Effect of warm storage and date of lifting on the quality of Douglas-fir seedlings

The effect of warm storage (15 °C)for up to 21 days on the vitality of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings lifted on four occasions from October to January wasassessed using fine root electrolyte leakage (REL). After 0, 7 and 21 days warm storage, additionalseedlings were potted and placed in a controlledgreenhouse environment to determine root growthpotential (RGP) after 4 weeks and survival after 8weeks. REL was a poor indicator of survival potential;REL increased after 7 days storage, despite the factthat RGP and survival were unaffected. REL increased further during the remainder of the 21-days storage period, but values were often not greatly different from those following 7days storage. Storage for up to 21 days greatlydecreased RGP and survival. Seedlings lifted inOctober and November were most affected by storagetreatments, but differences among lifting dates wererelatively small.     

Fine root electrolyte leakage and moisture content: indices of Sitka spruce and Douglas-fir seedling performance after desiccation

In spring 1992, 2-year-old bare-rooted seedlings of Sitka spruce (Picea sitchensis (Bong.) Carr.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were exposed for 0, 0.5, 1.0, 1.5, or 3 h in a controlled environment room at 20°C. Plants were desiccated in batches during February and March; 100 seedlings of each species were planted in 5 20-plant plots at each of 6 planting sites using the normal planting times and methods of each area. The effect of exposure was assessed within 24 h of desiccation on a subsample of plants by measuring fine root moisture content and electrolyte leakage and, in a limited number of cases, needle water potential. These measures were related to survival and growth after the first and second growing seasons.There were significant interactions between the effect of desiccation and site. The measurements following desiccation were significantly related to survival and growth on some but not all sites; in general, the effect of condition was more pronounced on sites with low spring rainfall than on sites with greater than 100 mm rainfall per month during the spring of planting. Root electrolyte leakage was significantly related to performance in slightly more cases than needle water potential or root moisture content.     

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.     

Stress resistance levels change little during dormancy in ash,sessile oak and sycamore seedlings

The physiological status of ash (Fraxinus excelsior L.), sessile oak (Quercus petraea (Matt.)) and sycamore (Acer pseudoplatanus L.) seedlings sampled from nurseries in Ireland between October and May, 1995/1996 and 1996/1997 was investigated. The results of heat treatments applied to taproots in vitro and evaluated using root electrolyte leakage (REL) indicated that sycamore was more easily damaged than the other species but lift date effects were small in all species. Dormancy release began later each year in ash (mid-November) than in oak or sycamore (late October to early November). The results of the REL and other data indicated that there was little change in stress resistance from November to about March (and April for some parameters). Sycamore was most active (highest shoot xylem pressure potential, REL, and root growth potential) during the winter, suggesting that adverse handling during this period is likely to reduce plant quality than in ash or oak. Field performance was good regardless of lifting/planting date.     

Physiological and field growth responses of oak seedlings to warm storage

The effect of warm storage (15°C) for 0, 15 or 31 days, applied after cold storage until April, and date of lifting to cold storage on the physiological condition and field performance of two-year-old oak seedlings (Quercus robur L.) was investigated. Assessments before planting included plant moisture status, root and shoot dry weight, root growth potential (RGP), while after planting root growth, shoot growth phenology, shoot and root dry matter accumulation and stem quality were assessed. Warm storage effects were large, but lift date effects were small. Warm storage for 31 days reduced height and diameter growth, stem quality, total biomass, root growth, and reduced stem quality in the field, but 15 days storage had a smaller effect. Warm storage delayed bud break and shoot growth cessation but survival was unaffected. The depletion of food reserves during storage and low moisture availability might have caused shoot dieback leading to the development of poor quality stems. There was evidence that dry weight fraction of both the shoot tip and the taproot provided good information on the quality of the stock before planting. RGP was also a good indicator of quality. Electrolyte leakage readings from fine and taproots were not reliable indicators of plant quality.     

