Influenced Seedling Survival Research Articles

Ants may buffer the Janzen-Connell effect in a tropical forest in Southwest China.

Mutualistic symbioses between ants and plants are widespread in nature. Ants can deter unwanted pests and provide protection for plants in return for food or housing rewards. Using a long-term demographic dataset in a tropical seasonal rain forest in Southwest China, we found that associations with ants positively influenced seedling survival and adult growth, and also, species with extrafloral nectaries experienced weaker conspecific negative density dependence compared with species without extrafloral nectaries. Furthermore, we found strong evidence suggesting that species in our forest experienced conspecific density dependence, which we interpreted as heavy pest pressure that may drive the development of anti-pest symbioses such as the plant-ant relationship. Our findings suggest that ants and conspecific neighbors play important but inverse roles on plant survival and growth and that ants can buffer tree neighborhood interactions in this tropical forest.

Assessing the impact of abiotic and biotic factors on seedling survival in an African montane forest

Tree seedling dynamics underpin subsequent forest structure and diversity as different species/guilds respond variously to abiotic and biotic stresses. Thus, understanding differential seedling responses to stresses helps us to predict forest trajectories. Because forests vary in both environment and species composition, generalisations across tropical forests are difficult. Afromontane forests are important carbon stores, harbour high diversity and provide critical ecosystem services, yet they are vulnerable to climate change. Here, we investigate the importance of key abiotic and biotic factors on survival of seedling guilds along spatial and temporal scales in a montane forest in south-eastern Nigeria. We use data from 318 seedling plots censused every 3 months from 2017 to 2020 to identify seven key abiotic and four biotic factors influencing seedling survival. We used the Kaplan–Meier method to estimate the persistence time of 1,145 seedlings at community and guild levels. At the community level, newly recruited seedlings had a median survival time of 15 months and about 37% of the seedlings sampled where still alive after 24 months. Understory tree species survived significantly longer than the other growth form guilds and seedling survival did not differ across shade tolerance guilds. Conspecific adult density and steeper, more north facing slopes had a negative effect on tree seedlings survival. In addition, tree seedlings that recruited in October (end of wet season/beginning of dry) had lower survival probabilities compared to those that recruited in the other months. Except for initial height, seedling survival in lianas was not impacted by any of the abiotic and biotic variables tested. Our results suggest that under the current environment forest structure and diversity is changing, most noticeably lianas are increasing in abundance relative to trees.

Habitat heterogeneity and biotic interactions mediate climate influences on seedling survival in a temperate forest

Seedling stage has long been recognized as the bottleneck of forest regeneration, and the biotic and abiotic processes that dominate at seedling stage largely affect the dynamics of forest. Seedlings might be particularly vulnerable to climate stress, so elucidating the role of interannual climate variation in fostering community dynamics is crucial to understanding the response of forest to climate change. Using seedling survival data of 69 woody species collected for five consecutive years from a 25-ha permanent plot in a temperate deciduous forest, we identified the effects of biotic interactions and habitat factors on seedling survival, and examined how those effects changed over time. We found that interannual climate variations, followed by biotic interactions and habitat conditions, were the most significant predictors of seedling survival. Understory light showed a positive impact on seedling mortality, and seedling survival responded differently to soil and air temperature. Effects of conspecific neighbor density were significantly strengthened with the increase of maximum air temperature and vapor pressure deficits in the growing season, but were weakened by increased maximum soil temperature and precipitation in the non-growing season. Surprisingly, seedling survival was strongly correlated with interannual climate variability at all life stages, and the strength of the correlation increased with seedling age. In addition, the importance of biotic and abiotic factors on seedling survival differed significantly among species-trait groups. Thus, the neighborhood-mediated effects on mortality might be significantly contributing or even inverting the direct effects of varying abiotic conditions on seedling survival, and density-dependent effects could not be the only important factor influencing seedling survival at an early stage.

