NZJFS - Volume 28 (1998)
Book review - Microfibril angle in woodRidoutt, B.
Review of: "Microfibril angle in wood", The Proceedings of the IAWA/IUFRO International Workshop on the "Signficance of Microfibril Angle to Wood Quality" edited by B. G. Butterfield.
High air velocity and relative humidity reduce development of kiln brown stain in Pinus radiata.Kreber, B., Haslett, A. N., & Norris, M. G. C.
Kiln drying of Pinus radiata D. Don sapwood causes the development of a brown subsurface coloration, commonly called kiln brown stain. Planing exposes the stain and this can spoil one of the appealing features of P. radiata—its light colour.
Kiln schedule modifications—for example, drying with low kiln temperatures—reduced the frequency and intensity of kiln brown stain but increased drying times. An attempt was made to shorten drying times and produce an acceptable colour in the dried lumber by using high air velocities as well as high relative kiln humidities in conjunction with medium kiln temperatures. Depth (below the wood surface) and thickness of kiln brown stain were also determined in the dried P. radiata.
Using stepped kiln schedules with either high air velocities or high relative humidity reduced development of kiln brown stain compared to accelerated conventional temperature 90/60°C drying, but considerably longer drying times were needed. Furthermore, stain formed about 0.5 mm underneath the surface with a thickness of up to 2 mm. The best method for countering the effect of kiln brown stain would be to plane 2 mm off the surface of kiln-dried lumber during remanufacturing.
Site index curves for Pinus nigra grown in the South Island high country, New Zealand.Kimberley, M. O., & Ledgard, N. J.
Height/age equations were derived for Pinus nigra Arn. subsp, laricio (Poiret) Maire (Corsican pine) growing in the South Island high country of New Zealand. These equations can be used to predict height growth, including site index (dominant height at age 40), when provided with a measure of height and age. The equations were derived from dominant height data obtained from 30 stands covering the range of rainfall zones typical of the region. Because of the species' monocyclic growth pattern it was possible to measure annual heights for each tree. A variety of sigmoidal height/age curves were tested, with the Hossfeld and Chapman-Richards equations performing best. Anamorphic and polymorphic forms of these models were tested using cross-validation. The simpler anamorphic forms of the equations gave better results than the more complex polymorphic forms. The two methods of fitting the equations that were compared—one treating site index as a fixed effect, the other as a random effect—gave almost identical results. The shape parameters of the growth curves were not related to altitude or rainfall, but site index was positively correlated with rainfall, thus allowing formulation of a predictive equation.
Growth efficiency of Pinus radiata stand elements: Implications for stand growth modelling strategiesO'Hara, K. L., Knowles, R. L., Dean, M., West, G. G. & McInnes, I.
Individual tree growth rates and growth efficiencies were assessed for different stand elements from Pinus radiata D. Don pruning trials in New Zealand. Growth rates were higher for non-crop elements, but crop elements had significantly higher rates of efficiency (basal area increment per unit of crown length or per unit of sapwood crosssectional area at crown base (as a representation of leaf area)). Sapwood basal area was more strongly related to tree basal area increment than to measured crown length, indicating it may be a better measure of crown size in growth models and in measures of crown growth efficiency. Weak correlations between plot basal area increment and average crown length per tree indicated that the primary effect of crown length per hectare on basal area increment was through its relationship to stocking density rather than crown length. Inclusion of a growth efficiency variable in the EARLY growth model resulted in some minor improvements to the model for productive farm sites, but not for less-productive pumice forest sites. Future modifications which may enhance the EARLY model might include adding calliper cross-sectional area at crown base as a production variable to represent leaf area.
Nursery stock and field fertiliser application affect early performance of Pinus radiata on a phosphorus-deficient site in Northland.South, D. B., & Skinner, M. F.
