Hoarding of acorns by granivorous mice and its role in the population processes of Pasania edulis (Makino) Makino

In order to evaluate the role of granivorous mice, Apodemus speciosus Temminck and Apodemus argenteus Temminck, in the regeneration of Pasania edulis (Makino) Makino, an evergreen tree, we conducted field studies examining acorn crops, the population dynamics and hoarding behavior of mice and pre- and postdispersal acorn predation in an evergreen broad-leaved forest dominated by P.edulis in Kagoshima, southern Japan. The study was conducted from 1994 to 2000. Apodemus mice selected sound acorns and hoarded them in the soil after transporting them for distances ranging from 5.4 to 19.9m. This behavior appeared to be beneficial to the establishment of seedlings of P.edulis. However, the positive effects were negated by a high rate of recovery of the acorns hoarded by the mice. A life-table analysis of five cohorts of P.edulis indicated that postdispersal predation of acorns by Apodemus mice was a major contributor to annual variation in the number of new seedlings. A considerable number of acorns germinated only in years with a good acorn crop and a low level of resident mice. These results suggest that Apodemus mice are serious acorn predators rather than important dispersers. After germination, acorns were attacked by the acorn borer at a high rate. From these results, we can conclude that acorn production probably makes a smaller contribution to the regeneration of P.edulis than coppice shoot production at the study site.     

Development of microsatellite markers for Pasania edulis (Makino) Makino, one of the dominant species of lucidphyllous forests in southern Kyushu, Japan

Pasania edulis (Makino) Makino is a Fagaceous tree species endemic to Japan and one of the dominant species in lucidphyllous forests in southern Kyushu, Japan. Recently, P. edulis was attacked by ambrosia beetles, Platypus quereivorus (Murayama) and mass mortality occurred in several areas in southern Kyushu. We isolated and characterized ten microsatellite loci in this species to reveal the genetic structure and gene flow. The number of alleles ranged from 3 to 11 and expected heterozygosities from 0.3761 to 0.8346. The markers described here will be useful for investigating the genetic diversity, genetic structure and gene flow, and planning for conservation of viable population of P. edulis.     

Isolation of endophytic fungi from leaves of Pasania edulis and their within-leaf distributions

 Endophytic fungi were isolated from leaves of Pasania edulis, one of the most important trees of the warm temperate forests in southern Kyushu, by the surface sterilization method using H₂O₂ as a sterilizing agent. From a tree in the Experimental Nursery of Kagoshima University, located at the city of Kagoshima, Phyllosticta sp. and Colletotrichum spp. were frequently isolated. From a stand in a laurel forest in Mt. Takakuma, an ascomycetous fungus (Ascomycete sp. 1) and Phomopsis sp. were frequently isolated. Phyllosticta sp. was isolated more frequently from petiole segments and leaf segments with midrib and Phomopsis sp. from petiole segments and leaf-base segments with midrib than other segments. Colletotrichum spp. were isolated less frequently from petioles and Ascomycete sp. 1 from petiole segments and leaf-base segments with midrib than other segments. As possible causes of such biases in within-leaf distributions of the endophytes, differences in infection modes and negative interactions of major endophytes within leaves are suggested. Received: December 13, 2001 / Accepted: June 7, 2002 Acknowledgments The authors thank the staff members of the Experimental Forests of Kagoshima University for enabling the present study. Correspondence to:K. Hata     

Seed dispersal and seedling establishment of Sarracenia purpurea (Sarraceniaceae)

Plant ecologists continue to grapple with Reid's paradox, the observation that dispersal distances of most herbs and trees are too limited to account for their recolonization of northern latitudes following glacial recession. As global climate changes and natural habitats become increasingly fragmented, understanding patterns of seed dispersal and the potential for long-distance colonization takes on new importance. We studied the dispersal and establishment of the northern pitcher plant Sarracenia purpurea, which grows commonly in isolated bogs throughout Canada and eastern North America. Median dispersal distance of S. purpurea is only 5 cm, which is insufficient to explain its occurrence throughout formerly glaciated regions of North America. Establishment probability of seeds in the field is approximately 5%, and juveniles are normally found clustered around adult plants. The large-scale population genetic structure of this species can be accounted for by rare long-distance dispersal events, but its predictable occurrence in isolated habitats requires additional explanation. Reid's paradox remains an open question, and predicting long-range colonization into fragmented habitats by species with limited dispersal ability is a novel challenge.     

