Detection and features of wetwood in Quercus mongolica var. grosseserrata

To elucidate the location of water in wetwood, variations in moisture content within a tree of Quercus mongolica var. grosseserrata were observed macroscopically by determination of moisture content and by soft x-ray photography. Then the typical wetwood, which had been precisely located by such macroscopic analysis, was examined further by cryo-scanning electron microscopy. The moisture content varied considerably within the tree trunk, and typical wetwood was detected in limited regions of the heartwood. The distribution of the wetwood did not always correspond to the discoloration of the wood. In the wetwood, almost all the lumina of vessels and fibers were filled with water, while the lumina of ray and axial parenchyma cells were often cavitated. Intercellular spaces produced by deformation of cell walls and radial shakes were filled with water. In addition, tyloses were collapsed and torn in the wetwood, and they did not block the vessel lumina. These results suggest the possibility that vessels and fibers might serve as effective pathways for the accumulation of water in the wetwood.     

沙地樟子松天然林南缘分布区林木竞争、空间格局及其更新特征

以呼伦贝尔沙地樟子松地理分布南缘天然林为研究对象,采用Hegyi竞争指数与点格局等分析方法,研究了沙地樟子松天然林的种群结构、种内竞争、空间格局及幼树更新等特征。结果表明:1)所调查区域天然沙地樟子松纯林处于中幼龄阶段,属增长型种群;2)其竞争指数与对象木胸径服从幂函数关系CI=242.24D~(-1.12)(R~2=0.91);3)幼树在小尺度上呈聚集分布,中树与大树在中大尺度上呈随机分布;幼树与中树在小尺度上呈正相关性,中树与大树在小尺度呈负相关性;4)竞争指数与更新幼树和存活更新幼树的密度均呈显著正相关性。在林分管理中需要充分考虑林木竞争、空间格局以及种群更新的关系,本研究可为沙地樟子松天然林的经营管理与保护提供重要的科学依据。     

Comparative study of leaf carbon gain in saplings ofThujopsis dolabrata var.hondai andQuercus mongolica var.grosseserrata in a cool-temperate deciduous forest

Seasonal courses of leaf CO₂ gas exchange in a growing season were examined in saplings ofThujopsis dolabrata var.hondai andQuercus mongolica var.grosseserrata in a cool temperate deciduous forest. Between the two tree species there were no large differences in the light compensation point of leaf photosynthesis, except for the season of new leaf expansion. However, light-saturated rates of net photosynthesis were obviously high inT. dolabrata var.hondai. EvergreenT. dolabrata var.hondai saplings had large photosynthetic production in two seasons, before the emergence of new foliage and after foliage fall of the overstory deciduous trees, because of the significantly high solar radiant energy penetrating under the forest canopy during the seasons. Saplings of deciduousQ. mongolica var.grosseserrata were heavily shaded throughout the growing season by foliage of the overstory trees, which resulted in a low daily surplus production. The annual surplus production of leaves in the growing season was estimated to be 2300 mmol CO₂ m⁻² inT. dolabrata var.hondai and −100 mmol CO₂ m⁻², slightly negative, inQ. mongolica var.grosseserrata. These results supported the high survivability ofT. dolabrata var.hondai saplings and the high mortality ofQ. mongolica var.grosseserrata in the deciduous forest.     

Biomass and production of a naturally regenerated oak forest in southern Korea

Biomass and production of two stands with Quercus variabilis Bl. as the dominant species (stands 1 and 3) and one with Q. mongolica Fisch. as the dominant species (stand 2) were investigated in southern Korea. Stands 1 and 3 naturally occurred on sites with southerly aspects while stand 2 naturally occurred on northerly aspects; stand ages were similar for the three stands (36–38 years old). Total above- and belowground biomass including understory vegetation (Mg ha^–1) was 108.4 for stand 1, 115.6 for stand 2, and 132.0 for stand 3, respectively. Understory vegetation constituted 17.4% of the total biomass in stand 1 but only 3.7–4.5% in stand 2 and stand 3. Roots constituted 20.1–24.6% of the biomass of the overstory vegetation. Although stand 3 showed the highest total biomass, net production was highest in stand 2 at 12.6 (Mg ha^–1 year^–1); net production levels for stands 1 and 3 were 11.7 and 11.1 (Mg ha^–1 year^–1), respectively. It appeared that the differences in site conditions related to aspect influenced the distribution of naturally regenerated oak species within a relatively small area and resulted in differences in biomass and production among the stands.     

