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In gynodioecious plants, females are predicted to produce more and/or better offspring than hermaphrodites in order to be maintained in the same population. In the field, the roots of both sexes are usually colonized by arbuscular mycorrhizal ( AM) fungi. Transgenerational effects of mycorrhizal symbiosis are largely unknown, although theoretically expected., We examined the maternal and paternal effects of AM fungal symbiosis and host sex on seed production and posterior seedling performance in Geranium sylvaticum, a gynodioecious plant. We hand-pollinated cloned females and hermaphrodites in symbiosis with AM fungi or in nonmycorrhizal conditions and measured seed number and mass, and seedling survival and growth in a glasshouse experiment., Females produced more seeds than hermaphrodites, but the seeds did not germinate, survive or grow better. Mycorrhizal plants were larger, but did not produce more seeds than nonmycorrhizal plants. Transgenerational parental effects of AM fungi were verified in seedling performance., This is the first study to show transgenerational mycorrhiza-mediated parental effects in a gynodioecious species. Mycorrhizal symbiosis affects plant fitness mainly through female functions with enduring effects on the next generation. [ABSTRACT FROM AUTHOR]

Experimental forest plantations to study biodiversity-ecosystem functioning (BEF) relationships have recently been established in different regions of the world, but subtropical biomes have not been covered so far. Here, we report about the initial survivorship of 26 tree species in the first such experiment in subtropical China. In the context of the joint Sino-German-Swiss Research Unit 'BEF-China,' 271 experimental forest plots were established using 24 naturally occurring tree species and two native commercial conifers. Based on the survival inventories carried out in November 2009 and June 2010, the overall survival rate was 87 % after the first 14 months. Generalized mixed-effects models showed that survival rates of seedlings were significantly affected by species richness, the species' leaf habit (deciduous or evergreen), species identity, planting date, and altitude. In the first survey, seedling establishment success decreased with increasing richness levels, a tendency that disappeared in the second survey after replanting. Though evergreen species performed less well than deciduous species with establishment rates of 84 versus 93 % in the second survey, their planting success exceeded the general expectation for subtropical broad-leaved evergreen species. These results have important implications for establishing mixed-species plantations for diversity conservation and improvement of ecosystem functioning in the Chinese subtropics and elsewhere. Additional costs associated with mixed-species plantations as compared to conventional plantations also demonstrate the potential of upscaling BEF experiments to large-scale afforestation projects. [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]

Pinus pinea L. is a coniferous tree inhabiting the Mediterranean Basin, which appears widely distributed in the Iberian Peninsula, frequently associated to Mediterranean shrub species, such as Cistus salvifolius L., C. libanotis L. and Halimium halimifolium (L.) Willk. (Cistaceae). This study investigated the effects (chemical and physical) of P. pinea needles on the seed germination and early growth of these three shrub species. Laboratory experiments were carried out in order to assess an expected negative effect by using different treatments to seeds (physical layer and two aqueous extracts concentrations). Seed germination of all species was inhibited when treated with aqueous extracts and the degree of inhibition was higher when using the extract with the highest concentration, while no effect was observed with the physical layer treatment. Seedling performance was also sensitive to the different treatments, showing the most stressed values with the high concentration extract. The results from this study highlight the importance of allelopathy of P. pinea needles as a mechanism for controlling seed germination and seedling performance of some Mediterranean shrub species. [ABSTRACT FROM AUTHOR]

Introduction: The great spatial and temporal heterogeneity of Mediterranean ecosystems can influence establishment success in woody species, whose natural regeneration occurs to a very small extent. In this work, the effect of the spatial pattern of environmental variables (light availability, soil moisture and herbaceous production) on seedling emergence, growth, survival and establishment success was examined by using a spatially explicit approach. Methods: Seeds of four Quercus species differing in leaf longevity ( Quercus ilex, Quercus suber, Quercus faginea and Quercus pyrenaica) were sown in two plots located in a holm oak forest (southern Spain). The spatial pattern of the studied variables was examined by Spatial Analysis by Distance Indices. Results: All environmental variables exhibited an aggregated spatial pattern. There was no clear spatial association between the environmental variables and emergence and survival. Only soil moisture during the dry season was spatially associated with the establishment success of all the species. Species also differed in survival and establishment success, with evergreens having higher percentages than deciduous. No aggregated spatial pattern for growth and morphological traits was apparent, these being more dependent on seed mass than on environmental factors. Identifying which microsites facilitate regeneration may provide useful hints with a view in focusing restoration endeavours on microenvironments with high survival percentage. [ABSTRACT FROM AUTHOR]