Differential responses of germination and seedling establishment in populations of Tragopogon pratensis (Asteraceae)

The establishment phase is an important bottleneck in the life cycle of plants. It consists of two steps that are rarely separated, i.e., the germination of seeds and the establishment of seedlings. Here we report the results of two experiments in which we independently investigated germination and seedling establishment in the greenhouse, under different grass vegetation treatments representing different regeneration niches. Seeds of Tragopogon pratensis from six populations and two habitat types were studied, three from roadside verges and three from hayfields. Germination percentages and germination speed were higher for seeds from roadside verges than for seeds from hayfields, but were little affected by treatment. In contrast, seedling growth was much lower in the tall grass vegetation, than in the short grass and especially the bare soil treatment. Seedling sizes were generally similar for different populations and habitat types. Our results thus show that the two early steps in the establishment phase of plants may respond very differently to the micro-environment, and may have a different selection history. Insight into the ecology and evolution of life histories may require that germination and establishment are considered separately.     

Seed mass and seedling dimensions in relation to seedling establishment

Several experiments have shown that seedlings from larger-seeded species are better able to survive various hazards during establishment. Previous work has suggested a general mechanism might underpin this outcome. Larger-seeded species might tend to mobilize their metabolic resources over a longer period into the autotrophically functioning structures of the seedling. Consequently relatively more resources would remain uncommitted at any given time during the early period of the seedling’s growth, and available to support respiration during carbon deficit. An important aspect of this larger-seed-later-commitment mechanism would be that at a given time, larger-seeded species would hold more resources uncommitted not just absolutely, but relative to the functional seedling structures that needed to be supported. Here we quantify, across a wide range of phanerocotylar species, an allometric pattern that supports the generality of a larger-seed-later-commitment mechanism as an explanation for superior performance by larger-seeded species in face of the hazards of seedling establishment. Larger-seeded species allocate relatively less to cotyledon area, reflecting the initial functional size of the seedling, and relatively more to dry mass per unit area of cotyledon, reflecting stored metabolic reserves. The shift in relative allocation is progressive, rather than seedlings falling into discrete morphological types. The allometry is similar whether considered as correlated evolutionary divergences (phylogenetically independent contrasts) or as correlation across present-day species. Received: 7 April 1999 / Accepted: 29 March 2000     

Reproductive potential and seedling establishment of the invasive alien tree Schinus molle (Anacardiaceae) in South Africa

Schinus molle (Peruvian pepper tree) was introduced to South Africa more than 150 years ago and was widely planted, mainly along roads. Only in the last two decades has the species become naturalized and invasive in some parts of its new range, notably in semi‐arid savannas. Research is being undertaken to predict its potential for further invasion in South Africa. We studied production, dispersal and predation of seeds, seed banks, and seedling establishment in relation to land uses at three sites, namely ungrazed savanna once used as a military training ground; a savanna grazed by native game; and an ungrazed mine dump. We found that seed production and seed rain density of S. molle varied greatly between study sites, but was high at all sites (384 864–1 233 690 seeds per tree per year; 3877–9477 seeds per square metre per year). We found seeds dispersed to distances of up to 320 m from female trees, and most seeds were deposited within 50 m of putative source trees. Annual seed rain density below canopies of Acacia tortillis, the dominant native tree at all sites, was significantly lower in grazed savanna. The quality of seed rain was much reduced by endophagous predators. Seed survival in the soil was low, with no survival recorded beyond 1 year. Propagule pressure to drive the rate of recruitment: densities of seedlings and sapling densities were higher in ungrazed savanna and the ungrazed mine dump than in grazed savanna, as reflected by large numbers of young individuals, but adult : seedling ratios did not differ between savanna sites. Frequent and abundant seed production, together with effective dispersal of viable S. molle seed by birds to suitable establishment sites below trees of other species to overcome predation effects, facilitates invasion. Disturbance enhances invasion, probably by reducing competition from native plants.     

