Early Stages Of Establishment Research Articles

Leaf C:N:P stoichiometrical and morphological traits of Haloxylon ammodendron over plantation age sequences in an oasis‐desert ecotone in North China

AbstractHaloxylon ammodendron, a typical C4 desert shrub, is widely used in vegetation reestablishment programs to stabilize shifting sand dunes and to control shifting sands encroaching into oases in the oasis‐desert ecotones in northwestern China. In this study, we investigated the morphological traits and analyzed leaf carbon (C), nitrogen (N), and phosphorus (P) stoichiometrical characteristics in an age sequence of 2‐, 5‐, 9‐, 13‐, 16‐, 31‐, and 39‐year old H. ammodendron plantations, to assess their growth development and degeneration processes. Results showed that the height, stem diameter, and canopy increased rapidly in the early establishment stage (2–9 years), and thereafter, showed a slower increase from 13 to 39 years. The leaf C and N concentrations and N:P ratio showed a rapid increase from ages 2–5, but C:N exhibited a significant decline. After 5 years, plantation leaf C, N, C:N, and N:P were stable, and leaf P and C:P showed no significant difference among all plantation ages. Leaf C and N concentrations were mainly affected by soil properties. Limiting nutrient factors in soil changed from nitrogen before 2 years to phosphorus after 5 years. The findings suggested that leaf stoichiometrical characteristics combined with morphological traits can be used to reflect the degeneration trend of H. ammodendron. Further research is needed to reveal the processes and mechanisms of H. ammodendron growth development and degeneration, and its adaption to the soil environment.

Impacts of the alien trees Ailanthus altissima (Mill.) Swingle and Robinia pseudoacacia L. on soil nutrients and microbial communities

Ailanthus altissima (Mill.) Swingle and Robinia pseudoacacia L. are two aggressive invasive trees in riparian areas in Central Spain. We aim to test whether soil properties, nutrient mineralization rates and soil bacterial communities of riparian forest dominated by the native Populus alba L. can be altered by the presence of A. altissima or R. pseudoacacia. In autumn 2011 and spring 2012 we conducted a field soil sampling in three sites where invasive and native trees were paired. In addition, in a 6-month greenhouse experiment (GHE), we grew A. altissima, R. pseudoacacia and P. alba from seeds in a soil collected from a native area. We quantified soil organic matter (OM), nitrogen (N), phosphorous (P), nitrate (NO3−–N), ammonium (NH4+–N), pH, potential net ammonification and nitrification rates, phosphomonoesterase (PME) activity and the composition of soil bacterial community in soils from the field study and from the GHE. Both the field and the GHE results showed the capability of A. altissima to decrease soil total N and of R. pseudoacacia to increase soil mineral N. In the field, all invaded soils had greater NO3−–N than P. alba soils. R. pseudoacacia field soils had greater PME activity, total N and net ammonification rates while A. altissima soils had lower OM, NH4+–N, net nitrification and total N mineralization rates than those of P. alba. Differences in the composition of soil bacterial communities were only found in the field, being more evident between A. altissima and P. alba than between R. pseudoacacia and P. alba field soils. Symbiotic N2 fixation could explain the capability of R. pseudoacacia to increase soil mineral N, while the potential of A. altissima to decrease total soil N may be attributed to changes in the balance between N input and losses from the soil. Although the GHE results indicated that the invasive trees can start changing soil conditions during early stages of establishment, more impacts found in the field study suggests that several soil properties, the composition of soil bacteria communities and microbial activities need longer time since invasion to be altered.

