Response of balsam fir and hemlock roots to injuries

Drill wounds in balsam fir and hemlock roots activated the nonspecific resistance mechanisms of compartmentalization in wood and necrophylactic periderm in bark. Tangential bands of resin ducts localized around the wounds constituted the barrier zones in the secondary xylem of conifer roots. Barrier zones were more extensive in roots which showed symptoms characteristic of invasion by fungi and bacteria after wounding. This observation supports an expanded definition of barrier zones; barrier zones may form not only in response to mechanical wounds but also in response to xylem injury caused by pathogens. Multiple bands of resin ducts were common in young xylem when bark lesions developed around wounds. Necrophylactic periderms isolared dead bark from living bark. Development of phellem cells with dark contents and thick suberized walls, typical of exophylactic periderm, followed initiation of necrophylactic periderm. The wound responses were similar in both balsam fir and hemlock.     

Factors involved in alleviating water stress by partial crop removal in pear trees

We studied the relief of water stress associated with fruit thinning in pear (Pyrus communis L.) trees during drought to determine what mechanisms, other than stomatal adjustment, were involved. Combinations of control irrigation (equal to crop water use less effective rainfall) and deficit irrigation (equal to 20% of control irrigation), fruit load (unthinned and thinned to 40 fruits per tree) and root pruning (pruned and unpruned) treatments were applied to pear (cv. 'Conference') trees during Stage II of fruit development. Daily patterns of midday stem water potential (Psi(stem)) and leaf conductance to water vapor (g(l)) of deficit-irrigated trees differed after fruit thinning. In response to fruit thinning, gl progressively declined with water stress until 30 days after fruit thinning and then leveled off, whereas the effects of decreased fruit load on Psi(stem) peaked 30-40 days after fruit thinning and then tended to decline. Soil water depletion was significantly correlated with fruit load during drought. Our results indicate that stomatal adjustment and the resulting soil water conservation were the factors determining the Psi(stem) response to fruit thinning. However, these factors could not explain differences in daily patterns between g(l) and Psi(stem) after fruit thinning. In all cases, effects of root pruning treatments on Psi(stem) in deficit-irrigated trees were transitory (Psi(stem) recovered from root pruning in less than 30 days), but the recovery of Psi(stem) after root pruning was faster in trees with low fruit loads. This behavior is compatible with the concept that the water balance (reflected by Psi(stem) values) was better in trees with low fruit loads compared with unthinned trees, perhaps because more carbon was available for root growth. Thus, a root growth component is hypothesized as a mechanism to explain the bimodal Psi(stem) response to fruit thinning during drought.     

致伤类型与树皮含水量对肉桂枝枯病发病程度的影响

对二年生肉桂枝条采用不同致伤方式接种发现，深刻伤引起发病的程序最严重，其次为浅刻伤，烫伤和针刺伤，病害程度与致伤类型关系密切，无伤接种不产生症状，但对嫩梢接种引起发病，枝条树皮相对含水量与病害程度显著相关，枝条失水愈多，发病愈严重，防止伤口，减轻干旱可对控制肉桂枝枯病的发生起积极作用。     

Limited response of ponderosa pine bole defenses to wounding and fungi

Tree defense against bark beetles (Curculionidae: Scolytinae) and their associated fungi generally comprises some combination of constitutive (primary) and induced (secondary) defenses. In pines, the primary constitutive defense against bark beetles consists of preformed resin stored in resin ducts. Induced defenses at the wound site (point of beetle entry) in pines may consist of an increase in resin flow and necrotic lesion formation. The quantity and quality of both induced and constitutive defenses can vary by species and season. The inducible defense response in ponderosa pine is not well understood. Our study examined the inducible defense response in ponderosa pine using traumatic mechanical wounding, and wounding with and without fungal inoculations with two different bark beetle-associated fungi (Ophiostoma minus and Grosmannia clavigera). Resin flow did not significantly increase in response to any treatment. In addition, necrotic lesion formation on the bole after fungal inoculation was minimal. Stand thinning, which has been shown to increase water availability, had no, or inconsistent, effects on inducible tree defense. Our results suggest that ponderosa pine bole defense against bark beetles and their associated fungi is primarily constitutive and not induced.     

