Redundancy and niche differentiation among the European invasive <Emphasis Type="Italic">Elodea</Emphasis> species

Community ecologists implicitly assume redundancy when they aggregate species into functional groups. But there have been remarkably few empirical efforts to investigate the accuracy of this concept in situ. The concept of redundancy could be roughly split into two components: the ecological redundancy (similar response to environmental variations involving similar ecological processes) and the functional redundancy (similar biological trait combinations shaping similar functional processes). Both types of redundancy are tested among the 3 invasive European Elodeas. In 11 sites and during two successive years 2004–2005, the cover growth rate of each Elodea species was monthly recorded. To test ecological redundancy, cover growth rates were related to a large suite of environmental variables. To test functional redundancy, 13 biological traits involved in competitive relationships were measured each month. Firstly, the redundancy hypothesis looks problematic for Elodea ernstiae. Indeed, the later possess numerous biological traits involved in light competition and niche overlap with the other Elodeas is very low. Secondly, ecological and functional redundancy can be successfully applied to Elodea canadensis and Elodea nuttallii. They share a large suite of biological traits leading to wide niche overlaps through the growing season. And the measured environmental variables do not differentially influence their growth rates, which are, in turn, controlled by a similar group of biological traits. In this way, the different invasiveness patterns of E. canadensis and E. nuttallii could be solely due to the ecological drift and their ecological dynamic could follow neutral rules.     

川西米亚罗林区主要树木生长对气候响应的差异

为分析青藏高原东缘半湿润区不同树种树木生长对气候变化的响应规律,于川西米亚罗林区海拔3000 m左右(低海拔)采集铁杉、岷江冷杉、紫果云杉,海拔4000 m左右林线位置(高海拔)采集岷江冷杉、四川红杉,共计182棵树木年轮样芯,建立了不同树种的树轮宽度年表,对不同树种的年轮指数与各月气候因子进行相关分析.结果表明： 在低海拔处,树木生长与4、5月气温呈负相关,与4、5月降雨呈正相关,受到春季干旱胁迫的影响;但树种之间存在显著差异： 铁杉的生长受春季干旱胁迫影响最严重,岷江冷杉次之,紫果云杉所受影响很小.在高海拔处,树木生长主要受生长季温度的影响,岷江冷杉年轮指数与当年2、7月最低气温呈显著正相关,与上一年10月最高气温亦呈正相关;四川红杉年轮指数与5月最高气温呈显著正相关,但与2月均温、3月最低气温呈显著负相关.近几十年青藏高原东北缘气候有干暖化趋势,如果这种趋势持续发生,低海拔紫果云杉长势将超过铁杉和岷江冷杉;高海拔处的升温更有利于岷江冷杉的生长.     

Income, birth order, siblings, and anthropometry

The purpose of the present cross-sectional study was to examine the relationship and effect of monthly household income, birth order, and number of siblings on adult body dimensions, adiposity index, and body composition among adult Bengali females. One hundred seventy-one adult Bengali females, age 20.35 +/- 1.51 years (mean +/- SD; range: 18-21 years) from Kolkata (formerly Calcutta) were studied. Anthropometric measures (weight, height, waist circumference, hip circumference, and triceps, biceps, subscapular, suprailiac, and medial calf skinfold thicknesses) were taken from all participants using standard protocols. BMI and log10 of the sum of the five skinfold thicknesses were computed subsequently. Percentage of body fat was estimated from the triceps skinfold thickness following the equation of Durnin and Womersley (1974), and fat mass was then calculated. Results of the correlation analysis revealed that monthly household income had significant (p < 0.05) positive association with all anthropometric variables. Birth order and number of siblings showed significant (p < 0.05) inverse association. The correlation of monthly household income with anthropometric variables was much stronger for number of siblings and birth order. The results of the analysis of variance showed that monthly household income, birth order, and number of siblings (tertiles used to categorize all variables) had significant effects (p < 0.05) on anthropometric variables, indicating differences in adult body dimensions, the adiposity index, and body composition in relation to income, birth order, and number of siblings.     

