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Understanding the mechanisms generating species distributions remains a challenge, especially in hyperdiverse tropical forests. We evaluated the role of rainfall variation, soil gradients and herbivory on seedling mortality, and how variation in seedling performance along these gradients contributes to habitat specialisation. In a 4-year experiment, replicated at the two extremes of the Amazon basin, we reciprocally transplanted 4638 tree seedlings of 41 habitat-specialist species from seven phylogenetic lineages among the three most important forest habitats of lowland Amazonia. Rainfall variation, flooding and soil gradients strongly influenced seedling mortality, whereas herbivory had negligible impact. Seedling mortality varied strongly among habitats, consistent with predictions for habitat specialists in most lineages. This suggests that seedling performance is a primary determinant of the habitat associations of adult trees across Amazonia. It further suggests that tree diversity, currently mostly harboured in terra firme forests, may be strongly impacted by the predicted climate changes in Amazonia., (© 2016 John Wiley & Sons Ltd/CNRS.)

Premise of research. Seed ontogeny between fertilization and seed maturity is a neglected life history stage in demographic studies, yet this period may have profound consequences for seed set and seedling vigor. For plant species with multiovulate linear fruits, it is possible to record the relative position of each ovule, thereby allowing investigators to assess whether ovule development occurs at random or whether it exhibits unique discernible patterns within fruits. We studied effects of ovule position on patterns of ovule development, seed mass, and seedling size within linear pods of Cercis canadensis. Methodology. Fruits were collected from multiple trees at each of three sites in southeastern Michigan. Intraovary ovule position and developmental fate (i.e., undeveloped ovule, aborted ovule, insect-damaged seed, and mature seed) and seed mass were determined. Seedling performance from three seed size classes was also monitored. Seedling traits included days to emergence, height, leaf area, and seedling biomass. Pivotal results. Three-fourths or more of all ovules within fruits across the populations reached seed maturity. Patterns of seed maturation and abortion were nonrandom and significantly depended on populations, individuals, and ovule positions within fruits. Probability of seed maturation within individual fruits was lowest at the basal end and highest at either the center or the distal end, suggesting the existence of a fertilization gradient. Conversely, frequencies of undeveloped ovules and aborted seeds were highest at the bases of fruits. Insect-damaged seeds accounted for 1%–3% of all ovules and occurred randomly. Seeds located in basal sections of fruits were also smaller than seeds located in central and distal sections. Seed mass was positively correlated with all measures of seedling performance. Conclusions. Patterns of ovule development and seed maturation were determined to be nonrandom within fruits of C. canadensis. Ovule position influences abortion and maturation of seeds, seed mass, and early seedling vigor and has the potential to affect overall plant fitness. [ABSTRACT FROM AUTHOR]

Understanding the adaptation of plant species will help us develop effective breeding programs, guide the collection of germplasm, and improve the success of population restoration projects for threatened species. Genetic features correlate with species adaptation. Acer yangbiense is a critically endangered plant species with extremely small populations (PSESP). However, no information was available on its seed germination and seedling growth in populations with different genetic characteristics. In this study, we investigated seed germination and compared the performance of 566 seedlings in 10 maternal half-sib families cultivated in Kunming Botanical Garden. The results showed that A. yangbiense seeds required an average of 44 days to start germinating, with a 50% germination rate estimated to take about 47–76 days, indicating slow and irregular germination. There is a trade-off between the growth and survival in A. yangbiense seedlings, with fast growth coming at the cost of low survival. Groups that were able to recover from a recent bottleneck consistently had higher relative growth rates. High genetic diversity and low levels of inbreeding are likely to be responsible for their improved survival during drought conditions and rapid growth under optimal environmental conditions. Our results suggest that maternal genetic traits might be used as indicators for conservation and population restoration. These findings provide us with new information that could be applied to support ex situ conservation and reintroduction of threatened species. [ABSTRACT FROM AUTHOR]

