Carbon and phosphorus partitioning in Pinus serotina seedlings growing under hypoxic and low-phosphorus conditions

Ten-week-old pond pine (Pinus serotina Michx.) seedlings were grown in solution culture at 5 or 100 microM P and under aerobic or hypoxic solution conditions. After 6 and 10 weeks in the treatments, changes in relative growth rate (RGR), P acquisition and allocation, and carbohydrate partitioning were determined by analyzing tissue for total P, soluble sugars and starch. Six weeks of low-P growth conditions decreased seedling dry weight and the ratio of shoot dry weight to root dry weight (S/R) by 39 and 51%, respectively, in comparison to seedlings from the aerobic, high-P (control) treatment. Mean RGRs of shoots in the low-P treatment were reduced by 33%, whereas root growth was unaffected. After 10 weeks of low-P growth conditions, however, both shoot and root RGRs were significantly reduced, and plants had lower S/R ratios than in any other treatment. Slowed shoot growth was accompanied by starch and nonstructural carbohydrate accumulation in needles, indicating that needle growth was not limited by carbohydrate supply. Six weeks of low-P growth conditions decreased total seedling P by 75%, reflecting a 97% reduction in the net uptake rate (NUR). Shoot NUR as a fraction of seedling NUR was also greatly reduced in the low-P treatment, indicating that low-P growth conditions affected P translocation to the shoot more than P accumulation by roots. In contrast, 6 weeks of hypoxic growth conditions decreased total dry weight of seedlings in the high-P treatment by 41% relative to their aerobic counterparts. Root growth was affected more than shoot growth, however, and S/R ratios increased. After 10 weeks, S/R ratios doubled, primarily because of the reduction in root RGR. Nevertheless, roots of hypoxic seedlings contained a higher percentage of total seedling P than their aerobic counterparts. Net P acquisition per seedling decreased by more than 50% under hypoxic growth conditions, as a result of reductions in both root RGR and seedling NUR. Starch accumulation in shoots of hypoxic seedlings reflected reductions both in root growth and in transport of carbohydrates to nonwoody roots. Carbohydrate availability did not appear to be limiting growth of hypoxic woody roots, which are well-aerated internally, but it may have limited metabolic processes in nonwoody roots of seedlings from the high-P treatment.     

The effect of seaweed concentrate on the growth of Pinus pinea seedlings

Seedlings of Pinus pinea L. growing in plastic containers were treated with seaweed concentrate (SWC). Different concentrations of SWC were applied, 0 to 3 times, to the roots or shoots of the seedlings. Shoot application increased plant weight mainly by increasing shoot growth. This was manifested as increased shoot length and weight and a decrease in the root/shoot ratio. Root drenches did not change the total plant weight but it accelerated root growth and increased lateral root dry weight. Root growth capacity (RGC) tests for both shoot and root applications indicated an increase in root length and some increases in root number when applied as a root drench. This study indicates that root application of SWC improved seedling quality and increased the ability of seedlings to survive transplanting into pots.Abbreviations GC-MS Gas Chromatography-Mass Spectrometry - RGC root growth capacity - SWC seaweed concentrate     

Field performance of Quercus petraea seedlings grown under competitive conditions: influence of prior undercutting in the seedbed

Quercus petraea was undercut according to the following procedure: undercutting first year once (July, September, November), twice (July and November), or undercutting in two consecutive years (September of year 1 and either July, September or November of year 2). Undercutting decreased height and dry weight of the seedlings compared to uncut control seedlings. Undercutting in September and July in two consecutive years increased the number of first-order lateral roots. Field performance was evaluated by transplanting under two conditions, (a) competition with a mixture of grasses with no irrigation or fertilisation and (b) standard conditions with fertilisation and irrigation first year and no competition with grass. After two growing seasons under competitive conditions, seedlings undercut in September of year 1 had a significantly higher dry weight compared with that of uncut control seedlings. Numbers of lateral roots and field performance under competitive conditions was related when numbers of lateral roots were small, but not when high. Competitive conditions had limited effect on root growth after one growing season, whereas shoot growth was reduced. After two growing seasons both shoot and root growth were reduced in all treatments compared with standard conditions.     