树木年轮揭示的东灵山主要树种间干旱耐受性差异

近年来北京地区的森林随极端干旱加剧表现出脆弱性特征,为了解气候变化下不同树种的干旱耐受性,选择北京东灵山森林内3个乔木树种(华北落叶松、油松和辽东栎),利用树木年轮生态学方法分析了径向生长与气候的关系,以及对极端干旱事件的抵抗力和弹性。结果表明: 华北落叶松和油松与5—6月气温呈显著负相关,辽东栎与5月气温呈显著负相关;华北落叶松与6月降水量、5—6月和8—9月相对湿度呈显著正相关,油松与6—8月降水量和相对湿度呈显著正相关,辽东栎与2月和5月降水量、5月相对湿度呈显著正相关;所有树种均与当年5—7月标准化降水蒸散指数(SPEI)呈显著正相关。华北落叶松是干旱耐受性最弱的树种,径向生长在所选极端干旱事件中(1994年、2001—2002年和2007年)下降幅度最大(46.6%～69.6%),抵抗力(0.534、0.304、0.530)和弹性(0.686、0.570、0.753)显著低于辽东栎和油松,辽东栎在2007年抵抗力显著高于油松,弹性无显著差异。生长季持续的高温或降水减少引起的极端干旱是树木径向生长下降的主要原因,树种间各异的生理生态策略是干旱耐受性差异的可能原因。研究结果可为未来造林树种选择和森林管护措施制定提供新依据,以在气候压力持续增加背景下维持森林生态系统功能和服务。     

Age and growth of the sand shark, Rhinobatos annulatus, in Algoa Bay, South Africa

Annual rings on the vertebral centra were used to determine age in the sand shark, Rhinobatos annulatus . A 6% silver nitrate solution was applied to the concave surfaces of the vertebrae to clarify the rings. The monthly percentage frequency of opaque and hyaline peripheral rings were used to determine the annual nature of the rings. Both sexes can reach a maximum age of 7 years. Conventional growth curves could not be fitted and empirical curves were used to illustrate growth. Total body length at age was calculated from these curves and compared with observed data.     

Some aspects of hepatic function in feral brown trout, Salmo trutta, living in metal contaminated water

Brown trout, Salmo trutta, exposed to heavy metals (mainly Cd and Zn) for at least 2 years in the Eagle River, Colorado, were examined for liver size and activity of the growth-promoting enzyme, ornithine decarboxylase (ODC) and compared to trout living in an uncontaminated site. Liver-somatic index (LSI) was greater for trout living in the uncontaminated site with the LSI of females being significantly greater than that of males. The LSI for females at the uncontaminated site was greater than that of females at the contaminated site, but males were not different statistically. ODC activity in the livers of both males and females was lower at the contaminated site. However, males and females did not differ with respect to ODC activity. These data suggest that chronic exposure to heavy metals may have important implications for growth and reproduction and possibly survival. The activity of ODC in liver might serve as a useful biomarker when assessing chronic toxicity of metals to naturally reproducing fish populations.     

穆棱东北红豆杉年轮-气候关系及其濒危机制

东北红豆杉是国家I级重点保护野生濒危植物,其径向生长与气候的关系对于探讨其种群濒危机制具有极其重要的意义。利用穆棱自然保护区内天然东北红豆杉树木年轮样本,建立了长300多年的树轮年表(1700—2005年)。分析径向生长特征发现东北红豆杉总体上呈波动式下降的生长方式,在1770年和1930年左右存在两个生长释放区,该地区调查的样本最大年龄达到370a左右。年表与气候变量之间相关分析表明,冬春季节最低气温、平均气温是树木生长的主要限制因子,其他气候因子也有一定的影响,但不起主要作用。1942年以后东北红豆杉年轮指数与Wilson重建的北半球气温变化吻合度降低,温度对东北红豆杉的径向生长限制性降低,这表明气候变暖可能有利于东北红豆杉的径向生长,但不足以说明气候变暖与东北红豆杉衰退的关系,其他气候因子的年轮气候响应分析也不能确定气候变化在东北红豆杉衰退中的主导作用。人为破坏可能是东北红豆杉衰退的主要因素,但气候变化在其中起到多大的贡献还有待深入研究。     

