Height Increment Of Seedlings Research Articles

Influence of watering periods and organic fertilizer on seedling growth and development of two species of oak tree; Quercus aegilops and Quercus libani

Raisin drought seasons and temperature at last decades are the maximum prominent threats for the world. It is predictable that there will be several regional influences by worldwide climate alteration, especially on freshwater reserves, energy, biodiversity, agriculture, human health, forest trees and sea level. This experiment was aimed for estimate the influence of watering periods and organic fertilizers on seedling growth and development of the two oak species; Q. aegilops L. and Q. libani L.. The trial was conducted under three levels of water periods (once every 4 days, 8 days and once every12 days) and with three organic fertilizer levels (control, 25 gm, and 50 gm per pot) were used two times when seedlings age was 3 and 6 months. The result showed that the organic fertilizer with watering periods had a significant effect on seedling growth and physiological properties. The results indicated that the highest value Leaf number and seedling height increment (5.22 plant-1, and 2.20 cm, respectively) were both recorded from (4 days watering plant-1). The highest values of leaf area (10.95cm2) were recorded from the (zero or control organic fertilizer plant-1) in Q. aegilops. The highest value moistures content was (63.52 %) were recorded from interaction between (8 days of watering*25gm organic fertilizer). Therefore, it is concluded that Q. aegilops and Q. libani seedlings could success under organic fertilizer and watering periods, especially seedlings were showed best performance under well water availability. Keywords: Watering periods, Organic fertilizer, Q. aegilops, Q. libani, Morphological, and physiological pareameters &nbsp

Comparison of pulp sludge compost effectivity of three different decomposers to the growth of geronggang (Cratoxylon arborescens) seedlings

Pulp residue from liquid waste processing is suitable for compost materials, except for its high CN ratio so it needs composting to reduce the CN ratio. Geronggang is a native peat swamp species suitable for peat rehabilitation. The study aims to test pulp sludge compost quality enriched with three different decomposers to the growth of geronggang ( Cratoxylum arborescens ) seedlings. The sludge composting was incubated for a month using three species of decomposers, i.e., Phanerochaete chrysosporium (C); Penicillium citrinum and Penicillium oxalicum (CO); P. chrysosporium, P. citrinum and P. oxalicum (CCO). The compost is weighed and placed around the seedling's roots area with varies dosages equal to 2, 4, 6, 8, 10, 12, 14, and 16 ton ha -1 . The height and diameter of the seedlings were recorded for six months. Data was examined using ANOVA followed with DMRT at a 5% significance. The sludge compost in this study has CN ratio, Total N (%), P 2 O 5 (%) and K 2 O (%) about 40.22-44.5; 1.04-1.11; 1.05-1.13; 1.05-1.13, respectively. Statistically, the height increment of seedlings after the sludge compost application enriched with the CO was different from the CCO. However, the seedling's height rise was not statistically different at the dosages variation treatment. The raise of seedlings diameter after CO treatment at a dosage equal to 6 and 12 ton ha -1 was significantly different to the CCO at a dosage equal to 12 ton ha -1 . However, the rise of seedling's diameter was not significantly different at decomposers' variation treatment. The future study can be aimed to gain compost that meets the national standard.

Influence of mycorrhizal preparation on seedling growth and Armillaria infestation

The influence of three types of treatment on seedling survival percentage, growth and Armillaria infestation of Fagus sylvatica L. (FAGUS), Abies alba Mill. (ABIES) and Picea abies (L.) H. Karst. (PICEA) seedlings were tested in this study: (i) inoculation with the Ectovit<sup>®</sup> preparation containing ectomycorrhizal fungi (INOCUL), (ii) Ectovit<sup>®</sup> preparation + Conavit<sup>®</sup> fertilizer (INOCUL + FERTILIZ) and (iii) the untreated group (CONTROL). The selected sample contained 100 seedlings per each tree species and treatment type (900 seedlings in total). Besides that, 18 months after planting, 10 living seedlings per each species and treatment (90 seedlings in total) were sampled to evaluate root dry mass and Armillaria infestation. The data were statistically evaluated by frequency analysis, analysis of variance and Kruskal-Wallis test. The overall seedling survival percentage was very low, probably due to extreme drought and high temperatures, with significantly lower results for the ABIES INOCUL + FERTILIZ and PICEA INOCUL + FERTILIZ groups. All tested growth characteristics (seedling height increment, root collar diameter increment, seedling shoot dry weight, root dry mass) were significantly higher in PICEA seedlings. Root collar diameter increment showed significant differences within each species and inconsistent results. Armillaria was detected only in the PICEA CONTROL group as rhizomorphs identified as A. ostoyae. The results suggest that the artificial mycorrhizal preparation can be an efficient method of preventing Armillaria infestation, especially in spruce seedlings.

