Phylogenetic indices and temporal and spatial scales shape the neighborhood effect on seedling survival in a mid-mountain moist evergreen broad-leaved forest, Gaoligong Mountains, Southwestern China.

Density dependence and habitat filtering have been proposed to aid in understanding community assembly and species coexistence. Phylogenetic relatedness between neighbors was used as a proxy for assessing the degree of ecological similarity among species. There are different conclusions regarding the neighborhood effect in previous studies with different phylogenetic indices or at different spatiotemporal scales. However, the effects of density dependence, neighbor phylogenetic relatedness, and habitat filtering on seedling survival with different phylogenetic indices or at different temporal and spatial scales are poorly understood. We monitored 916 seedlings representing 56 woody plant species within a 4-ha forest dynamics plot for 4 years (from 2020 to 2023) in a subtropical mid-mountain moist evergreen broad-leaved forest in the Gaoligong Mountains, Southwestern China. Using generalized linear mixed models, we tested whether and how four phylogenetic indices: total phylogenetic distance (TOTPd), average phylogenetic distance (AVEPd), relative average phylogenetic distance (APd'), and relative nearest taxon phylogenetic distance (NTPd'), three temporals (1, 2, and 3 years), and spatial scales (1, 2, and 4 ha) affect the effect of density dependence, phylogenetic density dependence, and habitat filtering on seedling survival. We found evidence of the effect of phylogenetic density dependence in the 4-ha forest dynamics plot. The effects of density dependence, phylogenetic density dependence, and habitat filtering on seedling survival were influenced by phylogenetic indices and temporal and spatial scales. The effects of phylogenetic density dependence and habitat filtering on seedling survival were more conspicuous only at 1-year intervals, compared with those at 2- and 3-year intervals. We did not detect any effects of neighborhood or habitat factors on seedling survival at small scales (1 and 2 ha), although these effects were more evident at the largest spatial scale (4 ha). These findings highlight that the effects of local neighborhoods and habitats on seedling survival are affected by phylogenetic indices as well as temporal and spatial scales. Our study suggested that phylogenetic index APd', shortest time scale (1 year), and largest spatial scales (4 ha) were suitable for neighborhood studies in a mid-mountain moist evergreen broad-leaved forest in Gaoligong Mountains. Phylogenetic indices and spatiotemporal scales have important impacts on the results of the neighborhood studies.

Intraspecific plant-soil feedback in four tropical tree species is inconsistent in a field experiment.

PREMISE: Soil microbes can influence patterns of diversity in plant communities via plant-soil feedbacks. Intraspecific plant-soil feedbacks occur when plant genotype leads to variations in soil microbial composition, resulting in differences in the performance of seedlings growing near their maternal plants versus seedlings growing near nonmaternal conspecific plants. How consistently such intraspecific plant-soil feedbacks occur in natural plant communities is unclear, especially in variable field conditions. METHODS: In an in situ experiment with four native tree species on Barro Colorado Island (BCI), Panama, seedlings of each species were transplanted beneath their maternal tree or another conspecific tree in the BCI forest. Mortality and growth were assessed at the end of the wet season (~4 months post-transplant) and at the end of the experiment (~7 months post-transplant). RESULTS: Differences in seedling performance among field treatments were inconsistent among species and eroded over time. Effects of field environment were detected at the end of the wet season in two of the four species: Virola surinamensis seedlings had higher survival beneath their maternal tree than other conspecific trees, while seedling survival of Ormosia macrocalyx was higher under other conspecific trees. However, these differences were gone by the end of the experiment. CONCLUSIONS: Our results suggest that intraspecific plant-soil feedbacks may not be consistent in the field for tropical tree species and may have a limited role in determining seedling performance in tropical tree communities. Future studies are needed to elucidate the environmental and genetic factors that determine the incidence and direction of intraspecific plant-soil feedbacks in plant communities.

Verified hypotheses on the "nurse" and "burial" effects on introduced Quercus rubra regeneration in a mesic Scots pine forest.