基于Sentinel-1和Sentinel-2A的西小山林场平均树高估测

森林资源调查对于我国森林生态系统可持续发展具有重要意义,森林平均高度是森林资源调查的主要结构参数,也是获取难度最大的关键参数之一。为探究联合主被动遥感技术在估测森林平均高度方面的潜力,本研究以吉林省临江市西小山林场为研究区,利用Sentinel-1 SAR和Sentinel-2A数据,通过提取Sentinel-1的2个后向散射系数、8个纹理信息,以及Sentinel-2A的10个光谱波段及其纹理信息和11个植被指数,采用多元线性回归方法分别建立基于上述变量以及融合4类变量的5组平均树高估算模型,并评估各变量对反演精度的影响。结果表明: 单一数据源变量中,基于Sentinel-2A光谱波段提取的纹理信息建模效果较好,能够作为估算森林平均高度的有效数据;融合4类变量的森林平均高度估算模型最优,R²达0.56、留一交叉验证均方根误差为2.92 m、相对留一交叉验证均方根误差为21.5%。基于Sentinel-1与Sentinel-2A特征变量的平均树高模型能够提高森林高度的估算精度,可用于区域森林平均高度估测和制图。     

Genetic diversity and connectivity remain high in <Emphasis Type="Italic">Holothuria polii</Emphasis> (Delle Chiaje 1823) across a coastal lagoon-open sea environmental gradient

Coastal lagoons represent habitats with widely heterogeneous environmental conditions, particularly as regards salinity and temperature, which fluctuate in both space and time. These characteristics suggest that physical and ecological factors could contribute to the genetic divergence among populations occurring in coastal lagoon and open-coast environments. This study investigates the genetic structure of Holothuria polii at a micro-geographic scale across the Mar Menor coastal lagoon and nearby marine areas, estimating the mitochondrial DNA variation in two gene fragments, cytochrome oxidase I (COI) and 16S rRNA (16S). Dataset of mitochondrial sequences was also used to test the influence of environmental differences between coastal lagoon and marine waters on population genetic structure. All sampled locations exhibited high levels of haplotype diversity and low values of nucleotide diversity. Both genes showed contrasting signals of genetic differentiation (non-significant differences using COI and slight differences using 16S, which could due to different mutation rates or to differential number of exclusive haplotypes. We detected an excess of recent mutations and exclusive haplotypes, which can be generated as a result of population growth. However, selective processes can be also acting on the gene markers used; highly significant generalized additive models have been obtained considering genetic data from 16S gene and independent variables such as temperature and salinity.     

Climate–tree growth relationships of longleaf pine (Pinus palustris Mill.) in the Southeastern Coastal Plain, USA

Knowledge of tree growth/climate response relationships is important to dendroecological studies and dendroclimatic reconstructions, particularly in the Southeastern Coastal Plain where few such studies have been attempted. To this end, we developed tree-ring chronologies of total ring width, earlywood width, and latewood width from longleaf pine (Pinus palustris Mill.) at three sites in the Southeastern Coastal Plain to examine the climate–growth relationships for this tree species. The length of these chronologies is unprecedented for southern pine chronologies in the Southeast. We compared the tree-ring chronologies to monthly temperature, precipitation, Palmer drought severity index (PDSI), and Palmer hydrological drought index (PHDI) data from the pertinent climate divisions. We found that PDSI and PHDI have the highest correlation with longleaf pine growth, and the strongest relationships between longleaf pine growth and these variables occur between July and November. Precipitation in the spring and summer was also positively related to growth at all sites. The relationship between temperature and growth was the weakest among all climate variables, but warm summer temperatures had a consistent, negative relationship with longleaf pine growth. The climate signal in the latewood was generally more robust than for total ring width and earlywood width.     

