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.     

Effects of soil water content and initial root volume on the nutrient status of 2+0 Douglas-fir seedlings

Two-year-old bareroot Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco.) seedlings were graded on the basis of four root-volume categories and transplanted to four moisture-stress treatments (6, 12, 18, and 24% soil water content) in pots. Macronutrient concentrations and contents of both old and new foliar tissue were determined. Decreasing soil water content resulted in higher concentrations of phosphorus, potassium, and particularly nitrogen in both old and new foliar tissue. This can be attributed to reduced growth, translocation, metabolic activity, and nutrient requirement in response to moisture stress. Seedlings with relatively higher root volumes exhibited higher nutrient concentrations and contents, as well as increased growth. Thus, increased total root biomass per unit of soil area with increasing seedling root volume may have resulted in greater nutrient use, supply, uptake, and storage.     

Effects of Douglas-fir 2+0 seedling morphology on field performance

The relationships between field performance of Douglas-fir (Pseudotsuga menziesii) 2+0 seedlings and their initial diameter and root mass were evaluated on five sites in Oregon in the early 1980s to identify opportunities for improving seedling grading prior to planting. Survival and height 3–5 years after planting were positively related to seedling size at the time of planting. On all sites, survival nearly doubled from the smallest to largest diameter classes. Root mass had a similar relationship to survival on sites with environmental stress. Increasing root size class increased survival more for the small diameter classes than for the larger diameter clases. On the other hand, increasing root size class increased total height more for the large diameter class than the smaller ones. Although height was not as strongly affected as survival on several sites, height differences among initial seedling diameter classes were still significant and increasing after five years. Root class effects on height were less important than diameter class effects.     

Growing environment and container type influence field performance of black spruce container stock

Black spruce (Picea mariana [Mill.] B.S.P.) overwintered container crops produced in four container types spanning a range of container sizes and seedling rearing densities were compared for two consecutive years. In 1989 two growing environments (greenhouse and outdoors) were compared. In 1990 three growing environments (greenhouse, coldframe, and outdoors) and two hardening regimes (short day and natural) were compared. Seedlings were outplanted during the spring of 1989 and 1990 and total height and survival were assessed for five years.The outdoor-grown crop was shorter, smaller in root collar diameter and had less dry weight at time of planting than the crops produced in the greenhouse (1989 study) and in the greenhouse and coldframe (1990 study). Although the greenhouse crops in both studies were larger at time of planting, the outdoor-grown crops (1989 and 1990) and coldframe-grown crop (1990) displayed significantly greater annual height increment in the first two years after planting. The enhanced early height growth of the outdoor-grown crops may be due to the natural acclimation created by their growing environment.Seedlings grown in a large volume container, at a low plant density (441 plants/m²), had significantly larger root collar diameters and total dry weights at time of planting than seedlings grown in a smaller volume container at a high plant density. Stem volume production in the field was greater on seedlings from larger volume containers grown at low densities.     

Influence of initial age and size on the field performance of <Emphasis Type="Italic">Larix olgensis</Emphasis> seedlings

Quality of seedlings is important for the success of plantations. The field performance of five stock types of Olga Bay larch (Larix olgensis Henry) seedlings three seasons after planting was evaluated. High survival rates were achieved for all five types of planting stock in the first-year growing season when weeds were controlled. In the second and third-year growing seasons, significant differences were observed in survival rates among different stocktypes. The 1 + 1 type of Olga Bay larch seedling demonstrated better survival than 1 + 0 type of seedlings. 1 + 1 seedlings with diameter larger than 5.0 mm as well as 1 + 0 seedlings with diameter larger than 4.5 mm were suitable for reforestation. The 1 + 1 stocktype with a root collar diameter between 6.0 and 7.5 mm was considered optimal for the establishment of fast-growing and high-yield plantations. The number of lateral roots > 1 cm in length was the best predictor of field performance, however, the number of first order lateral roots with diameter > 1 mm at the tap root junction (FOLR (D > 1 mm)) was more feasible and sufficiently reliable to predict the field performance of the deciduous conifers. The initial height and root collar diameter of seedlings showed a significant correlation with the field performance for both 1 + 1 and 1 + 0 seedlings in the first and second-year growing seasons and thus can be adopted as an indicator for predicting potential field performance of seedlings.     

