Poor Stem Form Research Articles

Interaction of site, spacing, weed control and fertiliser in Pinus radiata plantations in southeast New South Wales

ABSTRACT Two trials addressing soil preparation, weed control, fertiliser application and planting density were established on dry, high-elevation sites as part of a program to develop site-specific management. The sites differed in soils and the level of pasture improvement. The objectives included identifying treatment combinations that had greatest productivity and best stem and branch form, considering that poor stem form is an issue on pasture sites. The trials were assessed at 13 years of age. Volume production was high compared with a plantation established earlier on a native forest site, but it was not possible to determine whether this was a result of higher survival, higher nutrition, improved weed control or improved genetics. There was little difference in the effects of soil preparation treatments, and there was no effect at 13 years of the small early-fertiliser application. Weed control was important, with effects on volume production varying between sites and having a greater effect on the highly improved pasture site. Increasing stocking from 1000 stems ha−1 to 1500 stems ha−1 increased volume production by about 24% where weed control was applied. There were differences in stem and branch form between sites, and the highly improved pasture site had a higher level of multi-leaders, probably attributable to low boron. The study shows the value of small, standardised silvicultural trials in the development of site-specific management.

Modeling Self-Thinning Patterns in Loblolly Pine with Provenance and Family Effects

Abstract Size-density trajectories and self-thinning boundary lines were modeled for two diverse provenances of Pinus taeda L. and five open-pollinated families within each provenance. The data used come from a single site with replicated 64-tree block plots measured through age 25 years. The effects of provenance and family were tested using linear and nonlinear mixed-effects self-thinning models. The drought-hardy Lost Pines of Texas provenance displayed a greater predicted carrying capacity (almost 200 more trees per hectare at reference diameter 25.4 cm) and had a more abrupt approach to the self-thinning line than the widely planted Atlantic Coastal Plain provenance. However, the growth rate of the Lost Pines of Texas provenance was considerably slower and stem form was unacceptable for timber production. Families from the Atlantic Coastal Plain differed in their maximum stand density index predictions (from 1,118 to 1,282 trees per hectare at the reference diameter), suggesting there is an opportunity for artificial selection to change maximum stand density index in this breeding population of loblolly pine. A novel method for predicting the self-thinning boundary line using random effects inherent to the experimental design is presented and recommended for repeated measures data. Experimental design considerations for evaluating genetic differences in self-thinning are discussed. Study Implications Genetic improvement of growth rate in forest trees has resulted in large gains in plantation productivity, but the effect on carrying capacity has not been addressed. This study indicated that artificial selection on tolerance to competition in the widely planted Atlantic Coastal Plain provenance of loblolly pine can potentially increase harvest yield without sacrificing growth rate. The drought-hardy Lost Pines of Texas provenance displayed greater carrying capacity but had poor stem form and slow growth. The Lost Pines provenance may be attractive for aboveground carbon sequestration, since it sustained substantially more biomass because of greater maximum stand density and denser wood.

Genetic variation in resistance to Uromycladium acaciae fungus, growth, gummosis, and stem form in Acacia mearnsii populations

A new epidemic disease caused by the rust fungus Uromycladium acaciae emerged in 2013/2014 causing defoliation, branch, and stem deformations in plantations of Acacia mearnsii (black wattle) in South Africa. This study investigated the level of genetic resistance to the rust fungus Uromycladium acaciae in six progeny tests from two different trial series. A total of 269 open pollinated families of different levels of improvement, ranging from wild selections to fourth cycle generations were included in the study. Families originated from land race subpopulations of South Africa and from Australian provenances. Rust severity was assessed across all the trials at 6 months of age. In the rust screening trials, different measures of rust incidence were assessed at 6, 12, and 17 months, as well as tree height and mirid damage at 12 months. In the progeny trial series, tree height, stem defects, and gummosis were measured at 36 months. Results suggested that rust incidence is under moderate genetic control at the family level. The coefficient of additive genetic variation was large (59.4%) for the disease incidence. The family mean heritability for rust disease was $$ {h}_{fm}^2=0.48\pm 0.16 $$ in the progeny trial series, whereas it was $$ {h}_{fm}^2=0.33\pm 0.06 $$ in the rust screening trials. Among the rust assessment methods, 6-month rust incidence (yes/no) assessment produced higher heritability estimates. With some exceptions, Australian provenances from low altitude sites along the eastern coast of Victoria and the south east coast of New South Wales showed high tolerance to rust, better growth, low gummosis incidence but poor stem form. All the South African sources showed high rust susceptibility and had average or below average growth, gummosis incidence, and stem form. For rust disease improvement, the South African material should be avoided and the best existing Australian families should be used for further breeding. In addition, new seed sources from Australia should be infused to the breeding program in order to increase the genetic diversity while increasing genetic gain for the rust, gummosis, and growth.

