High performance liquid chromatographic analysis and anticancer potential of Oplopanax horridus: Comparison of stem and berry extracts

Oplopanax horridus or devil's club is a herbal medicine distributed in North America. The constituents and pharmacological activities of O. horridus (OPH) are largely unknown. In this study, we assayed OPH stem and berry extracts using high performance liquid chromatography (HPLC). The anticancer potentials of extracts on different human cancer cell lines (SW-480, HCT-116, HT-29, MCF-7 and NSCLC) were determined by MTS method. The effect of stem extract on cancer cell cycle, expression of cyclin A, and apoptosis were assayed using flow cytometry. HPLC data showed that the composition of OPH stem extract is more complicated than the berry extract. The wavelength of maximum absorption of the major constituent in stem and berry is 196.0 nm and 201.9 nm, respectively. Compared to the berry extract, the stem extract showed significant potent antiproliferative effect on all the studied cell lines. The stem extract at 0.1 mg/ml arrested cancer cells in S- and G2/M-phases, and significantly induced expression of cyclin A. After treatment with 0.1 mg/ml of stem extract for 72 h, apoptotic cells were increased to 45.2%, while control was 9.6%. The cell cycle arrest and induction of apoptosis may play a critical role in cancer chemoprevention by Oplopanax horridus stem extract.     

Protective effect of Piper longum fruit ethanolic extract on radiation induced damages in mice: a preliminary study

The radioprotective property of an ethanolic extract of Piper longum fruits (EEPLF) was investigated in Swiss mice. The white blood cell (WBC) count in irradiated control mice was drastically reduced to 1900 cells/mm3 on third day but in treated animals the count was 2783.3 cells/mm3. The number of bone marrow cells and alpha-esterase positive cells was also enhanced by the EEPLF administration (16.7 x 10(6) cells/femur and 946.5/4000 cells, respectively) when compared to the radiation exposed control animals (12.2 x 10(6) cells/femur and 693.5/4000 cells, respectively). EEPLF reduced the elevated levels of glutathione pyruvate transaminase (GPT), alkaline phosphatase (ALP), and lipid peroxidation (LPO) in liver and serum of radiation treated animals. The extract administration also increased the reduced glutathione (GSH) production to offer the radioprotection.     

盐胁迫对红楠幼苗生长及Na+、K+吸收和分布的影响

In order to explore the salt tolerance mechanism of Machilus thunbergii, the effects of salt stress on seedling biomass, root morphology, sodium and potassium absorption and distribution were studied. The results showed that the above-ground biomass increased slightly under lower salt stress conditions, while the below-ground biomass, root length and root surface area showed a downtrend. The above-ground growth was limited under high concentration salt stress, while the under-ground growth was not subject to significant restrictions. The absorption of Na⁺ in root increased under salt stress, but that of K⁺ decreased. The ability of Na⁺ transporting from root to leaf and stem was weakened. The accumulation of Na⁺ in stem and leaves was less. With the decreased absorption of K⁺, the ratio of Na⁺/K⁺ also continuously increased. With the increased concentration of salt stress, the ability of K⁺ absorption in roots increased. The ability of K⁺ transporting from root to leaf and stem was enhanced, which resulted in significant increase of K⁺ in the leaves and stem. The accumulation of Na⁺ in the under-ground was significantly greater than that in above-ground, while the K⁺ content in above-ground increased significantly, which played a key role in maintaining normal growth and metabolism of M. thunbergii.     