Planted seedling survival in a post-wildfire landscape: From experimental planting to predictive probabilistic surfaces

Across the southwestern United States, high-severity wildfire is causing increasingly large areas of tree mortality and removing the seed sources required for the natural regeneration of these formerly conifer-dominated landscapes. Planting tree seedlings can accelerate reforestation, but in the semi-arid southwestern US, the survival of planted conifer seedlings is typically low. Our research examined how post-fire planting success is influenced by climate, topographic, biotic, and microclimate factors. We present data on a seedling planting experiment within the footprint of the 2011 Las Conchas Fire in northern New Mexico. We planted 768 tree seedlings of four species: ponderosa pine (Pinus ponderosa), piñon (P. edulis), southwestern white pine (P. strobiformis), and Douglas-fir (Pseudotsuga menziesii) in an area burned at high-severity and densely populated by New Mexico locust (Robinia neomexicana) and other shrub species. We established experimental plots stratified by aspect, either northerly or southerly, and cover, either planted under New Mexico locust or in the open, and collected topographical and microclimate measurements over three years. Mean survival over the 3-year period for all species in all treatments was 20%. Using microclimate variables and site-level topographical indices in a piecewise exponential model, we first determined how these factors influenced seedling survival of four conifer tree species, finding that topographical indices describing incoming solar radiation, variables related to vapor pressure deficit, i.e., seasonal maximums, and presence of New Mexico locust increased hazard for all species while variables related to shade, moisture availability, and slope reduced hazard. Following our planting experiment, an additional 1145 ponderosa pine seedlings, planted by USFS, were surveyed for survival and the topographical indices at their locations were recorded. Adding these seedlings' survival data to our experimentally planted ponderosa pine seedlings, we used boosted regression tree models to determine survival probability for ponderosa pine as a product of topographical indices, then extrapolated these findings to the wider landscape, producing a spatial projection of probabilistic seedling survival as a function of readily available topographical data, with a mean AUC value of 0.63. Both sets of analyses highlight the importance of landscape heterogeneity in shaping microclimatic environments and affecting seedling survival in a predictable manner, with areas receiving less solar radiation and more moisture promoting seedling survival. Our results demonstrate that by using fine-scale microtopography that shapes microclimatic environments, future plantings can increase conifer tree seedling survival in high-severity post-wildfire landscapes.

Size- and environment-driven seedling survival and growth are mediated by leaf functional traits.

Ecologists usually find that plant demography (e.g. survival and growth) changes along with plant size and environmental gradients, which suggests the effects of ontogeny-related processes and abiotic filtering. However, the role of functional traits underlying the size– and environment–demography relationships is usually overlooked. By measuring individual-level leaf traits of more than 2700 seedlings in a temperate forest, we evaluated how seedling traits mediated the size– and environment–demography relationships. We found leaves were larger for taller seedlings; leaf economics traits were more conservative in taller seedlings and under high-light and low-elevation conditions. Structural equation modelling showed that a higher survival probability for taller seedlings was indirectly driven by their larger leaf area. Although taller seedlings had lower growth rates, larger and more resource-conservative leaves could promote the growth of these tall seedlings. Environmental variables did not influence seedling survival and growth directly but did influence growth indirectly by mediating trait variation. Finally, species-specific variation in traits along with size and environments was associated with the species-specific variation in seedling survival and growth. Our study suggests that not only plant ontogeny- and environment-related ecological processes, but functional traits are also important intermediary agents underlying plant size– and environment–demography relationships.

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.

Resource competition, not facilitation, structures gravel beach plant communities

AbstractQuestionsHow are plant–plant interactions mediated by environmental factors to influence plant community structure on gravel beaches?LocationTwo coastal gravel beaches on the eastern coast of New Zealand.MethodsWe surveyed plant co‐occurrence patterns on the beaches and performed plant addition experiments, varying nutrients, water, and presence of potential nurse plants. We used C‐score analysis to test whether observed individual and species co‐occurrence patterns deviated from random expectation. Generalised linear modelling of survival within the experiments tested the importance of potential nurse plants vs both resource‐ and non‐resource‐based stress.ResultsDespite the harsh conditions, species co‐occurred less frequently than expected if distributions were random. The presence of adult nurse plants had a negative, rather than facilitative effect on growth and survival of planted shrub seedlings. Abiotic factors also influenced seedling survival, although responses were species‐specific.ConclusionsWe found no evidence that facilitation plays a role in structuring plant communities in the highly stressed environment of New Zealand gravel beaches. Rather, our results support the prediction that resource competition is the dominant factor in determining community structure in highly stressed environments and is inconsistent with the stress gradient hypothesis.

