Oak Decline

Repeated oak decline and mortality events have occurred in the Ozark region for decades and probably longer. We sampled an age sequence of 1,259 black and scarlet oaks (Quercus velutina Lam. and Quercus coccinea Muench.) to better describe the process of oak decline and mortality in the red oak group (subgenera Erythrobalanus). Trend in basal area increment (BAI) over the most recent 40 years was used to establish three vigor classes for trees with decreasing, stable, or increasing growth (Declining, Stable, or Healthy). We compared crown condition measures with absolute BAI and boundary line BAI, a measure of radial growth adjusted for tree size. A pulse of mortality was found to occur just subsequent to the most recent drought, although decline often started decades previously. Time series of individual tree BAI suggests that half of all oak decline events were incited by one or two drought-related step-changes in growth and variance. Predisposing factors to decline generally showed significant but weak relationships with crown conditions. Surviving oaks growing in high-mortality stands had poorer crown conditions and grew more slowly than trees in low-mortality stands. When recently dead trees were accounted for, the same high-mortality stands had significantly greater predecline basal area and stocking than low-mortality stands. Thus, a less competitive growth environment may afford some buffer to drought stress before oak decline but does not appear to help afflicted stands improve their growth and vigor. FOR. SCI. 54(1):8 -20.

Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988 to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20-30 cm of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N ratio). Trees growing on soils with a high pH (≥4.00, in BaCl 2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH <4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency. Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than trees on more basic soils between 1988 and 1999. Trees ≥100 years old had significantly higher defoliation on more acidic than on more basic soils, however defoliation dynamics of these trees over 1988-99 was not related to soil acidity. Two biotic agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics.

During last years, the populations of the oak buprestid beetle Agrilm biguttatzes (Fab.) in Europe have increased. In several countries, the beetles' attacks have become a new component in oak dieback. The larvae excavate galleries under the bark of weakened trees, which are killed through the girdling. Because of the difficult diagnosis it is necessary to draw more attention to the infestations. Therefore, this paper presents a review on the literature concerning the recognition of the infestations by the insect and its bionomics.

The oak decline is probably the most severe plant health problem faced in the Mediterranean region which is one of the habitats of community interest under the EU’s environmental legal regime. More information on the role of Cerambycids species in this decay is still needed. This paper reports the apparent survival rate (Phi) and recapture rate (P) for a population of Cerambyx welensii Küster (Coleoptera cerambycidae) in a highly degraded cork oak grove near the Doñana National Park (Huelva, Spain) as calculated using the mark-capture-recapture method. High and constants in the time values of apparent survival rates for males and females are detected. The male overall recapture rate (P) exceeded that of the female group with relatively low, but significant, values. The presence of transient individuals suggests a nucleus of population with many immigrants and emigrants in the study plot. The results are used to discuss various aspects of the insect biology, and the potential effect of the gradual deterioration of the studied ecosystem on theinsect population it supports.

Incidences of oak decline have occurred repeatedly during the past three centuries as well as in the most recent decades. On the basis of historical records and dendrochronological measurements, oak decline in Central Europe has been attributed to the single or combined effects of climatic extremes (winter frost, summer drought), defoliating insects, and pathogenic fungi. Starting from a literature review, we discuss the possible roles of various abiotic (air pollution, nitrogen eutrophication, soil chemical stress, climatic extremes, site conditions) and biotic factors (insect defoliation, borer attack, infection by pathogenic fungi, microorganisms) that have been related to oak decline. On the basis of investigations on Quercus petraea and Quercus robur at three different levels (from experiments with young trees to monitoring on a supraregional scale), we suggest a conceptual model of the interaction of abiotic and biotic factors responsible for the onset of oak decline. This model should be valid for Central European oak stands at more acidic sites (soil pH (H 2 O) £ 4.2; on soils with higher pH, pathogenic Phytophthora species may contribute to oak decline). The combination of severe insect defoliation in at least two consecutive years with climatic extremes is the most significant complex of factors in the incidence of oak decline. Combined with defoliation, summer drought or winter ⁄ spring frost or both have to occur within the same year or in consecutive years to trigger major outbreaks of decline. Important additional stress factors are the following: (1) hydromorphic site conditions which, particularly in the case of Q. robur, render the trees more susceptible to drought stress as a result of an impairment of root growth in the subsoil; and (2), possibly, excess nitrogen which, in combination with drought stress, results in distinct decreases in the foliar concentrations of allelochemicals in Q. robur, thereby probably making the trees more susceptible to insect defoliation. Air pollution, soil chemical stress (including excess manganese), and nitrogen-induced nutritional imbalance do not seem to be important causal factors in the complex of oak decline. On the basis of the model, the appearance of the most recent oak decline in North-western Germany can be adequately explained.

