Acorn Production Research Articles

Pollen source affects acorn production in pedunculate oak (Quercus robur L.)

Acorn production in oaks (Quercus spp.) shows considerable inter-annual variation, known as masting. The effects of pollen sourced from trees within or outside the stand on acorn production were investigated in pedunculate oak (Quercus robur L.) in an ancient mixed woodland during two moderate masting years. Comparisons were made between natural pollination, hand pollinations with out-of-stand pollen, in-stand pollen or a 1:1 combination of the two pollen sources, and for bagged flowers left unpollinated. After all treatments, > 85% of the flowers or developing acorns were aborted between May and August of both years. When flowers were protected with pollen bags and no pollen added, no acorns were produced. In contrast, hand pollination with out-of-stand pollen produced the most acorns both years and significantly more than within-stand pollen or natural pollination in 2022. Hand pollination with out-of-stand or within-stand pollen provided significantly more acorns than natural pollination in 2023. In 2022, hand pollination with a 1:1 mixture of out-of-stand and within-stand pollen yielded an intermediate number of mature acorns between those for the out-of-stand and within-stand pollination treatments. The study provides clear evidence of maternal choice during acorn development in pedunculate oak and of the benefits of pollen supplementation. It also confirms that pedunculate oak is a fruit-maturation masting species; abortion of pollinated flowers and immature acorns determines a mast year (rather than the number of flowers produced) at this site.

Natural regeneration of cork oak forests under climate change: a case study in Portugal

The sustainability of forest species is directly related to the success of stand regeneration. Assuring success is particularly critical in stands where perpetuity relies on natural regeneration, as is often the case with cork oak forests. However, 59% of the stand in Portugal have no natural regeneration, and climate change could further worsen the sustainability of the system. The study summarizes the factors that affect the natural regeneration of cork oak (Quercus suber L.) based on current knowledge and presents a case study on a forest in Northeast Portugal, where the natural regeneration of Quercus suber under the effect of climate change have been monitored and analyzed. The present work focuses on the effect of stand density, i.e., tree cover, on the production of acorns, the establishment and survival of seedlings, and the impact of the summer season on seedling mortality. The monitoring was carried out in February, June, September 2022, and January 2023 in two stands with distinct stand canopy cover, when the region was under extreme drought. Data analysis was performed using the analysis of variance for repeated measures and the Mann–Whitney-Wilcoxon test. The study showed that cork oak regeneration is influenced by stand density, which promoted the establishment success and survival of natural regeneration in a period of reduced precipitation, despite possible competition for water resources. The mean number of seedlings differed significantly between the two stands. However, there were no significant differences in the mean number of seedlings throughout the field measurements. Additionally, the percentage of dead seedlings was low even after the summer season (9.5% of the total seedlings) in the denser stand. These results indicate that high canopy cover can have a protective effect for extreme climatic events and should be considered in forestry management to promote regeneration of the cork oak forests.

Intra-annual variation in oak masting affects wildlife feeding behavior

Abstract Oaks (Quercus spp.) provide an important food source for many wildlife species throughout the fall and winter. Most research evaluating oak masting patterns and the subsequent behavioral responses of wildlife focuses on the annual temporal scale. However, patterns in masting at the seasonal temporal scale may be important for wildlife behavior. We designed a study quantifying seasonal oak masting patterns of 3 oak species (water oak, Q. nigra; laurel oak, Q. laurifolia; and swamp chestnut oak, Q. michauxii) and linking those patterns to visitation and feeding behavior of 3 primary consumers (white-tailed deer, Odocoileus virginianus; gray squirrel, Sciurus carolinensis; and raccoon, Procyon lotor). We used seed traps to monitor the seasonal masting pattern of 205 trees in the fall of 2021 and 2022 and used camera traps concurrently to monitor wildlife behavior associated with a subset of 30 trees. Seasonal masting patterns differed between oak species both within a season and across years, and the timing of mast varied within oak species across years. White-tailed deer tended to visit swamp chestnut oak as the number of acorns increased and consumed their acorns. Gray squirrels and raccoons tended to visit laurel oak and consume water oak acorns with gray squirrels being more likely to consume as the number of acorns increased. Our results indicate that evaluating acorn production at multiple temporal scales may be necessary to fully understand oak masting relationships with wildlife. Furthermore, differences in wildlife behavior based on oak species may have important implications for oak regeneration.

