Codominant Oaks Research Articles

Restoring bigcone Douglas-fir post-fire in drought-stricken Southern California: Assessing the effects of site choice and outplanting strategies

IntroductionForest restoration is a powerful tool to combat the dual threats of drought and fire, both of which have been increasing in frequency and severity in recent years in the Western United States. The hard-hit region of Southern California is home to the endemic bigcone Douglas-fir, Pseudotsuga macrocarpa (Vasey), whose abundance and range have been impacted by multiple large fires within the last two decades.MethodsTo better understand the ecology of these trees, and thereby improve the potential for restoration in light of predicted future conditions, we outplanted 1,728 seedlings into burned areas with varying levels of pre-planting fire severity and proximity to water (near canyon bottom and upslope). Within each planting area, seedlings were planted into one of four microhabitats; under conspecifics, under the codominant oak species [Quercus chrysolepis (Liebm)], in the open (no woody canopy), or in the open within a microsite feature such as a log, rock or a small shaded hole. At each site and within each microhabitat, half the seedlings were treated with oak-soil amendments (soil from under the oak) and half with spring watering (4 months after planting). To better understand the influence of outplanting conditions, we tracked the survival of the seedlings over the next two years.Results and discussionShort-term (March to June) survivorship following planting was quite high and the most significant die-off of seedlings occurred during the first dry season (June to November) despite strong droughts in the second and third dry seasons. Overall, only 7.3% (127 of 1,728) of seedlings survived. Seedling success depended strongly on the microhabitat and summer watering, though not in necessarily intuitive ways. Seedlings that received supplemental water during the first summer did worse than unwatered seedlings. The most successful microhabitats for planting were open sites with microsite features and sites underneath canyon live oak, while sites under mature bigcone Douglas-firs had the lowest rates of survival. Position on the slope had no effect on outcomes and soil amendment had a weak negative effect on seedling survival.

Condition, protection and maintenance of age-old pedunculate oak trees in Feofania forest

Large old trees are significant elements of forests, arboretums, botanical gardens and parks and perform a number of unique functions contributing to ecosystem integrity and biodiversity. At the same time human activities such as compaction of topsoil layers, deterioration of soil permeability and soil aeration drive the decline of large old trees. The human impact is also exacerbated by plants inevitable physiological age-specific changes. The presence of such old trees in urban environments brings great scientific promises enhancing a social, cultural and historical forest value, although these benefits increase responsibility for trees maintaining. Regarding old-growth trees historical, cultural, and environmental significance and their overall vulnerability, the individual-by-individual tree protection measures are required. Pedunculate oak (Quercus robur L.) is among the most widespread long-lived species in Europe, in particular in Ukraine. In Feofania (or Theophania) forest, that is an oak-hornbeam forest located in southern part in Kyiv, the age of the oldest oak trees reaches about 300 years. In this article, we aim to estimate vitality, overall condition, and recreational digression stages of pedunculate oak trees and to develop the recommendations to maintain and extend trees longevity in Feofania forest. We estimate the stages of recreational digression and vitality using an approach of Hensiruk et al. (1987) and Sanitary Regulations in forests of Ukraine (1995) respectively. The dendrochronological analysis is performed on core samples from sixteen age-old pedunculate oaks in order to determine their exact cambial age and to evaluate their growth rates. We use at least two cores per tree extracted at a height from 0.5 m to 1.3 m above ground level with an increment borer. The tree-ring widths are measured using AxioVision (Carl Zeiss) software to the nearest 0.01 mm. To identify false rings we employ stereomicroscope MBS-1. The individual tree-ring series are cross-dated, standardized and checked using the COFECHA program. Then we determine exact cambial age of oak trees as number of tree-rings in individual series. To estimate the age of trees with cores without pith we use a graphical method. The analyze is performed on 42 increment cores containing 7335 annual rings formed in the period from 1746 to 2016. Measured diameter of the age-old oaks ranges from 57.6 cm to 165.2 cm. The longest chronological series contains 271 years. The age of studied trees varies from 202 to 275 years averaging 175 years and radial growth ranges from 1.07±0.400 mm to 2.85±1.487 mm averaging 1.95±0.792 mm. In recent years the reduction of radial growth isn’t observed, although in a long time interval in five studied trees the rings width not exceeds the individual series average value. However, the growth rate reducing could not be regarded as critical for trees vitality because it is above 10 % of the average value yet. The evaluated mean increment coefficient is 5.13±1.482 years in cm that allows to estimate the age of dominant and codominant oaks in the association of Galeobdoloni luteae-Carpinetum in other forests. The estimated vitality is mostly of 6–7 points. Five oaks are in «satisfactory condition», nine oaks are «weakened», one oak is «very weakened» and one tree is «dying». «Weakened» trees are with mechanically damaged stem and are often suffered from leaves defoliation caused by Acrocercops brongniardella and Microsphaera alphitoides. Regarding wood samples maintenance, the «dying» oak stem is found rotted in its center. The recreational digression is at the stage 1–4. For eight oaks it is at the first stage, for four oaks at the second stage, for two oaks at the third stage and for two oaks at the fourth stage with 60 % destruction of the understorey. The number of age-old Q. robur trees is limited, thus measures to care could consider individual tree-specific features. Given trees vitality and stages of recreational digression, we develop the guidelines to preserve and extend trees longevity. We also propose to include four old-growth oaks in the list of monumental plants.