Estrogenic and anti-estrogenic activities of hispolon from Phellinus lonicerinus (Bond.) Bond. et sing

Hispolon was the main antitumor active ingredient in Phellinus sensu lato species. In order to confirm the dual regulating estrogenic ingredient and obtain more effective natural estrogen replacement drugs, hispolon was separated from Phellinus lonicerinus (Bond.) Bond. et sing. Hispolon exhibited significant anti-proliferative effect against estrogen-sensitive ER (+) MCF-7 cells in the absence of estrogen, and exhibits antagonistic effects on 17β-estradiol (E₂)-induced MCF-7 cell proliferation when E₂ and the different concentrations of hispolon were treated simultaneously. Hispolon also inhibited the proliferation of estrogen-negative ER (−) MDA-MB-231 cells at the concentration of 5.00 × 10^− 5 M. The yeast two-hybrid experiments showed that hispolon had strong and non-selective effects on the estrogen receptor (ER) α and ERβ at a concentration of 1.00 × 10^− 6 M. The ERβ-binding ability of hispolon was larger than ERα in the concentration range of 1.00 × 10^− 9 M and 1.00 × 10^− 7 M. Hispolon could increase the body weight coefficient, serum E₂ and progesterone contents in immature female mice at dose of 9.10 × 10^− 6 mol/kg, and increase coefficient of thymus and spleen in mice. The Gscores of hispolon-ERα and hispolon-ERβ docked complexes were − 7.93 kcal/mol and − 7.79 kcal/mol in docking simulations. Hispolon presented dual regulating estrogenic activities, which showed estrogenic agonist activity at low concentration or lack of endogenous estrogen, and the estrogenic antagonistic effect was stimulated at high concentrations or too much endogenous estrogen. Hispolon could be used for treating the estrogen deficiency-related disease with the benefit of non-toxic to normal cells, good antitumor effects and estrogenic activity.     

Cd及矿质营养元素在结缕草植株中的积累特性

以水培方法研究了镉在结缕草中的积累特性及对矿质元素含量的影响。结果表明:Cd²⁺处理下结缕草根、叶中镉的分布比例为细胞壁>胞液>细胞器。低浓度(1、10 mg·L^-1)处理下,结缕草茎细胞液中镉的比例分别较细胞壁中镉的比例高出61.70%、69.60%;高浓度(100 mg·L^-1)处理下,细胞壁中镉的比例较细胞液中镉的比例高出47.70%。低浓度(1、10 mg·L^-1)处理的结缕草地下部的镉含量显著高于地上部,而高浓度下(100 mg·L^-1)结缕草地上部的镉含量较地下部显著提高37.31%;随着处理浓度的升高,镉转运系数显著提高,100 mg·L^-1处理下镉转运系数分别较1、10 mg·L^-1提高了4.12、2.45倍。高浓度(100 mg·L^-1)处理下,结缕草地下部N、K、Ca、Mg含量下降,P、S含量有所提高。高浓度(100 mg·L^-1)镉处理下,地上部N含量较对照显著上升16.11%,Ca、Mg的含量均较对照升高;不同浓度镉处理的地上部P、K、S含量均较对照降低。     

中国思茅松林生态服务功能价值动态研究

对我国思茅松林生态服务功能价值20年来的变化规律进行了研究。1987—2002年期间,思茅松林面积呈下降趋势,思茅松林的生态服务功能价值也相应下降,从365.81×10⁸元·a^-1降至313.50×10⁸元·a^-1,之后随思茅松林资源的恢复而增至328.44×10⁸元·a^-1;思茅松林生态服务功能价值随着资源的增长而增长,随着思茅松林资源的消耗而降低。思茅松林单位面积生态服务     

Echinacoside promotes bone regeneration by increasing OPG/RANKL ratio in MC3T3-E1 cells

