Acorn Production Research Articles

Acorn Yields and Seed Viability of Pedunculate Oak in a 10-year Period in Forest Seed Objects across Croatia

Quercus robur L. exhibits not only a large inter-annual variability in seed production but also considerable variability among locations and individuals within the same year. The differences in how individual trees and populations of oaks invest in acorn production, both in terms of the yield size and the acorns quality, is of interest both ecologically and economically. For this research we used data collected from harvesting which has been organised and executed by the largest forestry company in Croatia - public enterprise Croatian Forests Ltd. According to the Act on Forest Reproductive Material, Croatian Forest Research Institute is designated as the Official Body that supervises production and provides analysis of quality of forest reproductive material. Regarding that, we summarized data of 10-year long records (from 2009 to 2018) of submitted seed samples and seed quality testing from 119 Q. robur forest seed objects across Croatia. Our aim was to investigate seed yield and effects of seed size and seed moisture content on seed viability. In the study period there were four years with higher quantity of collected seeds than other years (2010, 2011, 2015 and 2017). There was no significant difference in seed viability among forest seed objects. However, variations among years within forest seed objects were highly significant. It was also found that seed size (indicated by the number of acorns per kg) and seed moisture content were significantly related to seed viability. Bigger seed dimensions, i.e. lower mean number of acorns per kg, correlated with higher viability. Lower moisture content affected decrease in acorn viability. On average, viability dropped below 70% when acorn mean moisture decreased below 36%. Thus, it can be concluded that bigger seeds and seeds with moisture content of 40-44% have better viability.

Hunting and environmental influences on survival of male wild turkeys in Virginia and West Virginia

AbstractKnowledge of the effects of hunting and environmental influences on survival of eastern wild turkeys (Meleagris gallopavo silvestris) is critical to managers setting fall and spring hunting seasons. Research has shown improper season frameworks can result in unsustainably high harvest rates of adult males, affect male age structure, and result in lower hunter satisfaction. Our objectives were to estimate survival rates of males, identify causes of mortality, and relate hunting and environmental influences to male turkey survival. We captured and radio‐tagged male wild turkeys in Virginia (n = 204) and West Virginia (n = 197), USA, during 2004–2007. We used staggered entry Kaplan‐Meier models to estimate survival and Cox Proportional Hazards Models to estimate effects of predictor variables on survival. Survival was estimated for 3 distinct periods of interest: annual, fall hunting (October–January), and spring hunting (April–May). The leading causes of mortalities (209 turkeys) were legal spring harvest (42%), predation (25%), and poaching (17%). Only 8 turkeys (4%) were taken during fall hunting seasons. Confidence intervals for annual survival of 2 year‐old and 3+ year‐old turkeys overlapped; therefore, we combined adult ages into a single category (2+). Adult (2+) annual survival was 0.63 (95% CI = 0.58–0.69) and the harvest rate was 25% (95% CI = 20–29%) for the combined states. Annual survival rates for adults (2+) were greater than in most other published studies, whereas adult (2+) spring harvest rates were lower. For juvenile males, annual survival was 0.74 (95% CI = 0.68–0.79) and spring harvest rate was 7% (95% CI = 3–11%). High juvenile and adult (2+) survival may have been related to low harvest rates. Adult turkeys (2+) had 46% greater risk of dying than one‐year‐old birds and were 3.7 times more likely to be harvested than juveniles. Age, a relative phenology index (RPI; spring green‐up), and white oak (Quercus alba) acorn production were included in the top models for annual survival, spring season survival, and spring harvest risk. Increasing RPI (more foliage) decreased mortality risk and greater white oak (Quercus alba) acorn abundance increased mortality risk. Across 4 regions in the 2 states, fall survival was high (0.90, 95% CI = 0.87–0.93). The impact of fall hunting on males in Virginia was low (5% harvest rate, 95% CI = 0–9%). Overall, spring harvest had the greatest effect on male survival, although those effects were moderated by the previous fall white oak crop and the onset of green‐up in the spring.

