Morphological and physiological acclimation of Quercus coccifera L. seedlings to water availability and growing medium

One of the main constraints of reforestation in the Mediterranean region is low summer water availability during the first years after out planting. Plant water availability depends on the precipitation regime, but also on the physical properties of the soil. Higher survival rates result when seedlings are soil acclimated. Our main goal was to describe the morpho-physiological responses of 6-, 10- and 18-month-old Quercus coccifera seedlings growing in a natural soil (terra rossa) or a standard nursery growing medium, and to assess in the nursery if seedlings growing in natural soil were more resistant to deficit irrigation. The high growth rate achieved after 10?C18 months by terra rossa-grown seedlings in contrast with those grown in the nursery substrate suggests that the former were acclimated to the soil. Higher photosynthetic rate (A), transpiration (E) and stomatal conductance (g_s) were observed in terra rossa seedlings, mainly during the first months. The higher carbon availability may account for the higher root nitrogen concentration in terra rossa-grown seedlings, which could favor their later field growth. Low-watered seedlings showed a certain degree of hardening, since after 18 months, they showed higher A, E, g_s and lower photoinhibition than well-watered seedlings, likely attributable to the sharp leaf-to-root biomass ratio reduction. Carbon isotope discrimination (??) values were similar to those of well-watered plants and indicated a non-stomatal component as the main factor controlling photosynthesis in these leaves. Eighteen-month-old low irrigated seedlings had the highest mortality. Overall, results suggest that nursery terra rossa-acclimated Q. coccifera seedlings with improved physiological status and hydraulic soil-root continuity would have a higher survival rate in the field.     

The growth of shoots and lateral roots of Quercus robur L. seedlings following simulated undercutting

The effect of cutting the tap root on shoot growth and development of lateral roots was observed in seedling Quercus robur L. growing in PVC tubes containing peat and perlite. Cutting the tap root had little effect on shoot height and leaf number although some treatments caused a significant but slight reduction in shoot dry weight and number of branches. Total root dry weight was similar in control and treated plants but distributed differently between the types of root present. The tap root always formed the largest part of the total root dry weight. In control plants most lateral root dry weight was in roots < 1 mm diameter whereas in treated plants most dry weight was in roots > 1 mm diameter. Development of the root system following root cutting was similar for all treatments: new long laterals > 1 mm diameter with relatively few branches, that formed replacement tap roots, developed near the cut end of the original tap root. Fine laterals (< 1 mm diameter) near the root collar continued to grow forming highly branched systems.     

The Timing of Canopy and Epicormic shoot growth in Quercus robur L.

The sequence and timing of shoot development from buds on thebranches and trunk of Quercus robur were observed over 2 years.Shoots on crown branches began development before those on existingepicormic branches but both stopped growing at about the sametime. Epicormic buds on the trunk began expanding 3–4weeks after crown buds, and finished growth 3 weeks later. Theseobservations do not support previous claims that new epicormicshoots grow before development of the canopy.     

Root growth enhancement by rhizospheric aluminum treatment in Quercus serrata Thunb. seedlings

This article discusses the effect of aluminum on root growth of Querucus serrata Thunb. In a 9-week hydroponics experiment, the effects of various concentrations (0 to 5.0 mM) of Al on root growth were examined. Results revealed that root biomass increases with the increase in Al concentration up to 2.5 mM, and then it tended to decrease. In the next experiment, the effects of H⁺ and Al³⁺ on roots were compared in a 4-week hydroponics experiment using three treatment solutions: control (pH 6.0), −Al (without Al, pH 3.5), and +Al (with 2.5 mM Al, pH 3.5). No clear difference in the biomass and root length between the control and −Al treated roots was observed, and root and shoot biomass were increased by Al treatment. These results confirmed that the H⁺ concentration level, at a pH of 3.5, is not toxic for Q. serrata and the Al-induced increase in root biomass is not caused by the amelioration of H⁺ toxicity by Al. In the third experiment, roots were exposed to an Al solution (pH 3.6) intermittently. This treatment clarified that Al stimulated rooting and root elongation. In the fourth experiment, the effect of 1 mM Al on root growth during a 15-month period in a sand culture were examined. This experiment confirmed that Al stimulated good growth and development of root systems at appropriate concentrations. Therefore, it is considered that Al-induced root growth enhancement occurs as a long-term and short-term phenomenon.     