Tree mycorrhizal type plays an important role in promoting plant species diversity and coexistence, via its mediating role in conspecific negative density dependence (CNDD), i.e., the process by which an individual's performance is impaired by the density of conspecific plants. Previous findings suggest that ectomycorrhizal (EM) tree species are generally less susceptible to CNDD than arbuscular mycorrhizal (AM) tree species, due to the chemical and physical protection that EM fungi provide their host with. We examined how CNDD effects on leaf herbivory, seedling growth, and survival differ between AM and EM seedlings of ten tree species collected over 3 years in an old-growth temperate forest in northeastern China. We found that AM and EM seedlings differed in how conspecific density affected their leaf herbivory, seedling growth, and survival. Specifically, AM seedlings leaf herbivory rates significantly increased with increasing conspecific seedling and adult density, and their growth and survival rates decreased with increasing conspecific adult density, these patterns were, however, absent in EM seedlings. Our work suggests that AM seedlings have a performance disadvantage relative to EM seedlings related to the negative effects from conspecific neighbors. We highlight the importance of integrating information on seedling leaf herbivory, seedling growth, to provide further understanding on potential mechanisms driving differences in CNDD between AM and EM tree seedlings. [ABSTRACT FROM AUTHOR]

Monoculture tree plantations have been preferred by farmers and companies because they maximize the production of specific products and are easier to manage, while multispecies plantations can provide multiple ecosystem services but have still been adopted at very limited scales. One potential midway to enhance the ecological contribution of monoculture plantations is to introduce native tree species in the plantation understory. We conducted phylogenetically explicit enrichment planting experiments beneath the monocultures of two tree species native to the Brazilian Atlantic Forest to assess if the evolutionary distance of each seedling species to the overstory tree explained variations in seedling performance. We planted in the understory of two replicate plantations of species Esenbeckia leiocarpa Engl. (Rutaceae; 38 and 25 years old) and Zeyheria tuberculosa (Vell) (Bignoniaceae; both replicates were 30 years old) six native tree species, ranging in their evolutionary distances to these overstory species. We assessed individual seedling survival and height at 1, 7, and 19 months after planting. We found a weak yet significant, positive correlation between seedling performance (growth and survival) and the phylogenetic distance of the planted seedling to the overstory species, which was driven by the poor performance of conspecifics. Seedlings of the same order and class as the overstory trees showed a significantly lower risk of death compared to conspecifics and to the furthest relative, Cryptocarya aschersoniana. These findings highlight that very close relatives to the overstories should be avoided when planting beneath monoculture plantations, but that knowledge on species‐specific requirements is still the most important for a successful planting. [ABSTRACT FROM AUTHOR]

Rodents regularly rely on emerged epicotyls to locate and remove cotyledons still containing valuable nutrients. However, the extent to which acorn characteristics influence tolerance to post‐germination predation has received little attention.Here, we investigated the impact of cotyledon removal following epicotyl emergence on seedling performance and survival of seven oak (Quercus) species. We imitated cotyledon predation at different stages of seedling establishment and development in order to detect effects on seedling height, leaf number and tissue/component mass.Seedling growth and survival were negatively affected by cotyledon loss regardless of oak species. However, these negative effects decreased as the epicotyl length at which cotyledons were removed increased. We also found that there was a threshold epicotyl length above which seedling survival and performance were relatively unaffected in white oak species compared to red oak species.Following cotyledon removal, early germinating white oak (section Quercus) seedlings survived and/or grew better than the late germinating red oak (section Lobatae) seedlings. This was likely caused by a difference in dependence on cotyledon reserves, which ultimately affected the ability of seedlings to tolerate cotyledon removal.Synthesis. From an evolutionary perspective, this is likely to follow from the early germination in white oaks and the ability of seed consumers to locate young seedlings from the emerging epicotyls. Our study has implications for forest regeneration by suggesting additional opportunities for white oak species to establish following epicotyl emergence. Future studies should consider quantifying the rates of post‐germination cotyledon loss. [ABSTRACT FROM AUTHOR]