Echinacoside (ECH), isolated from Cistanche tubulosa (Schrenk) R. Wight stems, was subjected to in vitro experiments to investigate its bioactivities on proliferation, differentiation and mineralization of the osteoblastic cell line MC3T3-E1. MTT assay, the alkaline phosphatase (ALP) activity and calcium deposition were determined, and the secretion of collagen I (COL I), osteocalcin (OCN), osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) were also assayed by enzyme-linked immunosorbent assay (ELISA). The results showed that ECH caused a significant increase in cell proliferation, ALP activity, COL I contents, OCN levels and an enhancement of mineralization in osteoblasts at the concentration range from 0.01 to 10 nmol·L^− 1 (p < 0.05), suggesting that ECH has a stimulatory effect on osteoblastic bone formation or has potential activity against osteoporosis. In addition, the ratio of OPG/RANKL also could be enhanced by ECH. These findings provide the potent evidence that ECH can promote bone regeneration in cultured osteoblastic MC3T3-E1 cells, which might be done by elevating the OPG/RANKL ratio, and potential evidence for echinacoside to be a promising drug or a lead compound in the development of disease-modifying drug to prevent osteoporosis.     

Pinus contorta growth in northern Sweden as affected by soil scarification

The aim of this study was to quantify the effects of different soil scarification methods on tree growth. Soil scarification influenced stem volume and stem biomass yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in a 17-year-old field trial in boreal Sweden. Soil scarification (disc trenching, mounding and ploughing) resulted in an average stem volume yield of 3.1 and 34.2 m³ ha^–1 on the poor and intermediate sites, respectively, while corresponding values for no soil scarification were 0.9 and 16.7 m³ ha^–1. In comparison to no scarification, ploughing increased volume yields by 500% on the poor site and by 200% on the intermediate sites. The ranking according to stem volume yield was ploughing > disc trenching = mounding no soil scarification. Averaged over the two sites, the mean annual increment of stem biomass was 219% and 145% higher (in d.w., 0.26 kg and 0.34 kg per sample tree) after ploughing compared with no soil scarification, for the average and dominant sample trees, respectively. Although not significant, the increased growth rate after soil scarification decreased the average stem basic wood density of the sample trees with 1.6% and 5.3%, at the poor and intermediate sites, respectively. In conclusion, soil scarification significantly increased the 17-year stem volume yield compared with no scarification. The results also indicate that the difference in stem biomass yield between ploughing and the other methods, especially no soil scarification, will increase even more in the near future.     

Establishment of a high-frequency regeneration system in <Emphasis Type="Italic">Cerasus humilis</Emphasis>, an important economic shrub

Cerasus humilis is a species of small, perennial, drought-resistant and multipurpose deciduous shrub grown in arid and semi-arid conditions in northern China. In this study, an efficient protocol for the rapid micropropagation of C. humilis has been standardized using stem and/or leaf explants. Direct multiple shoot induction was observed when the stem explants were cultured on Murashige and Skoog (MS) medium supplemented with different plant growth regulators. The highest shoot induction was obtained when stem explants from adult trees were cultured on MS medium supplemented with 2.0 mg L^?1 6-benzyladenine (6-BA) and 0.9 mg L^?1 α-naphthaleneacetic acid (NAA). The leaf and stem explants cultured on MS medium with 1.0 mg L^?1 6-BA and 0.6 mg L^?1 NAA, and 0.5 mg L^?1 6-BA and 0.8 mg L^?1 NAA, respectively, produced the highest induction frequency of callus. Maximum proliferation of callus was observed on MS medium containing a combination of 0.5 mg L^?1 6-BA with 0.6 mg L^?1 2,4-dichlorophenoxyacetic acid (2,4-d). Optimal shoots differentiated from callus were obtained on MS medium supplemented with 5.0mg L^?1 6-BA and 0.9 mg L^?1 NAA. In vitro rooting was achieved on half-strength (1/2) MS medium containing 0.5 mg L^?1 NAA. Rooted plantlets were hardened under control conditions and successfully acclimatized under field conditions.     

