Cone Crop Research Articles

Innate immunity and environmental correlates of Haemoproteus prevalence and intensity in an opportunistic breeder.

While parasite infection can have substantial fitness consequences in organisms, the predictors of parasite prevalence and intensity are often complex and vary depending on the host species. Here, we examined correlates of Haemoproteus (a common malaria parasite) prevalence and intensity in an opportunistically breeding songbird, the red crossbill (Loxia curvirostra). Specifically, we quantified Haemoproteus prevalence and intensity in crossbills caught in the Grand Teton National Park from 2010 to 2013. We found that parasite prevalence varies seasonally and across years, with the highest number of infected individuals occurring in the summer, although there was variation across summers sampled, and that prevalence was positively related to annual mean cone crop sizes (a measure of crossbill food abundance) and daily ambient temperature (a correlate of vector abundance). Parasite intensity was significantly and positively related to one measure of innate immunity, leucocyte counts per blood volume. Finally, neither crossbill age, ecomorph, nor sex had significant effects on parasite infection intensity; however, parasite prevalence did significantly vary among ecomorph and age classes. These results support the interpretation that a combination of physiological (specifically immune activity) and environmental factors affects parasite prevalence and infection intensity in this opportunistically breeding avian species.

Mechanisms of population limitation in the southern red-backed vole in conifer forests of western North America: insights from a long-term study

Our goals were to characterize multiannual population changes of the southern red-backed vole (Myodes gapperi) to determine potential cycling behavior, and to specify the possible causes of these changes. We analyzed a detailed, 21-year record of changes in abundance of M. gapperi in late successional coniferous forest in southern British Columbia, Canada, from 1995 to 2015. We evaluated 3 hypotheses (H), namely that population changes are related to: (H1) changes in food supply from cone crops of coniferous trees; (H2) changes in forest habitat associated with beetle-killed lodgepole pine (Pinus contorta) trees; and (H3) territorial reorganization leading to breeding season declines in abundance. There were 3 cyclic population fluctuations (6- to 7-year periodicity) where red-backed voles reached mean fall numbers of 19–25, 15–16, and 26–27 per ha, respectively; in contrast, only 2–5 voles per ha occurred during population lows. Breeding season declines in abundance occurred in 17 of 21 years, with particularly precipitous drops ranging from 49% to 69% loss of voles. M. gapperi had more successful pregnancies, juvenile recruits, and adult recruits in the high than in the low population years. Mean index of early juvenile survival was 22% higher in low than high population years. Mean summer survival (58%) was consistently lower than that in winter (83%). Population increases were positively related to cone crops of 3 coniferous tree species. Thus, H1 was partially supported in 3 of 4 seedfall events. Positive changes in forest habitat, resulting from seed rain as a food supply and fallen debris from beetle-killed pine trees as cover, may have supported high numbers of voles in 2011–2012 (H2). A spring reorganization event limited the number of breeding animals by density-dependent inhibition of maturation and survival of juvenile voles, and led to breeding season declines (H3). Rigorous field experiments are needed to test these hypotheses and their interactions as mechanisms driving population change.

The role of urban habitats in the abundance of red squirrels (Sciurus vulgaris, L.) in Finland

Because the amount of urban areas has increased, it is important to investigate the abundance of wildlife species in relation to urban environments. Analyzing the impact of urbanization on the presence of forest-dwelling mammals is of interest due to the possible effects of urbanization on human-wildlife relationships and urban biodiversity. The Eurasian red squirrel (Sciurus vulgaris) is a declining forest species, and its occurrence in urban environments has been inadequately studied. The loss and fragmentation of forests due to urbanization may be detrimental for squirrels, whereas the abundant and predictable food resources and the low number of natural predators in urban areas may encourage squirrels to invade towns. We used large-scale data collected by volunteer bird watchers along a 950km south-north gradient to study whether the winter abundance of squirrels in Finland is dependent on urbanization, while controlling for effects of habitat type, food abundance (spruce cone crop; number of winter feeding sites), predator abundance (northern goshawk, Accipiter gentilis; feral cat Felis catus), season and latitude. We found that squirrel abundance increased with human population density, number of feeding sites and spruce cone crop and decreased with latitude and season. Feral cats showed weak negative connection with squirrel numbers, but there were no effect of goshawks. Relative squirrel abundance was approximately twice as high in urban habitats than in forests. Artificial feeding rather than a low number of predators may attract squirrels in urban environments. Planting spruce trees in urban environments will also benefit squirrels. Our results indicate that urban areas are an important habitat for the red squirrel even along the northern edge of their distribution range, where natural forest areas are still widespread. We conclude also that a citizen science −based bird survey protocol associated with mammal surveys seems to be a good large-scale monitoring method to study the urbanization of squirrels.