Carbon dioxide enrichment affected flower numbers transiently and increased successful post-pollination development stably but without altering final acorn production in mature pedunculate oak (Quercus robur L.)

Acorn production in oak (Quercus spp.) shows considerable inter-annual variation, known as masting, which provides a natural defence against seed predators but a highly-variable supply of acorns for uses such as in commercial tree planting each year. Anthropogenic emissions of greenhouse gases have been very widely reported to influence plant growth and seed or fruit size and quantity via the ‘fertilisation effect’ that leads to enhanced photosynthesis. To examine if acorn production in mature woodland communities will be affected by further increase in CO2, the contents of litter traps from a Free Air Carbon Enrichment (FACE) experiment in deciduous woodland in central England were analysed for numbers of flowers and acorns of pedunculate oak (Quercus robur L.) at different stages of development and their predation levels under ambient and elevated CO2 concentrations. Inter-annual variation in acorn numbers was considerable and cyclical between 2015 and 2021, with the greatest numbers of mature acorns in 2015, 2017 and 2020 but almost none in 2018. The numbers of flowers, enlarged cups, immature acorns, empty acorn cups, and galls in the litter traps also varied amongst years; comparatively high numbers of enlarged cups were recorded in 2018, suggesting Q. robur at this site is a fruit maturation masting species (i.e., the extent of abortion of pollinated flowers during acorn development affects mature acorn numbers greatly). Raising the atmospheric CO2 concentration by 150 μL L−1, from early 2017, increased the numbers of immature acorns, and all acorn evidence (empty cups + immature acorns + mature acorns) detected in the litter traps compared to ambient controls by 2021, but did not consistently affect the numbers of flowers, enlarged cups, empty cups, or mature acorns. The number of flowers in the elevated CO2 plots’ litter traps was greater in 2018 than 2017, one year after CO2 enrichment began, whereas numbers declined in ambient plots. Enrichment with CO2 also increased the number of oak knopper galls (Andricus quercuscalicis Burgsdorf). We conclude that elevated CO2 increased the occurrence of acorns developing from flowers, but the putative benefit to mature acorn numbers may have been hidden by excessive pre- and/or post-dispersal predation. There was no evidence that elevated CO2 altered masting behaviour.

Evergreen forests on the Korean Peninsula faced a new threat: Schizomyia castanopsisae (Jat-bam-na-mu-hok-pa-ri) inducing galls on reproductive organs of Castanopsis sieboldii in the Yokjido Island Natural Monument Forest

Unnoticed and silently, a certain midge has emerged that could pose a threat to the evergreen forests on the Korean Peninsula and the associated island ecosystems. We report the discovery of an unrecorded species on the Korean Peninsula, identified as Schizomyia castanopsisae Elsayed & Tokuda, 2018 (Diptera: Cecidomyiidae). This previously unrecorded gall midge species induces galls on a reproductive organ of Castanopsis sieboldii, specifically the inflorescences, and was found in the natural monument forest on Yokjido Island. A total of 40 larvae were collected from 8 inflorescence galls, each obtained from individual hosts within the forest. Morphological examinations and mitochondrial DNA cytochrome oxidase subunit I (COI) region sequencing were conducted for each specimen, confirming the identification of the gall inducer as S. castanopsisae. The COI sequences from the 40 specimens collected on Yokjido Island were identical, showing a 99.8% match with individuals from Kyushu, Japan. Additionally, a maximum likelihood tree analysis revealed a sister relationship between Yokjido Island and Kyushu individuals. Considering the tropical nature of gall midge species, it suggests recent northward migration from Kyushu to Yokjido Island. This species not only significantly reduces acorn production but also has the potential to negatively impact organisms associated with acorns. Drawing from cases in Japan, this species has the potential to rapidly dominate evergreen broad-leaved forests on numerous islands in the Korean Peninsula. Therefore, urgent additional research on aspects such as natural enemies of this species, its dispersal mechanisms, and other relevant factors is necessary. We also investigated the distribution of trees with inflorescences gall-induced by S. castanopsisae in the Yokjido Island Natural Monument Forest. The occurrence frequency of these galls is estimated to be approximately 10 percent.