Framework species are indigenous tree species planted in a mixed stand to accelerate natural regeneration of forest and encourage biodiversity regeneration. In this study we used the framework species method to make multipurpose tree gardens to provide traditional healers with woody species used for medicine and other needs like food and firewood. We specifically determined the phenology, germination behaviour, survival and growth after planting 19 indigenous and 8 introduced woody species. The species were planted in a mixed stand together at a density of 3125 ha. Field performance was assessed by monitoring survival, height and crown width once every month for 13 months after planting. Eleven species ( Artocarpus heterophyllus, Calliandra calothyrsus, Callistemon citrinus, Carica papaya, Carissa spinarum, Leucaena leucocephala, Markhamia lutea, Sarcocephalus latifolius, Senna siamea, S. spectabilis and Terminalia schimperiana) proved to be excellent framework species. Eight species qualified as 'acceptable' FWS ( Albizia coriaria, Ceiba pentranta, Entada abyssinica, Erythrina abyssinica, Eugenia jambos, Ficus sycomorus, Maesopsis eminii and Milicia excelsa), while seven species were ranked as 'marginally acceptable' ( Acacia macrothyrsa, Calpurnia aurea, Canarium schweinfurthii, Capparis tomentosa, Ficus natalensis, Senna sp. and Warburgia salutaris) . Annona squamosa was the only species rejected since both germination and survival was low. Trees with good reforestation traits could be recommended for planting while the species that were marginally acceptable or rejected require extra research since some of them are important medicinal woody species of conservation concern. [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]

This research was carried out in a degraded pasture at Selva Lacandona tropical rain forest in Chiapas, Mexico. During a whole year weeding and fertilization effects were assessed on the seedling performance of six native tree species measuring survival and growth. From the dry season onwards the survival probability of the seedlings rise under grass covering (without weeding treatment) both for light demanding and shadow tolerating species. Helophytic seedlings, Ceiba pentandra, Schizolobium parahyba and Swietenia macrophylla had higher levels of survival and growth than shadow tolerating species, Brosimum alicastrum, Calophyllum brasiliense and Ormosia schippii. Relative growth rate (TRC) in height and diameter changed significantly for the simple effect of weeding and for the species itself. The simple effect of weeding indicated a higher growth on height and diameter of the plants under weeding treatment. We did not observe any significant effects of the fertilization on plants performance. The effect of the species was the most consistent factor in explaining variances in the three response variables, meaning that the tree species under investigation had specific survival and growth trajectories which lie aside the effect of the treatments. [ABSTRACT FROM AUTHOR]

We investigated how seed size and timing of emergence interact with environmental conditions to determine seedling performance in one population of the long-lived perennial shrub Ericameria nauseosa var. oreophila (Asteraceae) in the sand dune ecosystem near Mono Lake, California. Size of seeds varied significantly among and within individual plants, and this variation had important consequences for size, growth, and survival of seedlings in both greenhouse and field experiments. Larger-seeded seedlings had greater biomass, greater percentage of total plant biomass allocated to roots, and longer taproots than seedlings from smaller seeds. Seedlings grown in native soil had less total biomass than seedlings grown in augmented soil but greater allocation of biomass to roots. In a field experiment following individually weighed seeds, seedlings emerging from larger seeds germinated and emerged earlier and at a higher rate than did smaller-seeded seedlings. Larger-seeded seedlings were larger at emergence, remained larger through time, and lived longer than smaller-seeded seedlings. In all stages of early seedling establishment, from germination through the first summer drought, and by all criteria, larger-seeded seedlings performed better than smaller-seeded seedlings. Given the considerable longevity of adults and the extremely small size of the wind-dispersed seeds, these aspects of seed and seedling performance have a remarkably significant impact on the survival and reproduction of subsequent life stages of E. nauseosa at this site. [ABSTRACT FROM AUTHOR]