Longleaf Pine Cone Collection on the Sabine National Forest during October 2014

Longleaf pine is known as an unpredictable seed producer, with adequate or better seed crops occurring once every 5 years or longer. However, in the spring before seed fall, good cone crops can be predicted by visually counting green cones in the canopy, which by then are large enough to be seen, especially when binoculars of suitable power are used. During the spring of 2014, cone surveys in eastern Texas suggested that the autumn longleaf pine cone crop there could be a bumper crop. As a result, staff of the National Forests and Grasslands in Texas, in cooperation with Southern Region Forest Management staff, planned and conducted a longleaf pine cone collection that was implemented during the fall of 2014. Results were a great success, with more than 1,000 bushels of cones collected, producing nearly 1,000 pounds of seed (equivalent to approximately 5 million seedlings, enough to plant roughly 8,000 acres at typical planting rates). This seed supply will meet the needs of the National Forest and Grasslands in Texas for the foreseeable future.

Norway spruce cone crops in uneven-aged stands in southern Finland: A case study

Norway spruce cone crops in individual trees from two seed ripening years 2012 and 2014 were studied. Data were collected from five stands in southern Finland, managed by single-tree selection harvests since the 1980s. The upper third of living crown of each individual tree was photographed for digital cone counting with image analysis. The average number of cones per tree for trees bearing any cones was 92 in 2014 and 66 in 2012. Highest cone numbers found per individual tree were 526 in the year 2014 and 364 in the year 2012. Of all trees studied, 55.5% produced cones during both years, 9.6% produced cones once and 34.9% did not produce cones in 2012 or 2014. The number of cones per tree in 2014 was positively correlated with tree diameter at breast height and the presence of cones (at least twenty) in that particular individual two years earlier and negatively correlated with local basal area. The quality of the seed crop in 2014 as determined in two of the stands was poor. Based on X-ray analyses, 44% of seeds were empty, 29% were damaged by insects feeding on seeds (Plemeliella abietina or Megastigmus strobilobius) and only 25% were full and capable of germination. The results have implications for management practices in uneven-aged Norway spruce stands. It is suggested that at each harvest entry, some large, prolific trees should be retained in order to increase the total number of seeds produced in a stand to enhance regeneration and the recruitment of new seedlings.

Predicting white spruce cone crops in the boreal forests of southern and central Yukon

White spruce (Picea glauca (Moench) Voss) cone crops were measured at five regional centers in southern and central Yukon for 30 years at one site from 1986 to 2015 and at four other sites during 9 to 11 years to select the best climatic model that uses cues from growing season temperature and rainfall to predict the size of cone crops. We evaluated six climatic models that use summer temperature and rainfall of years t – 1 and t – 2 to predict cone crops in year t. July temperatures provided the best predictors of white spruce cone crops, and no rainfall variable was related to the size of cone crops. We explored three variants of July temperatures: mean temperature, degree-days > 5 °C, and maximum temperatures. For each of these, we used the ΔT model that uses the difference in the July temperature measures of years t – 1 and t – 2. We compared the resulting six models with corrected Akaike’s information criterion (AICc) to determine their relative predictive performance. The best model combined ΔT measures of degree-days > 5 °C and the four highest daily maximum July temperatures with R2 = 0.65. By comparison, the ΔT model involving only mean July temperatures was less successful (R2 = 0.49). There was good regional synchrony (rp = 0.7 to 0.8) in high cone crops over southern and central Yukon during 1986 to 2015.

Stand Dynamics Influence Masting/Radial Growth Relationships inPinus palustrisMill.

ABSTRACT Longleaf pine (Pinus palustris) regeneration is dependent on above-average masting (i.e., cone crop) years that occur over 5- to 7-yr cycles. Not understood, however, is how annual cone mast influences radial growth for longleaf pine. Here, we collected tree-ring data from one site in South Carolina and two sites in North Carolina to examine: (a) the relationship between longleaf pine mast and radial growth; (b) how timber thinning at one site affected this relationship; and (c) how previous October to current April Palmer drought severity index (PDSI) affects mast. We used dendroecological techniques to assemble three radial growth chronologies and compared annual radial growth to annual mast. We found the strongest negative correlation when mast was lagged 1 year from radial growth (i.e., mast of Year X with radial growth of Year X − 1), but current-year mast and growth were not significantly correlated. Mast/radial growth relationships were only detectible when radial growth indices less than...