An experiment was established on a phosphorus-deficient site to determine the effects of nursery stock type and fertiliser application (after transplanting) on early growth and survival of 1/0 Pinus radiata D.Don seedlings. Three fertiliser treatments were compared: (1) slit-applied diammonium phosphate (DAP; 18 kg N and 20 kg P/ha) at 80 g/tree, (2) Christmas Is. 'A' grade rock phosphate (RP; 16% P) broadcast at 50 kg P/ha, and (3) partially acidulated rock phosphate (PARR; 17% P) broadcast at 50 kg P/ha. Tree stocks given DAP grew best over the first 2 years, but lost the early height advantage in the following 2-year period when stock on PARR- or RP-treated soil outgrew them by c. 0.5 m. After 4 years in the field, the trees with fertiliser were on average 1.8 to 2 times taller than stock without. Container stock maintained its initial 4 cm or so height advantage over bare-root stock for the 4 years of the trial, but cost three times as much to produce. Seedling survival was not affected by fertiliser application after planting, but survival was slightly lower for bare-root seedlings that were initially deficient in nitrogen. Inoculating the soil with freeze-dried spores of Rhizopogon spp. had no beneficial effects on seedling performance.
Nitrogen and phosphorus mineralisation in Pinus radiata harvest residue samples from a coastal sand.Parfitt, R. L., Ross, D. J., & Salt, G. J.
Although nitrogen mineralisation after harvest of Pinus radiata D. Don plantation forests has been studied previously, little work has addressed nitrogen and phosphorus mineralisation in stockpiles of harvest residues on coastal sands. We examined, in the laboratory, the mineralisation of nitrogen and phosphorus in dead needles, L/FH materials, and mineral soil (0—10 cm depth) from windrows, and in raked soil, and compared results with those from an adjacent standing forest. Microbial carbon, nitrogen, and phosphorus were also determined. Samples were taken 12 and 32 months after harvest.
Mineralisation of nitrogen was greatest in the dead needles, and was greater in windrow L and FH materials than in corresponding forest samples. The proportion in the nitrate-nitrogen form increased with time after harvest, and became susceptible to leaching loss. Microbial carbon, nitrogen, and phosphorus values were initially highest in the windrow dead needles and L material. These data were consistent with previous results suggesting that net nitrification is likely in P. radiata needles with carbon/nitrogen ratios <40, whereas net immobilisation of nitrogen is likely if the ratio is >55. Extractable phosphorus was comparatively high, and carbon/phosphorus ratios comparatively low, in the windrow L and FH materials, which suggests that net mineralisation of phosphorus would readily occur in these materials. Net mineralisation of phosphorus in mineral soil was higher in the windrow and raked soil than in the standing forest. These data are also consistent with previous data suggesting that net mineralisation of phosphorus occurs when the carbon/phosphorus ratio for the FH horizon is <550. Since the nitrogen in the windrows is readily mineralised, and some losses by leaching occur, management practices could be initiated to allow for greater retention of nutrients after harvest on coastal sands.
Quarantine risk posed to forestry by full container loads, and efficiency of FCL door inspections.Bulman, L. S.
A survey of 9001 full-container-load (FCL) consignments imported into Auckland (a 10% sample, based on perceived risk) was undertaken to examine the incidence of interceptions of material that may affect trees and wood products, and to compare the rate of interceptions with those found in an earlier study of part-container-load (LCL) cargo (100% inspection). Interceptions in FCL cargo (4.2%) were less than half those in LCL cargo (9.1%). Bark was found in 3.5% of the consignments, insect damage in 1.5%, insects in 0.7%, and fungi in 0.3%. Stone and slate, sawn timber, and general goods had the highest rate of contamination, along with any cargo from Africa and North Asia. Cargo packed in crates, skids, and cases contained more prohibited material than packages or cargo packed in cartons or bales. A log-linear model was used to predict contamination rates for various combinations of origin, goods, and packaging. Nearly half the combinations had a 2%, or less, probability of carrying contaminated material.