Non-native earthworms alter the assembly of a meadow plant community

Non-native earthworms can alter ecosystems by modifying soil structure, depredating seeds and seedlings, and consuming soil organic matter, yet the initial responses of plant communities to earthworm invasions remain poorly understood. We assessed the effect of non-native earthworms on seedling survival during germination and after establishment using six native and six non-native plant species grown from seed in single- and multi-species experimental mesocosms. We examined the extent to which earthworms (1) influenced seedling survival, (2) selectively depredated native versus non-native plants, (3) impacted establishment based on seed size and/or root morphology, and (4) shaped community assembly. The effect of earthworms on seedling survival varied temporally and among species but inconsistently with respect to species origin. Differences in seed/seedling survival translated to changes in community assembly. Earthworms tended to reduce species abundance, richness, evenness, and diversity in multi-species mesocosms and led to the divergence of communities by treatment. In general, species with large seeds and fibrous roots dominated communities with earthworms present, whereas species with small seeds and taproots only persisted in multi-species mesocosms without earthworms. Our findings suggest that earthworms act as ecological filters in the early stages of invasion to shape community composition based on plant morphological traits.

Seedling survival declines with increasing conspecific density in a common temperate tree

AbstractFeedbacks between plants and their soil microbial communities often drive negative density dependence in rare, tropical tree species, but their importance to common, temperate trees remains unclear. Additionally, whether negative density dependence is driven by natural enemies (e.g., soil pathogens) or by high densities of seedlings has rarely been assessed. Density dependence may also depend on seedling size, as smaller and/or younger seedlings may be more susceptible to mortality agents. We monitored seedlings of Quercus rubra, a common, canopy‐dominant temperate tree, to investigate how the density of neighboring adults and seedlings influenced their survival over two years. We assessed how the soil microbial community influenced seedling survival by growing seedlings in a glasshouse inoculated with soil collected from beneath conspecific and heterospecific mature trees. In the field, seedling survival was lower in areas with high densities of mature conspecifics but was unrelated to either conspecific or heterospecific seedling density. Smaller seedlings were also more sensitive than larger seedlings to neighboring adult conspecifics. In the glasshouse, seedlings grown with soil from beneath a conspecific adult had a higher mortality rate than seedlings grown with soil from beneath heterospecific adults or sterilized soil, suggesting that soil microbial communities drive the patterns of mortality in the field. These results illustrate the importance of negative density‐dependent feedbacks resulting from the soil microbial community in a common and ecologically important temperate tree species.

Bacterial communities differ between plant species and soil type, and differentially influence seedling establishment on serpentine soils

Root-associated microbial communities influence plant phenotype, growth and local abundance, yet the factors that structure these microbial communities are still poorly understood. California landscapes contain serpentine soils, which are nutrient-poor and high in heavy metals, and distinct from neighboring soils making them ideal for studying the factors that structure root microbiomes and their functions. Here, we surveyed the rhizoplane of serpentine-indifferent plants, which grow on and off serpentine soil, to determine the relative influence of plant identity and soil chemistry on rhizoplane microbial community structure using 16S rRNA metabarcoding. Additionally, we experimentally examined if serpentine vs. non-serpentine microorganisms differentially affected plant growth in serpentine soil. Rhizoplane bacterial communities differed among plant species, soil types, and the interaction between them in both the field and experimental soils. In the experiment, soil microbial community source influenced seedling survival, but plant growth phenotypes were largely invariant to microbial community with a few exceptions. Rhizosplane bacterial species composition differed between plant species and soil types, and Amplicon Sequence Variants (ASVs) from the phyla Acidobacteria and Proteobacteria (Genus: Microvirga) were characteristic of serpentine soils. While soil microbial community composition influenced seedling survival in the current study, further study is required to disentangle the role of microbial associations and plant tolerance to serpentine.

Effects of climate warming and prolonged snow cover on phenology of the early life history stages of four alpine herbs on the southeastern Tibetan Plateau.

Much research has focused on plant responses to ongoing climate change, but there is relatively little information about how climate change will affect the early plant life history stages. Understanding how global warming and changes in winter snow pattern will affect seed germination and seedling establishment is crucial for predicting future alpine population and vegetation dynamics. In a 2-year study, we tested how warming and alteration in the snowmelt regime, both in isolation and combination, influence seedling emergence phenology, first-year growth, biomass allocation, and survival of four native alpine perennial herbs on the southeastern Tibetan Plateau. Warming promoted seedling emergence phenology of all four species and biomass per plant of two species but reduced seedling survival of three species. Prolonged snow cover partly mediated the affects of warming on Primula alpicola (survival and biomass), Pedicularis fletcheri (phenology, biomass, and root:shoot ratio) and Meconopsis integrifolia (survival). For the narrowly distributed species M. racemosa, seedling growth was additively decreased by warming and prolonged snow cover. Both warming and alteration of the snow cover regime can influence plant recruitment by affecting seedling phenology, growth, and survival, and the effects are largely species-specific. Thus, climate change is likely to affect population dynamics and community structure of the alpine ecosystem. This is the first experimental demonstration of the phenological advancement of seedling emergence in the field by simulated climate warming.