Sea, wind, or bird: Origin of <i>Fagus multinervis</i> (Fagaceae) inferred from chloroplast DNA sequences

울릉도의 낙엽활엽수림에 ìš°ì í•˜ê³ ìžˆëŠ” 너도밤나무를 대상으로 엽록체 반수체형(haplotype)의 다양성과 ê³µê°„ì  분포를 íŒŒì• í•˜ê¸° 위해 울릉도 ì „ì—­ì—ì„œ 채집한 총 144개체로부터 psbA-trnH 구간의 염기서열을 ê²°ì •í•˜ì˜€ë‹¤. 너도밤나무의 ê·¼ì—°ì¢ ì„ 포함하여 계통분석을 수행한 ê²°ê³¼, 너도밤나무의 엽록체 반수체형은 일본산 F. japonica와 중국산 F. engleriana 분계조와 자매관계를 이루는 것으로 나타났다. 또한, 분석한 ëª¨ë“ ë„ˆë„ë°¤ë‚˜ë¬´ì˜ 개체들은 동일한 염기서열을 ê°–ê³ ìžˆëŠ” 것으로 나타나, 엽록체 반수체형의 다양성은 매우 낮은 것으로 íŒëª ë˜ì—ˆë‹¤. 이러한 결과는 동위효소 분석에 근거한 ìœ ì „ìž 다양성이 매우 높다는 기존 연구 결과와 대비되는 것으로서, 너도밤나무는 핵 ìœ ì „ìžì˜ 다양성은 높으나 엽록체 ìœ ì „ìžì˜ 다양성은 낮은 것으로 판단되며, 이것은 두 가지 가설로 ì„¤ëª í• ìˆ˜ 있다. 하나는 너도밤나무의 조상이 울릉도로 이주하여 ì •ì°©í• ì´ˆê¸° 단계에서 엽록체 반수체형이 ì§€ì—­ì ì¸ 구조를 갖는 조상 모집단으로부터 ì¢ ìžê°€ ì§€ì†ì ìœ¼ë¡œ ìœ ìž ëœ 결과로 í•´ì„í• ìˆ˜ 있다. 다른 하나는 육지의 조상 모집단으로부터 새 또는 태풍에 의해 소수의 ì¢ ìžê°€ ìœ ìž ë˜ì–´ ì •ì°©í•œ 후, 바람에 의해 조상 모집단의 화분이 ì§€ì†ì ìœ¼ë¡œ ìœ ìž ëœ 결과인 것으로 ì¶”ë¡ í• ìˆ˜ 있다. 울릉도 내의 다양한 ê³ ìœ ìžìƒì‹ë¬¼ì˜ 기원을 ê·œëª í•˜ëŠ” 데 있어서 ëª¨ê³„ìœ ì „ì„ 함으로 인해 ì¢ ìžì˜ 이동을 ì¶”ì í• ìˆ˜ 있는 엽록체 DNA에 근거한 ë¹„êµê³„í†µì§€ë¦¬í•™ì  연구가 필요한 것으로 사료된다. 주요어: 너도밤나무, 엽록체 DNA, 반수체형, 울릉도

Use of nondestructive sensors to assess nitrogen status in potted poinsettia (Euphorbia pulcherrima L. (Willd. ex Klotzsch)) production

Utilizing precision farming techniques in a greenhouse setting to manage plant site-specific nitrogen (N) needs can help to prevent N deficiency, increase final plant quality, reduce cost of excessive fertilizer, and prevent N runoff. Optical sensors are a fast and nondestructive approach to estimate plant chlorophyll content by measuring the reflectance or absorbance of the green leaves. The objective of this study was to test the reliability of normalized difference vegetative index (NDVI) values calculated by the GreenSeeker™ hand held sensor as an indirect indicator of poinsettia (Euphorbia pulcherrima L. (Willd. ex Klotzsch) N status, and compare the sensors performance to other optical sensors on the market. The second objective of the study was to investigate if plant quality is improved by correcting N fertilizer application during production based on the sensor readings. The experiment was conducted in fall 2013. Poinsettia ‘Prestige Red’ and ‘Freedom Red’ pots were supplemented with 0, 5, 10, 15, and 20g of 15N-9P-12K controlled release fertilizer (CRF). Soil and plant analysis development (SPAD) chlorophyll meter, GreenSeeker™ NDVI sensor, and atLEAF meter readings were recorded for four consecutive weeks. Readings and visual qualities differences were monitored for significant separation between the different rates. At 40 days after planting (DAP), based on visual qualities differences, half of the deficient treatments were supplemented with extra fertilizer for treatment correction. All pots were completely randomized. All sensors values were compared to actual leaf N concentration to determine efficiency. Plants were assessed at the end of commercial production period by recording final height, final width, number of bracts, length of bract, dry weight, and salability. The GreenSeeker™ NDVI sensor correlated well with actual leaf N concentration during the vegetative phase of poinsettia production. As for the overall production period, SPAD and atLEAF meters showed an advantage with greater correlation to actual leaf N concentration. The GreenSeeker™ readings were less correlated with leaf N concentration at early stages of establishment due to plants small size and background noise, as well as at later stages of establishment due to anthesis. Poinsettia ‘Freedom Red’ responded better to treatment correction than ‘Prestige Red’. The correction treatments showed greater results for plant growth in the treatment correction 5 (+5g) compared to treatment correction 0 (+10g), and as good as the 10g treatment, indicating that the correction treatment could be used to correct deficiencies during production.

