Site preparation: Water relations and growth of newly planted jack pine and white spruce

Bareroot jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) were planted near Elliot Lake, Ontario, on a boreal reforestation site. Site preparation treatments were mixed, mineral and undisturbed (i.e., control) soil. Seedling water relations and growth were examined during the first field season. During the first 28 days after planting, jack pine base (i.e., predawn) and minimum xylem water potential readings were more negative in the control site preparation treatment. White spruce, during the first 10 days, in all site preparation treatments had base and minimum xylem water potential readings more negative than –1.7 MPa. By day 28 base xylem water potentials of white spruce had increased to approximately –1.0 MPa in all site preparation treatments. As the growing season progressed, white spruce minimum xylem water potential readings ceased exceeding the measured turgor loss point first in the mixed followed by the mineral and then control site preparation treatment. Jack pine minimum xylem water potential readings, in all site preparation treatments, almost never exceeded the measured turgor loss point. Water stress and stomatal optimization integrals, day 28 and 125, for both species showed least water stress and greater stomatal optimization in the mixed, mineral and control site preparation treatments, respectively. Both species had less new root growth in the field during the first 28 days after planting compared to seedlings grown for 28 days in a greenhouse for root growth capacity testing. Root growth at 28 days and both shoot and root development at the end of the growing season, were greatest to least in mixed, mineral, and control site preparation treatments, respectively.     

From planting to 26 years of age – actual growth and estimated volume scenarios for spruces and pines

The objective of this study was to compare the survival and volume of conifer stands at 26 years of age with their status at planting. Survival, growth and damage were studied in eight clear felled stands regenerated in 1972. Five of the areas were planted with Norway spruce (Picea abies (L.) Karst.) and three with Scots pine (Pinus sylvestris L.). The plantings were examined in 1972 and 1974. In 1974, the number of living undamaged planted seedlings was low (10–15%). However, the number of undamaged seedlings was supplemented by naturally regenerated conifer and birch seedlings. The total number of undamaged seedling in 1974 was equivalent to 20–30% of the number of seedlings planted. In 1998, the main species in three stands had changed from Norway spruce to Scots pine, and in one stand from Norway spruce to birches. Actual volume in 1998 for the stands was compared to stand volume generate according to five scenarios based on recommended and actual seedling number in 1972 and 1974. The actual volume was 64% of that expected if the recommended number of trees had been planted. Naturally regenerated Scots pine and Norway spruce increased stand density in 1998. The actual volume was 37% higher than the average volume in the surrounding county. On average, 36% of the trees were damaged. More than 50% of the total damage was caused by moose (Alces alces L.). For Scots pine, moose or other browsing animals damaged 30% of the trees. The results of this study indicate that the 1998 volume was higher than expected, considering the low number of undamaged seedlings in 1974. This was mainly due to the large amount of naturally regenerated plants. In addition, the results indicate that the volume could have been higher if the initial conditions had been better. Despite the low number of undamaged seedlings in 1974, seven of the eight studied stands produced a higher volume than the average stand for the region. In practise, high numbers of seedlings should be planted on scarified areas. In most cases there will be a supply of naturally regenerated seedlings.     

Herbicides and planting date affect early performance of container-grown and bare-root loblolly pine seedlings in Alabama

The survival of bare-root and container-grown loblolly pine (Pinus taeda L.) seedlings exceeded 90% when outplanted in March at two sites in Lee County, Alabama. At both sites, soil moisture and seedling survival were greater in March than in May. A March herbicide application reduced weed biomass by 75–80% at both sites. At the moist site, herbicide application did not affect survival. However, at the drier site, a reduction in weed biomass increased both the percent soil moisture and the survival of May-planted bare-root seedlings. When soil moisture at planting time was less than 13% on a dry weight basis container-grown seedlings survived better than bare-root seedlings. At both sites, reduced weed competition resulted in greater seedling heights and diameters.Alabama Experiment Station Journal Series No. 9-85802.     