A review of Sciurus Group studies on the red squirrel (Sciurus vulgaris): presence, population density and colour phases in Lombardy (Italy)

During the nineties of the last Century, under the inspiration of Luigi Cagnolaro, it had been founded a “Sciurus group”, within the Research Centres of the Società Italiana di Scienze Naturali. Aim of the group was to start a campaign of researches on red squirrel populations in Lombardy, Italy promoting field master thesis on various topics: colour phases and indirect estimations of population densities. The researches were carried out during 10 years in 5 study areas. An investigation and census with questionnaires were started in parallel, with the collaboration of Forest Guards (CFS), Ecological Guards (GEV) and students of biological and natural sciences. The results were published in Italian or exposed in national and international congresses. This review has the purpose to show and critically discuss the overall results, and make them available to a broader audience. The dark colour phase, in the red squirrel, resulted associated to elevation and conifer woodlands, according to the thermoregulation theory, which consider the dark fur thicker and more suitable in cold environments. Squirrel population densities are subject to periodical fluctuations, in conifer woodlands, due to cones availability. Cone crops are subject to cycle with years of great production followed by years of lean. The recorded squirrel densities are middle-lows, but in line with data from similar environments.

Light-level geolocators confirm resident status of a Southern European Common Crossbill population

Common Crossbill (Loxia curvirostra) populations are dependent on specific key conifer species for their primary food supply, but many of these conifers standardly show irregular cone crop production. Consequently, the species has evolved a nomadic behavior, breeding in areas with a high crop production in given years. Northern European crossbills mostly forage on Norway Spruce (Picea abies) and migrate along a northeast–southwest gradient across Europe. In contrast, crossbills from Spain were considered to be resident until recent studies on crossbill populations in the Pyrenees showed that a fraction of the population may also migrate. The type of movements of these Spanish birds, however, remains virtually unknown. The aim of our study was to resolve the question of whether these birds displace on a small local scale or whether they actually move to a distinct non-breeding area for part of the annual cycle. We tracked 14 male Common Crossbills from the Pyrenees with light-level geolocators for an entire year. Our results suggest that these birds were resident; only one bird may have shown a west–east movement of up to 200 km along the Pyrenean axis. We conclude that movement of the Common Crossbill from the Pyrenees may predominantly consist of relocation to nearby mountain ranges in Iberia or vertically in altitude. We expect that such small-scale movements have implications for population dynamics, and we recommend further research with telemetry to resolve the details of this small-scale movement.

Winter diet and hunting success of Canada lynx in Colorado

ABSTRACTInformation regarding the diet of Canada lynx (Lynx canadensis) at the southernmost extent of its range is critical for managing the species under current and predicted climate conditions. Therefore, from 1999–2009, we investigated winter diet and hunting strategies of Canada lynx in Colorado, USA by tracking individuals in the snow to identify sites where lynx encountered and killed prey. Similar to other parts of lynx range, snowshoe hares (Lepus americanus) were the primary winter food in Colorado, especially when considering total biomass consumed. Red squirrels (Tamiasciurus hudsonicus) comprised the bulk of the remaining food items and were a substantial occurrence during several years, which is consistent with previous hypotheses regarding the diet of lynx in southerly populations. Lynx successfully captured snowshoe hares on 31% of attempts and red squirrels on 47% of attempts, similar to lynx in other regions. In contrast to other populations, the majority of chases of both prey species were initiated while actively hunting rather than by ambush and this behavior did not change through time. We found evidence for snowshoe hare refugia during winter; hunting success for hares peaked at sites with approximately 3,000 stems/ha, but was lower in more dense vegetation where hare densities were greater. Given this finding and the apparent importance of red squirrels as alternate prey, we suggest that management for lynx in the southern Rocky Mountains, USA, focus on maintenance of mature, uneven‐aged Engelmann spruce (Picea engelmannii)‐subalpine fir (Abies lasiocarpa) stands. Such stands naturally provide patches of dense and open habitats juxtaposed closely together that should simultaneously facilitate high hare densities (and refuge from predation) and accessibility to hares by lynx. Mature trees in such stands also provide abundant cone crops to sustain populations of red squirrels for use as alternate prey. © 2016 The Authors. Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