Effect of Mulching and/or Watering on Soil Moisture for Growth and Survival of the Transplanted Tree Seedlings in Dry Period

Dry mulch, as soil moisture conservation techniques, is seldom practiced for growth and survival of transplanted tree seedlings in dry period in Eritrea. Field experiment was conducted at Halhale, Eritrea with Dry Hyparrhenia rufa, as a mulch, on a flat basin for growth and survival of seedlings of Grevillea robusta and Acacia polyacantha subspecies Campylacantha by involving four management practices: 1) mulching and watering basins (MW); 2) no-mulching but watering basins (NMW); 3) mulching but no-watering basins (MNW); 4) no-mulching and no-watering basins (NMNW). The experimental design was CRD with three replications. MW and NMW were watered 180 litters (20 litters/month) but MNW and NMNW were not watered at all. Parameters such as soil moisture content of the basin, early growth performance of seedling and survival rate of the seedlings were studied. The result indicated that there were statistically significant differences (p 0.05) among the treatment for soil moisture content and early growth performance of the seedlings. The average volumetric water content (VWC%) on 0 - 20 cm soil depth at the end of dry period of MW, NMW, MNW, and NMNW were 10.08%, 7.7%, 6.3% and 3.9% respectively. Mean height increment of seedlings of G. robusta of MW (100 cm), NMW (83.3 cm), MNW (31.5 cm) and NMNW (9 cm) were recorded, while the mean height increments of seedlings of A. polyacantha subsp. Campylacantha of MW (48 cm), NMW (25 cm), MNW (4.5 cm) and NMNW (3 cm) were recorded. The mean survival rate of G. robusta was 91.8% of which the highest (100%) survival rate was recorded under MW, NMW and MNW, but the lowest (66.7%) was recorded by NMNW. All seedlings of A. polyacanth subsp. Campylacantha were survived, irrespective of the treatments. The study concluded that soil moisture content, early growth performance of seedlings, and survival rate of transplanted tree seedling was improved by application of mulch.

Effects of lead on growth, osmotic adjustment, antioxidant activity and photosynthetic responses in Phoebe chekiangensis seedlings

Experiments were conducted on 1-year Phoebe chekiangensis seedlings treated by different concentration (0, 300, 600, 900, 1200 mg/L) of Pb (NO3)2. Sixty days later, determination was implemented on seedling growth, physiological and photosynthetic parameters. The results showed that the lower concentration treated could promote the growth of the seedlings. But with the increase of concentration of lead, P. chekiangensis seedling height increment, ground diameter growth, whole biomass, total root surface area, root volume, total root length and root activity decreased, while root-shoot ratio present a rising trend. With the increase of concentration of Pb(NO3)2 solution, the membrane permeability and MDA content of P. chekiangensis seedlings showed a trend of rise after the first reduce; the protein content and chlorophyll content presented a trend of decrease after the first increase; while the POD, SOD and CAT activity increased firstly but decreased afterwards; the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate were all increase at first then decrease, which indicated that protection enzyme activity and membrane was damaged thus the growth of P. chekiangensis seedlings was inhibited.

Effect of buds manually removal and their damage by large pine weevil (Hylobius abietis L.) on Scots pine seedlings in Siversky Donets river valley

Large pine weevil (Hylobius abietis L.) damages different organs of Scots pine (Pinus sylvestris L.) seedlings in unclosed plantations, including foliage, buds, stem bark and roots. Simulated damage of respective organs, particularly debudding is one of the ways to evaluate qualitative and quantitative influence of such damage on tree condition.
 The aim of research was to evaluate the dependence of Scots pine seedlings mortality and height increment on artificial and large pine weevil caused bud damage.
 The growth of apical shoots of Scots pine seedlings was registered since the beginning of May to the end of June. Development of new shoots in seedlings with manually bud removal or large pine weevil damage started in beginning of May and continued in July.
 Mortality of Scots pine seedlings with 20% of lateral buds damaged did not differ from that in undamaged plants. The seedlings with apical and lateral buds manually removed as well as with apical and over 70% lateral buds damaged by large pine weevil have died in the year of treatment or damage. The seedlings with apical buds damaged as well as with apical and over 50% lateral buds damaged died in the 4th year after damage.
 Removal or damage up to 50% lateral buds did not affect the growth of Scots pine seedlings. Height increment of seedlings with apical buds manually removed or damaged by large pine weevil did not differ significantly in May and June of the year of treatment or damage. In July the height increment was statistically greater in the variant with manually removal of apical bud.
 Previously suggested scale of Scots pine seedlings bud damage satisfactory reflects the score of large pine weevil injuriousness.
 We can suggest that height increment in the next years after bud damage does not depend on damage way and intensity but mainly on ecological conditions.