The Role of Population Origin and Microenvironment in Seedling Emergence and Early Survival in Mediterranean Maritime Pine (Pinus pinaster Aiton)

Understanding tree recruitment is needed to forecast future forest distribution. Many studies have reported the relevant ecological factors that affect recruitment success in trees, but the potential for genetic-based differences in recruitment has often been neglected. In this study, we established a semi-natural reciprocal sowing experiment to test for local adaptation and microenvironment effects (evaluated here by canopy cover) in the emergence and early survival of maritime pine (Pinus pinaster Aiton), an emblematic Mediterranean forest tree. A novel application of molecular markers was also developed to test for family selection and, thus, for potential genetic change over generations. Overall, we did not find evidence to support local adaptation at the recruitment stage in our semi-natural experiment. Moreover, only weak family selection (if any) was found, suggesting that in stressful environments with low survival, stochastic processes and among-year climate variability may drive recruitment. Nevertheless, our study revealed that, at early stages of recruitment, microenvironments may favor the population with the best adapted life strategy, irrespectively of its (local or non-local) origin. We also found that emergence time is a key factor for seedling survival in stressful Mediterranean environments. Our study highlights the complexity of the factors influencing the early stages of establishment of maritime pine and provides insights into possible management actions aimed at environmental change impact mitigation. In particular, we found that the high stochasticity of the recruitment process in stressful environments and the differences in population-specific adaptive strategies may difficult assisted migration schemes.

Is tree shelter protection an effective complement to weed competition management in improving the morpho-physiological response of holm oak planted seedlings?

Weed control is a key aspect that influences seedling response in newly-established plantations. Tree shelter protection may be an effective complement to weed control with a positive effect on the overall response of seedlings. Our study focused on assessing the morpho-physiological response of Holm oak (Quercus ilex L. ballota [Desf.] Samp.) plantations to weed control and individual protection as a combined cultural technique on a cropland site in southern Spain. The weed control treatments (cultivation, herbicide and mulch) were also applied in combination with tree shelters. Morpho-physiological variables including survival, aerial and root morphology, water potential, gas exchange and chlorophyll fluorescence were monitored over a 2-year period. Results showed that weed competition management treatments improved the seedling survival rate compared to the control treatment. Moreover, shelter was associated with a greater height growth. At early stages of establishment, and particularly under combined treatments, all plants invested more resources in their aerial parts than in their root system. Seedlings did not regulate water loss as a result of water stress, contrary to what would be expected in Mediterranean areas. Under all treatments, especially those combined with tree shelters, seedlings took up to 2 years to achieve morpho-physiological adaptation (i.e. height and diameter growths, water stress behavior) to site conditions. In addition, tree shelters promoted an increase in net photosynthesis compared to non-shelter treatments during the winter period. The tree shelters also limited the emergence of photo-inhibition phenomena in seedlings so that plants under combined treatments showed greater photo-chemical efficiency. Thus, this study supports the effectiveness of tree shelter protection as a complement to weed control treatments. More specifically, it suggests that combining individual protection (shelter) and weed control around seedlings is an interesting technique for reforestation of forest ecosystems in Mediterranean areas.