Climate variables and spawning migrations of the striped mullet and white mullet in the north‐western area of the Gulf of Mexico

The 'smoothed'(4253e HT smoother) 6 year time series with a monthly periodicity of catches (where the increases of the catches reflect the spawning migration) of Mugil cephalus and Mugil curema , were correlated (Pearson correlation index) against the 'smoothed' data on rainfall, water temperature, daylight and tide monthly averages. Water temperature and M. curema spawning migrations had a negative correlation ( r  = −0·77), while tide monthly averages and M. cephalus spawning migrations were positively correlated ( r  = 0·84). The two environmental variables that showed highly significant correlations were water temperature and daylight ( r  = 0·85, P  < 0·05). Meteorological tides were used as a reflection of the effect of the north winds from the Gulf of Mexico which produce an average tide rise from September to November. The relationship of these variables with spawning migrations is discussed, and it is suggested, in particular, that meteorological tides, as a reflection of the north winds, are the trigger (zeitgebers) for M. cephalus spawning in the ocean.     

Performance, reliability, and performability of a hybrid RAID array and a comparison with traditional RAID1 arrays

We describe a hybrid mirrored disk organization patented by LSI Logic Corp. and compare its performance, reliability, and performability with traditional mirrored RAID1 disk organizations and RAID(4+?), ?≥1. LSI RAID has the same level of redundancy as mirrored disks, but also utilizes parity coding. Unlike RAID1, which cannot tolerate all two disk failures, LSI RAID similarly to RAID6 is 2?Disk Failure Tolerant (2DFT), but in addition it can tolerate almost all three disk failures, while RAID1 organizations are generally 1DFT. We list analytic expressions for the reliability of various RAID1 organizations and use enumeration when the reliability expression cannot be obtained analytically. An asymptotic expansion method based on disk unreliabilities is used for an easy comparison of RAID reliabilities. LSI RAID performance is evaluated with the Read-Modify-Write (RMW) and ReConstruct Write (RCW) methods to update parities. The combination of the two methods is used to balance data and parity disk loads, which results in maximizing the I/O throughput. The analysis shows that LSI RAID has an inferior performance with respect to basic mirroring in processing an OLTP workload, but it outperforms RAID6. LSI RAID in spite of its higher Mean Time to Data Loss (MTTDL) is outperformed by other RAID1 organizations as far as its performability is concerned, i.e., the number of I/Os carried out by the disk array operating at maximum I/Os Per Second (IOPS) until data loss occurs. A survey of RAID1 organizations and distributed replicated systems is also included.     

The Role of Late-Acting Self-Incompatibility and Early-Acting Inbreeding Depression in Governing Female Fertility in Monkshood,Aconitum kusnezoffii

Reduced seed yields following self-pollination have repeatedly been observed, but the underlying mechanisms remain elusive when self-pollen tubes can readily grow into ovaries, because pre-, post-zygotic late-acting self-incompatibility (LSI), or early-acting inbreeding depression (ID) can induce self-sterility. The main objective of this study was to differentiate these processes in Aconitum kusnezoffii, a plant lacking stigmatic or stylar inhibition of self-pollination. We performed a hand-pollination experiment in a natural population of A. kusnezoffii, compared seed set among five pollination treatments, and evaluated the distribution of seed size and seed set. Embryonic development suggested fertilization following self-pollination. A partial pre-zygotic LSI was suggested to account for the reduced seed set by two lines of evidence. The seed set of chase-pollination treatment significantly exceeded that of self-pollination treatment, and the proportion of unfertilized ovules was the highest following self-pollination. Meanwhile, early-acting ID, rather than post-zygotic LSI, was suggested by the findings that the size of aborted selfed seeds varied continuously and widely; and the selfed seed set both exhibited a continuous distribution and positively correlated with the crossed seed set. These results indicated that the embryos were aborted at different stages due to the expression of many deleterious alleles throughout the genome during seed maturation. No signature of post-zygotic LSI was found. Both partial pre-zygotic LSI and early-acting ID contribute to the reduction in selfed seed set in A. kusnezoffii, with pre-zygotic LSI rejecting part of the self-pollen and early-acting ID aborting part of the self-fertilized seeds.     

