Rodent impact on establishment of direct-seeded Fagus sylvatica,Quercus robur and Quercus petraea on forest land

Abstract

Seed predation by granivorous rodents constitutes a major problem during reforestation using direct seeding. Acorns or beech nuts were sown at 14 different sites in Denmark and southern Sweden, and seedling establishment was inventoried during the first three growing seasons. Around the time of sowing, rodents were either snap-trapped or live-trapped. At some sites, perches for raptors were installed, and at other sites, signs of predation were investigated or predation was monitored by camera surveillance. Granivorous rodents had a profound negative influence on sowings, and the removal of beech nuts occurred rapidly following sowing. Establishment of oak was better when surroundings consisted of mixed forests rather than broadleaved forests. Fewer rodents were caught, and establishment was better, in large reforestation areas. Rodent captures indicated that forest edges, slash piles and stone wall remains were suitable rodent microhabitats. Snap-trapping or raptor perches did not result in increased oak establishment. Neither sowing in summer nor increased seeding depth decreased predation by rodents on beech nuts. In conclusion, seeds need protection from rodents immediately at the time of sowing. Choosing large regeneration areas combined with removal of suitable rodent habitats seems to be a practical alternative for the development of successful strategies for direct seeding.     

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.     

Productivity of mixed versus pure stands of oak (Quercus petraea (Matt.) Liebl. and Quercus robur L.) and European beech (Fagus sylvatica L.) along an ecological gradient

The mixture of beech (Fagus sylvatica L.) and oak (sessile oak, Quercus petraea (Matt.) Liebl., and pedunculate oak, Q. robur L.) is of considerable importance in Europe and will probably become even more important under climate change. Therefore, the performance of oak and beech in mixture was compared with the species’ growth in pure stands. Data from 37 long-term mixing experiments in Poland, Germany and Switzerland were pooled for analysis of mixing effects on stand productivity and possible interrelationships with mixing portions or site conditions. We found that on average, mixed stands of oak and beech exceeded biomass productivity in pure stands by 30 % or 1.7 t ha^?1 year^?1, as the growth of both species was benefitted by the mixture. However, that the interaction actually ranged from facilitation and overyielding on poor sites to underyielding on fertile sites triggered by competition. An empirically derived interaction model showed volume and dry mass growth changing in mixed stands from gains of 50 % to losses of 10 % depending on site conditions. It is concluded that the analysed mixture grows in accordance with the stress-gradient hypothesis and that our results suggest a site-specific relationship between species mixture and biomass productivity. As a consequence, an adequate species mix should result in increased productivity under steady state as well as climate change.     

High-pruning of European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.): work efficiency for target pruning as a function of tree species,pruning height,branch characteristics,pole saw type and operator

The objective of this study was to establish an operational model of productive work time per tree (work efficiency) for high-pruning of young European beech and pedunculate oak depending on tree species, pruning height, branch characteristics, pole saw type and operator. The final model included all of these independent variables with branch characteristics specified in terms of number of live branches and cross-sectional area of the thickest branch at the cut. Work time increased with increasing values of each of the three numeric variables. For a given pruning height the size of the largest branch was for all practical purposes more influential than the number of live branches. Beech took 28% longer to prune than oak. The German Ergo-Schnitt saw was 21% slower than the Japanese Silky Hayauchi saw. The variation in worker performance within our study was larger than that attributed to tree species and pruning equipment.     

Comparing the intra-annual wood formation of three European species (Fagus sylvatica, Quercus petraea and Pinus sylvestris) as related to leaf phenology and non-structural carbohydrate dynamics

Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species. The main objective of this study was to determine how the timing, duration and rate of radial growth change between species as related to leaf phenology and the dynamics of non-structural carbohydrates (NSC) under the same climatic conditions. We studied two deciduous species, Fagus sylvatica L. and Quercus petraea (Matt.) Liebl., and an evergreen conifer, Pinus sylvestris L. During the 2009 growing season, we weekly monitored (i) the stem radial increment using dendrometers, (ii) the xylem growth using microcoring and (iii) the leaf phenology from direct observations of the tree crowns. The NSC content was also measured in the eight last rings of the stem cores in April, June and August 2009. The leaf phenology, NSC storage and intra-annual growth were clearly different between species, highlighting their contrasting carbon allocation. Beech growth began just after budburst, with a maximal growth rate when the leaves were mature and variations in the NSC content were low. Thus, beech radial growth seemed highly dependent on leaf photosynthesis. For oak, earlywood quickly developed before budburst, which probably led to the starch decrease quantified in the stem from April to June. For pine, growth began before the needles unfolding and the lack of NSC decrease during the growing season suggested that the substrates for radial growth were new assimilates of the needles from the previous year. Only for oak, the pattern determined from the intra-annual growth measured using microcoring differed from the pattern determined from dendrometer data. For all species, the ring width was significantly influenced by growth duration and not by growth rate, which differs from previous studies. The observed between-species difference at the intra-annual scale is key information for anticipating suitability of future species in temperate forests.     