马尾松切根、菌根化容器育苗效果的试验

对马尾松切根、菌根化容器育苗效果的试验表明：催芽切根的苗木的主根和高生长受到一定抑制，但地径生长、侧根发育及须根数量均有显著改善，并且避免了畸形根系的产生，从而提高了容器苗的规格质量；切根茵根化的苗木高、径生长和生物量积累均优于切根未接种菌根的苗木，幼苗造林成活串和幼林生长发育状况也明显比对照要好。     

Mechanical shock during transportation: effects on seedling performance

A study was carried out to monitor shocks to seedling planting stock during transport from nursery to the planting site in normal commercial reforestation operations. Size and exact time of mechanical shocks were measured by a recorder placed inside seedling boxes. Seedling shipments by refrigerated semi-trailer, 5-ton truck, pickup truck, small trailer and all-terrain vehicles were monitored in Alberta and British Columbia. Number of shocks, peak acceleration and average drop height were tabulated for travel on both paved and gravel roads.Twenty-two trials involving seven species were established at nurseries and field locations covering several ecological zones in both provinces. Frozen-stored, cool-stored, and freshly lifted seedlings were used in the trials. Seedlings were given two mechanical stress treatments by dropping them 30 times from 0.5-m and 30 times from 1.0-m, respectively. Control seedlings were not dropped. Treatments were applied to nursery-trial seedlings not exposed to normal handling and transport, and to field-trial seedlings after transport to the planting site. Six root growth potential tests were made with treated and control seedlings in conjunction with the nursery trials.Seedling survival and volume growth were recorded for two growing seasons and the results statistically analysed.     

Why seedlings survive: influence of plant attributes

Seedling survival and successful forest restoration involves many silvicultural practices. One important aspect of a successful forest restoration program is planting quality seedlings with high survival capability. Thus the nursery needs to create seedlings with plant attributes that allow for the best chance of success once a seedling is field planted. Since the mid-twentieth century, research foresters have critically examined plant attributes that confer improved seedling survival to field site conditions. This review describes the value of commonly measured seedling quality material (i.e. shoot height, stem diameter, root mass, shoot to root ratio, drought resistance, mineral nutrient status) and performance (i.e. freezing tolerance and root growth) plant attributes defined as important in answering the question of why seedlings survive after planting. Desirable levels of these plant attributes can increase the speed with which seedlings overcome planting stress, become ‘coupled’ to the forest restoration site, thereby ensuring successful seedling establishment. Although planting seedlings with these desirable plant attributes does not guarantee high survival rates; planting seedlings with desirable plant attributes increases chances for survival after field planting.     

Performance of loblolly pine (Pinus taeda L.) seedlings and micropropagated plantlets on an east Texas site: I. Above- and belowground growth

East Texas contains the western extent of the natural range of loblolly pine (Pinus taeda L.) and, therefore, many planted seedlings there experience water deficit sometimes leading to plantation failure. One solution may be to regenerate with clonally propagated drought-hardy planting stock. The objective of this research was to compare the field performance of loblolly pine seedlings and plantlets of diverse genetic origin, produced via micropropagation technology.Two adjacent sites were established (Site I in 1993 and Site II in 1994) with trees produced from four genetic families: Liberty (LIB) and Montgomery (MON) Counties from southeast Texas, and Fayette (FAY) and Bastrop (BAS) Counties from the “Lost Pines” in Central Texas. Height, groundline diameter (GLD), leaf area, survival, root/shoot ratio, and root system architecture were measured throughout the 1994 and 1995 growing seasons. In addition, height and diameter at breast height on Site II were measured at the end of 1999 and 2000 growing seasons.Height and GLD growth for seedlings was significantly greater than for plantlets on both sites. However, mean relative growth rates for height were greater for plantlets during the first growing season, but comparable thereafter. Survival for all treatments was >85% on Site I and >90% on Site II at the end of the 1995 growing season. Survival was significantly different, but by a negligible margin, between families and stock types on Site II at the end of the 1995 growing season, and by a margin of 7% (89% for seedlings vs. 82% for plantlets) at the end of the 2000 growing season. Seedlings had greater leaf area growth than plantlets after two growing seasons. Root/shoot ratio was significantly greater for plantlets after two growing seasons, whereas their specific root length was significantly smaller than that of seedlings. This was attributed to root system architecture. Whereas plantlets produced thicker roots with less length per unit dry weight, seedlings produced more branching with thinner roots for similar dry weights.     