Modified SEIB-DGVM enables simulation of masting in a temperate forest

Masting, the periodical mass production of seeds, affects forest ecosystems and food web dynamics. However, masting is not included in process-based models of forest dynamics which makes it difficult to predict changes in masting characteristics owing to climate change. We developed a masting model using the Spatially Explicit Individual Based-Dynamic Global Vegetation Model and validated it in a temperate forest containing Quercus crispula. Four models were devised using combinations of three major masting theories: resource budget, pollen limitation, and weather pattern hypotheses. The models simulated masting by modifying the reproduction of a novel plant functional type by parameterising the resource allocation to masting, the threshold limit for flowering, and the cost of acorn production. The results indicate that masting affected tree mortality; when trees allocated too many resources to masting and the threshold limit for flowering was low, tree mortality of the masting group increased. The model based on the resource budget and pollen limitation hypotheses corresponded most closely to observations, particularly under parameter combinations involving low resource allocation to masting and cost of acorn production. The models can be adapted to other species and for global applications, such as simulating the effects of climate change on masting and mitigating negative impacts on forest ecosystems and human–wildlife interactions.

Fertility Variation and Effective Population Size across Varying Acorn Yields in Turkey Oak (Quercus cerris L.): Implications for Seed Source Management

This research examines the impact of varied acorn yields on the effective population size of Turkey oak (Quercus cerris L.) as assessed through the fertility averages of zygotic parents. We selected two distinct populations from the species’ natural habitats based on their good and poor acorn production rates to investigate acorn production, growth attributes, and their interrelationships over three years of production and two years of growth data. Results showed that the population with good acorn production exhibited greater growth attributes and acorn yields compared to the poor acorn production population. Acorn production had lower coefficients of variation compared to growth attributes. Fertility variation in both populations was moderate, with a decrease in the effective number of parents from the population with abundant acorn production to the one with limited acorn production. The presence of mixed seeds from diverse populations had a detrimental impact on fertility variation and related metrics. Nonetheless, this study suggests that regions with limited acorn production still have the potential for natural regeneration due to their larger effective population size when coupled with appropriate forestry practices such as selective acorn harvesting to enhance genetic diversity. These findings emphasize the importance of accounting for fertility variation in the selection and management of seed sources, even within the context of a limited area and three years of data. Further research should be conducted in larger populations and over longer periods to draw more comprehensive conclusions.

Acorn production of pedunculate oak in northeast of Ukraine

Abstract We analysed the quantity and quality of Quercus robur L. acorns after years with a very poor yield under the canopy of natural oak stands of various compositions, ages and stock densities in the northeastern part of Ukraine. We determined the mass of 1,000 healthy and damaged acorns of the current year. The levels of variability were estimated for the number and mass of acorns under the canopy of the studied stands. The dependences of the number of acorns on the age of oak stands and their stock density were studied. The total number of acorns under the canopy of natural oak stands was 9,900–19,000 seeds per hectare with a total mass of 26.8–54.1 kg per hectare in 2020 and 8,600–17,200 seeds per hectare with a total mass of 22.7–48.4 kg per hectare in 2021. The proportion of damaged acorns was about 70% both in 2020 and 2021. The largest number of acorns was concentrated under healthy trees (without signs of decline) that had a well-developed crown and, therefore, received more sunlight and heat. The identified quantitative and qualitative estimates and acorn spreading pattern need to be considered when selecting sites for further natural seed regeneration in old-aged oak stands.

