古田山常绿阔叶林木本植物与生境的相关性

 用来解释物种丰富的热带雨林物种共存机制的生态位理论和中性理论已经引起了生态学家广泛的关注,而对亚热带常绿阔叶林物种共存机制及物种多样性维持的研究很少。笔者采用卡方检验和典范对应分析方法,对古田山典型常绿阔叶林24hm2样地中胸径不小于10mm、个体数大于18的106种木本植物与平均海拔、坡度和凸度3个小地形生境指标进行生境关联分析。卡方检验结果表明,106种木本植物中,84种(79%)至少与一种生境显著相关(P<0.05);CCA及随机化排列测验方法分析结果表明,大部分物种的分布受生境因子限制;因此,古田山24hm2样地木本植物的分布与生境显著相关,生境特化是亚热带典型常绿阔叶林在局域尺度上木本植物多样性维持的主要机制。     

干旱胁迫对3种针茅种子萌发期抗旱性影响的研究

以采自宁夏回族自治区云雾山的本氏针茅、大针茅和克氏针茅种子为研究材料,用不同渗透势浓度的聚乙二醇(PEG-6000)模拟干旱胁迫,探讨了干旱胁迫对3种针茅种子萌发特性的影响。结果表明,随着PEG浓度的增加,3种针茅种子的发芽率、活力指数、幼苗的鲜重和抗旱指数均呈下降趋势。其大针茅下降趋势最为明显(p<0.05),而低浓度PEG(5%PEG)对本氏针茅的萌发及生长有一定促进作用。低浓度PEG克氏针茅的发芽率以及幼苗鲜重与对照差异不显著,表明克氏针茅有一定的抗旱性。PEG对幼苗生长的抑制效应比幼根大。3种针茅种子萌发期的抗旱能力依次为:本氏针茅>克氏针茅>大针茅。     

干旱胁迫对窄叶鲜卑花种子萌发及幼苗生长的影响

[目的]研究干旱胁迫对窄叶鲜卑花种子萌发及幼苗生长的影响,为野生种驯化和种群恢复提供参考。[方法]以窄叶鲜卑花种子为实验材料,采用不同浓度聚乙二醇(PEG-6000)模拟干旱胁迫环境,研究干旱协迫强度对窄叶鲜卑花种子的吸胀速率、发芽率、发芽势、发芽指数、活力指数和种子抗旱萌发指数及幼苗生长情况的影响。[结果]随着干旱胁迫程度的加剧,窄叶鲜卑花种子的吸水过程表现出急速吸水期、缓慢上升期和吸水平稳期3个阶段;其发芽率、发芽势、发芽指数、活力指数和种子抗旱萌发指数及苗高、根长,苗重与胁迫强度均呈负相关;当PEG浓度达30%时,种子萌发完全被抑制。另一方面,种子群体萌动、萌发和出苗达50%所需时间随胁迫强度的增加而越发延迟,且各阶段对环境临界水势要求不同,出苗阶段最为严格,表明种子出苗过程对环境水分胁迫较为敏感,耐旱能力较弱。[结论]干旱胁迫显著抑制了窄叶鲜卑花种子的萌发和幼苗生长,也说明水分是窄叶鲜卑花种子萌发和幼苗形成的主导因素之一,在较干旱地区种植需要考虑水分的供给。     

红壤侵蚀退化地马尾松幼苗生长及养分利用效率对施肥的响应

马尾松是南方红壤侵蚀区的先锋树种,由于受土壤贫瘠的限制,植物生长缓慢.以树龄1年的马尾松为研究对象,研究了不同施肥处理对马尾松的生长特征以及生物量、植株养分含量和养分利用效率的影响.设置了1个对照(不施肥,CK)和3种施肥方式:单施复合肥(0.94,1.89,3.56 g);复合肥与微生物菌肥混施((0.94+8.00...     