In Andean Patagonia, Argentina, severe wildfires produce high mortality in Austrocedrus chilensis forests. Owing to its high timber quality, A. chilensis trees are generally salvage logged right after wildfires. Post-logged areas result in open, denuded stands with low herbaceous or shrub cover, which precludes natural A. chilensis regeneration. In severely burned A. chilensis stands, we determined how different site conditions (salvage logging, SL, and without logging, WL), and the combination of different methods of control of above- and belowground competition and micro-environmental factors (incident radiation, soil temperature and soil moisture) affected survival, growth and hydric status of planted A seedlings. Two growing seasons after plantation, seedling survival was lower than 10% at SL sites, whereas it was near 90% at WL sites. Four seasons after establishment, and regardless of competition treatments, no seedlings survived at SL sites, whereas over 75% survived at WL sites. Radiation attenuation by canopy of WL sites benefitted A. chilensis seedling survival, and no additional control of early successional herbaceous species should be necessary to attain high seedling survival 4 years after restoration. Selective logging, by leaving ~50% of burned snags, and active restoration practices, may help reconcile economic needs of society and ecological requirements of A. chilensis for recovering former structure and functions. We determine how post-fire salvage logging (SL) v. without logging (WL) affected Austrocedrus chilensis seedling survival and growth under different aerial and root-competition treatments. High radiation levels at SL sites precluded A. chilensis seedlings survival, whereas aerial or root competition had insignificant effects. Remaining snags at WL sites attenuate radiation, allowing high seedling survival. [ABSTRACT FROM AUTHOR]

Early regeneration is a critical life stage that affects the future species composition of forests. Knowledge about regeneration success under different environmental conditions allows better understanding of forest dynamics. We studied the effects of seedbed conditions on the establishment and performance of seedlings of pedunculate oak, beech and red oak. In 50 plots of a tree-diversity oriented research platform in mature forests in northern Belgium (TREEWEB), we installed a field experiment with three treatments (potting soil, mineral soil, mineral soil + forest floor), in which we sowed seeds of each species. We monitored early establishment and survival, height, root and shoot biomass of the seedlings after two growing seasons. Mineral soil negatively affected seedling establishment and performance relative to the potting soil. The negative soil effects did not vary with measured abiotic soil properties. In general, the forest floor did not deteriorate or mitigate the soil effects, and only for root biomass did the forest floor partly compensate the negative soil effects. Forest floor effects did not vary with the measured forest floor properties. In the studied forests, creating bare soil was not enough to promote regeneration; improving soil properties might be important for the success of natural regeneration. [ABSTRACT FROM AUTHOR]

[Display omitted] Plant recruitment is limited by seed predation. However, seeds that are only partially consumed can still contribute to regeneration provided the embryo remains viable. Seed size and shape are important traits that influence the relative location of the embryo, as well as its survival and further development. Yet, it is unclear whether the interaction of seed size and shape affects seed tolerance to partial damage and initial seedling performance. We evaluated the effects of simulated partial damage in three different acorn shapes (flattened, triangular and typical) on early seedling establishment in the threatened Quercus insignis , the largest-seeded oak species worldwide. We also distinguished between lateral acorn damage (pericarp damage only) and cotyledon damage (1/3 of the reserves), using acorn size as a covariate. For this, we recorded the germination, emergence and performance (total height, basal diameter, specific leaf area, total leaf area, above and belowground dry biomass) of each seedling after 110 days of growth. Seed shape influenced the rate and percentage of acorn germination, seedling emergence and performance. Typical-shaped acorns germinated at higher rates and produced more seedlings with higher performance. Simulated damage increased the rate and percentages of germination and emergence, but did not affect performance (except for specific leaf area). Seed size favored performance but not germination or emergence, and no significant interaction was found between acorn shape and seed size with respect to germination, emergence or performance, depending on each damage treatment. Our results suggest that acorn size allows tolerance to partial seed predation, since low to moderate acorn damage (<1/3 of cotyledon lost) had no negative effect on germination or emergence. Larger seed size could therefore not only support seedling performance, but also help to meet the nutritional requirements of small and mid-size predators without risking the integrity or development of the embryo. Acorn shape should therefore be considered in basic and applied oak ecology since seed morphology seems to influence not only germination and emergence, but also seedling performance. These results may have important eco-evolutionary implications in the context of seed-predator interactions, since certain shapes tolerate damage better than others and may thus benefit from the selection pressures exerted by seed foragers, both predators and dispersers. In addition to acorn size, managers should consider acorn shape and its relationship to early seedling establishment, as well as the potential for using partially damaged acorns in oak forest restoration projects. [ABSTRACT FROM AUTHOR]