Effect of Desiccation on Water Status and Forest Performance of Bare-rooted Sitka Spruce and Douglas Fir Transplants

Sitka spruce transplants which had been exposed to drying conditionswere assessed for shoot water potential (), shoot moisture content(MC), water saturation deficit (WSD) and root moisture content(RMC) before forest planting. Exposure for 1 hour 44 minuteshad no effect on subsequent survival or growth, but exposurefor 3 hours 18 minutes reduced survival to 68 per cent aftertwo years and significantly reduced height growth. The damagedplants were clearly distinguished at the time of planting by and RMC but not by MC or WSD. After a range of desiccation treatments, survival was high inSitka spruce unless RMC had fallen below 180 per cent but survivalwas reduced in Douglas fir with smaller reductions in RMC or. During the desiccation treatment, Douglas fir started withand maintained a higher RMC than Sitka spruce and reached lowlevels of less rapidly. The poor performance of desiccatedDouglas fir was therefore not the result of an inability toconserve water. After rewetting for one hour in the dark RMC was restored butnot , and there was no significant effect on survival or growthin either species. It may be possible to devise a method to establish when plantsare in poor condition by direct or indirect measurement of RMC,but high levels of RMC can be misleading if rewetting has occurred. Handling systems which involve brief periods of exposure aretolerable for Sitka spruce but not for Douglas fir, and specialmeasures are justified to ensure that the latter species isnever subjected to root desiccation during handling.     

Initial moisture stress,budbreak and two-year field performance of three morphological grades of slash pine seedlings

This study examined the relationship between root collar diameter, plant moisture stress and budbreak in three morphological grades of bareroot 1+0 slash pine (Pinus elliottii Engelm.) nursery seedlings and assessed the role of these parameters in predicting field performance potential under operational conditions. Two months after outplanting seedlings with small (3.2 mm) diameters exhibited greater signs of moisture stress than those with the largest (4.7 mm) diameters, as determined by lower xylem pressure potential values. Intermediate and large-sized seedlings (diameter >3.2 mm) showed earlier budbreak than smaller seedlings with more rapid shoot elongation after planting and had significantly greater survival rates for two years after planting on both a moist flatwoods and a dry sandhill planting site. However, after two years on the more favorable moist site, height and diameter measurements of seedlings with significantly smaller diameters initially did not differ from those of intermediate sized seedlings (diameter >3.2 and <4.7 mm). Large seedlings had greater second-year leader and diameter increments and attained greater total height and diameter after two years on both sites. Decreasing the proportion of smaller seedlings included in the field performance analyses increased overall mean plantation survival while increasing the proportion of large seedlings increased mean two-year total height and diameter as well as annual growth increments.     

Root exposure effects on water relations of Eucalyptus nitens nursery stock

Bare-root seedlings of Eucalyptus nitens frequently exhibit water stress after planting resulting in leaf lamina damage and reduced leaf area. Two trials examined effects of root exposure and desiccation between lifting and transplanting on post-planting water relations, leaf retention and root growth. Plants with roots exposed on a glasshouse bench initially lost water rapidly. In one trial ₁ declined to around –2.0 MPa within 2.5 h, after which there was no further change with exposure up to 7.5 h. In the second trial, the initial decline in ₁ was more rapid, reaching below –2.0 MPa in the first hour, before remaining stable with continuing exposure up to 4.5 h. A further decline then continued to –4.0 MPa after 7.5 h.Two days after transplanting into potting mix, day – time leaf water potentials in all desiccation treatments had declined to near –2.0 MPa. Hydraulic resistivity, measured as leaf specific resistivity two days after transplanting, increased following exposure for greater than 2.5 h, but there was no further increase between 4.5 and 7.5 h. The increase in resistivity corresponded with leaf water potential declining below –2.0 MPa during exposure.In the second trial, increasing root exposure time resulted in decreased leaf area due to lamina necrosis. Root growth, measured three weeks after planting, was also reduced. and there was also a positive curvilinear relationship between leaf area remaining at three weeks and new root growth. The results are discussed in terms of hardiness and the management of E. nitens seedlings from nursery to plantation.     

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.     