Current and future conifer seed production in the Alps: testing weather factors as cues behind masting

Temporal patterns of masting in conifer species are intriguing phenomena that have cascading effects on different trophic levels in ecosystems. Many studies suggest that meteorological cues (changes in temperature and precipitation) affect variation in seed-crop size over years. We monitored cone crops of six conifer species in the Italian Alps (1999–2013) and analysed which seasonal weather factors affected annual variation in cone production at forest community level. Larch, Norway spruce and silver fir showed masting while temporal patterns in Pinus sp. were less pronounced. We found limited support for the temperature difference model proposed by Kelly et al. Both seasonal (mainly spring and summer) temperatures and precipitations of 1 and 2 years prior to seed maturation affected cone-crop size, with no significant effect of previous year’s cone crop. Next, we estimated future forest cone production until 2100, applying climate projection (using RCP 8.5 scenario) to the weather model that best predicted variation in measured cone crops. We found no evidence of long-term changes in average cone production over the twenty-first century, despite increase in average temperature and decrease in precipitation. The amplitude of predicted annual fluctuations in cone production varies over time, depending on study area. The opposite signs of temperature effects 1 and 2 years prior to seed set show that temperature differences are indeed a relevant cue. Hence, predicted patterns of masting followed by 1 or more years of poor-medium cone production suggest a high degree of resilience of alpine conifer forests under global warming scenario.

Clark's Nutcracker Breeding Season Space Use and Foraging Behavior.

Considering the entire life history of a species is fundamental to developing effective conservation strategies. Decreasing populations of five-needle white pines may be leading to the decline of Clark’s nutcrackers (Nucifraga columbiana). These birds are important seed dispersers for at least ten conifer species in the western U.S., including whitebark pine (Pinus albicaulis), an obligate mutualist of Clark’s nutcrackers. For effective conservation of both Clark’s nutcrackers and whitebark pine, it is essential to ensure stability of Clark’s nutcracker populations. My objectives were to examine Clark’s nutcracker breeding season home range size, territoriality, habitat selection, and foraging behavior in the southern Greater Yellowstone Ecosystem, a region where whitebark pine is declining. I radio-tracked Clark’s nutcrackers in 2011, a population-wide nonbreeding year following a low whitebark pine cone crop, and 2012, a breeding year following a high cone crop. Results suggest Douglas-fir (Pseudotsuga menziesii) communities are important habitat for Clark’s nutcrackers because they selected it for home ranges. In contrast, they did not select whitebark pine habitat. However, Clark’s nutcrackers did adjust their use of whitebark pine habitat between years, suggesting that, in some springs, whitebark pine habitat may be used more than previously expected. Newly extracted Douglas-fir seeds were an important food source both years. On the other hand, cached seeds made up a relatively lower proportion of the diet in 2011, suggesting cached seeds are not a reliable spring food source. Land managers focus on restoring whitebark pine habitat with the assumption that Clark’s nutcrackers will be available to continue seed dispersal. In the Greater Yellowstone Ecosystem, Clark’s nutcracker populations may be more likely to be retained year-round when whitebark pine restoration efforts are located adjacent to Douglas-fir habitat. By extrapolation, whitebark pine restoration efforts in other regions may consider prioritizing restoration of whitebark pine stands near alternative seed sources.

Large-scale spatial synchrony in red squirrel (Sciurus vulgaris) sex ratios

Large-scale studies on population-level sex ratios are few, even though sex ratio is an important determinant of population viability and dynamics. Mechanisms driving large-scale sex ratio variation include spatially autocorrelated resources and scale differences in local versus global Fisherian feedback of the operational sex ratio. In this study, we reanalyze historic data on sex ratios based on 187,404 hunted subadult and adult red squirrels ( Sciurus vulgaris ) capturing spatial sex ratio variation in 50×50 km squares throughout Finland over a period of 8 years. Overall, sex ratio was slightly male biased (50.9%) and relatively more 50×50 km squares showed a bias toward males (19% of squares) compared to females (8% of squares). Sex ratio was spatially autocorrelated at distances up to 200 km and in some years showed a U-shaped pattern: regions that were in close proximity and those that were far apart had similar sex ratios, but regions in-between had opposite sex ratios. We found no evidence that food supply (spruce cone crop) drives regional red squirrel sex ratio. Our findings add to the scarce evidence that vertebrate sex ratios show spatial patterns over large scales.