Morphological indicators of stock quality and field performance of red oak (Quercus rubra L.) seedlings underplanted in a central Ontario shelterwood

The value of initial stem diameter near the root collar, shoot length and number of first-order lateral roots (FOLR) as morphological indicators of stock quality and field performance was examined for bareroot (1+0, undercut) red oak (Quercus rubra L.) underplanted in a shelterwood in central Ontario. These three attributes were measured on more than 400 seedlings prior to planting, and their relationship with height and basal diameter growth two years after planting was determined using correlation and regression analysis. Initial diameter, shoot length and number of FOLR were positively and significantly correlated with second-year height and diameter. These relationships were strongest for diameter, but this variable explained less than 25% of the total variation in growth. Of the three indicators, diameter was also the best predictor of several physical characteristics of root systems two years after planting. Initial diameter was significantly correlated with root volume, root area and lateral root, taproot and total root dry mass. Weaker relationships existed between initial shoot length and number of FOLR and second-year root system features. Stem diameter two years after planting was more strongly related to root volume, area and dry mass than was initial diameter, the probable result of adjustment in root-shoot balance of planting stock to the shelterwood environment.     

红椆播种苗移栽容器育苗技术研究

为提高红椆苗木质量和造林成活率,对红椆2年生直播苗和2年生撒播苗移栽容器苗苗木质量进行对比试验,同时采用不同规格容器和遮荫处理对1年生撒播苗移栽到容器后苗木的成活率和生长量进行比较试验。结果表明:容器育苗可显著提高红椆苗苗高、地径、主根长、地上部分干重、地下部分干重;容器规格对移栽后苗木成活率影响不显著,但对苗木生长有显著影响;采用80%遮阳网遮荫,容器苗成活率较高,苗木高生长也显著增加,但苗木地径生长与60%遮阳网遮荫处理的苗木差异不显著。     

花榈木不同播种育苗方式效果研究

试验采用营养袋播种育苗和田间苗床播种育苗2种方式进行花榈木苗木生长量的比较研究,结果表明,2种不同育苗方式的种子的发芽率、高径生长量、根系生长量差异极显著;营养袋有利提高花榈木种子的发芽率及苗木的高径生长和主根生长,但侧根生长较差;为提高移栽成活率,在生产上提倡采用营养袋育苗。     

Initial seedling morphological characteristics and field performance of two Sudanian savanna species in relation to nursery production period and watering regimes

It has become apparent that some interventions are required to aid the regeneration of woody species in the Sudanian savanna. Direct seeding has been ineffective, thus planting high quality seedlings may be a viable alternative. In this study, we examined the stock quality of two valuable Sudanian savanna species, Acacia macrostachya and Pterocarpus erinaceus. Different nursery production periods were tested as well as the species’ field performance under well-watered and stressed conditions. The results showed that older seedlings (9-month) were morphologically distinct from younger ones (3-month), particularly in the case of P. erinaceus. Eighteen months after planting out, survival and growth of seedlings were not affected by initial seedling size; this was the result of the high root to shoot ratio of seedlings in all age groups at the time of planting. Seedling mortality as high as 30% was observed and attributed to both drought stress and other factors such as herbivory. Regression analyses revealed that initial shoot height was a poor predictor of field performance for both species, but initial root collar diameter accounted for 25% of the variation in diameter of P. erinaceus in the field. We conclude that initial seedling size does not affect survival and growth in the field provided that all sizes of seedling have a high root to shoot ratio at the time of planting. The prediction of field performance could be improved by developing a model that incorporates a wide range of root collar diameter.     

Effect of planting stocktype and cultivation treatment on the establishment of Norway spruce on cutaway peatlands

In order to determine the effect of stocktype and cultivation treatment on the field performance (survival and growth) and physiological status of Picea abies in cutaway peatlands, small bare-root, large bare-root and containerised seedlings were planted in a deep ploughed and a control site. Survival after 2 years was good across all treatment (>90%) except for the large bare-root seedlings growing in the control site (84%). For all the morphological characteristics assessed in this study, there was no significant interaction between stocktype and cultivation treatment indicating that the growth response to site cultivation was not stocktype dependent. After two growing seasons, all Norway spruce seedlings performed better in the deep ploughed site and displayed also better nutritional and physiological status. Regardless of cultivation treatment, mean height, diameter and volume increment were significantly smaller for the large bare-root seedlings while the small bare-root seedlings displayed the greatest growth rates. In order to promote early height growth in container and small bare-root stock, large diameter is important. Other initial characteristics such as foliar nitrogen content may also have a strong influence on first year field performance. The physiological status of the seedlings during the first year after outplanting was assessed using chlorophyll fluorescence (CF) measurements. CF measurements detected a higher level of stress for the large-bare root stock (low Fv/Fm). On the other hand, small bare-root stock displayed highest maximum potential photochemical activity which corresponded to greatest growth rates. Container seedlings demonstrated higher capacity for photosynthetic electron transport during the first five months after planting suggesting that they recovered from planting stress quicker and optimised better light interception and utilization than bare-root stock. It can be concluded that intensive management systems including deployment of best-adapted stocktype and site cultivation can be used to enhance early height growth of Norway spruce on cutaway peatlands.     