New lignans from the bioactive fraction of Sambucus williamsii Hance and proliferation activities on osteoblastic-like UMR106 cells

Four new lignans (1, 7–9), together with nine known ones, were isolated from the anti-osteoporosis fraction of the extract of Sambucus williamsii Hance which was eluted by 50% and 95% aqueous ethanol over D101 macroporous resin column. Their structures were elucidated by NMR spectroscopic analyses, and the absolute configurations of all compounds were determined by application of circular dichroism method. All the compounds were reported for the first time from the Sambucus genus and firstly studied for their proliferation effects on osteoblastic-like UMR 106 cell. The data showed that compounds 2–9 significantly promoted cell proliferation in some dose, especially compounds 2, 3, 4, 5, and 7 increased osteoblastic cell numbers by 31.3%, 28.3%, 25.6%, 25.1% and 26.0% at 10^− 10 M, 10^− 10 M, 10^− 7 M, 10^− 10 M and 10^− 10 M, respectively, which suggested that lignans were the components accounting for the bone protective effects of SWH.     

Extract of Magnoliae Flos inhibits ovariectomy-induced osteoporosis by blocking osteoclastogenesis and reducing osteoclast-mediated bone resorption

Bone homeostasis is maintained by a balance between bone resorption by osteoclasts and bone formation by osteoblasts. Osteoporosis occurs when osteoclast activity surpasses osteoblast activity. Pro-inflammatory cytokines stimulate osteoclast differentiation and activity by increasing production of macrophage-colony stimulating factor and receptor activator of nuclear factor-κB ligand (RANKL). In this study, we investigated whether Magnoliae Flos (MF), one of the most commonly used Chinese medicinal herbs for managing rhinitis, sinusitis and headache, could effectively inhibit osteoporosis. In ovariectomized (OVX) mice compared to sham mice, the body weight increased and serum levels of alkaline phosphatase (ALP), tartrate resistant acid phosphatase 5b, calcium, and osteocalcin were significantly elevated. However, orally administrated MF extract substantially inhibited the increased body weight and serum levels of bone turnover markers, without any evidence of tissue toxicity. MF extract treatment significantly reversed the morphometric parameters of ovariectomy-induced bone loss, including trabecular bone volume, thickness, number, separation, and bone density, to almost the same levels of the sham mice. Furthermore, MF extract reduced the RANKL-mediated osteoclast differentiation and bone resorption by inhibiting the activities of matrix metalloproteinases (MMPs) and cathepsin K in mouse bone marrow macrophages. MF extract appeared to increase ALP activity in murine osteoblastic cells. Taken together, MF extract may be a beneficial supplement for the blockade of osteoporosis progression, particularly for the management of postmenopausal osteoporosis.     

Structural characterization and radioprotection of bone marrow hematopoiesis of two novel polysaccharides from the root of Angelica sinensis (Oliv.) Diels

Two novel homogeneous polysaccharides, APS-1a and APS-3a were successfully isolated from the root of Angelica sinensis. APS-1a was composed of galactose, arabinose and glucose in a relatively molar percentage of 57.34%, 27.67% and 14.98%, and had a molecular weight of 49.0 kDa, whereas APS-3a was composed of galactose, arabinose and glucose in a relatively molar percentage of 84.54%, 6.50%, and 8.96%, and had a molecular weight of 65.4 kDa. APS-1a and APS-3a mainly consisted of 1,4-linked galactose, 1,3,6-linked galactose, T-galactose and T-arabinose, and the molar ratio of each linkage was different between APS-1a and APS-3a. The bioactivity analysis showed that APS-1a and APS-3a increased the thymus and spleen index, the number of red blood cell (RBC) and white blood cell (WBC) in peripheral blood and the cellularity of bone marrow cell numbers in irradiated mice, protected mice against radiation-induced micronucleus formation in bone marrow, suggesting that polysaccharides could be used as radioprotective agents, especially for promoting bone marrow hematopoiesis.     

Anti-ulcer potential of Haldinia cordifolia

Haldinia cordifolia stem has been evaluated for its antiulcer potential. Enzyme assay-guided fractionation of the chloroform extract yielded 7-hydroxycoumarin as the active constituent which showed interesting H⁺/K⁺ ATPase inhibitory activity.     