Species wood density and the location of planted seedlings drive early‐stage seedling survival during tropical forest restoration

Abstract The success of restoration projects is known to vary widely, with outcomes relating to numerous biotic and abiotic factors. Though many studies have examined the factors associated with long‐term restoration success, few have examined which factors impact the establishment of restoration plantings. In Australia's Wet Tropics, we used a large replicated restoration experiment to assess seedling survival for 24 native rainforest species commonly used in local restoration efforts. The experiment allowed for a rigorous assessment of the effects of species functional traits, planting conditions, and landscape‐ and local‐scale biotic and abiotic factors on seedling survival. This study reports on seedling survival between three different time periods of 0–4, 4–9 and 9–31 months post planting. The probability of seedling survival was influenced by multiple factors, varying in importance over time. Across the whole study period, seedlings with high wood density and which were planted closer to intact forest consistently displayed the highest probabilities of survival. Transient factors affecting seedling survival across the three time periods included plot aspect (0–4 months only), the identity of the planter and slope (4–9 and 9–31 months). Overall, species survival did not differ between the low (6 species) and high (24 species) diversity treatments, but was significantly lower in monocultures of Flindersia brayleyana by the end of the study. We demonstrate that early‐stage seedling survival depends on species wood density and planting location. Our results support the use of species with more conservative growth strategies when limited funds are available for follow‐up plantings. High wood density species had significantly higher survival than lower wood density, early successional species typically used in rainforest restoration plantings. Synthesis and applications. Our study highlights the importance of wood density and landscape structure to the initial survival of rainforest plantings. Factors influencing seedling survival shifted over time but, most importantly, our results highlight that, when planting into abandoned pastures, it may be preferable to select species with higher wood densities to maximize survival during the crucial early stages of establishment and growth.

Waterlogging Influence on Roughstalk Bluegrass (Poa trivialis) and Tall Fescue Germination

Oregon’s Willamette Valley is the major cool-season, grass-seed-production area in the world. Roughstalk bluegrass (RB) is a weed in waterlogged, grass-seed-crop fields. Growth chamber and greenhouse studies were conducted to determine the influence of waterlogging on the germination and establishment of RB and tall fescue (TF). Oxygen deficiency resulted in a germination delay in both species, but was greater for TF. Oxygen deficiency at 20 and 30 C was greater for TF compared to RB. Simulated waterlogging for 28 d reduced aboveground biomass more for RB (58%) than for TF (46%), but did not influence seedling survival. Compared to TF, the influence of waterlogging on RB was greater during early establishment. These responses may help RB maintain its germination rate while reducing the damage caused by the accumulation of toxic fermentation-metabolites during waterlogging which benefits RB in competition with TF, especially under high temperatures.

Drought versus heat: What's the major constraint on Mediterranean green roof plants?

Green roofs are gaining momentum in the arid and semi-arid regions due to their multiple benefits as compared with conventional roofs. One of the most critical steps in green roof installation is the selection of drought and heat tolerant species that can thrive under extreme microclimate conditions. We monitored the water status, growth and survival of 11 drought-adapted shrub species grown on shallow green roof modules (10 and 13cm deep substrate) and analyzed traits enabling plants to cope with drought (symplastic and apoplastic resistance) and heat stress (root membrane stability). The physiological traits conferring efficiency/safety to the water transport system under severe drought influenced plant water status and represent good predictors of both plant water use and growth rates over green roofs. Moreover, our data suggest that high substrate temperature represents a stress factor affecting plant survival to a larger extent than drought per se. In fact, the major cause influencing seedling survival on shallow substrates was the species-specific root resistance to heat, a single and easy measurable trait that should be integrated into the methodological framework for screening and selection of suitable shrub species for roof greening in the Mediterranean.

