氮磷钾配比施肥对桢楠幼苗生长及生物量积累的影响

采用3因素3水平正交试验设计,研究了N、P、K3种大量元素配方施肥对1a桢楠幼苗生长和生物量积累的影响,为桢楠苗期的科学施肥提供参考.结果表明,不同施肥处理对桢楠幼苗苗高、地径和各器官生物量的影响差异均显著,其中N2P3K1组合(尿素2 g·株-1、过磷酸钙8 g·株-1,氯化钾0 g·株-1)条件下植株苗高、地径及各器官生物量均处于最高水平,该组合植株生长表现最佳.N、P、K对桢楠幼苗生长和生物量积累的影响效应不同,主次顺序均表现为N>P>K,其中N元素影响最大,P元素和K元素影响较小.     

Fall lifting and long-term freezer storage of ponderosa pine seedlings: effects on post-storage leaf water potential, stomatal conductance, and root growth potential

Post-storage water relations, stomatal conductance, and root growth potential were examined in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings from high- and low-elevation seed sources that had been lifted either in October or November and freezer stored, or in March, and then grown hydroponically in a greenhouse for 31 days. Seedlings lifted in October had poor root initiation (< 17 new roots per seedling), low predawn leaf water potentials (< -1.5 MPa), and low stomatal conductance (7.10 mmol m(-2) s(-1)) compared with seedlings lifted in November or March. There was little difference in post-storage water relations and stomatal conductance between seedlings lifted in November and those lifted in March. Throughout the 31-day test, seedlings from the high-elevation seed source produced 3-9 times more new roots, had higher predawn leaf water potentials (-0.6 to -0.7 MPa versus -1.1 to -1.6 MPa), and 1.3-5 times greater stomatal conductance than seedlings from the low-elevation seed source. For all seedlings on Day 31, the number of new roots was significantly related to predawn leaf water potential (r(2) = 0.65) and stomatal conductance (r(2) = 0.82). Similarly, the dry weight of new roots per seedling on Day 31 accounted for a significant amount of the variation in predawn leaf water potential (r(2) = 0.81) and stomatal conductance (r(2) = 0.49).     

氮磷钾配比施肥对油茶花芽生长及分化的影响

为给油茶高效栽培提供参考,选择8年生‘长林53号’油茶作为研究对象,按照3因素3水平L9(34)正交试验设计进行施肥试验,筛选最适油茶花芽分化及生长的施肥配比。施加的氮磷钾肥分别为尿素、钙镁磷肥、硫酸钾肥,其有效成分分别为有效氮(质量分数≥46.4%)、P2O5(质量分数≥12%)、K2O(质量分数≥51%)。结果表明:施加氮肥能显著促进花芽伸长,提高花芽分化率的最佳氮磷钾施肥量为N218.23g/株、P71.00g/株、K242.48g/株;在花芽生理分化期(前分化期),施肥处理显著提高了花芽中ABA和ZR含量,ABA和ZR含量与花芽分化率显著正相关;在花芽形态分化期,施肥处理下ABA含量呈现下降趋势,ZR、IAA和GA3含量呈现增加趋势,氮、磷、钾与多数形态分化期内源激素含量呈显著相关。施肥能促进花芽生长,并且通过影响花芽中内源激素含量来影响花芽分化。     

The effect of cork removal on the radial growth and phenology of young cork oak trees

The effect of the removal of cork was studied in 11-years old cork oak trees (Quercus suber L.), growing in favorable conditions, in relation to phenology and radial growth during two years. Longevity of leaves was 14–15 months (1996, 1998) and 10 months (1997). Bud burst started in mid-February and leaf flushing in April, extending until June. Neither a distinct two-period flushing nor an autumn bud burst or leaf flushing were observed. Radial growth started in mid-April and continued until the end of November, with the maximum growth in June and July. In trees with the removal of cork, leaf abscission occurred a little earlier and new branches had on average 23% fewer new leaves. The radial growth of the trees and its general seasonal pattern were not affected by cork removal in the year of removal or in the year after. The only observation was a shift of the maximum radial growth rate from June to July for the trees where cork had been removed.     

Effects of oak root pruning in forest nurseries on potential pathogen infections

Despite the general practice of root pruning, little is known about the potential impact of reducing shoot/root systems of oak seedlings in this way on their future susceptibility to pathogens, for example Cylindrocarpon spp., Fusarium spp., Ilyonectria spp., Pythium spp. Phytophthora spp. or Rhizoctonia spp. In this study, root‐pruned and non‐pruned seedlings of Quercus robur grown under controlled conditions were inoculated with aggressive and less‐aggressive pathogens. Results indicated, in contrast to our initial assumption, that pathogens significantly reduced lateral root biomass more in non‐pruned seedlings, the extent of the response depending on the pathogens species. In response to pathogen pressure, pruned seedlings tended to attain a higher dry stem mass fraction, but lower dry leaf mass fraction. Pathogens also suppressed leaf mass in total root dry mass fraction (dry leaf mass/total root dry mass ratio, in g × g^?1) more in pruned than in non‐pruned seedlings. These results suggest differences in growth between non‐pruned and pruned seedlings in response to pathogen stress. In nurseries, root pruning of oak trees may enhance the reduction in leaf mass in lateral roots mass fraction resulting from pathogen infections, which may decrease seedling quality. It is therefore important to ensure a low level of inoculum of soil‐borne pathogens to minimize the risk of seedling infection.     

