Death of bark in Acer pseudoplatanus associated with drought

Radially flattened fibres and parenchyma cells, together with buckled and constricted rays were interpreted as a drought ring in Sycamore (Acer pseudoplatanus L.). The damage was dated to late summer of 1972, an exceptional drought year in Scotland. Nectria coccinca (Pers. ex Fr.) Fr. and Verticillium tenerum (Nees ex Pers.) Link (Nectria inventa Pethybridge) were the two organisms found almost exclusively in bark and wood of lesions on stems and branches. These lesions were non perennating and had been formed at the end of the 1972 growing season.     

Wind Damage to the Leaves of Sycamore (Acer pseudoplatanus L.) in Coastal and Non-coastal Stands

Wind damage to the leaves of sycamore (Acer pseudoplatanus L.)trees was examined at five sites in Northern Ireland duringJune and September, 1986 by estimating the percentage of leafarea showing lesions, discoloration or actual loss of laminasurface. Levels of damage on individual leaves ranged up to 46.6 percent of the leaf area but few leaves had damage greater than10 percent. Two sites showed relatively low levels of damage(about 2 per cent of lamina damaged); one site was inland, andthe other, although coastal, was well sheltered. The three othersites had damage in excess of 3.5 per cent of the lamina area—thesite with the highest levels of damage being the most exposedsite and the one probably experiencing the greatest amount ofturbulence. Most damage had occurred by June and there was littleincrease in damage levels between the June and September samples;there was however evidence of the premature loss of the mosthighly damaged leaves. Regression analysis indicated that at sites showing the highestlevels of damage, the most highly damaged leaves were the smallest.It is argued that in these cases the damage to the leaves issufficiently high to prevent full leaf expansion. At sites wherethe overall damage levels were lower, there was either a non-significantrelationship between percentage leaf damage and leaf area ora significant positive relationship. It is suggested here thatthe damage levels are not great enough to inhibit the expandingleaves reaching full size.     

Ecophysiology and Survival of Acer pseudoplatanus L., Castanea sativa Miller. and Quercus frainetto Ten. Seedlings on a Reforestation Site in Northern Greece

Seedlings of three tree species (Acer pseudoplatanus L., Castanea sativa Miller. and Quercus frainetto Ten.) were planted on a field site in Northern Greece to investigate factors connected to planting failures. On several dates, for the first two growing seasons after planting (1997 and 1998), leaf water potential, chlorophyll fluorescence, gas exchange variables and seedling survival were determined. Q. frainetto seedlings exhibited the lowest values of leaf water potential (Ψ) for most of the season in both studied years. Seedlings of all species showed large reductions in Ψ the mid-summer in both years, with particularly low values in 1998. In both years, a sharp reduction in Ψ was observed at the beginning of July when all three species exhibited their lowest net CO₂ assimilation (A) rate by the end of July. In 1997, A recovered after the July depression to values even higher than those recorded in June. However, in 1998, only Q. frainetto and to a lesser degree C. sativa recovered from a similar July depression in physiological values. Species reached their highest A rates by the end of August in 1997 and in June during 1998. In general, stomatal conductance and transpiration rates paralleled the A patterns. In 1997, the seasonal course of effective quantum yield (ΔF/F_m), for all plant species followed a rise-and-fall pattern with a peak at the beginning of July. In 1998, ΔF/F_m values were relatively high in June, showed a deep depression during July and while Q. frainetto and C. sativa recovered afterwards, A. pseudoplatanus continued to exhibit very low values. This study showed that differences in mortality between species were due to differences in tolerance to water stress and the superiority of Q. frainetto was probably related to the fact that it was the only species native and adapted to the planting site     

Widespread latent infection of Cryptostroma corticale in asymptomatic Acer pseudoplatanus as a risk for urban plantations

Sooty bark disease (SBD) caused by the pathogen Cryptostroma corticale is currently one of the risks to the population of Acer pseudoplatanus in Europe. After a number of records of symptomatic and dead trees in Prague, assessment of the latent non‐symptomatic stage of SBD was questioned as a means to forecast the health risk of the A. pseudoplatanus population. We used two methods of early detection of C. corticale in non‐symptomatic trees: cultivation from wood tissue on agar plates and a culture‐free approach based on nested PCR with newly designed species‐specific primers. The pathogen was detected in 25% of 112 examined trees from seven localities in Prague, but the disease incidence might be higher if more A. pseudoplatanus trees in Prague were included and if the crown infections were considered. The presence of C. corticale was positively correlated with discoloured wood, but its presence did not depend on the occurrence of external symptoms. Infected trees were more frequently found in groups on steep sites at higher elevations. In addition, heavier NO_x pollution combined with more paths and roads increased the incidence of C. corticale.     