Advanced Oak Seedling Development as Influenced by Shelterwood Treatments, Competition Control, Deer Fencing, and Prescribed Fire

Advanced northern red oak (Quercus rubra) seedlings in an 85-year-old forest located in north-central Pennsylvania were observed for 10 years after manipulation of available sunlight by shelterwood treatments, reduction of interfering plants by broadcast herbicides and/or a single prescribed fire, and reduction of deer damage by fencing. Twenty-four treatment combinations including untreated controls were studied on 72 permanent plots. The key to sustainable oak regeneration is to enhance both survival and growth of the advanced oak seedlings several years before a planned overstory harvest. In this study, survival and growth of 4,235 tagged oak seedlings were greatest in plots that received an overstory shelterwood harvest or midstory removal to increase sunlight, plus mist-blown herbicides to reduce interfering plants and fencing to reduce deer browsing. The overstory shelterwood harvest and midstory removal treatments reduced basal area by 30 and 12%, respectively. The prescribed fire treatment reduced survival because of the small size of the seedlings at the time of the burn. Published dominance probabilities were applied to the density and size of seedlings present after 10 years to compare the predicted number of codominant oaks resulting from the various treatments. Predicted success was greatest in fenced plots that received herbicide reduction of interfering plants and either the overstory shelterwood harvest or midstory removal treatments.

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.

Una aproximación ecológica a la silvicultura del roble:síntesis de 50 años de investigación en ecosistemas de roble en Norteamérica

La revista Colombia Forestal publica manuscritos originales en temáticas del campo forestal y diversos aspectos de los recursos naturales y del medio ambiente, los cuales se discriminan en las categorías de artículo de investigación, de revisión, de reflexión y notas técnicas de acuerdo con lo estipulado por COLCIENCIAS para las publicaciones científicas. De acuerdo a la clasificación de áreas científicas de la Organización para la Cooperación y el Desarrollo Económico (OCDE), la revista Colombia Forestal pertenece al gran área de Ciencias Agrícolas(4), área de Agricultura, Silvicultura y Pesca(4A) y a la disciplina Forestal (4A02).