Summary: Success of establishing native trees in cool temperate environments depends on the ability of seedlings to withstand subzero temperatures and recurrent frosts. This study compared the survival and growth of five tree and shrub species with two guard types at three landscape positions in an upland pasture. Seedlings were planted between December 2013 and March 2014. Half of the seedlings were planted in tall Corflute® guards (60 cm high), and the remaining seedlings were interplanted in milk cartons (30 cm). Seedling survival and height were measured in November 2014. Hourly temperature readings were recorded between March and November 2014. Seedling height for all species was greater in tall guards than milk cartons at all landscape positions, possibly at least partly due to etiolation. However, seedlings in tall guards survived better than seedlings in milk cartons at mid‐ and upper‐slope positions. Higher temperatures may have benefited seedling performance by prolonging the growing season as average maximum temperature was significantly higher inside tall guards than milk cartons and ambient conditions at all landscape positions. Average daily temperature was significantly higher in tall guards compared to milk cartons and ambient conditions at the upper‐slope site only. There were no significant differences in average minimum temperature between guard types at all landscape positions. [ABSTRACT FROM AUTHOR]

Ricinus communis is becoming an important crop for oil production, and studying the physiological and biochemical aspects of seedling development may aid in the improvement of crop quality and yield. The objective of this study was to assess the effect of temperature on biomass allocation in two R. communis genotypes. Biomass allocation was assessed by measuring dry weight of roots, stems, and cotyledons of seedlings grown at three different temperatures. Root length of each seedling was measured. Biomass allocation was strongly affected by temperature. Seedlings grown at 25 °C and 35 °C showed greater biomass than seedlings grown at 20 °C. Cotyledon and stem dry weight increased for both genotypes with increasing temperature, whereas root biomass allocation showed a genotype-dependent behavior. Genotype MPA11 showed a continuous increase in root dry weight with increasing temperature, while genotype IAC80 was not able to sustain further root growth at higher temperatures. Based on metabolite and gene expression profiles, genotype MPA11 increases its level of osmoprotectant molecules and transcripts of genes encoding for antioxidant enzymes and heat shock proteins to a higher extent than genotype IAC80. This might be causal for the ability to maintain homeostasis and support root growth at elevated temperatures in genotype MPA11. [ABSTRACT FROM AUTHOR]

Cultivation of important woody species with the goal of conserving them is hampered by little, or no, information on how such species can be propagated or their seedlings established. We investigated propagation and seedling establishment of 14 important multipurpose species much valued for traditional medicine in Uganda. The experiments included sexual and vegetative propagation, as well as a seedling growth experiment. The multipurpose speciesPsidium guajava, Markamia lutea, Maesopsis eminiiandSpathodea campanulatapropagated easily from seed, andFicus natalensisfrom cuttings. The medicinal speciesZanthoxylum leprieurii, Warburgia ugandensisandFicus saussureanadid not germinate at all.Toddalia asiaticaandCanarium schweinfurthiihad high dormancy and low synchrony of seed emergence.Markamia luteaseedlings established readily with addition of fertilizer (NPK) and moderate watering (three times a week). We conclude that whereas the multipurpose use species appear to propagate easily, the medicinal plants are difficult to propagate sexually or asexually. [ABSTRACT FROM AUTHOR]

