Fall fertilization enhanced nitrogen storage and translocation in Larix olgensis seedlings

Fall nutrient loading of deciduous forest nursery seedlings is of special interest because of foliage abscission and varied translocation patterns. For non-deciduous seedlings in the nursery, fall fertilization typically can reverse nutrient dilution and possibly increase nutrient reserves; however, this technique has received little attention with deciduous conifer trees that translocate nutrients before abscising foliage. We evaluated how fall nitrogen (N) fertilization affected N storage and translocation in the deciduous conifer Olga Bay larch (Larix olgensis Henry) seedlings during the hardening period. Seedlings were supplied with 25 mg N seedling^?1 for 15 weeks before hardening and fall fertilization treatments began with a three week application period of K¹⁵NO₃ at 0, 5, 10 and 15 mg N seedling^?1. During the hardening period, fall N fertilization had little effect on seedling morphology. The N concentration and content of needles decreased dramatically as needles abscised, while that of stems and roots increased. Six weeks after fall N fertilization ceased, all seedlings translocated similar net N from their needles. For the control seedlings, this accounted for 84 % of the N stored in stems and roots. For fall fertilized seedlings, however, the proportion of N stored in stems and roots translocated from needles accounted for only 41–61 % of the total because of absorption of fall fertilizer that was translocated directly to stems and roots. Six weeks after fall fertilization, the distribution pattern of N concentration and content in seedlings was found in this order: stems > fine roots > coarse roots > needles. Our results suggest that providing deciduous conifer seedlings N during hardening, in this case Olga Bay larch, is a way to promote nutrient loading during nursery production.     

Growth and nutrient dynamics of <Emphasis Type="Italic">Betula alnoides</Emphasis> seedlings under exponential fertilization

Betula alnoides is a fast-growing hardwood species grown in large plantations in Southeast Asia and South China. Nitrogen requirements for producing robust seedlings, growth and nutrient dynamics were investigated using exponential fertilization treatments. Root collar diameter, height, dry mass and nutrient contents of seedlings increased exponentially in all fertilization treatments as time progressed. Moreover, with water soluble fertilizer (Plant Products plus microelements N–P₂O₅–K₂O: 20–20–20), 300 mg N seedling^?1 was adequate. Vector analysis revealed that P was the most responsive nutrient element, followed by N and K. Dilutions of N and K were evident in the plants without N addition, which induced initial P sufficiency and then luxury consumption probably due to the antagonistic interaction between N and P. However, deficiencies of N, P and K were mostly observed in all exponential regimes during the experiment because seedling growth rate exceeded nutrient uptake rate, inferring that further study on improving the nutrient uptake efficiency is needed. Analysis of relationships among nutrient supply, dry mass, N content and N concentration demonstrated that 100–400 mg N seedling^?1 induced sufficiency to luxury consumption of nitrogen without significant change in dry mass, and 400 mg N seedling^?1 is recommended to apply for nutrient loading of seedlings before outplanting. The findings will help improve seedling quality and enhance the production of robust seedlings for plantation forestry of this species.     

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.     

Fertilization at planting influences seedling growth and vegetative competition on a post-mining boreal reclamation site

Reclamation of post-mining sites is challenged by limiting factors including adverse soil chemical and physical properties, along with weed competition. Fertilization may alleviate nutrient deficiencies, but broadcast fertilization with immediately available fertilizers (IAF) results in generally low rates of nutrient recovery for planted trees. Directed application of controlled-release fertilizer (CRF) to the rhizosphere offers an alternative to extend nutrient longevity while reducing nutrient leaching or uptake by competing vegetation. We evaluated white spruce (Picea glauca (Moench) Voss) and aspen (Populus tremuloides Michx.) development on a mine reclamation site in the Oil Sands Region of northern Alberta in response to IAF and polymer-coated CRF (3–4 and 8–9 month release). IAF and CRF (each NPK plus other macro- and micro-nutrients) were applied at 20 and 40 g N seedling^?1 and 2 and 4 g N seedling^?1, respectively. No effect on seedling survival occurred. White spruce year-1 height and diameter growth responded positively to both IAF and CRF relative to non-fertilized controls, but in year-2 seedlings treated with CRF (i.e., 8–9 month) outperformed those fertilized with IAF, which were similar to controls. Aspen height growth did not respond strongly to fertilization in either year, but diameter growth showed positive responses to all fertilizer treatments in year-1 and to all CRF treatments and the high IAF rate in year-2. Responses were attributed to a pronounced increase in vegetative competition observed for IAF relative to CRF or controls following the first growing season, and generally higher levels of foliar N in year-1 for CRF compared to IAF or unfertilized trees. Thus, directed root zone application of CRF promoted seedling growth responses similar to or better than those induced by broadcast IAF applications, but at 90–95 % lower N application rates.     