Growth and Physiological Mechanism of Phoebe chekiangensis Seedlings in Response to Lead Stress

Experiments were conducted on 1-year Phoebe chekiangensis seedlings treated by different concentration (0, 300, 600, 900, 1200 mg/L) of Pb (NO3)2. Sixty days later, determination was implemented on seedling growth, physiological and photosynthetic parameters. The results showed that the lower concentration treated could promote the growth of the seedlings. But with the increase of concentration of lead, P. chekiangensis seedling height increment, ground diameter growth, whole biomass, total root surface area, root volume, total root length and root activity decreased, while root-shoot ratio present a rising trend. With the increase of concentration of Pb(NO3)2 solution, the membrane permeability and MDA content of P. chekiangensis seedlings showed a trend of rise after the first reduce; the protein content and chlorophyll content presented a trend of decrease after the first increase; while the POD, SOD and CAT activity increased firstly but decreased afterwards; the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate were all increase at first then decrease, which indicated that protection enzyme activity and membrane was damaged thus the growth of P. chekiangensis seedlings was inhibited.

Efekat primene mikrobiološkog preparata na dinamiku visinski porasta jednogodišnjih sadnica crnog oraha (Juglans nigra L.)

Trend of organic production of plants that are used for human nutrition binds that when using nutrition preparations which represent significant factor in production of high quality planting material for different purposes microbiological preparations have to be included as well. The effect of the microbiological preparation Bactofil® B 10 on height growth tempo of black walnut seedlings during vegetation period is a subject of research of this paper. Comparative analysis of height increment of seedlings grown in soil treated with this preparation and height increment of control, nontreated seedlings shows the justification of direct application of Bactofil in mass production of high quality planting material of black walnut.

Effect of ethephon on hardening of Pachystroma longifolium seedlings

Immediately after planting, tree seedlings face adverse environmental and biotic stresses that must be overcome to ensure survival and to yield a desirable growth. Hardening practices in the nursery may help improve seedling stress resistance through reduction of aboveground plant tissues and increased root volume and biomass. We conducted an assay to quantify changes in the morphogenesis following application of ethephon on seedlings of Pachystroma longifolium (Ness) I. M. Johnst.during hardening. The results showed no effect of the ethephon treatments on the number of leaves but a reduction of up to 50% in seedling height increment, and an increase in stem diameter increment of up to 44% with the 600 mg L-1 ethephon treatment, which consequently altered seedling Dickson Quality Index. Our results indicate that ethephon may help to promote desired morphological changes that occur during seedling hardening in nurseries.

Effects of soil preparation on the success of artificial beech regeneration in areas infested by weeds on Juzni Kucaj Mountain, Serbia

This paper presents the results of research on the effects of prior soil preparation on artificial regeneration by mountain beech forests (Fagenion moesiacae montanum) in weed-covered plots on Južni Kučaj Mountain. Research was conducted on the survival of one-year-old containerized seedlings in weed-covered sites where different auxiliary measures had been carried out, i.e. the following methods of soil preparation: 1) control area, with no preparation; 2) living forest ground cover (blackberry) removed; 3) living forest ground cover removed and soil tilled to a depth of 10 cm; 4) only the soil tilled. The above treatments were performed with five repetitions each for further statistical processing. Analysis of variance showed no statistically significant difference at level p <0.05 in initial seedling height, so that this did not considerably affect the influence of the different soil preparations on seedling growth. Half of the planted seedlings were treated with the chemical “Zeba” in order to establish and monitor its effects and needs for its use. The product has a sponge effect underground, meaning that it can absorb and retain moisture in the soil to be used later by the plants. The analysis carried out showed that only in certain elements were there statistically significant differences in one-year-old seedling height increment (annual shoot length).

Uticaj primene različitih preparata ishrane na visinski prirast sadnica oraha (Juglans regia L.)