A further study of 501 "high risk" FCLs was carried out by examining the cargo as it was unpacked at its final destination, after the containers had been inspected via the open door of the FCL on the wharf. Contamination by insects or fungi, or the presence of bark, was recorded. Of the 501 containers examined, 191 (38.1 %) contained insects, insect damage, bark, fungi, or some combination of the four. Door inspections identified 115 (23%) contaminated containers, and during the follow-up inspections, 76 (15%) containers previously cleared during the door inspections were found to be contaminated. The majority (81%) of contaminants found during the door inspections were of such significance that treatment was recommended. Only 30% of contaminated containers found during the follow-up inspections warranted treatment. Quarantine interceptions were most common for stone and slate, machinery, and general goods packed in crates and cases. The study showed that door inspections are generally efficient for detecting significant contaminants in imported cargo, but some contaminated containers slip through quarantine undetected.
Wind-caused disturbance of a red/silver beech forest: Ten years on.Hosking, G., & Hutcheson, J.
A 10-year study of the effect of wind damage on the health of residual Nothofagus fusca (Hook, f.) Oerst. / N. menziesii (Hook, f.) Oerst. (red/silver beech) forest showed tree mortality continued throughout the period in severely damaged forest. Forest with less than 30% canopy loss was much less affected by continued deterioration and showed little difference from undamaged forest at the end of the period. The two species showed different trends in mortality over time; the mortality rate of red beech levelled off after 7 years while that of silver beech was still increasing after 10 years. Platypus spp. pinhole borers were not a primary cause of tree mortality, attack being largely confined to trees that were already unhealthy. Blowdown debris harboured only a single generation of pinhole borers, decay being too advanced to support further broods.
Infection of wounds in young Eucalyptus nitens by ascospores and conidia of Endothia gyrosa.Yuan, Z. Q., & Mohammed, C.
A shadehouse-based technique to inoculate seedling stems with ascospores and conidia was developed. Seventeen-month-old seedlings from three different localities of the Toorongo provenance of Eucalyptus nitens (Deane et Maiden) Maiden were inoculated with the ascospores, conidia, and mycelium of each of three Endothia gyrosa (Schw.: Fr.) Fr. isolates. The lesions produced from the inoculation of the different forms of each isolate were compared. Both ascospores and conidia of E. gyrosa were able to initiate and establish infections through wounds, and results suggest that both are able to play a role in dissemination of the pathogen.
Environmental preferences of Eucalyptus globulus stem cuttings in one nursery.Wilson, P. J.
The initial survival of Eucalyptus globulus Labill, ssp. globulus stem cuttings, under intermittent mist in a glasshouse, was increased by: shade on clear days, the amount depending on season; increasing the wettability of cuttings; periodic water stress of mother plants; and, in winter, by supplementary lighting of cuttings and mother plants. In cuttings from greenhouse-grown plants, survival and the rooting ability of survivors did not vary overall with season, but short-term environmental variation (over 1 week) was significant. Rooting was sensitive to fertiliser in the medium of both mother plants and cuttings, and to the level of shading of cuttings. In summer, outdoor environments were satisfactory for mother plants and favourable for cuttings.
Developing clones from Eucalyptus globulus and hybrid seedlings by stem cuttings propagation.Wilson, P. J.
Clones were developed by stem cuttings propagation from 1700 potted seedlings of Eucalyptus globulus Labill, ssp. globulus and various E. globulus interspecific hybrids. Propagation traits were evaluated and the 10% of clones that were easiest to propagate were planted in clonal field trials. Ease of propagation varied widely between clones, families, and hybrids, although (overall) the hybrids were not dissimilar from the pure species. Rooting ability also varied widely between occasions within a clone, largely owing to management factors, increasing the error in clonal rankings and leading to under-estimates of clonal mean rooting ability. Over all harvests of cuttings, rooting was higher than 70% of survivors in 3-4% of all E. globulus and hybrid clones.
Clonal selection, propagation, and maintenance of juvenility of Chinese fir, and afforestation with monoclonal blocks.Zhou, T., Zhou, J., & Shelbourne, C. J. A.