Root-shoot relationships of Fraxinus mandchurica

IntroductionRootsystemsofplantsplaycruciaIrolesinabovegroundgroWth,competitionbetweenthesameordifferentspecies,fluxesofenergyandnutrientscy-cIinginecosystems(Fogel1985,Faheyetal1988,1994).DuringtheevolutionofterrestrialplantstheirrootSandshootsbecameprogressivelyspeciaIizedtoexpIoitdifferentfacetsoftheirenvironments(Russell1979).Shootsentra9solarradiationandthroughphotosynthesis,eIaboratethemetabolitesonwhichallgroWthdepends,rootsanchortheplantinthesoilandabsorbwaterandnutrients.But,histo…     

Shoot and root sensitivity of containerized black spruce,white spruce and jack pine seedlings to late fall freezing

Damage to containerized forest seedlings due to freezing can occur in the fall or early winter in Canadian forest nurseries. The following spring, damage to shoots and impairment of growth is observed. The objectives of this experiment were to measure the impact of late fall low temperatures (0° to --30°C) on whole seedlings of the three most common species used for reforestation in Quebec: black spruce (BS), white spruce (WS) and jack pine (JP). Impacts of freezing temperatures on (i) whole seedling and apical bud mortality, (ii) shoot growth and root mortality, (iii) stem electrical resistance, (iv) shoot and root water relations, (v) concentrations of N, P, K, Ca, Mg, and total sugars in shoots were assessed. JP showed the highest rate of whole seedling mortality while WS showed the highest rate of apical bud mortality. JP was the most severely affected: destruction of the root system at low temperatures as well as a reduction of shoot growth and stem diameter and a decrease (more negative) in shoot and root water potential. WS showed a reduction of shoot growth despite no apparent damage to the root system at low temperatures. BS was not affected by temperatures as low as --30°C. Nutrient and sugar concentrations were not affected by low temperature treatments.     

不同类型薄壳山核桃苗木栽植效果研究

以淮安地区种植园的1年生和泰州地区种植园的2年生‘波尼’薄壳山核桃苗为试材,研究裸根苗、土球苗、无纺布容器苗等3种不同类型薄壳山核桃苗栽植后生长发育的差异。结果表明:3种类型苗木栽植后新梢和根系生长差异较为显著。两处均以无纺布容器苗成活率最高,达到100%;新梢生长量最大,1年生和2年生苗木的生长量分别为110.77 cm和53.44 cm;根系也最为发达。土球苗次之,裸根苗的新梢、根系生长量最小。分析表明,在江苏淮安和泰州这两个地区,无纺布容器苗的成活率、平均新梢生长量、分枝数、总的新梢生长量、主根长度、粗度、侧根数量等均优于土球苗和裸根苗的。此外,3种类型苗木栽植后,2年生苗木的地上、地下部分生长均优于1年生苗木的。     

Root cold tolerance of black spruce seedlings: viability tests in relation to survival and regrowth

Root systems of 6-month-old, cold-hardened, container-grown black spruce seedlings (Picea mariana (Mill.) B.S.P.) were exposed to 0, -5, -10, -15, -20, or -22.5 degrees C. Freezing-induced damage to fine roots, coarse roots and the whole root system was assessed by various viability tests including leakage of electrolytes, leakage of phenolic compounds, water loss, root and shoot water potentials, and live root dry mass. To assess the long-term effects of freezing-induced root damage, seedling survival and regrowth were measured. Leakage of both electrolytes and phenolic compounds differed among fine roots, coarse roots, and whole root systems. In coarse roots and the whole root system, but not in fine roots, leakage of electrolytes, leakage of phenolic compounds, water loss, and root and shoot water potentials were correlated with percentage of live root dry mass which, in turn, was highly correlated with seedling survival and regrowth. Compared with live root dry mass, electrolyte and phenolic leakage, water loss, and root and shoot water potentials were less well correlated with seedling survival and regrowth. Among the viability tests, electrolyte leakage of the whole root system correlated most closely with seedling survival and regrowth. Under freezing conditions that destroyed less than 50% of each seedling's root system, about 70% of the seedlings survived and subsequent growth was little affected, whereas under freezing conditions that destroyed 70% of each seedling's root system, only about 30% of the seedlings survived and subsequent growth was reduced compared with that of undamaged plants.     