A previous study on the encroachment of North American northern red oak Quercus rubra L. into the mesic Scots pine forest (in central Poland) revealed high abundances of seedlings and saplings under shrubs, with lower abundances in open areas or clumps of bilberry Vaccinium myrtillus L. It was unclear whether the regeneration success of Q. rubra is enhanced by the presence of shrubs due to their "nurse effect", and how burying acorns of different sizes in soil or moss affects the survival of oak seeds and seedlings (a "burial effect"). Results of a previous observational study were verified in an experimental study: a pool of 900 large-, medium-, and small-sized acorns was sown under moss cover in open areas and within bilberry clumps and in soil under shrubs in 2018 and monitored for 3 years in natural conditions. The majority of sown acorns were lost, mainly due to acorn pilferage, lack of germination and the death of sprouting acorns. However, acorn and seedling survival depended significantly on acorn size and differed among the microsites studied. Viable seedlings were twice as likely to develop from large- and medium-sized as from small-sized acorns, and they grew mainly from acorns sown under moss cover, confirming a positive "burial effect." Seedling survival was three times higher in bilberry and open areas, than under shrubs; however, seedlings "nursed" by shrubs were less threatened by large ungulates. Only a small part of the pool of sown acorns contributes to the reproductive success of Q. rubra in the mesic Scots pine forest. Microsites characteristic to this type of forest are suitable for northern red oak regeneration; however, bilberry favors acorn survival and germination and early seedling growth, moss cover favors acorn survival and germination, while shrubs protect surviving seedlings from herbivory.

Long-term seedling and small sapling census data from the Barro Colorado Island 50 ha Forest Dynamics Plot, Panama.

Tropical forests are well known for their high woody plant diversity. Processes occurring at early life stages are thought to play a critical role in maintaining this high diversity and shaping the composition of tropical tree communities. To evaluate hypothesized mechanisms promoting tropical tree species coexistence and influencing composition, we initiated a census of woody seedlings and small saplings in the permanent 50 ha Forest Dynamics Plot (FDP) on Barro Colorado Island (BCI), Panama. Situated in old-growth, lowland tropical moist forest, the BCI FDP was originally established in 1980 to monitor trees and shrubs ≥1 cm diameter at 1.3 m above ground (dbh) at ca. 5-year intervals. However, critical data on the dynamics occurring at earlier life stages were initially lacking. Therefore, in 2001 we established a 1-m2 seedling plot in the center of every 5 × 5 m section of the BCI FDP. All freestanding woody individuals ≥20 cm tall and <1 cm dbh (hereafter referred to as seedlings) were tagged, mapped, measured, and identified to species in 19,313 1-m2 seedling plots. Because seedling dynamics are rapid, we censused these seedling plots every 1-2 years. Here, we present data from the 14 censuses of these seedling plots conducted between the initial census in 2001 to the most recent census, in 2018. This data set includes nearly 1 M observations of ~185,000 individuals of >400 tree, shrub, and liana species. These data will permit spatially-explicit analyses of seedling distributions, recruitment, growth, and survival for hundreds of woody plant species. In addition, the data presented here can be linked to openly-available, long-term data on the dynamics of trees and shrubs ≥1 cm dbh in the BCI FDP, as well as existing data sets from the site on climate, canopy structure, phylogenetic relatedness, functional traits, soil nutrients, and topography. This data set can be freely used for non-commercial purposes; we request that users of these data cite this data paper in all publications resulting from the use of this data set.

Climate and fragment area jointly affect the annual dynamics of seedlings in different functional groups in the Thousand Island Lake.