Anatomical-based defense responses of Scots pine (Pinus sylvestris) stems to two fungal pathogens

We investigated the cellular responses of stem tissues of mature Scots pine (Pinus sylvestris L.) trees to inoculations with two fungal pathogens. The bark beetle vectored fungus, Leptographium wingfieldii Morelet, induced longer lesions in the bark, stronger swelling of polyphenolic parenchyma cells, more polyphenol accumulation and increased ray parenchyma activity compared with the root rot fungus, Heterobasidion annosum (Fr.) Bref., or mechanical wounding. Axial resin ducts in the xylem are a general feature of the preformed defenses of Scots pine, but there was no clear induction of additional traumatic axial resin ducts in response to wounding or fungal infection. The anatomical responses of Scots pine to pathogen infection were localized to the infection site and were attenuated away from bark lesions. The responses observed in Scots pine were compared with published studies on Norway spruce (Picea abies (L.) Karst.) for which anatomically based defense responses have been well characterized.     

Methyl jasmonate induces changes mimicking anatomical defenses in diverse members of the Pinaceae

Conifers have defenses such as the production of phenolic compounds and resins that can be induced by bark beetles and other invading organisms, but the signaling agents involved are unknown. The anatomical effects of methyl jasmonate (MJ), a potent inducer of certain plant defenses, were compared with wounding of the bark of 12-15-year-old trees of five conifer species. Wounding in all species resulted in tissue necrosis and wound periderm development immediately around the wound site. One cm from the wound, swelling of phloem polyphenolic parenchyma cells and phenolic accumulation were observed in Pseudotsuga menziesii (Mirb.) Franco, Picea pungens Engelman, Larix occidentalis Nutt. and Pinus monticola Douglas ex D. Don, but not in Taxus brevifolia Nutt. Traumatic resin ducts were formed in response to wounding in three species of Pinaceae, but not in P. monticola, which formed irregular clusters of cells rather than ducts. Taxus brevifolia did not form resin ducts in response to either wounding or MJ treatment. In the Pinaceae species studied, surface application of 100 mM MJ caused similar anatomical changes to those observed in response to wounding, including phenolic accumulation, cell swelling and traumatic resin duct formation, but it did not induce a wound periderm. Traumatic resin ducts differed in size among the study species, ranging from small in L. occidentalis to very large in P. menziesii. In P. menziesii, P. pungens and L. occidentalis, traumatic resin ducts were more abundant after MJ treatment than after wounding. We conclude that the octadecanoid pathway is likely involved in defense responses in stems of the Pinaceae, but not necessarily in other taxa.     

Mechanical injury and fungal infection induce acquired resistance in Norway spruce

Norway spruce trees (Picea abies (L.) Karst.) pretreated by wounding and fungal infection showed highly enhanced resistance to a subsequent challenge inoculation with the pathogenic bluestain fungus Ceratocystis polonica (Siem.) C. Moreau. This is the first time the effectiveness of the constitutive and inducible defenses has been shown to depend on prior wounding and infection in conifers, although such acquired resistance has previously been found in several angiosperms. Trees that were pretreated with a combination of 12 bark wounds (1.6 x 10 cm), four fungal inoculations and four sterile inoculations 1-15 days before mass inoculation with C. polonica at 400 inoculations per square meter over a 0.8 m stem section had significantly shorter necroses in the phloem, less bluestained sapwood, and less dead cambium than untreated control trees. Pretreatment with four fungal or sterile inoculations alone did not lead to enhanced resistance. Pretreatment by bark wounding alone seemed to provide an intermediate degree of resistance compared to bark wounding, fungal inoculations and sterile inoculations combined. All trees had a marked increase in the number of resin ducts in the year of inoculation compared with previous years, suggesting that formation of traumatic resin ducts play an important role in the development and maintainance of enhanced resistance.     

Nitrogen absorption,translocation and distribution from urea applied in autumn to leaves of young potted apple (Malus domestica) trees

We studied the absorption, assimilation, translocation and distribution of nitrogen (N) from urea applied in autumn to leaves of 1-year-old potted Fuji/M26 apple (Malus domestica Borkh) trees. In early October, all leaves of each tree were painted with either 3% urea (enriched to 10 atom % with 15N) or water (control trees). Four trees were harvested before the treatment and N and amino acid contents were determined. Four trees from each treatment were harvested at 2, 4, 7, 10, 15 and 20 days after urea or water application. Total N, amino acids and 15N in leaves, bark, xylem, shank and roots were analyzed to determine uptake and mobilization of N from urea. Most uptake of 15N by leaves occurred during the first 2 days following application of urea. The mean rate of absorption during these 2 days was 0.29 g m-2 day-1. Amino acids in leaves, bark and roots increased significantly after urea application compared with control values. The highest concentrations of amino acids in leaves and bark occurred 4 days after application, whereas the highest concentrations of amino acids in roots occurred 10 days after application. Total 15N content in leaves peaked 2 days after urea application and then decreased, whereas 15N content in roots and bark increased throughout the experiment. Total 15N content in xylem and shank was low. Leaves absorbed 35% of the 15N applied as urea, and 63.6% of absorbed 15N was translocated out of leaves within 20 days after urea application. We conclude that N from urea was converted to amino acids in leaves after foliar application in autumn, and roots and bark were the main sinks of N from urea applied to leaves.     