Modification of Acorn Starch Structure and Properties by High Hydrostatic Pressure.

Despite being rich in starch, over half of acorn production is undervalued. High hydrostatic pressure was used to modify the properties of Q. pyrenaica (0.1 and 460 MPa for 20 min) and Q. robur (0.1 and 333 MPa for 17.4 min) acorn starches to obtain high-valued ingredients. Pressure significantly altered the span distribution and heterogeneity of the acorn starch granules depending on the species, but their morphology was unaffected. Pressurization increased the amylose/amylopectin ratio and damaged starch contents, but the effect was more prominent in Q. pyrenaica than in Q. robur. However, the polymorphism, relative crystallinity, gelatinization temperatures, and enthalpies were preserved. The pressure effect on the starch properties depended on the property and species. The solubility, swelling power, and acorn gels' resistance towards deformation for both species decreased after pressurization. For Q. pyrenaica starch, the in vitro digestibility increased, but the pseudoplastic behavior decreased after pressurization. No differences were seen for Q. robur. Regarding the commercial starch, acorn starches had lower gelatinization temperatures and enthalpies, lower in vitro digestibility, lower resistance towards deformation, superior pseudoplastic behavior, and overall higher solubility and swelling power until 80 °C. This encourages the usage of acorn starches as a new food ingredient.

Early Responses to Crown Modification of California Black Oak Sprouts Initiated by High-Severity Wildfire

Abstract Hardwoods resprouting after wildfire or cutting develop as multistemmed clumps that gradually self-thin over time. There is increasing interest in thinning of sprouting species to accelerate the formation of tree characteristics important to indigenous cultural practices and wildlife such as large-diameter stems, large branches, broad crowns, and acorn production. We compared responses to three thinning treatments applied to black oak (Quercus kelloggii) resprouting after high-severity wildfire throughout northern California, USA. Basal area increment of the dominant stem was greatest after only one stem was retained, intermediate after three stems were retained, and lowest within unthinned oaks. Unwanted resprouting in response to the thinning was minimized by retaining three stems. Acorn production tended to increase as time elapsed since the fire (i.e., larger, older sprouts) but varied among sites and was noted as early as six years after fire at one site. More study is needed to test for the effects of thinning timing and intensity on the acceleration of acorn production as well as stem, branch, and crown size development over time.

Acorn production, climate, and tree-ring growth of five oak species in southern Appalachian forests

Oak (Quercus) are a dominant and important tree genus in the Central Hardwood Region (USA) due to their commercial timber value, and food value of their protein-rich seed – acorns – to wildlife. Acorn production is characteristic of masting, with highly variable crop sizes that are synchronized within populations, but with consideration variation among individual trees. Critical to acorn masting studies are longitudinal datasets, which are often difficult to maintain due to a host of constraints. One possible approach to extending mast datasets involves the use of dendrochronology, where tree-ring-width variability serves as a proxy for annual acorn production. In this study, we addressed the future utility of mast reconstructions by examining relationships between acorn production, climate, and tree-ring data from five common oak species in southern Appalachian hardwood forests (Bent Creek Experimental Forest). We found little evidence to suggest that acorn production influences seasonally resolved tree-ring data, even when we considered early and latewood growth separately, or when we analyzed trees with substantially higher overall investment in acorn production (i.e., super producers). Monthly climate (temperature, precipitation) correlated to acorn production was strongest when lagged, which could indicate weather conditions were more important for phases of flower production and fertilization than acorn maturation. However, relationships were relatively weak, indicating limited potential for the forecasting of acorn crops, or for reconstruction methods that combine observed weather data and tree-ring responses to masting. Overall, our findings provide some support for the role of resource dynamics in regulating masting in oaks, but relationships between radial growth and acorn production are not sufficiently strong, at least in this location, to permit tree-ring based reconstruction of masting in these oak species.

