Success factors for high-quality oak forest(Quercus robur, Q. petraea) regeneration

Background: Within the framework of close-to-nature forestry, oak forest(Quercus robur, Q. petraea) regeneration techniques that consider both silvicultural and nature conservation demands have become a very important issue.While there are many experimental and local studies that aim at disentangling the relationships between different environmental and silvicultural factors and the success of oak regeneration, systematic supra-regional studies at the greater landscape level are missing so far.Against this background, the first objective(a) of this study was to present an efficient and sufficiently accurate sampling scheme for supra-regional forest regrowth inventories, which we applied to young oaks stands. The second, and major, objective(b) was to identify the crucial success factors for high-quality oak forest regeneration in northwest Germany.Results: Objective(a): Factors that have been identified as potentially crucial for the success or failure of oak regeneration were either included in a field inventory procedure or extracted from forest inventory databases. We found that the collected data were suitable to be analyzed in a three-step success model, which was aimed at identifying the crucial success factors for high-quality oak forest regeneration.Objective(b): Our modeling procedure, which included a Bayesian estimation approach with spike-and-slab priors,revealed that competitive pressure from the secondary tree species was the most decisive success factor;no competition, or low competition by secondary tree species appeared to be particularly beneficial for the success of high-quality oak regeneration. Also fencing and the absence of competitive vegetation(weeds, grass, bracken)seemed to be beneficial factors for the success of oak regeneration.Conclusions: Trusting in biological automation was found to be mostly useless regarding economically viable oak forest regeneration. To efficiently organize oak regeneration planning and silvicultural decision-making within a forest enterprise, it is strongly recommended to initially evaluate the annual financial and personnel capacities for carrying out young growth tending or pre-commercial thinning and only then to decide on the extent of regenerated oak stands. Careful and adaptive regeneration planning is also indispensable to secure the long-term ecological continuity in oak forests. Oak regeneration should therefore preferably take place within the close vicinity of old oak stands or directly in them. The retention of habitat trees is urgently advised.

Growth phenology adjusts to seasonal changes in water availability in coexisting evergreen and deciduous mediterranean oaks

Different leaf(evergreen vs.deciduous habit)and xylem(diffuse-vs.ring-porous wood)traits represent contrasting strategies to face seasonal changes in water availability and temperature.However,how contrasting leaf and xylem habits of coexisting tree species affect stem wood formation and tree-ring development remains poorly understood.Here,we investigated the spatio-temporal patterns of wood formation in two deciduous oaks(Quercus faginea and Quercus petraea)and two evergreen oaks(Quercus ilex and Quercus suber)coexisting in seasonally dry Mediterranean forests along an aridity gradient in Spain.We hypothesized that growth responses to drought and intra-and inter-annual growth patterns would differ between functional groups.We simulated intra-and interannual growth using a modified version of the Vaganov-Shashkin(VS)process-based,growth model.The VS model simulations were used to estimate growth changes under a high emission scenario(RCP 8.5)for the current distribution of the study oak species and to forecast their future performance under warm(4.8℃)conditions in the Iberian Peninsula.Our simulations indicate that climate warming would induce a shortening of the ringgrowth season and a reduction of radial growth in evergreen and deciduous Mediterranean oaks,particularly in dry sites from southern and eastern Iberia currently occupied by Q.ilex and Q.faginea.Evergreen oaks may better recover after dry periods than deciduous oaks by resuming growth after the summer drought.Low soil water availability in spring would be more detrimental to growth of deciduous oaks.Process-based growth models should be refined and validated to better forecast changes in tree growth as a function of climate.

Production of micro-cuttings from acorns to test the plasticity of response to contrasting soil water regimes

We collected acorns from selected Quercus robur and Quercus petraea mother trees growing at sta- tions with different depths to the water table. We produced pairs of micro-cuttings from these single acorns. The obtained pairs of cuttings represented phenotypes of high similarity according to photosynthetic parameters. These pairs of cuttings were used to test the plasticity of response to contrasting water regimes. For each pair, one cutting was submitted to drought and the other was submitted to waterlogging. Drought response was recorded according to gas exchange traits （stomatal closure and water use effi- ciency）. The response to waterlogging was recorded according to the capacity to form hypertrophied lenticels and to maintain the CO2 assimilation rate. Intermediary phenotypes presenting both high water use efficiency and the capacity to develop hypertrophied lenticels were expected.

Removing harvest residues from hardwood stands affects tree growth, wood density and stem wood nutrient concentration in European beech (Fagus sylvatica) and oak (Quercus spp.)

Background:Higher exportation of harvest residues from forests due to increased demand for woody biomass,has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth.However,as nutrients become less available in the soil,the remobilization of nutrients in biomass tissues(plant internal cycling)helps sustain tree nutrition.Our study aims to quantify the impact of Removing Harvest Residues and Litter(RHRL)during five years on tree growth,wood density,and stem wood nutrient concentrations in young beech and oak forest stands.Result:Our study found that,RHRL significantly decreased tree growth ring width by 14%,and wood density by 3%,in beech trees,in near bark rings.RHRL also significantly reduced nutrient concentration in near bark and near pith areas of both studied species.Mg,Na and S were found lower by 44%,76%,and 56%,respectively,in near bark area of beech trees.In near bark area of oak trees,K,Ca,Mg,Na,S,and Fe were lower by 20%,25%,41%,48%,41%,and 16%,respectively.K and Mg concentrations decreased more strongly in near pith area compared to near bark area suggesting internal translocation of these two elements.Conclusion:In beech trees,wood density proved to be an important factor while quantifying the effect of removing harvest residuals on tree growth and biomass.Soil nutrient loss intensified the remobilization of nutrients con-tained in older tree rings(close to the pith)towards newly formed rings(close to bark).In our study,in beech trees,K was found to be the most recycled major nutrient.These results demonstrate the potential of such analysis for providing valuable insight into the effect of RHRL in premature stands on the physiological adaptive strategies of trees and an indication of soil fertility status.