Changes in host chitinase isoforms in relation to wounding and colonization by Heterobasidion annosum: early and strong defense response in 33-year-old resistant Norway spruce clone

We studied the defense reactions of 33-year-old susceptible and resistant clones of Norway spruce (Picea abies (L.) Karst.) to the major root-rot fungus Heterobasidion annosum (Fr.) Bref. and determined if tissue cultures can be used as a model system for studying defense responses of mature trees at the molecular level. Quantitative PCR analysis of genomic DNA obtained from samples taken at different times along the lesion length in living bark indicated that the fungus was present in higher amounts and extended further into the host tissue in the susceptible clone than in the resistant clone. In protein extracts from the same lesion samples, there were differences in temporal and spatial changes in host chitinase isoform profiles between the resistant and susceptible clones. Host chitinase isoforms with pI values approximately 4.8, 4.4 and 3.7 increased more during the first 7 days after wounding and inoculation and extended further along the lesion length in the resistant clone than in the susceptible clone. These results suggest that the time from wounding and infection to induction of defense-related expression is shorter in the resistant clone indicating a more efficient host defense response than in the susceptible clone. Tissue cultures from the same clones were not resistant to H. annosum and showed no difference in the timing of the increase in chitinase isoforms in response to the pathogen. However, tissue cultures from both clones showed an increase in chitinase isoforms within 6 to 24 h past inoculation, indicating that increased chitinase expression in response to the pathogen is part of a general defense response common to both mature clones and tissue cultures.     

Influence of water table decline on growth allocation and endogenous gibberellins in black cottonwood

Cottonwoods occur in riparian areas where water table depth generally varies with the elevation of the adjacent river. Plant adaptation to the riparian zone requires the coordination of root elongation to maintain contact with the water table during the summer decline. We investigated the effects of rate of water decline on growth allocation and concentrations of endogenous gibberellins (GAs) in black cottonwood (Populus trichocarpa Torr. & A. Gray ex Hook.) saplings. Rhizopods were used to achieve water decline rates of 0, 2 and 4 cm day(-1). Root elongation approximately doubled in response to the 2 cm day(-1) treatment, whereas leaf area was reduced. A water decline rate of 4 cm day(-1) led to water stress, as evidenced by reduced growth, increased leaf diffusive resistance, decreased water potential, and leaf senescence and abscission. Endogenous GAs were extracted, purified and analyzed by gas chromatography-selected ion monitoring with internal [(2)H(2)]GA standards. Across the sampled plant organs, GAs were generally highest in shoot tips and sequentially lower in basal stems, root tips, leaves and upper roots; GAs were thus abundant in rapidly growing tissues. Of the GAs measured, GA(1) tended to predominate, followed sequentially by GA(3), GA(8), GA(19), GA(20), GA(29) and GA(4). There was little relationship between GA concentration and growth allocation across the water table decline treatments, although GA(8) was consistently reduced in plants experiencing water table decline. Because GA(8) is the final gibberellin in the metabolic sequence, it might be useful for assessing historic patterns of GAs and growth rate. This study demonstrated changes in growth allocation in response to water table decline, but provided little evidence that endogenous GAs play a primary role in the regulation of root elongation in response to water table decline.     