Tree growth,mortality, and above-ground biomass accumulation in a holm oak forest under a five-year experimental field drought

A holm oak forest was exposed to an experimental drought during 5 years to elucidate the growth responses of the dominant species Quercus ilex, Arbutus unedo and Phillyrea latifolia. Soil water availability was partially reduced, about 15% as predicted for this area for the next decades by GCM and ecophysiological models, by plastic strips intercepting rainfall and by ditch exclusion of water runoff. The stem diameter increment was highly correlated with annual rainfall in all species, and drought treatment strongly reduced the diameter increment of Q. ilex (41%) and specially of A. unedo (63%), the species showing higher growth rates. Stem mortality rates were highly correlated with previous stem density, but drought treatment increased mortality rates in all species. Q. ilex showed the highest mortality rates (9% and 18% in control and drought plots, respectively), and P. latifolia experienced the lowest mortality rates (1% and 3% in control and drought plots, respectively). Drought strongly reduced the increment of live aboveground biomass during these 5 years (83%). A. unedo and Q. ilex experienced a high reduction in biomass increment by drought, whereas P. latifolia biomass increment was insensitive to drought. The different sensitivity to drought of the dominant species of the holm oak forest may be very important determining their future development and distribution in a drier environment as expected in Mediterranean areas for the next decades. These drier conditions could thus have strong effects on structure (species composition) and functioning (carbon uptake and biomass accumulation) of these Mediterranean forests.     

降水变化和种间竞争对红松和蒙古栎幼苗生长的影响

针对全球变暖导致的降水格局的变化,选择长白山红松针阔叶混交林主要树种蒙古栎和红松幼苗为研究对象,在野外自然条件下人工模拟增、减水30%对单种和混种的针阔叶树种形态、生长和生物量分配的影响. 结果表明：对于蒙古栎幼苗,与单种处理相比,混种显著增加了其冠幅和主根长,与对照处理相比,减水处理显著提高了其茎质比、降低了其主根长; 对于红松幼苗,与单种处理相比,混种显著减少了其基径、树高、叶片数和根、茎、叶质量及总干质量,与对照处理相比,减水处理显著降低了其主根长、叶片数、叶质量和总干质量以及叶质比,同时显著提高了茎质比. 增水处理对二者的影响均不显著. 在树木生长初期,种间竞争和降水格局变化对蒙古栎和红松幼苗形态和生长均产生显著影响,对红松幼苗的影响更大.     

蒙古栎次生林的生长更新与林下植被多样性对林分密度的响应

以辽宁省抚顺市清源县蒙古栎天然次生林为对象,在2018年对6块面积为0.1 hm²的蒙古栎样地进行疏伐,并于2020年调查样地内植被的生长情况,研究疏伐后形成的600(低密度)、720(中密度)、900株·hm^-2(高密度)3种密度对林木生长、林下实生苗更新与林下植被多样性的影响。结果表明: 由于疏伐后间隔年份较短,不同密度下树高、胸径无显著差异。但低密度下林冠对称指数显著高于高密度,表明树冠生长对于林分密度的响应比树干生长更迅速。中密度下实生更新苗数量最多,且相同苗高的实生苗地径显著高于其他两个密度,中密度下实生苗更新与幼苗生长都好于高、低密度。林中共有植物70种,隶属于41科67属,其中木本植物蒙古栎、胡枝子与草本植物山罗花、三叶委陵菜占优势地位。灌木层与草本层的优势度指数、均匀度指数和多样性指数在中密度下表现最佳,表明该立地条件下林分密度保持在720株·hm^-2时更有助于辽东山区蒙古栎次生林的可持续发展。     