Abstract: The Mediterranean region emerges highly heterogeneous at every spatio-temporal scale. Key species shape a mosaic of patches (landscape units) composed of different microhabitats. Within these ecosystems irradiance appears as one of the most changing factors affecting communities’ dynamic. However, the impact of irradiance on the species performance is still poorly known. In this study, we intended to explore whether irradiance heterogeneity influences early recruitment. We chose a patchy Mediterranean site. During 2001, 2002 and 2003 we marked naturally Quercus ilex emerged seedlings. We distinguished three landscape units (Q. ilex woodlands, shrublands and afforestations) and six microhabitats (oak, broom, tall shrub, subshrub, pine and open). For each seedling, we measured (1) irradiance as global site factor (GSF); (2) acorn presence; (3) acorn depth; (4) burial layer; (5) distance to the nearest co-specific adult. As estimates of seedling performance, we measured seedling survival and height. Estimates of seedling performance were higher in 2001 and 2002 than in 2003. Oak or pine microhabitats achieved higher survival rates than brooms or open areas whilst under oaks, brooms or in open areas seedling height was lower than under tall shrubs. Irradiance significantly affected seedling survival and growth. The lower the irradiance, the higher the survival. Maximal growth was found at intermediate irradiance, indicating that, in this system, moderate shade is crucial for Q. ilex seedling recruitment. Some microhabitats provide intermediate irradiance that combines positive effects on survival and growth. As a final point, dispersers’ activity creates a heterogeneous distribution of acorn deposition filtering out part of the total irradiance present in the study site. [Copyright &y& Elsevier]

Feeding by the tarnished plant bug ( Lygus rugulipennis Popp.) has caused severe damage in Norwegian nurseries. Large quantities of seedlings have been removed after sorting. The life cycle of the insect has been well studied and documented. This study was a first attempt to investigate how the seedlings develop after the insect attacks. The first visible sign of damage is the development of multiple terminal buds. Two-year-old containerized seedlings were planted and followed for 4 years. Before planting, the seedlings were sorted into three damage classes: 0, undamaged; I, moderately damaged, up to 10 fully developed buds; and II, severely damaged, 10–20 small buds and no dominant apical bud. The damaged seedlings were somewhat shorter at planting but this difference disappeared with time. The seedlings in the two damage classes differed in their development of multiple shoots. At the end of the 4 year period about 50% of the seedlings in class  II and about 20% from class I still had multiple leaders, or lateral stems or side branches that would probably produce spike knots in the future. The sorting routine currently used at the nursery was found to reduce the problem to an acceptable level for seedlings that were planted in the forest. [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]

Abstract: Mountain birch, Betula pubescens subsp. czerepanovii (Orlova) Hämet-Ahti, is one of the very few woody plants surviving in the heavily polluted industrial barrens of the Kola Peninsula, north-western Russia. The present study was designed to find out whether long-lasting pollution impact caused selection of resistant birch genotypes, and to investigate possible trade-offs between pollution resistance and performance by exploring growth of birch seedlings in the different environments. In the reciprocal planting experiments, progenies of birches from polluted sites performed slightly better in the polluted environment (in terms of survival, leaf number, and leaf size) than progenies of birches from clean sites; and vice versa, in the clean environment progenies of birches from polluted sites performed slightly worse than progenies of birches from clean sites. However, this pattern was detected only in some of statistical tests, while the majority of comparisons showed no genotype or genotype by environment effects. Although some of the results indicate that long-lasting pollution impact may have increased pollution resistance of the affected populations by elimination of sensitive genotypes (survival selection), this conclusion should be considered tentative. The resistance did not reach the level sufficient to assure re-colonisation of polluted habitats: progenies of all trees completely died on the contaminated soils by the end of the first growth season. Therefore persistence of mountain birch populations near the strong polluters may be transient, being explained not only by higher resistance of the survivors, but also by phenotypic acclimatisation of mature trees to gradual increase in pollution. [Copyright &y& Elsevier]

The montane rain forest in Chiapas, Mexico has been subject to continuous human disturbance, mainly by wood extraction, cattle grazing and fire. To address the effect of this kind of disturbance regime on regeneration, survival and growth of naturally established tree seedlings were evaluated during a 3-yr period in three forest stands which varied in frequency and intensity of human disturbance. Frequency of cattle browsing on transplanted seedlings of Cornus disciflora, Liquidambar styraciflua and Oreopanax xalapensis planted on different facing slopes was evaluated over an 18-mo period, their survival and growth was also determined. The density of seedlings, number of species and survival of naturally recruited tree seedlings decreased with increased intensity of disturbance. Only seedlings of Pinus and Quercus species were recorded in heavily disturbed conditions. Seedlings grew more vigorously under moderately disturbed than in undisturbed or heavily disturbed conditions. More extreme microclimatic variation (air temperature, relative humidity and solar radiation) was recorded in heavily vs moderately disturbed forest. Survival and growth of transplanted tree seedlings differed with species. Grazing damage varied among seedlings located on different facing slopes. Plants located on NE facing slopes survived better than those on other slope positions. The mean proportion of surviving individuals of L. styraciflua (80%) and C. disciflora (78%) was higher than those for O. xalapensis (60%). A higher number of C. disciflora and O. xalapensis seedlings were grazed than L. styraciflua in any slope orientation treatment. The results suggest that human disturbance negatively affects natural recruitment, reduces richness of tree seedlings and favours a small number of tree species. [ABSTRACT FROM AUTHOR]