Inhibition of glucose intestinal absorption by kaempferol 3-O-α-rhamnoside purified from Bauhinia megalandra leaves

Glucose intestinal absorption (GIA) is one of the factors that increase glycemia. Its reduction could be an important factor in decreasing hyperglycemia in diabetic patients. It has been shown that the aqueous extract of Bauhinia megalandra leaves inhibits GIA. In the present study we identified a compound present in the extract of B. megalandra responsible for the biological effect. The methanol extract of B. megalandra leaves was fractionated using different solvents, and high-speed counter-current chromatography yielding two pure compounds identified by ¹H NMR and ¹³C NMR as kaempferol 3-O-α-rhamnoside and quercetin 3-O-α-rhamnoside. The first one increased the K_M without changes in the V_MAX of GIA. In addition it exerted an additive inhibitory effect, on GIA, when combined with phlorizin. We suggest that kaempferol 3-O-α-rhamnoside is a competitive inhibitor of intestinal SGLT1 cotransporter.     

Model computations on the critical combination of snow loading and windspeed for snow damage of scots pine,Norway spruce and Birch sp. at stand edge

Model computations were made on the critical combination of snow loading and windspeed for snow damage of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies Karst.) and birch sp. (Betula sp.) at the newly formed stand edge with varying tree height and stem taper using the model developed by H. Peltola, S. Kellomäki and H. Väisänen (1996, HWIND: A Mechanistic Model for Wind and Snow Damage of Scotts Pine, Norway Spruce and Birch sp.) for the mechanism of wind and snow damage. In the computations, the total turning moment arising from the wind and snow load and from the bending of stem and crown was calculated along with the breaking stress of the stem and root anchorage. Windspeed variation within the crown and the vertical distribution of snow, stem and crown weight were also taken into account.According to computations, the critical combination of snow and wind loading for stem breakage and uprooting of trees was caused mainly by accumulation of snow on tree crowns, rather than by wind, which did, however, increase the risk of damage. The risk of damage increased along with stem taper decrease or tree height increase for all tree species studied. However, Scots pine and Norway spruce were found much more susceptible to snow damage than birch, which (being leafless) had much less crown area for snow attachment and wind loading.The trees most likely to suffer stem breakage were slightly tapering Scots pines and Norway spruces with tapers of 1:120 for varying tree heights of 12–20 m under short-term snow loading of 60 kg m⁻², i.e. they would have suffered stem breakage under windspeeds of less than 9 m s⁻¹ above the tree canopy top. Respectively, even Scots pine and Norway spruce with tapers of 1:100 were at risk of stem breakage through sustained snow loading of 60 kg m⁻². In addition, even snow loads of 20–40 kg m⁻² were found big enough to cause stem breakage of these trees with stem tapers of 1:120 during sustained snow loading. Correspondingly, similar pines and spruces with stem tapers of 1:120 were found to even more liable to be uprooted during conditions of unfrozen soil than of having their stem broken by short-term snow loading of 20–60 kg m⁻², i.e. less windspeed was needed to cause uprooting. However, pines and spruces with tapers of 1:80 were not at risk for stem breakage and uprooting. This was because snow would have more probably been dislodged from the tree crowns by windspeeds greater than 9 ms⁻¹ which are needed to worsen the damage. Nor would very slender birch without leaves have suffered stem breakage or uprooting under any circumstances with windspeeds of less than 9 ms⁻¹.     

Bilberry extract protect restraint stress-induced liver damage through attenuating mitochondrial dysfunction

The aim of the present study is to investigate the protective effect of bilberry extract on liver damage in restraint stressed mice. A remarkable increase in alanine aminotransferase (ALT) and reactive oxygen species (ROS) levels was observed in stressed mice. Treatment with bilberry extract restored ALT and ROS to normal levels, and enhanced mitochondrial complex II activity that was lowered in restraint stressed mice. The mitochondrial electron transfer chain (ETC)-related gene expression was measured by RT-PCR, and a significant up-regulation of complex II mRNA was observed for SDHA, B, C and D mRNA in bilberry extract-treated group compared with that in stressed group. Bilberry extract administration also profoundly elevated the Na⁺-K⁺-ATPase activity and mitochondria membrane potential (?Ψ_m), which was reduced in the stressed group. Bilberry extract exhibited protective effect by scavenging free radicals and attenuating mitochondrial dysfunction in the liver of restraint stressed mice. It may be used as a promising therapeutic agent in preventing and delaying the life-related disease.     