Techniques of clonal selection, establishment of hedged stool-beds, and cutting propagation have been developed for Cunninghamia lanceolata (Lamb.) Hook. (Chinese fir) in Zhejiang Province, China, and clonal forestry has been implemented in a local programme based at Kaihua County Forest Farm. Cutting propagation and the maintenance of juvenility, and plantation performance of 102 clones in single-row plots and multi-tree blocks, have been studied over different years and sites.
Hedged stool-beds with a density of 6.3 stools/m2 can provide 40-50 shoots per stool in the third year, when techniques for stimulating shoots have been used. Cuttings taken in the spring have an average rooting success of 90%, height at age 1 year of 35 cm, and basal diameter of 6 mm at a density of 52.5 plants/m2, at which point they are ready for transplanting to field sites.
Needle cuttings were developed to increase multiplication rates of superior clones. This involves cutting off needles (with a little xylem) from coppice shoots near the root collar, and setting during the period from January to March. Rooting was 85%, the height at age 8 years was 10 m, and diameter at breast height (dbh) was 12.4 cm, a similar performance to that of shoot cuttings. Stands developed from seedlings of elite families and cuttings of the third propagation cycle had a similar growth rate. The performance of successive propagations of cuttings showed no significant decline in rooting and growth over 11 propagation cycles. Hedged stool-beds can prevent trees from ageing and keep shoots at a juvenile stage.
If the test materials are classified into four levels of improvement—"elite clones", "average of best 23 clones", "elite families", and "first-generation seed orchard offspring"—gains in single-tree-volume (STV) at age 9 years were respectively 67%, 24%, and 15% over the seed orchard offspring. Of all selection materials, the best were crosses between selected parents from different provenances. The first screening of clones was carried out at 4-5 years after planting, the second at 6-7 years, and the final screening at 8-12 years (9.5—11.5 m height). Selection of 15 clones out of 102 resulted in a gain of 86% in STV over the Napo, Guangxi, check. Planting single-clone blocks of a genetically-diverse range of clones can increase yields per unit area. Up to the present, 2700 ha have been planted on Kaihua Forest Farm and increases in yield of over 50% are expected.
Corrigendum - International gene pool experiments in Pinus radiata: patterns of genotype-site interactionBurdon, R. D., Hong, S. O., Shelbourne, C. J. A., Johnson, I. G., Butcher, T. B., Boomsma, D. B., Verryn, S. D., Cameron, J. N., & Appleton, R.
Corrigendum to NZJFS 27 (2) 101-125: International gene pool experiments in Pinus radiata: patterns of genotype-site interaction.
The paper which this Corrigendum refers to is available here: International gene pool experiments in Pinus radiata: patterns of genotype-site interaction
Book Review - Sampling plantation eucalypts for wood and fibre propertiesDonaldson, L.
Review of "Sampling plantation eucalypts for wood and fibre properties" by G. M. Downes, et al.
Development of a database, and its use to quantify incidence of defects in random-width Pinus radiata boards.Gazo, R., Mitchell, S., & Beauregard, R.
A database was developed containing 392 digitised boards, volume 17.10 m3 (7245 board feet), from 10 different clones of New Zealand Pinus radiata D. Don. Thirty-one percent of the boards came from pruned logs, and the remainder from unpruned logs. Nine defect categories were identified, the most frequent defects in boards from pruned logs being bark pockets and blemishes and the largest-sized defects on average being areas containing needle flecks. The most frequent defects in boards from unpruned logs were knots, and they were also the largest-sized defects in these boards.
The database can interface with all common simulation and modelling programs. It can be used to establish basic relationships between New Zealand P. radiata tree characteristics and board characteristics for prediction and planning purposes.
Conceptual method for comparing yield from curve-sawn and straight-sawn logs.Todoroki, C. L., & Ronnqvist, E. M.