Relationships between climate variables, seed production and reproduction of the Edible Dormouse (Glis glis) in mixed oak forests of the Iberian Peninsula

The Edible Dormouse (Glis glis) is a small arboreal mammal that lives in deciduous forests in much of Europe, the Iberian Peninsula being one of the southern limits of its distribution. Some studies have shown that this species uses the strategy of anticipatory reproduction, which means that it adapts its reproductive effort to seed production, such as beech mast and acorns, which varies greatly from year to year. The Edible Dormouse anticipates future seed availability of the coming autumn and modulates its reproductive effort, as beech mast and acorns are a crucial resource for the young to survive their first hibernation. This work aims to determine the correlations between annual variations in climate and seed production, and their effect on Edible Dormouse reproduction using 9 years of data (2012–2020) in two natural parks in Catalonia (Montseny and Montnegre-Corredor). These are located at the southernmost limit of the distribution of this species in the Iberian Peninsula. The results show that the productivity of Beech trees (Fagus sylvatica) is conditioned by local meteorological conditions and pollen availability, and that the acorn production by oak trees (Quercus sp.) is also affected by local meteorological conditions, but not by pollen availability. Additionally, breeding by the Edible Dormouse in Montseny has shown high synchrony with acorn production and that the presence of beech seeds increases the number of offspring per female. These results encourage us to conduct future studies to predict how Edible Dormouse populations will be impacted by climate change.

Individual-level variation in reproductive effort in chestnut oak (Quercus montana Willd.) and black oak (Q. Velutina Lam.)

Masting is a population-level reproductive strategy, where individuals synchronize large but intermittent seed production. Despite the high degree of synchrony at the population level, there can be considerable variation in reproduction among individuals (intraspecific variation). Here, we use 18 years of acorn production data from individual chestnut oak and black oak from control and thinned stands, to understand what factors influence individual differences in reproductive effort and variability. We included a variety of tree-level measurements, environmental characteristics, and measurements from tree cores to determine if certain characteristics were associated variations in reproduction. We considered both mean annual acorn production per m2 crown and interannual variation in acorn production (CV) as response variables. We also classified individuals as super producers (i.e., those that consistently produce more acorns than others), good, fair and poor producers (i.e., those that consistently produce less or have a higher number of failure years). In chestnut oak, 14% of the individuals were classified as super producers and contributed 34% of the total acorns, while poor producers made up 35% of the trees and contributed only 16% to total acorn production. In black oak, super producers (14% of the individuals) contributed 31% of total acorns and poor producers (24% of the individuals) contributed only 9% of the acorns. Diameter at breast height (DBH) was the most consistent variable for explaining intraspecific variation in reproductive effort and variability (i.e., larger individuals had higher mean acorn production for both chestnut oak and black oak, and lower CV for black oak). Other variables that influenced reproduction and variation included elevation and clay content for chestnut oak, and slope for black oak. We found no significant effect from the thinning treatment on acorn production. Our results illustrate how tree-level and environmental characteristics can distinguish acorn production groups, which can be used to inform management and selective harvesting decisions.

BUDBURST TIMING OF VALLEY OAKS AT HASTINGS RESERVATION, CENTRAL COASTAL CALIFORNIA

We studied the timing of budburst of valley oak (Quercus lobata Née) at Hastings Reservation, central coastal California. Similar to other taxa, budburst was advanced by warmer temperatures. Over the 30-year study period, however, there were no significant trends in either air temperature or the timing of budburst, except during the 2014–2016 drought, during which the earliest budburst dates were advanced. Several individual tree characteristics correlated with budburst timing, including access to ground water, soil available phosphorus, and elevation, the effects of which were in turn correlated with winter microclimatic conditions of individual trees. Budburst timing was significantly related to both subsequent acorn production and radial growth; trees leafing out on or near the population mean for the year experienced greater radial growth and produced larger acorn crops than trees leafing out earlier or later than the mean. Differences in acorn production were due to both differences in phenology among trees and plasticity in the phenology of individual trees across years, while differences in radial growth were primarily due to plasticity in individual tree phenology. Valley oak phenology exhibits considerable variability; the extent to which this plasticity will help this keystone California species adapt to future climate change remains to be seen.

Wood Density and Ring Width in Quercus rotundifolia Trees in Southern Portugal

Quercus rotundifolia Lam., known as holm oak or evergreen oak, occurs naturally in the western Mediterranean region, mainly as part of the agroforestry or agrosilvopastoral systems in Portugal (“montado”) and Spain (“dehesa”), and is economically important for acorn production. Less attention has been given to Q. rotundifolia wood, and its density variability is not known, namely related to tree growth. The wood density of 20 Q. rotundifolia trees was measured along the radial direction by X-ray densitometry and the factors responsible for ring width and wood density variation within and between trees were investigated at two sites located within the main species region in southern Portugal. Ring width was significantly different between sites, with an average of 1.81 mm and 1.55 mm. Wood density was very high and averaged between 888 kg/m3 and 914 kg/m3 but not significantly different between sites. Ring width and wood density showed a positive and significant correlation at both sites. Cambial age was the main source of variation for ring width and wood density, while between-tree effects accounted for a considerable proportion of wood density variation. The results are an important contribution for the species valorisation aiming at high-value wood products, also adding knowledge on the species growth of interest for tree selection and sustainable management.