Growth behaviour of the invasive species <Emphasis Type="Italic">Ipomoea carnea</Emphasis> in the Nile Delta,Egypt

Ipomoea carnea Jacq., a native shrub of South America, grows in dense populations along river beds, river banks, canals and other waterlogged (wetland) areas. It has become naturalised along canals, drains, road sides and field edges in the Nile Delta, Egypt. The rapid growth rate, spread and adaptability from xeric to aquatic habitats indicates that this plant may potentially become a disastrous invasive species in Egyptian water bodies. Fifty established stands covering seven habitats (railway sides, waste lands, road sides, drain and canal banks, road dividers and field edges) in the Nile Delta were used in this experiment. In each stand, 20 ramets were permanently marked to estimate the monthly variations in such growth variables as phenology, height and diameter of the ramet canopy, number of flowers, leaves and fruits. The results showed a significant variation in growth variables relative to habitat types. Generally, I. carnea populations along the railway sides and field edges had the lowest values for most variables; while those of the road dividers, road sides and canal banks produced the highest values. The growth of I. carnea follows a seasonal pattern where the highest values for most growth variables were obtained during September and October and the lowest were recorded during June and July. The greatest flower and fruit production was observed between September and December. Similarly, it was shown that the flowering time varied in relation to habitat types; it began earlier on road sides and canal banks, but later on railway sides, road dividers and waste lands. Leaf areas of I. carnea populations in the wet habitats (e.g. drain and canal banks) were higher than those in other habitats. These results are discussed in relation to other related studies.     

Estimating equations for parameters in stochastic growth models from tag-recapture data

James (1991, Biometrics 47, 1519-1530) constructed unbiased estimating functions for estimating the two parameters in the von Bertalanffy growth curve from tag-recapture data. This paper provides unbiased estimating functions for a class of growth models that incorporate stochastic components and explanatory variables. A simulation study using seasonal growth models indicates that the proposed method works well while the least-squares methods that are commonly used in the literature may produce substantially biased estimates. The proposed model and method are also applied to real data from tagged rock lobsters to assess the possible seasonal effect on growth.     

Mountain pine beetle selectivity in old‐growth ponderosa pine forests,Montana, USA

A historically unprecedented mountain pine beetle (MPB) outbreak affected western Montana during the past decade. We examined radial growth rates (AD 1860–2007/8) of co‐occurring mature healthy and MPB‐infected ponderosa pine trees collected at two sites (Cabin Gulch and Kitchen Gulch) in western Montana and: (1) compared basal area increment (BAI) values within populations and between sites; (2) used carbon isotope analysis to calculate intrinsic water‐use efficiency (iWUE) at Cabin Gulch; and (3) compared climate‐growth responses using a suite of monthly climatic variables. BAI values within populations and between sites were similar until the last 20–30 years, at which point the visually healthy populations had consistently higher BAI values (22–34%) than the MPB‐infected trees. These results suggest that growth rates two–three decades prior to the current outbreak diverged between our selected populations, with the slower‐growing trees being more vulnerable to beetle infestation. Both samples from Cabin Gulch experienced upward trends in iWUE, with significant regime shifts toward higher iWUE beginning in 1955–59 for the visually healthy trees and 1960–64 for the MPB‐infected trees. Drought tolerance also varied between the two populations with the visually healthy trees having higher growth rates than MPB‐infected trees prior to infection during a multi‐decadal period of drying summertime conditions. Intrinsic water‐use efficiency significantly increased for both populations during the past 150 years, but there were no significant differences between the visually healthy and MPB‐infected chronologies.     