施N肥对会同杉木人工林N、P含量的影响

以湖南会同杉木基地Ⅱ号集水区杉木人工林为研究对象,对其进行施N肥实验,并进行一年期采样,测定不同施肥处理下N肥对杉木林N、P含量的影响及杉木器官与土壤N、P含量之间的相关关系。结果表明:施肥能够提高杉木土壤、细根、叶片的N和P含量,其中施N肥25 g/m~2能提高土壤的N、P含量,施N肥25g/m~2比施N肥5 g/m~2和15 g/m~2更能提高土壤中细根的N、P含量,施N肥5 g/m~2比施N肥15 g/m~2和25 g/m~2对提高叶片中的N含量的效果好,施N肥并未提高凋落物N含量。会同杉木人工林氮磷含量的增加说明施肥能够促进杉木林的生长。     

杉木根、枝和叶的C、N、P生态化学计量特征

以湖南会同杉木基地Ⅲ号集水区25年生杉木人工林为研究对象,测定1月份杉木根、枝和叶的C、N、P含量,研究其C、N、P生态化学计量特征。结果表明:杉木根、枝和叶中C含量平均值分别为561.04、515.93、513.56 g/kg,表现为根枝叶;N含量平均值分别为6.86、8.78、7.97 g/kg,表现为枝叶根;P含量平均值分别为1.45、0.71、1.54 g/kg,表现为叶根枝。根的C∶N、C∶P、N∶P的平均值分别为92.50、521.72、5.29;枝的C∶N、C∶P、N∶P的平均值分别为65.17、789.82、12.46;叶的C∶N、C∶P、N∶P的平均值分别为69.31、355.56、5.53。叶的C含量和枝的呈显著正相关;叶的N含量和枝的呈极显著正相关;叶的N含量和根的呈极显著正相关;P的含量在根、枝和叶之间均呈显著正相关。     

Stomatal conductance, growth and root signaling in young oak seedlings subjected to partial soil drying

Leaf conductance, water relations, growth, and abscisic acid (ABA) concentrations in xylem sap, root apices and leaves were assessed in oak seedlings (Quercus robur L.) grown with a root system divided between two compartments and subjected to one of four treatments: (a) well watered, WW; (b) half of root system exposed to soil drying and half kept well watered, WD; (c) whole root system exposed to drought, DD; and (d) half of root system severed, RE. Sharp decreases in plant stomatal conductance, leaf water potential, hydraulic conductance and leaf growth were observed during DD treatment. No significant differences in plant leaf water potential and stomatal conductance were detected between the WW and WD treatments. Nevertheless, the WD treatment resulted in inhibition of leaf expansion and stimulation of root elongation only in the well-watered compartment. Abscisic acid concentrations did not change in leaves, root tips, or xylem sap of WD- compared to WW-treated plants. Increased concentrations of ABA were observed in xylem sap from DD-treated plant roots, but the total flux of ABA to shoots was reduced compared to that in WW-treated plants, because of decreases in transpiration flux. Similar plant responses to the WD and RE treatments indicate that the responses observed in the WD-treated plants were probably not triggered by a positive signal originating from drying roots.     

Nitrogen loading of Eucalyptus globulus seedlings: nutritional dynamics and influence on morphology and root growth potential

New Forests - Achieving successful outplanting of trees on increasingly harsher sites is a global concern. In Chile, for example, new Eucalyptus globulus plantations are being targeted to poorer,...     

Effects of pre- and post-planting shading on growth of container Norway spruce seedlings

