Number Of Acorns Research Articles

Initial regeneration success of tree species after different forestry treatments in a sessile oak-hornbeam forest

Ecological, economic, and social demands triggered a shift in the management of temperate deciduous forests from rotation forestry system towards more nature-based forest management techniques such as continuous cover forestry. However, there is insufficient knowledge on the regeneration success of different tree species—especially oaks—within this management system. Through a systematic experiment, we compared the regeneration processes of a sessile oak-hornbeam forest after gap-cutting (as an element of continuous cover forestry system) to regeneration after clear-cutting, preparation cutting, and in retention tree groups (treatments of rotation forestry system). A managed, closed, mature forest was used as control. Several different aspects of the regeneration were studied: (1) seed supply of sessile oak—Quercus petraea (Matt.) Liebl., (2) species number and abundance of the natural regeneration, (3) survival and growth of individual saplings of five tree species (sessile and Turkey oak—Quercus cerris L., hornbeam—Carpinus betulus L., beech—Fagus sylvatica L., and common ash—Fraxinus excelsior L.). The number of acorns was high in closed forest, intermediate in preparation cutting and retention tree group, low in gaps, and zero in clear-cutting. Four years after the interventions, there was no detectable treatment effect on the species number of regeneration. Survival increased in every treatment compared to control, but there was no significant difference in this measure between the differently treated sites. Height growth was highest in the gaps and clear-cuts, intermediate in preparation cuts, and lowest in retention tree groups and controls. Species with different seed dispersal mechanisms responded differently to treatments: oaks were dispersal-limited in the gaps and clear-cuts, while anemochorous species (e.g., hornbeam and manna ash) were present in every treatment. The survival and growth pattern of the particular species proved to be similar, but the intensity of the response differed: shade-tolerants (hornbeam, beech, and ash) showed better survival than oaks in most treatments, and their height growth was larger. According to our results, oak regeneration establishes successfully in oak-hornbeam forests not only in the case of rotation forestry, but also during continuous cover forestry (gap-cutting). The survival and growth of the saplings are similar in cutting areas and gaps, but keeping in mind other considerations (such as preserving forest continuity, balanced site conditions, and forest biodiversity), continuous cover forestry should be preferred.

Estimation of acorn production capacity using growth characteristics of Quercus acutissima in a clonal seed orchard

Acorn production varies considerably among individual trees, years, and locations, which directly affect oak regeneration and populations of wildlife species. This study was conducted to estimate the acorn production capacities of trees in a clonal seed orchard (CSO) of Quercus acutissima by analyzing the relationship among morphological characteristics of acorns, growth characteristics of trees, and the number of acorns per tree in 9-year-old and 15-year-old trees, respectively. The age of the tree did not affect individual acorn morphological characteristics (weight, length, and width), but increased the mean acorn yield per tree from 1.26 kg at 9-year-old to 2.71 kg at 15-year-old. The number of acorns per tree showed strong positive correlations (P < 0.0001) with both crown width and crown volume of the tree. According to our equation, it was estimated that the management of tree density (to 180 trees per ha) and crown volume (to 78 m3) may have the maximum acorn production per ha. Therefore, our results suggested that optimal management of tree density and crown volume may be very effective in increasing the acorn production in CSO of Q. acutissima, which further provides an important initial step in establishing a governmental policy for seedling supply plans.

Acorn production prediction models for five common oak species of the eastern United States

AbstractAcorn production varies considerably among oak (Quercus) species, individual trees, years, and locations, which directly affects oak regeneration and populations of wildlife species that depend on acorns for food. Hard mast indices provide a relative ranking and basis for comparison of within‐ and between‐year acorn crop size at a broad scale, but do not provide an estimate of actual acorn yield—the number of acorns that can potentially be produced on a given land area unit based on the species, number, and diameter at breast height (dbh) of oak trees present. We used 10 years of acorn production data from 475 oak trees to develop predictive models of potential average annual hard mast production by five common eastern oak species, based on tree diameter and estimated crown area. We found a weak (R2 = 0.08–0.28) relationship between tree dbh and acorn production per unit crown area for most species. The relationship between tree dbh and acorn production per tree was stronger (R2 = 0.33–0.57). However, this is because larger‐dbh trees generally have larger crowns, not because they have a greater capacity to produce more acorns per unit crown area. Acorn production is highly variable among individual trees. We estimated that dbh of at least 60 dominant or codominant oak trees per species should be randomly sampled to obtain an adequate representation of the range of dbhs (≥12.7 cm dbh) in a given forest area, and achieve precise estimates when using these equations to predict potential acorn production. Our predictive models provide a tool for estimating potential acorn production that land managers and forest planners can apply to oak inventory data to tailor estimates of potential average annual acorn production to different forest management scenarios and multiple spatial scales. © 2011 The Wildlife Society.

Do ecological and silvicultural factors influence acorn mass in Holm Oak (southwestern Spain)?