Fire history and weather interact to determine extent and synchrony of mast-seeding in rhizomatous scrub oaks of Florida.

In disturbance-prone ecosystems, fitness consequences of plant reproductive strategies are often determined by the relative timing of seed production and disturbance events, but the role of disturbances as proximate drivers of seed production has been overlooked. We use long-term data on seed production in Quercus chapmanii, Q. geminata and Q. inopina, rhizomatous oaks found in south central Florida's oak scrub, to investigate the role of fire history and its interaction with weather in shaping acorn production and its synchrony. Acorn production increased with the time since last fire, combined with additive or interactive effects of spring precipitation (+) or drought (-). Furthermore, multiple matrix regression models revealed that ramet pairs with shared fire history were more synchronous in seed production than ones that burned in different years. Long-term trends suggest that increasingly drier spring weather, in interaction with fire frequency, may drive a decline of seed production. Such declines could affect the community of acorn-reliant vertebrates in the Florida scrub, including endangered Florida scrub-jays (Aphelocoma coerulescens). These results illustrate that fire can function as a proximate driver of seed production in mast-seeding species, highlighting the increasingly recognized importance of interactions among reproductive strategies and disturbance regimes in structuring plant populations and communities. This article is part of the theme issue 'The ecology and evolution of synchronized seed production in plants'.

Delayed fertilization facilitates flowering time diversity in Fagaceae.

Fagaceae includes typical masting species that exhibit highly synchronized and fluctuating acorn production. Fagaceae shows an interesting feature in that fertilization is delayed by several weeks to more than 1 year after pollination. Although delayed fertilization was recorded over a century ago, the evolutionary advantage of delayed fertilization is still poorly understood. Here, we present a new hypothesis that delayed fertilization facilitates temporal niche differentiation via non-overlapping flowering times among species. Comparing flowering and fruiting times in 228 species from five genera in Fagaceae, we first show that there is a close association between a wider spread of flowering times and the likelihood of a 2-year fruiting habit in which there is a long delay from pollination to fertilization. To study the coevolution of flowering time and delayed fertilization, we developed a mathematical model that incorporates the effects of competition for pollinators, seed predator satiation and unfavourable season for reproduction on fitness. The model shows that delayed fertilization facilitates the diversification of flowering time in a population, which is advantageous for animal-pollinated trees that compete over pollinators. Our new hypothesis about the coevolution of delayed fertilization and flowering time will provide new insight into the evolution of masting. This article is part of the theme issue 'The ecology and evolution of synchronized seed production in plants'.

Effect of environmental variables on incidence of tick-borne encephalitis, leptospirosis and tularaemia.

Potential effect of three environmental variables (population density of rodents, global weather in the form of the North Atlantic Oscillation (NAO) index, and acorn crop) on human morbidity rate of three zoonoses: tick-borne encephalitis (TBE), leptospirosis and tularaemia were analysed in the Czech Republic for the period 1970-1990. The Pearson's correlation analysis was used. The correlation analysis revealed that the significant factor for explaining annual morbidity rates of these zoonoses was the abundance of common voles (Microtus arvalis) in the current year (for leptospirosis) or in the previous calendar year (for TBE and tularaemia). The two other environmental variables tested (NAO index and acorn production) do not seem to play a significant role in these zoonoses in Central Europe.

Acorn Crop, Seed Size and Chemical Defenses Determine the Performance of Specialized Insect Predators and Reproductive Output in a Mediterranean Oak.