This review attempts to assess the causal factors and their interrelations that cause decline of widespread European oak (Quercus) species. In particular, it provides an overview of recent advances in cause-effect research since 2000. The first recorded outbreak of oak decline took place in 1739-1748, and was followed by several other decline episodes, most of them occurring in the 20th century. The mortality rates differ substantially among the European regions and decline episodes; however, the decline of entire stands is a rare event. The principal causes of oak decline are the following site-unspecific factors: severe (in particular, repeated) defoliation by insect larvae, especially in combination with infection by powdery mildew, and weather extremes (summer drought, winter frost, spring frost); and the following site-specific factors: the root pathogen Phytophthora quercina (which is virulent in soils with a pH[CaCl2] value  3.5 and certain fractions of exchangeable calcium), and a distinct decrease in the groundwater level. At hydromorphic sites, intermittent soil moisture can intensify the impact of drought. At least in the temperate regions, two or more of these factors have to act in combination to cause major outbreaks of decline. Other biotic factors such as the root pathogen Collybia fusipes and the borers Agrilus biguttatus or Platypus cylindrus can contribute to the damage in later stages of decline. In the Mediterranean region, the aggressive root pathogen Phytophthora cinnamomi as well as prolonged periods of intense drought probably are capable of causing oak decline without contribution of additional factors. Other possible causal factors, whose importance still has to be corroborated, are the decrease in chemical defence compounds against leaf herbivores due to eutrophication with nitrogen, and increased ozone concentrations.

Oak-dominated forests in northwestern Arkansas have recently experienced an oak mortality event associated with an unprecedented outbreak of a native insect, the red oak borer, Enaphalodes rufulus (Haldeman). To determine whether prior drought was associated with increased E. rufulus infestation level of Quercus rubra L. trees, we employed a suite of dendrochronological measurements from Q. rubra in affected forest stands. We examined patterns of tree growth and physiological indicators of stress including a-cellulose d 13 C, intrinsic water-use efficiency (W i ) and photosynthetic discrimination (D) in Q. rubra from 1954 to 2002. Basal area increment measurements revealed that Q. rubra with lower levels of E. rufulus infestation experienced approximately 20% greater stem growth than Q. rubra more severely infested for $17 years prior to the onset of high rates of Q. rubra mortality. This trend emerged immediately following a severe drought in 1979-1981 and continued through 2002, suggesting that drought influenced E. rufulus infestation levels of some Q. rubra trees. Indicators of tree carbon and water relations (d 13 C, W i , and D) revealed no relationship with degree of E. rufulus infestation, except for D in 2000, when physiology likely was responding to the advanced stage of decline in heavily infested trees. d 13 C, W i , and D responded to drought periods as predicted early in the study period, but lost their sensitivity to drought after differences emerged in stem growth rate with degree of infestation. Though reduced stem growth in heavily infested trees suggests these trees were negatively influenced by E. rufulus infestation, the lack of infestation response of d 13 C, W i , and, for much of the study period, D, suggests that infestation had negligible influence on C-water relations. The study highlights how d 13 C and d 13 C-based parameters may not indicate variation in tree C-water relations when forest disturbances are associated with reductions in tree growth rates. #