Effects of soil water deficit on gas exchange characteristics and water relations of orchard lychee (Litchi chinensis Sonn.) trees

Eight-year-old lychee (Litchi chinensis Sonn.) trees, cv. 'Bengal,' growing in krasnozem soil were subjected to soil water deficit from one month before flowering until harvest by covering the ground with polyethylene sheeting and withholding irrigation. The ratio of daytime stomatal conductance of unirrigated to irrigated trees decreased 20% during the three months of increasing water deficit. Predawn leaf water potentials of irrigated trees averaged about -0.3 MPa throughout the period, whereas they declined progressively to -0.9 MPa in unirrigated trees. Minimum daytime leaf water potential in the unirrigated trees decreased from -1.0 to -1.1 MPa at the beginning of the drought period to -2.2 to -2.4 MPa after three months, and calculated whole-plant conductance did not change with decreasing availability of water. The calculated soil-root water potential declined to less than -1.0 MPa in unirrigated trees. Capacitance effects on the relationship between leaf water potential and transpiration were significant only at low transpiration rates. Although unirrigated trees reduced soil water content at 0-30 cm depths to an equivalent water potential of -1.0 MPa, fruit shedding was significantly less than in irrigated trees. Water deficit had no effect on the fresh weight of pericarp, but caused increased seed size and decreased fresh weight of flesh, resulting in fruit from unirrigated trees being 16% lower in total fresh weight per fruit than fruit from irrigated trees.     

Detection of a chitinase-like protein in the roots of Douglas-fir trees infected with Armillaria ostoyae and Phellinus weirii

Protein was extracted from root bark of 11- and 25-year-old interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees that were naturally infected with Armillaria ostoyae (Romagnesi) Herink. The proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Root bark tissue adjacent to infected areas had a significantly higher protein concentration than healthy tissue (P < 0.05), whereas the protein concentration of infected tissue was consistently lower (P < 0.05) than that of healthy tissue. The SDS-PAGE profiles of healthy, infected, and adjacent-to-infected root bark tissues revealed significant differences in concentrations of a 29.3-kDa protein. The N-terminal amino acid sequence of the 29.3-kDa protein displayed significant homology (P = 0.013) to a basic endochitinase. Use of a polyclonal antibody raised against the 29.3-kDa putative endochitinase-like protein (ECP) indicated differences in the quantities of ECP in healthy roots compared with roots infected with A. ostoyae in 11- and 25-year-old interior Douglas-fir trees. The antibody was also used to screen for the presence of the 29.3-kDa protein in roots of 24-year-old coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) trees that were artificially inoculated with and colonized by Phellinus weirii (Murr.) Gilbn. The amount of ECP was elevated in root bark of coastal Douglas-fir in response to P. weirii infection, although in lower quantities relative to those found in the A. ostoyae-interior Douglas-fir pathosystem. The sequence homology of the ECP with a basic chitinase, together with its increased synthesis in response to two fungal pathogens, indicate a possible role for this protein in the defense of Douglas-fir against fungal pathogens.     

Intra- and inter-provenance variability in phloem phenols of Picea abies and relationship to a bark beetle-associated fungus

One hundred Norway spruce (Picea abies (L.) Karst.) clones (three ramets per clone) were analyzed for phloem phenol composition and concentration before and 10 days after wound inoculation with sterile malt agar. Fifty clones (Experiment 1) belonged to the same provenance, whereas the remaining clones (Experiment 2) belonged to five provenances from three geographic areas. In Experiment 2, two additional ramets from the same clones were mass inoculated with Ceratocystis polonica (Siem.) C. Moreau to quantify the resistance of each clone. Tree response to wound inoculations was characterized by increased catechin concentration in both experiments, accompanied by increases in astringin and decreases in piceid in Experiment 1. In both experiments, we observed a diverse group of phenolic compounds whose concentrations increased (catechin, astringin) or did not vary (taxifolin glucoside) in response to wound inoculations, whereas concentrations of a homogeneous group of stilbene compounds decreased (piceid) or did not vary (isorhapontin, unidentified stilbene). In Experiment 2, provenances from the alpine and Hercynian-Carpatic areas differed from provenances from the Baltic area with respect to the relative importance of these two groups of compounds, further indicating that the two groupings of phenolic compounds structure the Norway spruce populations. Eighty days after mass inoculation, the percentage of healthy sapwood, which was taken as a measure of tree resistance, indicated that clones from the Baltic area were less resistant to mass inoculations than clones from the alpine and Hercynian-Carpatic areas. We conclude that the degree of resistance of Norway spruce trees to mass inoculations with a bark beetle-associated fungus can be predicted based on the diversity of constitutive phloem phenols and the ability to induce phenol synthesis in response to wounding.     