Is nitrogen fertilization in the nursery a suitable tool for enhancing the performance of Mediterranean oak plantations?

Mediterranean oaks frequently have poor performance in forest restoration projects. We analyzed if nitrogen (N) fertilization during nursery cultivation enhances the outplanting performance of two ecologically distinct oaks, Quercus coccifera L. an evergreen shrub, and Quercus faginea L., a deciduous tree. Additionally, we compared the sufficiency N levels of both oaks and if root growth capacity (RGC) and photosynthesis testing at low air temperature better discriminated among fertilization treatments than testing at mild temperature. Plants were cultivated under five N fertilization rates (0, 30, 75, 150 and 200 mg N plant^?1) for one growing season. At the end of the cultivation period several plant material and performance attributes were measured. RGC and photosynthesis were assessed at mild temperature and cool conditions in Q. coccifera, while in Q. faginea these attributes were only analyzed at mild temperature conditions. Q. coccifera seedlings were transplanted into four terraces that imposed increasing drought stress, while Q. faginea seedlings were transplanted into an abandoned wheat cropland. Sufficiency level was higher for the tree (150 mg N plant^?1) than for the shrub (75 mg N plant^?1) Nitrogen-deprived Q. coccifera plants had higher frost damage than remaining treatments, which did not differ among them. Fertilization in Q. faginea did not affect photosynthesis rate but it delayed leaf senescence and abscission. RGC increased with fertilization in both species. Testing temperature did not change the effect of fertilization on RGC in Q. coccifera. Photosynthesis in cool conditions discriminated N-deprived seedlings from the remaining treatments, but treatments did not differ in photosynthesis at mild temperature. Fertilization enhanced outplanting survival in Q. coccifera, primarily in the terraces imposing stronger drought stress, while fertilization only increased growth in the terraces imposing mild drought stress. Overall, survival and growth was positively related to seedling size at planting in both oaks. Additionally, Q. coccifera survival was also positively related to RGC in the harsh planting conditions. Field growth was positively related to RGC and plant N concentration in both oaks but the relation was weak or nonexistent under harsh conditions in Q. coccifera. We conclude that fertilization in the nursery is an important tool for improving the success of oak plantations in Mediterranean continental sites, and that large and N-rich seedling have greater field performance than small and low tissue N concentration seedlings, especially in harsh field sites.     

Fall fertilization of Pinus resinosa seedlings: nutrient uptake, cold hardiness, and morphological development

? Fall fertilization may increase plant nutrient reserves, yet associated impacts on seedling cold hardiness are relatively unexplored.

? Bareroot red pine (Pinus resinosa Ait.) seedlings in north-central Minnesota, USA were fall fertilized at the end of the first growing season with ammonium nitrate (NH₄NO₃) at 0, 11, 22, 44, or 89 kg N ha^?1. Seedling morphology and cold hardiness [assessed by freeze induced electrolyte leakage (FIEL)] were evaluated six weeks after fertilization and following the second growing season.

? Seedling height and number of needle primordia increased with fertilizer rate for both sampling years. Seedlings fertilized with 44 and 89 kg N ha^?1 attained target height (15 cm) after the second growing season. Shoot and root N concentration increased after the first growing season in fall fertilized seedlings compared to controls. Fall fertilized seedlings had lower FIEL (i.e., increased cold hardiness) compared to controls when tested at ?40 °C after the first growing season, but no significant differences in FIEL of control and fertilized seedlings were observed after the second growing season.

? Results suggest that fall fertilization of red pine seedlings can help render desired target height in the nursery, while maintaining or increasing cold hardiness levels.

