Non-mast Years Research Articles

Masting promotes transformation from predation to mutualism in an oak-weevil-rodent system.

The significance of ecological non-monotonicity (a function whose first derivative changes signs) in shaping the structure and functions of the ecosystem has recently been recognized, but such studies involving high-order interactions are rare. Here, we have proposed a three-trophic conceptual diagram on interactions among trees, rodents, and insects in mast and non-mast years and tested the hypothesis that oak (Quercus wutaishanica) masting could result in increased mutualism and less predation in an oak-weevil-rodent system in a warm temperate forest of China. Our 14-year dataset revealed that mast years coincided with a relatively low rodent abundance but a high weevil abundance. Masting not only benefited seedling recruitment of oaks through increased dispersal by rodents but also a decrease in predation by rodents and weevils, as well as an increase in the overwintering survival of rodents. Masting appeared to have increased weevil survival by reducing predation of infested acorns by rodents. These results suggest that masting benefits all participants in the plant-insect-rodent system by increasing mutualism and reducing predation behavior (i.e., a non-monotonic function). Our study highlights the significance of masting in maintaining the diversity and function of the forest ecosystem by facilitating the transformation from predation to mutualism among trophic species.

High stand density improves seed production in seed orchards of the masting species Picea abies

Reproduction in masting species is characterised by long intervals between good cone and seed production years, and only sparse reproduction between mast years. The physiological mechanisms behind masting, and how these are linked to internal resource status and external weather factors, is still a subject of scientific exploration and debate, as is the effect of climate change on masting. This study investigates cone production in one operational seed orchard in Sweden which was established with two different spacings and has since been subject to three tree thinning experiments. The spacings before thinning varied between 800 and 400 stems ha–1, and then thinning reduced the stand density in all trials to half, i.e. between 400 and 200 stems ha–1. In all three experiments cone production per tree was equal in un-thinned and thinned treatments, both in mast years and in non-mast years. Thus, the cone production per unit area was twice as high in the un-thinned areas. The conclusion from these experiments is that the establishment of Picea abies (L.) H. Karst. seed orchards with wide tree spacing is both a misuse of good orchard locations and bad economics.

Predictability of the Spatiotemporal Pattern of Wild Boar (Sus scrofa) Rooting Influenced by Acorn Availability

The natural regeneration of the temperate oak forests is often insufficient. Acorns of the oak serve as the basis of the recruitment and key food resources in these ecosystems, thus the crop size, the germination success and seed predators have crucial roles in the process. Wild boar (Sus scrofa) is often considered as one of the main mitigating agents in oak regeneration. Therefore, in our study we analyzed and compared the spatial patterns of the acorn density and the patches rooted by wild boar within and among the different examined time intervals in a 28 ha Turkey-sessile oak (Quercus cerris, Q. petraea) forest stand. Data were collected between 2016 October and 2019 December. In the acorn density patterns, intra-annual similarities were recognized mainly, regardless of the crop size. Meanwhile, rooting patterns showed inter- and intra-annual similarities in mast years and intra-annual overlaps in non-mast years, indicating that masting is a fundamental driver of wild boar foraging behavior. However, a direct local connection between the rooting intensity and the acorn density could not be shown, as wild boars never fully depleted the acorns, even in intensively used patches. This study can help in predicting the intensively rooted forest patches, providing opportunities to manage wildlife conflicts.

Yearly Fluctuations in Honey Production in Hokkaido, Northern Japan, with Special Reference to Weather Conditions and Masting Behavior

The factors controlling yearly fluctuations in honey production are poorly understood. To evaluate yearly fluctuations in honey production, the coefficient of variation (CV) and the autocorrelation analysis were used to determine the magnitude and periodicity of the fluctuations for seven major nectar-source plants (basswood, black locust, Amur cork tree, white clover, buckwheat, Kamchatka thistle, and horse chestnut) using 15-years of data obtained in Hokkaido, Japan. Regression analysis was conducted to evaluate the relationship between annual honey production and the corresponding weather conditions during the flowering month. The periodic synchronous flowering and fruiting observed in tree species is called masting or masting behavior. A masting model, based on the resource budget, was applied to tree species if periodicity was detected by an autocorrelation analysis. The CV differed markedly among species. Black locust and the Amur cork tree had the smallest and largest CVs, respectively, whereas basswood was periodic. A negative correlation was observed between monthly precipitation and honey production in black locust, white clover, thistle and the Amur cork tree. This result implies that rain inhibits honey bee foraging. Production of buckwheat honey, however, tended to increase with increasing mean temperature. It might be difficult to detect the effect of rain on the honey production using buckwheat presumably because of the long flowering period. Annual honey production in basswood could be described by the resource budget model, but not in horse chestnut. Some horse chestnut trees produce flowers even in non-mast year implying that it was difficult to detect the periodicity in this species. According to beekeepers, honey production in this last decade in Hokkaido has been disrupted by climate change and the transitioning of the industrial structure.