Environmental factors can influence spatial aggregation and acorn production in the endemic and endangered oak Quercus brandegeei in Mexico

Background and study species: The endangered oak Quercus brandegeei Goldman, endemic to Baja California Sur, Mexico, is threatened because of its relictual distribution restricted to ephemeral riverbeds, declining populations, and a lack of seedling regeneration. Although there is evidence of viable acorn production, no seedlings or saplings have been found across the range of occurrence for this species. 
 Hypothesis: We tested for spatial aggregation and factors determining acorn production, hypothesizing that Q. brandegeei trees would be less distant from one another in regions with higher precipitation and that tree attributes and climatic variables would co-determine acorn presence.
 Study site and dates: Baja California Sur, Mexico, 2016-2017
 Methods: We conducted a Ripley’s K analysis to determine each population’s spatial pattern (random, uniform, clumped) across 12 populations and a total of 194 individuals. To find the impact of environmental factors on acorn production we conducted a series of generalized linear models on eight climatic variables. 
 Results: Ripley’s K analysis revealed that Q. brandegeei is a highly clumped species, with the highest rate of aggregation occurring within 0-25 meters. Region but not climatic cues were found to be important determinants of presence of acorns. 
 Conclusions: High aggregation in clumps and low evidence of acorn production in some populations suggests that there is a niche attrition for this species, which is confined to very specific microsites along ephemeral riverbeds. Suitable recruitment areas could be reduced even further under the hotter and drier climate predicted for the region.

Unravelling the influence of annual weather conditions and Mediterranean habitat types on acorn production, availability and predation

Seed production and survival are critical steps in the life cycle of plants, and could become bottlenecks for plant regeneration in case of failure. During regeneration many factors, both abiotic and biotic, intervene and interact with each other. After dispersal, environmental variation affects the success of the plant population, so seedling recruitment can display spatial variability. However, few studies of seed production and availability cover a range of habitat conditions (e.g. mature, transitional and post-fire habitats), which makes it difficult to evaluate the potential of site-production relationships. We study how the heterogeneity of habitat structure and composition affects the phenology, production and availability of acorns, mainly holm oak, in a Mediterranean Natural Park. Our results show that meteorological variables determine the phenology of acorn fall. Habitat types present temporal mismatches in falls since, for example, shrublands required a longer period of time for all seeds to fall. Furthermore, habitats with greater tree density and low understory complexity had higher production but smaller acorns. Lower densities promote higher acorn volume (seedling size) as a consequence of less intraspecific competition and more reserves for germination. The proportion of viable acorns available on the ground also decreased substantially in winter, when the proportion of infested acorns increase because the selective consumption of sound acorns by predators. Acorns from mixed forests and shrublands had less pre-dispersal predation by arthropods and post-dispersal predation by wild boar as a result of oak isolation and understory complexity. Conversely, rodents are more abundant in shrublands, where they find a greater diversity of anti-predator refuges and large nutritious acorns available in autumn and winter. Understanding the reproductive constraints imposed by time and space allows us to infer the consequences of environmental changes on population recruitment and persistence. We thus show that habitats with a high density of oak trees, less plant diversity and understory cover had a greater prevalence of infested acorns, thereby reducing recruitment viability. These habitats also had more available acorns on the ground for seed predators. Therefore, habitat type is an important factor affecting acorn production and should be taken into account in future studies.

Periodical Cicada Emergences Affect Masting Behavior of Oaks.

AbstractOaks (Quercus spp.) are masting species exhibiting highly variable and synchronized acorn production. We investigated the hypothesis that periodical cicadas (Magicada spp.), well known to have strong effects on the ecosystems in which they occur, affect acorn production of oaks through their xylem feeding habits as nymphs, the oviposition damage they inflict as adults during emergences, or the nutrient pulse resulting from the decomposition of their bodies following breeding. We found negative effects on acorn production during emergence years and the year following emergences and enhanced acorn production 2 years after emergence. We also found evidence indicating a significant effect of cicada emergences on spatial synchrony of acorn production by trees growing within the range of the same cicada brood compared with different broods. These results demonstrate that periodical cicadas act as a trophic environmental "veto" depressing acorn production during and immediately following emergences, after which the nutrient pulse associated with the cicada's demise enhances oak reproduction.

