Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Nutrient loading of forest tree seedlings to promote stress resistance and field performance: a Mediterranean perspective

The planting environment of Mediterranean areas is highly challenging as summer drought and winter frost jeopardize survival, and soil infertility limits establishment success. We review the potential for seedling nutrient loading to alleviate these post-planting stresses. A growing body of evidence indicates that nitrogen (N) rich seedlings have improved field performance in Mediterranean environments, due to their ability to grow new roots rapidly and out-compete weeds. In addition, frost resistance during hardening is crucial for relatively cold inland nurseries; recent research shows a positive relationship between N and shoot frost resistance though a knowledge gap exists regarding the influence of nutrition on root frost resistance. Some new evidence also implicates phosphorus as an important driver of seedling response in the Mediterranean due to its influence on root growth and physiology. Nutrient status influences other functional attributes critical to survival in Mediterranean areas, such as drought tolerance, root hydraulic conductivity, and mycorrhization. In light of the apparent benefits of high nutrient reserves for seedling performance in Mediterranean areas, we also review techniques for nursery nutrient loading. Exponential fertilization can be applied when species’ growth patterns match this application regime. However, many Mediterranean species exhibit episodic growth indicating that constant or fall fertilization could be more effective in reaching loading. In particular, late-season fertilization has shown good potential to avert nutrient dilution in the fall and increase frost resistance. Several needs for future research are identified, with special emphasis on the necessity to match fertilization regimes to species ecological traits and planting conditions.     

Autumn Fertilization in the Nursery Affects Growth of Picea abies Container Seedlings After Transplanting

Second-year Norway spruce seedlings [Picea abies (L.) Karst.] grown in containers were divided into three fertilization levels in August [5, 15 and 25 mg nitrogen (N) seedling^?1]. The resulting foliar concentrations of N were 11.0, 13.1 and 15.8 g kg^?1, respectively. Seedling height (mean 26.0 cm) did not differ among treatments. The next spring, the seedlings were tested in two experiments. (1) The seedlings were transplanted into pots containing sandy soil in the greenhouse, where they were fertilized with either pure water or nutrient solution (22 mg N l^?1). (2) The outplanting performance of the autumn-fertilized seedlings was tested on a sandy field. In the greenhouse experiment, the autumn fertilization level affected height growth and root egress of the seedlings significantly, but less than fertilization with a nutrient solution after planting. In the field experiment, during the first season after transplanting shoot growth of the seedlings increased with the level of autumn fertilization. After the second and third seasons, the seedling stem volume was highest with the highest level of autumn fertilization. These results suggest that, by improving the preplanting nutrient status of seedlings, the growth of shoot, stem diameter and root biomass can be enhanced after planting, especially on nutrient-poor soils. However, heavier autumn fertilization than that used here may yield a greater and more persistent increment in growth.     

Characterizing the frost sensitivity of black spruce photosynthesis during cold acclimation

We used photosynthetic light response curves to measure and model the responses of two provenances of 3-year-old black spruce (Picea mariana (Mill.) BSP) seedlings to severe artificial frost treatments applied at 2-week intervals during cold acclimation. Black spruce seedlings responded to cold acclimation with long-term suppression of photosynthetic capacity (Amax) and apparent quantum-use efficiency (alpha'). Short-term reductions in both photosynthetic parameters following frost treatments were dependent on the extent of cold acclimation of the seedlings and the severity of the frost treatments. Large reductions in Amax in response to the frost treatments were observed in seedlings that had undergone little cold acclimation and these reductions were associated with an irreversible reduction in alpha'. Such seedlings recovered only partially during the subsequent 23 days, whereas seedlings in most other treatments showed complete recovery of Amax after 13 days. The impact of frost treatments on Amax and alpha' did not vary with seedling provenance. We propose an algorithm that predicts the combined effects of cold acclimation and severe freezing temperatures on the extent of the suppression of A(max) during autumn. The algorithm is based on (1) the maximum Amax observed during the growing season, (2) the accumulation of cold degree-days, based on a minimum nocturnal temperature < 5 degrees C, and (3) the severity of freezing temperatures during autumn. The parameters developed in the algorithm showed that cold acclimation of black spruce seedlings had a greater impact on the reduction of Amax in autumn than did the severe frost treatments. Mean Amax of seedlings subjected to artificial frosts showed a strong correlation with values predicted by the algorithm (r2 = 0.91).     