Fire suppression has been found to dramatically change fire regimes, lead to accumulation of fuels, and alter forest composition and species abundance in the Central Hardwood Forests in the Missouri Ozarks, United States. After a half century of fire suppression, fire hazards have increased to a high level and high intensity fires are more likely to occur. We used LANDIS, a spatially explicit landscape dynamics model, to simulate the long-term effects of fire suppression on forests in Missouri Ozarks. Specifically, we examined to what extent fire suppression would affect fuel loads and fire hazards, and how fire suppression would affect forest tree species abundance. Using a spatial modeling approach, we conducted 200-year simulations of two management scenarios: (1) a fire suppression scenario circa 1990s and (2) a historic fire regime scenario prior to fire suppression, with a mean fire-return interval of 14 years. Under the fire suppression scenario, the simulation showed that both fine and coarse fuels were at a medium-high level after a few more decades of fire suppression. Fire hazard also rapidly increased to a medium-high level within a few decades. After one century of fire suppression, simulated fire intensity increased to a dangerous level, with more than 3/4 of the fires at a medium-high intensity level. Fire suppression also led to distinct changes in species abundance; the pine and oak-pine forests which used to dominate the study area prior to fire suppression were replaced by mixed-oak forests. This study suggests that it may be desirable to re-introduce frequent fire. By greatly increasing the use of fire over current management levels, our simulation suggests less accumulation of dangerous fuels, reduced fire hazard, and decreased occurrence of high intensity fires. Results imply that frequent fire would greatly increase the abundance of fireresistant species (e.g., shortleaf pine) and decrease the abundance of more fire-sensitive species such as red oaks. Such a compositional shift should also decrease the recent phenomenon of widespread oak decline events. #

We studied the effects of repeated defoliation and drought, which are considered to be most effective in triggering oak decline, on the Central-European oak species Quercus robur L. and Quercus petraea [Matt.] Liebl. Threeyear-old saplings were subjected to artificial defoliation in two consecutive years and to drought stress, applied singly or in combination. Differences in the morphological, anatomical and physiological responses to these stress factors among treatments and between species were tested in a 3-year experiment. Drought stress lowered the pre-dawn and the afternoon leaf-water potentials in both species, irrespective of additional defoliation. The relative water content of the leaves was unaffected by drought stress; but, in Q. robur, it decreased in trees subjected to defoliation and to the combination of drought stress and defoliation. When repeated defoliation and drought stress were applied within the same growing season, the leaf-to-air difference in the partial pressure of water vapour ( w) explained most of the variation in the daily integral of the stomatal conductance to water vapour (g s day sum ) in Q. petraea; however, in Q. robur, the hydraulic conductance of the twigs was the most powerful predictor variable. In the same year, the actual hydraulic conductance was correlated with g s day sum in Q. robur, but not in Q. petraea. The studied parameters of gas exchange and biomass production revealed that Q. robur recovered more rapidly from stress than did Q. petraea. We hypothesize that this is due to Q. robur's lower responsiveness to the environmental variable w and its higher responsiveness to internal hydraulic conductance compared to Q. petraea.

Isolates belonging to an undescribed Phytophthora species were frequently recovered during an oak forest soil survey of Phytophthora species in eastern and north-central USA in 2004. The species was isolated using an oak leaf baiting method from rhizosphere soil samples collected from Quercus rubra, Q. macrocarpa, and Q. phellos. This species is formally described as P. quercetorum. It is homothallic and has aplerotic oogonia and paragynous antheridia. It produces papillate sporangia (occasionally bipapillate) of ovoid-elongated shapes. Its temperature optimum for growth is ca 22.5 C with the upper limit of ca 32.5 C. P. quercetorum differs from the morphologically related P. quercina in producing distinct submerged colony-patterns, different growth-temperature requirements, and oogonial shapes and sizes. Phylogenetic analyses using seven nuclear loci supported P. quercetorum as a novel species within clade 4, closely related to P. arecae, P. palmivora, P. megakarya, and P. quercina.

Structural changes in the shrub layer were analysed in a Hungarian oak forest after the oak decline pandemics. This paper focuses on the following questions: (1) which of the woody species tolerated better the forest conditions after oak decline? (2) What are the ecological factors that explain the successful response of woody species to changes in light and thermal conditions? In the monitoring plot, the structural condition of specimens only above 8.0 m was observed. After the appearance of oak decline some Acer campestre, Cornus mas and Acer tataricum specimens appeared that reached between 8.0-13.0 m in height. Significant differences were revealed between top canopy density and foliage cover of the subcanopy and between top canopy density and mean cover of field maple. The findings of the study indicate that the forest responded to oak decline with significant structural rearrangement in the shrub layer and that three woody species compensated for the remarkable foliage loss in the top canopy. These species formed a second crown layer directly below the canopy formed by oaks.