Effects of intercropping of peanut with the medicinal plant Atractylodes lancea on soil microecology and peanut yield in subtropical China

Diverse intercropping is an effective way to control crop disease and improve productivity. The aim of this study was to investigate the effects of intercropping peanut (Arachis hypogaea L.) with the medicinal plant Atractylodes lancea on peanut yield and on the microbial community in the soil. A. lancea was intercropped with peanut in an upland that had been monocropped with peanut for 10 years in subtropical China. The results showed that all the intercropping treatments increased the peanut pod yield. Intercropping of peanut with A. lancea effectively reduced the accumulation of soil phenolic allelochemicals and increased soil urease and invertase activities. Compared with addition of fertilizer, the row spacing between peanut and A. lancea was a more important factor influencing the soil microbial community. Analysis of phospholipid fatty acid (PLFA) profiles showed that Gram-negative (G^?) bacteria were significantly affected by changes in the intercropping pattern. Especially in the rhizosphere region, which is nutrient-rich and has diverse substrate composition, the G^? bacterial population increase by 31.2–79.9 % in intercropping treatments. Soil G^? bacteria (as indicated by PLFA, including cy17:0, 18:1ω7, and 16:1ω9) were significantly promoted in the intercropping treatments. The increase in the G^? bacterial population and the decrease of phenolic allelochemicals resulted in the promotion of peanut growth and increased peanut yield in the intercropping treatments. Our results provide details on the mechanisms by which intercropping of peanut with A. lancea can improve the soil environment.     

麻竹枝叶生长对钩梢的响应

为了解冠层生物量积累、分配及枝叶大小对麻竹立竹受营林措施干扰(钩梢)后的响应,对不同竹龄全梢、钩梢麻竹地上构件生物量、生物量比、单叶特征、大小枝生物量分配比例及商品竹叶数量进行了调查.结果表明:麻竹立竹地上现存生物量分配格局为秆＞枝＞叶.叶生物量、叶/枝和叶/秆生物量比为2年生＞3年生＞1年生.随着竹龄的增加,枝、秆生物量、地上生物量和枝/秆生物量比总体上呈增加的趋势.2年生和3年生立竹枝、叶生物量分配比例显著高于1年生立竹,秆生物量分配比例显著小于1年生立竹.此外,随着竹龄的增加,立竹减少了对0 ～8 mm枝生物量的分配,增加了对8～16 mm、16 mm以上枝生物量的投入,以提高空间拓展能力,截获更多光资源.钩梢强烈影响了生物量分配格局,显著减小了麻竹立竹枝、叶、秆、地上生物量.钩梢后麻竹立竹增加了枝、叶生物量分配比例,减少了秆生物量的分配比例,同时提高了单叶叶面积和单叶干质量,增加了8～16 mm、16 mm以上枝生物量分配比例,减小0～8 mm枝生物量分配比例,以权衡枝叶的生长,提高立竹对环境的适合度.钩梢后立竹叶/枝、叶/秆、枝/秆生物量比升高,表明生物量分配更多地向叶和枝倾斜.钩梢麻竹商品竹叶数量较全梢麻竹增加29.68％,且发生部位明显降低,钩梢后冠层下部商品竹叶数量增加79.73％,中部商品竹叶数量增加25.81％,降低了采摘高度.在钩梢后的一个生长季内,钩梢影响了麻竹立竹资源利用策略,表现为枝与叶之间关系的变化,但随钩梢年限的增加其变化规律如何尚需进一步研究.     