Simple SummarySeed predation is an antagonistic interaction that can limit plant population dynamics. We investigated the interaction between Quercus faginea and two specialized pre-dispersal insect seed predators (weevils and moths) during two years of contrasting crop size to determine the consequences of oak reproductive investment on seed production and insect performance. Crop and acorn size were lower during the second year, although seed predation rates by insects were similar during both crop years. Oaks producing more acorns reduced seed predation by insects during the large crop year and thus improved their reproductive success, and those producing bigger acorns experienced higher levels of seed predation, and more insect larvae developed inside the available acorns during the low crop year. Inter- and intra-specific insect competition increased during the low crop year and were affected by tannin content in acorns. Despite substantial between-year variations in crop and acorn size, insect performance was similar due to larvae being able to finish their development by depleting acorn reserves when resources were low. Crop size, acorn size and chemical composition seem important traits for reducing seed predation by specialized insects and improve reproductive success in this Mediterranean oak species.Seed predation is an antagonistic interaction that negatively affects the performance of individual plants and can limit plant population dynamics. In animal-dispersed plants, crop size is an important determinant of plant reproductive success through its effect on seed dispersers and predators. Seed traits, such as size or chemical composition, can also increase the tolerance to seed predators or reduce their performance. We investigated the interaction between Quercus faginea and two specialized pre-dispersal insect seed predators (weevils and moths) during two years of contrasting crop size to determine the consequences of oak reproductive investment on seed production and insect performance. Crop size was 44% lower and acorns were 32% smaller in the second year, although acorn predation by insects was proportionally similar between both years at the population level. Individual trees producing larger crops showed a lower incidence of insect predators during the year of abundant acorn production, whereas trees producing bigger acorns experienced higher seed predation rates by insects, and acorns held more insect larvae in the low crop year. Competition between insects increased when acorn production was low, and higher tannin content in acorns further constrained the number of weevil larvae developing together in the same acorn. However, the abundance and size of insect larvae produced per tree were similar between the two crop years, and this was due to larvae often depleting acorn reserves when resources were low. Oak reproductive output increased nearly two-fold during the large crop year. Crop size variation, acorn production in a given year and acorn size and chemical composition seem to be important traits for reducing damage by insect predators in Quercus faginea and improve oak reproductive success.

Towards optimizing acorn use as animal feed in Tunisia: evaluation and impact on natural regeneration

In Mediterranean forests, besides the conflict between forest managers and local populations who are often poor and dependent on livestock for survival, the cost of raw materials used in animal feed is increasingly a burden for farmers. There is growing recognition that wise use of acorns can reduce feed costs and enhance sustainable participatory governance of these woodlands. This paper aimed to carry out a quantitative, qualitative and economic evaluation of acorn potential in a cork oak forest in north-western Tunisia and to investigate the impact of their post-dispersal on natural regeneration. Quantities were estimated in November and February, respectively for acorns collected directly from trees and from the ground. Time-dependent monitoring of acorn quality and numbers of new seedlings was also conducted from autumn 2014 to spring 2015. The results show a significant decrease in acorn quantity from 5.28 ± 4.61 t/ha in November to 0.684 ± 0.1 t/ha in February. However, this loss did not put the early stages of natural cork oak regeneration at risk since the percentage of acorns not able to germinate was estimated at only 37% in late February. Furthermore, the average number of new seedlings was estimated in April at 40,000 seedlings/ha. A model was fitted to predict tree acorn production and to establish the best agroforestry system to optimize acorn use. Based on acorn quantity and quality data, earlier acorns should be directed to nursery and livestock production and the later acorns to wildlife and natural regeneration.

Effects of pulsed resources on the dynamics of seed consumer populations: a comparative demographic study in wild boar

AbstractMast seeding is a well‐known example of pulsed resources in terrestrial ecosystems. Despite the large literature available so far on the effects of mast seeding on the dynamics of seed consumer populations, it remains unknown whether heterogeneity in demographic responses to mast seeding exists both within a population of consumers and among consumer populations. Here, we fill this knowledge gap by assessing the effects of acorn production (i.e., oak mast) on all stage‐specific demographic rates (i.e., survival, growth, reproduction) in several consumer populations. From long‐term capture–mark–recapture data collected in three wild boar populations in Europe and detailed information on annual acorn production, we quantified the effects of acorn production on body mass‐specific demographic rates in these populations. We then built a body mass‐structured population model for each population and assessed the effect of acorn production on generation time—the mean age of mother at childbirth—and population growth rate using a combination of prospective and retrospective demographic analyses. Within populations, acorn production had a positive effect on reproduction (proportion of breeding females) and growth of small‐sized females. Survival remained buffered against environmental variation, in accordance with the demographic buffering hypothesis. Thus, all stage‐specific demographic rates were not influenced in the same way by acorn production. In turn, higher reproduction and growth probabilities involved higher population growth rates and shorter generation times. Despite these common demographic responses to mast seeding among populations, we highlighted marked among‐population variation in the magnitude of these responses. Also, while populations inhabiting resource‐rich environments took advantage of current acorn conditions, populations under resource‐poor environments stored and allocated acorns produced the preceding year to reproduction indicating contrasting breeding tactics along the capital–income continuum. Our results suggest heterogeneity in demographic responses to mast seeding, within and among populations. This is an important finding for our understanding of the effects of mast seeding on the dynamics of seed consumer populations.