Framework tree species are indigenous forest tree species, planted to complement and accelerate natural regeneration of forest ecosystems and encourage biodiversity recovery, on degraded sites. In this paper we test the extent to which 37 native forest tree species might act as framework tree species to accelerate recovery of evergreen, seasonal forest in a degraded upper watershed in Doi Suthep-Pui National Park in northern Thailand. The trees were planted at a density of 3125 ha−1 in 1998 and 1999. The plots were hand weeded, and fertiliser applied around planted trees three times during the rainy season. Field performance of planted trees was assessed at the end of the second wet season after planting by monitoring height, crown width and weed cover. A fire, which spread through some of the plots in March 2001, enabled assessment of resilience to fire for some of the species. Nine species were ranked as ‘excellent’ framework species, including Ficus hispida var. hispida, Gmelina arborea, Hovenia dulcis, Melia toosendan, Michelia baillonii, Prunus cerasoides, Rhus rhetsoides and Spondias axillaris. Fifteen species qualified as ‘acceptable’ framework species: Acrocarpus fraxinifolius, Balakata baccata, Castanopsis acuminatissima, Ficus altissima, Ficus benjamina var. benjamina, Ficus glaberrima var. glaberrima, Ficus racemosa var. racemosa, Ficus subulata var. subulata, Glochidion kerrii, Heynea trijuga, Macaranga denticulata, Machilus bombycina, Nyssa javanica, Sapindus rarak and Sarcosperma arboreum. Only four species were ranked as ‘marginal’: Bischofia javanica, Ficus heteropleura var. heteropleura, Manglietia garrettii and Quercus semiserrata. Nine species performed poorly in most respects and should probably be rejected as framework species: Aglaia lawii, Callicarpa arborea var. arborea, Cinnamomum caudatum, Diospyros glandulosa, Helicia nilagirica, Horsfieldia thorelii, Lithocarpus fenestratus, Phoebe cathia and Pterocarpus macrocarpus. [Copyright &y& Elsevier]

Effects of litter cover on insect herbivory, leaf-fungal damage, and seedling performance (survival, growth in height and leaf number), were assessed on established Nectandra ambigens seedlings in three sites of a Mexican tropical rain forest. Naturally occurring seedlings were measured for height, leaf number and standing levels of leaf damage by herbivores and pathogens. Thereafter, seedlings were exposed for 1 y to three litter treatments: (1) litter addition, (2) control and (3) continuous litter removal. There was a significant effect of site on the proportion of surviving seedlings and on the relative growth rates in terms of leaf number. Overall, seedlings with higher initial leaf number showed higher survival and produced more leaves after 12 mo than seedlings with lower initial leaf number. Litter addition resulted in seedlings with lower relative growth rates in height and higher levels of damage by herbivores and pathogens. On average, leaf area damaged by pathogens was < 6% and herbivory was < 27%. Seedlings with higher levels of herbivory showed higher levels of pathogen attack. Herbivory and pathogen attack had no effect on seedling performance. This study reveals the importance of litter-cover on the interactions between seedlings, herbivores and pathogens, as well as on the performance of tropical seedlings. [ABSTRACT FROM PUBLISHER]

Summary • Senna obtusifolia (sicklepod) is a troublesome weed in many agronomic cropping systems in the southeastern USA with varying fertility regimes. This series of experiments was initiated to determine the impact of nutrient availability on reproductive output and maternal effects. • Experiments were conducted with plants growing in soil in growth chambers for 120 d. Offspring growth was evaluated in hydroponics. • Plants grown under higher nutrient conditions had greater reproductive biomass, number of seeds and total seed biomass. Individual seed mass distributions were slightly affected, with negative skewness decreased at higher nutrition. Seed germination rates were influenced primarily by seed size, as small seeds germinated faster than large seeds. The nitrogen content of seeds increased with increasing seed size and was higher in the high nutrition treatment. Seedlings arising from maternal plants grown under high nutrition grew more rapidly than did seedlings arising from maternal plants grown in a low nutrient regime. • The results suggest that S. obtusifolia reproduction and offspring competitiveness can be strongly influenced by the fertilization regimes used in different agronomic crops and rotations. [ABSTRACT FROM AUTHOR]