When straight sawing technology is used, yields from irregularly-shaped (swept) logs are lower than those from comparable unswept logs. The greater the sweep, the greater the anticipated yield loss. Developments in curve-sawing technology may improve yields from swept logs; volume increases of 3%-20%, and board length increases exceeding 20% have been suggested. The destructive nature of the sawing process precludes direct verification of such claims.
A method has been developed to allow simulation of conceptual curve-sawing using a straight-sawing simulation system. Curve-fitting and data transformation are used to remodel a swept log as its "straightened" counterpart. This "log metamorphosis" was applied to a sample of 40 log models constructed from measurements of actual logs and selected to cover a range in size, shape, and quality. Sawing simulations were performed before and after log metamorphosis in order to compare straight- and curve-sawn yield. Results were variable, but increases in estimated recoveries fell within the assumed ranges reported for actual curve-sawing.
Loss of organic matter and carbon during slash burns in New Zealand exotic forests.Robertson, K.
The quantity of carbon lost to the atmosphere through volatilisation during burning of Pinus radiata D. Don and Pinus contorta Loudon forest logging slash was estimated from measurements made at four P. radiata sites and one P. contorta site in New Zealand. Pre- and post-burn fuel mass and carbon content were assessed at each site. On average 271 C/ha, or 62% of carbon present before burning (excluding that contained in stumps, roots, and mineral soil), was lost to the atmosphere as a result of slash burns at the four P. radiata sites. At the P. contorta site 33 tC/ha, or48% of carbon present before burning (excluding that contained in stumps, roots, and mineral soil), was lost to the atmosphere as a result of slash burning. Duff (F and H horizons), litter (L horizon), and sound woody material exceeding 7 cm in diameter were the components that contributed most to this loss. Total carbon loss in New Zealand due to burning of plantation forest logging slash was estimated to be 10 300 tonnes/year (s.e. = 1800) for P. radiata and 1600 tonnes/year (s.e. = 1160) for P. contorta.
Relationships between carbon loss from individual sites and the specific codes and indices of the Canadian Fire Weather Index System were examined. The best predictor of carbon loss was the Fire Weather Index itself. The development of a comprehensive system for modelling carbon losses from slash burns will require more information to develop a larger data set.
Modelling surface airflow for forest and rural fire danger rating: Comparisons between actual observations and predicted values.Moore, J. R., Fogarty, L. G., Suarez, J. C., & Gardiner, B. A.
The performance of three airflow models (Flowstar, MSFD-PC, and MS-Micro/3) was compared as a means of providing wind speed and wind direction data for use in the assessment of forest and rural fire danger. At Cowal Peninsula, Scotland, and the Manawatu Gorge, New Zealand, six simulations were performed with each model, using data for incident winds from the westerly quarter and incorporating effects of complex terrain. Model performance was similar for both study areas. The mean wind speed prediction error for the best-performing model (MS-Micro/3) was approximately 30%. Without simulation, prediction errors for average wind speed were 67% at Cowal Peninsula and 50% at Manawatu Gorge. Root mean square errors for wind direction prediction by models averaged 86° at Cowal Peninsula and 26° at Manawatu Gorge. With the exception of MS-Micro/3 output for the Manawatu Gorge area, wind direction simulations at both sites produced unacceptable results.
Three independent data sets were used to examine the influence of wind speed prediction errors on fire danger rating assessment. Error magnitudes associated with use of airflow modelling of single point source data altered the number of days allocated to Very High and Extreme fire danger classes, differences being much greater for areas with a severe fire climate. The Jackson-Hunt linear microscale models tested can provide wind speed information which will improve the accuracy of fire danger rating.
Evaluation of diameter distribution as a criterion for selecting crop trees in a pulpwood regime.James, R. N., & Hong, S. O.