The effect of late summer fertilization on the frost hardening of second-year Scots pine seedlings

In this study the effect of summer fertilization on the initiation of frost hardening of containerized second-year Scots pine (Pinus sylvestris L.) seedlings is studied. During the second growing season three different fertilization programs (water soluble NPK with micronutrients) determined by electrical conductivity of peat water extract (0.2, 0.5 and 1.2 mS cm^-1) were initiated. The growth and nutrient concentrations of needles were monitored during the fertilization period. The frost hardiness of seedlings was assessed on four separate occasions at two week intervals from August 7 to September 18. This assessment was based on artificial freezing tests and visual damage scoring of tissue browning on current-year needles. Clear differences in foliar N, P and K concentrations were observed between the fertilization treatments. Fertilization prolonged the growing period of needles and increased root collar diameter. In all the tests, the highest fertilization level resulted in the highest level of frost hardiness. The difference between the fertilization treatments ranged from 1 °C to 2.2 °C. Frost hardiness increased with an increase in foliar nitrogen concentration and slightly less consistently with increases in foliar phosphorus and potassium concentrations.     

Weed control increases nitrogen retranslocation and growth of white spruce seedlings on a reclaimed oil sands soil

Early establishment of seedlings in reclaimed oil sand areas is often limited by low nutrient and water availability due to factors such as strong understory vegetation competition. Management practices such as nursery fertilization and field weed control could help early establishment of planted seedlings and reclamation success. We investigated the effect of nursery nutrient loading and field weed control on the growth, nitrogen (N) retranslocation within seedling components, and plant N uptake from the soil for white spruce (Picea glauca [Moench] Voss) seedlings planted on a highly competitive reclaimed oil sands site for two years. Exponential fertilization during nursery production increased the root biomass but not the nutrient reserve in the seedling. In the field experiment, on average across the treatments, 78 and 49% of the total N demand of new tissue growth in the first and second year were met by N retranslocation, respectively. Though exponential fertilization did not affect N retranslocation, it increased the percent height and root collar diameter growth. Weed control increased not only the growth of seedlings by increasing soil N availability, but also N retranslocation within the seedlings in the second year after outplanting. We conclude that vegetation management by weed control is feasible in improving the early growth of white spruce seedlings planted on reclaimed soils and facilitate tree establishment in the oil sands region. Optimization of the nursery exponential N fertilization regime for white spruce may further help with early revegetation of reclaimed oil sands sites.     

Fast, nondestructive measurement of frost hardiness in conifer seedlings by VIS+NIR spectroscopy

Frost hardiness development from mid-August to mid-November was evaluated in seedlings of three provenances of Norway spruce (Picea abies (L.) Karst.) and three provenances of Scots pine (Pinus sylvestris L.) raised at nurseries in north, central and south Sweden. Measurements of the visible + near infrared (VIS+NIR) spectra of shoots were made simultaneously with estimates of frost hardiness based on electrolyte leakage following artificial freezing. Nine physiological variables known to influence frost hardiness were measured throughout the experiment. Multivariate analysis showed that VIS+NIR spectra explained 69% and 72% of the variation in frost hardiness in Scots pine and Norway spruce, respectively. Stem lignification, dry weight fraction, and starch, glucose, fructose, galactose, sucrose, raffinose and stachyose concentrations together explained 80% and 85% of the variation in frost hardiness in Scots pine and Norway spruce, respectively when used as independent X variables in a partial least squares model. These physiological variables could be related to varying degrees with variation in the VIS+NIR spectra. We conclude that VIS+NIR spectroscopy provides a rapid nondestructive technique for measuring frost hardiness in conifer seedlings based on causal relationships between the spectra and the physiology of seedling frost hardiness.     

Assessing the effect of late-season fertilization on Holm oak plant quality: insights from morpho–nutritional characterizations and water relations parameters

Forest restoration projects with Holm oak (Quercus ilex) have had limited success, mostly due to water stress after planting and poor plant quality. Recent studies indicated that large and nutrient rich plants perform better in Mediterranean areas, suggesting that late-season fertilization may improve plant quality and field performance. The purpose of this study was to assess the effect of late-season fertilization on the quality of Holm oak seedlings, as determined by morphological, nutritional, and water relations analyses. We grew Holm oak nursery seedlings under 5 different late-season fertilization regimes and then analyzed morphological characteristics, nutritional status, and water relations parameters of the fertilization groups at the end of the nursery period. We also analyzed the effect of fertilization on nutritional status by use of vector nomograms. Our results indicated that late-season NPK fertilization improved shoot and root growth, and the overall nutritional status of seedlings. The lack of late-season fertilization leads to nutrient deficiency in plants, whilst the application of imbalanced fertilization treatments may trigger nutrient luxury consumption and nutrient dilution, pointing out the importance of NPK proportions in the fertilizer. Moreover, late-season fertilization with nitrogen might improve the drought resistance of seedling by enhancing their osmotic adjustment.     