Conservation management conflicts frequently arise when an overpopulation of a protected organism has negative effects on other valuable elements in the same ecosystem. We studied the interactions between a colony of protected tree-nesting wading birds and a remnant population of centenarian cork oaks that was part of the formerly dominant forests in the Donana Biological Reserve (SW Spain). A significant increase in the tree mortality rates has been recorded in areas that are yearly influenced by the bird colony.

We analysed a cohort of surviving trees using a gradient of nesting bird influence. Tree-nesting history, bird isotopic signature (delta(15)N), tree health-related parameters (defoliation, delta(11)C and leaf surface coverage by faeces) and several soil variables were evaluated. Bird influence was related to increased soil salinity. This increase correlated to increased water-use efficiency for the leaves and to crown defoliation, suggesting that the heavily occupied trees are under higher stress and in poorer health condition than the unoccupied ones. We tested structural equations models (SEM) that were based on hypothesised bird effects on the health of the trees. Soil-mediated effects of the nesting birds best explained the symptoms of the declining health of the trees, whereas the percent of leaves' surface that was covered by faeces did not improve the fitted SEM model.

For the reserve's managers, a challenging trade-off exists between preserving the relict trees, which have a high genetic diversity and a key ecological role in these savannah-like ecosystems, and maintaining the current nesting area for these protected, but expanding, wading birds.

Recent land-use changes in intensively managed forests such as Mediterranean coppice stands might profoundly alter their structure and function. We assessed how the abandonment of traditional management practices in coppice stands, which consisted of short cutting-cycles (10-15 years), has caused overaging (stems are usually much older than when they were coppiced) and altered their wood anatomy and hydraulic architecture. We studied the recent changes of wood anatomy, radial growth, and hydraulic architecture in two stands of Quercus pyrenaica, a transitional Mediterranean oak with ring-porous wood forming coppice stands in W-NW Spain. We selected a xeric and a mesic site because of their contrasting climates and disturbance histories. The xeric site experienced an intense defoliation after the severe 1993-1994 summer drought. The mesic site was thinned in late 1994. We studied the temporal variability in width, vessel number and diameter, and predicted the hydraulic conductivities (K h ) of earlywood and latewood. In the mesic site, we estimated the vulnerability to xylem cavitation of earlywood vessels. Overaging caused a steep decline in latewood production at a cambial age of 14 years., which was close to the customary cutting cycle of Q. pyrenaica. The diameter distribution of vessels was bimodal, and latewood vessels only accounted for 4% of the K h . Overaging, acting as a predisposing factor in the decline episode, was observed at the xeric site, where most trees did not produce latewood in 1993-1995. At the mesic site, thinned trees formed wider tree-rings, more latewood and multiseriate tree-rings than overaged trees. The growth enhancement remained 8 years after thinning. Most of the hydraulic conductivity in earlywood was lost in a narrow range of potentials, between −2.5 and −3.5 MPa. We have shown L.

• We combined stem volume increment analysis with dendroecological tools to address two unresolved issues concerning oak dieback in Mediterranean areas: early detection of changes in stand growth, and identification of mechanisms for observed growth declines. • We reconstructed productivity of a stored coppice formed by Turkey oak (Quercus cerris) to test if its growth decline was linked to climatic variability, while also accounting for age-related and sociological factors. • Drought in May–June and in prior-year late summer-autumn was negatively correlated with current growth during 1974–2006. Previous November water balance was the strongest signal. Moving Correlation Functions (11 y windows) indicated that the May–June signal remained dominant until 1996, thereafter falling to non-significant values in parallel with the May–June water balance drying trend; at the same time the previous autumn correlations reached significant values. Since 1994 there was a two-year lagged response to June water balance, suggesting that, when growth declined, loss of current-year climate signals was accompanied by the emergence of previous-year ones. • Growth and productivity of deciduous oaks in Mediterranean environments is linked to late spring-early summer hydrologic balance; at both annual and decadal timescales, oak growth decline was associated with a delayed response to climate.

Botr yosphaeria stevensii frequently has been associated with dieback and canker diseases of oak, mainly in the western Mediterranean area but more rarely in other regions. The species concept of B. stevensii has been unclear, and it is possible that some collections were identified incorrectly. A collection of fungal strains isolated from diseased oak trees and initially identified as B. stevensii was characterized on the basis of morphology and ITS nucleotide sequences. Morphology was compared with the type specimens of Physalospora mutila (ϭ B. stevensii) and its anamorph, Diplodia mutila. It was concluded that the isolates from oak differed from B. stevensii in having larger ascospores and conidia as well as different spore shapes and represented an as yet undescribed species, which is described here as B. corticola. Moreover, ITS sequence data separated B. corticola from all other known species of Botryosphaeria. Amended descriptions of B. stevensii and its anamorph are provided to differentiate B. stevensii from B. corticola and to clarify some of the earlier taxonomic uncertainties.