     

Morphology, gas exchange, and chlorophyll content of longleaf pine seedlings in response to rooting volume, copper root pruning, and nitrogen supply in a container nursery

Few pine species develop a seedling grass stage; this growth phase, characterized by strong, carrot-like taproots and a stem-less nature, poses unique challenges during nursery production. Fertilization levels beyond optimum could result in excessive diameter growth that reduces seedling quality as measured by the root bound index (RBI). We grew longleaf pine (Pinus palustris), a grass stage species, in containers of four different volumes (60–336 ml) either coated with copper oxychloride or left untreated and fertilized at low, medium, or high levels of nitrogen (N). In general, N concentration of tissues rose as N rate increased, with larger changes in concentration occurring between low and medium levels than between medium and high levels. N rate influenced root tissue N concentration less than it did stems and needles. Subtle needle color differences caused by N rate were significant, suggesting its potential utility during nursery production. As expected, seedlings grew larger as container volume increased and as N rate increased. Copper treatment, which we posited could influence the RBI, tended to increase root-collar diameter and tap root biomass and decrease total root volume. Chlorophyll abundance was affected more by N rate than by container volume or copper treatment, but photosynthesis was affected more by copper treatment than N rate or container size. Although RBI was 25 % greater for seedlings grown in small containers with high N rates than those grown in large containers with low N rates, RBI ranged only from 11 to 15 %, well below the critical 27 % threshold.     

Chlorophyll fluorescence of stem cambial tissue reflects dormancy development in Juglans nigra seedlings

Assessment of chlorophyll fluorescence (CF) of forest tree seedlings can provide important insight into physiological function, dormancy status, and stress resistance. This evaluative tool has been measured routinely using foliage on conifer seedlings to assess seedling physiological status during winter dormancy. Absence of foliage during dormancy has thus far precluded the potential application of CF to seedling quality assessment of temperate deciduous hardwood seedlings. Because stems contain chlorophyll, however, assessment of CF using stem tissue may serve as an effective alternative tissue type to facilitate CF measurements. We collected Juglans nigra L. (black walnut) seed from two provenances (Alabama and Indiana, USA) and subjected 1-year-old container seedlings from these provenances to a simulated hardening regime (i.e., progressively decreasing temperatures and photoperiods) in a growth chamber environment over an 18-week period; CF of stem tissue (evaluated as ΦPSII, efficiency of photosystem II) was sampled periodically at seven time intervals. Though both provenance and measurement period significantly affected ΦPSII, measurement period had a much more pronounced effect. Values for ΦPSII fluctuated (ranging from 0.45 to 0.72) during the simulated growth and hardening regimes, generally decreasing over time for both provenances. Our results suggest that physiological status of temperate deciduous seedlings may be effectively evaluated during dormancy by assessing CF of stem tissue.     

Influence of sulfometuron methyl on conifer seedling root development

On three sites in coastal northwestern Oregon, USA, seedling root and shoot development were assessed for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western red-cedar (Thuja plicata Donn ex D. Don) container seedlings under varying sulfometuron methyl (Oust XP^®) herbicide application treatments. Treatments consisted of application of 0.16 kg active ingredient (ai) ha^?1 as a site preparation in fall 2003, a release application in fall 2004, or a control treatment with no application. Seedlings were planted in winter 2004 and measurements recorded in summer 2004, winter 2005, and summer 2005. During first season growth, western red-cedar seedlings showed the greatest negative impact to site preparation compared to the control with overall average new root length outside the root plug reduced by 67%. Significant reductions in root length also occurred for western hemlock (47%) and Douglas-fir (40%) seedlings. About 9 months after the release treatment, and 21 months after the site preparation application, there were no significant differences between treatments for any measured parameter. These findings suggest that seedlings under the site preparation treatment recovered from initial damage incurred to the root system. Lack of seedling response under the release treatment may be the result of opposing influences from the herbicide application associated with seedling phytotoxicity and enhanced seedling development resulting from effective vegetation control. Although our study was limited to 21 months following planting, reduced vegetation cover in the site preparation and release treatments suggests that these treatments may benefit future seedling growth.     

氮素营养对闽楠幼苗生长及光合特性的影响

设置0、50、100、150、200、300、400、600 mg·株-1 8个N处理,通过盆栽试验研究氮素对闽楠苗生长及光合特性的影响.结果表明:随着供氮量的增加,闽楠苗高、地径、叶面积和根、茎、叶及整株生物量均呈现先增加后降低的趋势,其中,苗高、地径和叶面积均在供氮量100 mg·株-1时最高,而各器官生物量及整株生物量均在供氮量150 mg·株-1时最大;根冠比则随着供氮量的增加呈现单调递减趋势;闽楠苗光合特性与生长表现是契合的,随供氮水平的提高,闽楠苗叶绿素a、b及总量先升高后降低,净光合速率、气孔导度、胞间二氧化碳浓度和蒸腾速率值也均呈先仰后抑之势,恰在供氮量100 mg·株-1时,以上光合参数值均达最高,且不同氮素处理间闽楠光合气体交换参数和蒸腾速率差异均显著.综合闽楠苗各生长及光合指标的分析结果,100～150 mg·株-1的供氮量为闽楠苗温室培育的适宜范围.     