Effects of soil temperature on shoot and root growth and nutrient uptake of 5-year-old Norway spruce seedlings

Soil temperature is a main factor limiting root growth in the boreal forest. To simulate the possible soil-warming effect of future climate change, 5-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three simulated growing seasons in controlled environment rooms. The seedlings were acclimated to a soil temperature of 16 degrees C during the first (GS I) and third growing seasons (GS III), but were assigned to random soil-temperature treatments of 9, 13, 18 and 21 degrees C during the second growing season (GS II). In GS II, shoot diameter growth was lowest in the 21 degrees C treatment and root growth was lowest in the 9 degrees C treatment. In GS III, shoot height and root length growth improved in seedlings that had been kept at 9 degrees C during GS II, indicating compensatory growth in response to increased soil temperature. The temporary decrease in soil temperature had no long-lasting significant effect on seedling biomass or total nutrient uptake. At the end of GS III, fine roots of seedlings exposed to a soil temperature of 21 degrees C in GS II were distributed more evenly between the organic and mineral soil layers than roots of seedlings in the other treatments. During GS II and GS III, root growth started earlier than shoot growth, decreased during the rapid shoot elongation phase and increased again as shoot growth decreased.     

Effects of Seedbed Density on One-Year-Old <Emphasis Type="Italic">Fraxinus angustifolia</Emphasis> Seedling Characteristics and Outplanting Performance

To assess the effects of seedling spacing on one-year-old seedling morphology in the nursery, seeds of three provenances of Fraxinus angustifolia were sown at five different seedling spacings within rows of two different spacings in the seedbed. Subsequent growth performance of one-year-old seedlings was assessed by planting in the forest. Within row spacings were: 4.3, 5.0, 6.3, 8.3, and 12.5 cm, and there were five rows at 20 cm apart, or three rows at 33 cm apart across the 1.2 m wide seedbeds. Both spacings within and between rows significantly affected shoot height, root collar diameter, root dry weight and shoot dry weight, but not root/shoot ratio. Wider spacings produced larger seedlings, but only the wider spacing within rows significantly increased fine and coarse root mass. Provenances showed significant differences in diameter, root/shoot ratio, and fine and coarse roots, and they also showed interactions with row spacings in height and diameter measurements. One year after outplanting, diameter growth was significantly related to provenance, and diameter growth was 88% greater for trees from 33 cm nursery row spacing than those from 20 cm nursery row spacing.     

Regrowth and dry matter allocation in Quercus robur (L.) seedlings root pruned prior to transplanting

Two-year seedlings of Quercus robur (pedunculateoak) were root-pruned before transplanting in order toevaluate the importance of coarse versus fine roots onregrowth. Root systems were pruned by leaving c. 19,13 or 7 cm root from the root collar. Alternatively,coarse roots (>2 mm in diameter) were removed, leaving only the taproot and the fine roots (<2 mm)attached, or fine roots were removed from coarse rootsand taproot. Growth of shoots and roots after onegrowing season was compared to an unpruned controlunder standard nursery conditions. Seedlings rootpruned to 19, 13 or 7 cm were further tested undercompetition achieved by transplanting into a mixtureof clover and grass. Pruning of the root systemsignificantly reduced regrowth in terms of total plantDW in accordance with the severity of pruning, shootDW being more affected than root DW. Removal of coarseroots depressed final root DW whereas removal of fineroots reduced shoot DW and hence root:shoot ratioincreased. The study suggests that fine and coarseroots have different roles in root:shoot allocation.The competition test increased root:shoot ratioindicating that competition induced seedlings toallocate more of their resources into growth of theroot system.     