Early stages of establishment of the non-indigenous ascidian Herdmania momus (Savigny, 1816) in shallow and deep water environments on natural substrates in the Mediterranean Sea

The solitary ascidian Herdmania momus (Savigny, 1816) was first recorded in the Eastern basin of the Mediterranean, off the coast of Israel, in 1958. Since then, H. momus established along the shores of Israel, albeit restricted to artificial substrates (e.g., pier pillars, artificial reefs, and shipwrecks) and deeper waters (20–30 m) in comparison to its native range. It has recently spread to natural substrates (i.e. the rocky reef) and shallow water environments (< 1 m). Field surveys, augmented by observations by recreational divers, were conducted along the Israeli Mediterranean coast on natural substrates to assess the present distribution. H. momus was detected on natural substrates at eleven sites, some of them at very shallow depths. This change in the distribution of H. momus that now includes natural substrates in shallow waters along with deep water environments may have negative impacts on the native fauna in the Eastern Mediterranean.

Kinetochore-driven outgrowth of microtubules is a central contributor to kinetochore fiber maturation in crane-fly spermatocytes

We use liquid crystal polarized light imaging to record the life histories of single kinetochore (K-) fibers in living crane-fly spermatocytes, from their origins as nascent K-fibers in early prometaphase to their fully matured form at metaphase, just before anaphase onset. Increased image brightness due to increased retardance reveals where microtubules are added during K-fiber formation. Analysis of experimentally generated bipolar spindles with only one centrosome, as well as of regular, bicentrosomal spindles, reveals that microtubule addition occurs at the kinetochore-proximal ends of K-fibers, and added polymer expands poleward, giving rise to the robust K-fibers of metaphase cells. These results are not compatible with a model for K-fiber formation in which microtubules are added to nascent fibers solely by repetitive "search and capture" of centrosomal microtubule plus ends. Our interpretation is that capture of centrosomal microtubules-when deployed-is limited to early stages in establishment of nascent K-fibers, which then mature through kinetochore-driven outgrowth. When kinetochore capture of centrosomal microtubules is not used, the polar ends of K-fibers grow outward from their kinetochores and usually converge to make a centrosome-free pole.

Hierarchy of root functional trait values and plasticity drive early‐stage competition for water and phosphorus among grasses

Summary The link between species' functional traits and competitive abilities has been described as a major factor structuring plant communities. However, two diverging hypotheses have been proposed to explain this process: competition‐trait similarity and competition‐trait hierarchy. We performed a greenhouse experiment to determine whether grasses' root foraging strategies, from acquisitive or conservative functional groups, are linked to plant competitive ability and to test which hypothesis better explains interactions during the early stage of grass establishment under contrasting growth conditions. Two grass species of each functional group were grown with and without a neighbour under two levels of water and phosphorus supplies. Three functional traits related to plant competitive ability were measured on all plants grown without neighbours: specific root length (SRL), root phosphorus use efficiency and root length density. Above‐ground biomass was measured on plants grown with and without neighbours to evaluate the intensity of plant interaction. We demonstrated that for the three traits the intensity of interaction is driven mainly by hierarchical trait distance, that is, trait distance between target and neighbour, and not by trait similarity. Growth conditions strongly affected the significance of the relation between hierarchical distances and competition intensity. For the SRL hierarchical distance, this effect may be due to the most competitive species (with high SRL) being strongly impacted by water shortage, which modified the competitive hierarchy. Trait plasticity in response to stresses also appeared an important factor influencing the competitive ability of species, that is, species with the most plastic SRL in response to P stress were also the most competitive under P stress. A strong hierarchy exists among grasses' competitive abilities in non‐limiting growth conditions that is linked to their root functional traits and investment in the root system. Consequently, our results support the trait hierarchy hypothesis in its ability to describe competitive interaction among grasses during early stages of establishment. Our study provides evidence that root functional hierarchical trait distance and plasticity explain how grasses interact with their neighbours. This distance enables species to be ranked according to their competitive ability; however, this ranking may be influenced by the growth conditions and traits considered.