Recent studies have provided evidence that trade-offs in biomass allocation, resource-use efficiency, and anti-herbivore defense influence seedling performance and distribution across soil types. Our previous research suggested that soil nutrient availability acted as a filter for understory palm community assembly and species coexistence in a lower montane forest in western Panama. Here, we experimentally tested three potential mechanisms that could be driving this filtering of palm communities along a soil nutrient gradient. We examined seedling performance of 13 understory palm taxa with differing distribution patterns transplanted to five sites, where they were both exposed to and protected from herbivores. We found the strongest evidence for habitat filtering at the lowest-nutrient site, where seedlings of locally occurring species had significant performance advantages over those of locally absent species, regardless of protection from herbivores. When transplanted to the lowest-nutrient site, seedlings of naturally occurring species maintained high above- to belowground biomass ratios, maximized photosynthetic nitrogen-use efficiency, and minimized leaf area loss to herbivores and pathogens. Species from low-fertility sites were therefore able to maintain higher survival and relative growth rates (RGR) at the lowest-nutrient site than species from more fertile sites. Similar patterns were found for a high-nutrient site, where naturally occurring species had higher RGR compared to species from lower-fertility sites. However, the functional traits associated with the differences in performance at high-nutrient sites were less clear, perhaps due to increased light limitation in the understory of these sites. At higher-nutrient sites, protection from herbivores significantly reduced leaf area damage and mortality rates in seedlings, particularly for naturally occurring species. Overall, morphological and physiological traits were more strongly coupled with soil nutrient availability than were leaf damage or seedling performance across the sites. Nonetheless, the coordination of all three trade-offs was related to the strongest performance advantage and, therefore, ecological filtering along the soil nutrient gradient in this lower montane forest. [ABSTRACT FROM AUTHOR]

Abstract: Enrichment planting within established plantations or secondary forests is a common strategy to enhance forest recovery, given that later successional forest species tend to have low dispersal and limited recruitment into these sites. It is difficult, however, to predict how species of seedlings will perform when planted under different overstory species. The field of phylogenetic ecology offers tools to help guide the selection of seedlings, drawing on the evolutionary conservatism of important functional traits. We evaluated the survival, growth, foliar disease, and herbivory of various native tropical tree seedlings at different evolutionary distances from monospecific stands of trees beneath which they were planted. We expected that seedlings planted under conspecific overstory trees would have low survival and growth and high percent foliar damage (as predicted by the Janzen–Connell Hypothesis), and that seedling performance would improve steadily with phylogenetic distance between seedling and overstory species. We found that seedlings planted under conspecific canopies had lower survivorship, reduced growth, and greater foliar damage than seedlings planted under canopies of different tree species. An overall increase in seedling performance with greater phylogenetic distance between seedling and overstory species was dominated by the contrast in performance between conspecific pairs and seedlings planted beneath extra-familial overstory species; but lack of available congeneric pairing limited inference about interactions among close relatives. Most pathogenic fungi isolated from enrichment-planted seedlings also caused disease when inoculated on the overstory tree species where the seedlings had been planted; this is consistent with overstory trees being an important reservoir of pathogens that affect seedlings. We conclude that enrichment planting with species more distantly related to those that dominate the canopy should enhance seedling’s performance. Closer analysis at the congeneric level is warranted because of expected strong biotic interactions at close phylogenetic distances. [Copyright &y& Elsevier]

Intraspecific variation in seed size may result from life-history constraints or environmental conditions experienced. This variation in seed size is likely to affect the early stage of invasion as seed size may contribute to the success or failure of population establishment. However, only a few studies have examined seed size variability and its causes and consequences for invaders so far. Using the invasive herb Lupinus polyphyllus, we estimated seed mass variation within and among 39 populations from two different geographic regions in a part of the invaded range. We empirically and experimentally evaluated the effect of seed number and environmental conditions (e.g. geographic region, habitat type, intraspecific competition) on seed mass, emergence and seedling performance. Seed mass varied threefold, being largest among individual plants within populations and smallest among populations. Variation in seed mass was neither related to seed number nor the environmental conditions examined, but led to differences in offspring performance, with emergence and seedling size increasing with seed mass. Larger L. polyphyllus seeds were better establishers than smaller seeds regardless of environmental conditions, indicating that the success of L. polyphyllus invasions is likely to depend positively on seed mass. Our results suggest that some plant species such as the invasive L. polyphyllus may not show an adaptive response in seed mass to resources or environmental conditions, which may partly explain their ability to colonise a range of different habitats. [ABSTRACT FROM AUTHOR]