Post-fire, seasonal and annual dynamics of the ectomycorrhizal community in a Quercus ilex L. forest over a 3-year period

Two study plots, burned and control, were established in autumn 1998 in a Quercus ilex forest located in northern Spain, part of which had been affected by a low intensity fire in 1994. Soil samples for ectomycorrhizae (ECM) were taken over a 3-year period in each study plot in spring, summer, autumn and winter. ECM morphotypes were identified and the relative abundance of each morphotype in each soil sample calculated, along with species richness, Shannon diversity index and percentage of mycorrhization in each soil sample. The relative abundance of certain ECM morphotypes differed between burned and control plots, and the percentage of mycorrhizal tips was significantly lower in the burned than in the control plot. Nevertheless, there were no significant differences in the diversity, species richness or species composition of the ECM community in the burned and control plots. The dominant ECM morphotypes in both stands were Cenococcum geophilum and several thelephoroid fungi. Sphaerosporella brunnea and Pisolithus tinctorius thrived especially in the burned plot, whereas three ectomycorrhizal morphotypes assigned to the genus Hebeloma were especially abundant in the control plot. There was no significant variation in the relative abundance of the ECM morphotypes between seasons, but ECM community species richness was highest in autumn and lowest in summer. The percentage of mycorrhizal tips reached a maximum in winter, with its minimum in autumn. Collection of samples over the 3-year period also enabled us to detect a significant increase in percentage of ECM colonisation in the burned stand over time.     

Stand dynamics during a 12-year period in a second-growth stand in a cool temperature forest in northern Japan

In 1981 and 1993, trees over 2 m high were measured and mapped to clarify stand dynamics in two permanent plots of 0.1 ha in a secondary, cool temperate, mixed broadleaf/conifer forest after logging in the Tomakomai Experiment Forest, central Hokkaido, northern Japan. The species could be placed in two groups according to the change in basal area and density, and annual height growth:Quercus mongolica var.grosseserrata, Phellodendron amurense, Prunus sargentii andTilia japonica (Group I: GI) showed episodic regeneration and/or fast height growth;Acer mono, Acer palmatum var.matsumuae andSorbus alnifolia (Group II: GII) showed continuous regeneration and/or slow height growth. The age distribution of stems over 10 cm in d.b.h. suggests synchronous regeneration of GI and GII species. Vertical stratification was promoted during the 12-year period by the difference in annual height growth between the two species groups. Additional tree censuses in both remnant old-growth stands and second-growth stands after large scale blowdowns demonstrated thatQ. mongolica var.grosseserrata is most dominant in stands varying in the stages of development. Disturbance history and successional trends in dominant species implied that stand-devastating disturbances were responsible for the regeneration ofQ. mongolica var.grosseserrata in the study forest.     

Notes on Quercus ilex L. in Liguria (NW Italy)

The climatic characteristics of the Liguria region have been outlined by means of raw data and derived indices (water balance related to potential evapotraspiration, Rivas-Martinez's index of mediterraneity and thermicity, De Martonne's index of dryness, and Emberger's pluviothermic quotient and index of summer dryness). Their interpretation suggests that Liguria is a boundary region between two different climatic areas: the Mediterranean and that of Central Europe.The distribution of Quercus ilex communities in Liguria have suffered the heavy consequences of human activity on the coastal belt of the region. There is, however, sufficient evidence to show that their presence is closely linked to climatic conditions. Quercus ilex communities are absent from the western coastal belt where the annual water balance is below –50 mm and high mean temperatures occur. They are also absent from marly limestone dominated areas where annual water balance is below 300 mm. Quercus ilex woods show a preference for water balance values between 0 and 600, with the better developed forests being found in central and eastern coastal Liguria.The Ligurian Quercus ilex woods are ascribed to Quercetum ilicis Br.-Bl. 1915. Given that the presence within their floristic composition of a group of species of Querco-Fagetea (more species in eastern stands, few in western ones) is an almost constant characteristic, the subass. fraxino-ostryetosum Mariotti 1984 can be retained for many of them. Quercus ilex is not present in the initial succession stages of Mediterranean Liguria vegetation. It can be found in later stages when the vegetation is more fully developed towards a maquis type structure. In this case it tends to become dominant and the community develops (if no fire or other human interference occurs) into a Quercus ilex forest. Frequently, this succession takes place under an old tree layer cover (generally Pinus sp.), a remanant of man's past management of the vegetation in the area.     