An attempt was made to create a crop of plantation-grown Pinus radiata D.Don with more uniform diameter dimensions by selecting residual crop trees at age 8 from codominants with diameters close to the stand mean ("uniformity" thinning). A crop selected at age 7 by the conventional "from below" method was used for comparison. In both crops stocking rate was reduced from 2500 to 500 stems/ha to simulate a pulpwood thinning regime. The diameter range was reduced by uniformity thinning to the point where stands carried almost the same basal areas despite the difference in age of 1 year. After uniformity thinning, growth in basal area was slower for the first 3 years; it then increased to equal that of the conventionally thinned plots. By age 28 there was no significant difference in diameter distribution of crop trees selected by either method. It is unlikely that the final distribution of stem diameters in plantation-grown P. radiata can be altered for more than a few years by thinning to a restricted diameter range.
Branch development in Pinus radiata - Model outline and data collection.Grace, J. C., Blundell, W., & Pont, D.
The location of branches attached to the tree stem and the dimensions of the initial part of these branches which become encased within the stem are major determinants of timber quality. The branching characteristics of Pinus radiata D. Don were summarised and this information was used to define the structure of a branch model. The data necessary to define the mathematical form of these functions were obtained by destructive sampling of selected trees.
Pinus radiata growth responses to pruning, thinning, and nitrogen fertiliser in Kaingaroa forest.West, G. G.
Growth responses of Pinus radiata D.Don to pruning, thinning, and fertiliser treatments in a factorial design were measured over a 19-year period at two Kaingaroa Forest sites (Goudies, site index 30 m; Matea, site index 25 m). As single-factor treatments:
• Pruning — (selective green-crown pruning without thinning) resulted in a considerable loss in basal area growth;
• Thinning — Trees that were thinned-only responded with increased diameter growth;
• Fertiliser — The application of nitrogenous fertiliser (at 200 kg N/ha) to trees that remained unthinned (at 2700-3000 stems/ha) gave no significant improvement in basal area growth.
For combined treatments, when nitrogen fertiliser was applied to trees that were also thinned, a moderate basal area response resulted. For trees that were pruned and thinned, there was evidence that nitrogen fertiliser assisted with growth recovery from green crown pruning. The response to nitrogen fertiliser applied at first thinning (age 5-6 years) appeared to be similar to the response achieved at second thinning (age 9-11 years). Where the fertiliser was applied at both first and second thinnings the response was very small—a result which cannot be explained. By tree age 24 the response to nitrogen fertiliser was inconsistent and statistically non-significant.
Height growth in this study was little affected by pruning or thinning treatments and unaffected by the application of nitrogen fertiliser.
Generally, thinning increased mean branch diameters in subsequent pruning lifts by 0.4 cm, and where nitrogen fertiliser was also applied the increase was 0.6 cm. When combined with stem diameter responses these treatments have generally increased the diameter over pruned stubs (DOS) by 1-2 cm. For these reasons it would be advantageous to apply nitrogen fertiliser after all pruning lifts are complete.
Analysis of these trials up to age 24 years has indicated that variation between replicates increased with time and that this trend should be considered when trial designs are developed. The analysis also confirmed that single trials are of little value because of the influence of local site factors. A trial series located on a range of site types is recommended for the testing of silvicultural and fertiliser treatments.
In situ measurements of soil mineral-nitrogen fluxes in hoop pine plantations of subtropical Australia.Bubb, K. A., Xu, Z. H., Simpson, J. A., & Saffigna, P. G.
The dynamics of nitrogen (N) mineralisation, plant uptake of nitrogen, and leaching in the 0-10 cm soil depth were studied in hoop pine (Araucana cunninghamii Ait. ex D.Don) plantations aged 0,3,10,14, and 62 years with in situ incubation cores. Although ammonium-nitrogen was the dominant form of mineral-nitrogen in the 0-10 cm soil depth, nitrification was also an important process in hoop pine plantation soils, indicating that there might be a potential for nitrogen losses through leaching and denitrification, particularly at recently clearfelled sites.