Pre‐ and post‐inoculation water stress affects Sphaeropsis sapinea canker length in Pinus halepensis seedlings

In order to assess the influence of water stress on the development of Sphaeropsis sapinea cankers in Pinus halepensis, the stems of 4‐ to 5‐year‐old potted seedlings were artificially inoculated with the fungus before and after being kept at controlled water regimes from April 1997 to March 1998. In the pre‐water‐stress inoculation experiment, the canker length, measured 5 months after inoculation (September 1997), was greater in seedlings predisposed to extreme water deficit (midday needle water potential between ?4.5 and ?5.5 MPa). In the post‐water‐stress inoculation experiment, the fungus was inoculated in April 1998, after irrigation had enabled the seedlings to resume normal needle water potential. In this case also, at 5 months after inoculation, longer cankers were visible in seedlings that had been subjected to extreme water deficit. These findings suggest that the occurrence of marked water stress, although apparently tolerated by Aleppo pine, can enhance the development of S. sapinea cankers in this species, regardless of whether the stress occurs before or after infection by the fungus.     

Five-year field comparison of naturally regenerated Pinus taeda L. to genetically improved container stock,with and without release

A field study compared genetically improved, container-grown loblolly pine (Pinus taeda L.) seedlings to naturally established loblolly seedlings on a cutover pine site in southern Arkansas, USA. Pines on 50% of all plots were released from woody and herbaceous competition within a 61 cm radius of each tree stem. Woody competition was controlled by hand cutting for 5 consecutive years and herbaceous competition was controlled with herbicides (sulfometuron methyl and glyphosate) for 4 consecutive years. Competition control increased 5-year survival by 21–23% for natural and planted seedlings, respectively, with no statistically significant difference between the two regeneration techniques. Five years after field establishment, planted pines averaged 85% more volume than naturally established pines. Nevertheless, greater volume gains (551–688%) were achieved within regeneration techniques, as a result of competition control, than were achieved between the two regeneration techniques.     

Why do large,nitrogen rich seedlings better resist stressful transplanting conditions? A physiological analysis in two functionally contrasting Mediterranean forest species

We analysed the physiological bases that explain why large and high nitrogen (N) concentration seedlings frequently have improved survival and growth relative to small seedlings in Mediterranean woodland plantations. Large seedlings of Aleppo pine (Pinus halepensis Mill.) and holm oak (Quercus ilex L.) with high N concentration (L+), and small seedlings with either high (S+) or low (S−) N concentration, were planted on two sites of different weed competition intensity that created contrasting stress conditions. Seedling survival, growth, gas exchange, N remobilization (N_R) and uptake (N_U), and water potential were assessed through the first growing season. Weeds reduced survival and growth, but seedling response to weed competition varied among phenotypes and between species. At the end of the first growing season, L+ Aleppo pine seedlings had higher survival than both small seedling types in presence of weeds but no differences were observed in absence of weeds. Mortality differences among phenotypes occurred in spring but not in summer. L+ Aleppo pines grew more than small Aleppo pines independently of weed competition. No holm oak seedling type survived in presence of weeds and no mortality differences among phenotypes where observed in absence of weeds, although L+ holm oak seedlings grew more than small seedlings. Mortality and growth differences in Aleppo pine were linked to marked physiological differences among phenotypes while physiological differences were small among holm oak phenotypes. L+ Aleppo pines had greater root growth, gas exchange, N_R, and N_U than small seedlings, irrespective of their N concentration. Seedling size in Aleppo pine had a greater role in the performance of transplanted seedlings than N concentration. The functional differences among oak phenotypes were small whereas they were large in pine seedlings, which led to smaller differences in transplanting performance in holm oak than in pine. This suggests that the nursery seedling quality improvement for planting in dry sites could depend on the species-specific phenotypic plasticity and functional strategy. Improved transplanting performance in large Aleppo pine seedlings relative to small seedlings was linked to greater gas exchange, root growth and N cycling.     