Habitat selection, nest survival, and nest predators of Rusty Blackbirds in northern New England, USA

ABSTRACT Rusty Blackbird (Euphagus carolinus) populations have plummeted since the mid-20th century. Recent research in New England, USA, suggests that an ecological trap, created through timber harvesting on the breeding grounds, may be responsible. Red squirrels (Tamiasciurus hudsonicus) were hypothesized to be the primary nest predator, but definitive identification was lacking. The potential for mast cone crops to affect Rusty Blackbird nest predation via trophic interactions also remains unexamined. Our objectives were to identify the mechanisms by which an ecological trap may be operating in New England through a multiscale analysis of Rusty Blackbird habitat selection and nest survival, as well as predator identification and quantification. We located 72 Rusty Blackbird nests in Maine and New Hampshire in 2011 and 2012, and modeled habitat selection and nest survival as a function of habitat characteristics at the nest patch (5 m) and home range (500 m) scale. We placed camera traps at 29 nests to ...

Red Crossbill Invasion of Northwestern Arkansas during 2012-2013

An irruption of Red Crossbills (Loxia curvirostra) occurred in primarily northwestern Arkansas starting in November of 2012 and lasting to the end of May of 2013. Based on recordings of call notes, most birds around Fayetteville were Type 2, the large-billed ponderosa pine crossbill, associated with a variety of conifer species. Birds recorded in Carroll County were Type 3, the small-billed western hemlock crossbill, and they were associated with small cones on shortleaf pine (Pinus echinata). One recording was obtained in Fayetteville of Type 5, the lodgepole pine crossbill, only the third recording east of the Great Plains. Crossbills at the Fayetteville Country Club were observed eating algae (Cladophora sp.) during the months of December and January, a behavior rarely reported for passerines. During March, crossbills appeared at sunflower bird feeders, which is a relatively recent phenomenon associated with low conifer seed abundance. The first two Arkansas specimens of crossbills (probably Type 3) were obtained from birds that struck windows near feeders. This is only the third recorded irruption of crossbills in Arkansas in the last 43 years, suggesting that crossbills rarely travel this far south in search of cone crops.

Seed and Cone Production Patterns from Seventy-Nine Provenances of Pinus halepensis Mill. Across Tunisia Forests

Pinus halepensis Mill. is an important tree species in the Mediterranean Basin. In Tunisia, there is an increasing interest in its seed production due to their impact on the socio-economical life of the Tunisian population, forest regeneration (seedling production) and biodiversity maintenance. Adaptative strategies were developed to fire recurrence by early cone production and seed storage in the serotinuous cones. Tunisia's native forests were investigated to examine the impact of four bioclimatic zones on Aleppo pine cone and seed production. Stand characteristics and average tree size measurements were studied with simple and multiple regression analyses for explaining their influences in seed and cone production and characteristics. Results showed a positive relationship between the accumulated rainfall and the geographical variables to the number of cones and its seeds content. Density had a strong adverse effect on the average tree's cone crop and seed yield. The cone production and the total seed mass were positively correlated with tree dimensions, but diameter at breast height and crown height were the most explanatory variables. Several environmental factors substantially increased the production of cones and seeds. The results could help foresters to decide better locations of cone and seed production according to density in Aleppo pine forests.