Planting stress in newly planted jack pine and white spruce. 1. Factors influencing water uptake

Bareroot jack pine (Pinus banksiana Lamb.) seedlings (2 + 0) and bareroot white spruce (Picea glauca (Moench) Voss) transplants (1 1/2 + 1 1/2) were taken from cold storage and planted on a clearcut forest site in northeastern Ontario on several dates between May 6 and June 5 during which period soil temperature at 15 cm depth increased from 0 to 18 degrees C. Additional cold-stored trees were transferred to a greenhouse where they were grown in pots for 0, 7 or 28 days and then placed with their roots in aerated water maintained at one of a range of constant temperatures between 0 and 22 degrees C. In both species, daytime xylem pressure potentials (Psi(x)) and needle conductances (g(wv)) decreased with decreasing soil or water temperature. At all root temperatures, g(wv) was lower, and Psi(x) higher, in jack pine than in white spruce. After 28 days in the greenhouse, g(wv) of jack pine seedlings, and Psi(x) of white spruce, was higher than in plants just removed from cold storage. In both species, water-flow resistance through the soil-plant-atmosphere continuum (RSPAC) increased as root temperature decreased. At all root temperatures, RSPAC was higher in plants just removed from cold storage than in plants grown in the greenhouse for 28 days, during which time many new unsuberized roots were formed. At root temperatures above 10 degrees C, RSPAC of both species was higher in trees newly planted in mineral soil than in trees with roots in aerated water; presumably because the roots of planted trees had limited hydraulic contact with the soil. On the day following removal from cold storage, relative plant water flow resistance increased, in both species, more rapidly with declining root temperature than could be accounted for by the change with temperature in the viscosity of water, thus indicating an effect of temperature on root permeability. The same effect was evident in jack pine seedlings, but not white spruce transplants, that had been grown for 28 days in the greenhouse after removal from cold storage.     

Securidacaxanthone A, a heptaoxygenated xanthone from Securidaca longepedunculata

From the root bark of Securidaca longepedunculata, a heptaoxygenated xanthone (1) has been isolated as well as two known xanthones (2) and (3) and two salicylic acid derivatives (4) and (5). The structure of 1 has been elucidated from 1H and 13C-NMR spectral data.     

Changes in volatile terpene and diterpene resin acid composition of resistant and susceptible white spruce leaders exposed to simulated white pine weevil damage

Induced (traumatic) resin in white spruce (Picea glauca (Moench) Voss) leaders resistant or susceptible to the white pine weevil (Pissodes strobi Peck) was analyzed for volatile terpenes and diterpene resin acids after simulated white pine weevil damage. Leaders from 331 trees were wounded just below the apical bud with a 1-mm diameter drill, coinciding with the natural time of weevil oviposition in the spring. Leaders were removed in the fall, and the bark and xylem from the upper and lower regions of the leader extracted and analyzed by gas chromatography. Unwounded trees had low amounts of resin in xylem compared with bark. In response to wounding, volatile terpenes and diterpene resin acids increased in the upper xylem (area of wounding), with resistant trees showing a greater increase than susceptible trees. Wounding caused monoterpenes in particular to decrease in the lower region of the leader (away from the drilled area) in greater amounts in susceptible trees than in resistant trees. In response to wounding, the proportion of monoterpene to resin acid increased in the upper and lower xylem of resistant trees, and slightly increased in the upper xylem of susceptible trees. Monoterpene-enriched resin is more fluid than constitutive resin, and probably flows more readily into oviposition cavities and larval mines, where it may kill immature weevils. Loss of resin components in the lower xylem suggested catabolism and transport of these materials to the site of wounding; however, energetic and regulatory data are necessary to confirm this hypothesis. This study provides a basis for measuring the ability of a tree to undergo traumatic resinosis that could be used to screen for resistance to white pine weevil.     

Mitigation of effects of extreme drought during stage III of peach fruit development by summer pruning and fruit thinning

A water deficit during stage III of fruit growth was established with the aim of determining if it is possible to achieve an improvement in tree water status by summer pruning and fruit thinning. The experiment was set up as a randomized block split-plot design across trials (irrigation) where pruning was assigned to the main plot and fruit thinning to the sub-plots. The irrigation treatments were (1) standard full irrigation (FI), and (2) suppression of irrigation during stage III of fruit growth until leaves visibly withered (LWI); the pruning treatments were (1) experimental summer pruning (EP), and (2) standard summer pruning (CP); and three fruit thinning intensities were applied to facilitate analysis of the effects of the treatments in relation to fruit load. Changes in amount of light intercepted and in tree stem water potential (Psi stem) were evaluated. The EP treatment reduced the amount of light intercepted by the tree. In the FI treatment, there was a significant reduction in fruit growth measured as both water accumulation and dry mass accumulation. Under FI conditions, reductions in fruit load as a result of EP were not accompanied by a significant improvement in Psi stem. In the LWI treatment, EP produced a significant improvement of 0.17 MPa in Psi stem, but there was no improvement in fruit growth compared with CP trees. A reduction in fruit load from 350 (commercial load) to 150 per tree significantly improved Psi stem by 0.3 MPa at the end of stage III of fruit growth. These results indicate that improvements in water status in response to pruning may be insufficient to promote fruit growth if the pruned trees are unable to provide an adequate supply of assimilates to the developing fruits.     