Planted conifer seedling growth under two soil thermal regimes in high-elevation forest openings in interior British Columbia

A field trial was conducted investigating the single season growth response of 1+0 313 PSB Engelmann spruce (Picea engelmannii Parry ex Engelm.) and lodgepole pine (Pinus contorta Dougl. ex Loud.) seedlings planted into two different soil thermal regimes at three high-elevation locations spanning 200 km in the Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone in the Cariboo Mountains of central British Columbia. Temperature treatments represented the extremes of soil temperature commonly found in high-elevation clear-cuts. A warm soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 18 to 25 °C at –10 cm) consisting of a bare mineral soil hummock (average dimensions of 100 cm × 100 cm × 40 cm) was contrasted with a cool soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 10 to 13 °C at –10 cm) comprised of organic forest floor overlying mineral soil. By the end of the growing season, seedlings of both species planted into the warm treatment generally exhibited greater root, stem, foliage, and total seedling biomass than cool treatment seedlings. Measurements of root growth at 30, 60, and 90 days after planting showed that total root number and total root length were consistently greater for warm treatment seedlings than for cool treatment seedlings. Root growth was greater from the bottom rather than from the side of the root plug for all seedlings. These results suggest that the effect of low soil temperatures on outplanted styroblock conifer seedlings is pronounced and may be limiting growth performance in high-elevation plantations in British Columbia. We recommend silvicultural treatments that secure natural regeneration, ensure that warmer microsites are always planted, and utilize seedling stocktypes able to make rapid lateral root growth into warmer surface organic horizons.     

Influence of water stress on the physiology and growth of red spruce seedlings

Two-year-old, container-grown red spruce (Picea rubens Sarg.) seedlings from a New Hampshire seed source were exposed to 10 or 11 drying cycles in which the seedlings were not watered until their midday (1400 h) xylem water potentials averaged -1.57 MPa. Control seedlings were kept well watered to maintain midday water potentials of about -0.73 MPa. After the final drying cycle, the water-stressed seedlings were rehydrated and osmotic potentials were determined by pressure-volume analysis. Gas exchange at ambient CO(2) concentration (338 ppm) and at an elevated CO(2) concentration (838 ppm) was measured on both groups of plants as they slowly dried down. No osmotic adjustment or photosynthetic acclimation occurred as a result of the water-stress treatment and both groups of seedlings maintained photosynthesis to water potentials as low as -3.0 MPa. Twenty-four hours after rehydration, the water-stressed seedlings had photosynthetic rates as high as the control seedlings. Estimated stomatal limitation to photosynthesis was approximately 30% down to water potentials of -1.4 MPa, but increased steadily as water potentials decreased further. At ambient CO(2) concentrations (338 ppm) and water potentials averaging -2.45 MPa, photosynthetic rates of water-stressed seedlings were 15% those of well-watered seedlings, whereas when the same water-stressed seedlings were measured in the presence of an elevated concentration of CO(2) (838 ppm) their photosynthetic rates were 73% those of well-watered seedlings measured at an ambient CO(2) concentration (338 ppm).     

Planting stress in newly planted jack pine and white spruce. 2. Changes in tissue water potential components