Synchronous masting regulates seed-seed interactions for two co-fruiting tree species under the mediation of rodents

Knowledge is lacking on how masting regulates seed-seed interactions of sympatric tree species under the mediation of rodents. Here, we compared rodent-mediated seed dispersal between two sympatric tree species (Castanea mollissima and Quercus aliena) in both monospecific and mixed plots, across five successive years in the Qinling Mountains, China. We investigated: (a) whether the rodent-mediated seed dispersal success of each tree species was affected by the presence of the other, and (b) if any effects on dispersal were influenced by either the abundance of rodents present, or by (c) masting (i.e., seed abundance). We found both short-term mutualism and competition occurred between these two sympatric tree species. In non-mast years, the presence of Q. aliena seed reduced predation on C. mollissima seeds and promoted seed caching, which resulted in higher rates of C. mollissima seed dispersal. Synchronous masting enhanced this benefit to C. mollissima seeds, although we detected no clear neighbor or masting benefits for Q. aliena seed dispersal. This shows that inter-specific interactions differ between these masting neighbors, which may relate to either relative species-specific seed abundance or seed traits. We conclude that seed abundance mediates rodents’ seed forging and caching strategies, which may be important for forest regeneration and forest tree species composition.

Low Rate of Pre-Dispersal Acorn Predation by Eurasian Jays Garrulus glandarius during Non-Mast Years

Mast-seeding is widely considered to be an adaptation that minimizes seed predation. The superabundance of seeds during mast years greatly exceeds the capacity of seed predators to consume them. These notions were based on research on food specialists such as insects and rodents. However, mast-seeding may have different impact on the behavior of corvids that are food generalists. The Eurasian Jay Garrulus glandarius is a widespread scatter-hoarding corvid that uses acorns as a food reserve for winter. In mast-years, the birds are supposed to be satiated by the greater seed supply and are able to store their surplus, acting as dispersal agents, whereas in poor crop seasons they use most of the crop for current consumption and thus become seed predators. In such a situation, a dispersal agent may become a seed predator, and vice versa. The main task of this study was to determine the levels of pre-dispersal acorn predation by Jays during non-mast years to verify the notion that under such conditions Jays act mostly as seed consumers. During two consecutive non-mast years, tagged acorns were radio-tracked and the acorns' fate (cached or eaten) was assessed. We found extremely low pre-dispersal acorn predation by Jays (0.9%). The possible reason is that temperatures in period of acorns collecting (September–October) are high enough to allow invertebrates to remain active, so the Jays may supplement their diet with insects and also fleshy fruits. Therefore, almost all acorns were cached and scatter-hoarding Jays provided effective seed dispersal, with extremely low consumption of acorns.

Host plant utilisation of two Dicraeus species (Diptera: Chloropidae) feeding on bamboo flowers

ABSTRACT Bamboos are known for flowering simultaneously over a wide geographic range at long intervals of more than several decades. Florivory by Dicraeus phyllostachyus and D. nartshukae causes severe damage to bamboo seed production. However, the nature of the life history of the two Dicraeus species, particularly how they sustain populations during non-masting years of bamboos such as their host plant range, is poorly explored. We hypothesised that the two Dicraeus species host on other plant species and/or on non-floral organs of bamboos and move to bamboo florets during masting years. We tested whether the two Dicraeus species oviposit and develop on florets of grasses excluding bamboos (other grasses), and on non-floral organs of bamboos, including branch buds and bamboo shoots, by conducting a natural population survey and laboratory experiments. We found that the two Dicraeus species utilise short, slender shoots of Phyllostachys nigra var. henonis and a few other grass florets in the natural populations. Laboratory experiments also showed that the two Dicraeus species oviposited and fed on non-floral organs of bamboos and several species of other grass florets, although the oviposition rate and number of eggs varied among organs and the survival rate was low on most other grass florets. The generalised feeding ability may have enabled the two Dicraeus species to utilise the bamboo florets during masting years and become the dominant florivorous insect of bamboos. Unravelling their life history strategies may contribute to understanding adaptation in florivorous insects of masting plants as well as their impact on the evolution of masting in plants.