Frost damage to planted Norway spruce seedlings — influence of site preparation and seedling type

Damage to Norway spruce (Picea abies (L.) Karst.) seedlings by summer frost was monitored on 10 clear-cuttings of various ages to which slash removal and four types of site preparation had been applied. The clear-cuttings were established on two sites (5 on each) in southern Sweden from 1989 through 1993 and planted each year from the year of cutting until 1993. In total, 7680 seedlings were analysed for frost injuries during the first three years following planting. The site preparation methods evaluated were: application of herbicide to ground vegetation; mowing of ground vegetation; scarification (mounding); and control. Two seedling types, bare-rooted and containerised seedlings, were evaluated.Periods of frost susceptibility were calculated using data on bud and shoot development during 1997 together with weather data for each of the studied years and sites. The date of flushing was well correlated to the air temperature sum (+5°C threshold value) in spring. Frost damage varied considerably between sites and study years. The lowest measured minimum air temperature and the frost-day sum during the frost-susceptible period were correlated to the frequency of frost damage. Soil scarification reduced frost damage in the first growing season. Bare-rooted seedlings had a considerably lower frequency of frost injury compared with containerised ones, possibly because flushing of the former was delayed. There was no statistically significant effect of herbicide application, mowing or slash removal on the frequency of frost damage. Seedling growth was significantly reduced by frost injury, especially in cases where injuries were sustained during several years. Survival was only slightly affected by frost damage.     

Frost hardiness of nutrient-loaded two-year-old <Emphasis Type="Italic">Picea abies</Emphasis> seedlings in autumn and at the end of freezer storage

The effects of nutrient loading (NLOAD) on the frost hardening and dehardening of Picea abies (L.) Karst. seedlings were investigated under nursery conditions. Before NLOAD, second-year container seedlings were either short-day (SD) treated for 3 weeks in July or left for the natural photoperiod (CO). By mid-September, after 5 weeks of NLOAD, the fertilization of three foliar nutrient concentration levels (low = L-SD, medium = M-SD, and high = H-SD) for the SD-treated seedlings and one (medium = M-CO) for the CO-seedlings was completed. The NLOAD resulted in foliar nitrogen concentration 10.6, 16.1, 22.3, and 17.5 g kg⁻¹ for L-SD, M-SD, H-SD and M-CO seedlings, respectively. The NLOAD had no effects on the morphology or dry mass variables of the seedlings, while SD-treatment reduced the dry mass of shoots, but not that of roots. The frost hardiness (FH) of different batches of the seedlings was assessed by the visual scoring of damage in their needles, stems and buds after their controlled exposure to freezing during frost hardening and dehardening. The low nutrient concentration in the SD-treated seedlings (L-SD seedlings) resulted in poor FH, to an even lower extent than that of the M-CO seedlings. The NLOAD did not affect the dehardening of the seedlings at the end of the freezer storage in the following spring.     

Corrigendum to: Growth of white spruce underplanted beneath spaced and unspaced aspen stands in northeastern B.C.—10 year results

Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39-year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51 m² ha⁻¹. Thinning of overstory aspen to 1000 or 2000 stems ha⁻¹ did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C.     

Growth of white spruce underplanted beneath spaced and unspaced aspen stands in northeastern B.C.—10 year results

Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39 year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51 m² ha⁻¹. Thinning of overstory aspen to 1000 or 2000 stems ha⁻¹ did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C.     