Temperature Relations of Germination in Acer platanoides L. Seeds

The aim of this study was to describe the effect of temperature on the germination response of Acer platanoides L. seeds and the possible influence of dormancy. Moist chilled seeds (fruits) from eight trees were germinated at eight constant temperatures from 3 to 32C for 30 days. The highest germination was obtained at temperatures below 10C and the highest rate of germination was between 22 and 28C. The critical lower temperature for germination was estimated to be -2.6C, and the critical upper temperature between 30 and 35C. Temperatures above 10-15C increasingly inhibited the germination of seeds. Some of the non-germinated seeds were able to germinate after a second chilling period, possibly as a consequence of further release of primary dormancy and an indicated secondary dormancy. Seed survival decreased with increasing temperatures above 15C. The rate of germination was correlated with the accumulated thermal time at suboptimal temperatures. In conclusion, a constant temperature of 10C is recommended for testing the germination of seeds of A . platanoides.     

Soil physical factors affecting the growth of sycamore (Acer pseudoplatanus L.) in a silvopastoral system on a stony upland soil in North-East Scotland

Tree growth and soil physical properties were compared on two grazed plots planted with sycamore at 5 and 10 m square spacing on an upland Scottish site. Both plots received fertilizer and stocking density of ewes and lambs was adjusted to maintain a constant sward height.Mean tree height in 1990 and height increment (1988–90) were significantly greater in the 5 m spaced plot (P<0.05). Although matric potential under the trees was generally greater than in the grassed rows between trees, mean penetration resistance (37–107 mm depth) was significantly greater (P<0.01) under the trees. Even when the soil was close to field capacity, less than 10% of penetrometer readings were < 1 MPa under the trees, in comparison to 44% in grassed areas between trees. This demonstrates that surface compaction due to preferential treading by sheep near the base of trees was sufficient to have seriously reduced tree root growth. Penetration resistance under the 5 m spaced trees was significantly less (P<0.05) than under the 10 m spaced trees. A technique for estimating the probability of root deflections by stones (in 35 mm depth intervals), Ps, from penetrometer readings was used. A significant relationship (P<0.1) was found between tree height increment and depth to Ps0.4 in the 10 m plot.     

Early results of sycamore (Acer pseudoplatanus) provenance trials at farm-forestry sites in England and Wales

The early growth of British and continental provenances of sycamore,Acer pseudoplatanus L., was compared in the nursery and in fieldtrials at five farm-forestry sites. There were significant differencesbetween provenances in height and root-collar diameter in thenursery. After four seasons in the field the ranking of provenancesfor height had changed considerably and differences betweenprovenances were no longer significant summing over sites. Ofthe four continental provenances, two, from Denmark and Germany,performed better than the British provenances at those siteswhere they were included. Results are discussed in relationto the selection of improved sycamore planting material forthe forest industry.     

Variations in the Growth of Different Seeds of Acer pseudoplatanus and Betula verrucosa Grown on Different Soils

Seed of Acer pseudoplatanus was obtained from six widely scatteredlocations in Europe, and seedlings from these seed-sources weregrown on 25 different soils, covering a wide range of soil properties.Seedlings from four seed-sources of Betula verrucosa were alsogrown. There was a very wide variation in growth on the differentsoils, and between the two species; but relatively little variationbetween seed-lots within a species, and no significant interactionbetween seed-lot and soil, over the 2-year period of the experiment.It is concluded, therefore, that any one of the seed-lots usedin this experiment could have been used to assess the responseof seedlings of that species to changes in soil type, and thatvariation in growth due to genetic differences within thesespecies is likely to be small in comparison to the variationdue to soil conditions.     

Responses of endomycorrhizal and non-mycorrhizal plants of Acer pseudoplatanus to different levels of soluble and non-soluble phosphorus

A greenhouse experiment compared growth and mineral nutrition of mycorrhizal and non-mycorrhizal seedlings of Acer pseudoplatanus on a fumigated soil. The effects of mycorrhizal inoculation were examined at six rales of soluble phosphate and five rates of non-soluble phosphate. Inoculation with Glomus mosseae markedly stimulated phosphorus uptake and growth only at the lowest level of soluble phosphorus. With 200 ppm of added monocalcium phosphate mycorrhizal infection depressed growth and considerably modified the relationships between yield and phosphorus concentration in plant tissues. The possible causes of growth depression at high level of added soluble phosphorus are discussed.     