Seedling recruitment and survival of two desert grasses in the monte of Argentina

In the Monte Austral Neuquino, Argentina, vegetation is arranged in patches. Understanding the mechanisms involved in their distribution is critical for preventing desertification. The working hypothesis was that vegetation patches reduce environmental stress on the plants. Plant patches were classified into four microenvironments: windward; below the dominant shrubs (subcanopy); vegetation at the patch periphery (canopy edge) and bare patch interspaces (open). We determined seedling survival of the dominant species in each microenvironment, using a marking method of seedlings established from sown seeds. In addition, we measured the environmental characteristics in the four microenvironments, and associated them with seedling survival. Study species were the perennial grasses Leymus erianthus (Phil.) Dubcovsky, Stipa neaei Nees ex Steudel and Poa ligularis Nees ex Steudel, and the shrubs Larrea divaricata Cav. and Atriplex lampa Gill ex Moquin. Results supported the hyphothesis only for L. erianthus and S. neaei (but not for the other three species that showed higher seedling survival in the subcanopy than in the patch interspaces after 1 year from sowing). This study determined that (1) reduced environmental stress does not guarantee seed germination and seedling survival of a given species in the plant community and (2) seedling establishment will not be possible for any species of the plant community in the patch interspaces under the study conditions in the region. This is mostly because soil temperatures can reach up to 50°C in the patch interspaces in years of scanty precipitation during late spring and summer. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence of Growing Medium and Seed Size on Germination and Seedling Growth of Pinus gerardiana Wall.

Pinus gerardiana Wall. is an important nut-producing pine having restricted distribution in the world. It has been observed that natural regeneration in the species is extremely poor or entirely lacking. The species has erratic and infrequent seed years, dormancy-related problems, and slow growth of seedling, which reduces its regeneration process in natural habitats. Therefore, we investigated the effect of growing medium and seed size on germination and seedling growth of the Pinus gerardiana. The seeds were categorized into two sizes, viz, small (<2.35 cm) and large (>2.35 cm) and five growing medium treatments were used, viz, Soil:Sand:FYM; Soil:Sand:Moss:FYM; Soil:Moss:Vermicompost; Soil:Sand:Vermicompost; and Soil:Sand:Moss:Vermicompost, for assessing their impact on germination and seedling growth. It was observed that, among different growing medium treatments, higher germination and seedling growth parameters were recorded, when Soil:Sand:Moss:Vermicompost was used for the study. Between different seed sizes, higher germination and seedling growth were recorded when seed size was large.     

Control of pitch pine seed germination and initial growth exerted by leaf litters and polyphenolic compounds

We investigated the influence of three concentrations of water extracts of three leaf litter species (pitch pine, huckleberry and white oak) and a mixture of all litters on the germination of pitch pine seeds and initial seedling growth in a microcosm experiment. All three plant species are important components of the pine barrens ecosystems in New Jersey, where it has been seen that pine seedling recruitment occurs only after stand replacing fire or in disturbed sites, where surface organic soil horizons and leaf litter have been removed. Leaf litter extracts did not influence seed germination, but significantly reduced seedling growth at high concentrations. There was little difference between the leaf litter species in growth suppression. As charcoal is a natural residue on the forest floor following fire, its influence on growth suppression was examined; it has been shown to immobilize polyphenols. Charcoal removed the inhibitory effect of leaf litter extracts and allowed the fertilizer effect of nutrients leached from the leaves to enhance seedling growth, particularly at the higher concentration of litter extract used. Responses to litter extracts were compared to four pure phenolic compounds, catchecol, p-coumaric acid, p-hydroxybenzoic acid and tannic acid. None of these compounds suppressed pine seedling growth, suggesting that these phenolics are not allelopathic to pine seedlings. The results are discussed in the context of fire as a driving factor in these oligotrophic and seasonally dry ecosystems and the interactions between nutrient supply and allelopathic chemistry of different leaf litters.     

Provenance variation in seed germination and seedling growth of Acacia nilotica ssp. indica in India

Summary Acacia nilotica ssp. indica, a multipurpose tree species occurs throughout semi-arid India. The present study reports the variation in seed germination and seedling growth of 21 sites (provenances) collected between the latitude 11°N and 31°23N, and 19 m to 650 m altitude throughout India. There were significant differences (P<0.05) between the sites for seed germination that varied from 16 to 90% in the incubator, and 14 to 84% in the nursery. Significant variations were also observed in seedling growth up to 28 days in the incubator. There was no significant relationship between seed germination and seedling growth and the latitude or longitude of the original seed source. However, in general the South Indian provenances showed lower germination as compared to North Indian provenances. The observations are important for selection of vigorous provenances concerning seed germination and early seedling growth.     