Norway spruce (Picea abies (L.) Karst.) is shade-tolerant and sensitive to high irradiance, summer frosts and winter desiccation, which can impair its reforestation success. In this study, artificial pre- and post-planting shading was examined to determine their effects on post-planting shoot and root growth as well as the vigor of one- and two-year-old Norway spruce seedlings. Three planting experiments were carried out on open nursery fields (Exp. 1, 2) and on a mounded forest clearcut in central Finland (Exp. 3). Before planting, the seedlings were stored over winter either in a freezer or on open fields under snow cover. For two weeks prior to planting, half of the seedlings were placed in the open and the other half under a horizontal shade netting (light transmittance 56 %) (Exp. 1, 2). All seedlings were planted with or without a vertical post-planting shade, which was located on the southern side. Post-planting shading enhanced shoot growth and reduced damage (better visual vigor and needle color and less pine-weevil damage) on Norway spruce seedlings for at least two years after planting (Exp. 2, 3). Those seedlings, that had been stored over winter in the open and kept in shade prior to planting seemed to benefit most from post-planting shading (Exp. 2). However, post-planting shading may give variable results, depending on the seedling quality and weather conditions after planting, and may even reduce shoot growth if no pre-planting shading is used (Exp. 1). Shoot growth may also be improved at the expense of root growth (Exp. 3). The costs of manufacturing and installing post-planting shades may limit their use in practice, for example, to selected regeneration sites where there is high risk of frost damage but where no alternative silvicultural procedure (shelterwood or nurse crop) has been used.     

Fine root dynamics of oak saplings in response to Phytophthora cinnamomi infection under different temperatures and durations

The belowground effects of Phytophthora cinnamomi on 1‐year‐old saplings of two common oak species in mid‐Atlantic US forests, white (Quercus alba) and red oak (Q. rubra), were examined after incubation in pathogen‐infested soilless potting mix. Fine root lengths (0–1.5 mm in diameter) of both oak species were quantified after incubation at successive 30‐day intervals up to 300 days, for a total of 10 incubation periods. In addition, colony‐forming units (CFU) of P. cinnamomi were quantified after white oak saplings were incubated in infested soilless potting mix at different temperature/duration combinations that reflect soil conditions present in the mid‐Atlantic United States. Impact of P. cinnamomi on fine root lengths of red and white oak saplings varied considerably over time. Significant periods of fine root loss occurred primarily during spring, when bud break and leaf flush began for both oak species. Red oaks had 17% fine root loss on average, while white oaks appeared more resistant to P. cinnamomi infection with a 2% decrease in fine roots over the course of the experiment. Phytophthora cinnamomi CFU declined significantly with exposure to all incubation temperatures except 8°C. This was in contrast to in vitro experiments, where the optimum temperature for mycelial growth was determined to be 21°C and above. Significant fine root loss caused by P. cinnamomi depended on plant phenology and the oak species tested. Extreme soil temperatures have a significant adverse impact on temporal changes of P. cinnamomi population.     

Chlorophyll fluorescence,root growth potential,and stomatal conductance as estimates of field performance potential in conifer seedlings

After cold storage, conifer seedlings in British Columbia are tested for field growth potential before planting. We compared three tests of performance potential using container-grown seedlings of Douglas-fir, interior spruce, lodgepole pine, and western larch (14 seedlots total). On several autumn dates, seedlings were lifted and stored at −2°C. The following spring we tested stored seedlings for root growth potential (RGP), chlorophyll fluorescence (CF), and stomatal conductance (Gs), and then planted seedlings in nursery beds. We assessed survival and shoot dry weight (SDW) after one growing season. Performance test results were significantly correlated with each other (r ≥ 0.47) but showed different relationships with field performance, which varied with lift date. The best performance predictor was the sum of CF and RGP (R ² = 0.79 for 78 seedlot by lift-date combinations), which minimized the risk of planting poor seedlings and not planting good seedlings. A sum of 83 for CF (Fv/Fm %) and RGP (new roots >1 cm) provided a threshold above which survival and growth were good. For evergreen conifers, Gs was a good performance predictor, but required extra time to measure leaf area. We recommend a combination of CF and RGP to assess vigor of shoot and root systems before planting. Wolfgang D. Binder––Scientist Emeritus.     

Delayed soil thawing affects root and shoot functioning and growth in Scots pine

In boreal regions, soil can remain frozen after the start of the growing season. We compared relationships between root characteristics and water relations in Scots pine (Pinus sylvestris L.) saplings subjected to soil frost treatments before and during the first week of the growing period in a controlled environment experiment. Delayed soil thawing delayed the onset of sap flow or totally blocked it if soil thawing lagged the start of the growing period by 7 days. This effect was reflected in the electrical impedance of needles and trunks and in the relative electrolyte leakage of needles. Prolonged soil frost reduced or completely inhibited root growth. In unfrozen soil, limited trunk sap flow was observed despite unfavorable aboveground growing conditions (low temperature, low irradiance, short photoperiod). Following the earliest soil thaw, sap flow varied during the growing season, depending on light and temperature conditions, phenological stage of the plant and the amount of live needles in the canopy. The results suggest that delayed soil thawing can reduce tree growth, and if prolonged, it can be lethal.     

Dynamics of fine root N, P and K in high elevation forests of central Himalaya

Fine root nutrient dynamics were calculated for one year in three high elevation forests of Indian central Himalaya.In all sites,fine root nutrient concentrations varied with respect to forests and sea...     