基于清查数据的福建省马尾松生物量转换和扩展因子估算差异解析——3种集成学习决策树模型的比较

生物量转换和扩展因子(BCEFs)是估算森林生物量碳储量普遍使用的重要参数.厘清BCEFs估算差异的来源,可降低森林生物量碳储量评估的不确定性.利用基于集成学习的决策树模型能够很好地解决BCEFs估算差异来源问题.然而,不同此类模型的对比研究目前尚未见报道.本研究以第8次国家森林资源清查福建省331块马尾松的固定样地数据作为材料,分别利用增强回归树(BRT)、随机森林(RF)和立体派(Cubist)模型分析BCEFs(包括地上和地下部分)估算差异的来源.结果表明: 研究区马尾松BCEFs呈右偏分布,平均值为0.69 t·m^-3,最小值为0.67 t·m^-3,最大值为0.71 t·m^-3.BRT、RF和Cubist模型对BCEFs的拟合和预测能力均很好,均能够解释92.8%以上的BCEFs变异.3种模型均给出了相同的前2个相对贡献率最大的自变量,为平均胸径和蓄积量.BCEFs随着平均胸径、蓄积量的增加呈逐渐减小的趋势.平均胸径、蓄积量、平均年龄和平均树高等林分特征因子对BCEFs的影响极大,而土壤因子和地形因子对BCEFs的影响均很小.在建立BCEFs模型时,利用平均胸径、蓄积量、平均年龄和平均树高等少量包含较多BCEFs预测信息的变量便能获取很好的预估精度.当应用固定BCEFs时,应选择在平均年龄、平均胸径以及蓄积等方面具有广泛代表性的样本计算BCEFs.     

Harvesting Increases Reproductive Activity in Himatanthus drasticus (Mart.) Plumel (Apocynaceae), a Non‐Timber Forest Product of the Brazilian Savanna

The harvesting of non‐timber forest products (NTFP) can influence the pattern of resource allocation in plants, affecting their growth, survival, and reproduction. However, only a small number of studies have addressed the impacts of NTFP harvesting on the reproductive phenology of the exploited species. The aim of this observational study was to assess the effects of harvesting and climatic variables on the reproductive phenology of Himatanthus drasticus, a highly exploited medicinal tree from the Brazilian savanna (Cerrado). We evaluated the effects of two different debarking levels (50 and 100%) in comparison to a control (no harvesting). We performed monthly counts of the number of buds, flowers in anthesis, unripe and ripe fruits in each sampled tree (intensity index), as well as the number of trees in each phenophase (activity index), over 2 yr. We used circular statistics tools to compare the effects of each treatment on flower and fruit production and to test whether the reproductive peaks were related to climatic variables. Both the activity and intensity indexes exhibited the same patterns; flower and fruit production were lower in the control, intermediate in the 50 percent debarking group and higher in the 100 percent debarking group. To the best of our knowledge, this is the first study of NTFP to demonstrate an increase in reproductive activity after several years of harvesting. All phenophases were positively correlated with higher temperature and precipitation, as it is common in the Cerrado.     

Photoperiod,temperature, and regional patterns of conceptions in the USA

Twenty-two years of monthly values of birth data for the USA, 1967 through 1988, were analyzed by visual inspection. The data were transformed to remove the influence of length of month and of linear trend, and the values were lagged 9 months to approximate the time of conception. Then, 11-year monthly averages were obtained and plotted as standard scores. Thus two 11-year sets of data were independently analyzed, providing the opportunity of replication. Four distinct temporal patterns were found, differing in month of occurrence of the initial trough and peak and the relative sizes of the two troughs; these characteristics of the temporal pattern change systematically with latitude in the eastern and midwestern states. Data from two other continents, the United Kingdom and Australia, also were analyzed using the same method and found to exhibit a temporal pattern during the year similar to the northern states of the USA. Two biologically relevant variables, temperature and photoperiod, were considered as possible controllers and regulators of the annual rhythmicity. Comparisons of the trends in conceptions with these environmental variables, and inspections of the temperatures and photoperiods at which peaks and troughs in conceptions were found, indicated that these environmental variables could not account for the annual rhythmicity in conceptions.