Biomonitoring of atmospheric mercury in the vicinity of Kilauea,Hawaii

The release of mercury from volcanic eruptions on the Island of Hawaii has been well documented, but the dispersion characteristics have not previously been studied in detail. Samples of lichens were collected from around the island, and subsequent analysis showed levels ranging from < 8 to 59 µg Hg g^-1. The distribution of the accumulation of mercury clearly shows that there is a major input from the active eruption sites, but that this is significantly modified by variations in wind patterns. Superimposed on this regional distribution are two localised sites where the mercury accumulation is exceptionally high; this is attributed to the release of steam from the circulation of shallow ground waters.     

The anatomy of a (potential) disaster: Volcanoes, behavior, and population viability of the short-tailed albatross (Phoebastria albatrus)

Catastrophic events, either from natural (e.g., hurricane) or human-induced (e.g., forest clear-cut) processes, are a well-known threat to wild populations. However, our lack of knowledge about population-level effects of catastrophic events has inhibited the careful examination of how catastrophes affect population growth and persistence. For the critically endangered short-tailed albatross (Phoebastria albatrus), episodic volcanic eruptions are considered a serious catastrophic threat since approximately 80% of the global population of ∼2500 birds (in 2006) currently breeds on an active volcano, Torishima Island. We evaluated how short-tailed albatross population persistence is affected by the catastrophic threat of a volcanic eruption relative to chronic threats. We also provide an example for overcoming the seemingly overwhelming problems created by modelling the population dynamics of a species with limited demographic data by incorporating uncertainty in our analysis. As such, we constructed a stochastic age-based matrix model that incorporated both catastrophic mortality due to volcanic eruptions and chronic mortality from several potential sources (e.g., contaminant exposure, fisheries bycatch) to determine the relative effects of these two types of threats on short-tailed albatross population growth and persistence. Modest increases (1%) in chronic (annual) mortality had a 2.5-fold greater effect on predicted short-tailed albatross stochastic population growth rate (lambda) than did the occurrence of periodic volcanic eruptions that follow historic eruption frequencies (annual probability of eruption 2.2%). Our work demonstrates that periodic catastrophic volcanic eruptions, despite their dramatic nature, are less likely to affect the population viability and recovery of short-tailed albatross than low-level chronic mortality.     

盐胁迫下外源钙对高羊茅种子萌发和幼苗离子分布的影响

该文模拟了上海市临港新成陆地盐渍化土壤的盐分特点,并在100 mmol/L NaCl盐胁迫下,以常见牧草和草坪草高羊茅（Festucaarundinacea）为材料,在人工气候室可控制条件下,进行了盐胁迫下种子萌发和幼苗盆栽试验,用不同浓度的CaCl2（5、10、20、40、80 mmol/L）处理,研究高羊茅种子萌发和幼苗生长状况,重点研究了矿质元素Na^＋、K^＋、Ca^2＋和Mg^2＋在植株地上部分和地下部分的分布。研究表明：适当浓度的外源CaCl2浸种处理能缓解高羊茅种子受到的盐胁迫伤害,促使种子提前萌发,20 mmol/L CaCl2浸种处理能显著提高种子萌发率,但高浓度（80 mmol/L）的外源钙处理对高羊茅种子萌发不利;适当浓度的CaCl2处理能促进幼苗地上部分生长,降低高羊茅根冠比、稳定植物细胞膜、维持离子平衡、提高植物耐盐性,但是高浓度（80 mmol/L）CaCl2处理会对植物幼苗生长造成伤害。     

三种锦鸡儿属植物的克隆生长特性及其植被恢复意义

 了研究适于甘肃定西黄土丘陵沟壑区植被恢复的主要灌木种,以本地种白毛锦鸡儿(Caragana licentiana) 和甘蒙锦鸡儿(C．opulens)以及外来种中间锦鸡儿(C．intermedia)为对象,研究其克隆生长特性。白毛锦鸡儿和甘蒙锦鸡儿由根状茎产生很多无性系分株,均为松散游走型克隆生长构型,其根状茎错纵复杂,结成网状结构。在黄土丘陵沟壑区相对干旱的环境以及动物胁迫下,白毛锦鸡儿种子繁殖受到限制,无性繁殖有助于其种群的更新和扩展。白毛锦鸡儿的分株种群在半阳坡比在半阴坡有显著大的分株数、根状茎数、基株最大半径、根状茎长和根状茎生物量分配,反映出其形态的可塑性。游走型的克隆生长构型和根状茎的网络结构,赋予白毛锦鸡儿很好的水土保持性能。中间锦鸡儿为单轴型构型,在定西地区不产生无性系分株。     