Drought constrains acorn production and tree growth in the Mediterranean holm oak and triggers weak legacy effects

Droughts are becoming more frequent in the Mediterranean basin due to warmer conditions. Droughts negatively impact forests growth for several years, often generating negative legacies or carryover effects. However, these legacies differ among tree species, sites and drought characteristics and have been mainly studied considering tree growth or canopy greenness, but ignoring reproductive phenomena. Here, we compare the legacy effects of drought on acorn and male inflorescence production and radial growth by using a 19-year series of 150 Quercus ilex individuals in three stands located in north-eastern Spain. We evaluate the relationships between monthly climate variables, tree-ring width, acorn production and male inflorescence production. For the two driest years considered (2005 and 2012), when very few acorns were produced, we did not find negative legacy effects on acorn production in the three years following droughts. The production of male inflorescences did not show any significant legacy after drought, although its annual variation was related to the climatic conditions of the year before acorn ripening. Acorn production was higher than expected for some of these years, apparently following the pattern of tree growth recovery with a certain lag. This compensatory response of acorn production differed between the two analysed droughts, in accordance with different conditions of drought timing and post-drought climate conditions. Even though few negative legacy effects of growth and acorn production were found, we confirmed the negative effect of drought stress on tree growth and acorn production, linked to dry winter conditions. Our findings confirm that drought features (timing, duration, intensity) and post-drought climate conditions influence tree growth and reproduction legacies.

The bigger the tree the better the seed – effect of Sessile oak tree diameter on acorn size, insect predation, and germination

Sessile oak is one of the ecologically and economically most important tree species in Europe. Recently, the importance of this species has been particularly highlighted in the context of climate change, where it is expected that these species will play a significant role within their natural range and beyond. To regenerate and expand the range of the sessile oak forests, a large amount of healthy acorns is needed. The acorn production and the acorns themselves are endangered by a large number of abiotic and biotic factors. As oak trees of different sizes do not produce the same amount of seed of the same quality, we investigated how the sessile oak tree diameter affects the acorn size, insect infestation, and germination rate. On the other side, as the acorn size influences the attack rates of the most significant acorn pest – Curculio glandium (Marsham, 1802), and the germination rates of both the damaged and healthy acorns we also investigated how the acorn dimensions influence the insect damage and germination rates, and how the insect damage influences the germination rates. We determined that the oak tree size influences some oak seed characteristics that are important for forest regeneration, while it does not affect others. A greater acorn yield was recorded on the bigger oak trees. The tree dimensions also had a significant influence on the acorn size. Greater average length, as well as greater average acorn diameter, were recorded on bigger trees. Although the tree size affects the acorn size, it does not influence the acorn insect predation rates or its germination rates. These parameters are affected by the acorn size itself. Bigger acorns had a greater germination rate. Insects preferred smaller acorns and had a significantly negative influence on the germination rate.

Acorn production of introduced Quercus rubra is more strongly impacted by the weather than by the forest site (a case study from Poland)