Environmental and individual determinants of burrow-site microhabitat selection, occupancy, and fidelity in eastern chipmunks living in a pulsed-resource ecosystem.

Habitat selection has major consequences on individual fitness, particularly selection for breeding sites such as nests or burrows. Theory predicts that animals will first use optimal habitats or rearrange their distribution by moving to higher-quality habitats whenever possible, for instance when another resident disperses or dies, or when environmental changes occur. External constraints, such as predation risk or resource abundance, and interindividual differences in age, sex and body condition can lead to variation in animals' perception of habitat quality. Following habitat use by individuals over their lifetime is thus essential to understand the causes of variation in habitat selection within a population. We used burrow occupancy data collected over eight years to assess burrow-site selection in a population of wild eastern chipmunks (Tamias striatus) relying on pulsed resources. We first compared characteristics of burrow microhabitats with those of equivalent unused plots. We then investigated the factors influencing the frequency of burrow occupation over time, and the individual and environmental causes of annual burrow fidelity decisions. Our results indicate that chipmunks select microhabitats with a greater number of woody debris and greater slopes. Microhabitats of burrows with higher occupancy rates had a lower shrub stratum, were less horizontally opened and their occupants' sex-ratio was skewed towards males. Burrow fidelity was higher in non-mast years and positively related to the occupant's age, microhabitat canopy cover and density of large red maples. The quality of a burrow microhabitat appears to be determined in part by characteristics that favour predation avoidance, but consideration of occupancy and fidelity patterns over several years also highlighted the importance of including individual and contextual factors in habitat selection studies.

Density-dependent plasticity in territoriality revealed using social network analysis.

Territories are typically defined as spatially exclusive areas that are defended against conspecifics. Given the spatial nature of territoriality, it is inherently density dependent, but the economics of territoriality also depend on the distribution and abundance of defended resources. Our objectives were to assess the effects of changing population density and food availability on individually based territorial phenotypes. We developed a novel analytical framework that bridges spatially explicit territories with social network analysis to model density-dependent territorial phenotypes. Using the outputs from our data pipeline, we modelled plasticity in territory size and territory intrusion rates in a long-term study population of North American red squirrels Tamiasciurus hudsonicus. Red squirrels defend year-round territories around a central hoard (midden) of white spruce Picea glauca cones. Importantly, white spruce is a masting species that produces large cone crops every 4-7 years (i.e. mast years) in our study area interspersed with non-mast years when few cones are produced. In the spring following mast years, populations are approximately double in size, but are lower in the spring of non-mast years. We predicted that territory size and intrusion rates would decrease as resource abundance, and consequently population density, increased. By contrast, as resource abundance decreased via depletion, and therefore density decreased, territories should increase in size and intrusions should also increase. As we expected, individual territory size and territorial intrusions were negatively density dependent, such that increased density after mast years resulted in smaller territories and fewer intrusions. When considering between-individual variation in plasticity across a density gradient, individuals responded differently to changes in population density within their lifetime. Our results show that territory size and intrusion rates display negative density dependence. When food becomes available in the autumn of a mast year and density in spring of the following year increases, territories shrink in size to effectively a small area around the midden. While our findings for red squirrels are unique compared to other systems, they serve as a reminder that the direction and strength of fundamental ecological relationships can depend on the nature of the system.

Novel food resources and conservation of ecological interactions between the Andean Araucaria and the Austral parakeet.

In fragile ecosystems, the introduction of exotic species could alter some ecological processes. The Austral parakeet (Enicognathus ferrugineous) shows close ecological and evolutionary relationships with the Andean Araucaria (Araucaria araucana), so any alteration in these interactions may have negative consequences for both partners and for ecosystem functioning and structure. We conducted extensive roadside surveys to estimate the abundance of parakeets in the northern Patagonian Andes over 4 years and recorded the food plants consumed by foraging flocks. The use of native habitats and humanized areas like villages and farms was influenced by the Araucaria seed crop. In masting years, the large seed crop allowed a massive use of this resource during the non‐breeding season, and even during the breeding season. The exploitation of exotic plants was minor in the masting year, but became predominant in non‐masting years, especially during the non‐breeding season. This feeding switch towards exotic plants primarily arose because the low Araucaria seed crop in non‐masting years is entirely consumed just after production by domestic and wild exotic mammals living in Araucaria forests year‐round, thus forcing the displacement of parakeets towards anthropic habitats to exploit exotic plants. Given the degradation of the remaining Andean Araucaria forests due to the impact of exotic mammals on the ecological interaction between Araucaria and Austral parakeets, ambitious programs to exclude or reduce the density of these alien mammals, including livestock, are warranted.