Effects of treeshelters and polyethylene mulch sheets on survival and growth of cork oak (Quercus suber L.) seedlings planted in northwestern Tunisia

Success of plantation establishment depends on the ability of seedlings to withstand animal browsing and competition from vegetation. This study in northwestern Tunisia examined the influence of browsing protection and vegetation control on seedling mortality, diameter, and height growth components of an evergreen sclerophyllous oak species, cork oak (Quercus suber L.) for the first 2 years after planting (2005 and 2006). Browsing protection was controlled by varying both treeshelter type (non-vented, vented, and control) and height (1.2-m and 1.8-m tall). Competing vegetation was controlled through increasing sizes of square-shaped black polyethylene mulch sheets: 0 m, 0.7 m, 1 m and 1.3 m large. Seedling mortality rate was relatively low during the first year (9%) and was not affected by any of the studied factors. During the following year, mortality was lower for seedlings in both types (non-vented and vented) of 1.2-m tall treeshelters than for unsheltered ones. Mortality was only slightly higher for 1.8-m tall shelters than for 1.2-m shelters. Compared to unsheltered seedlings, basal diameter was reduced during both seasons for seedlings inside non-vented treeshelters (1.2-m and 1.8-m tall), whereas for vented shelters it was reduced during the first year and then increased during the second year. Height growth was positively affected by tree shelters during both years. Seedlings inside non-vented 1.8-m tall shelters were the tallest having an average height of up to 140 cm at the end of the second year, while the unsheltered seedlings had only an average height of up to 42 cm. The greater height of the sheltered seedlings was attributed to the increase of: (1) the number of shoot flushes yearly established on the main stem (up to three), and (2) the length of all the growth units produced during each flush. Seedlings inside vented shelters had balanced growth with a low proportion of seedlings unable to support themselves without a stake (7%). However, non-vented shelters had unbalanced height and diameter growths resulting in both a higher height-to-diameter ratio and in a higher proportion of seedlings having stability problems (47%). Polyethylene mulch sheets did not affect early survival, seedling basal diameter, or number of shoot flushes established yearly, but did slightly improve seedling height at the end of the second season, mostly due to the significant improvement in shoot elongation of the first flush. Results suggest that both 1.8 m treeshelters and plastic mulches may enhance the growth of cork oak seedlings planted on harsh sites in northwestern Tunisia.     

淹水胁迫对麻栎苗木生长和生理的影响

采用室内盆栽控制试验,研究了麻栎苗木在不同淹水处理下的生长和生理变化。结果表明,经过1个月的淹水试验,麻栎苗木未出现死亡现象,说明麻栎具有较强的耐水能力;但是不同处理之间的苗木生长和生理性状存在一定差异,主要是淹水处理后的麻栎苗木新梢生长均明显小于对照处理。经淹水处理后苗木叶片含水量、叶绿素含量以及光合速率均明显低于对照处理,但是叶片相对电导率呈相反趋势。淹水后麻栎苗木叶片中的N、P、K含量均比对照低。淹水处理会导致叶片Na含量增加,且随着淹水强度的增强而增加。     

Interactive responses of Quercus suber L. seedlings to light and mild water stress: effects on morphology and gas exchange traits

? The combined effect of water stress and light on seedlings of forest species is a key factor to determine the best silvicultural and afforestation practices in the Mediterranean area.

? The aims of this work was (1) to determine the optimal light level for the early development of cork oak seedlings under mild water stress and (2) to test if the combined effect of water stress and light followed the trade-off, the facilitation or the orthogonal hypothesis.

? Shade reduced instantaneous photosynthetic rates and water use efficiency in cork oak. However, seedlings grown under moderate shade (15% of full sunlight) were capable to accumulate similar amount of biomass than those grown under more illuminated environments by increasing their specific leaf area. Absolute differences in net photosynthesis between light treatments were higher in well watered than in water stressed seedlings. However, the impact of both factors on overall growth was orthogonal.

? We concluded that cork oak development is impaired under deep shade (5% of full sunlight) but it can be optimal under moderate shade (15% of full sunlight) even under moderate water stress. Implications of these patterns on regeneration, cultivation and afforestation of cork oak are discussed.

     

石灰岩山地根瘤菌对台湾相思苗木生长效应

从石灰岩山地不同立地条件的台湾相思林分中采集根瘤并分离获得12株根瘤菌,将其接种到台湾相思盆栽苗木中,5个月后测量苗木的株高、地径、生物量及根瘤结瘤情况。试验结果表明:①在石灰岩山地的台湾相思林分中,根瘤数量较多的是中、下坡,最少的是下坡;单个根瘤平均质量最重的是中坡,上坡和下坡次之,表明石灰岩山地的中坡最适合根瘤菌生长。②供试的12株菌株回接到台湾相思苗木后能全部侵染苗木根部并结成有效根瘤;与对照比较,菌株回接都不同程度地促进台湾相思苗木的株高、地径、生物量的增长,增长幅度分别为1.7%~39.0%、1.7%~18.1%和21.4%~135.7%;根瘤生物量也比对照增长3.04~12.94倍。综合分析结果表明,台4、台10菌株为优良菌株。     