欧洲山毛榉干燥工艺初探

通过试验研究探索出在国产蒸汽加热干燥窑上干燥欧洲山毛榉的干燥工艺,该工艺具有处理后干燥周期短、开裂和变形小的特点,达到了国家干燥锯材一级标准.     

Thermally initiated solvent-free radical modification of beech (Fagus sylvatica) wood

A procedure for rapidly modifying beech wood using a thermally initiated solvent-free grafting system was examined. In the modification, butyl acrylate and butyl methacrylate were used as vinyl monomers. Free radicals were generated from 2,2′-azobis(2-methylpropionitrile) or benzoyl peroxide at 103 and 180 °C by contact heating of the modified material. Chemical changes in the material were investigated by FTIR and X-ray photoelectron spectroscopies. The modification resulted in decreased surface wetting of the material manifested by increased water contact angles. The hardness of the resultant material decreased, while its color changed by the effect of temperature. It was shown that the approach allowed for efficient thermal-initiated modification of wood with rapid contact heating.     

Leaf gas exchange and growth of flood-tolerant and flood-sensitive tree species under low soil redox conditions

Seedlings of Taxodium distichum L., Quercus lyrata Walt. and Q. falcata var. pagodaefolia Ell. were grown for 22 days in a rhizotron system providing two soil redox potential regimes, +170 mV (low Eh) and +560 mV (high Eh). Leaf chlorophyll concentration and gas exchange, root alcohol dehydrogenase (ADH) activity, root and leaf ethylene production, and growth and biomass partitioning were measured. In response to the low Eh soil treatment, stomatal conductance was reduced in Q. falcata and Q. lyrata but not in T. distichum, whereas net photosynthesis was reduced significantly in all species; however, net photosynthesis in T. distichum began to recover within 2 weeks of treatment initiation. Within each treatment, mean stomatal conductance and net photosynthesis were significantly greater in T. distichum than in the oak species. Leaf chlorophyll concentration was not affected by the soil treatments. All species showed significant reductions in root and leaf dry weights in response to the low Eh soil condition. The low Eh soil treatment resulted in increased root ADH activity and ethylene production in T. distichum, but had no effect on root ADH activity and ethylene production in the oak species.     

Interaction of lignin and polysaccharides in beech wood (Fagus sylvatica) during drying processes

Summary ¹³C CP MAS NMR spectroscopy was used to characterize the structural changes of cell wall polymers in beech wood Fagus sylvatica during drying processes. The analysis of five wood samples, namely, untreated, untreated dried, pre-treated by steam and/or NaOH subjected to drying showed partial depolymerization of lignin component as well as the change of the ratio of the crystalline and of the amorphous parts of cellulose as the consequence of wood pre-treatment. In addition, T_1ρ(¹H) relaxation times were determined in beech wood sample pre-treated with steam at 135 °C and the lignin isolated from this sample. The magnitudes of the relaxation times were found comparable in both samples as well as in the lignin-cellulose model compound. These unique T_1ρ (¹H) values indicate that spin diffusion is complete and homogeneous due to spatial proximity of spins and confirmed the formation of lignin-cellulose complex during thermal treatment of wood. Received 30 June 1997     

Fungi associated with above-ground portions of declining oaks (Quercus robur) in Germany

Various disease symptoms on oak (Quercus robur L.) affected by oak decline in northern Germany were examined for fungal colonization. The isolated fungi are evaluated in respect to their possible pathogenic qualities and the results are compared with those of other authors and geographic regions.     