Root growth capacity and field performance of Pinus sylvestris and Picea abies seedlings

Correlations between root growth capacity (RGC), at the time of planting, and field performance were studied for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings. Before planting a gradient in seedling viability was generated through exposure to low root temperatures and different winter storage regimes. The hypothesis that high RGC values would improve field performance was to some extent verified for pine seedlings while no correlations could be registered for spruce. Reasons for these results are discussed.     

Performance and quality of <Emphasis Type="Italic">Cupressus sempervirens</Emphasis> L. mini-plug seedlings under reduced photoperiod

Short-day treatment has been used for some conifer species to improve planting stock quality. The aim of this paper was to study the effect of short-day treatment on performance and quality of young seedlings of Italian cypress (Cupressus sempervirens L.), a conifer species abundant in the Mediterranean area. Seeds of Italian cypress were sown in mini-plug cavities. After 5 weeks of growth, seedlings were subjected to four different photoperiods: (a) 14 h (control), (b) 8 h, (c) 6 h, and (d) 4 h for a period of 1–3 weeks, before they were transplanted to bigger size containers. Reducing photoperiod did not result in bud formation or shoot inhibition although it increased the number of lateral shoots. Seedlings subjected to 6-h photoperiod for 2 weeks during pre-cultivation in mini-plugs had improved root characteristics, giving them a higher potential for outplanting success, especially in Mediterranean areas.     

Does RGP predict field performance? A debate

Root Growth Potential (RGP) has become the most commonly used and reported measure of seedling quality. It has also been used to predict field performance after planting, but not everyone agrees that this is an appropriate use. The authors were solicited by the Making the Grade Organizing Committee to engage in a debate on the topic Does Root Growth Potential (RGP) predict Field Performance with D. G. Simpson arguing the affirmative position and G. A. Ritchie the negative. Simpson's key debate points are: (1) RGP predicts actual field performance when trees are dead __ dead trees do not grow, (2) RGP predicts field performance potential when water uptake is dependent on new root growth, and (3) RGP is a practical tool to monitor and improve reforestation system performance. Ritchie, arguing against the proposition, maintains that: (1) the logic which underlies the dependence of Field Performance on rapid root growth after planting is flawed, i.e. root growth immediately following planting rarely occurs because soils during the planting season are generally below the threshold temperature for root growth, and (2) RGP does not provide enough information about the complex of interacting factors which control Field Performance to give reliable, consistent predictions. The authors conclude by proposing a conceptual model which accommodates both positions.     

Surface quality sensing of trembling aspen (Populus tremuloides Michx.) veneer products by near infrared spectroscopy

Abstract

The potential of near infrared spectroscopy (NIRS) to estimate wood moisture content (MC), surface energy characteristics and adhesive bond strength were evaluated on aspen (Populus tremuloides Michx.) veneer subjected to different drying times. For samples dried progressively at 103°C, the best MC prediction model was for the total MC range (0–100%) with an R² value of 0.68. However, exposure at 180°C produced surface colour changes, and the CIE L*a*b* colour parameters measuring colour changes were better estimated using the 400–900 nm spectral data than the 1100–2400 nm spectral data. Increased exposure time at 180°C resulted in lower wettability and, hence, larger contact angles, especially when ethylene glycol was used as probe solvent. Lap shear strength tests on veneers showed that adhesion by phenol formaldehyde resins was impaired by the high temperature exposure; however, the lap shear strength test had high variability so there was not always a clear relationship between contact angle and lap shear strength test.     

Assessment of seedling storability of Quercus robur and Pinus sylvestris

Pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.) seedlings were lifted on several occasions during autumn 1997 to determine the relationships between storability and frost hardiness. On each lifting date their physiological status was determined by assessment of shoot and root electrolyte leakage and frost hardiness, assessed as freeze-induced electrolyte leakage. Additional seedlings were simultaneously cold-stored for field planting and assessment of preplanting root growth potential in April 1998. First year field performance was determined the following winter. Storability and cold acclimation patterns differed between the two species. Both were negatively affected by early lifting, but oak was less sensitive with respect to survival, and pine attained tolerance to cold storage more rapidly and earlier with respect to growth increment. The correlations between shoot frost hardiness and performance suggest that freeze-induced shoot electrolyte leakage (SEL_diff?20) below a threshold of 5% is a good storability predictor for Scots pine in Denmark. A completely reliable criterion for pedunculate oak could not be established.     