Water relations of bare-root jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) planted in a greenhouse and on a boreal cut-over site were examined during the first growing season. In field-planted trees, maximum stomatal conductances (g(wv)) were initially low (< 0.10 cm s(-1)). Base and minimum xylem pressure potentials (Psi(x(base)) and Psi(x(min))) were less than -1.5 and -1.7 MPa for jack pine and -2.0 and -2.6 MPa for white spruce, respectively. During the growing season, maximum g(wv) increased in both species to around 0.2 cm s(-1). Base and minimum xylem pressure potentials also increased in both species to around -0.5 and -1.0 MPa in jack pine and -1.0 and -1.5 MPa in white spruce, respectively. Minimum xylem pressure potentials in white spruce fell below the turgor loss point during the first half of the growing season. Osmotic potential at the turgor loss point Psi(pi(TLP)) decreased after field planting to around -2.7 and -2.3 MPa in jack pine and white spruce, respectively. In the greenhouse, minimum values of Psi(pi(TLP)) were -2.2 and -2.3 MPa in jack pine and white spruce, respectively. Maximum bulk modulus of elasticity was greater in white spruce and underwent greater seasonal change than in jack pine. Relative water content (RWC) at turgor loss ranged between 71 and 74% in jack pine and 80 and 87% in white spruce. Available turgor (T(avail)), defined as the integral of turgor over the range of RWC between Psi(x(base)) and xylem pressure potential at the turgor loss point, was similar in jack pine and white spruce just after field planting. For the rest of the growing season, however, T(avail) in jack pine was two to three times that in white spruce. Diurnal turgor (T(diurnal)), defined as the integral of turgor over the range of RWC between Psi(x(base)) and Psi(x(min)), as a percent of T(avail) was higher in field-planted white spruce than jack pine until the end of the season. Dynamics of tissue water potential components are discussed in relation to plantation establishment.     

Pine weevil (Hylobius abietis) damage to cuttings and seedlings of Norway spruce

Damage caused by pine weevil (Hylobius abietus L.) to planted seedlings and cuttings of Norway spruce (Picea abies (L.) Karst.) was studied at five clearcut sites in south-eastern Sweden. The main objective was to compare the two types of stock in terms of attack frequency and mortality due to pine weevil feeding. Cuttings and seedlings with the same initial stem-base diameter (4 mm) were compared. Two sites were harvested and scarified shortly before planting, two were harvested shortly before planting, but were not scarified, and one was harvested 2 years before and scarified the autumn before planting. The total mortality 5 years after planting was highest, greater than 90%, at the new, non-scarified sites, and lowest, 23%, at the old, scarified site. More than 90% of the mortality was caused by pine weevil feeding. Attack frequency and pine weevil induced mortality were significantly higher among seedlings than among cuttings. Mortality due to pine weevil damage was 4–43% higher in seedlings than in cuttings after the fifth year. Of the cuttings and seedlings that were attacked in the first year, a significantly higher frequency of the seedlings were girdled. The higher resistance of cuttings to pine weevil damage may partly explain the more rapid growth of cuttings reported in other studies. However, the causes of their higher resistance need to be further investigated. The thicker bark and needles on the stem base of the cuttings could be important in this respect.     

Frequencies and patterns of browsing by large herbivores on conifer seedlings

Browsing by large herbivores on planted and naturally regenerated conifer seedlings (Picea abies and Pinus sylvestris) was recorded in 104 clear‐cuts in east‐central Sweden during 1990 and in 47 clear‐cuts in 1991. The number of seedlings browsed and the browsing patterns were analysed in relation to seedling type. Browsing frequencies were also compared between forest stands with different site productivities and subjected to different management practices. The variation in the number of seedlings browsed in 1990 was explained mainly by seedling category. Among both planted and naturally regenerated seedlings, pine was browsed more than spruce. Two‐year‐old containerized seedlings of spruce was browsed more than 4‐yr‐old bare‐rooted spruce. In 1991, browsing was more equal among species and seedling types. Number of seedlings with their leader browsed and the amount of biomass left after browsing differed significantly between seedling types. Seedlings that had been browsed in 1990 experienced significantly higher browsing frequencies in 1991 when compared with unbrowsed seedlings. The effects of stand characteristics were not found to be significant.     

Importance of root growth in overcoming planting stress

Root growth is critical to the establishment of planted seedlings. Seedlings can undergo stress just after planting if root growth is not sufficient to couple the seedling to available soil water. Stress occurs when a newly planted seedling’s root system can not supply enough water to transpiring needles to maintain a proper water balance and ensure survival. Thus, a newly planted seedling’s ability to overcome planting stress is affected by its root system size and distribution, root–soil contact, and root hydraulic conductivity. This paper describes how factors of root growth and water status of newly planted seedlings are important in overcoming the phenomenon of planting stress which then allows a newly planted seedling to enter the establishment phase of development.     