Habitat fragmentation and climate change are the two main threats to global biodiversity. Understanding their combined impact on plant community regeneration is vital for predicting future forest structure and conserving biodiversity. This study monitored the seed production, seedling recruitment and mortality of woody plants in the Thousand Island Lake, a highly fragmented anthropogenic archipelago, for 5 years. We analyzed the seed-seedling transition, seedling recruitment and mortality of different functional groups in the fragmented forests and conducted correlation analyses involving climatic factors, island area, and plant community abundance. Our results showed that: 1) shade-tolerant and evergreen species had higher seed-seedling transition, seedling recruitment and survival rate than shade-intolerant and deciduous species in time and space, and these advantages increased with the island area. 2) Seedlings in different functional groups responded differently to island area, temperature and precipitation. 3) Increasing active accumulated temperature (the sum of the mean daily temperature above 0 °C) significantly increased seedling recruitment and survival, and warming climate favored the regeneration of evergreen species. 4) The seedling mortality rate of all plant functional groups increased with the increase of island area, but the increasing strength weakened significantly with the increase of the annual maximum temperature. These results suggested that the dynamics of woody plant seedlings varied among functional groups, and can be regulated separately and jointly by fragmentation and climate.

Cultivation Using Coir Substrate and P or K Enriched Fertilizer Provides Higher Resistance to Drought in Ecologically Diverse Quercus Species.

Nursery cultivation practices can be modified to increase resistance to water stress in forest seedlings following field establishment, which may be increasingly important under climate change. We evaluated the morphological (survival, growth) and physiological (chlorophyll fluorescence, leaf water potential) responses to water stress for three ecologically diverse Quercus species (Q. robur, Q. pubescens, and Q. ilex) with varying traits resulting from the combination of growing media (peat, coir) and fertilization (standard, P-enriched, K-enriched). For all species under water stress, seedlings grown in coir had generally higher growth than those grown in peat. Seedlings fertilized with P performed better, particularly for survival; conversely, K fertilization resulted in inconsistent findings. Such results could be explained by a combination of factors. P fertilization resulted in higher P accumulation in seedlings, while no K accumulation was observed in K fertilized seedlings. As expected, the more drought-sensitive species, Q. robur, showed the worst response, while Q. pubescens had a drought resistance equal or better to Q. ilex despite being classified as intermediate in drought resistance in Mediterranean environments.

Herbivory Amplifies Adverse Effects of Drought on Seedling Recruitment in a Keystone Species of Western North American Rangelands.

Biotic interactions can affect a plant's ability to withstand drought. Such an effect may impact the restoration of the imperiled western North American sagebrush steppe, where seedlings are exposed to summer drought. This study investigated the impact of herbivory on seedlings' drought tolerance for a keystone species in this steppe, the shrub Artemisia tridentata. Herbivory effects were investigated in two field experiments where seedlings were without tree protectors or within plastic or metal-mesh tree protectors. Treatment effects were statistically evaluated on herbivory, survival, leaf water potential, and inflorescence development. Herbivory occurrence was 80% higher in seedlings without protectors. This damage occurred in early spring and was likely caused by ground squirrels. Most plants recovered, but herbivory was associated with higher mortality during the summer when seedlings experienced water potentials between -2.5 and -7 MPa. However, there were no differences in water potential between treatments, suggesting that the browsed plants were less tolerant of the low water potentials experienced. Twenty months after outplanting, the survival of plants without protectors was 40 to 60% lower than those with protectors. The percentage of live plants developing inflorescences was approximately threefold higher in plants with protectors. Overall, spring herbivory amplified susceptibility to drought and delayed reproductive development.

Experimental and observational evidence of negative conspecific density dependence in temperate ectomycorrhizal trees.