Premature shoot growth termination allows nutrient loading of seedlings with an indeterminate growth strategy

Nutrient loading of nursery seedling stock of species with an indeterminate growth strategy is challenging and poorly understood. Here, we explore the use of two potential techniques for nutrient loading of trembling aspen (Populus tremuloides Michx.) seedlings: (1) exponential fertilization and (2) early shoot growth termination in order to divert assimilated nutrients and carbon to storage rather than to growth. In the first study, aspen seedlings were treated with either exponential or constant fertilization rates, both of which supplied the same amount of nutrients over the growing season. Exponential fertilization resulted in overall poor planting stock form (stunted seedling growth and weak root development) and produced only marginal improvements of nutrient status. As a result, the exponential fertilization regime studied cannot be recommended as a treatment for aspen seedlings. In the second study we treated seedlings with a 2 × 2 factorial combination of fertilization and shoot growth inhibitor (SGI) applications with the fertilizer treatments varying in terms of mid-season fertilizer concentrations. Seedlings with SGI application had much higher tissue nutrient and carbon reserve concentrations than seedlings without a SGI application. In addition, nutrient uptake appeared to be more efficient in SGI treated seedlings, which could potentially result in significant reductions of nutrient application rates during aspen seedling production in nurseries. Overall, early shoot growth termination using a SGI appears to be an effective technique to produce nutrient loaded aspen seedlings.     

Fall frost resistance in willows used for biomass production. II. Predictive relationships with sugar concentration and dry matter content

The accumulation of sugars and dry matter in stems in fall was examined in relation to frost hardening in eight willow clones (six clones of Salix viminalis L. and one clone each of S. viminalis x S. schwerenii E. Wolf and S. dasyclados Wimm.). Evidence is presented that three sources of variation in fall frost resistance among the eight clones could be assessed from an analysis of stem composition. First, the pre-hardening value of frost resistance could be assessed from the total sugar concentration. Second, the start of induction of apical growth cessation and hence frost hardening could be distinguished by a stepwise increase in sucrose-to-glucose ratio. Third, the progress of frost hardening during its first phase could be followed from a proportional rise in total sugar concentration and, even more accurately, from a proportional rise in dry-to-fresh weight ratio. In contrast, the second phase of frost hardening was largely uncoupled from sugar and dry matter accumulation. Raffinose and sucrose accumulation seemed to be under differential environmental controls. Sucrose accumulation started with the initiation of growth cessation controlled by photoperiod, whereas raffinose accumulation started with falling temperatures later on. Starch reserves that built up in stems in early fall were partially mobilized later on to support sugar accumulation. In contrast to stems, leaves did not exhibit a preferential accumulation of sucrose in fall.     

Steady-state nutrition of Pinus resinosa seedlings: response to nutrient loading, irrigation and hardening regimes

To test effects of fertilization on late-season growth and nutrient content of container-grown red pine (Pinus resinosa Ait.), seedlings were subjected to a factorial combination of two fertilization regimes (exponentially increasing concentrations providing 25 (1N) and 75 (3N) mg N seedling(-1), respectively) and two irrigation regimes (well-watered and water-stressed) followed by drought-hardening or nonhardening. The fertilization treatments gave rise to steady-state nutrition in the seedlings during the prehardening phase. The 3N treatment increased macronutrient uptake significantly more than dry matter production, particularly in the roots, giving rise to what has been called luxury consumption of nutrients, or nutrient loading. Nutrient loading was higher in well-watered seedlings than in water-stressed seedlings. Among well-watered seedlings, relative growth rate of nutrient-loaded seedlings was more sensitive to drought during the hardening phase than that of nonloaded seedlings. However, when watering was resumed at the end of the hardening treatment, the relative growth rate of the nutrient-loaded seedlings (421%) exceeded that of the nonloaded seedlings (213%). Nitrogen accumulation was also higher in nutrient-loaded seedlings than in nonloaded seedlings during the post-hardening phase.     