We studied the effects of repeated defoliation and drought, which are considered to be most effective in triggering oak decline, on the Central-European oak species Quercus robur L. and Quercus petraea [Matt.] Liebl. Threeyear-old saplings were subjected to artificial defoliation in two consecutive years and to drought stress, applied singly or in combination. Differences in the morphological, anatomical and physiological responses to these stress factors among treatments and between species were tested in a 3-year experiment. Drought stress lowered the pre-dawn and the afternoon leaf-water potentials in both species, irrespective of additional defoliation. The relative water content of the leaves was unaffected by drought stress; but, in Q. robur, it decreased in trees subjected to defoliation and to the combination of drought stress and defoliation. When repeated defoliation and drought stress were applied within the same growing season, the leaf-to-air difference in the partial pressure of water vapour ( w) explained most of the variation in the daily integral of the stomatal conductance to water vapour (g s day sum ) in Q. petraea; however, in Q. robur, the hydraulic conductance of the twigs was the most powerful predictor variable. In the same year, the actual hydraulic conductance was correlated with g s day sum in Q. robur, but not in Q. petraea. The studied parameters of gas exchange and biomass production revealed that Q. robur recovered more rapidly from stress than did Q. petraea. We hypothesize that this is due to Q. robur's lower responsiveness to the environmental variable w and its higher responsiveness to internal hydraulic conductance compared to Q. petraea.

In a recent study intended to assess the distribution of Cryphonectria parasitica in Portugal, 22 morphologically atypical orange isolates were collected in the Midwestern regions. Eleven isolates were recovered from Castanea sativa, in areas severely affected by chestnut blight and eleven isolates from Quercus suber in areas with cork oak decline. These isolates were compared with known C. parasitica and

Following the severe drought in 1999–2000 there was a widespread outbreak of oak decline in the Ozark Highlands. Over 400,000ha of dead and dying oak trees were observed by the USDA Forest Service in this region. Although oak forests that are dead can be easily interpreted from air photos or classified from satellite images, it is difficult to detect dying trees that are still green but will die back or recover in the following years. In this study, we applied a normalized difference water index (NDWI) to map the continuous forest dynamics related to oak decline. The Landsat TM image in 1992 and the ETM+ image in 2000 were processed to calculate the differential NDWI which revealed moisture variation primarily caused by the drought and the associated red oak borers. A simple thresholding method was used to map oak dying back, recovery and non-change areas in the study area. The died-back areas were extracted from the modified land use/land cover maps created by the Missouri Resource...

Conservation management conflicts frequently arise when an overpopulation of a 23 protected organism has negative effects on other valuable elements in the same 24 ecosystem. We studied the interactions between a colony of protected tree-nesting 25 wading birds and a remnant population of centenarian cork oaks that was part of the 26 formerly dominant forests in the Doñana Biological Reserve (SW Spain). A significant 27 increase in the tree mortality rates has been recorded in areas that are yearly influenced 28 by the bird colony. 29

We conducted an operational study to evaluate effect of site preparation treatments on pine reproduction density and the impact of overstory basal area and understory density on pine reproduction height and basal diameter in pine-oak stands in the Missouri Ozarks. Stands were harvested to or below B-level stocking, but patchiness of the oak decline lead to some plots having no overstory and some having over 200 ft 2 /ac basal area at the end of the study. In all stands, the midstory and understory were chainsaw felled. If stands were inadequately stocked with pine reproduction, then mechanical scarifying or prescribed burning treatments were applied to increase the density of shortleaf pine reproduction. Pine reproduction basal diameter, height, and crown class within the understory were measured three to eight growing seasons later.

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 oakdominated 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. Published by Elsevier B.V.