Conspecific negative density dependence (CNDD) promotes tree species diversity by reducing recruitment near conspecific adults due to biotic feedbacks from herbivores, pathogens, or competitors. While this process is well-described in tropical forests, tests of temperate tree species range from strong positive to strong negative density dependence. To explain this, several studies have suggested that tree species traits may help predict the strength and direction of density dependence: for example, ectomycorrhizal-associated tree species typically exhibit either positive or weaker negative conspecific density dependence. More generally, the strength of density dependence may be predictably related to other species-specific ecological attributes such as shade tolerance, or the relative local abundance of a species. To test the strength of density dependence and whether it affects seedling community diversity in a temperate forest, we tracked the survival of seedlings of three ectomycorrhizal-associated species experimentally planted beneath conspecific and heterospecific adults on the Prospect Hill tract of the Harvard Forest, in Massachusetts, USA. Experimental seedling survival was always lower under conspecific adults, which increased seedling community diversity in one of six treatments. We compared these results to evidence of CNDD from observed sapling survival patterns of 28 species over approximately 8 years in an adjacent 35-ha forest plot. We tested whether species-specific estimates of CNDD were associated with mycorrhizal association, shade tolerance, and local abundance. We found evidence of significant, negative conspecific density dependence (CNDD) in 23 of 28 species, and positive conspecific density dependence in two species. Contrary to our expectations, ectomycorrhizal-associated species generally exhibited stronger (e.g., more negative) CNDD than arbuscular mycorrhizal-associated species. CNDD was also stronger in more shade-tolerant species but was not associated with local abundance. Conspecific adult trees often have a negative influence on seedling survival in temperate forests, particularly for tree species with certain traits. Here we found strong experimental and observational evidence that ectomycorrhizal-associating species consistently exhibit CNDD. Moreover, similarities in the relative strength of density dependence from experiments and observations of sapling mortality suggest a mechanistic link between negative effects of conspecific adults on seedling and sapling survival and local tree species distributions.

Seed and seedling predation by vertebrates mediates the effects of adult trees in two temperate tree species.

Specialised natural enemies can locally suppress seeds and seedlings near conspecific adults more than far from them. Whilst this is thought to facilitate species coexistence, the relative contribution of multiple enemies to whether heterospecific seeds and seedlings rather than conspecifics perform better beneath a particular adult species remains less clear, especially in regions with spatially extensive monodominant stands. We designed a field exclusion experiment to separate the effects of fungi, insects and vertebrates on the seedling establishment and early survival of two temperate tree species, Fagus sylvatica and Picea abies, in the adult tree monocultures of these species. Our experiment demonstrates the key role of vertebrates in mediating the effects of adult trees on seeds and seedlings. Due to vertebrates and partly insects, Fagus sylvatica seedlings survived worse beneath conspecific than heterospecific adults and were also outperformed by Picea abies seedlings beneath their own adults. Picea abies seedling establishment was higher beneath conspecific than heterospecific adults, but Fagus sylvatica seedlings outperformed them beneath their own adults. The impact of enemies on Picea abies establishment beneath conspecific adults was less clear. Fungi did not influence seedling establishment and survival. Our findings highlight the need to compare enemy impacts on each seedling species beneath conspecific and heterospecific adults with their impacts on conspecific and heterospecific seedlings beneath a particular adult species. Such evaluations can shed more light on the role of enemies in tree communities by identifying the plant-enemy interactions that facilitate species coexistence and those that promote species monodominance.

Seedling survival simultaneously determined by conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity in a subtropical forest in Taiwan.

Density dependence and habitat heterogeneity have been recognized as important driving mechanisms that shape the patterns of seedling survival and promote species coexistence in species-rich forests. In this study, we evaluated the relative importance of density dependence by conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity on seedling survival in the Lienhuachih (LHC) Forest, a subtropical, evergreen forest in central Taiwan. Age-specific effects of different variables were also studied. We monitored the fates of 1,642 newly recruited seedlings of woody plants within a 25-ha Forest Dynamics Plot for 2 years. The effects of conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity on seedling survival were analyzed by generalized linear mixed models. Our results indicated that conspecific negative density dependence (CNDD) had a strong impact on seedling survival, and the effects of CNDD increased with seedling age. Heterospecific positive density dependence (HPDD) and phylogenetic positive density dependence (PPDD) had a significant influence on the survival of seedlings, and stronger HPDD and PPDD effects were detected for older seedlings. Furthermore, seedling survival differed among habitats significantly. Seedling survival was significantly higher in the plateau, high-slope, and low-slope habitats than in the valley. Overall, our results suggested that the effects of CNDD, HPDD, PPDD, and habitat heterogeneity influenced seedling survival simultaneously in the LHC subtropical forest, but their relative importance varied with seedling age. Such findings from our subtropical forest were slightly different from tropical forests, and these contrasting patterns may be attributed to differences in abiotic environments. These findings highlight the importance to incorporate phylogenetic relatedness, seedling age, and habitat heterogeneity when investigating the impacts of density dependence on seedling survival that may contribute to species coexistence in seedling communities.