Biomass production and potential water stress increase with planting density in four highly productive clonal Eucalyptus genotypes§

The choice of planting density and tree genotype are basic decisions when establishing a forest stand. Understanding the interaction between planting density and genotype, and their relationship with biomass production and potential water stress, is crucial as forest managers are faced with a changing climate. However, few studies have investigated this relationship, especially in areas with highly productive forests. This study aimed to determine the interaction between biomass production and leaf water potential, as a surrogate of potential water stress, in different clonal Eucalyptus genotypes across a range of planting densities. Four clones (two clones of E. urophylla × E. grandis, one clone of E. urophylla, and one clone of E. grandis × E. camaldulensis) and four planting densities (ranging from 591 to 2 949 trees ha^?1) were evaluated in an experimental stand in south-eastern Brazil. Biomass production was estimated 2.5 years after planting and predawn (ψ_pd) and midday (ψ_md) leaf water potential were measured 2 and 2.5 years after planting, in February (wet season) and August (dry season) in 2014. For all clones, total stand stemwood biomass production increased and leaf water potential decreased with planting density, and their interaction was significant. Thus, wood biomass at tighter spacings was higher but exhibited lower leaf water potentials, resulting in a trade-off between productivity and potential water stress. These are preliminary findings and still need to be supported by more experimental evidence and repetitions. However, in light of the increased frequency of extreme climate events, silvicultural practices that are tailored to the potential productivity of each region and that result in low potential water stress should be considered.     

Heat damage in boxed white spruce (Picea glauca [Moench.] Voss) seedlings: Its pre-planting detection and effect on field performance

This study investigated the effects of holding 1+0 PSB313a white spruce (Picea glauca (Moench.) Voss) seedlings in storage boxes at air temperatures of 5, 10, 20, 30 and 40°C for 12, 24, 48, 72 and 96 h before planting. The ability to detect physiological damage to seedlings as a result of such treatment, before planting, was also examined. After one growing season, no needle damage or mortality >8% was found for temperature treatments up to 20°C for 4 days. At 30°C and above, seedling damage and mortality increased, while bud flush, shoot height, stem diameter and shoot dry weight decreased with increasing temperature and duration of treatment. Seedling mortality in the field was 100% after the 40°C treatment exposure for 72 h or longer. Pre-planting needle electrolyte leakage was indicative of visible needle damage 14 days after planting, whereas stem electrolyte leakage and root growth potential were more closely related to end of season plantation mortality. Despite the lack of damage observed at 20°C or below, preplanting exposure of white spruce seedlings to temperatures above 5°C, during transportation and field storage, is not recommended.     

Field performance potential of a somatic interior spruce seedlot

This study defined the field performance potential for 34 genotypes that composed a somatic seedlot of interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex. Engelm.) crosses, white spruce (P. glauca (Moench) Voss) crosses, or a mixture. Each genotype was measured for morphological attributes: height, diameter, shoot dry weight, root dry weight, shoot-to-root ratio, height-to-diameter ratio at time of lifting. Each genotype was also measured for physiological attributes of cuticular transpiration (TFD_cut), osmotic potential at turgor loss point (Ψ_tlp) and freezing tolerance (index of injury at −6°C and −4°C; II_@−6 & II_@−4) during inactive and active shoot growth phases. Shoot growth potential (SGP = length of new leader elongation) and root growth potential (RGP) were conducted under four environmental regimes: nutrient-rich/well-watered, nutrient-poor/well-watered, low root temperature, and planting stress conditions. The somatic seedlot met target height, diameter and RGP standards for a plantable seedling crop in British Columbia, Canada, though genotypes differed in morphology at time of lifting. These genotypes also differed in their measured physiological attributes (TFD_cut, Ψ_tlp, II_@−6 and II_@−4) at time of lifting and during active shoot growth. Genotypic differences were also found for SGP and RGP under different testing environments. A stock quality assessment program describing elite genotypes within a seedlot can aid foresters in applying benefits of clonal forestry. Raymund S. Folk is now self employed.     