Fig (Ficus spp.) trees have been promoted as frame-work species for tropical forest restoration throughout Asia, because they are considered to be keystone species. This article presents optimal propagation and planting techniques for six Asian dioecious Ficus species, which will enable their inclusion in forest restoration plantings across the Asia-Pacific region: Ficus auriculata, F. fulva, F. hispida, F. oligodon, F. semicordata, and F. varie-gata. Nursery experiments compared the growth perfor-mance of propagating planting stock from seed and from leafy cuttings, whereas field experiments assessed the cost-effectiveness and the relative performance of (1) direct seeding, (2) planting stock from seed, and (3) planting stock from cuttings. The most efficient method of produc-ing Ficus spp. was from seed. Propagation from cuttings was much less successful. Seedlings produced from seed had the highest rates of growth and survival both in the nursery and in field trials. In field trials, use of planting stock from seed was also more cost-effective than direct seeding and vegetative propagation. Establishment costs calculated on the basis of "per plant established" were $1.14 for seed, $6.95 for cutting, and $25.88 for direct seeding. [ABSTRACT FROM AUTHOR]

Question Is there evidence of a trade-off between drought and shade tolerance in coastal desert shrubs? Location Arid scrubland, Atacama desert, north-central Chile. Methods One-week-old seedlings of six coastal desert shrub species ( Centaurea chilensis, Encelia canescens, Flourensia thurifera, Pleocarphus revolutus, Senna cumingii and Haplopappus parvifolius) were planted in the field under six treatment combinations: three light environments (low, intermediate and high radiation) and two water levels (natural rainfall (55.4 mm) and natural rainfall plus 100 mm irrigation). We quantified seedling survival for each species during 22 weeks, estimated relative growth rate, and examined how light and water affect whole-plant responses, particularly specific leaf area, leaf mass ratio and root-shoot ratio. Results We found species-specific differences in the temporal pattern of mortality. Water and/or light levels affected seedling survival of all species, excluding C. chilensis. Relative growth rate ( RGR) increased in low-light conditions in C. chilensis and P. revolutus, but otherwise did not vary in response to differences in either light or water, independently or to their interaction. Across species, the effect of water on specific leaf area ( SLA) was inconsistent, increasing both in drought conditions ( C. chilensis) and in treatments with supplemental water ( S. cumingii). Additionally, SLA tended to increase with decreasing light levels for most species ( F. thurifera, H. parvifolius, C. chilensis). In our study, only F. thrurifera and C. chilensis showed changes in leaf mass ratio ( LMR) and only with respect to light levels; specifically, LMR tended to increase with decreasing light level. Biomass allocation was independent of light and water for all species except F. thurifera, which showed an increase in root biomass in drought conditions. Conclusions Overall, we did not find evidence to support a trade-off between drought and shade tolerance during early plant establishment. Our results suggest that water is the most important resource that limits recruitment in the coastal desert. Therefore, increased aridity in this system is likely to severely hinder seedling recruitment of the native coastal desert shrubs. [ABSTRACT FROM AUTHOR]

Dipterocarps are one of the most important tree families in the lowland forests of Southeast Asia and are somewhat unusual among tropical trees in that they form ectomycorrhizal ( Ec M) symbiotic root-inhabiting fungal associations. It has been hypothesized that dipterocarps have been partnered in this mutualistic association prior to the separation of Gondwana. Under many conditions Ec Ms form rapidly on dipterocarp seedlings through inocula present in the soil, although few studies have been conducted to provide evidence that they improve seedling establishment and performance. There are hundreds of Ec M species associated with dipterocarps. Fungal fruit body surveys suggest that the most important families are Amanitaceae, Boletaceae, and Russulaceae, although Thelephoraceae also become numerically important when root tips are examined. Ec M communities are affected by various biotic and abiotic factors, as well as anthropogenic perturbations, and the importance of these in structuring Ec M communities is examined herein. [ABSTRACT FROM AUTHOR]