Recruitment of pioneer trees with physically dormant seeds under climate change: the case of Vachellia pennatula (Fabaceae) in semiarid environments of Mexico.

Most tree species native to arid and semiarid ecosystems produce seeds with physical dormancy, which have impermeable coats that protect them from desiccation and prevent germination when the environmental conditions are unfavorable for seedling establishment. This dormancy mechanism may confer some degree of tolerance to seeds facing warmer and drier conditions, as those expected in several regions of the world because of climate change. Scarification of these seeds (removal of protective coats) is required for stimulating germination and seedling development. However, as scarification exposes seeds to the external environmental conditions, it can promote desiccation and viability loss in the future. To test these hypotheses, we performed field experiments and sowed scarified and unscarified seeds of a pioneer tree native to semiarid ecosystems of Mesoamerica (Vachellia pennatula) under the current climate and simulated climate change conditions. The experiments were conducted at abandoned fields using open-top chambers to increase temperature and rainout shelters to reduce rainfall. We measured microenvironmental conditions within the experimental plots and monitored seedling emergence and survival during a year. Air temperature and rainfall in climate change simulations approached the values expected for the period 2041-2080. Seedling emergence rates under these climatic conditions were lower than under the current climate. Nevertheless, emergence rates in climate change simulations were even lower for scarified than for unscarified seeds, while the converse occurred under the current climate. On the other hand, although survival rates in climate change simulations were lower than under the current climate, no effects of the scarification treatment were found. In this way, our study suggests that climate change will impair the recruitment of pioneer trees in semiarid environments, even if they produce seeds with physical dormancy, but also indicates that these negative effects will be stronger if seeds are scarified.

Identification of cold tolerance QTLs at the bud burst stage in 211 rice landraces by GWAS.

BACKGROUND: Rice is a crop that is very sensitive to low temperature, and its morphological development and production are greatly affected by low temperature. Therefore, understanding the genetic basis of cold tolerance in rice is of great significance for mining favorable genes and cultivating excellent rice varieties. However, there have been limited studies focusing on cold tolerance at the bud burst stage; therefore, considerable attention should be given to the genetic basis of cold tolerance at this stage. RESULTS: In this study, a natural population consisting of 211 rice landraces collected from 15 provinces in China and other countries was used for the first time to evaluate cold tolerance at the bud burst stage. Population structure analysis showed that this population was divided into two groups and was rich in genetic diversity. Our evaluation results confirmed that japonica rice was more tolerant to cold at the bud burst stage than indica rice. A genome-wide association study (GWAS) was performed with the phenotypic data of 211 rice landraces and a 36,727 SNP dataset under a mixed linear model. Twelve QTLs (P < 0.0001) were identified for the seedling survival rate (SR) after treatment at 4 °C, in which there were five QTLs (qSR2-2, qSR3-1, qSR3-2, qSR3-3 and qSR9) that were colocalized with those from previous studies and seven QTLs (qSR2-1, qSR3-4, qSR3-5, qSR3-6, qSR3-7, qSR4 and qSR7) that were reported for the first time. Among these QTLs, qSR9, harboring the most significant SNP, explained the most phenotypic variation. Through bioinformatics analysis, five genes (LOC_Os09g12440, LOC_Os09g12470, LOC_Os09g12520, LOC_Os09g12580 and LOC_Os09g12720) were identified as candidates for qSR9. CONCLUSION: This natural population consisting of 211 rice landraces combined with high-density SNPs will serve as a better choice for identifying rice QTLs/genes in the future, and the detected QTLs associated with cold tolerance at the bud burst stage in rice will be conducive to further mining favorable genes and breeding rice varieties under cold stress.