Validity of Darwin’s naturalization hypothesis relates to the stages of invasion

Naturalization is the introduction and establishment of a nonnative species with sustainable populations in a novel environment. The success of nonnative species may be influenced by their relatedness to the native flora. Darwin proposed that if a nonnative plant species is introduced into an environment without native congeners, the nonnative species will have a greater chance of becoming naturalized. To test Darwin’s naturalization hypothesis, we compiled a Kentucky plant database consisting of 821 vascular plant species and subsequently selected species traits and distribution information to determine the effect of congeneric species and traits on the probability of successful naturalization and invasion. The predictors used include reproductive traits, growth form, abundance, habitat type, native congeners, and biogeographical origin. We fit three sets of generalized linear mixed models (GLMMs) with a binomial family and a logit link. Backward selection based on minimizing the Akaike Information Criterion (AIC) was used in the analyses. Our results from these three sets of models clearly indicate that the validity of Darwin’s hypothesis is invasion stage dependent. More specific, the naturalized and invasive models (predicting the probability of being naturalized and invasive respectively) did not support Darwin’s naturalization hypothesis. The number of native congeners had no effect on the likelihood that a particular species would naturalize and become invasive. Our results suggest that Darwin’s naturalization hypothesis is more relevant during the early stage of establishment as demonstrated by the native model (predicting the probability of being native) and it becomes irrelevant during the late stages of invasion as indicated by the naturalized and invasive models. Thus, it can be generalized that biotic interactions, especially competition, is a critical determinant of initial success for nonnative species in the recipient communities. Once established, the fate of non-native species during the late stages of invasion may be more related to other factors such as biogeographic origin and habitat conditions. Furthermore, we found reproductive traits such as flowering phenology and flower type are associated with invasion success. We also recognized contrasting traits between native and nonnative species, indicating niche differentiation between these two groups of species. Niche overlapping was found as well among species regardless of the status of being native or otherwise. Our study provides a novel approach to advance the understanding of phylogenetic relatedness between nonnative species and native flora by integrating traits and niche concepts at the regional scale.

Environmental biology of an invasive population of signal crayfish in the River Stort catchment (southeastern England)

Assessment of population biology at early establishment stages is a fundamental component of conservation monitoring programmes, such as for invasive signal crayfish Pacifastacus leniusculus . Population structure, body condition (including its relation to density-dependence), spatial patterns and habitat relationships were examined between September and October 1997 along the lower River Stort catchment (Thames River catchment, UK). A higher proportion of females was observed at intermediate sizes, whereas the largest individuals were males. Body condition was positively associated with total crayfish abundance in females but not males. Principal components analysis of the population data (by gender and size) across sampling sites revealed three distinct groups (large males, large females, small crayfish of mixed gender), with large males having significantly (analysis of covariance) lower body condition. Multiple regression of crayfish population and habitat data revealed: increasing abundance was associated with high total suspended solids (e.g. burrowing behaviour) in all size/gender groups except medium and large males; decreasing abundances of large males and females with increasing hydrodynamic efficiency (i.e. Froude number); and increasing abundance of large males and females with increasing substratum roughness. Signal crayfish population structure in the River Stort suggests an elevated potential for dispersal and reinforcement throughout the River Lee catchment. The observed spatial and habitat segregation of crayfish by gender and size appears to reflect a female reproductive strategy that avoids contact between progeny and big aggressive/cannibalistic males. Furthermore, intra-male competition is the likely reason for the lower body condition of big males, given the lack of a negative relationship between male body condition and crayfish abundance. The comparison with established populations elsewhere shows that a sex-ratio biased towards females could be a good descriptor to detect invading populations. Potential threats posed by signal crayfish for the conservation of River Stort catchment are predation, competition and habitat alteration.