The seed is the fundamental unit of the dispersal of dry, dehiscent fruits, in which the fruit splits open at maturity to allow for seed dispersal. However, dry fruits may be indehiscent and therefore represent the dispersal unit (DU). Cereals possess a one-seeded fruit, whereby the seed coat and the fruit coat are fused together to generate the caryopsis. This caryopsis may be covered by floral bracts to generate two types of DUs, namely florets, whereby the caryopsis is enclosed by the lemma and the palea (e.g., Avenasterilis) or spikelet, whereby the floret(s) is further covered by the glumes (Triticum turgidum var. dicoccoides). Here, we highlight the dead coverings enclosing the caryopsis in cereals, namely the husks as an integral component of the dispersal unit that play multifaceted roles in grain biology. Thus, besides protection and dispersal means, the husks function as a rich maternal supply of proteins and metabolites for enhancing growth and development, combat potential pathogens as well as confer tolerance to abiotic stresses. These attributes might have broad implications for crop performance, plant population dynamics and diversity in ecological systems, and for conservation of genetic resources in seed banks. [ABSTRACT FROM AUTHOR]

We studied seed germination and the growth and survivorship of seedlings of females and hermaphrodites of Pachycereus pringlei (cardon), a Mexican columnar cactus whose geographically variable breeding system includes trioecy and gynodioecy. Results of a two-year field experiment conducted near Bahia Kino, Sonora, Mexico and a ten-month laboratory experiment were similar and did not support the hypothesis that seedlings of females outperform those of hermaphrodites. In the field, percent seed germination and 2-yr seedling survivorship averaged 66% and 95%, respectively and did not differ among six treatment classes. Seedlings of hermaphrodites generally were larger than those of females at the end of both experiments. Selfed seedlings of hermaphrodites did not grow more slowly than outcrossed seedlings of hermaphrodites or females. Hermaphrodite seedlings performed best when pollinated with hermaphrodite pollen; female seedlings performed best with male pollen. We conclude that superior seedling performance cannot explain why females are able to coexist with hermaphrodites in populations of this cactus. Instead, we postulate that greater annual seed production, which averaged 1.6 times higher in females than in hermaphrodites in two years, may be sufficient to allow females to co-occur with hermaphrodites in this large, longlived plant, especially if sex determination involves cytoplasmic-nuclear inheritance. [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]

• We explored the effects of climate change and P. cinnamomi on coexisting tree species. • Warming and drought did not influence P. cinnamomi infectivity and pathogenicity. • Q. canariensis had slightly higher tolerance to P. cinnamomi than the other species. • Q. suber vulnerability to P. cinnamomi was similar in monocultures than in mixtures. • Climate change and P. cinnamomi had interactive effects on Quercus root traits. The structure and function of Mediterranean mixed oak forests are seriously threatened by climate change and the exotic pathogen Phytophthora cinnamomi. Both factors have been individually studied in some detail, but we have a poor understanding of their interactive effects on plant performance and species coexistence. We conducted a greenhouse experiment where seedlings of three coexisting species with contrasting susceptibility to the pathogen (Q uercus suber, Quercus canariensis and Olea europaea var. sylvestris) were planted in pairs under different scenarios of drought (control vs. 30% rainfall reduction), warming (control vs. 3°C increase) and pathogen presence (control vs. soil infested with P. cinnamomi). At the end of the experiment, we assessed the severity of root symptoms and plant morphological traits (shoot and root biomass, root tissue density and specific root length). Results showed that seedlings of the three species, including O. europaea and Q. canariensis (species considered as resistant and tolerant to the pathogen, respectively), showed in general significantly higher root symptoms and lower shoot and root biomass than non-inoculated seedlings, independently of the drought, warming and plant treatments. We found, however, some interactive effects of the climatic treatments and P. cinnamomi on root traits of the two Quercus species. Variations in the specific root length (SRL) and root tissue mass density (RTD) of Quercus spp. suggest a compensation of the negative effects of both stressors on seedling performance. Overall, our results suggest that the warming and drought predicted for Mediterranean forests during spring might not have a relevant impact on the infectivity ability of P. cinnamomi , supporting its great adaptability to these changing climatic conditions. Therefore, in Mediterranean forests infected by P. cinnamomi, it becomes crucial to avoid the spread and multiplication of the pathogen during spring, since its destructive ability at high inoculum levels is largely independent of environmental conditions. Image, graphical abstract [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.