This study examines the ecological niche of American chestnut ( Castanea dentata (Marsh.) Borkh) and the latest blight resistant American chestnut × Chinese chestnut ( Castanea mollissima Blume) hybrids. Planted seedlings of chestnut, tulip poplar ( Liriodendron tulipifera L.) and chestnut oak ( Quercus prinus L.) were subjected to two levels of light and two soil types in parallel field and greenhouse studies. The field study took place in the Appalachian ridge and valley province of Virginia. Growth and survival were quantified after three growing seasons. The interaction between light levels and topographic position (soil type) was significant for growth rates in the field and greenhouse. Species were significantly different from each other although hybrid varieties were not significantly different from each other or from pure American chestnut. Tulip poplar showed the greatest growth rates under all treatments in the field. Both tulip poplar and chestnut had the greatest growth rates in large gaps within mesic, mid and lower slope (MML) sites in the field. In contrast to growth, optimal conditions for survival differed among species. Tulip poplar had the greatest survival (71%) within large gaps in MML sites while chestnuts and oaks had the greatest overall survival (64%) in small gaps within xeric, upper slope and ridge (XUR) sites. In the greenhouse, tulip poplar did not outperform chestnut. Discrepancies in field and greenhouse studies were accounted for by uncontrolled factors, such as rodent predation. We conclude that optimal sites for planting American chestnut hybrids are in small gaps located within XUR sites. [ABSTRACT FROM AUTHOR]

The rainforest of Mexico has been degraded and severely fragmented, and urgently require restoration. However, the practice of restoration has been limited by the lack of species-specific data on survival and growth responses to local environmental variation. This study explores the differential performance of 14 wet tropical early-, mid- or late-successional tree species that were grown in two abandoned pastures with contrasting land-use histories. After 18 months, seedling survival and growth of at least 7 of the 14 tree species studied were significantly higher in the site with a much longer history of land use (site 2). Saplings of the three early-successional species showed exceptional growth rates. However, differences in performance were noted in relation to the differential soil properties between the experimental sites. Mid-successional species generally showed slow growth rates but high seedling survival, whereas late-successional species exhibited poor seedling survival at both the study sites. Stepwise linear regressions revealed that the species integrated response index combining survivorship and growth measurements, was influenced mostly by differences in soil pH between the two abandoned pastures. Our results suggest that local environmental variation among abandoned pastures of contrasting land-use histories influences sapling survival and growth. Furthermore, the similarity of responses among species with the same successional status allowed us to make some preliminary site and species-specific silvicultural recommendations. Future field experiments should extend the number of species and the range of environmental conditions to identify site 'generalists' or more narrowly adapted species, that we would call 'sensitive.' [ABSTRACT FROM AUTHOR]

Abstract: Unsuccessful colonization by indigenous tree species into established plantations has retarded the succession of artificial plantations to more natural, secondary forests in South China. To understand how to improve colonization by seedlings of indigenous species, we determined how performance of indigenous seedlings is affected by seedling species (the shade-intolerant Castanopsis chinensis, the moderately shade-intolerant Michelia chapensis, and the shade-tolerant Psychotria rubra), the site into which the seedlings were transplanted (a mixed-legume plantation, a eucalyptus plantation, a mixed-native plantation, a mixed-conifer plantation, and a shrubland), and site preparation (removal or retention of understory vegetation and litter). Seedling survival and growth were generally increased by removal of understory vegetation and litter. C. chinensis and M. chapensis grew better in the mixed-legume and mixed-conifer plantations, while P. rubra grew better in mixed-native and mixed-conifer plantations. Responses of the transplanted seedlings to environmental factors were species specific. The effects of light on seedling survival and growth were correlated with the shade tolerance of the species. Soil moisture was important; it was positively correlated with survival but negatively correlated with growth of C. chinensis seedlings. Growth of C. chinensis and M. chapensis was positively correlated with soil potassium, while growth of P. rubra was positively correlated with soil organic matter but negatively correlated with soil hydrolyzed nitrogen. These findings suggest that we should select suitable native species under the different plantations before improvement of plantations. Light and soil moisture are most important environmental factors for the selection of species specific. Site preparation and fertilizer are needed during the improvement of those plantations. [Copyright &y& Elsevier]