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.     

不同类型和规格木荷苗木造林对比试验

利用福建省南平樟湖国有林场不同类型和规格的木荷苗木造林对比试验林,系统研究苗木类型与规格对造林成活率、保存率、幼林生长及叉干率的影响。结果表明:轻基质营养袋苗、大田裸根Ⅰ级苗和大田裸根Ⅱ级苗3种类型和规格的木荷苗木造林成效差异显著,其中采用轻基质营养袋苗造林可取得95.56%的造林保存率,且叉干率只有3.47%;造林后木荷1年生幼苗地径、树高和冠幅的平均值分别达到了1.63cm、107.10cm和56.43cm;造林后2年生,其地径、树高和冠幅的平均值分别达到了2.61cm、224.90cm和113.07cm,均优于大田裸根Ⅱ级苗和大田裸根Ⅰ级苗的造林成效,说明采用木荷轻基质营养袋苗造林可显著提高造林成活率和生长量,降低林木叉干率,全面提升造林成效。     

Root wrenching and lifting date of slash pine: Effects on morphology,survival, and growth

Slash pine (Pinus elliottii Engelm.) seedlings were subjected to three wrenching treatments: One root wrenching in early August; Three root wrenchings in early August, September, and October; and No wrenchings. Seedlings were then lifted on five dates between November and February based on the number of chilling hours accumulated. All wrenched seedlings had reduced shoot dry weight, smaller shoot-root ratio, and smaller stem diameter and height. These morphological differences translated into improved survival as well as increased diameter and height growth when measured one and two years after planting. Only seedlings wrenched three times demonstrated improved root fibrosity. Furthermore, only multiple wrenched stock showed greater resistance to drying imposed prior to planting. At the time of lifting, seedlings lifted latest had greater stem diameter, increased root dry weight and number of root tips, and improved shoot-root ratio. However, no survival differences were detected across lifts, and those seedlings lifted earliest demonstrated the best height and diameter growth.This paper is Journal Series No. R00695 of the Institute of Food and Agricultural Sciences, University of Florida, Gainesville 32611.     

Field performance of containerized black spruce seedlings with root systems damaged by freezing or pruning

Roots of 2-year-old black spruce seedlings (Picea mariana [Mill.] B.S.P.) were exposed to freezing temperatures to destroy 20, 40, 60, and 80% of the root systems. For comparison, other root systems were pruned to eliminate the same proportions of roots. Treated and control seedlings were planted in spring 1992 at Forêt Montmorency (the Université Laval forest research station, 50 km north of Quebec City). From 1992 to 1995, survival, shoot height and stem diameter were measured. Mortality mainly occurred in 1993, the year after planting; pruned seedlings showed practically no mortality while seedlings with 20, 40, 60, and 80% of their root systems affected by frost showed mortality rates of 0, 6, 17, and 24%, respectively. Shoot height and stem diameter decreased with increasing root damage when compared to controls. After three years on the planting site, shoot height was reduced by 2, 8, 11, and 18% while stem diameter was reduced by 4, 21, 25, and 24% for 20, 40, 60, and 80% frost damage, respectively. For pruned seedlings, shoot height was increased by 3% at 20% damage and was decreased by 1, 3, and 13% for 40, 60, and 80% root damage while stem diameter was reduced by 1, 4, 8, 19% for 20, 40, 60, and 80% respectively. Use of damaged seedlings on the planting sites should be limited in order to reduce the cost of replacement planting.     

Effect of water stress conditioning on morphology,physiology and field performance of Pinus halepensis Mill. seedlings

Five-month-old Pinus halepensis Mill. seedlings were subjected to 4 irrigation treatments for 8 weeks. After the treatments, morphological and physiologicalattributes assessed included height, diameter, dry weight, water relations parameters, and determination of N, P, K, soluble carbohydrates, and starch concentrations. The remaining seedlings were field planted. Survival and height growth were recorded forfour growing seasons after planting. The mostsignificant effect of irrigation was onmorphology. Increased irrigation lead toseedlings with significantly higher height,root collar diameter and shoot and rootbiomass. Starch and soluble carbohydrateconcentrations were also affected byirrigation. However, parameters derived frompressure-volume curves were not significantlydifferent among treatments, nor were N, P, andK concentrations. There were no differencesamong treatments for survival in the field,which was highly related to summer rainfall. Incomparison, absolute and relative heightgrowth showed some significant but minordifferences among treatments.