• Rhododendron rupicola shrubs in the Hengduan mountains can modify abiotic microenvironmental conditions. • R. rupicola can increase diversity of soil associated fungi and modify their community composition. • R. rupicola facilitates growth and survival of treeline seedlings in a species-specific manner. • R. rupicola facilitates upward migration of the treeline and modifies its species composition. The alpine treeline is shifting upward due to climate warming. However, the treeline species composition and the pace of its upward migration can be mediated by ecological interactions. In particular, so-called ecosystem engineers, i.e. species that modulate the microscale environmental conditions, at the treeline may play a crucial role. We conducted a three-year seedling transplant experiment at the alpine treeline ecotone in southwest China to study how the shrub Rhododendron rupicola modifies the microscale physical and biotic environments and thus influences the establishment and performance of the two treeline species Larix potaninii and Picea likiangensis. Seedlings were transplanted to the current timberline and treeline, as well as above the current treeline in order to determine the responses of the two tree species to the shrub with respect to the current tree distribution. R. rupicola modified the microenvironment by increasing soil moisture and nutrient contents, buffering soil temperature fluctuations, and by increasing richness and changing the composition of root-associated fungi. As a result, tree seedlings planted under shrubs had significantly higher survival, growth rates and nutrient accumulations than those planted in open ground. Furthermore, seedlings planted at lower elevations performed better than those planted at higher elevations. Beyond the treeline, seedling survival was very low on open ground but strongly facilitated by the shrub. Finally, facilitation effects were species-specific, with Larix benefitting more from the shrub than Picea , while Picea had less mortality than Larix in the absence of the shrub. This study demonstrates that shrubs, through the amelioration of physical and biotic microenvironmental conditions, can act as stepping stones for the establishment of selective tree species beyond the current treeline. This suggests that biotic interactions can strongly modify the treeline species composition and push the treeline beyond its current climatic limits, thereby facilitating the upward shift with ongoing climate warming. [ABSTRACT FROM AUTHOR]

• Phytophthora cinnamomi and soil moisture affected Quercus suber performance. • The inoculum density required to cause disease increased at lower soil moisture. • An average drier climate might imply a slower advance of the disease. • On the contrary, more frequent extreme rain events might favor the disease. Climate change and exotic pests and pathogens are causing alarming forest declines worldwide. However, we still lack a comprehensive understanding of how damage caused by exotic pests and pathogens might vary under the different scenarios of water availability imposed by a changing climate, particularly in water-limited forests as those that occupy Mediterranean areas. In this paper we aimed to experimentally analyse the interactive effects of the aggressive exotic pathogen Phytophthora cinnamomi and climate change-related reductions in soil moisture on seedling performance of the Mediterranean host Quercus suber. We conducted a full-factorial greenhouse experiment where the physiology and growth of Q. suber seedlings was measured in soils with different combinations of P. cinnamomi inoculum density (0, 30, 60 and 120 colony forming units per gram of dry soil) and soil moisture (15%, 40%, 50% and 100% soil water holding capacity) simulating different invasion and climate change scenarios. We found additive effects of P. cinnamomi and drought on Q. suber performance aboveground, although these effects were not always negative. In fact, seedlings showed a compensatory physiological response to P. cinnamomi infection by increasing their net photosynthetic rates. Our results also supported important interactive effects of pathogens and soil moisture on belowground performance. Thus, the inoculum density in the soil required to cause significant root damage in experimental seedlings decreased as soil moisture increased. From a climate change perspective, these results suggest that an average drier climate might imply sub-optimal conditions for P. cinnamomi infections allowing for a slower advance of the disease in invaded areas. However, this effect will be modulated by the also predicted more frequent extreme climatic events. A higher frequency of extreme rain events that saturate the soil might be particularly beneficial for P. cinnamomi , boosting its soil density beyond any possible response capacity of susceptible hosts. [ABSTRACT FROM AUTHOR]