Food availability alters community co-occurrence patterns at fine spatiotemporal scales in a tropical masting system.

Patterns of co-occurrence among species can help reveal the structure and assembly of ecological communities. However, studies have been limited by measuring co-occurrence in either space or time but not both simultaneously. This is especially problematic in systems such as masting forests where resources are highly variable, meaning that spatial use and co-occurrence patterns can change on fine spatiotemporal scales. We develop an analytical framework for assessing species co-occurrence at fine spatial and temporal scales simultaneously and apply these models to a camera trapping dataset from Borneo. We sought to determine how substantial variation in food availability across space and time affects co-occurrence among terrestrial vertebrates. We detect many significant, mostly positive, co-occurrence patterns among species, but almost entirely in unlogged forest and during dipterocarp mast years. The most strongly co-occurring pair of species, bearded pig (Sus barbatus) and sambar (Rusa unicolor), only positively co-occur in areas and years when fruit is locally abundant. Species occurrences in logged forest and non-mast years are mostly random with respect to other species. This suggests that frugivore-granivore species positively co-occur when resources are plentiful (i.e., large trees are present and fruiting), likely because they use the same resources; these patterns disappear when food availability is lower. Our approach demonstrates the utility of measuring co-occurrence in space and time together and highlights the importance of resource abundance for driving the co-occurrence structure of communities. Furthermore, our method could be broadly applied to other systems to assess fine-scale spatiotemporal patterns across a range of taxa.

From trees to fleas: masting indirectly affects flea abundance on a rodent host.

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow-necked mice in beech forest after 2 mast and 2 non-mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density-dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance ("dilution," which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump-shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation.

The Feast and the Famine: Spring Body Mass Variations and Life History Traits in a Pulse Resource Ecosystem.

AbstractPhenotypic plasticity is the most immediate mechanism of adaptative response to environmental change. Studying plastic changes in response to fluctuating environments provides insights into how such adjustments may impact life history traits. Here, we used a 14-year data set of repeated body mass measurements in male eastern chipmunks (Tamias striatus) to assess the extent of plastic changes for this trait in a resource pulse ecosystem. We first determined the magnitude of variation in body mass at the population level in response to the drastic change in food resource availability from American beech tree seeds (Fagus grandifolia). Males that emerged in the spring from winter torpor following a nonmast year had a lower body mass than males emerging after a mast year, but they tended to recover this loss by mid-June. We found significant among-individual variation in spring body mass plasticity (i.e., individual-by-environment interaction). We then investigated the relationships between individual spring body mass plasticity, longevity, and lifetime reproductive success. Interestingly, heavier males lived longer than lighter males, but more plastic males had a lower longevity and lower lifetime reproductive success than less plastic males. The report of such plastic response in a stochastic resource system provides valuable insights into the interplay between the costs and benefits of phenotypic plasticity as an adaptation to environmental fluctuations.

Solitary vs communal use of nest boxes by the Edible Dormouse (Glis glis)

The Edible Dormouse often forms group associations in den sites. We characterize, over a 13-year period, how often the dormice rest alone or communally in nest boxes. The majority (87%) of individuals are solitary, resting alone during the daytime in nest boxes. In communal associations, groups of two or three individuals were the most common. We assessed the role of ambient temperature, seed mast, density of nest boxes and the surrounding vegetation on occupancy patterns. Seed mast and nest box density had a significant effect on group associations. Groups were more common in non-masting years. The lower the density of nest boxes at the study sites, the more common were group associations. In addition, a higher proportion of beech trees surrounding the nest boxes was associated with more frequent group associations.