Effects of forest floor planting and stock type on growth and root emergence of Pinus contorta seedlings in a cold northern cutblock

A two-year field trial was conducted to determine the growth response, and root emergence pattern of interior lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings in response to container type and forest floor removal. Seedlings were grown in Styroblocks^TM, Copperblocks^TM, or AirBlocks^TM, and were planted directly into the undisturbed forest floor or into manually prepared planting spots where the forest floor had been scraped away to expose the mineral soil. Seedlings planted into scalped planting spots exhibited marginally but significantly (7%) greater above-ground growth rates (seedling stem volume); whereas seedlings planted into the forest floor produced significantly more (11%) new roots. There were no differences in above- or below-ground biomass. Seedlings grown in Copperblock^TM containers produced a higher proportion of roots near the top of the plug when tested at lifting, however this pattern was not observed in the field. Given that scalping is more costly than forest floor planting, and that the increased shoot growth was relatively small, we recommend that forest floor planting be considered as an alternative to manual spot scalping for sites, such as the site tested here: those with cold, but well-drained soils and where competition from other plants is not a serious problem.     

森林草原过渡带中沙地云杉幼苗在林窗中的环境梯度变化

在我国内蒙古自治区森林草原过渡带中,从林窗内到周围环境进行沙地云杉(Piceamongolica)幼苗的调查以阐明其梯度变化。在沙地森林区,选择了一个形成年龄长达30年的大林窗,从林窗中央向周围森林作2个5m宽的样带,对沙地云杉幼苗动态进行了监测。幼苗距离林窗中心越远,个体越高,数量也越多。在林窗内,有很多幼苗,但是大多数的幼苗在它们长大之前就死亡了。相对于林木高度的动态变化,幼苗的死亡率在样带中的分布基本上有着相似的规律。沿着森林的边缘,幼苗的生长可能由于林窗中边缘光线渗透而得到暂时的提高。文中还讨论了自然森林的更新动态。结果表明在沙地云杉林里林窗干扰带能产生一个非均质的环境促进物种的更新,从而决定了该森林是一个多年龄层次的森林类型。图6参37。     

杜仲育苗试验结果分析

采用切根及喷云大-120 对杜仲苗木生长的效果进行了试验, 结果表明: 切根和喷云大- 120 处理对杜仲苗木的生长作用一般不显著, 在苗高、地径、冠幅等10 个性状中, 切根喷云大- 120 对苗高和主根发育负作用明显, 切根、喷云大-120 及其交互作用对根鲜重负作用明显, 故在杜仲育苗过程中不宜采用切根和喷云大-120 处理。     

Effects of soil temperature on biomass and carbohydrate allocation in Scots pine (Pinus sylvestris) seedlings at the beginning of the growing season

We studied effects of soil temperature on shoot and root extension growth and biomass and carbohydrate allocation in Scots pine (Pinus sylvestris L.) seedlings at the beginning of the growing season. One-year-old Scots pine seedlings were grown for 9 weeks at soil temperatures of 5, 9, 13 and 17 degrees C and an air temperature of 17 degrees C. Date of bud burst, and the elongation of shoots and roots were monitored. Biomass of current and previous season roots, stem and needles was determined at 3-week intervals. Starch, sucrose, glucose, fructose, sorbitol and inositol concentrations were determined in all plant parts except new roots. The timing of both bud burst and the onset of root elongation were unaffected by soil temperature. At Week 9, height growth was reduced and root extension growth was much less at a soil temperature of 5 degrees C than at higher soil temperatures. Total seedling biomass was lowest in the 5 degrees C soil temperature treatment and highest in the 13 degrees C treatment, but there was no statistically significant difference in total biomass between seedlings grown at 13 and 17 degrees C. In response to increasing soil temperature, below-ground biomass increased markedly, resulting in a slightly higher allocation of biomass to below-ground parts. Among treatments, root length was greatest at a soil temperature of 17 degrees C. The sugar content of old roots was unaffected by soil temperature, but the sugar content of new needles increased with increasing soil temperature. The starch content of all seedling parts was lowest in seedlings grown at 17 degrees C. Otherwise, soil temperature had no effect on seedling starch content.     