Both weather and resources influence masting in chestnut oak (Quercus montana Willd.) and black oak (Q. velutina Lam.)

Masting is the synchronous and highly variable production of fruit within a population. Although several hypotheses have been proposed to explain why and how masting evolved in plants as a reproductive strategy, the factors that trigger a large reproductive effort in a particular year are still not well understood. While both weather and resources have been proposed to play an important role, testing these hypotheses has been challenging due to a lack of long-term data and appropriate experimental designs. In this manuscript, we used 18 years of acorn production data to analyze the relationship between resources, weather, and masting in black oak (Quercus velutina) and chestnut oak (Q. montana). The data were collected in southeast Ohio as part of the Fire and Fire Surrogate (FFS) study, which applied silvicultural treatments (i.e., thinning and prescribed fires) to reduce competition and manipulate resources. We found species-specific responses to the thinning and fire treatments, with an overall increase in acorn production for chestnut oak in the thin + burn treatment and an increase for black oak in the thin-only treatment compared to the control. Chestnut oak reproduction also had strong positive relationships with warm spring temperatures, and a positive change in summer temperatures compared to the previous year (i.e., summer temperatures that went from cool to warm). For black oak, warm spring temperatures increased acorn production while later starts to spring warming the year before decreased acorn production. These results support the hypotheses that both resources and weather (as a cue and as a limiting factor) are important for masting in oaks. Thus, both factors should be included in predictive models for acorn production under current and future climate conditions.

Blacklegged tick population synchrony between oak forest and non‐oak forest

1. Fluctuations in abundance of blacklegged ticks in space and time are well‐documented, but the extent to which populations fluctuate synchronously across habitat types is poorly understood. In oak forests, blacklegged tick density depends on small mammal abundance, which is in turn driven by fluctuations in acorn production. It is currently unknown whether fluctuations in tick abundance in oak forest, long understood to depend largely on masting events, are shared with nearby non‐oak forest.2. In this study, we analysed 22 years of tick population data from nine forest plots in south‐eastern New York in order to compare fluctuations of nymphal and larval blacklegged tick populations in oak‐dominant forests and non‐oak forests.3. We found that population peak densities of nymphal ticks were strongly synchronous in oak and non‐oak forests among years and that larval population dynamics were weakly synchronous between these two forest types.4. Our results suggest that drivers of immature tick density in oak‐dominant forest, including climatic factors and mast‐driven host dynamics, may also influence tick population fluctuations in the surrounding landscape.

Insights into the restoration and sustainable management of Emory oak: A southwestern cultural keystone species

Emory oak acorns are a critically important commodity for Western Apache Tribal Nations, both as a food source and also for cultural and ceremonial uses. The Apache people historically inhabited much of Emory oak's range, but these lands are now divided among many entities, with the majority of trees occurring off-reservation in public domains. Based on observations of diminished acorn production and seedling recruitment, Apache Elders called for restoration and improved management of Emory oaks on public lands to ensure the long-term availability of acorns for Western Apache Tribes. Ecological information is critical to effectively design restoration efforts and successfully manage Emory oak, but little is known about Emory oak’s current ecological status on the landscape. Here, we use Forest Inventory and Analysis (FIA) data to examine factors that influence Emory oak distribution, abundance, and demography, and relate findings to observations made by Tribal Elders. We found that Emory oak distribution was constrained by metrics related to water availability. Drought and fire occurred frequently in Emory oak habitats, highlighting the likely importance of these disturbance events in determining oak population dynamics. Emory oak growth was predicted by environmental variables related to water availability, like physiographic class and elevation, and population characteristics, like stand age and size, but not by land ownership classifications. Interestingly, no environmental variables explained patterns of seedling recruitment and mortality perhaps owing to the stochastic nature of these events and the coarse temporal scale of FIA data in AZ. Drier, warmer conditions projected by climate models was shown to reduce future suitable Emory oak habitat, particularly in central AZ. Restoration efforts should focus on increasing water availability for Emory oaks and reducing the likelihood of high intensity fires. This could be accomplished, in part, by thinning competing vegetation at Emory oaks stands and restoring historical fire regimes. Given projections that suggest drier regional climatic patterns, strategic seed augmentation aimed at enhancing population resilience through selection of drought-adapted genotypes may also be warranted. Data were insufficient to confirm Apache Elders’ observations of diminished acorn production and seedling recruitment, highlighting the need for comprehensive demographic analyses of Emory oaks in the Southwest.