Effects of light availability on morphology, growth and biomass allocation of Fagus sylvatica and Quercus robur seedlings

The survival, morphological, and growth responses of European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) seedlings to different light intensities, from full sunlight to heavy shade, were studied over two growing seasons in a shadehouse experiment. Although shade treatments significantly affected seedling growth, they did not influence seedling survival. Both growth and biomass increased as light intensity increased. Diameter growth of oak seedlings was higher than that of beech. Beech and oak seedlings showed typical acclimation to shade, including greater specific leaf area and height to diameter ratios, and lower leaf thickness and root:shoot ratios with increasing shade. Beech seedlings exhibited greater specific leaf area, and lower leaf thickness and root:shoot ratios than oak seedlings. In spite of the greater growth at full sunlight, the results from this study suggest that beech and oak seedlings would have high survival rates and would acclimate well if underplanted below overstories that reduce the available light to as low as 28% of full light.

Competitive resistance of a native shrubland to invasion by the alien invasive tree species, Acacia cyclops

Biotic resistance is infrequently considered when investigating the potential spread of invasive woody species. In this study, we determined whether native vegetation of Mediterranean-climate shrublands in the Cape Floristic Region of South Africa constrains woody invasive seedling establishment and performance through above- and below-ground competition for resources. Seedlings of the invasive tree, Acacia cyclops, were transplanted into native shrubland vegetation in a three-way factorial design where light availability, below-ground root competition and soil nutrient availability were manipulated. Survival, growth, biomass allocation, water use efficiency, foliar nutrients and δ15N were assessed after ca. 7 months. Control seedlings had a ca. 20 % survival, which increased to a maximum of ca. 80 % depending on treatments. Root exclusion tubes increased seedling survival and heights by ca. 1.6-fold and total biomass by ca. 4.8-fold. In contrast, above-ground availability of light did not influence seedling survival or height, although seedlings grown under the lowest light availability (0–20 %) had biomass ca. threefold lower than seedlings grown under the highest light availability (80–100 %). Competition from native vegetation, particularly below-ground competition, impedes survival, growth and biomass accumulation of these woody invasives, presumably constraining invasion spread. We conclude that the maintenance of intact, native ecosystems is important in limiting woody invasion spread and also suggest that biotic components should be included in invasion distribution and spread models in order to aid in optimization of scarce management resources.

Invasions across secondary forest successional stages: effects of local plant community, soil, litter, and herbivory on Hovenia dulcis seed germination and seedling establishment

Species abilities for seed germination and seedling survival under different situations are good predictors of their capacity to colonize a broad range of habitats. Biotic conditions related to understory cover, and abiotic factors such as litter thickness and soil moisture can be determinants of plant establishment. We evaluated seed germination, seedling survival, and growth of the invasive tree Hovenia dulcis under experimental field conditions in three successional stages (open, semi-open, and closed vegetation) of a fragmented seasonal deciduous forest in southern Brazil. Our hypotheses were that H. dulcis seed germination, seedling survival, and seedling growth decrease along the successional gradient, that these factors are positively affected by soil moisture and percentage of bare soil, and negatively affected by understory cover and litter thickness. We also tested the hypothesis that herbivory on H. dulcis would decrease along the successional gradient. Our main finding was that H. dulcis can germinate and establish along all forest successional stages because it is shade-tolerant. Abiotic factors were more important than biotic factors for seed germination. Soil moisture positively affected seed germination while litter thickness negatively influenced seed germination. Percentage of bare soil negatively influenced seedling survival. Germination rates were higher in closed vegetation, whereas seedling survival was higher in semi-open vegetation, and growth rates were higher in open vegetation. There was no difference in herbivory among successional stages. The results of our study show that intermediate forest succession stages congregate the most favorable conditions for H. dulcis establishment, likely making them more susceptible to invasion.

Seedling Recruitment and Establishment ofLupinus perennisin a Mixed-Management Landscape