Providing of quality planting material which takes root well after planting, resistant to diseases, pests, stress (drought, extreme temperature, etc.) and grows well in cultures is one of the strategic and preferential tasks of modern forestry. Walnut is a fruit tree important as a founder of various varieties and hybrids, and as a rootstock for high-yielding varieties. It is also of great importance because of high nutritional value of fruit and high quality of stem. For that reason this species has to be introduced into the existing ecosystem and used for afforestation of different habitats. The paper presents results of research on the effect of the controlled decomposing fertilizer Osmocote Exact®, mineral NPK fertilizer Florin 2 and microbiological preparation Bactofil® B 10 on height increment of walnut seedlings. Data analysis was performed by relevant procedures using statistical software packages (SPSS Statistics 17.0). Comparative analysis of height increment of seedlings treated with these preparations and height increment of untreated seedlings, as well as a simple way of application of these preparations by adding them to the substrate, will show the justification of direct application of these types of fertilizers and microbiological preparation in mass production of high quality planting material.

Survival and growth of outplanted seedlingsof selected tree species on the High Tatra Mts. windthrow area after the first growing season

Bareroot and containerized seedlings (seedling type) of Norway spruce, Scots pine, European larch, European beech, and sycamore maple were outplanted in autumn 2008 and in spring 2009. Roots of a half of the seedlings were dipped into the commercial fungal product Ectovit prior to spring outplanting. Fifty seedlings were planted for each tree species and seedling type in each of 3 treatments (Autumn, Spring, Spring+Ectovit) and 3 replications (4,500 seedlings in total). Eighty-one per cent of containerized and 75% of bareroot seedlings (most &amp;ndash; 89% of bareroot spruce, least &amp;ndash; 59% of bareroot pine seedlings) survived after the first growing season. Planting time and Ectovit did not have a marked effect on survival, with the exception of the lower survival of containerized beech and spruce in autumn than in spring. The most extensive damage caused by game and mechanical weed control was found out in both broadleaves; most of the dry leading shoots occurred in beech. Besides beech, higher annual height increment of seedlings was observed in autumn than in spring planting time. Effect of Ectovit on seedling growth was not obvious. &amp;nbsp;

A review of the study of Oinonen (1956) on ants on rocks and their contribution to forest regeneration in Southern Finland

The classical and still valid study of Oinonen (1956) on the species distribution and nesting habits of ants on rocks and their contribution to forest regeneration and tree growth on rocks was reviewed. Oinonen searched ant colonies in 103 sample plots situated on rocks in southern Finland. The plots were classified into three categories according to their vegetation succession stage. The locations of origin, ages, heights and height increment of seedlings were determined. The results indicated that the number of ant species decreased from sites with >50% lichen cover to sites with >50% moss cover and to sites with <50% lichen cover. Lasius flavus was the most common species (5.14 nests per 100 m2), followed by Lasius niger (0.72), Myrmica lobicornis (0.57), Formica fusca (0.38) and Myrmica scabrinodis (0.36). Ant nests were favourable sites for tree establishment, growth and survival. The height growth of 3–14-year-old seedlings averaged 39% higher in ant nests than elsewhere. Ants form favourable microsites for seedlings by collecting organic material and fine mineral soil in their mounds, and thus significantly contribute to forest regeneration on rocks with thin soil cover. The role of ants in postfire forest regeneration on mineral soils was also discussed.

Conservation through utilization: a case study of the Vulnerable Abies guatemalensis in Guatemala

Conservation through utilization is a controversial strategy that deserves more attention from researchers and practitioners. This case study focuses on Abies guatemalensis, a Vulnerable Mesoamerican conifer that is illegally used for timber, shingles, charcoal and Christmas tree production. Conservation of the remnant populations would preserve some unique montane forests, with concomitant benefits for local water supplies and prevention of landslides. As a conservation tool we suggest establishment of additional A. guatemalensis Christmas tree plantations. These could generate income for local farmers and help halt poaching from natural stands. So far, 51 such plantations have been established in Guatemala but practical knowledge of cultivation is limited and production dominated by a few large plantations. Seed for Christmas tree plantations needs to be carefully selected because there are marked differences among populations in germination, seedling height increment and greenery quality. Insect pests such as the balsam twig aphid Mindarus sp. could limit cultivation. A market study showed that c. 23% of households in the major Guatemalan cities buy A. guatemalensis Christmas trees but currently only 2.3% of these are plantation-grown. The prices of illegal and certified Christmas trees are, however, converging, making plantation trees more competitive. Because of the market characteristics and the potential for establishment of plantations, we are moderately optimistic that the conservation through utilization strategy may be successful for this species in Guatemala.