Morphological and physiological responses of beech (Fagus sylvatica) seedlings to grass-induced below ground competition

We examined morphological and physiological responses of beech (Fagus sylvatica L.) seedlings to grass-induced below ground competition in full-light conditions. Two-year-old beech seedlings were grown during two growing seasons in 160-l containers in bare soil or with a mixture of five grass species widely represented in semi-natural meadows of central France. At the end of the second growing season, beech seedlings in the presence of grass showed significant reductions in diameter and height growth, annual shoot elongation, and stem, root and leaf biomass, but an increase in root to shoot biomass ratio. Grasses greatly reduced soil water availability, which was positively correlated with daily seedling diameter increment. Beech seedlings seemed to respond to water deficit by anticipating stomatal closure. There was evidence of competition for nitrogen (N) by grasses, but its effect on seedling development could not be separated from that of competition for water. By labeling the plants with 15N, we showed that beech seedlings absorbed little N when grasses were present, whereas grasses took up more than 97% of the total N absorbed in the container. We conclude that, even if beech seedlings display morphological and physiological adaptation to below ground competition, their development in full-light conditions may be strongly restricted by competition from grass species.     

Intra- and interspecific diversity in the response to waterlogging of two co-occurring white oak species (Quercus robur and Q. petraea)

Quercus robur L. and Quercus petraea (Matt.) Liebl. are sympatric oak species with different ecological requirements. Quercus robur is more tolerant to waterlogging than Q. petraea. This ecological divergence may play a role in the maintenance of the two species despite the absence of an insurmountable reproductive barrier between them. We predicted that the genetic architecture of traits related to waterlogging tolerance differs between the species. To gain insight into this architecture in the absence of genetic markers for waterlogging tolerance, we compared populations of seedlings of each species for diversity in the expression of quantitative phenotypic traits induced by severe hypoxia. To determine the capacity for hypertrophied lenticel formation, we applied gas-impermeable mastic to stems of seedlings. Two months after application, the mastic treatment had induced the formation of 3 (+/- 2) cm(-2) hypertrophied lenticels in the absence of root hypoxia. Leaf epinasty during root hypoxia was an early predictor of seedling mortality. Four weeks of waterlogging resulted in greater epinasty in Q. petraea than in Q. robur, but fewer hypertrophied lenticels (16 +/- 6 versus 21 +/- 9 cm(-2)) and adventitious roots (2.7 +/- 4.7 versus 5.2 +/- 5.9). Differences between species in these traits were associated with differences in the frequencies of extreme phenotypes rather than with a generally higher tolerance to waterlogging in Q. robur seedlings.     

Variations in sucrose and ABA concentrations are concomitant with heteroblastic leaf shape changes in a rhythmically growing species (Quercus robur)

In rhythmically growing woody species such as common oak (Quercus robur L.), stem growth is discontinuous and a bud forms at regular intervals at the shoot apex. These buds are composed of different types of leaves: laminate, aborted lamina and scale. The change in heteroblastic leaf shape from laminate to aborted lamina leaves is regarded as one of the events marking shoot growth arrest. To better understand the determinism of heteroblastic leaf shape change and thus, of rhythmicity, we studied morphogenetic events during the early days of the second flush of growth in oak, as well as changes in sucrose metabolism and abscisic acid (ABA) concentrations in control plants expressing the heteroblastic leaf shape change and in defoliated plants showing no heteroblastic leaf shape change and producing only laminate leaves. In control plants, the leaf shape change was underway on Day 5 of the second flush with the differentiation of the first two aborted lamina leaves. Sucrose concentration in the apices of control plants decreased between Days 3 and 5 during differentiation of the aborted lamina leaves. An inverse pattern was observed in defoliated plants, suggesting that sucrose acts as a signal triggering heteroblastic leaf shape changes. During the same period, acid cell wall invertase activity was high in young stem and laminate leaves of control plants, whereas the activity remained constant and low in the apices. If the laminate leaves were removed, the increase in apical sucrose concentration was proportionally higher than the decrease in apical acid vacuolar invertase activity, suggesting that, in the absence of young leaves, sucrose is imported to the apex. The sucrose concentration in the apex is therefore likely to be affected by trophic competition with the expanding laminate leaves. The decrease in apex sucrose concentration may be one of the mechanisms driving heteroblastic leaf shape change. Differentiation of aborted lamina leaves was followed by a decrease in the organogenic activity of the shoot apical meristem (SAM) between Days 7 and 9. High concentrations of ABA are associated with differentiation of aborted lamina and scale leaves and with low SAM organogenic activity. Shoot apical meristem organogenic activity remained high and ABA concentration in the apex remained low in defoliated plants producing only photosynthetic leaves. These results suggest that (1) ABA is involved in the gradual conversion of embryonic leaves to abnormal leaves, thereby regulating heteroblastic leaf shape changes and (2) changes in ABA concentration influence the intensity of SAM organogenic activity. Heteroblastic development and therefore rhythmic growth could be the result of competition between apices and laminate leaves, with competition first involving sucrose and thereafter ABA.     