Fertilization of Danish Forests: A Review of Experiments

Fertilization experiments in Norway spruce stands on nutrient-poor sites have been practised in Denmark since the eighteenth century. Until 1950, the main aim was to find a nitrogen (N) source that improved the survival of plants in the early growth phase. The N supply could be improved by intercropping with N 2 -fixing plants, and fertilization with phosphorus (P) and potassium (K) improved the growth of the N 2 fixers, thereby improving tree growth and survival. Positive responses of P and K in spruce cultures were seen in the 1960s, and in most cases the N response was dependent on the supply of P and K. Fertilization experiments in mature spruce stands began in the 1960s. Despite 20 yrs of experimentation, no trends can be deduced. The results discouraged fertilization aimed at increasing growth in mature stands, and fertilization stopped in 1989. After 1980, fertilizers were used in experiments aimed at clarifying the causes and effects of forest decline. Fertilization and liming counteracted soil acidification and increased needle nutrient concentrations when they were below deficiency levels. However, positive growth responses have only been recorded in some of the experiments where nutrient deficiencies were overcome. The experiments have not resulted in practical revitalization programmes. Future fertilization of Danish forests may be limited to systems where nutrient extraction is in excess of the carrying capacity of the ecosystem, and presumably where spruce plantations are converted to broadleaved forests. Finally, future events of deposition of acidifying compounds may necessitate counteractive measures.     

Frost tolerance of two-year-old Picea glauca seedlings grown under different irrigation regimes in a forest nursery

Abstract

This study examined the impact of increased irrigation efficiency on the hardening and frost tolerance of 2-year-old containerized white spruce seedlings in the context of groundwater protection, irrigation management and the maintenance of seedling quality in northern climates. The seedlings were grown under three different irrigation regimes (IR =30%, 40% and 55% v/v; cm³ H₂O/cm³ substrate) and were hardened under conditions of natural photoperiod and temperature. After being subjected to artificial frost tests on four sampling dates during autumn, the seedlings were compared for bud development and frost tolerance. IR had no influence on frost tolerance as determined by measurements of physiological (electrolyte leakage, root water loss) and morphological (shoot damage, root initiation) variables. At the end of the second growing season, there was no significant difference between IRs in seedling height, root collar diameter, shoot dry mass and root dry mass. The results indicate that the amount of water applied to large-dimension 2-year-old white spruce seedlings during the growing season can be significantly decreased without prematurely impeding their growth or hindering their acquisition of frost tolerance.     

氮肥对盆栽欧洲水青冈生物量和营养分配的影响(英文)

调查了施加氮肥(15NH4和15NO3)处理后在两个连续生长季内欧洲水青冈(Fagus sylvatica L.)幼苗地上部分和地下部分的生物量和营养元素分配。盆栽欧洲水青冈幼苗培养于温室大棚内,培养土样取自相邻的三种林分:欧洲水青冈,挪威赤松,欧洲水青冈-赤松混交林。结果表明,氮肥(15N)处理对欧洲水青冈营养元素分配没有显著影响,施加氮素形式决定自身流入植物库的情况。欧洲水青獭收氮素主要以硝态氮的形式,因此,尽管植物体内保存的硝态氮和氨态氮并没有统计差异,但是叶片中硝态氮明显减少。施加硝态氮对欧洲水青冈氮素恢复的影响要大于施加氨态氮。与欧洲水青冈茎、粗根相比,优质根系对氮素(15N)固定是一个缓慢过程。表8图1参40。     

Effects of nitrogen fertilization and temperature on frost hardiness of Aleppo pine (Pinus halepensis Mill.) seedlings assessed by chlorophyll fluorescence

In a 14-week study, 1-year-old Aleppo pine seedlings were grownin two growth chambers. Seedlings were artificially hardenedby decreasing photoperiod and temperature. In each chamber halfof the seedlings were fertilized with nitrogen (8.4 mg seedling^–1).In order to determine the relative importance of the hardeningenvironment versus fertilization, each chamber was programmedto decrease night temperatures down to a low of 8 or 4°C.Chlorophyll fluorescence and frost hardiness was measured fivetimes during the experiment. A sample of seedlings from eachtreatment was exposed to an artificial frost at –5°Cand the freezing effects were assessed by measurements of chlorophyllfluorescence and visual evaluation of needle damage. Seedlingsincreased their frost hardiness during the experiment in allthe treatments but the ratio of variable to maximal chlorophyllfluorescence (F_v/F_m) measured before freezing did not vary duringthe experiment. This indicates that Aleppo pine maintains itsphotosynthetic ability during hardening in contrast to otherconiferous species from colder climates. The effect of nitrogenfertilization on frost hardiness was small in comparison withchamber effect. Nitrogen fertilization slightly delayed theacquisition of hardening in the coldest chamber. Seedlings inthe warmest chamber did not become fully resistant to –5°C,but in the coldest chamber, where night temperature reached4°C, all the seedlings were resistant to the frost. Severedamage caused by frost could be related to a rapid rise of minimalfluorescence (F₀) but the best index of damage was the dropof F_v/F_m after freezing.     