Wilt of Acer negundo L. caused by Fusarium nirenbergiae in China

Boxelder maple(Acer negundo L.) is widely grown as ornamental trees in China. In 2017 in Pizhou,Jiangsu Province, China, the boxelder maple trees suffered from a disease which caused wilting and yellowing leaves,rotted roots, and discolored xylem. The disease broke out from July to August. Seven fungal isolates were obtained from symptomatic tissue and tested for pathogenicity.Isolate An7 was isolated at high frequency from the discolored vascular tissues, which caused the wilt disease on healthy 2-year-old seedlings after inoculation and eventually killed all the seedlings. We conducted molecular analysis for An7, including the partial sequences of the rDNA internal transcribed spacer, calmodulin, RNA polymerase II second largest subunit and the translation elongation factor 1-a and evaluation of the variously sized conidia, chlamydospores and conidiophores and cultural traits. The pathogen was identified as Fusarium nirenbergiae, a member of the Fusarium oxysporum speciescomplex. To our knowledge, this is the first report of F.nirenbergiae causing wilt on A. negundo in China.     

Effect of thinning on growth of Acer velutinum Boiss. in northern forests of Iran

It has become necessary to develop stands of fast growing endemic species in the Caspian forests because of their reduction in area and the domestic demand of timber processing industries in Iran. Acer velutinum, an en- demic species in Iran, is often planted in monocultures or in a mixture with other endemic species. Our study was con- ducted on A. velutinum planted in Berenjestanak （control plots） and Chaibagh （thinned plots） in northern Iran in 1991. A randomized sampling method with circular sampling plots of 100 m2 was used to measure diameter and height of trees. The results show that the diameter of trees in thinned stands was 19.98 cm and in the control stands 13.84 cm, while the mean heights were 18.33 and 17.46 m, respectively. The mean basal area in thinned stands was 30.74 m2 and in the control 15.70 m2 per ha. The results of Student＇s t tests indicate that there are significant differences at a probability level of 99.9% between the two variously treated stands in diameter （d）, height （h）, basal area, volume growth and the stabil- ity coefficient. We conclude that tending operations with suitable intensity in different time periods are recommended to obtain stable stands.     

Effects of climate and management history on the distribution and growth of sycamore (Acer pseudoplatanus L.) in a southern British woodland in comparison to native competitors

Sycamore (Acer pseudoplatanus L.) is an invasive, non-nativespecies in Great Britain and its management in conservationareas is controversial. Climate change adds further uncertaintyto decision making. We investigated the role of management historyin determining present-day abundance and the effects of climaticvariability on growth, photosynthesis and phenology at WythamWoods, a UK Environmental Change Network (ECN) monitoring site.Relatively few sycamore trees were found in undisturbed ancient,semi-natural woodland and recent plantations, despite beingcommon in other areas of the site. Sycamore grew more slowlythan ash (Fraxinus excelsior L.), its principal competitor,but at a similar rate to pedunculate oak (Quercus robur L.)in the period 1993–2005. There were fewer sycamore thanash seedlings, regardless of which species dominated the canopy.Growth of sycamore was slower in dry periods than wet ones andlower photosynthetic rates were measured in canopy leaves underdry compared with wet soil conditions. This study thereforesuggests that sycamore does not present a serious threat toundisturbed ancient woodland on the site and that it may eventuallydecline in areas of the site where it competes with ash, inthe absence of disturbance. It may also decline under climatechange if summer droughts become more frequent.     

Growth and provenance of Norway maple (Acer platanoides) in lowland Britain

The results of an experiment to investigate the early growthand form of ten different provenances of Norway maple (Acerplatanoides L.) are described. Two sites were planted and after8 years survival was 88 per cent and 95 per cent and heightincrement was 402 cm and 201 cm; confirmmg the potential ofNorway maple to be a productive forest tree. Provenances thatperformed well were from Germany, the Netherlands, Denmark andYugoslavia; exact locations were not known for all seed collections.A provenance from Russia was included, material from this fareast has rarely been tested in Britain. However, as expected,its performance was relatively poor. The main constraint tofurther planting of Norway maple is the palatability of thebark to grey squirrels (Sciurus carolinensis Gmelin.). However,it is a useful tree for high pH and heavy soils and as an alternativespecies to sycamore (Acer pseudoplatanus L.).     