Comparison between the soil seed banks of a burnt and an unburnt Quercus pyrenaica Willd. forest

Soil samples from burnt and unburnt sites dominated by Quercus pyrenaica Willd. forest in León province (NW Spain) were collected, separated into an upper layer (0–2 cm depth) from a lower layer (2–5 cm), put in a greenhouse, and seeds allowed to germinate.A total of 670 identified seedlings comprising 56 species and belonging to 24 families were recorded. Most seedling were herbaceous perennials (hemicryptophytes: 59%), followed by annuals (therophytes: 23%). Many species that germinated from buried seeds were not observed as plants at any site, and came from exogenous communities. The principal means of seed dissemination were anemochory (45%) and autochory (23%).The number of species as well as seedlings was not significantly different between soils from the burnt and unburnt sites, but seedlings were more numerous in samples from the unburnt sites, as the number of seedlings was always highest in the upper soil layer. Germination behaviour of four particular species was characterized.Seedlings from the seed bank temporarily were found in the early stages of recovery of the burnt Quercus pyrenaica forests.     

Studies on litter decomposition processes in a temperate forest ecosystem. I. Change of organic matter in oak (Quercus liaotungensis Koidz.) twigs

The litter bag method was used in this study on the decomposition of twigs of an oak (Quercus liaotungensis Koidz.) which is dominant in the warm temperate deciduous forests. This continual 5-year investigation was to measure the changes of organic compounds in twig litter. The decomposition of oak twigs based on rates of the mass loss during the first 5 years was simulated using the Olson exponential equation. The simulated data fitted well with the observed values. Oak twigs were predicted to reach 95% mass loss within 21 years. During the first 5 years, the concentration of protein in the remaining litter increased from 3.5% to 5.5%, while the concentration of hemicellulose decreased from 16.0% to 8.0%. However, there was no obvious change in the concentrations of lignin and cellulose. The losses of lignin, crude-cellulose and hemicellulose could be well simulated using the Olson exponential equation. However, this was not true for cellulose and protein.     

Influence of root temperature on growth of Pinus sylvestris,Fagus sylvatica,Tilia cordata and Quercus robur

One-year-old tree seedlings were incubated in a greenhouse from April to July, under natural daylight conditions, with their root systems at constant temperatures of 5, 10, 15, 20, 25, 30 and 35 °C and with the above ground parts kept at a constant air temperature of 18–20 °C. The course of height growth, total mass increment, root, shoot and leaf weight as well as leaf areas were measured. The results indicate that clear differences exist in the optimal root zone temperatures for various growth parameters in different tree species. Pinus sylvestris had a maximal height increment at about 5–10 °C and maximal total mass increment at 15 °C root temperature. In contrast, the optimum for Quercus robur was at 25 °C. Tilia cordata and Fagus sylvatica had their optima for most growth parameters at 20 °C. The root temperature apparently indirectly influenced photosynthesis (dry weight accumulation) and respiration loss. From the observed symptoms and indications in the literature it seems probable that a change in hormone levels is involved as the main factor in the described effects. Variation of root temperature had only an insignificant effect on bud burst and the time at which the shoots sprouted. Apparently species of northern origin seem to have lower root temperature optima than those of more southern origin. This is to be verified by investigation of other tree species.     

