension culture can be very different to ones in adherent cells. Most transfection protocols have been developed and optimizedfor adherent culture. Using green fluorescent protein (GFP) as reporter, FCS was eliminated from the transfection process by altering critical parameters and by substituting serum with albumin. Using standard phosphate and calcium concentrations for transfection in the absence of serum resulted in titers of only 1% of those observed in the presence of serum. A reduction of the calcium concentration from 250 mM to 100 mM, yielded a 25-fold increase in the expression of the recombinant protein compared to the serum-free standard conditions. Altering the phosphate concentration, 1.4 mM in the transfection buffer, did not improve the protein expression. Interestingly, reduction of DNA quantity by half to a concentration of 0.5 μg per milliliter of culture volume resulted in a two-fold increase of protein production. Addition of albumin to serum-free medium protected the cells against the toxicity of the calcium phosphate transfection particles (CaPi) yielding higher protein expression. All the experiments were executed in a shaken multi-well system, allowing high multiplicity parameter screening to speed up optimizations. The culture system is inexpensive, simple and efficient, minimizing costs for labor and consumables. This revised version was published online in July 2006 with corrections to the Cover Date.     

Neutral communities may lead to decreasing diversity-disturbance relationships: insights from a generic simulation model

Many attempts have been made to confirm or reject the unimodal relationship between disturbance and diversity stated by the intermediate disturbance hypothesis (IDH). However, the reasons why the predictions of the IDH apply or fail in particular systems are not always obvious. Here, we use a spatially explicit, individual-based community model that simulates species coexistence in a landscape subjected to disturbances to compare diversity-disturbance curves of communities with different coexistence mechanisms: neutrality, trade-off mechanism and intraspecific density dependence. We show that the shape of diversity-disturbance curves differs considerably depending on the type of coexistence mechanism assumed: (1) Neutral communities generally show decreasing diversity-disturbance curves with maximum diversity at zero disturbance rates contradicting the IDH, whereas trade-off communities generally show unimodal relationships confirming the IDH and (2) density-dependent mechanisms do increase the diversity of both neutral and trade-off communities. Finally, we discuss how these mechanisms determine diversity in disturbed landscapes.     

古田山不同干扰程度森林的群落恢复动态

森林采伐后次生林的恢复过程对于生物多样性的保护和生态系统功能的重建具有重要意义。作者以古田山不同干扰程度的12个1 ha 森林样地为研究对象, 运用群落多元统计方法, 探讨了自然恢复过程中森林群落组成及物种多样性的动态变化及趋势。结果表明: 不同恢复阶段森林样地的群落组成存在显著性差异, 而同一恢复阶段的样地具有高度的相似性。物种丰富度随恢复进程有增加的趋势, 但各阶段差异并不显著; 物种均匀度除人工林较低以外, 其他恢复阶段之间无显著性差异。不同恢复阶段研究样地的群落组成及物种多样性的差异主要存在于林冠层。灌木及更新层具有各自的指示种, 人工林的指示种为落叶灌木或阳性乔木, 幼龄次生林的指示种为常绿灌木或小乔木, 老次生林的指示种为亚乔木层常绿树种, 老龄林的指示种为林冠层树种。上述结果表明古田山不同人为干扰程度森林群落的物种多样性具有较强的自我恢复能力。尽管物种组成难以预测, 但处于同一恢复阶段的森林, 其幼树的生活型组成呈现出一致的变化趋势。     

Early life stress, MAOA, and gene-environment interactions predict behavioral disinhibition in children

Several, but not all, studies have shown that the monoamine oxidase A functional promoter polymorphism ( MAOA-LPR ) interacts with childhood adversity to predict adolescent and adult antisocial behavior. However, it is not known whether MAOA-LPR interacts with early life (pre-birth–3 years) stressors to influence behavior in prepubertal children.
The Avon Longitudinal Study of Parents and Children, UK, is a community-representative cohort study of children followed from pre-birth onwards. The impact of family adversity from pre-birth to age 3 years and stressful life events from 6 months to 7 years on behavioral disinhibition was determined in 7500 girls and boys. Behavioral disinhibition measures were: mother-reported hyperactivity and conduct disturbances (Strengths and Difficulties Questionnaire) at ages 4 and 7 years.
In both sexes, exposure to family adversity and stressful life events in the first 3 years of life predicted behavioral disinhibition at age 4, persisting until age 7. In girls, MAOA-LPR interacted with stressful life events experienced from 6 months to 3.5 years to influence hyperactivity at ages 4 and 7. In boys, the interaction of MAOA-LPR with stressful life events between 1.5 and 2.5 years predicted hyperactivity at age 7 years. The low activity MAOA-LPR variant was associated with increased hyperactivity in girls and boys exposed to high stress. In contrast, there was no MAOA-LPR interaction with family adversity.
In a general population sample of prepubertal children, exposure to common stressors from pre-birth to 3 years predicted behavioral disinhibition, and MAOA-LPR – stressful life event interactions specifically predicted hyperactivity.     

社群大小的年变化、气候和人类活动对神农架自然保护区川金丝猴日移动距离的影响

作者于2001年4月至2003年1月研究了社群大小的年变化、气候和人类活动对神农架自然保护区千家坪地区一群川金丝猴(Rhinopithecusroxellana)日移动距离的影响。对该群金丝猴进行了8个季节的跟踪研究,每季连续跟踪30d。用社群直线距离法确定猴群的日移动距离,同时调查社群大小,记录人为活动和气象因子。研究结果显示:(1)两年间猴群的个体数增加了14%,但其日移动距离没有明显变化,说明社群大小的年变化对日移动距离没有影响。(2)猴群在人为活动影响下的日移动距离比没有人为活动影响时长。(3)多变量回归分析显示,各个季节中,猴群的日移动距离与一天中晴和有云但无降水所占时间的比例没有相关性;与春季和冬季日降雨或雪所占时间的比例呈负相关,但与夏季和秋季的没有相关性,说明降水缩短了冬春季猴群的日移动距离,这可能与川金丝猴的繁殖有关。人为活动对猴群是不利的;冬春季的长时间降水可能是川金丝猴的灾害性天气。