Assessment of genetic diversity of Typha angustifolia in the development of cattail stands

Typha angustifolia has ecological characteristics of clonal growth similar to Phragmites australis. The plant spreads byclonal growth and seed dispersal. In this study, for the three stands which have different settlement age at the Baksilji wetland in Korea, genetic diversity was estimated by random amplification of polymorphic DNA analysis to evaluate the change in genetic diversity of T. angustifolia during stand development in the same population. Stand (ST) 1 was the oldest and ST 4 was the youngest. ST 5 was in a small ditch out of the Baksilji. Although the ST 1, ST 2, and ST 3 did not differ significantly in vegetational or physical environment, the genetic diversity estimated according to Nei's gene diversity (h) and the Shannon index (i) increased in the order of ST 1 < ST 2 < ST 3 contrary to formative age. The genetic diversity of ST 4 was much higher than that of the other three stands. ST 4 has similar abiotic environmental conditions with slight T. angustifolia dominance, and seems to be in the early establishment stage. ST 5 differed from the other stands in vegetational and soil environments, which can result in stressful cattail conditions. Even though the ST 5 stand was not younger than the ST 4 stand, ST 5 showed the highest genetic diversity. Our results indicate that after early settlement of the T. angustifolia population, genetic diversity within the species decreased over time and that the decreasing pattern of genetic diversity within T. angustifolia stands is not likely to occur under stressful conditions.

Mayaca fluviatilis Aubl.: an ornamental aquatic with invasive potential in Sri Lanka

The ornamental aquatic plant industry in Sri Lanka has grown substantially during the last decade and there is a renewed demand for several exotic species. Mayaca fluviatilis, a submerged plant used in aquaria, is not recorded as a naturally occurring plant in Sri Lanka. However, recent studies recorded it in the wet zone of Sri Lanka and certain countries have recognized it as a problematic plant. The knowledge of the mode of propagation of invasive species is vital in the management of biological invasions. Therefore, the present study was conducted to investigate the propagation ability of vegetative parts of M. fluviatilis. A field survey was conducted in the wet zone of Sri Lanka, and populations of M. fluviatilis were monitored between 2006 and 2009. The propagation ability of different maturity stages of stem cuttings (terminal, middle and basal) were investigated, and terminal stem cuttings with five different lengths (2, 4, 6, 8 and 10 cm) were used to investigate the propagation ability of fragmented vegetative parts. Terminal shoots showed the highest survival rates and significantly high (P < 0.05) shoot and root lengths compared to middle and basal parts of the stem cuttings. In the other experiment with terminal stem cuttings with different lengths, all the stem fragments were capable of developing into a new plant. Increasing lengths of fragments was significantly related to the number of roots. Nevertheless, as even the 2-cm fragment was capable of developing into a new plant, removal of even the smallest fragments is necessary to control this plant. Submerged plants can spread easily through fragmentation and manual removal will likely increase its spread. Nevertheless, it is considered as effective for small infestations. Therefore, repeated removal of plant parts can be suggested as an ecologically sound management approach to prevent further spread of M. fluviatilis since it is in the early stage of establishment.

The role of species traits and taxonomic patterns in alien bird impacts

ABSTRACTAim To test whether the distribution of alien bird impacts varies across bird families and regions of origin, and to investigate whether species traits associated with successful introductions can predict which species will have negative impacts in the new area of introduction.Location Europe and the Mediterranean Basin.Methods Combining historical information and published literature about negative economic, biological and human health impacts, we compared the distribution of impacts among bird families and native origins of bird species for three major types of impact (economic, biodiversity and human health). We examined the relationships between ecological, biological and reproductive characteristics of species and the severity of the impacts.Results The majority of alien species with reported impacts originated from the Afrotropical, Indo‐Malayan and Palaearctic biogeographical regions. The distribution of alien bird species in Europe with reported impacts shows a taxonomic bias and largely mirrors patterns of establishment. While most species had primarily either economic or biodiversity impacts, several species in the Anatidae, Corvidae, Passeridae, Phasianidae and Sturnidae families were associated with moderate to serious negative impacts on both economic resources and native biodiversity. After controlling for taxonomic effects, species with the greatest overall impacts were habitat generalists and multi‐brooded, while species with smaller bodies and the tendency to form large feeding or roosting flocks were linked with greater impacts on native biodiversity.Main conclusions This study presents the first synthesis of published impact data for alien birds and provides a broad‐scale perspective on factors that contribute to their impacts. The results show that accounting for both species traits and taxonomy improves our ability to predict the impacts of alien bird species. Because several species are currently in the early stages of establishment in Europe, there may be an opportunity to limit negative impacts with efforts that promote proactive strategies against species and families possessing the above characteristics.