A census of seedling establishment in sugar-beet crops

Analysis of seedling establishment in 254 experiments from 1970 to 1977 showed that the target of 70%, needed for an adequate plant population and maximum yield, was achieved in only 19% of fields. However, because the plants were only counted once, when they had about six leaves, the cause and timing of the losses could not be identified. This, therefore, gave no sound basis for seeking improvements. Eight studies of all phases of establishment, from sowing to the 6-leaf stage, were then made at Broom's Barn from 1978 to 1981. The studies were on sandy loam or clay loam soils with seedbeds prepared by standard, recommended methods and sown either early or late in spring. These standard treatments were supplemented by plots which tested irrigation or protection from rain, fine or coarse tilths, and the use of a soil applied insecticide or a sterilant. Despite the widely differing weather experienced by these crops, 70% establishment was achieved in seven studies; in the eighth, seedlings emerged at 75% of seed stations, but 31% were then killed, mainly by birds. On average, the drill failed to place seeds at 2·8% of target positions, dead seed was sown at 6%, seedlings died after germination but before emergence at 12·4% and plants died thereafter at 6·5%. Almost every viable seed sown in the field germinated eventually; waterlogging seemed to be the cause of failure in a few small areas where this was not so. In most studies the first 50% of seeds germinated as expected on the basis of the thermal time required in the laboratory test. The remainder sometimes took longer, mainly because they experienced periods when the water supply was inadequate. Seedlings failed to emerge for several reasons; of which the principal ones were dehydration, restriction under a soil crust or stone, and pest damage. It seemed that waterlogging and herbicide damage were important causes in a few cases. After emergence bird grazing was the major cause of death, preferentially of the seedlings which emerged first and had the greatest yield potential. Because losses occurred at every stage and from many causes the solution to the problem of poor establishment requires a multidisciplinary approach.     

Limiting factors for seedling emergence and establishment of the invasive non-native Rosa rugosa in a coastal dune system

The relative importance of seed, habitat and microhabitat limitation has rarely been investigated for invasive non-native species, although this is critical for their effective management and for predicting future range expansion. Rosa rugosa is an abundant non-native shrub in coastal habitats of NW Europe; it is common along the Baltic coast but more scarce in exposed dunes of the North Sea. To investigate whether invasion of exposed dunes is limited by seed, habitat and microhabitat limitation, seedling emergence and establishment were examined in a factorial sowing, transplant and disturbance experiment. Twenty plots were randomly placed in each of five dune habitats (white dune, Empetrum dune, grey dune, outer dune heath, inner dune heath), and studied over 2 years. Seedling emergence in control subplots was zero in all habitats, whereas 96% and 98% of the undisturbed and disturbed seeded subplots produced seedlings. Disturbance had a positive effect on emergence and subsequent survival in white dune, outer and inner dune heath. Seedling survival and growth, and growth of transplanted seedlings, were markedly lower in grey dune. These findings indicate that establishment of R. rugosa is seed-limited in coastal dune habitats, and that the species is able to establish in both active and fixed dunes once seeds have arrived. Although differential seedling emergence and growth indicate that habitats differ in their degree of invasion susceptibility by R. rugosa, the positive influence of small-scale disturbance suggests microhabitat limitation in some dune habitats as well. Dune management should aim to reduce seed production and dispersal of R. rugosa in near-natural sites, and anthropogenic changes of habitat dynamics should be prevented.     

环境因子对蒙古莸种子萌发及幼苗建成的影响

蒙古莸(Caryopteris mongolica)是珍稀濒危的资源性植物,具较高的观赏和药用价值。其分布范围正日渐缩小。通过对内蒙古中西部干旱草原区蒙古莸天然种群实生苗的调查,以及在室内模拟不同环境条件,对蒙古莸种子萌发和幼苗建成进行研究,旨在探究这一物种珍稀、濒危的原因。结果显示:1)自然条件下蒙古莸种子在5—7月大量萌发,但在幼苗生长初期死亡率较高,使得自然种群更新强度仅为0.11株/m~2。2)蒙古莸种子不存在休眠现象,成熟采收后很快即可萌发。萌发对水分要求较宽范,但适宜其种子萌发的温度范围较窄,为25—30℃。3)蒙古莸幼苗生长的最适温度为25℃,能耐受每日短暂的高温胁迫(50℃)。持续的高温、低温和频繁的降水显著增大幼苗死亡率。研究认为,蒙古莸种子萌发的条件与幼苗存活的条件差异较大,同时满足其萌发和幼苗存活和生长的窗口条件比较严苛。其野生生长地的生境条件往往难以满足要求,这是限制蒙古莸通过有性繁殖进行自然种群扩散的主要原因之一。     