Response to canopy opening does not act as a filter to Fagus sylvatica and Acer sp. advance regeneration in a mixed temperate forest

? In mixed-species forest stands, large losses in tree species diversity often occur during the regeneration phase. In a former coppice-with-standards, we investigated whether the limiting stage in the recruitment process of advance regeneration is the immediate seedling response to canopy release. Experimental canopy gaps were opened and the survival and growth of advance seedlings (Fagus sylvatica, Acer pseudoplatanus, Acer campestre, Acer platanoides) growing in the gaps or under closed canopy were monitored for three years.

? All species responded positively and rapidly to canopy release. Survival was not affected by gap opening. Diameter increment after gap opening was similar across species, and height increment was greater for Acer platanoides and for Acer pseudoplatanus. Post-release diameter and height growth were mainly determined by pre-release seedling size. Competition from neighbouring seedlings did not affect growth in the three years following canopy opening.

? In the recruitment process of F. sylvatica and Acer sp. advance regeneration, the recovery from canopy release did not appear as a limiting step that would filter against some species. Pre-release size was the main factor accounting for post-release growth and is probably a major determinant of long-term seedling dominance.

     

Root-shoot relationships ofFraxinus mandchurica

In this paper, root-shoot relationships of seedlings of Manchurican ash (Fraxinus mandchurica) in pots is studied in green house. The results show that roots and shoots have the co-ordination of growth and roots and shoots of ash have the same growth dynamics. There are very close relationships between total root mass and total shoot mass, between fine root mass and leaf mass in this experiments. At the end growing season, ash root-shoot mass ratio and fine root-leaf mass ratio are 1.85 and 2.01 respectively. These ratios are difference during growth season. There are larger roots than shoots on seedling stage. Low nitrogen and phosphorus produce higher root-shoot ratio, and high nutrient concentrations decrease the ratios. This project is supported by National Natural Science Foundation of P. R. China (No.39570586) (Responsible Editor: Chai Ruihai)     

Excised shoots of top-pruned red pine seedlings,a source of inoculum of the Diplodia blight pathogen

Diplodia pinea causes shoot blight and collar rot diseases of pines in forest tree nurseries and sporulates on colonized seedling needles and stems. In late summer 2005, pycnidia of D. pinea were observed on shoots that had been excised by top pruning red pine seedlings earlier that summer during the third season of growth. This observation prompted surveys to determine the incidence and abundance of D. pinea conidia on excised shoots. At each of two nurseries, excised shoots were collected from the seedling canopy and adjacent alleyway soil in two subplots in each of five beds (plots). Excised shoots from both nurseries bore pycnidia with conidia of D. pinea. A water washing and filtration technique was used to quantify D. pinea conidia extracted from these shoots. Excised shoots collected from the seedling canopy yielded more D. pinea conidia than shoots collected from adjacent alleyway soil. Collection and removal of excised shoots resulting from top pruning of pine nursery seedlings should be considered as a means of reducing inoculum in areas where D. pinea is present.     