Affiliation of Dihydrolipoyl Dehydrogenase Allozymes in Mycorrhizae of European Forest Trees and Characterization of the Enzyme of the Matt Bolete (<i>Xerocomus pruinatus</i>) and the Bay Bolete (<i>X. badius</i>)

Mycorrhizal roots of the deciduous trees European beech (Fagus sylvatica (L.)) and Sessile oak (Quercus petraea (MattuschkaLiebl.)) and the conifers Norway spruce (Picea abies (L.) H. Karst.) and European larch (Larix decidua (Mill.)) associated with the ectomycorrhizal fungi matt bolete (Xerocomus pruinatus (Fries 1835)) or bay bolete (X. badius (Fries 1818)) were analysed with respect to the occurrence of dihydrolipoyl dehydrogenase (EC 1.8.1.4) allozymes. In root tissues of the two deciduous trees, two gene loci could be visualized after cellulose acetate electrophoresis while three loci were expressed in root tissues of the two coniferous species. The two fungal species and further ectomycorrhizal fungi expressed exclusively one dihydrolipoyl dehydrogenase gene. In Xerocomus pruinatus and X. badius, the dihydrolipoyl dehydrogenase gene consists of 1460 bp and 1370 bp, respectively, including five introns each consisting of 52 bp. Their DNA sequences correspond to 70 to 90% to other fungal dihydrolipoyl dehydrogenase genes. One monomer of the dimeric dihydrolipoyl dehydrogenase enzyme consists of 486 (X. pruinatus) or 454 (X. badius) amino acids which sum up to a molecular mass of 55 kDa (X. pruinatus), respectively 52 kDa (X. badius). The number of positively charged amino acid residues makes 79 (X. pruinatus) and 68 (X. badius) and the number of negatively charged amino acid residues was calculated to make 46 (X. pruinatus) and 48 (X. badius);isoelectric points make 9.99 (X. pruinatus) and 9.68 (X. badius). Calculated three dimensional structures reveal a short NADH binding site being part of a larger FAD-binding site and a binding/dimerization domain.

中国兰科羊耳蒜属新记录种——岩生羊耳蒜及其独特的珠芽繁殖方式

报道了中国兰科(Orchidaceae)羊耳蒜属(Liparis Rich.)植物一新记录种——岩生羊耳蒜(Liparis petraea),并提供了其形态描述及彩色图片,凭证标本保存于广西植物研究所标本馆(IBK)。岩生羊耳蒜与见血青(L.nervosa)在形态上相近,但前者叶银灰绿色,叶面平展,唇瓣基部胼胝体为短圆柱状突起,植株通常具珠芽而易与后者区分。岩生羊耳蒜居群内个体呈聚集式分布,并与其具有的珠芽繁殖方式相关。

四种栎树EST-SSR信息分析

为开发栎属遗传多样性检测的SSR标记,分析了蒙古栎、无梗花栎、夏栎和欧洲栓皮栎EST-SSR的特点,结果表明蒙古栎的EST中3 209.46 bp有一个SSR,无梗花栎中每6 160.36 bp有一个SSR、夏栎中每5 883.30 bp有一个SSR,欧洲栓皮栎中每6 129.12 bp有一个SSR。蒙古栎、无梗花栎、夏栎和欧洲栓皮栎EST-SSR的平均长度分别为21.65 bp、21.1 bp、20.66 bp和20.65 bp。四种栎类中不同基元的EST-SSR的分布频率具有非常一致的特征,均是二基元、三基元和六基元的SSR分布频率最高,达20%以上。而四基元和五基元的SSR在四个种类中的分布不到0.05%。二基元的SSR中大于1%的SSR均是AG、CT、TC、GA、AT、TA基元,并且在蒙古栎、无梗花栎和夏栎中AG、CT、TC基元的分布频率最高,而在欧洲栓皮栎中是TC、GA、AG的分布频率最高;三基元的SSR中,含CAA、GAA、TCT、CTT的SSR在四种栎类中都存在。六基元的SSR中大于1%在四种栎类中出现的类型均较少,为0～4种。

Sessile oak forest plant community changes on the NE Iberian Peninsula over recent decades

Aims Our aims were 3-fold:(i)to determine whether global change has altered the composition and structure of the plant community found in the sessile oak forests on the NE Iberian Peninsula over the last decades,(ii)to establish whether the decline in forest exploitation activities that has taken place since the mid-20th century has had any effect on the forests and(iii)to ascertain whether there is any evidence of impact from climate warming.Methods We assess changes in the plant community by comparing a cur-rent survey of sessile oak forest with a historical data set obtained from previous regional studies dating from 1962 to 1977.We ana-lyse the regional changes in the community in terms of biodiversity variables,species composition and plant traits.Furthermore,plants traits such as plant life forms and chorological groups are used to discern any effects from land-use changes and climate warming on the plant community.Important Findingsthere has been a loss of diversity in the community and,in the hottest region,there is also a loss of species richness.the composition of the community suggests that,although significant changes have taken place over recent decades,these changes differ between regions as a result of the low impact global change has had in the western regions.For instance,while the tree canopy cover in the western sessile oak forests remains stable,the eastern sessile oak forests are still recovering from the former exploitation that led to a loss of their rich and abundant herbaceous stratum.In fact,the recovery process in the catalan Pre-coastal Range has constituted an increase in the Euro-Siberian plants typical to this community.Moreover,in the eastern forests,there is evidence that climate warming has impacted the thermophilization of the sessile oak forests found on the coastal Range.