Growth and genetic predisposition of induced acorn production in pedunculate oak (Quercus robur L) within 15 years of planting

The primary objective of this study was to evaluate the growth, genetic predisposition and potential for early fructification of pedunculate oak trees (Quercus robur L.) using two different planting stocks: Root Production Method (RPM®) and Cell Grown (CG). The second objective was to investigate the effect of crown clearance on acorn production. This study was undertaken between 2001 and 2016 at an experimental site at Castlearchdale in Northern Ireland initially comprising of 150 CG and 150 RPM® derived one-year old Q. robur seedlings. Both tree seedling groups were each subdivided into two groups of 75 trees based on height: CG1 (20–50 cm); CG2 (>50 cm); RPM® 1 (<76 cm) and RPM® 2 (>76 cm). Viable acorns were produced by each category of tree in the seventh year after planting: CG1 - 1 tree (1.3%); CG2 - 2 trees (2.7%); RPM®1 - 6 trees (8%) and RPM®2 - 12 trees (16%). The RPM® trees were significantly (p < 0.001) taller, thicker and more likely to show early fructification than CG trees. A weak but very highly significant correlation (r = 0.23, p < 0.001) was established between height at planting and early fructification for RPM® Q. robur trees eight years later. Crown clearance in year 14 after planting had no significant effect on acorn production in the following year within the oak tree population. The genetic analysis shows no obvious genetic groupings within the treatment groups nor genetic predisposition. A similar pattern was found for samples producing acorns versus those not producing acorns.The potential of RPM® planting stock to enhance home grown seed production in Britain and Ireland is discussed in relation to fructification dynamics of oak trees, and physiological and climatic conditions.

Improving Coastal Plain Hardwoods for Deer and Turkeys with Canopy Reduction and Fire

ABSTRACTPrescribed fire and canopy reduction are accepted forest management practices used to increase forage and cover for white‐tailed deer (Odocoileus virginianus) and wild turkeys (Meleagris gallopavo) in pine systems throughout the southeastern United States. However, use of prescribed fire to improve conditions for deer and turkeys has not been evaluated in upland hardwood forests of the Coastal Plain, and some land managers remain skeptical of the utility of fire in this ecoregion. We designed a manipulative experiment to measure deer and turkey habitat components following canopy reduction and prescribed fire in 4 upland hardwood stands in the Coastal Plain of Alabama, USA, during 2018 and 2019. Specifically, we used herbicide to kill trees with low value to deer and turkeys and retained oaks (Quercus spp.) and other species considered important as part of a forest stand improvement (FSI) operation to reduce canopy coverage. We then applied low‐intensity prescribed fire to half of each treatment unit. One unit in each replicate served as a control. We measured total understory plant coverage, biomass of deer forage, and turkey brooding cover for 2 years following canopy reduction and one year after fire. Coverage of herbaceous plants increased by 134% in FSI/Burn, and coverage of woody and semiwoody plants increased by 33% and 97%, respectively, following FSI only. Deer forage biomass was greater in both FSI and FSI/Burn compared to control, but there was no difference in deer forage biomass between FSI and FSI/Burn. FSI/Burn provided better turkey brooding cover than FSI or control. No overstory trees were killed by fire. We detected minor cambium damage to 13% of water oaks (Quercus nigra) in the FSI/Burn units; other species only showed light bark charring or no sign of burning. We recommend FSI and low‐intensity prescribed fire in Coastal Plain hardwoods to improve brooding cover for turkeys and understory forage for deer while retaining acorn production. © 2020 The Wildlife Society.