The dependance of root growth potential on light level,photosynthetic rate,and root starch content in jack pine seedlings

Number of new roots (root growth potential or RGP), new root length, photosynthesis, total nonstructural carbohydrate content of needles and roots, terminal bud condition, and shoot elongation were measured on jack pine container seedlings for 4 weeks at weekly intervals under greenhouse conditions of 100%, 20%, and 10% sunlight to simulate competition-induced, lower light levels in the field. Both lower light levels significantly reduced photosynthetic rate, RGP, new root length, total nonstructural carbohydrate (especially starch) content of needles and roots, speed of terminal bud flush, and shoot growth. Both light level and photosynthetic rate were positively correlated with RGP and new root length, indicating that jack pine seedlings may use current photosynthate as an energy source to support new root growth. RGP and new root length were also both negatively correlated with root starch content suggesting that jack pine seedlings may also use stored carbohydrates as a potential carbon source for root initiation and initial root growth.     

Relationships between frost hardiness,root growth potential,and photosynthesis of nursery-grown white spruce seedlings

• Context  

Root growth is a characteristic to which nursery personnel is particularly attentive. The increase in root growth of white spruce seedlings in the autumn relies on the current season’s photosynthates. Needle hardening or a decrease in the mass of photosynthetically active foliage as a result of early frost may negatively affect the seedling’s photosynthetic capacity and its ability to fuel root growth.     

Effect of wood chip application on root growth of oak seedling and weed control in northern Iran

It was hypothesized that wood chips can serve as a mulch to improve the growth of young trees by facilitating the development of their root systems, inhibiting weed germination, and suppressing weed growth. The present study was carried out in Ghorogh Nursery, Golestan Northern Iran, in order to investigate the impact of wood chips application on root growth of oak (Quercus castaneifolia) seedlings and control of weed. A three centimeter wood chip layer was used on the soil surface as the mulch treatment with bare soil as the control. The number of new roots, the length of exciting roots and the density of weeds were measured after 5 and 12 weeks. Results showed that wood chip application had significant positive effect on the length of excising roots after 5 and 12 weeks compared with control seedlings. Also, weeds were reduced to near zero levels in treated plot. Our findings suggested that wood chip layer on the soil surface in the nursery can conserve soil moisture and prevent nutrient leaching from the rooting zone as well as diminish weed growth which consequently lead to production of high quality seedling.     

Effects of feathermoss removal, thinning and fertilization on lodgepole pine growth, soil microclimate and stand nitrogen dynamics

The influence of a continuous feathermoss layer (dominated by Pleurozium schreberi) on soil temperature, soil water potential and tree growth was assessed in a 5-year study. The feathermoss layer was manually removed from 900 m² plots in lodgepole pine (Pinus contorta) stands of northwestern Alberta. The interception and retention of nutrients by moss was estimated in N fertilization treatments with and without moss removal. As well, the potential for intraspecific competition to affect nutrient dynamics was assessed through a thinning treatment. Removal of the moss layer increased soil temperatures in summer and increased the period when soil was frost free, but the plots without moss had soil temperature as low as −13 °C in one winter period with little snow cover. Moss removal did not significantly affect N concentrations of the tree foliage but did reduce needle weight. Thinning had little effect on the rate of diameter growth after the first 3 years, but produced a significant increase in growth by year 4. Fertilization had a consistently positive effect on radial stem increments and N content of foliage, regardless of the presence of moss on the plot. Overall, the intraspecific competition between trees was apparently greater than interspecific competition between moss and trees.     

Relationships among cold hardiness, root growth potential and bud dormancy in three conifers

Greenhouse-cultured, container-grown ponderosa pine (Pinus ponderosa var. scopulorum Engelm.), interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and Engelmann spruce (Picea engelmannii (Parry) Engelm.) were cold acclimated and deacclimated in growth chambers over 19 weeks. Stem cold hardiness, total new root length at 14 days and days to bud break were measured weekly. Relationships among cold hardiness, root growth potential (RGP) and bud dormancy suggest that cold hardiness, which can be measured quickly, could provide a useful basis for estimating the two other parameters. During cold acclimation, there was a lag period in which stem cold hardiness remained at -15 degrees C and RGP was at a minimum, in all three species. Douglas-fir and Engelmann spruce buds remained fully dormant during this lag period. Ponderosa pine buds had no chilling requirement for the loss of dormancy, and reached quiescence during the lag period. Immediately following the lag period, as stem cold hardiness progressed to -22 degrees C, RGP increased to a high plateau in all three species, and Douglas-fir and Engelmann spruce buds approached quiescence. Cold deacclimation and bud development began immediately on exposure to warm, long days, but RGP remained high until stem cold hardiness returned to approximately -15 degrees C. At bud break, cold hardiness and RGP were at the minimum.