Recognition of the seed crop size and the periodicity of abundant seed production is essential for the management and control of introduced tree species. Here we studied acorn production of the North American northern red oak, Quercus rubra – the most common commercially important and invasive alien tree in European forests. A four-year (2017-2020) study conducted in even-aged Q. rubra stands, planted 55-60 years ago in sites of coniferous, mixed, and deciduous forests in central Poland, revealed a great variation in size of premature and mature acorn yields both among stands within the same year and among years for the same stand. However, each year numerous acorns of the introduced oak entered existing ecosystems, and the supply of mature propagules was more stable in the studied forests than in the Q. rubra native range. The total acorn crop was correlated significantly with the forest site, however, the forest site had a weaker effect on Q. rubra masting than the weather. Increases in abortion of acorns and decreases in mature acorn crops were preceded by reproduction-inhibiting weather events, and lower crops of mature acorns were correlated with abundant premature acorn abscission. In reaction to the weather, the phenology of premature and mature acorn shedding was very variable in subsequent years, but it was synchronized in time among all forest sites studied. The size of seed crop at the stand level was shaped by acorn crops of the highly-productive trees, and their identification within stands can be crucial for both effective management and control of Q. rubra in European forests.

A comparison of visual survey methods to estimate acorn production: A means of standardizing results

Acorns are a vital resource for many wildlife species and are required for oak (Quercus spp.) regeneration. Many different methods can be used to estimate acorn production and generate a hard mast index (HMI), however, the ability to compare data collected with different visual survey methods is limited. We conducted five visual acorn production survey methods on 70 oak trees (Quercus spp.) in northern Wisconsin from 1 August to 15 September 2020 to generate equations that convert indices of acorn production into a standardized index based on a 30-second count. We also used historical acorn production data from West Virginia (2000–2020) and North Carolina (2006–2019) for the standardization procedure. Indices from all visual survey methods were highly correlated to the 30-second count estimates, with HMI methods by Ryan et al. (2004) and Greenberg et al. (2007) having the strongest relationships (r = 0.99) with the 30-second count. The conversion equations from this study will provide managers a means of comparing data across visual survey methods and will expand the ability for future research in relation to acorn production.

Annual variability in the sound acorn production of Quercus serrata is regulated by a seed‐predatory weevil in western Japan

AbstractIn plants, processes from flowering to seed maturation are influenced by various factors, including weather conditions, resource supply, and damage inflicted by seed predators, that collectively contribute to annual variability in seed production. To identify the important factors associated with sound acorn production in Quercus serrata, from 2014 to 2020, we investigated the demographic processes from flowering to acorn maturation in six individual trees within a stand in a warm‐temperate secondary forest in western Japan. We found that the annual production of female flowers was positively correlated with the difference in April temperatures between successive years. However, their fluctuation was low and unaffected by either seed or flower production in the previous year. Compared with those of female flowers, the annual variability in sound acorn production within an individual was significantly higher and more synchronized. Key factor analyses revealed that reproductive losses due to the oviposition and sap‐sucking activities of Mechoris ursulus were the most prominent factors contributing to the observed annual variation in total predispersal losses at an individual level, and their effects were synchronized among individuals within a population. Survival from female flowering to sound acorn maturation was strongly predicted by the temperature in June, which corresponds to the period of adult M. ursulus emergence. Our findings indicate that the damage inflicted by the main seed predator during the predispersal stage can sufficiently regulate the sound acorn production patterns in Q. serrata that appear to resemble masting behavior (the highly variable and synchronized production of acorns within individuals).

Does mast seeding shape mating time in wild boar? A comparative study.

In seasonal environments, the timing of reproduction often matches with the peak of food resources. One well-known effect of global warming is an earlier phenology of resources, leading to a possible mismatch between the timing of reproduction for consumers and food peak. However, global warming may also change the dynamics of food resources, such as the intensity and frequency of pulsed mast seeding. How quantitative changes in mast seeding influence the timing of reproduction of seed consumers remains unexplored. Here, we assess how yearly variation in mast seeding influences mating time in wild boar (Sus scrofa), a widespread seed consumer species. We took advantage of the intensive monitoring of both female reproduction (1636 females) and acorn production over 6 consecutive years across 15 populations of wild boar in the wild. We found that mating time occurs earlier when acorn production increases in most but not all populations. In two out of 15 populations, heavy females mated earlier than light ones. Our findings demonstrate that mast seeding advances the mating time in some populations, which could perhaps impact how boars respond to climate change.