Effects of [CO2] and nitrogen on morphological and biomass traits of white birch (Betula papyrifera) seedlings

To investigate the interactive effects of CO₂ concentration ([CO₂]) and nitrogen supply on the growth and biomass of boreal trees, white birch seedlings (Betula papyrifera) were grown under ambient (360 μmol mol⁻¹) and elevated [CO₂] (720 μmol mol⁻¹) with five nitrogen supply regimes (10, 80, 150, 220, and 290 μmol mol⁻¹) in greenhouses. After 90 days of treatment, seedling height, root-collar diameter, biomass of different organs, leaf N concentration, and specific leaf area (SLA) were measured. Significant interactive effects of [CO₂] and N supply were found on height, root-collar diameter, leaf biomass, stem biomass and total biomass, stem mass ratio (SMR), and root mass ratio (RMR), but not on root mass, leaf mass ratio (LMR), leaf to root ratio (LRR), or leaf N concentration. The CO₂ elevation generally increased all the growth and biomass parameters and the increases were generally greater at higher levels of N supply or higher leaf N concentration. However, the CO₂ elevation significantly reduced SLA (13.4%) and mass-based leaf N concentration but did not affect area-based leaf N concentration. Increases in N supply generally increased the growth and biomass parameters, but the relationships were generally curvilinear. Based on a second order polynomial model, the optimal leaf N concentration was 1.33 g m⁻² for height growth under ambient [CO₂] and 1.52 g m⁻² under doubled [CO₂]; 1.48 g m⁻² for diameter under ambient [CO₂] and 1.64 g m⁻² under doubled [CO₂]; 1.29 g m⁻² for stem biomass under ambient [CO₂] and 1.43 g m⁻² under doubled [CO₂]. The general trend is that the optimal leaf N was higher at doubled than ambient [CO₂]. However, [CO₂] did not affect the optimal leaf N for leaf and total biomass. The CO₂ elevation significantly increased RMR and SMR but decreased LMR and LRR. LMR increased and RMR decreased with the increasing N supply. SMR increased with increase N supply up to 80 μmol mol⁻¹ and then leveled off (under elevated [CO₂]) or stated to decline (under ambient [CO₂]) with further increases in N supply. The results suggest that the CO₂ elevation increased biomass accumulation, particularly stem biomass and at higher N supply. The results also suggest that while modest N fertilization will increase seedling growth and biomass accumulation, excessive application of N may not stimulate further growth or even result in growth decline.     

Effects of pruning and stand density on the productionof new epicormic shoots in young stands of pedunculate oak (Quercus robur L.)

Context

Avoidance or control of epicormic shoots is among the major silvicultural challenges for the production of high-quality oak timber. In northern Europe, contemporary oak silviculture aims to produce valuable timber on a relatively short rotation, applying early, heavy thinning combined with artificial pruning.

Aims

The aim of this study was to analyse the effects of pruning and stand density on the production of new epicormic shoots on young trees of pedunculate oak (Quercus robur L.).

Methods

The study was based on two field experiments in even-aged stands of pedunculate oak subjected to different thinning practices and early selection of potential future crop trees. From ages 13 to 15 years, stem density was reduced to 300 trees ha^?1, 1,000 ha^?1 or stands remained unthinned. Pruning was conducted on selected trees at ages 22–24 years. At that age, the stem density in unthinned control plots ranged from 2,500 to 3,100 ha^?1. All treatments were replicated twice within each experiment.

Results

Pruning led to an overall increase in the total production of new epicormic shoots. More epicormic shoots were produced in the lower part of the stem (0–3 m in height) than in the upper part (3–6 m). The number of new epicormic shoots increased with increasing stand density.

Conclusion

Early, heavy thinning combined with high pruning at regular intervals may help shorten the rotation length for pedunculate oak without further reduction in wood quality than that which is caused by wider annual growth rings.