Low Temperature Antioxidant Activity QTL Associate with Genomic Regions Involved in Physiological Cold Stress Tolerance Responses in Rice (Oryza sativa L.).

Boosting cold stress tolerance in crop plants can minimize stress-mediated yield losses. Asian rice (Oryza sativa L.), one of the most consumed cereal crops, originated from subtropical regions and is generally sensitive to low temperature environments. Within the two subspecies of rice, JAPONICA, and INDICA, the cold tolerance potential of its accessions is highly variable and depends on their genetic background. Yet, cold stress tolerance response mechanisms are complex and not well understood. This study utilized 370 accessions from the Rice Diversity Panel 1 (RDP1) to investigate and correlate four cold stress tolerance response phenotypes: membrane damage, seedling survivability, and catalase and anthocyanin antioxidative activity. Most JAPONICA accessions, and admixed accessions within JAPONICA, had lower membrane damage, higher antioxidative activity, and overall, higher seedling survivability compared to INDICA accessions. Genome-wide association study (GWAS) mapping was done using the four traits to find novel quantitative trait loci (QTL), and to validate and fine-map previously identified QTL. A total of 20 QTL associated to two or more traits were uncovered by our study. Gene Ontology (GO) term enrichment analyses satisfying four layers of filtering retrieved three potential pathways: signal transduction, maintenance of plasma membrane and cell wall integrity, and nucleic acids metabolism as general mechanisms of cold stress tolerance responses involving antioxidant activity.

Data on how tree planting and management practices influence tree seedling survival in Kenya and Ethiopia.

Understanding which trees farmers prefer, what determines their survival and enhancing farmer knowledge of tree management is key to increasing tree cover in agricultural landscapes. This article presents data on tree seedling survival under different tree planting and management practices in Kenya and Ethiopia. Data were collected from 1600 households across three Counties in Kenya and 173 households across four Woredas in Ethiopia, using a structured questionnaire which was administered through the Open Data Kit. Data on seedling survival were collected at least six months after tree seedlings were planted. To understand how planting and management practices influence tree planting across the different socioeconomic and biophysical contexts, both household level and individual tree level data were collected. Household level data included socio-economic and biophysical characteristics of the households while tree specific data included when the tree seedling was planted, where it was planted, the management practices employed and whether surviving. The datasets described in this article help understand which options confer the best chance survival for the planted seedlings and in which socio-economic and biophysical contexts they are most successful.

Soil fungal networks moderate density-dependent survival and growth of seedlings.

Pathogenic and mutualistic fungi have contrasting effects on seedling establishment, but it remains unclear whether density-dependent survival and growth are regulated by access to different types of mycorrhizal fungal networks supported by neighbouring adult trees. Here, we conducted an extensive field survey to test how mycorrhizal and pathogenic fungal colonization of arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) seedlings in a subtropical forest respond to density of neighbouring adult trees. In addition, we undertook a hyphal exclusion experiment to explicitly test the role of soil fungal networks in driving density-dependent effects on seedling growth and survival. Conspecific adult density was a strong predictor for the relative abundance of putative pathogens, which was greater in roots of AM than of ECM seedlings, while mycorrhizal fungal abundance and colonization were not consistently affected by conspecific adult density. Both ECM and AM fungal networks counteracted conspecific density-dependent mortality, but ECM fungi were more effective at weakening the negative effects of high seedling density than AM fungi. Our findings reveal a critical role of common fungal networks in mitigating negative density-dependent effects of pathogenic fungi on seedling establishment, which provides mechanistic insights into how soil fungal diversity shapes plant community structure in subtropical forests.

Revisiting biotic and abiotic drivers of seedling establishment, natural enemies and survival in a tropical tree species in a West Africa semi-arid biosphere reserve.