Effects of mast seeding and insect infestation on predation and dispersal of Castanea mollissima nuts by rodents in the Qinling Mountains of China

Seed predation and dispersal by rodents plays an important role in woodland regeneration. To understand the impact of insect-infestation under different food abundance conditions on rodent predation and dispersal preferences, it is necessary to determine whether rodents have the ability to distinguish between infested and non-infested seeds and whether feeding strategies are affected by food abundance. Here, we compared the predation and dispersal fates of infested and non-infested nuts of Castanea mollissima in mast and non-mast years in a subtropical forest in the Qinling Mountains, central China. We found that rodents could discriminate between infested and non-infested nuts of C. mollissima. Harvest rates of non-infested nuts were relatively faster than those of infested nuts, and rodents preferred to consume infested nuts (typically in situ), while non-infested nuts were cached more often and dispersed farther. Mast seeding had a significant effect on seed predation and dispersal by rodents. When per capita food availability was low (i.e., in non-mast years), harvest rates and dispersal distances (including eaten and cached distances) were obviously accelerated and increased irrespective of insect-infestation. While in mast seed years rodents chose to cache more nuts, and selectively caching a higher proportion of non-infested seeds. This indicated that mast seeding could promote seed caching and result in more seeds escaping predation, which would enhance seed germination and forest regeneration.

Red foxes increase reproductive output of white spruce in a non-mast year

Predators may act as ecosystem engineers by modifying their physical environment through non-trophic interactions. Red foxes (Vulpes vulpes) are ecosystem engineers in the boreal woodlands, a nutrient-poor environment, where their denning activity increases soil nutrient concentrations, affecting the diversity of vegetation around dens. Since dens can persist for many decades and tree growth is enhanced on dens, dens can be used to study the long term impacts of nutrient additions on community and ecosystem processes. We examined the reproductive output of a mast-seeding conifer, white spruce (Picea glauca), on 10 red fox dens and paired control sites at the boreal treeline near Churchill, Manitoba, in July 2019. We estimated cone production in both the current non-mast year (2019) and the previous mast year. The number of cones produced per tree and per hectare was significantly higher on dens than control sites in the non-mast year, but did not differ in the mast year. Higher cone production on dens was partly driven by trees being larger on dens. These results suggest that red fox ecosystem engineering activity affects white spruce reproduction, since increased soil nutrients on dens allow for higher cone production, but the effect of red fox denning is limited by interactions with mast-seeding mechanisms. For example, weather cues may override the effects of denning in mast years, while trees on dens may be able to allocate more resources to reproduction in non-mast years, but store the same amount of resources as trees off dens to produce similarly large cone crops in mast years. Altered resource availability in this nutrient-limited landscape could have additional ecological implications, by affecting the foraging patterns of seed predators and spruce range expansion.

Characterizing the climatic niche of mast seeding in beech: Evidences of trade-offs between vegetation growth and seed production

Masting is a complex mechanism which is mainly driven by a combination of internal plant resources and climatic conditions. While the driving role of climate in masting is being intensively studied, the interplay among climate, seed production, vegetation growth and phenology still needs further investigation. The objectives of thisstudy were to identify the climatic determinants of different levels of seed production and of NDVI-based vegetation growth and phenology in European beech, and to evaluate if exists a trade-off between these two plant processes. To answer these questions, we used a 25-year-long dataset of beech seed production. We exploited the concept of ecological niche assuming that a mast year can be modeled like a species with variable preferences for different resources, which are the underlying annual climatic conditions; we performed an Ecological Niche Factor Analysis (ENFA), a presence-only modeling tool conventionally used in zoology and botany, and used seasonal (spring, summer, autumn) Standardized Precipitation-Evaporation Index (SPEI) observations, considering the current year (y−0), and up to one (y−1) and two (y−2) years before the masting event. For analyzing the role of vegetation growth and phenology, we used seasonal Normalized Difference Vegetation Index (NDVI) values and associated NDVI-based phenological metrics derived from Landsat imagery. Results indicated the driving role of climate for masting, especially in VHSP years. A moist summer and dry spring at y−2 and a dry summer at y−1 represented the main driving climatic conditions for masting; while a moist spring during the observation year represented the key condition for triggering higher intensities of seed production. Summer NDVI at y−0 and y−1 represented the variables discriminating best between masting and non-masting years and resulted as driven by opposite summer climatic conditions than seed production, thus indicating a trade-off between seed production and vegetation phenology. We concluded that reproduction and vegetation growth act as two different climate-dependent plant responses in beech, in a way that certain conditions through the years promote mast seeding and the opposite conditions favor vegetation growth. The understanding of climate-growth-masting relationships represents indispensable knowledge for providing a holistic view of masting mechanisms and developing adaptive forest management strategies in this species.