Nitrogen budgeting and quality of exponentially fertilized <Emphasis Type="Italic">Quercus robur</Emphasis> seedlings in Ireland

Current policy in Ireland calls for increased quality and quantity of broadleaved seedling plantings. Simultaneously, concerns regarding environmental contamination necessitate development of nursery production methods that minimize impacts. Exponential (E) fertilization has potential for producing high-quality seedlings through nutrient loading, while simultaneously minimizing nitrogen (N) losses during culture. We investigated the effects of a wide range (0.10–1.0 g N seedling⁻¹ year⁻¹) of E fertilization rates on seedling morphology and nutrition of Quercus robur L., as well as soil N status and N budget during one growing season in a bareroot nursery in County Carlow, Ireland. The N budget showed significant N losses, especially in the highest fertilizer treatments, due to high precipitation. Seedlings receiving the 0.5 E rate were morphologically and nutritionally superior to all other treatments. Results indicate that it may be possible to produce 1-0 bareroot seedlings meeting target specifications in Ireland and other countries of similar climate and soils if further manipulations to seedling culture are implemented; however, potential environmental degradation via N leaching must be considered when N loading in wet years.     

The effect of carbon and nutrient loading during nursery culture on the growth of black spruce seedlings: a six-year field study

We tested the effects of exponential nutrient loading and springtime carbon loading during nursery culture on the field performance of black spruce (Picea mariana (Mill.) B.S.P.). Seedlings were grown from seed with a conventional, fixed dose fertilizer (10 mg N seedling⁻¹) or an exponential nutrient loading regime (75 mg N seedling⁻¹). The following spring, seedlings were exposed for two weeks to either ambient (370 ppm) or elevated levels of CO₂ (800 ppm) and then planted in the field; seedling growth was followed for the next six years. Exponential nutrient loading increased seedling height, stem diameter and leader growth, with the largest increases in height and leader length occurring in the first three years after outplanting. Carbon loading increased seedling height and leader length, but only in seedlings that had been exponentially nutrient loaded. A combination of carbon and nutrient loading increased shoot height 26%, stem diameter 37% and leader length 40% over trees that received neither treatment. These results demonstrate that the growth enhancement seen under exponential nutrient loading is maintained under field conditions for at least six years. Carbon loading just before outplanting was a useful supplement to nutrient loading, but was ineffective in the absence of nutrient loading.     

Fall frost resistance in willows used for biomass production. I. Characterization of seasonal and genetic variation

Fast-growing willow clones (six clones of Salix viminalis L. and one clone each of S. viminalis x S. schwerenii E. Wolf and S. dasyclados Wimm.) were compared with respect to growth rhythm and frost hardening in the fall. Frost resistance of stem tissues was assessed by controlled freezing followed by analysis of chlorophyll fluorescence and scoring of visible cambial discoloration. The fluorescence method proved superior to scoring based on visible cambial discoloration because it was more rapid and less subjective, but needed calibration against cambial damage. Frost hardening in mature parts of stems did not start until growth cessation was initiated in the shoot apices, irrespective of whether growth cessation occurred early or late in the fall. Frost resistance varied because of clonal variations in: (1) pre-hardening frost resistance; (2) timing of growth cessation and hence start of frost hardening; and (3) rate of frost hardening. Compared with coastal and southern clones, continental and northern clones started hardening earlier, and a continental clone proceeded through hardening more rapidly at a given temperature. A cross between a continental and coastal clone was intermediate in timing. The pre-hardening frost resistance, however, was unrelated to both growth and frost hardening characteristics.     