Regeneration dynamics in an uneven-aged virgin Norway spruce forest in northern Sweden

The study was conducted at Kirjesålandet, a multistorey primeval Norway spruce [Picea abies (L.) Karst.] forest in northern Sweden. The objectives were: (1) to establish whether the presence of dead trees was associated with higher seedling density or growth; (2) to establish whether the influence of overstorey standing volume on height increment of seedlings differed between small and large seedlings; (3) to determine the time needed for seedlings to reach 1.3 m height; and (4) to estimate levels of recruitment, mortality and ingrowth into the tree layer, with equations using the relation between the height distribution and height increment of the seedling population. Seedlings (0.1–1.3 m height) and trees (diameter at breast height ≥5.0 cm) were measured on 46 circular plots. Presence of dead trees did not affect seedling density or growth. Height increment of small seedlings (0.1–0.5 m height) was unaffected by overstorey standing volume (range 13—333 m3 ha−1), whereas height increment of large seedlings (0.5–1.3 m height) decreased with increasing overstorey standing volume. Time to grow through the size interval 0.1–1.3 m was estimated as 58 years using height increment, and 50 years using analysis of annual rings. Seedling recruitment, annual mortality and ingrowth into the tree layer were estimated as 46 seedlings ha−1 year−1, 1.8% year−1 and 13 stems ha−1 year−1, respectively.

Growth And Survival of Seedlings and Saplings in the Logged - Over Forest, Kintap, South Kalimantan

A study on demography, growth and survival of seedlings and saplings was conducted in the Hutan Kintap concenssion, South Kalimantan, Indonesia. The aim of the study was to monitor pattern of growth of seedlings and saplings among different types of logged - over forest, including the newly logged - forest, older logged - over forests (treated and untreated), and un-logged-forest patches. The study began in 1991, and nineteen of 0.25 ha plots were set up in a total of six blocks designated as consecutively A, B, C, D, E and F. Block A was a newly logged forest and had five plots, and Block B - D were in forest which had been logged in 1979. Block B (five plots) had received no silvicultural treatment, while Block C (five plots) and D (one plot) had been lightly thinned after felling and further Block C received a further thinning treatment Block E (one plot) had been heavily thinned, and Block F (2 plots) was an un-logged control. The density of seedling varied within the study sites, and averaged from 47,000 ha" to 121,000 ha·1• The mean height increment of seedlings varied among block ranging from 2.9 cm year' to 10.5 cm year". Block A had the highest general mean increment of 10.5 cm year", followed in decreasing order by Block C of 5.4 and Block F, 4.5 cm year". Growth of seedling in Block B was low, even lower than the growth in the un-logged Block F. The difference of the increment among Block A, B, C and F however was not significant. The liberation treatment in Block C significantly resulted in a higher (p &lt;0 . 0 1 ) increment (5.4 cm year") than that in the untreated Block B (2.9 cm year"). Seedling mortality ranged from 16 to 37 % year", and declined with height class. The mortality of seedlings might be related among other factors to the humidity and density of seedlings per-unit area. The density of sapling ranged from 6,800 ha" to 7,700 ha" and they had diameter growth of 0.8 mm year" to 2.2 mm year", and height growth of 12.6 cm year" to 21.8 cm year"1. The difference in the diameter increment among block r \ , B, C and F was not significant. The average sapling height increment varied (but not significantly so) among Block, ranging from 12.6 cm year" in Block A to 21.8 cm year" in Block C. Mortality of sapling was relatively low in all block. Higher mortality in the un-logged forest Block I' and in the untreated Block B might due to the low degree of canopy opening.

Influence of physiological condition at the time of lifting on the cold storage tolerance and field performance of ash and sycamore

Summary The physiological condition of ash (Fraxinus excelsior L.) and sycamore (Acer pseudoplatanus L.) seedlings sampled from the same nursery in Ireland was evaluated at periodic intervals from September to May, and after cold (1oC) storage from the time of lifting until May, in 1997/98. Shoot water potential (WP), root electrolyte leakage (REL) and root growth potential (RGP) were assessed. In addition, the survival and height increment of seedlings established in a field trial in tandem with the physiology work was determined after one growing season. Shoot WP of freshly lifted ash seedlings, but not sycamore, decreased to low values in the winter. REL and RGP values were generally also lower in ash than in sycamore on most lift dates. Furthermore, sycamore became more highly active earlier in the year (February/March) than ash (April/May). The effect of cold storage on physiological responses was not consistent. The survival of seedlings in the field was close to 100 per cent regardless of treatment. The height increment of freshly lifted sycamore was best for stock planted from September to early March, whereas ash grew best when planted early (October‐November) or late (after February) in the lifting season, although differences between most lift dates were small in ash. Under operational forestry conditions, planting during some of these periods may not be advisable due to the potential effect of handling damage. Cold-stored ash planted in May after cold storage performed well for seedlings lifted to the store from December to February, but the physiologically more active sycamore performed best when stored from February.