饱和紫色土初始态和稳定态细沟水力学特征研究

细沟水力学特征是影响坡面土壤侵蚀的重要动力因素.不同侵蚀阶段细沟形态影响水流动力学特征,进而影响细沟侵蚀发育与形态演变.试验以饱和紫色土为研究对象,在测量得到不同流量(2,4,8 L·min-1)及坡度(5°,10°,15°,20°)下初始态细沟和稳定态细沟径流流速的基础上,计算得到初始态和稳定态细沟水力学参数,包括平...     

Spatial heterogeneity of loess contour tilled microtopographic slope in rainfall erosion

Loess tilled surface is the geographical unit for the quantitative study of the soil erosion process. Contour tillage has been proved to be the most effictive measure for soil and water conservation in the Chinese Loess Plateau. Studies on the spatial heterogeneity of loess tilled surfaces will contribute to the understanding of the mechanism of erosion evolution. For this, a laboratory experiment was performed on contour tilled sloping surfaces where the hydrological-erosive processes were simulated. At different erosion stages, point cloud measurements were made using a terrestrial laser scanning system (TLS); then the heterogeneity depending on detrending and directionality were analysed by both the semivariogram method and the rescaled range analysis method. Results showed that: (1) the fractal dimensions D_S and D_R were equivalent when determined from either the semivariogram method or the rescaled range analysis method, although the semivariogram method appears to be more reliable in identifying the specific stage of the erosion evolution process; (2) the contour tilled microtopographies had an anisotropy behavior depending on direction; (3) the fractal dimension (either D_S or D_R) in different erosion stages was less than 1.5, which indicates that the microtopography of the sloping surface exhibits characteristics of persistent fractional Brownian motion and positive spatial autocorrelation. Irrespective of tillage measure and slope percentage, the sloping surface can be regarded as having random roughness. The results reveals a quantitative relationship between microtopography and sloping erosion. Also, it may provide guidance for further studies regarding the spatial variability and heterogeneity of various tilled slopes on the microtopographic scale.     

随机模拟畦面微地形分布及其差异性对畦灌性能的影响

畦面微地形对畦灌性能具有较大影响,该文针对畦面相对高程分布具有随机性和空间相关性的特点,基于Monte-Carlo随机模拟方法和半方差分析方法建立了随机模拟畦面微地形分布状况的方法,并借助二维地面灌溉模型评价随机模拟的畦面微地形分布状况及其差异性对畦灌性能的影响。研究结果表明：同一畦面相对高程标准偏差值下随机模拟的畦面微地形分布间存在的差异性对畦灌性能的影响取决于该值大小,等于或大于3 cm以上的畦面微地形分布间存在的较大差异对畦灌性能影响显著,而小于3 cm的畦面微地形间存在的分布差异对畦灌性能影响相对较小,此条件下随机模拟的任一组畦面微地形分布状况均具有典型代表性,可直接作为二维地面灌溉模型的输入数据用于评价畦面微地形分布状况对畦灌性能的影响。     

霞浦沿海花岗岩侵蚀地引种相思类树种的试验研究

针对沿海花岗岩侵蚀地造林树种匮乏的局面以及生态系统稳定性差等现状，开展引进相思类树种造林试验。重点调查了不同相思树种在沿海花岗岩侵蚀地上的生长量和改良土壤效应，并应用统计学方法进行分析比较。试验结果表明，沿海花岗岩侵蚀地选择相思类树种造林能起到很好的水土保持作用，而且有助于改善造林地的土壤条件，提高林地肥力。引进相思类树种中以灰木相思的造林成效最好，纹荚相思次之，最后是卷荚相思。本研究为今后闽东沿海花岗岩侵蚀地的治理提供了重要的理论依据。     

Seed germination and seedling survival of two threatened endemic species of the northwest Iberian peninsula