Dehesas cover about 3,100,000 ha in the Iberian Peninsula, and support an outstanding diversity of wildlife and flora endemisms. These open woodlands provide Spain and Portugal inhabitants with a high-quality food, derived from animal production, sustain rural population, and act as retardants of soil erosion and desertification, which are considered primary environmental concerns in the Mediterranean basin. Dehesas are considered

Cork oak (Quercus suber) forests are acknowledged for their biodiversity and economic (mainly cork production) values. WildWres are one of the main threats contributing to cork oak decline in the Mediterranean Basin, and one major question that managers face after Wre in cork oak stands is whether the burned trees should be coppiced or not. This decision can be based on the degree of expected crown regeneration assessed immediately after Wre. In this study we carried out a post-Wre assessment of the degree of crown recovery in 858 trees being exploited for cork production in southern Portugal, 1.5 years after a wildWre. Using logistic regression, we modelled good or poor crown recovery probability as a function of tree and stand variables. The main variables inXuencing the likelihood of good or poor crown regeneration were bark thickness, charring height, aspect and tree diameter. We also developed management models, including simpler but easier to measure variables, which had a lower predictive power but can be used to help managers to identify, immediately after Wre, trees that will likely show good crown regeneration, and trees that will likely die or show poor regeneration (and thus, potential candidates for trunk coppicing).

Three research areas in the Ozark National Forest, Arkansas, were chosen to investigate relationships of site and stand conditions to northern red oak, Quercus rubra L., mortality attributed to red oak borer, Enaphalodes rufulus (Haldeman), a native wood-boring beetle. Fixed vegetation plots were installed in each area on five topographic positions: north, south, east, and west-facing benches and on ridges. Red oaks were classified into three red oak borer infestation history classes, low, moderate, and high, based on crown condition and red oak borer basal emergence holes. Three red oak borer population variables, number of current generation galleries, previous generation heartwood galleries, and emerging adults, were extrapolated to the stand-level based on infestation history class and within-tree red oak borer density data derived from whole and partial-tree sampling during the 2003 red oak borer cohort. Strong explanatory site and stand variables for borer population densities and northern red oak mortality were number of northern red oak, research area, topographic position, tree species richness, and tree species diversity. Number of northern red oak was positively correlated with increased borer densities and oak mortality whereas richness and diversity were negatively correlated. Yearly re-evaluations of 527 red oaks from 2002 to 2005 revealed that 8% improved in health relative to red oak borer infestation, 48% remained the same, 31% declined, and 13% died. Numbers of living trees and healthy trees decreased in some research areas and on some topographic positions. Results revealed spatial variability in tree and stand variables, red oak borer densities, and oak mortality and elucidated stand factors associated with this insect outbreak and oak mortality event.

Oak-dominated forests in northwestern Arkansas have recently experienced an oak mortality event associated with an unprecedented outbreak of a native insect, the red oak borer, Enaphalodes rufulus (Haldeman). To determine whether prior drought was associated with increased E. rufulus infestation level of Quercus rubra L. trees, we employed a suite of dendrochronological measurements from Q. rubra in affected forest stands.

The oak decline is probably the most severe plant health problem faced in the Mediterranean region which is one of the habitats of community interest under the EU’s environmental legal regime. More information on the role of Cerambycids species in this decay is still needed. This paper reports the apparent survival rate (Phi) and recapture rate (P) for a population of Cerambyx welensii Küster (Coleoptera cerambycidae) in a highly degraded cork oak grove near the Doñana National Park (Huelva, Spain) as calculated using the mark-capture-recapture method. High and constants in the time values of apparent survival rates for males and females are detected. The male overall recapture rate (P) exceeded that of the female group with relatively low, but significant, values. The presence of transient individuals suggests a nucleus of population with many immigrants and emigrants in the study plot. The results are used to discuss various aspects of the insect biology, and the potential effect ...