纳塔栎和柳叶栎对铅锌矿区污染土壤的修复潜力分析:田间试验

通过野外调查、采样和实验室分析方法,研究优新景观树种纳塔栎（Quercus nuttallii）和柳叶栎（Quercus phellos）对湖南郴州Pb、Zn矿区复合污染土壤的适应性和修复潜力。试验设计A、B、E区种植1年生纳塔栎,C、D区种植1年生柳叶栎,1年后测量株高、地径、生物量等生长指标,随机采集植物全株及根际土壤,测试植物根际土壤和树木组织中的重金属含量。试验结果：Pb、Zn矿区土壤受到重金属Cd、Pb、Zn和As的复合污染,不同区域的土壤表现出污染异质性,采用单污染指数（Pi）和内梅罗指数（P_N）评价不同地块的污染程度,A区尾矿库（P_N=20.08）和B区（P_N=3.14）为重度复合污染,C区（P_N=2.43）为中度复合污染,D区（P_N=1.55）和E区（P_N=1.07）为轻微污染。纳塔栎和柳叶栎在以上不同污染地块均能正常生长,株高、地径和生物量与复合污染指数（内梅罗指数）及重金属含量呈负相关。其中纳塔栎对Cd的生物富集系数（BCF）在A、B、E区分别为6.27-8.37、3.67-4.38、42.93-52.75,高于C、D区柳叶栎对Cd的生物富集系数1.79-2.15、0.89-1.07。B-E区Zn的转运系数（TF）在1.79-2.28之间,A区Zn的转运系数为0.43。结论：纳塔栎和柳叶栎表现出较强的重金属耐性,对Cd具有较高的生物富集能力,对Zn具有较高的转运能力。其中纳塔栎对重金属积累能力较强,可作为亚热带地区铅锌矿区Cd、Pb、Zn、As复合污染土壤的植被恢复及生态修复候选树种。     

Early seedling growth of pine (Pinus densiflora) and oaks (Quercus serrata,Q. mongolica,Q. variabilis) in response to light intensity and soil moisture

In climatic chambers seed germination and seedling growth of Pinus densiflora Sieb. et Zucc., Quercus serrata Thunb., Quercus mongolica Fisch. ex Turcz. and Quercus variablilis Bl. were investigated as functions of light intensity and soil moisture. In Korea these tree species occur widely and form mixed forests with different distributions. Species clearly differed in the pattern of germination and early seedling growth between light and soil treatments. The germination of pine did not differ between the experimental treatments until the breaking of the primary buds. After that, light intensity was the deciding factor for further development. In the most moist treatment (approx. field capacity) growth of the pine seedlings was strongly inhibited. For the three oak species, differences between experimental treatments first occurred after complete formation of primary leaves. Seed development strongly correlated with the weight of the acorn. The large seeded Q. variabilis (acorns with mean weight of 4.7 g) developed faster and reached larger dimensions towards the end of the experiment than Q. mongolica (2.8 g per acorn) and Q. serrata (0.9 g per acorn). Regarding height and biomass growth, the oak species showed a higher shade tolerance than pine. The proleptic shoot growth was clearly influenced by the light intensity. Root formation was favoured by a high exposure to light. In case of the oak species reduction of soil moisture increased the length of primary roots and the number of secondary roots.     

Effects of forest-floor avalanche disturbance on the structure and dynamics of a subalpine forest near the forest limit on Mt. Fuji

In subalpine forests near the forest limit on Mt. Fuji in central Japan, slush avalanches occasionally destroy forest-floor vegetation through an influx of volcanic gravel from bare upper sites. The vegetation structure of Larix kaempferi–Abies veitchii forests near and distant from avalanche paths was investigated to determine the effects of forest-floor disturbance on successional processes. The Larix population in a forest near an avalanche path, where there had been signs of forest-floor disturbance by avalanches, had a discontinuous age structure with three age groups, indicating that Larix seedlings established under the Larix canopy after the forest-floor disturbance. In contrast, the Larix population in a forest distant from avalanche paths, where there had been no forest-floor disturbance, had a continuous age structure, with no plants younger than the 90-year-old trees, indicating that this population had established on bare ground over a long period. These data suggest that the primary requirement for the regeneration of L. kaempferi on the forest floor is a mineral substrate. Conversely, A. veitchii had a continuous age structure in both forests. However, forest-floor disturbances by avalanche(s) may exclude A. veitchii from the forest because A. veitchii is very sensitive to scoria deposition. In conclusion, forest-floor disturbance by avalanche(s) provides L. kaempferi with an opportunity to establish on the forest floor, resulting in the maintenance of Larix forests alongside avalanche paths in the upper subalpine area on Mt. Fuji.     