Intensity of precommercial crop tree release increases diameter growth and survival of upland oaks

In 1988, seven study areas were established in Connecticut to examine the effects of precommercial crop tree release on development of sapling red oaks ( Quercus rubra L.) (n = 1250). Crown class at canopy closure, competition from adjacent trees for growing space and limited resources, and interaction of these factors were major determinants of survival, upper canopy persistence, and diameter growth over the 18 year period studied. Complete release from competition of neighboring trees, but not partial release, increased survival of intermediate and codominant stems. Complete release did not increase survival of oaks in the dominant crown class. Few intermediate and no suppressed oaks ascended into the upper canopy without crop tree release. Complete release doubled the proportion of codominant trees that remained in the upper canopy and increased the proportion of intermediates that ascended into the upper canopy. Complete release increased 18 year diameter growth only for dominant and codominant oaks. Because precommercial crop tree release simultaneously increases the probability that high-quality stems of desired species will be present in the mature stands and increases the diameter growth of those stems, this technique should be considered in stands with low oak densities.

The role of environmental factors in oak decline and mortality in the Ozark Highlands

Oak decline is a chronic problem in Missouri Ozark forests. Red oak group species are most susceptible and decline is reportedly more severe on droughty, nutrient-poor sites. However, it was not clear whether greater decline severity was caused by poor site conditions or is simply due to the greater abundance of red oak group species found on poorer sites. We conducted this study to determine whether oak decline severity in oak-dominated Missouri Ozark forests is related to factors strongly influencing site quality including soil, landform position, and slope-aspect. We monitored the survival of 6606 dominant or co-dominant oak trees for 10 years and surveyed crown dieback on more than 1995 oak trees during a single year to determine if mortality and the presence of decline symptoms were related to site factors. Analysis confirmed that red oak group species had more crown dieback and greater mortality than did white oak group species. We also found greater red oak mortality on upper slope positions and where soils were gravelly and low in base cations. However, the abundance of red oaks was also greater in these same locations. Further analysis showed that if the initial abundance of red oaks was included as a covariate in the model, the site factors no longer were significant effects related to oak mortality. Moreover, we found that frequency of oaks exhibiting crown dieback was the same or sometimes greater on high quality sites. These findings show that red oak mortality is more prevalent on droughty and nutrient-deficient sites because red oak group species are more abundant there. Rather than simply predisposing oaks to decline, droughty and nutrient-deficient site conditions most likely favored the establishment and growth of red oaks following the extensive logging during the early 1900s. The extensive oak decline occurring on droughty and nutrient-deficient soils today appears to due to the high abundance of mature red oak group species on these sites.

Inter- and intraspecific variation in the response of photosynthesis to elevated [CO2] in a Florida scrub oak community

Understanding inter- and intraspecific responses to rising [CO2] is critical for assessing possible future shifts in competition and species dominance, and for accurately predicting future carbon exchange in forest ecosystems. Two clonal, co-dominant evergreen oaks within a Florida scrub-oak ecosystem have regrown entirely under elevated [CO2], providing a rare opportunity to assess inter- and intraspecific variation during canopy closure. Photosynthesis was measured with an open-gas exchange system to assess acclimation of photosynthetic capacity in two co-dominant oaks. There was no acclimatory loss of photosynthetic capacity in Quercus myrtifolia; therefore, with decreased photorespiration in elevated [CO2], a 72% stimulation of net photosynthetic rate was observed. Quercus geminata showed a large acclimatory loss of photosynthetic capacity sufficient to offset any stimulation of light-saturated net photosynthesis due to decreased photorespiration. The photosynthetic rate of Q. geminata leaves grown and measured at elevated [CO2] was no higher than leaves grown at ambient [CO2]. Q. myrtifolia also exhibited an increase in photosynthetic nitrogen use efficiency, which was still present at canopy closure. Intraspecific variation in the response of photosynthesis to elevated [CO2] exists in both species. The role that individual genotypes play in that variation is currently unknown. DNA microsatellite analysis of Q. myrtifolia and Q. geminata is being used to estimate genetic distances between individuals. The results show that at canopy closure in a woody community, elevation of [CO2] causes a substantial difference in the capacity of co-dominants to acquire carbon and energy, with important implications for fitness and future composition of this community.