Annual and spatial variabilities in the acorn production of Quercus mongolica

BackgroundGenus Quercus is a successful group that has occupied the largest area of forest around the world including South Korea. The acorns are an important food source for both wild animals and humans. Although the reproductive characteristics of this genus are highly variable, it had been rarely studied in South Korea. Therefore, in Seoraksan and Odaesan National Parks (i) we measured the acorn production of Quercus mongolica, an overwhelmingly dominant species in South Korea, for 3 years (2017–2019), (ii) evaluated the spatial-temporal variation of acorn production, and (iii) analyzed the effects of oak- and site-related variables on the acorn production.ResultsThe annual acorn production of Q. mongolica increased 36 times from 1.2 g m−2 in 2017 to 43.2 g m−2 in 2018, and decreased to 16.7 g m−2 in 2019, resulting in an annual coefficient of variation of 104%. The coefficient of spatial variation was high and reached a maximum of 142%, and the tree size was the greatest influencing factor. That is, with an increase in tree size, acorn production increased significantly (2018 F = 16.3, p < 0.001; 2019 F = 8.2, p < 0.01). Elevation and slope also significantly affected the production in 2019. However, since elevation and tree size showed a positive correlation (r = 0.517, p < 0.001), the increase in acorn production with increasing elevation was possibly due to the effect of tree size. The acorn production of Odaesan for 3 years was 2.2 times greater than that of Seoraksan. This was presumed that there are more distribution of thick oak trees and more favorable site conditions such as deep soil A-layer depth, high organic matter, and slower slopes.ConclusionAs reported for other species of the genus Quercus, the acorn production of Q. mongolica showed large spatial and annual variations. The temporal variability was presumed to be a weather-influenced masting, while the spatial variability was mainly caused by oak tree size.

Oak growth and acorn production in southern Appalachian mature forests and shelterwood with reserves regeneration harvests

Oaks (Quercus) are economically important, and their seed (acorns) are a valuable food for many animals. Thus, forest managers must consider potential tradeoffs between oak growth and acorn production. I used 13 years of dbh growth and 17 years of acorn trapping data on 195 trees of five common eastern oak species to compare stand-level growth and acorn production between closed canopy mature forest (M) and recent shelterwood with reserves regeneration harvests (SW) (BA 27.3 ± 1.7 m2/ha in M; 5.1 + 0.8 m2/ha in SW at study establishment). I also examined treatment differences in dbh growth, crown expansion, and acorns/m2 crown at the individual tree level, using a subset of paired (by species and dbh) trees. Despite five times more oak trees and oak BA in M, average annual total acorn production/ha was only double (58,199/ha in M) that in SW (27,298/ha), and was statistically greater in M than SW for total oaks and white oak. Stand- and paired individual tree-level analyses indicated that average acorns/m2 crown and dbh growth was approximately 70% greater in SW than M for total oaks. Crown area increases were greater in SW than M for total oak (66%) and northern red oak (74%), and crown areas in SW expanded disproportionately to increases in dbh alone. In mixed-oak southern Appalachian forests, silvicultural treatments retaining 20–40 mature oaks/ha with fully released crowns will likely yield 50–100% of acorns produced/ha in mature closed canopy stands, as acorn production by residual trees increases. Retention of multiple oak species will reduce the likelihood of stand-level crop failure, as acorn production differs among species and years.

Patchy landscapes support more plant diversity and ecosystem services than wood grasslands in Mediterranean silvopastoral agroforestry systems

Plant diversity and proxy indicators of ecosystem services were assessed for three structural components of Mediterranean silvopastoral agroforestry systems: WL = cork oak woodlands, WG = cork oak wood grasslands, and OG = open grasslands. Our study was conducted in a long-term observatory located in NE Sardinia, characterized by fragmented land ownership and land use, which generates a patchy landscape that is different from the extensively studied large scale Iberian dehesas and montados. Our research question was focused on assessing whether, a “patchy” land use scenario made of the combination of WL, WG and OG or a “specialized” scenario could provide more plant diversity and ecosystem services than a “dehesa type” scenario including only WG under the same overall tree cover. The results showed that γ and β diversity, species unique to a position, C stock, cork and acorn production, Hemicryptophytes cover, nectariferous species cover, decreased and pastoral value, excellent and good forage species and legume cover, increased along the WL➔WG➔OG land use gradient. Isolated trees in WG and clearings in WL highly contributed to achieving mainly high C stock and plant diversity respectively. The results also showed that the “specialized” scenario can support higher biodiversity and better ecosystem services than the “dehesa type” scenario, but the “patchy” scenario made of all three components proved to support the highest level of both biodiversity and ecosystem services in Mediterranean silvopastoral agroforestry systems.