Annual and seasonal changes in fine root biomass of a Quercus ilex L. forest

The biomass, production and mortality of fine roots (roots with diameter <2.5 mm) were studied in a typical Mediterranean holm oak (Quercus ilex L.) forest in NE Spain using the minirhizotron methodology. A total of 1212 roots were monitored between June of 1994 and March of 1997. Mean annual fine root biomass in the holm oak forest of Prades was 71±8 g m^–2 yr^–1. Mean annual production for the period analysed was 260+11 g m^–2 yr^–1. Mortality was similar to production, with a mean value of 253±3 g m^–2 yr^–1. Seasonal fine root biomass presented a cyclic behaviour, with higher values in autumn and winter and lower in spring and summer. Production was highest in winter, and mortality in spring. In summer, production and mortality values were the lowest for the year. Production values in autumn and spring were very similar. The vertical distribution of fine root biomass decreased with increasing depth except for the top 10–20 cm, where values were lower than immediately below. Production and mortality values were similar between 10 and 50 cm depth. In the 0–10 cm and the 50–60 cm depth intervals, both production and mortality were lower.     

Ramet size equalisation in a clonal plant,Phragmites australis

The influence of shading from older generations of dead culms (standing litter) on density, growth rate and development of size structure at the ramet level was investigated in a pure stand of Phragmites australis by experimental neutral shading of plots after removal of standing litter. Initial differences in height distribution between autumn and spring cohorts disappeared in the course of shoot growth. The Gini coefficients of shoot heights and estimated shoot weights indicated that the size structure of the shoots became more equal with increasing mean size in both shaded and unshaded plots. Relative growth rate for height (RHGR) and weight of individual shoots was negatively related to shoot size during the early and presumably storage-dependent growth period, suggesting a strong support for growth of smaller shoots. No etiolation was indicated by mean or maximum height in shaded and unshaded plots, or by the relationship between shoot height and weight. Mean shoot density was significantly lower in shaded than in unshaded plots in one of two shade treatment years. A regression model indicated a small but significant effect of shoot density on the approximately linear relationship between RHGR and the logarithm of height. The growth rate of small shoots was slightly larger at low than at high shoot density. Therefore, it is suggested that the shade from standing litter in P. australis stands can decrease shoot natality in the spring cohort, and thereby increase the support to fewer small shoots.     

Phenological and growth patterns of the Mediterranean oak Quercus suber L.

The phenology of Quercus suber L., a dominant species of the montados in the Iberian Peninsula, was studied for 2 years in southwest Portugal. The seasonal progression of phenological events was analyzed in seven trees. Selected branches were examined monthly for shoot elongation, leaf number, branching, flowering, and fruiting. Radial stem growth and specific leaf weight were also studied. Active growth was observed from early spring to early summer. Reserves accumulated during winter and high photosynthetic activity in early spring apparently supported this strong development. The growth flush started with stem radial increment, which seemed to be impaired by spring rainfall. Male inflorescence production was the next phenological event. Old leaves were shed during new twig and leaf emergence. Shoot elongation and the number of new leaves produced were well correlated with the previous-year shoot's length, and were not clearly related to climatic factors. Radial growth resumed in autumn at a lower rate than in the previous spring, a possible consequence of a reserve depletion due to lower photosynthetic production in summer and investment on fruit maturation, which was complete by late autumn. Premature and excessive new leaf production were apparently subjected to self-pruning strategies related to the development of each tree's crown. Younger cork-oaks produced shorter and fewer shoots per module, and more sclerophyllous leaves than the older ones. A high intra-specific variability was observed in all the results.