The results indicated that most net nitrogen mineralisation and plant uptake of nitrogen occurred during the growing season between October and May. The amount of nitrogen mineralised from soils during this period ranged between 25 and 53 kg N/ha, representing, on average, 2% of the total nitrogen pool in the 0-10 cm soil depth. Net nitrogen mineralisation was significantly correlated with the soil organic carbon (C), total nitrogen, carbon/nitrogen ratio, and plantation age.
Soil solution phosphorus and Eucalyptus nitens roots in NP-treated microsites in highly phosphorus-fixing soil.Smethurst, P. J., & Wang, B.
Application of phosphorus (P) fertiliser to a microsite about 20 cm from each seedling soon after planting is a common practice in eucalypt plantations. To improve our understanding of phosphorus availability to Eucalyptus nitens (Deane et Maiden) Maiden plantations grown in a highly phosphorus-fixing soil, we determined the effects of spade-slit placement of fertiliser on (i) concentrations of phosphorus in soil solution (P1) around these microsites at 2,6,18, and 42 months after fertiliser application, and on (ii) fine root distribution at 18 months. Within 5 mm of the fertiliser, values of P1 decreased from at least 1000 mM soon after planting, to 100 mM at both 18 and 42 months. By 18 months, fertiliser application had increased P1 laterally up to 50 mm and vertically to a depth of 300 mm, despite the high phosphorus-fixing capacity of the soil (i.e., indicated by 472 mg P/g soil required to achieve 0.2 mg/ml in solution). Elevated phosphorus concentrations with depth were associated with high root-length densities (29 x 104 m/m3), but enhanced root growth may have also resulted from higher availability of nitrogen (N) in these fertile microsites. We concluded that microsite application of fertiliser was an effective way of maintaining high phosphorus availability to some root surfaces in this soil for at least 42 months after treatment. This method may alleviate the need for additional applications of phosphorus fertiliser later in the life of the crop.
Inbreeding in Pinus radiata. II: Time course of inbreeding depression and effect on growth curve.Wu, H. X., Matheson, A. C., & Spencer, D.
Changes in the effects of inbreeding on sectional area at breast height (1.3 m) each year from ages 1 to 13 were studied in Pinus radiata D.Don of five different inbreeding levels: F = 0, outcrosses; F = 0.125, resulting from half-sib matings; F = 0.25, resulting from full-sib matings; F = 0.5, resulting from selfing; and F = 0.75, resulting from two generations of selfing. The experimental material was derived from eight founder clones. Inbreeding had a significant impact on both cumulative and annual increments in sectional area from age 3, i.e., 2 years after outplanting when most trees had reached 1.3 m in height. At age 4, trees with the highest inbreeding levels (F = 0.5 and 0.75) had significantly less sectional area increment than those with lower inbreeding levels (F = 0, 0.125, 0.25). From age 11 on, trees had differentiated into three groups: outcrosses (F = 0) were best, sib matings (F = 0.125 and 0.25) were intermediate, and selfs (F = 0.5 and 0.75) were worst for cumulative and yearly increment of sectional area. An apparent bimodal time trend in inbreeding depression (ID) of annual increment was observed, being highest at the initial stage of stand development, disappearing at about the time of crown closure in the outcrossed population, and reappearing later. This bimodal trend was believed to be associated with the different times at which crown closure began for the different inbreeding levels, and indicates that inbreeding depression is a dynamic process associated with stage of stand development, spacing, and design of field layout.
In fitted Gompertz growth curves, all parameters were affected by inbreeding, including maximum growth rate, time to reach maximum growth rate, and the maximum sectional area achievable. There were significant differences in response to inbreeding among pedigrees.
Referee Index Volumes 1 to 25 (1971 to 1995)Editor: J.A. Griffith
Title Index Volumes 1 to 25 (1971 to 1995)Editor: J.A. Griffith
Title Index Volumes 1 to 25 (1971 to 1995)
Author Index Volumes 1 to 25 (1971 to 1995)Editor: J.A. Griffith
Author Index Volumes 1 to 25 (1971 to 1995)