Aims Oak decline is a complex phenomenon, characterized by symptoms of canopy transparency, bark cracks and root biomass reduction. Root health status is one of the first stress indicators, and root turnover is a key process in plant adaptation to unfavourable conditions. In this study, the combined effects of decline and thinning were evaluated on fine root dynamics in an oak forest adjoining the Italian Pre-Alps by comparison of acute declining trees with non-declining trees, both with and without thinning treatment of surrounding trees. Methods Dynamics of volumetric root length density (RLD V) and tip density (RTD V), root tip density per unit length of root (RTD L), diameter, branching index (BI) and mycorrhizal colonization were monitored by soil coring over 2 years as possible descriptors of decline. Key Results At the beginning of the experiment, the relationship between canopy transparency and root status was weak, declining trees having slightly lower RLD V (-20 %) and RTD V (-11 %). After a 1 year lag, during which the parameters were almost unaffected, BI and RLD V , together with tip density, tip vitality and mycorrhizal colonization, became the descriptors most representative of both decline class and thinning. Thinning of declining trees increased RLD V (þ12 %) and RTD V (þ32 %), but reduced tip mycorrhizal colonization and vitality over time compared with non-thinned trees, whereas the opposite occurred in healthy trees, together with a marked decrease in branching. After thinning, there was an initial reduction in the structure of the ectomycorrhizal community, although recovery occurred about 10 months later, regardless of decline severity. Conclusions Decline causes losses of fine root length, and a moderate recovery can be achieved by thinning, allowing better soil exploration by oak roots. The close correlation between root vitality and mycorrhizal colonization and their deterioration after thinning indicates that decline does not benefit from reduced root competition, excluding the hypothesis of limited water and nutrient availability as a possible cause of the syndrome in this forest.

Various native and exotic insects and diseases affect the forest ecosystems of the Hoosier-Shawnee Ecological Assessment Area. Defoliating insects have had the greatest effects in forests where oak species predominate. Increases in oak decline are ...

A survey of soils associated with oak species was conducted in 2003 and 2004 in Indiana, Illinois, Maryland, Michigan, Minnesota, Pennsylvania, Ohio, West Virginia, and Wisconsin to investigate the occurrence of Phytophthora spp. Soils taken from around the base of healthy and declining oak trees were flooded with H2O and Quercus robur leaflets were used as bait for Phytophthora spp. From 829 soil samples collected near trees, 21% were positive for Phytophthora spp., with 55% of the 125 sites surveyed yielding a Phytophthora sp. Phytophthora cinnamomi was the most frequently isolated species, representing 69.4% of the Phytophthora-infested sites surveyed. Other species, in decreasing order of isolation frequency were Phytophthora sp. 2, P. citricola, P. europaea, P. cambivora, P. quercina-like isolates, and Phytophthora sp. 1. No significant association was found between the presence of Phytophthora organisms and site characteristics such as latitude, elevation, soil pH, or the crow...

• We combined stem volume increment analysis with dendroecological tools to address two unresolved issues concerning oak dieback in Mediterranean areas: early detection of changes in stand growth, and identification of mechanisms for observed growth declines. • We reconstructed productivity of a stored coppice formed by Turkey oak (Quercus cerris) to test if its growth decline was linked to climatic variability, while also accounting for age-related and sociological factors. • Drought in May-June and in prior-year late summer-autumn was negatively correlated with current growth during 1974-2006. Previous November water balance was the strongest signal. Moving Correlation Functions (11 y windows) indicated that the May-June signal remained dominant until 1996, thereafter falling to non-significant values in parallel with the May-June water balance drying trend; at the same time the previous autumn correlations reached significant values. Since 1994 there was a two-year lagged response to June water balance, suggesting that, when growth declined, loss of current-year climate signals was accompanied by the emergence of previous-year ones. • Growth and productivity of deciduous oaks in Mediterranean environments is linked to late springearly summer hydrologic balance; at both annual and decadal timescales, oak growth decline was associated with a delayed response to climate.

Conservation management conflicts frequently arise when an overpopulation of a protected organism has negative effects on other valuable elements in the same ecosystem. We studied the interactions between a colony of protected tree-nesting wading birds and a remnant population of centenarian cork oaks that was part of the formerly dominant forests in the Doñana Biological Reserve (SW Spain). A significant increase in the tree mortality rates has been recorded in areas that are yearly influenced by the bird colony.
We analysed a cohort of surviving trees using a gradient of nesting bird influence. Tree-nesting history, bird isotopic signature (δ15N), tree health-related parameters (defoliation, δ13C and leaf surface coverage by faeces) and several soil variables were evaluated. Bird influence was related to increased soil salinity. This increase correlated to increased water-use efficiency for the leaves and to crown defoliation, suggesting that the heavily occupied trees are under higher stress and in poorer health condition than the unoccupied ones. We tested structural equations models (SEM) that were based on hypothesised bird effects on the health of the trees. Soil-mediated effects of the nesting birds best explained the symptoms of the declining health of the trees, whereas the percent of leaves’ surface that was covered by faeces did not improve the fitted SEM model.
For the reserve’s managers, a challenging trade-off exists between preserving the relict trees, which have a high genetic diversity and a key ecological role in these savannah-like ecosystems, and maintaining the current nesting area for these protected, but expanding, wading birds.