麻栎不同播种量及施肥生理效应的研究

不同播种量及施肥对麻栎苗木生长均有一定影响,从本次试验结果来看,麻栎的适宜播种量为1800kg·hm-2和2250kg·hm-2;麻栎播种苗在不同生长阶段内,N、P含量的高低不仅与施肥量有关,而且与苗木所处物候期、对土壤养分的吸收和利用状况、苗木本身生长节律等密切相关;不同施肥区,麻栎苗木叶绿素含量在速生期时最高,到生长后期相对降低。     

Interactive effects of shade and irrigation on the performance of seedlings of three Mediterranean Quercus species

Shade and irrigation are frequently used to increase the success of Mediterranean Quercus spp. plantations. However, there is controversy about the combined effects of these treatments on plant performance. We assessed the effects of two irradiances (full sunlight and moderate shade) and two summer watering regimes (high (daily) and low (alternate days)) on leaf and whole-plant traits of 1-year-old seedlings of Quercus coccifera, Q. ilex subsp. ballota and Q. faginea grown outdoors for 8.5 months. Leaf traits included measures of morphology, nitrogen concentration, gas exchange and photochemical efficiency, and measures of whole-plant traits included biomass allocation patterns, growth phenology, across-summer leaf area change and relative growth rate (RGR). Moderate shade reduced leaf mass per area, increased photochemical efficiency, maximum carbon assimilation rate (Amax) and allocation to leaves, and prolonged the growing period in one or more of the species. Daily watering in summer increased Amax of Q. ilex and prolonged the growing period of Q. ilex and Q. faginea. Both treatments tended to increase RGR. The effect of shade was greater in the low-watering regime than in the high-watering regime for two of the 15 studied traits, with treatment effects being independent for the remaining 13 traits. Leaf nitrogen and the ability to maintain leaf area after the arid period, rather than biomass allocation traits, explained the variation in seedling RGR. Trait responsiveness to the treatments was low and similar among species and between study scales, being unexpectedly low in Q. faginea leaves. This may be because selective pressures on leaf plasticity act differently in deciduous and evergreen species. We conclude that moderate shade and daily summer watering enhance the performance of Mediterranean Quercus seedlings through species-specific mechanisms.     

Response of Quercus robur L. seedlings to north-south asymmetry of light within gaps in floodplain forests of Slovenia

To examine Quercus robur establishment and growth in low to intermediate light levels, we analysed regeneration in different microsites created by light asymmetry within gaps in two main floodplain forest regions of Slovenia: Dolinsko and Krakovo. Four years after a mast year in 1995, we installed systematic grids of 1×1 m plots in 11 gaps (0.03–0.40 ha) on wet and dry site variants. In 256 plots, seedling species, cover, density, height, height increment, browsing damage, tree architecture, understory vegetation species and cover, and direct and diffuse light were measured. The average seedling density in all gaps was 15/m², but the highest densities were found in gap positions with low diffuse light levels (10–20%). Competing understory vegetation was more abundant in positions with high diffuse light. In gaps on dry site variants a combination of low diffuse and high direct light was favourable for regeneration. The results indicated that Q. robur can successfully establish in gaps. Here, both light components were sources of within gap resource heterogeneity, therefore knowledge of light asymmetry can improve regeneration success.     

Combined effects of pre-hardening and fall fertilization on nitrogen translocation and storage in Quercus variabilis seedlings

Maintaining proper seedling nitrogen status is important for outplanting success. Fall fertilization of evergreen conifer seedlings is a well-known technique for averting nitrogen (N) dilution caused by continued seedling growth during hardening. For deciduous seedlings, this technique is much less understood, and regardless of foliage type, the interaction of N status prior to fall fertilization and the rate of fall fertilization have yet to be fully explored. Therefore, we fertilized Quercus variabilis container seedlings with either 25, 100, or 150 mg total N seedling^?1, applied exponentially, during a 23-week pre-hardening regime, followed by either 0, 12, or 24 mg total N seedling^?1 applied during hardening (i.e., fall fertilization) in equal aliquots for 4 weeks. For seedlings without supplemental N during hardening, N concentration in stems and roots increased significantly despite substantial growth. The absence of N dilution was attributed to N translocation from foliage to these tissues, which was independent of pre-hardening N status. Overall, 32 % of foliar N was translocated and accounted for 75 % of the total N increase in stems and roots. Final stem N status was a function of pre-hardening fertilization, whereas root N concentration was affected by the interaction of pre-hardening and fall fertilization. Roots appear to be the main site of N storage, and root N content was significantly affected by pre-hardening and fall fertilization, but not their interaction. A combination of pre-hardening and fall fertilizer at a rate of 100 and 24 mg total N seedling^?1, respectively, yielded seedlings with the largest root systems.     