Early postfire seed dispersal, seedling establishment and seedling mortality of Pinus coulteri (D. Don) in central coastal California, USA

Seedling recruitment in many highly serotinous populations of Pinus coulteri on California's central coast depends almost entirely on periodic, stand-replacing fire. Compared to serotinous pines of the Mediterranean Basin, little detailed information is available on the postfire demography of California closed-cone pines, including P. coulteri. In September 1996 a wildfire burned the 760-ha American Canyon Research Natural Area (RNA). Using aerial photography, we mapped burn severity of P. coulteri-chaparral woodlands and forests within the RNA. From May to September of 1997, we also quantified seedling establishment and mortality in relation to biophysical site characteristics including fire severity. Seventy-six percent of P. coulteri forests and woodlands experienced high-severity burns, 9% moderate-severity burns, and 15% low-severity or unburned. Of the 53 plots used for seedling counts, 70% were high-severity, 26% moderate-severity, and 4% low-severity. Seedling densities 13 months postfire were low (0.21 m^–2), but seedling mortality also was low (8.4%). Aerial seed bank size increased from north-facing to south-facing slopes and from high-severity to low-severity burns. Seedling recruitment was unrelated to burn severity and increased with the size of the canopy seed bank (cone density). Many seedlings established from rodent seed caches; 23% of the seedlings established in clumps from seeds cached by Dipodomys agilis, Chaetodipus californicus and Peromyscus maniculatus. Pinus coulteri seeds have low potential for dispersal by wind, but secondary dispersal by rodents moves seeds away from source trees and into neighboring chaparral. We discuss the potential importance of rodent seed caching to postfire demography of California and Mediterranean serotinous pines.     

小朱兰在广东的首次记录及其意义

报道了广东省朱兰属1新记录——小朱兰,并论述了它的分类学、区系学意义。     

Distribution of hydraulic resistance in seedlings,sprouts and an adult tree ofPasania edulis Makino

Hydraulic resistance is an important factor in predicting water status. Hydraulic resistance of petiols, stems and branches, and roots was measured inPasania edulis Makino in order to compare the distribution of resistance between current seedlings, current stump sprouts and a 16 year old adult tree. Total resistance showed only minor variations despite large variations in plant size. This result is thought to be consistent with allometry between leaf mass and supportive organ mass, and with changes in permeability of conductive organs. Root resistance was low in sprouts and the adult tree due to their mature root systems. Current seedlings with undeveloped root systems had high root resistance. The proportion of petiol resistance in total resistance was high compared to the proportion of their conductive distance, and was thought to be a limiting factor of tree water status. The petiol resistance of the adult tree leaves was higher than for seedling and sprout leaves. From a comparison with the leaf water relation characteristics, the petiol resistance was thought to be provided as low values for intolerant leaves against water stress in order to compensate water inflow, and high values for tolerant leaves to regulate water inflow.     

Post-fire seedling establishment in Florida sand pine scrub

Abstract. This study deals with a quantification of pre- and post-fire seedling establishment and microsite characteristics in two Florida sand pine scrub sites burned in May 1993. In addition, life history characteristics related to seedling establishment are described for five perennial species –Calamintha ashei, Chapmannia floridana, Eriogonum floridanum, Garberia heterophylla and Palafoxia feayi. Post-fire seedling establishment in sand pine scrub was sparse (median = 1, 12 seedling/m²), with 17 of 35 species establishing seedlings. Chapmannia, Eriogonum, Garberia and Palafoxia resprouted and flowered after fire; Eriogonum and Garberia had strong post-fire seedling establishment responses within 19 months post-fire. Calamintha individuals were killed by fire, but this species had a strong post-fire seedling establishment response, presumably from seeds in a soil seed bank. Eriogonum and Calamintha seedlings established preferentially in plots centered on conspecific adults. For these species with poor seed dispersal, spatial patterns of seedling establishment may be influenced more by pre-fire adult plant location than by post-fire microsite conditions. Post-fire seedling density in sand pine scrub was much lower than in California chaparral and South African sand plain lowland fynbos.     