Effect of Stand Structure and Density on Development of Natural Regeneration in Two Picea abies Stands in Sweden

Previous studies have indicated that the effect of overstorey density on height increment and mortality of seedlings and saplings is affected by the vertical structure of the overstorey. To test this, 28 plots, including four control plots, were studied at two sites, in northern and central Sweden. Norway spruce dominated all plots. The overstorey was thinned from "above", i.e. harvesting mainly large-diameter trees and maintaining a multilayered structure, or from "below", i.e. harvesting mainly smaller trees and creating a shelterwood. Three different densities were created for each structure, in the range 20-140 m3 ha-1 at the northern site, and 40-200 m3 ha-1 at the southern site. Seven years after treatment, seedling (0.1 m5 heightB 0.5 m) and sapling (0.5 m5 heightB 2.0 m) height increment tended to decrease with increasing overstorey density at both sites for plots thinned from below, but the effect was not statistically significant. Cutting regime had a significant effect on seedling height increment year 5 after treatment at the northern site, and cutting regimen and overstorey density combined had a significant effect on saplings in years 5 and 6 after treatment at the southern site. Annual mortality rates were 2-7% for seedlings and 0-4% for saplings. Ingrowth past 10 cm in height during the 7 yrs after treatment was less than 20 seedlings per hectare and year at the northern site, and less than three at the southern site.

Responses of tree seedlings to the removal of Chromolaena odorata Linn. in a degraded forest in Ghana

Chromolaena odorata is a dominant plant species in degraded forest areas in Ghana. This species forms a very dense canopy. Although tree seedlings have been observed growing under the canopy of this species, they have scarcely been seen growing through the canopy of Chromolaena odorata. To study the response of tree seedlings to the removal of Chromolaena odorata, 108 plots were established 20 m apart in a degraded dry semi-deciduous forest in Ghana. Chromolaena odorata was removed from 50% of the plots to release tree seedlings and left the other half intact. Seedling height, the number of leaves per seedling, and seedling mortality were assessed in both released and unreleased plots immediately after the release treatment (June 1998) and again three months later (September 1998). It was found that the seedling height increment and the increase in number of leaves per seedling were three times greater in released plots than the unreleased plots three months after the release treatment. Twenty eight tree species were found in the plots and 89% of the species had higher height growth after the release treatment. Similarly, 93% of the tree species had more new leaves in released plots than in the unreleased plots. Sixty four percent of the species suffered various levels of mortality in the unreleased plots, but all the seedlings of all the species survived in the released plots. The results suggest that there is a great potential to restore the degraded area back to forest using natural seedlings by removing Chromolaena odorata, the competing vegetation.

Adaptive significance of intermittent shoot growth in Douglas-fir seedlings.

We tested the hypothesis that intermittent (lammas) shoot growth in Douglas-fir (Pseudotsuga menziesii var menziesii (Mirb.) Franco) seedlings from dry regions of southwest Oregon is adaptively significant. Seedlings from open-pollinated families (160 total) from two inland (dry) and two coastal (wet) sources were grown under either well-watered or intermittent drought conditions (temporary drought followed by rewatering) for two growing seasons. In the first growing season, the results supported the hypothesis: the frequency of a second flush was genetically controlled (although weakly, h(f) (2) </= 0.34); more seedlings, on average, from inland families than from coastal families displayed a second flush; and seedlings from inland families were more responsive to the intermittent drought regime in terms of increased frequency of a second flush (relative to the frequency in the well-watered regime). During the second growing season, the intermittent drought treatment did not promote intermittent shoot growth, although inland and coastal families had different patterns of shoot growth that reflected adaptations to soil water availability. We conclude that inland families have adapted to dry summers and short growing seasons by relying predominantly on predetermined growth for seedling height increment after the first growing season. In response to wetter and generally longer growing seasons, however, coastal families have developed a less regulated pattern of shoot extension and rely more on free growth.