The effect of orientation, location, year, and pruning treatment on mean acorn mass in two open woodland experimental locations (Huelva, South-Western Spain) of Holm Oak (Quercus ilex L. subsp. ballota [Desf.] Samp.) was analyzed during 2001–2006. Data were analyzed by using a mixed linear model, where the covariates were tree size parameters (circumference at 80 cm height, crown size), topographic position (wet index and flow length), intraspecific competition, total acorn crops per tree (weight and number), and climatic parameters. Average estimated acorn mass was 3.17 g acorn−1 in the Calañas location and 4.12 g acorn−1 in the San Bartolomé location, with significant differences between locations, among individual trees and across years. Acorns from the south sides of trees were significantly heavier than those at other positions. The effect of pruning treatment and the interactions location × treatment and treatment × year were not significant. Our study provides no evidence that pruning affects acorn mass. None of the analyzed covariates related to tree size, topographic position and intraspecific competition explained the difference among trees, suggesting that heritable factors play an important role. Specific climatic parameters during September, the most important month for acorn growth, may explain the effects of year and location × year on acorn mass. In addition, there appeared to be a “trade-off” between acorn mass and number of acorns.

Distribution of abundance and genome size variability in the grain beetle Oryzaephilus surinamensis (Linnaeus, 1758) (Coleoptera: Silvanidae)

We examined the distribution of abundance and genome size (GS, 2C-value) variability of the saw-toothed grain beetle Oryzaephilus surinamensis on the opposite slopes of the microsite “Evolution Canyon” (“EC”), Mt.Carmel, Israel. As controls, we used one sample of beetle population from a grain silo in Haifa and one sample from Upper Galilee (Sabalan Mts). The study showed that O. surinamensis is abundant in acorns of Quercus calliprinos (Palestine oak). The observed number of adults of O. surinamensis per acorn ranged from 0 to 12 at “EC” and 54% of acorns were not infected. At “EC”, O. surinamensis was more abundant on the “European, garrigue-like” north-facing slope (“ES”) than on the “African, savannah-like” south-facing slope (“AS”), reflecting the interslope differences in the number of oak trees. There was a significant positive correlation between beetle abundance and number of acorns. Both the number of acorns and the number of beetles decreased with the “ES” altitude. No significant intersample differences were found in the infestation rate (number of beetles per acorn) at “EC”. The study of the GS variability showed significant differences between the natural population at “EC” and the indoor silo pest population. Likewise, we found significant differences between males and females at both “EC” and in the silo, probably associated with the heteromorphism of the sex chromosomes. At “EC”, the slopes had significantly more effect than the intraslope stations on the female GS differences, indicating larger genomes in females at “AS” than at “ES”. The multispecies comparison of four diploid species (O. surinamensis, and the plants Ceratonia siliqua, Cyclamen persicum and Lotus peregrinus) supports the premise that increased tolerance to drought stress is associated with larger GS.

Pre- and Post-dispersal Damage to the Acorns of Two Oak Species (Quercus serrata Thunb. and Q. mongolica Fisher) in a Species-rich Deciduous Forest

A comparative study of pre- and post-dispersal damage to the acrons of two oaks,Quercus serrata Thunb. andQ. mongolica Fischer, was done over 3 years in a species-rich deciduous forest in central Japan. The numbers of acorns bored into by moth larvae and byKobuzo rectirostris (Roelofs) was low and relatively uniform each year for both oak species, but the numbers bored into byCurculio spp. varied from year to year. The proportions of acorns attacked were independent of the density of acorns produced for both oak species. The proportions of the dispersed acorns of both oak species on the forest floor that disappeared between autumn and spring were less than 27%, and were lower for species in the stand that belong to family Fagaceae. However, by the next summer, most dispersed sound acorns had been infested by moths that specialized on post-dispersal acorns.

Ability of Two Species of Oak Woodland Birds to Subsist on Acorns

Acorns are an extremely important food resource for bird populations in temperate North America (Martin et al. 1951). However, relatively little is known about the ability of animals to digest and maintain themselves on acorns. Nowhere is this ignorance more blatant than in California, where 15 species of oaks (Quercus spp.) dominate millions of hectares of land area (Griffin and Critchfield 1972, Griffin 1977), and serve (via their fruit) as a primary food resource for at least 16 species of birds (Martin et al. 1951). Of the birds dependent on acorns in foothill woodland regions of California, two of the most characteristic are the Acorn Woodpecker (Melanerpesformicivorus) and Scrub Jay (Aphelocoma coerulescens). The former is well known for its habit of caching large numbers of acorns in specially modified storage trees or granaries (MacRoberts and MacRoberts 1976). Acorns comprise over 50% of this woodpecker's total diet (Beal 1911), and are critical to overwinter survival and subsequent spring breeding (Koenig and Mumme 1987). Acorns also comprise over 50% of the fall and winter diet of Scrub Jays (Beal 1910; W. J. Carmen, unpubl. data). Despite the dependence of these species on acorns, it is unknown to what extent, if any, they are able to circumvent the effects of tannins, a key secondary metabolite present in acorns. Tannins bind with proteins (Martin and Martin 1982) and are generally accepted as defense compounds against herbivory (Bate-Smith 1973, Tempel 1981). This study was conducted in order to obtain preliminary data on the ability of Acorn Woodpeckers and Scrub Jays to overcome tannins and to maintain their body mass exclusively on acorns.