We combined stem volume increment analysis with dendroecological tools to address two unresolved issues concerning oak dieback in Mediterranean areas: early detection of changes in stand growth, and identification of mechanisms for observed growth declines.

Large numbers of black oak (Quercus velutina Lam.) and scarlet oak (Quercus coccinea Muenchh.) trees are declining and dying in the Missouri Ozark forest as a result of oak decline. Red oak borer-infested trees produce low-grade logs that become extremely difficult to merchandize as the level of insect attack increases. The objective of this study was to investigate the use of a resonance-based acoustic technique to evaluate the wood quality of infested red oak logs before processing as measured by grade, type and location of defects, and mechanical properties of the resulting boards. Principal compo nent and canonical correlation analyses revealed that relationships do exist between log acoustic mea surement and board grade yield, and between a linear combination of log acoustic velocity and diameter at breast height and a linear combination of board defect measurements. Although the acoustic technique was found capable of assessing wood quality at a stand level, the major advantage of the technique lies in segregating logs within the stand.

At three sites in northwestern Germany, which represent the centres of the present oak damage, root distribution and biomass beneath healthy and damaged trees of mature pedunculate oak (Quercus robur L.; Neuenburg site) and sessile oak (Q. petraea [Matt.] Liebl.; Lappwald and Sprakensehl sites) were investigated, and soil texture, bulk density, duration of waterlogging periods and the water available in the mineral soil were determined. For Neuenburg and Sprakensehl, the available soil water was related to leaf water parameters determined in a separate investigation. At the clayey and hydromorphic sites of Neuenburg and Lappwald, the measurements were performed in each one healthy and one damaged part of the site, which differed in the number of oaks with crown damage. In the damaged stand of Neuenburg, the clay content of the subsoil was higher than in the healthy stand, and the soil water availability was reduced especially in dry periods. Compared to healthy oaks of the healthy stand, the density of finest plus fine roots as well as the biomasses of finest roots were lower beneath damaged oaks of the damaged stand. With decreasing relative available soil water (actually available water in relation to water available at the saturation state), the relative leaf water content decreased in damaged, but not in healthy oaks. At Lappwald, similar differences in soil water availability between the healthy and the damaged stand were found, but had no effect on the distribution or biomass of the roots. At the sandy site (Sprakensehl), the available soil water decreased drastically during a dry period, and predawn leaf water potentials of both healthy and damaged oaks declined with decreasing relative available soil water. However, the damaged oaks were not inferior to the healthy ones with respect to root density and biomass. It is concluded that, in the damaged stand of Neuenburg, the high clay content of the subsoil, which results in prolonged periods of waterlogging, in sharp changes from waterlogging to drought and decreased water availability in dry periods, is the reason for the reduced biomass and density of roots of the pedunculate oak. Thus, in northwestern Germany, unfavourable soil water relations are considered as a factor contributing to crown damage of pedunculate oak at hydromorphic sites, but not to damage of sessile oak.

Damage and mortality data are collected as part of the US Forest Service, Forest Inventory and Analysis (FIA) ongoing assessments of the nation&#x27;s timberlands. The usefulness and value of FIA tree data in assessing historical levels of oak decline and oak mortality were ...

Shortleaf pine (Pinus echinata) is one of the most of important conifers in the Central Hardwood region both ecologically and economically. In the Ozark Highlands of Missouri and Arkansas, the presence of shortleaf pine provides an important conifer component in otherwise hardwood dominated forest types. Regional forest health issues such as oak decline and red oak borer as well as pine restoration efforts have increased interest in the species and the management of oak-pine forest types. The purpose of this paper is to provide information about the growth of shortleaf pine using one of the longest existing growth records available. Using tree-ring data collected at the Missouri Ozark Forest Ecosystem Project (MOFEP), we provide a long-term perspective of shortleaf pine growth, climate response, and regeneration. Tree-ring data from shortleaf pine remnants and cores of live trees illustrate the temporal variability in growth of shortleaf pine over the past 386 years. We developed a ...