The Influence of Desiccation, Rough Handling and Cold Storage on the Quality and Establishment of Sitka Spruce Planting Stock

In January 3-year-old Sitka spruce were lifted and treated eithercarefully or roughly. Plants in each treatment were either transferredto the laboratory for testing, or transferred to cold storageat –1°C. In the laboratory, half of the plants ineach treatment were desiccated to shoot water potentials ofless than –2.0 MPa. Plants were then tested for root growthpotential (RGP), bud dormancy, frost hardiness and carbohydratecontent before transplanting at a field site, Additional plantswere removed from the nursery and cold store at approximatelymonthly intervals until late April, and then treated as above.In April, plants in each treatment were transferred to on-sitefield storage (sheughs), for 2 or 4 weeks prior to testing asabove. Carefully handled plants maintained large RGP which was positivelycorrelated with plant water potential, root water content, shootrelative growth rate and field survival. Overall RGP was reduced: 59 per cent by desiccation; 85 percent by rough handling; and 98 per cent by desiccation and roughhandling in combination. On site storage for 4 weeks in April/May reduced RGP. Whereplants produced more than 30 new roots > 1 cm long in RGPtests, field survival exceeded 90 per cent. Cold storage at–1°C maintained RGP, (of carefully handled plants),bud dormancy and shoot frost hardiness at approximately pre-storagevalues. In contrast, total nonstructural carbohydrate contentdeclined in cold store but increased in March/April for plantsin the nursery.     

Seed storage behavior of <Emphasis Type="Italic">Knema attenuata</Emphasis>, an endemic species of Western Ghats,India

We performed desiccation and storage trials to better under- stand storage behavior of Knema attenuata seeds. Mature seeds with moisture content (MC) of 31% exhibited 73% germination. During the period of desiccation (open lab condition) seeds with MC 23% showed 40% germination. After further drying to MC 21% germination was reduced to 16%. Complete loss in viability resulted when seed moisture was reduced to 18%. The seeds stored at -10°C, 0°C, 10°C and 28±2°C (open lab condition) lost their viability within 10 days. Seeds stored in sealed polythene bags and moist sand retained viability for more days than did seeds stored under all other storage conditions. Sensitivity of seeds to lower temperature and desiccation suggest that the storage be- havior of K. attenuata seeds is recalcitrant. Seeds stored in moist condi- tions can, at best, be stored for a period of two months.     

Drought susceptibility and recovery of transplanted Quercus rubra seedlings in relation to root system morphology

? Transplant shock, implicated by depressed seedling physiological status associated with moisture stress immediately following planting, limits early plantation establishment. Large root volume (Rv) has potential to alleviate transplant shock because of higher root growth potential and greater access to soil water.

? We investigated impacts of drought and transplant Rv on photosynthetic assimilation (A), transpiration (E), stomatal conductance (g _s ), predawn leaf xylem water potential (Ψ_L), and growth of northern red oak (Quercus rubra L.) seedlings to explain mechanisms associated with susceptibility to transplant shock. One year-old barerooot seedlings were graded into four Rv categories and either well watered or subjected to drought consisting of low, medium, or high moisture stress by discontinuing irrigation at 22-day intervals for 3 months. Thereafter, all treatments were re-watered to examine recovery.

? Transplant shock was signified by reduced A, E, g _s, and Ψ_L, which generally increased with increasing moisture stress and Rv. Physiological status improved during recovery, though stress was still evident in seedlings exposed to medium or high moisture stress and in larger Rv seedlings. Growth declined with increasing moisture stress but was generally similar among Rv treatments, likely reflecting greater A at the whole plant level and/or reliance upon stored reserves in large Rv seedlings.

? The most effective drought avoidance mechanisms were root growth, stomatal regulation, reduced leaf area, and higher growth allocation to roots relative to shoots. Our results suggest that large initial Rv does not enhance drought avoidance during the first season after transplant in northern red oak seedlings.