A model of episodic, abiotic dispersal for oaks (Quercus robur)

The role of flooded rivers as dispersal agents for Quercus robur L. was investigated adjacent to the Disa River in the Orange Kloof Forestry Station, Cape Peninsula, South Africa. Three months after the floods, a systematic sampling of acorns was undertaken using 100, 4 m x 4 m quadrats. It was found that those quadrats in areas that had been flooded contained more than four times the number of acorns found in the quadrats of the unflooded areas. Further, flooded areas had a greater percentage of intact acorns and seedlings. It was also found that acorns beneath an oak canopy germinated poorly and that ungerminated acorns had a higher mortality. Since the flooding of this river must be considered a rare event, the efficiency of large scale, episodic dispersal was compared to the continuous low density dispersal carried out by the alien squirrel Sciurus carolinensis Gmelin. S. Afr. J. Bot. 1985, 51: 265–269

Foraging Behavior of the Acorn Woodpecker in Belize, Central America

-The foraging behavior of the Acorn Woodpecker (Melanerpes formicivorus) was observed during the dry season in the Pine Ridge region of Belize. The birds ate a variety of foods commonly consumed by this species in temperate regions, including flying insects, oak sap, and insects obtained by surface gleaning and probing. All birds also stored large numbers of acorns in natural cavities and in woodpecker-modified holes. The woodpeckers' social organization here resembled that found in most temperate habitats. All of the birds observed lived in stable social groups that contained between two and six individuals. No solitary birds were recorded. Although nesting was not studied, it is likely that the birds breed communally in Belize as elsewhere in their range. The Acorn Woodpecker (Melanerpes formicivorus) is a common resident of oak and pine-oak woodlands from western North America southward through Central America to northern Colombia (Ridgway 1914). In temperate habitats, most individuals live in year-round groups that collectively harvest and store acorns as a winter food supply (Bent 1939). The foraging ecology of this species has been examined extensively in North America (Ritter 1929, Bent 1939, MacRoberts 1970, Roberts 1979), but has not been studied in detail elsewhere. The Acorn Woodpecker has been reported to occur in association with oaks throughout Central America and Colombia, yet considerable variation may exist in the extent to which acorns are utilized and/or stored in modified holes. For example, neither Dickey and Van Rossem (1938) in El Salvador, nor Ridgely and Gaulin (1980) in Colombia, found any evidence that this species stored or even fed on the acorns that were present at their respective study areas. Skutch (1969) reported that the Acorn Woodpeckers which he had observed in various parts of Central America did frequently feed on acorns, but that they stored the nuts in natural crevices in the bark of trees and not in individual storage holes. However, he published a photograph of a storage tree that had been found in Honduras, and both Peck (1921) and Russell (1964) reported that this species made storage holes in dead pines (Pinus spp.) in Belize (British Honduras). I examined the foraging behavior of Acorn Woodpeckers during the dry season in a tropical dry forest in Belize. I wished to determine whether or not the birds used acorns in this habitat, the extent to which the nuts were stored, and the relative importance of acorns as a food source. I also studied the social organization of the woodpeckers to determine whether the birds' behavior in this environment differed from that of North American populations studied previously by MacRoberts and MacRoberts (1976), St cey (1979), Koenig (in press) and others. STUDY AREA AND METHODS My study area was in the Pine Ridge region of Belize, approximately 28 km west of Belize City near the Western Highway. The Pine Ridge is a coastal pineoak savanna, characterized by gently sloping ridges and a well-drained sandy clay soil. The common trees in this association include Caribbean pine (Pinus caribaea), oaks (Quercus oleoides and two unidentified species), craboo (Byrsonima crassifolia) and palmetto (Acoelorraphe wrightii). Various sedges (Rhynchospora spp.) predominate in open areas. Patches of hardwood forests occur near the banks of several small streams that ran through the study area. These small forests contain many scrubby second growth species as well as larger trees typical of limestone soils throughou the lowland areas of Belize (see Wright et al. 1959, Russell 1964). I studied Acorn Woodpeckers during 240 observerhours between 15 February and 6 March 1977. The dry season in Belize normally occurs between February and May. Although rainfall records were not available at the study area, Belize City receives only about 10% of its annual rainfall (185 cm) during the dry season (Russell 1964). I observed the foraging behavior primarily of three groups, obtaining additional data from five other groups in the vicinity. I watched each group during various times of the day, and, where possible, followed individual birds as they moved through their territories. Foraging behavior was divided into six categories described below. An individual was scored as having performed a feeding pattern each time it changed from one bout of a behavior to another bout of the same or different behavior (e.g., Cruz 1977). For example, if a woodpecker was gleaning for insects, it was considered to have made one gleaning bout each time it left one tree and flew to a new tree. Sap eating was also scored in bouts: i.e., each time an individual fed on sap at one site in a particular tree, rather than