We examined germination and seedling survival of Petrocoptis grandiflora and Petrocoptis viscosa (Caryophyllaceae), two narrow endemic species from the northwest Iberian Peninsula. The experiments were carried out with seeds of three of eight populations of P. grandiflora and one of the three sole populations of P. viscosa. Under natural conditions, both P. grandiflora and P. viscosa produce very large numbers of seeds. However, the specific microhabitat of these species (cracks and crevices of limestone rockfaces) has very marked effects on seed germination, and subsequent seedling survival. In the present study, we examined the effects of light, cold treatment and seed weight on germination capacity. In the case of P. grandiflora, we also compared the germination of seeds of the different populations. In addition, we assessed seedling survival over a 1-year period. Seeds maintained in darkness showed higher germination percentages than seeds maintained with a 12:12 h photoperiod. The application of a short period of cold prior to germination had no significant effect in either species. In the case of P. grandiflora, population of origin had a significant effect on germination percentage. Of all the factors considered, seed weight was the most important source of variability, both in seed germination and subsequent seedling survival. In both species in the natural habitat, less than 10% of germinated seeds survived by the end of the year. Seedling survival was affected by microhabitat. Seedlings in non-rockface soil microhabitats were more likely to suffer herbivory or interspecific competition than seedlings in crevices in the rockface.     

Weed abundance and soil seedbank responses to tillage systems in continuous maize crops

Weed abundance in crops undergoes frequent changes, often due to changes in tillage practices. Annual species, with quick germination, a short vegetative stage, profuse seed production and long-lived seeds become problematic under zero-tillage systems. Portulaca oleracea L. and Amaranthus blitoides L. are widespread weeds in the Mediterranean area, prominent in irrigated crops. We studied the total weed abundance in the field, and specifically these two species (Portulaca oleracea and Amaranthus blitoides) with high frequency of occurrence in monoculture maize, from 2012 to 2014, in the field and soil seedbank. Results showed significant differences between zero-tillage (ZT) and conventional tillage (CT) systems on total weed abundance and relative abundance of Portulaca oleracea. Total weed abundance decreased in ZT plots (from 136 plants m^?2 to 25 and 46 plants m^?2, in 2013 and 2014 respectively). The same trend was observed in Portulaca oleracea recorded in ZT plots, but the abundance of Amaranthus blitoides did not vary in this system. Weed seedling germination and weed seed numbers both of total weed seedbank and Portulaca oleracea, were greater in ZT plots compared to CT, regarding Amaranthus blitoides seedling germination and seed count, the values did not increase with ZT, in continuous maize crops.     

Autotoxicity of Phthalate Esters in Tobacco Root Exudates:Effects on Seed Germination and Seedling Growth

Autotoxicity is one of the major factors that impede continuous cropping. It is defined as the toxic influence of chemicals released from one plant species on the germination and growth of individuals of the same species. Here, in order to exam the autotoxicity of tobacco root exudates, root exudates were collected from tobacco plants grown both in cultural solution and on natural soil. Using ultraperformance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry, main autotoxic chemical substances in the root exudates were identified. The autotoxic effects of suspected autotoxins on seed germination (including germination rate, germination potential, germination index, and vigor index) and seedling growth were analyzed. Dibutyl phthalate (or diisobutyl phthalate), dioctyl phthalate, and diisooctyl phthalate were identified in tobacco root exudates. It was observed that high concentrations (greater than 0.5 mmol L^-1) of each identified phthalate ester caused significant (P < 0.05) inhibition of tobacco seed germination and seedling growth. It can be concluded that phthalate esters such as dibutyl phthalate, diisobutyl phthalate, and diisooctyl phthalate in tobacco root exudates may play an important role in tobacco autotoxicity.     

Non-native anecic earthworms (Lumbricus terrestris L.) reduce seed germination and seedling survival of temperate and boreal trees species

Recent studies have shown that the introduction of non-native earthworms in previously earthworm-free soils may have negative impacts on the recruitment of certain understory plant species in northern temperate forests. There is a need, therefore, to understand the mechanisms that may underlie this phenomenon. A microcosm study was conducted to test the effects of the anecic earthworm, Lumbricus terrestris L., on the number of days for germination, % seed germination, seedling survival and seedling biomass of 14 tree species native to southern Quebec (Canada). Seeds of these species were germinated and grown in the presence or absence of L. terrestris. The presence of earthworms significantly reduced % seed germination of seven tree species, as well as seedling survival of three tree species. The germination date of three tree species was significantly affected, either positively or negatively, by the presence of earthworms. Earthworms had no effect on seedling biomass. Results suggest that the introduction of L. terrestris into forested ecosystems of southern Québec may potentially alter overstory composition through several mechanisms that differentially affect the recruitment of various tree species in the understory.