A STUDY ON THE STAKEHOLDER CONSIDERATION RELATED TO COOPERATION IN THE JOINT HOUSING PROJECT AFTER THE HANSHIN-AWAJI EARTHQAKE

The purpose of this paper is to examine the residents and related designer consultants evaluation of the joint housing project after Hanshin-Awaji earthquake. We researched 7 condominiums provided by the joint housing project. We analyzed 102 documents of residents and questioned to 123 households of their evaluation for the joint housing project by questionnaires. And we questioned 20 designer consultants of 18 joint housing projects. And we questioned 8 local government staff who related to these projects.Several strategies which are necessary to support the establishment of a joint housing project are as follows.1) Create an enabling environment for the public developer's participation, because there are small number of family who transferred to the joint housing projects, 2) Encourage the intention of private organization such as NPO to participate, 3) Attempt the public support for the expense of the adviser which emerge at the early stage of establishment of the project.

Patterns of exotic plant invasions in Pennsylvania’s Allegheny National Forest using intensive Forest Inventory and Analysis plots

Intensive Forest Inventory and Analysis (FIA) plot data collected in the Allegheny National Forest (ANF), Pennsylvania, between 1999 and 2006 were evaluated for their ability to predict ANF’s vulnerability to invasion by exotic plants. A total of 26 variables classified by biotic, abiotic, or disturbance characteristics were examined. Likelihood of colonization by invasive exotic and non-invasive exotic plants was analyzed using a logistic regression model. Approximately, 11% of the 449 species documented in these plots were exotic, which is higher than has been found in other northeastern forested plots. Only 1% of the ANF flora was invasive exotic plants and these were at low abundance, confirming that most invasions are still at an early stage of establishment. Sites richer in native or non-invasive exotic plants and with more alkaline soils were more likely to be invaded. Younger forests, forests with non-forest patches present, and forests rich in native species were more likely to be colonized by exotic (invasive or non-invasive) plants. Frangula alnus, which is starting to spread locally, differed from the other invasive exotic species in terms of its association with high sapling density to tree density ratios, high soil nitrogen levels, and the presence of fire. Variables representing mortality due to beech bark disease and distance to the nearest exotic planting manifested counterintuitive results. In both cases, the combined occurrence of mortality due to beech bark disease or a close (less than 500 m away) known propagule source and the presence of an invasive or non-invasive exotic plant was rare. We encourage increased use of intensive sampling for FIA in the U.S.A. and similar monitoring programs in other countries, but suggest adding a step to the plot selection phase that would allow forest-wide or regional stratified sampling of typically coarse-scale variables, such as historic or predicted defoliation or fire events, and forest or land type. A more accurate picture of the importance of disturbance variables in defining forest vulnerability to plant invasion may be achieved.