Effect of endophytic fungi from oak (Quercus robur L.) on mortality of leaf inhabiting gall insects

Observations in the field suggest that certain species of endophytic fungi which occur, but are normally dormant, in the leaves of Quercus robur can be stimulated to pathogenic development by the feeding activity of certain gall insects. As a result of the death of leaf tissue the gall is also killed. This antagonistic relationship between endophytic fungi and gall insects is illustrated in the following three examples: Kabatiella apocrypta / Trioza remota, Gloeosporium quercinum / Neuroterus numismalis and Dichomera saubinetii / Polystepha panteli.     

Variation in log quality and prediction of sawing yield in oak wood (Quercus robur)

Context

The commercial feasibility of sawmilling depends on the expected volume and value of sawn planks. Models that predict the volume of sawn timber of a particular quality and produced from logs of known characteristics are therefore very useful.

Aims

The objectives were to study variation in sawing yield and to obtain models that predict lumber volume and grade recovery on the basis of easy-to-measure predictor variables of saw logs.

Methods

Forty-six oak trees growing in Galicia (NW Spain) were felled and cut into logs. The logs were visually graded and sawn mainly into quartersawn planks, which were dried, planed and visually graded for structural purposes.

Results

The total volumetric sawing yield was 47.6 %. The sawing yield for planks of structural dimensions (cross-section, 70?×?120 or 70?×?170 mm) was 43.4 %, but decreased to 8.4 % for structural sized and quality grade beams because of wane and biotic damage in many pieces. Log grade did not significantly affect sawing yield in the sample analysed, despite the wide range of diameter over bark at the smallest end in the sampled logs (22–77 cm). The sawing pattern affected total sawing yield (F?=?4.913; p value?=?0.001) and the sawing yield for structural planks (F?=?6.142; p value?=?0.0002); radial sawing with one cut and live sawing of half logs provided the highest yields. Three models were proposed for estimating sawn volume in timber products, with the small-end log diameter over bark as the predictor variable and R _adj ² between 0.31 and 0.78 (p value?<?0.01).

Conclusion

For the purpose of producing oak timber destined for structural use, the presence of bark and sapwood in planks must be reduced in the sawing process; this would decrease the total lumber recovery but increase the timber value yield. Air drying must be accelerated to reduce biotic damage in sawn planks. Geometric mean diameter over bark at the smallest end (d) outperforms other measures as a predictor variable for total or structural sawn timber volume.     

Hydraulic architecture correlates with bud organogenesis and primary shoot growth in beech (Fagus sylvatica)

In beech (Fagus sylvatica L.), the number of leaf primordia preformed in the buds determines the length and the type (long versus short) of annual growth units, and thus, branch growth and architecture. We analyzed the correlation between the number of leaf primordia and the hydraulic conductance of the vascular system connected to the buds. Terminal buds of short growth units and axillary buds of long growth units on lower branches of mature trees were examined. Buds with less than four and more than five leaf primordia formed short and long growth units, respectively. Irrespective of the type of growth unit the bud was formed on, the occurrence of a large number of leaf primordia was associated with high xylem hydraulic conductance. Xylem conductance was correlated to the area of the outermost annual ring. These results suggest that organogenesis and primary growth in buds correlates with secondary growth of the growth units and thus with their hydraulic architecture. Possible causal relationships between the variables are discussed.     

Pedunculate and Sessile Oak (Quercus robur L. and Quercus petraea (Mattuschka) Liebl.): A Review of the Hybrid Controversy

Early nineteenth-century studies of variation in the genus QuercusL., particularly those relating to Pedunculate and Sessile oakby Lasch and Greville, illustrate the confused situation thatawaited the forest botanist. Attempts of that period and laterto explain this condition led to the general acceptance of atheory of unlimited hybridization and introgression betweenthe two species. Experimentation and observations between thethirties and fifties of the present century by Dengler, Høeg,Jones, and others demonstrate the weakness of this popular concept—hence the controversy. More recent investigations by Johnssonand Krahl-Urban, supported by the biometric research of Cousens,Carlisle, and Brown, have helped in the production of a moreaccurate picture of the form and extent of hybridization. Agreat deal still remains to be done to elucidate the naturalfrequency of F₁ hybrids, and backcrossea in different regions.The karyotypes of both species and hybrids have still to bedefined.