Effects of nutrient loading and fertilization at planting on growth and nutrient status of Lutz spruce (Picea x lutzii) seedlings during the first growing season in Iceland

The low availability of nitrogen (N) is believed to be one of the major limiting factors of forest regeneration in Iceland and frequently under Boreal conditions. Lutz spruce (Picea x lutzii Littl.) seedlings were nutrient loaded using four fertilization regimes in the end of nursery rotation in autumn 2008 and planted in the following spring, with or without a single dose of fertilizer, on two treeless sites in N-Iceland with contrasting soil fertility. Measurements were made after one growing season. The highest loading level without additional field fertilization increased new needle mass by 122% and 152%, for the poor and more fertile site, respectively. The highest loading level with field fertilization increased new needle mass equally, by 188% and 189%, for the poor and more fertile site, respectively. Retranslocation of N, from old needles to current needles, increased with more loading. However, it was clear that nutrient loading could not replace field fertilization, as the seedlings generally showed an additive response to field fertilization and nutrient loading; doing both always gave the best results in seedling performance. As the study only covers field establishment during the first year, the long-term effect of nutrient loading of Lutz spruce cannot be predicted. However, it was concluded that loading might provide an additional input for faster plantation establishment during the first growing season after planting.     

Timing of cold temperature exposure affects root and shoot frost hardiness of Picea Mariana container seedlings

Seventeen‐week‐old black spruce seedlings were hardened under short daylengths and one of three short day length environments, which were either warm (24/16°C, day/night) throughout a 10 week hardening period (WW), cool (10/5°C) throughout hardening (CC), or warm for three weeks followed by seven weeks of cool temperatures (WC). Greatest root and shoot frost hardiness resulted from the exposure of seedlings to three weeks of warm followed by seven weeks of cool temperatures. Seedlings receiving warm temperatures throughout hardening increased in root and shoot frost hardiness, but to a lesser extent than seedlings exposed to cool temperatures. The frost hardiness of woody roots was generally greater than that of fine roots, but the extent of the difference in frost hardiness depended on the time since bud initiation and on the hardening treatment.     

短日照处理在夏季造林中的应用及研究进展

北欧、北美的许多地区在夏季造林前对云杉苗木进行2 ~ 3周的短日照处理,以促进苗木提前形成顶芽和进入休眠,提高苗木的木质化程度,增强苗木抗机械损伤和抵御生物或非生物胁迫的能力;通过抑制苗木的高生长,使碳水化合物更多地向根系分配,可促进根系的生长发育,增强苗木吸收水分、养分的能力,显著改善夏季造林苗木的质量,取得了较好的造林效果。目前,应用短日照处理调控夏季造林苗木质量的相关研究受到广泛关注。文中重点分析短日照处理的起始时间、持续时间和日照长度等主要技术参数对苗木木质化及其抗旱性和抗寒性的影响,并对短日照处理技术在我国夏季造林中的应用提出展望。     

Influence of nutrient supply on spring frost hardiness and time of bud break in Norway spruce (Picea abies (L.) Karst.) seedlings

When spring frosts occur on recently planted forest sites, severe damage may occur to the seedlings. The aim of the present study was to test how different low levels of nutrient concentrations in Norway spruce (Picea abies (L.) Karst.) seedlings affected spring frost hardiness and time of bud break. Seedlings were grown in a greenhouse for one season and supplied with fertiliser containing 22, 43 and 72 mg N l^–1, respectively. The treatments resulted in needle nitrogen concentrations ranging from 0.9 to 1.8% in autumn. After winter storage at 0 °C, bud break was recorded on seedlings growing in the greenhouse, outdoors and in growth chambers at 12 °C and at 17 °C. Freezing tests were performed on seedlings directly removed from winter storage and following one week growth in the greenhouse. Seedlings receiving fertiliser with 43 mg N l^–1 had less freezing injury than the two other fertilisation treatments in the present study. The earliest bud break occurred in seedlings receiving 72 mg N l^–1.