1. Allelopathic interactions between invasive and native species have been suggested to be an important mechanism for the success of some of the most aggressive plant invaders. However, field experiments that test the effects of natural levels of allelopathic compounds on coexisting native species are exceptionally rare. 2. In this study, we analyzed the allelopathic effects of the invasive tree Ailanthus altissima on seedling emergence, survival and growth of three native tree species ( Acer rubrum, A. saccharum and Quercus rubra) in temperate forests of the northeastern United States. We used activated carbon (AC) to reduce potential allelopathic interference, and developed neighbourhood models that explain the observed spatial variation in the effects of the AC treatments on seedling performance as a function of the size, abundance and distribution of Ailanthus trees in the neighbourhood. 3. Our results showed that the addition of AC to the soil did not affect seedling emergence or survival, but caused a significant increase in seedling growth of all three species. Moreover, the AC shifted the overall interaction between Ailanthus and maple seedlings from neutral or slightly positive to very positive for A. rubrum, and from negative to positive for A. saccharum, whereas the net interaction between Ailanthus and Q. rubra was always negative. As Ailanthus has the ability to increase soil fertility, these species-specific responses are presumably influenced by among-species differences in the net effects of both allelopathy and changes in resource availability caused by the presence of Ailanthus. 4. The cumulative allelopathic effects of Ailanthus were proportional to the density of Ailanthus in the neighbourhood, regardless of their size. In contrast, Ailanthus effects were strongly influenced by distance from a tree, generally dropping to zero within 5 m from the trunk. 5. Synthesis. Taken together, our results indicate that allelopathy is an important mechanism to take into account when trying to understand the causes and consequences of plant invasions. However, this study also strongly suggests that the real significance of the allelopathic effects of an invasive species cannot be assessed independently of its target community, or in isolation of other resource interactions involving the invader and the native community. [ABSTRACT FROM AUTHOR]

The effects of morphological characteristics on seedling performance were studied in Cedrus libani seedlings at 3 locations in the Central Anatolia region of Turkey. Some 2+0 seedlings were morphologically graded according to height and root collar diameter sizes. The seedlings were divided into 5 height categories and each height category was divided into small and large root collar diameter subcategories. The morphologically graded seedlings were planted at 3 locations. After 5 growing seasons, the mean survival of the seedlings planted in Ankara, Eskisehir and Konya locations was 84.4%, 77.9% and 54.7%, respectively. The mean height of seedlings planted in Ankara, Eskisehir and Konya was 78.5, 51.8 and 48.7 cm, respectively. Survival and height growth of graded seedlings showed significant differences among the locations, which might be a reflection of differences in climatic and physiographic conditions among the locations. The initial height and root collar diameter of seedlings had no effect on survival. Only root collar diameter had a significant effect on height growth. Initial height differences among different sized stocks were still significant after 5 years, but had not expanded. Our results suggest that initial seedling morphology is not a good predictor of field survival but root collar diameter is a good indicator of the growth potential of C. libani seedlings after planting. This study indicated that the physiological characteristics of seedlings have a strong influence on seedling survival potential. [ABSTRACT FROM AUTHOR]

Seedling growth and morphology of the deciduous tree Cornus controversa from subtropical China were studied in four simulated forest gap light environments: 100%. 55%, 33% and 18% full sunlight. The best performance was in 33% full sunlight. Overall, Cornus seedlings grew taller than those of five broad-leaved evergreen species from the same area. In terms of total plant mass only Cinnamomum camphora seedlings grew bigger than Cornus seedlings. Cornus seedlings needed relatively small biomass investments to become tall and to produce a great total length of axes. Growth of Cornus seedlings was probably enhanced by their comparatively `cheap' leaves in terms of weight per area, which resulted in large total leaf area per unit plant weight. The results provide ecophysiological support of Cornus' competitive strength in forest gaps amidst mostly evergreens. [ABSTRACT FROM AUTHOR]

The article presents a study to examine the growth and survival of riparian plantings in relation to Weeping Willow (Salix babylonica) canopy cover in order to assess their suitability for revegetation and the role of canopy cover in seedling establishment at the Upper Hunter River, New South Wales. Five species of plants were used in the experiment such as the Red Cedar (Toona ciliata), White Cedar (Melia azedarach), Kangaroo Apple (Solanum aviculare), Tree Violet (Melicytus dentatus) and Tuckeroo (Myrsine bowittiana). Details on how the study was done is offered. Results showed that those seedlings planted under a Weeping Willow canopy generally performed better than those planted in open sites, but not true for all species.