The effects of propagation environment on the rooting of leafy cuttings of ash (Fraxinus excelsior L.), sycamore (Acer pseudoplatanus L.), and sweet chestnut (Castanea sativa Mill.)

The effect of propagation environment on the rooting of field collected leafy cuttings of ash (Fraxinus excelsior, sycamore (Acer pseudoplatanus) and sweet chestnut (Castanea sativa) was investigated in two experiments. In the first experiment, rooting of all three species in mist enclosed inside a polythene tent was greater than 50%, while rooting of ash cuttings was reduced from 63% in enclosed mist to only 16% in open mist. Rooting in open mist, enclosed mist, and contact polythene was studied in a second experiment. Sycamore cuttings rooted equally well in the two mist systems with an average rooting of 78%. In contrast cuttings of both ash and sweet chestnut rooted most under the enclosed mist system, at 64 and 46% respectively. Rooting of ash cuttings was again depressed in the open mist system where less than 30% of cuttings rooted. This reduction was related to an increase in the percentage of cuttings which remained alive without rooting, while showing proliferation of callus at the cutting base. The percentage of sweet chestnut cuttings which callused without rooting was also much greater in the open mist system than in enclosed mist or contact polythene.     

Influence of soil properties on the growth of sycamore (<Emphasis Type="Italic">Acer pseudoplatanus </Emphasis>L.) in Denmark

Despite high demand on the timber, sycamore (Acer pseudoplatanus L.) covers only about 2% of the forested area in Denmark, mainly because several examples of failed stands have made foresters reluctant to grow sycamore. In order to optimize the use of sycamore, scientifically based knowledge is needed on the specific demands of sycamore to soil properties. Therefore, 34 stands of sycamore covering a broad range of soil types, tree heights and ages were investigated. Tree height and age were determined on 20 trees in each stand and combined into a site index. In each stand, soil water status, slope and ground cover were determined and soil samples were taken and analyzed for pH, organic carbon, total nitrogen, calcium carbonate, bulk density and texture in the laboratory. The data were analyzed by simple regression supplemented by PCA and MLR. Accordingly, sycamore can grow well on a broad range of soils regarding texture and water content. However, soils with stagnant water within 40 cm of the soil surface are unsuited for sycamore. On well-drained soils, increasing clay content caused better sycamore growth, which was also improved on insufficiently drained soils with calcium carbonate. Increased nitrogen content stimulated sycamore growth while, less productive stands occurred on carbon rich soils indicating that carbon and nitrogen contents can serve as sycamore growth indicators. Bulk density, C/N ratio and pH showed no significant influence on growth. The investigation showed that sycamore could grow well on a broader range of soils than hitherto believed.     

湖南槭属植物分类修订——I.分类系统

湖南是我国槭属Acer L.植物分布的重要区域.在前人研究的基础上,通过对中南林业科技大学树木标本室(CSUFT)、湖南师范大学生命科学院植物标本馆(HNNU)和中国科学院华南植物园植物标本馆(IBSC)所收藏的湖南槭属标本的全面鉴定、整理以及进行野外补充调查,基本查清了本省槭属植物种类,承认湖南槭属植物有41种、3个亚种、17个变种,按照方文培(1981)槭属分类系统,归属于2个亚属、10个组、15个系;将城步长柄槭和绿叶中华槭2变种暂存疑.     

TEM/FE-SEM studies on tension wood fibres of Acer spp., Fagus sylvatica L. and Quercus robur L.

Tension wood (TW) fibres from maple, beech and oak were analysed with special emphasis on the cell wall fine structure and deposition of aromatic compounds within the gelatinous layer (GL). For this purpose, transmission electron microscopy (TEM) was applied after section staining with potassium permanganate. There was evidence for the occurrence of aromatic compounds in the GLs of fibres of all three species. Some GLs showed a concentric sub-layering. Hence, conclusions about the biosynthetic activities during cell wall formation in TW could be derived. Additional information about structural characteristics of TW fibres were obtained by means of field emission electron microscopy. High-resolution micrographs of cell walls were used for measurements of diameter and microfibril angle (MFA) of cellulose aggregates (CAG). CAG of 7 nm were observed although their diameter varied greatly in the GLs. MFA in the secondary wall of TW was slightly smaller than in opposite wood. The microscopic methods provided complementary ultrastructural and topochemical information on tension wood fibres. The subcellular localisation of aromatic compounds and the observations of the ultrastructural morphology will contribute to the understanding of origin and functionality of TW and its characteristic GL.