Effect of nursery storage and site preparation techniques on field performance of high-elevation Pinus contorta seedlings

After five years of growth at high-elevations (∼3000 m) in Utah, container lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings survived well (80–95%) and grew to similar heights regardless of nursery storage method and site preparation technique. Seedlings received one of three storage treatments: (1) spring-sown in the nursery, overwintered in cooler storage and outplanted in July; (2) spring-sown, overwintered in freezer storage, and outplanted in July; or (3) winter-sown, no storage, and hot-planted in late August. We outplanted seedlings at two locations that were clearcut and had received two treatments of surface organic matter (coarse wood, logging slash, and forest floor) removal: surface organic matter (OM) piled with a bulldozer and burned or surface OM remaining in situ. Compared to adjacent uncut stands, both site preparation treatments increased total soil bulk density, but retaining surface OM in situ maintained soil OM, carbon, and nitrogen levels. After one growing season, seedlings planted where surface OM had been bulldozed were taller and had more biomass, although survival was similar (≥96%) across site preparation treatments. The height growth advantage disappeared after five growing seasons and although overall survival was good, survival was highest where site preparation involved removal of surface OM and freezer-stored seedlings were planted. Total non-structural carbohydrates tended to be higher in roots than in shoots and were also higher in hot-planted seedlings than in stored seedlings. Our results indicate that nursery and forest managers have several options for successful nursery production and outplanting of container lodgepole pine seedlings in the central Rocky Mountains. Using hot-planted seedlings allows for a faster turnaround time (from seed to plantable seedling) and maintaining surface OM may be a cost-effective alternative to dozer piling and burning.     

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.     

Reduction of frost heaving of Norway spruce and Scots pine seedlings by planting in mounds or in humus

This study was carried out in northern Sweden to determine the effects of frost heaving on the establishment of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings in relation to planting methods. For this purpose, one year old containerised seedlings were planted on two sites and on two dates: during the spring (early planting) and during the fall (late planting). In each case, two planting depths (normal and deep planting) and four planting sites (in mineral soil in the depressions, in the scalp/trench area, on the top of the mound and in the untreated humus layer) were used. On each site, 50 seedlings were planted for each treatment. Frost heaving was observed and measured during two years. The amount of heaving was highest in the hole and almost insignificant on the top of the mound and in the humus layer. Planting depth influenced the degree of heaving only for Scots pine planted in the hole and was not related to the planting time.     

Planting cost,survival, and growth one to three years after establishing loblolly pine seedlings with straight,deformed, or pruned taproots

To provide an objective approach for comparing various planting methods likely to differ in cost, seedling performance, and cost efficiency, loblolly pine (Pinus taeda L.) seedlings were dug-hole or slit planted with either straight, deformed, or pruned taproots, and planting rate (seconds per seedling) and three-year survival and growth of seedlings were measured. The per-hectare cost of dug-hole planting seedlings to ensure straight taproots ($273) was over five times that of slit planting seedlings with intentionally deformed or pruned taproots ($50). Although third-year pine survival did not differ significantly among treatments (74% to 87%), yield index was 58% higher for seedlings dug-hole planted with straight taproots (1152 dm³ stem volume/ha) versus that for seedlings slit planted with deformed or pruned taproots (730 dm³/ha). Third-year cost efficiency (yield index ÷ planting cost) of slit planted seedlings with deformed or pruned taproots (11.7 dm³/$) was over three times that of dug-hole planted seedlings with straight taproots (3.5 dm³/$). These short-term results suggest that the higher values of yield index resulting from straight-root planting do not justify its considerably greater cost.     