Biotic and abiotic drivers of seedling establishment and survival are fundamental not only for elucidating processes occurring at plant early life stages, but also for assisting species natural regeneration. Keystone, multipurpose and economically important tree species such as Afzelia africana Sm. are reportedly facing recruitment constraints, yet little is known about how abiotic and biotic factors shape the species seedling dynamics. Here, we monitored the species seedlings over one year across three seasons in West Africa savannahs to determine how conspecific and heterospecific biotic neighborhood and habitat heterogeneity correlate with initial seedling density, leaves' fungal infection and herbivory and how all these factors combined, influence the species seedling survival. Seedling densities increased with increasing conspecific adult densities, and were highest in tree savannahs and on sandy-silt soils. Leaves' fungal infection and herbivory were also positively associated with conspecific adult density, but were more abundantly observed in tree savannahs than in shrub savannahs. Seedling survival was constrained on higher slope, and negatively affected by conspecific adult density, especially in shrub savannahs. There was a strong evidence for negative density-dependence effects of conspecific adults on seedling survival, which operated through negative effects of herbivory and fungal infection. Habitat heterogeneity was also an important driver, which modulated biotic factors' effects on seedling survival: tree savannahs promote positive conspecific density-dependence of seedling fungal infection and herbivory more than shrub savannahs. Nonetheless, seedlings were more sensitive to natural enemies in shrub savannahs, suggesting increased negative conspecific density-dependence effects on seedling survival in less dense vegetation, possibly as a result of enhanced specialization of predators and pathogens on a limited set of species. The study brings important insights into the mechanisms that drive the establishment and survival of the species seedling, which should be considered in the design of management activities aiming at the conservation of this endangered species.

Species Identity and Initial Size Rather Than Neighborhood Interactions Influence Survival in a Response-Surface Examination of Competition.

To measure intraspecific and interspecific interaction coefficients among tree species is the key to explore the underlying mechanisms for species coexistence and biodiversity maintenance in forests. Through the response surface experimental design, we established a long-term field experiment by planting 27,300 seedlings of four tree species (Erythrophleum fordii, Pinus massoniana, Castanopsis fissa, and Castanopsis carlesii) in 504 plots in different species combinations (six pairwise combinations of four species), abundance proportions (five abundance proportions of two species, i.e. A: B = 1:0, 3:1, 1:1, 1:3, 0:1), and stand densities (25, 36, 64, and 100 seedlings per plot). In this initial report, we aimed to quantify the relative importance of biotic and abiotic factors on seedling survival at the early stage of growth, which is a critical period for seedling establishment. We found that plot-level seedling survival rate was determined by species combination and their abundance proportion rather than stand density. At the individual level, individual survival probability was mainly explained by species identity, initial seedling size, and soil conditions rather than neighborhood competition. Our study highlights that the seedling intrinsic properties may be the key factors in determining seedling survival rate, while neighborhood effects were not yet prominent at the seedling life stage.

Can intensive silvicultural management minimize the effects of frost on restoration plantations in subtropical regions?

Temperature is one of the main factors that influence field establishment of forest species. In high-altitude tropical regions and in subtropical regions, the occurrence of frost represents an important restriction in the trajectory and continuity of ecological processes. Thus, we aimed to characterize frost damage in nine native forest species under different silvicultural management schemes in plantations for the restoration of a riparian forest area in southern Brazil. The experiment was carried out in the Quarta Colônia State Park, and seedlings of nine native tree species, representing the Subtropical Seasonal Forest. Frost damage was measured using a visual damage scale based on the frost damage experienced in the winter of 2016. In addition, to evaluate the resilience of the species, height and diameter data were collected over the duration of the experiment. The species Solanum mauritianum was classified as frost resistant; therefore, we propose that it should be recommended for cultivation in regions where frost events usually occur. The other species studied, both the pioneers, S. terebinthifolius, Enterolobium contortisiliquum, Ceiba speciosa, and Inga marginata, as well as the secondary ones, Actinostemon concolor, Trichilia elegans, T. claussenii, and Eugenia rostrifolia, were influenced by the silvicultural management schemes used. Plants managed under intensive silviculture showed lower levels of frost damage and higher survival rates.