雪灾干扰下林窗对木荷幼苗更新的影响

林窗干扰是维持森林生态系统的重要驱动力之一,对种子萌发、幼苗等自然更新过程、森林物种组成和动态、森林生物多样性的维持具有重要作用。本研究以2008年雪灾干扰后的浙江江郎山木荷林为研究对象,对木荷林窗大小结构、幼苗更新、生长等进行调查研究,结果表明:扩展林窗以50 100 m2的林窗个数最多(占总数的45.45%),各等级林窗中以50 100 m2的林窗占总面积比例最大(占总面积的30.31%)。林窗中木荷幼苗的平均高度和地径较对照林分分别高1.44 cm和0.61 mm,幼树在林窗中的平均高度和地径则比对照林分中分别高45.37 cm和5.00 mm且差异显著;林窗大小对木荷幼苗、幼树的高度和地径生长影响显著,中林窗中幼苗的高度和地径均高于小林窗和大林窗中的幼苗且差异均显著(F=4.893,P=0.007;F=5.203,P=0.004;n=357);幼树的地径在不同大小林窗中差异显著(F=3.569,P=0.037;n=43)。林窗幼苗的更新密度随着林窗面积的增大而增大,在林窗面积达到76 m2时,更新密度达到最大值,而后随着林窗面积的增大下降;中林窗和小林窗中更新苗木以低矮植株(1级、2级)为主,面积100 m2大林窗中,木荷幼苗生长较快。与他人研究的森林天然林窗相比,雪灾干扰后改变了林窗的大小分布结构和面积,50 100 m2的林窗比例较大,一定程度上更利于幼苗更新,具有相对较大的林窗幼苗更新密度;不论林窗大小,林窗内的更新幼苗都比林内多,郁闭度较大的林内或大面积的空地上都不利于更新幼苗的生长。因此,从受灾木荷林窗大小结构、幼苗更新、生长等来看,中林窗是幼苗适宜更新的面积,为木荷灾后恢复与重建提供了科学依据。     

黑果枸杞在格尔木地区不同土壤中造林试验

采用三种苗木（容器苗、移植苗和裸根苗）在格尔木地区三种不同的土壤类型（农耕地、撂荒地和稀疏林地）中进行了栽植试验,结果表明,苗高、地径和冠幅的增长量与土壤类型、苗木类型之间具有明显的关联性,相关系数为R（苗高）=0.910（R2=0.828）、R（地径年增长量）=0.903（R2=0.815）和R（冠幅年增长量）=0.909（R2=0.736）;苗高、地径和冠幅的增长量依土壤类型从大到小的排序为：农耕地〉撂荒地〉稀疏林地;依苗木类型从在到小的排序为：容器苗〉移植苗〉裸根苗;在格尔木地区土壤条件较差的撂荒地和稀疏林地,采用容器苗和移植苗栽植黑果枸杞,采用容器苗和移植苗可使造林成活率提高19.4～36.6个百分点,且苗木生长良好,可有效提高土地利用率。     

Stomatal conductance,growth and root signaling in Betula pendula seedlings subjected to partial soil drying

Seedlings of Betula pendula Roth were grown with their root systems separated between two soil compartments. Four treatments were imposed: (i) adequate irrigation in both compartments (WW, controls); (ii) adequate irrigation in one compartment and drought in the other compartment (WD); (iii) drought in both compartments (DD); and (iv) half of the root system severed and the remainder kept well-watered (root excision, RE). Predawn leaf water potential, stomatal conductance, soil-to-leaf specific hydraulic conductance, and root and leaf growth decreased in DD-treated seedlings, which also displayed severe leaf shedding (30% loss in leaf area). The DD treatment also resulted in increased concentrations of abscisic acid (ABA) and its glucose ester in the xylem sap of roots and shoots compared to concentrations in control seedlings (about 200 versus 20 nM). Despite the difference in xylem sap concentrations, total ABA flux to the shoots was similar in the two treatments (1-2 pmol ABA m(-2) leaf area s(-1)) as a result of reduced transpiration in the DD-treated seedlings. Compared with root growth in control plants, root growth increased in the RE-treated plants and decreased in the drying compartment of the WD treatment; however, the RE and WD treatments only slightly reduced leaf expansion, and had no detectable effects on shoot water relations or ABA concentrations of the root and shoot xylem sap. We conclude that short-term soil water depletion affecting only 50% of the root system does not cause a measurable stress response in birch shoots, despite root growth cessation in the fraction of drying soil.