Field performance of Scots pine (Pinus sylvestris L.) seedlings planted in disc trenched or mounded sites over an extended planting season

Economic pressures have driven an ever-widening period during which foresters use machines to plant Scots pine (Pinus sylvestris L.) seedlings. In Fennoscandia, this period has recently stretched to the entire growing season. To evaluate the performance of seedlings planted during this extended period, three experiments were carried out in Central and Northern Finland over 2 years. One-year-old and current-year seedlings were planted in mounds or disc-trenched furrows when soil temperatures were >0°C. When 1-year-old seedlings grown for spring planting and overwintered outdoors were planted after mid-June, more needles browned and growth was reduced, possibly because seedlings were oversized with respect to planting density and the volume of growth media. When current-year seedlings sown in spring were planted from July to November, those planted in late September and October grew less in later years than those planted earlier, but survival was unaffected. No large differences in field performance were found with respect to whether seedlings were planted in mounds or disc-trenched furrows. In conclusion, Scots pine seedlings can be machine planted in mounds or furrows during May and early June (later in the North) and then continued from early August until late September, provided climatic conditions in late spring and early autumn are typical and similar to those experienced in Central Finland.     

Growth of graded sweetgum 3 years after root and shoot pruning

Nursery grown 1–0 bareroot sweetgum seedlings were lifted and graded into two diameter classes (12–16 and 4–8 mm) during the dormant season. Large and small grades were top and/or root pruned and then outplanted on two sites in the lower Coastal Plain of the southeastern United States. Seedling shoots were pruned to 50% of tree height, a 5 cm stump, or no pruning. Seedling roots were pruned to a 15 cm length or left unpruned. Site affected survival but not growth. Smaller, top pruned seedlings performed worse on one site, probably due to greater weed competition. Large seedlings increased survival and growth which increased 3 year average plot volumes by 89%. Top pruning stimulated height growth, but reduced diameter growth and decreased third year seedling volumes. Root pruning did not affect seedling growth. Diameter growth may better indicate treatment impact that height, which has been most commonly used in previous studies.     

Xylem cavitation and loss of hydraulic conductance in western hemlock following planting

Following planting, western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings experience water stress and declining xylem pressure potential (Psi(x)). Low Psi(x) can result in xylem cavitation and embolism formation, causing a decline in hydraulic conductance. This study focused on the relationship between Psi(x), xylem cavitation and transpiration (E) of newly planted seedlings. Leaf specific hydraulic conductance (k(AB)) declined from 0.56 to 0.09 mmol m(-2) s(-1) MPa(-1) over a 9-day period. Stomatal conductance (g(s)) declined from 143.5 to 39.15 mmol m(-2) s(-1) over the same period without an associated change in environmental conditions. A vulnerability profile indicated a 30% loss in hydraulic conductivity when seedlings experienced a Psi(x) between -2.5 and -3.0 MPa. A Psi(x) of -4.0 MPa led to a complete loss of conductivity. We conclude that following planting, western hemlock seedlings often experience Psi(x) values that are low enough to cause xylem cavitation and a decline in k(AB).     

Effects of planting time on pine weevil (Hylobius abietis) damage to Norway spruce seedlings

Feeding by pine weevil (Hylobius abietis L.) causes severe damage to newly planted conifer seedlings in most parts of Scandinavia. We investigated the effect of planting time and insecticide treatment on pine weevil damage and seedling growth. The main objective was to study if planting in early autumn on fresh clear-cuts would promote seedling establishment and reduce the amount of damage caused by pine weevil the following season. The experiment was conducted in southern Sweden and in south-eastern Norway with an identical experimental design at three sites in each country. On each site, Norway spruce seedlings with or without insecticide treatment were planted at four different planting times: August, September, November and May the following year. In Sweden, the proportion of untreated seedlings that were killed by pine weevils was reduced when seedlings were planted at the earliest time (August/September) compared to late planting in November, or May the following year. This pattern was not found in Norway. The average length of leading shoot, diameter growth and biomass were clearly benefited by planting in August in both countries. Insecticide treatment decreased the number of seedlings killed or severely damaged in both Norway and Sweden.