Mollusc grazing may constrain the ecological niche of the old forest lichen Pseudocyphellaria crocata

This study reports on mollusc grazing of two epiphytic cyanobacterial lichens (Pseudocyphellaria crocata and Lobaria pulmonaria) transplanted within three Picea abies-dominated boreal rain forest stands (clear-cut, young and old forests) in west central Norway. Grazing was particularly high in transplants located in the old forest and was almost absent in clear-cut transplants. Grazing marks were absent on natural thalli on nearby spruce twigs (required creeping distance for mollusc from the ground >4 m). Transplantation of lichens from twigs to artificial transplantation frames reduced the creeping distance to 1.2 m, and caused a significant increase in grazing damage in P. crocata. Given a paired choice under transplantation, molluscs consistently preferred P. crocata and avoided L. pulmonaria, implying species-specific differences in herbivore defence. Pseudocyphellaria crocata has a much lower content of the medullary depsidones stictic and constictic acid than L. pulmonaria. Heavy grazing occurred in the P. crocata thalli lowest in these two depsidones. The upper part of the medulla hosting the photobiont was the preferred fodder for grazing molluscs. Molluscs avoided the yellow soralia in P. crocata (localised pulvinic acid), suggesting a role for pulvinic acid in preventing grazing of detached soredia and early establishment stages. The preference of P. crocata for thin spruce twigs is probably a result of a lower grazing pressure on twigs compared to e.g. deciduous stems that frequently support the better defended L. pulmonaria. Ongoing climate changes with increased annual rainfall and milder winters have presumably increased mollusc grazing, particularly in SW parts of Norway which have more species of lichen-feeding molluscs than the boreal sites studied. These temperate areas lacking natural spruce populations have recently experienced reported extinctions of the poorly defended P. crocata from rocks and deciduous stems prone to mollusc grazing. Lichen-feeding molluscs have likely played a role in these extinctions, causing spruce twigs in Atlantic boreal forests to be a last strong foothold for P. crocata in Scandinavia.

The Simulated Effects of Iron Dust and Acidity During the Early Stages of Establishment of Two Coastal Plant Species

In Brazil’s littoral, many iron ore industries are located in areas of restinga, a type of coastal ecosystem; such industries represent stationary sources of iron and acid particulates. The industrial sector is under expansion, threatening the already fragile ecosystem. In the present study, the simulated impact of these emissions was studied on the early establishment stages of two native plant species, Sophora tomentosa and Schinus terebinthifolius. The results indicate that S. tomentosa display deficient germination and low root tolerance when exposed to iron dust and acidity. Toxic iron concentrations were found to accumulate only in the roots of S. tomentosa plants exposed to increasing doses of iron dust. In these plants, initial growth was reduced, leading to the conclusion that S. tomentosa was unable to regulate, and, thus, to overcome, the effects of the iron dust in the substrate. In contrast, the germination, root tolerance index, and initial growth of S. terebinthifolius were not affected by iron dust and acidity, revealing the species’ resistance to these pollutants. We propose that under similar field conditions, S. tomentosa would be adversely affected, whereas S. terebinthifolius would thrive. On a long-term basis, this imbalance is likely to interfere in the vegetational composition and dynamics of the affected ecosystem.

Plant form and function

Plant form and function

Effective gene dispersal and female reproductive success in Mediterranean maritime pine (Pinus pinaster Aiton)

Understanding population-scale processes that affect allele frequency changes across generations is a long-standing interest in genetic, ecological and evolutionary research. In particular, individual differences in female reproductive success and the spatial scale of gene flow considerably affect evolutionary change and patterns of local selection. In this study, a recently developed maximum-likelihood (ML) method based on established offspring, the Seedling Neighbourhood Model, was applied and exponentially shaped dispersal kernels were fitted to both genetic and ecological data in a widespread Mediterranean pine, Pinus pinaster Aiton. The distribution of female reproductive success in P. pinaster was very skewed (about 10% of trees mothered 50% of offspring) and significant positive female selection gradients for diameter (gamma = 0.7293) and cone crop (gamma = 0.4524) were found. The selective advantage of offspring mothered by bigger trees could be due to better-quality seeds. These seeds may show more resilience to severe summer droughts and microsite variation related to water and nutrient availability. Both approaches, ecological and of parentage, consistently showed a long-distance dispersal component in saplings that was not found in dispersal kernels based on seed shadows, highlighting the importance of Janzen-Connell effects and microenvironmental variation for survival at early stages of establishment in this Mediterranean key forest tree.