A prominent stepwise advance of the tree line in north‐east Finland

Summary The elevational limit of trees (henceforth, the ‘tree line’) is widely considered to be a sensitive indicator of environmental change. Here, we document the 20th century tree line advance and increase in the tree population at the tree line ecotone, along a Pinus sylvestris‐dominated slope in north‐eastern Finland, in conditions where growth and recruitment have generally been linked to temperature variation. Using tree recruitment ages (growth to 1.3 m height) along an elevational transect, we compared recruitment to variation in environmental conditions associated with tree line dynamics, seed and cone crops, and reindeer densities. We further investigated the relationships among temperature and tree‐level growth variables. Results show the existence of a former tree line at approximately 400 m a.s.l. and an advance of trees that began in the 1920s and reached the top of the fell (at 470 m a.s.l.) in the 1980s. During this time, the population density of P. sylvestris increased from 4 to 468 trees within the 5.6 ha study plot. Needle and shoot lengths were positively related to air temperature but recruitment was not. Average rate of P. sylvestris advance over the 20th century was consistent with earlier studies, but the temporal patterns of both upslope advance and population density increase were unexpected: both were characterized by a strongly stepwise pattern, culminating in a rapid advance and density increase in the 1970–1980s, and returning to low levels in the 1990s. Despite a positive relationship between growth and temperature variables at the tree level, climatic variables, or seed and cone crops were inconsistent with recruitment patterns. For most part of the 20th century, the increase corresponded to the gradual atmospheric CO2 increase, but of the variables screened only the changes in reindeer densities coincided with the stepwise pattern. Synthesis. Our results confirmed the connection between tree‐level processes and temperature variability as expected from earlier studies. However, recruitment was not correlated with any of the environmental variables. Our findings point towards complex tree line dynamics, in which biotic agents may play a major role in mediating tree line response to environmental change.

Ecophysiological variables influencing Aleppo pine seed and cone production: a review

The most interesting factors associated with seed and cone production of Aleppo pine were largely reviewed to identify broad patterns and potential effectiveness of reforestation efforts and planning. Aleppo pine cone production and seed yields are relatively variable, with differences between spatial and temporal influences. These differences are considered, mainly between (i) year, (ii) stand characteristics and (iii) individual tree measurements. Annual variability among populations was recorded for cone production per tree, based on influencing factors such as genetic characteristics, wetness, nutrient availability, insect pests and disease. In addition, some factors may affect Aleppo pine tree growth directly but may be affecting seed and cone production indirectly. Therefore, reduced stand density results in less competition among Aleppo pine trees and accompanying understory flora, which subsequently increases the stem diameter and other tree dimensions, including seed production. This review suggests that reforestation planning, particularly thinning, will result in improved tree morphology that will increase Aleppo pine seed and cone crops. Wildfire intensity and stand conditions such as light and soil nutrient status are also examined.

Reproductive phenology of a food-hoarding mast-seed consumer: resource- and density-dependent benefits of early breeding in red squirrels

The production of offspring by vertebrates is often timed to coincide with the annual peak in resource availability. However, capital breeders can extend the energetic benefits of a resource pulse by storing food or fat, thus relaxing the need for synchrony between energy supply and demand. Food-hoarding red squirrels (Tamiasciurus hudsonicus) breeding in the boreal forest are reliant on cones from a masting conifer for their nutrition, yet lactation is typically completed before the annual crop of cones is available for consumption such that peaks in energy supply and demand are not synchronized. We investigated the phenological response of red squirrels to annual variation in environmental conditions over a 20-year span and examined how intra- and inter-annual variation in the timing of reproduction affected offspring recruitment. Reproductive phenology was strongly affected by past resource availability with offspring born earlier in years following large cone crops, presumably because this affected the amount of capital available for reproduction. Early breeders had higher offspring survival and were more likely to renest following early litter loss when population density was high, perhaps because late-born offspring are less competitive in obtaining a territory when vacancies are limited. Early breeders were also more likely to renest after successfully weaning their first litter, but renesting predominantly occurred during mast years. Because of their increased propensity to renest and the higher survival rates of their offspring, early breeders contribute more recruits to the population but the advantage of early breeding depends on population density and resource availability.

Thinning increases cone production of stone pine (Pinus pinea L.) stands in the Northern Plateau (Spain)

& Context Edible stone pine (Pinus pinea L.) nut is a forest product which provides the highest incomes to the owners of stone pine forests. & Aim The objective of this work is to evaluate the effect of first thinning on growth and cone production in an artificially regenerated stand in order to determine optimum intensity. & Methods A thinning trial was installed in 2004 to compare two thinning regimes (heavy and moderate) and a control treatment. From 2004 to 2012, six inventories of forest attributes were carried out, and the cone crop was harvested annually.Weevaluatedtheeffectofthinningsongrowthusing repeated measures analysis of variance with a mixed model approach. With regards to cone production, we first estimated the probability of finding cones in a tree by applying a generalized mixed model and then estimated cone production by using a mixed model, including climatic variables. & Results We found that thinning had a positive influence on tree diameter increment. Thinning increased the probability of finding cones and cone production. However, significant differences between heavy and moderate thinnings were not found. & Conclusion We recommend early silvicultural treatments in stone pine stands to favor the development of trees and larger edible pine nut production.