The effect of frit fly (Oscinella frit) control measures on the establishment of seedling ryegrass (Lolium spp.)

In four experiments from 1981 to 1983 August-sown perennial (Lolium perenne) and Italian (L. multiflorum) ryegrass were exposed to frit fly attack by oviposition on the seedlings. Responses to pesticide treatment were detected at autumn harvests. Even at low sowing rates pesticide application did not ultimately establish a better sward and, owing to a tendency towards spring reversal of autumn yield responses, even temporary returns were negligible. As frit fly numbers were unusually low the autumn response to pesticide was sufficient to suggest that frit fly is always likely to be an influential factor in ryegrass sown in early August in this area. Later sowings are less likely to be affected. The yield response was related to the numbers of adult flies present 2–7 wk after sowing. Neither grass species was consistently more affected than the other. Additional seed (compared with a sowing rate below normal commercial rates) and the inclusion of fertiliser at sowing also gave only small temporary returns and failed to establish a better sward. It is suggested that routine protection against frit fly attack is of at least equal value to the other two variables in an early August sowing.     

Rice cultivar difference in seedling establishment in flooded soil

Seedling establishment of direct sown rice plants is less successful in flooded soil than in drained soil. This study was conducted to clarify the difference in morphogenesis of rice seeds sown in flooded and drained soils and to identify the morphological characteristics responsible for successful establishment of cultivars in flooded soil. Rice cultivars ASD1 and IR41996–50–2–1–3, superior in seedling establishment in flooded soil, and Mahsuri and IR72, non-superior (control), were sown at a depth of 25 mm in soil flooded with 25 mm of water or in drained soil. The coleoptile and 1st leaf emerged from the soil surface simultaneously in drained soil while in flooded soil the coleoptile emerged first. The coleoptile of superior cultivars, unlike the controls, elongated more in flooded soil than in drained soil. In flooded soil, the development of mesocotyl, 1st leaf, and roots were inhibited to a greater extent in the controls, than in the superior cultivars. In sealed flasks in which gas containing 0–21% O2 was exchanged daily, the superior cultivars developed longer coleoptiles than the controls at lower O2 concentrations. These findings suggest that the reason superior cultivars grow better in flooded soil than the controls is that the coleoptile elongates faster and longer in hypoxia and is able to reach the soil surface where O2 is available.     

Development of the Embryo Sac in Amitostigma kinoshitae (Makino) Schltr. (Orchidaceae)

The embryo sac of Amitostigma kinoshitae was studied. The ovuleis anatropous, bitegmic, and tenuinucellate. The inner integumentalone forms a micropyle. The megaspore of a tetrad nearest tothe chalaza develops into an eight-nucleate embryo sac of thetypical Polygonum-type. Double fertilization takes place normally.     

The role of seed depth,litter, and fire in the seedling establishment of amphicarpic peanutgrass (Amphicarpum purshii)

Summary Amphicarpum purshii is an annual grass which mostly grows in disturbed areas of the New Jersey Pine Barrens, USA. It is amphicarpic, producing spikelets (and seeds) both above and below the soil surface. Previous research has shown that subterranean seed production ensures reproduction in the event of a major disturbance such as fire and results in rapid post-burn colonization of these sandy habitats. The effects of fire, litter, and seed depth were further examined by planting subterranean seeds at four depths in 16 litter-covered flats buried at ground level and comparing plants arising from burned flats with those in undisturbed litter-covered flats. At 0 and 1 cm depth, rates of seedling emergence were lowest in burned flats. Surface-sown seeds produced seedlings more likely to desiccate. Sowing depth had a greater influence on most measured characters than burning treatments. The mean depth of subterranean seed placement by Amphicarpum is 3.5 cm and this coincides with the seed depth from which plants showed the greatest height growth, shoot biomass, and reproductive output. In a second experiment, subterranean seeds on the bare soil surface in clay pots were more likely to lose viability and less likely to germinate than seeds protected by litter or burial in soil. In addition to providing protection from fire, placement of seeds below ground in the sandy habitat of peanutgrass provides conditions more suitable for seed survival and subsequent seedling establishment.