Ecological disturbances structure plant communities. In areas where reintroducing natural disturbances is unfeasible, land managers use artificial disturbances, such as fire and mowing, to simulate natural disturbances. However, prescribed fire and mowing can promote or inhibit seedling survival in plant populations. Lupinus perennis (the wild blue lupine) is a potentially threatened species commonly subjected to rotations of burning and mowing treatments to restore habitat for endangered butterflies (e.g., Karner blue, Lycaeides melissa sameulis). While L. perennis adults respond favorably to these management techniques, it is unknown how these variable management programs affect natural seedling recruitment and establishment. We quantified natural L. perennis seedling survival in seven managed remnant oak savannas in Northwest Ohio in 2007 and 2008. To evaluate the roles of management history and environmental factors on recruitment, we obtained burning and mowing management records for each savanna, measured environmental variables at each seedling, and assessed their relationships with seedling mortality. Seedling survival varied among the savannas and increased with greater fern and grass stems, moss cover, soil moisture, and initial size, but was reduced by increased oak saplings, light levels, and topographic wetness. Site elevation and initial seedling size affected the sizes of the juvenile plants. Management activities did not directly influence seedling survival or density, but the number of fires and total management activities at a site were positively correlated with oak saplings, suggesting current management practices may indirectly reduce lupine survival. Future management strategies may increase recruitment by focusing on the restoration of multiple species that are important components of the lupine regeneration niche.

Successional Distance between the Source and Recipient Influence Seed Germination and Seedling Survival during Surface Soil Replacement in SW China

Adding propagules (source) to a degraded site (recipient) is a common way of manipulating secondary succession to restore diversity and services formerly provided by forests. However, heretofore no study has considered the effect of “successional distance” between source and recipient site. Four sites in the Shilin karst area of SW China were treated as different states along a secondary successional sere: grass, shrub, young secondary forest, and primary forest. Ten 1 m ×1m soil quadrats in the grass, shrub and young forest sites were replaced with 10 cm deep soil sources from corresponding later successional stage(s) in January 2009. Woody plant seed germination was monitored in the first year and seedling survival was monitored until the end of the second year. At the end of 2010, 2097 seeds of woody plants belonging to 45 taxa had germinated, and 3.9% of the seedlings and 7.8% of the species survived. Germination of most species was sensitive to ambient light (red, far-red, R:FR ratios, photosynthetically active radiation). Soil source and recipient site had a significant effect on the total number of seeds and number of species that germinated, and on the percentage of seedlings that survived through the end of the second year. Closer successional stages between recipient site and soil source had higher seed germination and seedling-survival percentages. However, a transition threshold exists in the young forest state, where seeds can germinate but not survive the second year. Our results, although based on an unreplicated chronosequence, suggest that successional distance between soil sources and recipient sites affect forest recruitment and restoration in degraded karst of SW China.

Rapid ontogenetic niche expansions in invasive Chinese tallow tree permit establishment in unfavourable but variable environments and can be exploited to streamline restoration

Summary Reinvasion pressure is the rate of new exotic recruitment following mature exotic removal and it can vary broadly among similarly invaded habitats. Reinvasion pressure drives restoration outcomes and costs but is difficult to predict and poorly understood. Chinese tallow tree Triadica sebifera is a major invader demonstrating broad variation in average reinvasion pressure. We hypothesize this variation arises from differences in moisture regimes among habitats, which drive differences in Triadica recruitment but are masked because Triadica exhibits ontogenetic niche expansions (increases in niche breadth during development) that enable dominance in habitats where average recruitment success is low. We began testing this hypothesis by quantifying Triadica's capacity for ontogenetic moisture niche expansions. We performed greenhouse experiments examining how soil moisture affects germination likelihood and timing and how soil moisture and seedling age influenced seedling survival and performance, plus a field experiment quantifying survival and performance of differently aged seedlings within a restoration site that has exhibited low average reinvasion pressure. Moisture requirements for germination were the most constrained of any life stage. No germination occurred in saturated or flooded soils despite high seedling survival in comparable conditions. Germination timing varied among suitable moisture treatments. Seedling survival increased rapidly with age across moisture treatments and in the field. Above‐ground biomass increased with age; tissue‐specific performance metrics also increased but reflected seed provisioning, age‐specific carbon allocation preferences, or tissue shedding for survival. Crucial moisture*age interactions that signify ontogenetic niche expansions were significant for all survival metrics and all but one performance metric. Survival and performance were generally highest in intermediate moistures, modestly reduced in saturated conditions and lowest in water‐limited conditions. Synthesis and applications. Our results show Triadica exhibits rapid ontogenetic moisture niche expansions, which could decouple mature Triadica density and average reinvasion pressure. Therefore, density is an unreliable predictor of reinvasion but is commonly used to guide Triadica management, and cryptic opportunities exist for inexpensive and straightforward restorations. Reliable moisture niche‐based estimates of Triadica's average reinvasion pressure are feasible and may improve restoration efficacy and efficiency by informing site selection and optimal management strategies.