THE ACTIVE AFFECTS OF SHELTERBELTS ON ENVIRONMENT IN THE SEMIARID REGION OF NORTHEAST CHINA

Since the shelterbelt systems of 1,092,260 hm~2have been established for thirteenyears from 1978,have formed 526,541 networks and protected 13,619,400 hm~2 land in westernpart of Northeast region of China.According to the research work we did in the last five years,the results of research project showed that the shelterbelts had improved the environmentsignificantly.A parameter of comprehensive effects of temperature,moisture and wind in thenetworks(E_c=246.52-12.17E+0.58T+6.58U)which is an active method to estimate the effects ofshelterbelt on farmland,is around 21.1-30.9mm/month improving the moisture state in dryseason,helping the crop yield increasing on the average by 19.8%.The effective accumulatedtemperature(≥10℃)incrcases by 71℃;the cropland area which suffered from wind and frostdamage decreases by 80-90%,the grass coverage on the pastureland and grass production in-creases by 13% and by 49.4-72%,rough protein,rough fat and nitrogen-free extract of grassincrease by 3.34%,2.4% and 8.4%separat     

Root system of Quercus suber L. seedlings in response to herbaceous competition and different watering and fertilisation regimes

Different management practices are commonly applied to increase pasture yield of Mediterranean open woodlands, but the consequences of increasing competition for soil resources with these practices on tree recruitment are still unknown. In a greenhouse study, belowground competition of Quercus suber L. seedlings growing together with natural (Oak_NP) or improved pasture (Oak_IP) was evaluated, and their root systems compared with those of seedlings growing in bare soil (Oak_BS). Two watering levels and two regimes of P₂O₅ fertilisation were also tested. Because of competition, the Oak_IP seedlings had their fine root mass density, coarse root length, and shoot mass reduced by up to 40, 36, and 39%, respectively, when compared to Oak_NP seedlings. Oak_NP and Oak_BS seedlings showed similar average root density parameters and shoot mass values, indicating that Q. suber seedlings growing with natural pasture is a low competitive system. High availability of water and phosphorus did not mitigate the strength of competition between herbaceous plants and oak seedlings, and favoured the pasture to the detriment of the trees. Our findings suggest that P₂O₅ fertilisation and irrigation practices performed to improve herbaceous productivity will negatively influence recruitment of Q. suber seedlings.     

Comparison of container-grown Pinus taeda L. seedlings raised outdoors and in a growth chamber in sunlight

Two annual crops of container-grown loblolly pine (Pinus taeda L.) seedlings raised outdoors differed from those grown inside a covered chamber with a clear top. After a 90-day growth period, outside-grown container seedlings had shorter heights, smaller root collar diameters, and lower root, stem, foliage, shoot, and total dry weights than chamber-grown seedlings. Fall-planted, outside-grown seedlings raised the first year had up to 10% higher field survival than those from the chamber. However, chamber-grown container seedlings that survived retained their initial height and diameter advantages following one complete growing season. Fall-planted seedlings raised the second year showed no differences due to growth treatments when favorable weather for seedling growth occurred after field-planting. Container-grown seedlings raised outdoors during the summer months are well suited for fall-outplanting.     

Formation of tyloses in felled Quercus rubra L.

Summary Tyloses form in red oak (Quercus rubra L.) sapwood in a period of hours if the wood is cut during the active growth season and stored in green condition in the laboratory. If the wood is cut during dormancy and stored in green condition, tyloses form in a period of months. Electron microscopic examination reveals that the wall of a tylosis forms from a promonths. Electron microscopic examination reveals that the wall of a tylosis forms from a protective layer that develops inside the secondary wall of the ray cell in the vessel-ray pit-pair. Protective layers are also present in fiber-parenchyma pit-pairs. Protective layers may exhibit variable thicknesses, with light and dark layers alternating. A young tylosis wall consists of two layers: An electron-dense outer layer and an electron-transparent inner layer. Tyloses walls may attach to each other and form multilamellate tyloses. Sometimes the individual layers of tyloses walls appear lamellated. Because of the type of formation and structure, the tylosis wall in red oak apparently is a primary wall rather than a secondary. Tyloses walls have simple pits. The findings of this study enable felled hardwoods with potential for forming tyloses to be used without the destructive influence of tyloses.     

不同施肥处理对美国红橡木幼苗生长的影响

对红橡木幼苗进行了不同施肥处理试验,结果表明:施肥显著促进红橡木苗高和地径生长.不同处理比较,T4处理(基质拌入1%NPK复合肥)最好,其苗高、地径均较大,分别比对照高39.3%和33.3%,T1(N肥)处理次之,其苗高、地径比对照高28.6%和27.4%.不同施肥处理对红橡木苗高和地径生长的影响效应从大到小的顺序为:...