Physical and chemical responses of Sitka spruce (Picea sitchensis) clones to colonization by Heterobasidion annosum as potential markers for relative host susceptibility

Forty-one 2-year-old clones of Picea sitchensis (Bong.) Carr. from three full-sib families (14 clones from each of two families and 13 clones from a third family) were either wounded and inoculated with an isolate of Heterobasidion annosum (Fr.) Bref. or wounded without inoculation. Lesion lengths on the inner bark from the point of inoculation varied among clones 35 days after treatment. There was no relationship between lesion length and relatedness within families. Two clones (21342 and 25202) with the shortest lesions, tentatively designated as less susceptible to H. annosum, and two clones (21176 and 27166) with the longest lesions, designated more susceptible, were selected for comparison of host anatomical and chemical responses to infection. The position and structure of the ligno-suberized boundary zone (LSZ) in the bark of the clones suggested that the less susceptible clones formed thicker layers of suberized cells in the LSZ following wounding plus inoculation. No LSZ was observed in two ramets of the more susceptible Clone 27166 following wounding and inoculation with H. annosum. Compared with more susceptible genotypes, clones of P. sitchensis with low susceptibility to H. annosum had high relative proportions of (+)-alpha-pinene, (-)-beta-pinene and one unidentified terpene constituent (Unknown-15) in cortical resin sampled 25 cm from the lesions. In contrast, more susceptible clones had higher relative proportions of (-)-limonene, Unknown-16, Unknown-18 and Unknown-19. In the secondary resin produced in bark tissues surrounding the lesions, proportions of several monoterpene constituents varied; these changes included a decrease in the relative amount of beta-phellandrene and corresponding small increases in some minor constituents. The concentrations of the monoterpenes, except a few minor constituents, increased in the infected tissues. Wounding plus inoculation with H. annosum resulted in varied monoterpene responses, with distinct differences between less susceptible and more susceptible clones. In less susceptible clones, Unknown-19 increased following wounding plus inoculation, whereas in more susceptible clones, concentrations of delta-3-carene and Unknown-13 and Unknown-16 increased. Differences in both constitutive and induced resin monoterpene profiles may provide useful markers for resistance to H. annosum in selection and breeding programs.     

Response of Ocotea bullata,Curtisia dentata and Rapanea melanophloeos to medicinal bark stripping in the southern Cape,South Africa: implications for sustainable use

Tree bark is commonly used for traditional medicine in southern Africa and further afield. Increasing demand and commercialisation have resulted in the overexploitation of many species, posing a major challenge to forest managers to develop mechanisms for sustainable resource use. An experimental bark harvesting research project was initiated in the southern Cape, South Africa, to inform best practices for bark harvesting based on tree response to bark stripping. The species selected for the study, Ocotea bullata, Curtisia dentata and Rapanea melanophloeos, are much sought after and well represented in southern Cape forests. The treatment entailed removing vertical strips of bark, 1 m in length and of different strip widths, covering the full range of tree size classes ≥10 cm DBH. The treatments were applied during two seasons, winter and summer. Evaluations were done every six months to assess tree response to bark stripping in terms of bark regrowth through phellogen edge and sheet development, and susceptibility to insect and fungal damage. The results show a differential response of tree species in terms of phellogen edge and sheet growth, as well as susceptibility to fungal and insect attack. Rapanea melanophloeos was the most vulnerable to fungal and insect damage and displayed little bark regrowth following wounding. Curtisia dentata showed best bark regrowth through sheet development. Only O. bullata, though, showed adequate bark regrowth (through edge development) to allow for sustainable strip harvesting. Bark regrowth is influenced by season of stripping, although this is difficult to define considering the wide range of environmental and other factors affecting tree response to bark removal. Smaller trees are more vulnerable to bark stripping, especially with a wide strip, with poorer bark regrowth than bigger trees.