An evaluation of standard oak tree growth in Ruislip woods, West London

Tree-ring studies on dominant and co-dominant oak standards from four woodlands on the western fringes of London were studied in relation to known historical and meteorological conditions. Whilst previous studies suggested a decline in oak growth in recent decades, this was not apparent from this study. Major recruitment periods for the large oaks were determined. The sites had differing responses to known drought years. Coppicing of the undergrowth was found not to greatly influence the growth of the remaining standard trees on all occasions, although one woodland showed some growth release following recent coppicing. Records of lichens for each woodland were used to assess changing pollution levels at the sites.

An evaluation of standard oak tree growth in Ruislip woods, West London

Tree-ring studies on dominant and co-dominant oak standards from four woodlands on the western fringes of London were studied in relation to known historical and meteorological conditions. Whilst previous studies suggested a decline in oak growth in recent decades, this was not apparent from this study. Major recruitment periods for the large oaks were determined. The sites had differing responses to known drought years. Coppicing of the undergrowth was found not to greatly influence the growth of the remaining standard trees on all occasions, although one woodland showed some growth release following recent coppicing. Records of lichens for each woodland were used to assess changing pollution levels at the sites.

Red maple dynamics in Appalachian hardwood stands in West Virginia

The growth strategies red maple (Acer rubrum L.) used to attain current overstory canopy positions were investigated in two West Virginia Appalachian hardwood stands. In both stands, red maple comprised a small percentage of overstory basal area but was the most abundant understory species. The stands originated after a stand-replacing disturbance around 1930. During stand initiation, red maple invaded the sites for 10-15 years longer than most other species; however, all of the codominant red maples sampled were similar in age to other codominant species. Twenty-seven percent of stem-analysed codominant maples were 1-4 years older than the disturbance and may have originated as advanced reproduction. One sampled codominant maple had been overtopped for 20 years. Other codominant maples had height growth rates similar to codominant oaks (Quercus sp.). Even at advanced ages, understory maples showed increased height growth rates in response to small canopy disturbances. Red maple's understory persistence suggests that partial harvesting may release these individuals and promote greater proportions of overstory maples in the future.

Silvicultural Opportunities Ten Years After Clearcutting Central Hardwoods

Abstract Natural reproduction in central hardwoods 8 to 13 years after clearcutting is assessed for stands in southern Illinois. Abundant reproduction for management of valuable hardwoods is present on all sites. There are more valuable hardwood stems per acre on the dry sites, with smaller average dbh, than on the mesic sites. Better oak reproduction is found on the dry sites. There are an average of 202 dominant or codominant oak stems per acre on the dry sites compared to 42 on the mesic sites. Valuable timber species reproduction can provide most of the crop trees and trainers; TSI will generally be required on mesic and dry sites. North J Appl For 5 22-25, March 1988

Direct-Seeded Cherrybark and Shumard Oaks Battle Natural Regeneration through 10 Years

Abstract Acorns of Shumard (Quercus shumardii Buckl.) and cherrybark (Quercus falcata var. pagodifolia Ell.) oaks were direct seeded in a 3-acre opening created by cutting and removing all trees ≥ 1.0 in. dbh from a forest in the silty uplands. Field germination of winter-sown acorns was 42% for cherrybark and 55% for Shumard, about twice that of spring-sown acorns. After 10 years, average height of co-dominant trees was 23.6 ft. for Shumard and 27.0 ft. for cherrybark; average dbh was 1.5 in. for both species. Dominants and codominants in the competing natural stand averaged 40 ft. tall and 3.5 in. dbh. Only 5% of the seed spots had oak in a free-to-grow position; most codominant oaks were on higher, drier sites where competition was less severe. On better sites a number of intermediate oaks are still developing, but their future is yet to be determined.