Restrictions on natural regeneration of storm-felled spruce sites by silver birch (Betula pendula Roth) through limitations in fructification and seed dispersal

Particularly after disturbance events, the early successional colonist Betula pendula Roth is experiencing renewed silvicultural interest with respect to the natural regeneration of large disturbed forest areas. In a case study, we therefore studied the seed dispersal of B. pendula from two adjacent spruce stands to large storm-felled sites at high altitudes in the Thuringian Forest (Germany) over a 2-year period. We applied inverse modelling to describe the distance-dependent seed distribution using a negative exponential kernel and seed production function of birch seed trees. Maximum seed numbers of 2015 n m−2 (non-mast year) and 9557 n m−2 (medium year) occurred within 40‒50 m distance to a seed tree. The predicted seed production rate of a birch seed tree with a reference dbh of 20 cm was approximately 350,000 n tree−1 (non-mast year) and 1,500,000 n tree−1 (medium year). Regardless of the seed crop, the dispersal distances were similar in both years. The isotropic model showed mean dispersal distances of 86 and 97 m (uphill) and 367 and 380 m (downhill) for the 2 years of seed sampling. No directionality in seed dispersal was found. The findings showed birch seed dispersal to be strongly influenced by site inclination, seed tree position (valley, slope or plateau) and distance to the storm-felled site. Furthermore, the seed shadow is influenced by the number of seed sources. Therefore, risk-adapted forest management should include the ‘spatial optimization’ of birch seed trees, ideally creating a network of small seed tree groups scattered more or less regularly within pure conifer forests.

Horizontal and elevational patterns of masting across multiple species in a steep montane landscape from the perspective of forest mammal management

ABSTRACTMasting of trees affects the activity of large mammals that feed on their fruits, but the spatial patterns of masting at the scale of mammal home ranges across multiple tree species have rarely been investigated. Furthermore, the effects of elevation, which may affect site productivity and thereby alter temporal patterns of masting, have often been ignored. We investigated fruit production by 403 trees of six species that are preferred by Asian black bears over 10 years within a 30 × 30-km2 landscape at 700–1600 m elevations, as well as the horizontal and elevational structures of intraspecies and interspecies synchrony. Higher elevation was related to greater temporal variation in fruiting for Quercus crispula. Among heterospecific relationships, two Quercus species and Swida controversa showed fruiting synchrony, whereas Prunus grayana produced more fruit when Quercus and Swida produced less. Fagus crenata and Castanea crenata did not exhibit masting synchrony, neither positive nor negative, with other species. Spatially, most tested species showed positive autocorrelations with horizontal distance, particularly between close trees (4–10 km), whereas autocorrelations with elevational difference showed negligible spatial structure across elevational distance. Positive spatial correlations between different species were found only for the two Quercus species. These findings imply that variation in movement patterns among individual Asian black bears should be greater in Quercus mast years and that most bears will range more widely than average in non-mast years for Quercus.

Masting and regeneration dynamics of Abies cephalonica, the Greek endemic silver fir

AbstractMasting and regeneration dynamics were investigated in a long-term perspective using Abies cephalonica as a study tree species. Extensive fieldwork was implemented in Parnitha National Park, Greece, following a large-scale wildfire. Annual cone production was monitored for a 5-year period in 130 tagged trees, in 13 plots with 10 individuals each, established both within the unburned part of the forest and in surviving fragments of the burned area. In the most recent masting year, a high percentage (88%) of cone-bearing trees was recorded, along with a sizeable, average cone production (40.8 cones per tree). In the intermediate, non-masting years, the corresponding values ranged from 2% to 55% and 0.08 to 5.9 cones per tree, respectively. The reproduction process is affected by both tree density and regional climatic conditions, in particular temperature during spring of the maturation year and precipitation during spring and summer of the previous year. For the first time according to our knowledge, natural regeneration was recorded for a 4-year period, in 13 permanent transects within the monitoring plots, in relation with a masting event and the additional implications of a preceding wildfire. Highest mean density of seedlings and saplings (11.4 per m2) was observed during the first spring after masting. In the non-masting years, the corresponding value ranged from 2.1 to 2.9 per m2. Seedling survival during their first summer was considerable (30–76%) but stabilized afterwards (1–3 years) at a lower level (10–20%). The particular post-masting seedling flush was followed by an extremely high mortality rate (88.6%) and cannot represent a major recruitment event.