控释肥和灌溉方式对栓皮栎容器苗苗木质量及造林效果的影响

[目的]探讨控释肥和灌溉方式对栓皮栎(Quercus variabilis Bl.)容器苗生长、养分含量、基质电导率(EC)及2年造林效果的影响,为培育高质量苗木提供参考。[方法]以栓皮栎容器苗为研究对象,采用双因素完全随机试验设计,设置5个施肥水平(以N元素含量为基准,5个施肥水平分别为:25、75、125、175、225 mg·株~(-1))和2种灌溉方式(上方喷灌(O)、底部渗灌(S)),测定栓皮栎容器苗形态指标、养分含量、根系生长、基质EC值及连续2年造林效果。[结果]表明:(1)施肥量和灌溉方式二者对苗木形态指标影响存在交互效应,225-O处理的苗木地径、根生物量、单株生物量最大,但根生物量、单株生物量在225-O、125-S、175-O处理之间差异不显著。225-S处理的苗高、茎生物量、茎根比最大,茎生物量在225-S与225-O之间差异不显著。(2)苗木茎、根的氮磷钾浓度和含量随施肥量的增加而增大,施肥量125、175、225 mg·株~(-1)处理之间的根氮、磷含量及单株磷含量差异不显著。(3)增加施肥量促进苗木根系的生长,施肥量为125、175、225 mg·株~(-1)处理之间的根系表面积、体积差异不显著。(4)基质EC值随施肥量的增加而增大,底部渗灌显著提高了基质上层、下层的EC值,基质上层、下层的最大EC值分别为4. 69、0. 56d S·m-1,没有对苗木生长产生不利影响。(5)和上方喷灌相比,底部渗灌显著地促进造林第1年幼树的树高、地径生长;造林第1年、第2年的树高和地径均随施肥量的增加而增大,造林第2年,施肥量125、175、225 mg·株~(-1)处理之间的树高、地径差异不显著。[结论]底部渗灌提高了栓皮栎容器苗体内的养分含量,促进了造林第1年幼树树高、地径的生长。施加控释肥有利于苗期苗木质量的提高及造林后苗木的快速生长。综合考虑苗木质量、经济效益、环境利益,培育栓皮栎容器苗可选择底部渗灌和控释肥量为125 mg·株~(-1)的组合(以N元素含量为基准)。     

Production and establishment techniques for the restoration of Nothofagus alessandrii,an endangered keystone species in a Mediterranean forest

Ruil (Nothofagus alessandrii) is an endangered keystone species from the Mediterranean climate zone of Chile. Ruil’s fragile state of conservation urges development of restoration programs, but specific protocols for nursery production and field establishment that ensure plant survival are largely unknown. Therefore, we examined the effect on nitrogen (N) fertilization and container size during nursery production in combination with the use of mesh shelters after outplanting on survival and growth during the first growing season in the field. First year outplanting survival of nursery-grown container seedlings was enhanced when seedlings were given nitrogen (N) during nursery production and deployed with mesh tree shelters in the field. The volume of the container had no effect on outplanting survival and growth. Increasing N from zero to 200 mg N L^?1 provided sufficient N levels, resulting in increased seedling height, root-collar diameter, shoot biomass, and total seedling N and phosphorous concentrations. Additional N provided by the 400 and 600 mg N L^?1 treatments underwent luxury consumption by the seedlings with no further benefits in field performance. Improved growth in the nursery, along with the use of mesh tree shelters after outplanting, especially during the typical summer drought, may be responsible for increased survival during the first growing season. Increasing the performance of nursery-grown ruil seedlings is essential to restoring this endangered, vulnerable, and foundation species within the highly biodiverse, yet seriously threatened endemic Maulino Costero Forest of the Mediterranean climate of central Chile.

     

Effects of boron fertilization in the nursery or after planting on the performance of Norway spruce seedlings on boron-poor sites

Many forest soils in Finland are poor in boron (B), especially otherwise fertile (nitrogen-rich) soils and peatlands. Boron deficiency causes growth disorders affecting young Norway spruce (Picea abies) stands. We studied the effects of B fertilization on the growth and morphology of Norway spruce seedlings. Boron was applied in a nursery and/or after planting in a nursery-field and on a reforestation site, both known to be low in B. The B applied in the nursery increased foliar B concentration in a linear relationship to the amount of B fertilizer but did not affect seedling growth and morphology. Even the highest foliar B concentration (approx. 400 mg kg^?1) did not have harmful effects on the seedlings. Therefore, B fertilization in the nursery can be used for increasing B storage in needles. Boron fertilization at planting increased foliar B concentration in the first season. Afterward, the concentration decreased but remained above the deficiency limit for at least 4–5 years. In the B-poor nursery-field, nonfertilized seedlings began to produce multiple leaders in the second year. On the reforestation site, fewer multiple leaders were found. At the nursery-field site, height growth was stimulated by B fertilization at planting. In conclusion, 200–400 mg m^?2 (2–4 kg ha^?1) of B applied at planting has longer-lasting effects on seedling B status than does B fertilization applied in the nursery, and can improve seedling quality and growth in the first years after planting on B-poor sites.     

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.