Quantifying the roles of seed dispersal, filtering, and climate on regional patterns of grassland biodiversity.

Seed dispersal and local filtering interactively govern community membership and scale up to shape regional vegetation patterns, but data revealing how and why particular species are excluded from specific communities in nature are scarce. This lack of data is a missing link between our theoretical understanding of how diversity patterns can form and how they actually form in nature, and it hampers our ability to predict community responses to climate change. Here, we compare seed, seedling, and adult plant communities at 12 grassland sites with different climates in southern Norway to examine how community membership is interactively shaped by seed dispersal and local filtering, and how this process varies with climate across sites. To do this, we divide species at each site into two groups: locally transient species, which occur as seeds but are rare or absent as adults (i.e., they arrive but are filtered out), and locally persistent species, which occur consistently as adults in annual vegetation surveys. We then ask how and why locally transient species are disfavored during community assembly. Our results led to four main conclusions: (1) the total numbers of seeds and species that arrived, but failed to establish locally persistent populations, rose with temperature, indicating an increase in the realized effects of local filtering on community assembly, as well as an increase in the number of species poised to rapidly colonize those warmer sites if local conditions change in their favor, (2) locally transient species were selectively filtered out during seedling emergence, but not during seedling establishment, (3) selective filtering was partly driven by species climate preferences, exemplified by the poor performance of seeds dispersing outside of their realized climate niches into colder and drier foreign climates, and (4) locally transient species had traits that likely made them better dispersers (i.e., smaller seeds) but poorer competitors for light (i.e., shorter statures and less persistent clonal connections) than locally persistent species, potentially explaining why these species arrived to new sites but did not establish locally persistent adult populations. Our study is the first to combine seed, seedling, and adult survey data across sites to rigorously characterize how seed dispersal and local filtering govern community membership and shape climate-associated vegetation patterns.

Influence of cultivation medium on growth of tissue cultured seedlings of Polygonatum cyrtonema / 中草药

Objective: To find a solution to the problems in the growth of tissue cultured seedlings of Polygonatum cyrtonema, such as low seedling survival rate, poor growth, and leaf disease. Method: In this study, tissue cultured seedlings of P. cyrtonema were used as testing plants. Two types of commercially-available cultivation medium commonly used in Fujian Province, as well as six types of cultivation medium mixed using peat soil, pearlite, roseite, sand, fungi residues and plant ash were used as the raw materials; Among them, a customized nutrient solution was added into the T5 and T7 cultivation media. Besides measuring the physicochemical properties of the cultivation media mentioned above, the study focused on the evaluation of their influence on the rate of grown-up seedlings, biological characteristics, growth biomass, strength index and incidence of leaf disease of P. cyrtonema. It also attempted to find the correlation between the physicochemical properties of the cultivation media and the biological characteristics, growth biomass, as well as the strength index of tissue cultured seedlings of P. cyrtonema. Results: The difference in the cultivation media had a great influence on the tissue cultured seedlings of P. cyrtonema in the rate of grown-up seedlings, biological characteristics, growth biomass, strength index and incidence of leaf disease. The difference in bulk density of the cultivation media had a notable negative correlation with the plant height of the tissue cultured seedlings of P. cyrtonema. The difference in the organic content of the cultivation media had a notable positive correlation with the fresh weight and dry weight of the tissue cultured seedlings of P. cyrtonema. Treated with the T5 cultivation medium we prepared, the tissue cultured seedlings of P. cyrtonema were in better growing condition in the rate of grown-up seedlings, morphological index, growth bomass, strength index, and no disease was found on the leaf. Conclusion: The prepared T5 was worth being widely used as the cultivation medium for growth of tissue cultured seedlings of P. cyrtonema.