Assignment testing reveals multiple introduced source populations including potential ash hybrids (Fraxinus excelsior × F. angustifolia) in Ireland

Large-scale reforestation programmes are a major source of unwarranted gene flow and can have profound consequences on local genetic diversity. Recently, ash has been introduced to Ireland from continental Europe to stock plantations but has often exhibited poor stem form. It was not known whether these trees were Fraxinus excelsior, Fraxinus angustifolia or interspecific hybrids that are known to occur in continental Europe. F. excelsior is the only native ash in Ireland, so the introduced populations represent a potential threat for the genetic diversity of native populations. We characterized the introduced trees within two plantations (Clonee and Kildalkey) using morphological characters and six microsatellite markers. Samples from continental Europe were included for comparison. Plantations exhibited higher genetic diversity than control populations because our data suggest they contain a mixture of several provenances. There was a small but significant differentiation between plantations and control populations (ФCT = 0.0211). Bayesian analysis to infer population structure and to assign introduced individuals to reference populations clearly demonstrated the presence of hybrid individuals within the plantations. The percentage of trees detected with potential hybrid origin ranged from 28 to 58 % depending on the plantation and the threshold data analysis level chosen. Most hybrids could be considered cryptic because there was a lack of intermediate morphology for hybrid individuals that mainly clustered with F. excelsior. The results indicated that the source of material at the two plantation sites differed. Management options to minimize the impact of these introduced populations are discussed.

Poor Stem Form as a Potential Limitation to Private Investment in Koa Plantation Forestry in Hawaii

Providing economic incentives to landholders is an effective way of promoting sustainable forest management, conservation and restoration. In Hawaii, the main native hardwood species with commercial value is Acacia koa (koa), but lack of successful examples of koa plantation forestry hinders private investment. Financial models, which have been offered to encourage investment, assume that a particular minimum volume of merchantable wood will be harvested at rotation age. No studies have been done to determine the appropriateness of the assumed volumes for koa plantations. Three 18- to 28-year-old koa plantations were studied to determine butt-log size, crown class and crop tree potential. Estimates of present and future merchantable sawtimber volume were made for each plantation. Results indicate that most existing plantation koa trees fork so close to the ground that they will produce little to no merchantable wood. Projected sawtimber yields from crop trees in these plantations at age 45 years are 10, 15 and 90 m 3 /ha, which are below the 135 m 3 /ha yield used in the most recent financial analysis of returns on investment in koa forestry. Relaxing the crop tree criteria gives higher volume yields, but two plantations still fall short of the assumed target yield by 43 and 52%.

Damage to foliage and stems caused by fungal pathogens in young eucalypt plantations in Zambia

Plantations consisting of non-native tree species were established on the Copperbelt of Zambia to supplement timber supply from natural forests and to meet the increasing demand of round wood and fuel wood for the copper mines. In early 2004, a disease characterised by severe leaf defoliation and death of juvenile trees suddenly occurred in plantations of the Copperbelt Forestry Company. This study was undertaken to determine the nature of the disease and extent of damage caused with a view of providing a framework for sustainable management of the plantations. Disease incidence, severity and impact on plantations using the crown damage index were assessed for three consecutive years. Eucalyptus grandis was more affected than E. cloeziana and leaf spot incidence and severity were higher in Kalibu, Kitwe District, than in Kafubu, Kalulushi District. The incidence in Kalibu was 90.4%, causing tree crown damage of 18.6% at the end of the assessment in 2006 compared to 17.5% incidence and 1.02% crown damage recorded in Kafubu. Fungi collected from leaf tissues included species of Aulographina, Cryptosporiopsis, Cylindrocladium and fungi in the Teratosphaeriaceae. Stem pathogens were identified as fungi in the Botryosphaeriaceae and Kirramyces sp. Diseases induced by these pathogens are increasingly becoming major threats to young eucalypts, resulting in poor stem form. Factors favouring disease development are described and these need to be properly managed to minimise the impact of diseases in addition to the need to establish selection and breeding programmes to develop tolerant genotypes to ensure a sustainable future for the forestry industry in Zambia.

Blackwood (Acacia melanoxylon R. Br.) plantation silviculture: a review

Summary In Australia, blackwood is logged from native forest stands. The limited size of this resource, and its capacity to meet the demand for blackwood timber in the longer term, has resulted recently in the establishment of plantations in Australia. Plantation silviculture of blackwood has a longer history in New Zealand, South Africa and Brazil. A major problem in plantation establishment is that blackwood has poor apical dominance, producing large numbers of branches and trees of poor stem form when grown in full light. Blackwood has two types of foliage, bipinnate compound leaves and vertically-oriented phyllodes. A phase change from leaves to phyllodes occurs, though this is reversible. The type foliage present can be a useful indicator of the prevailing light conditions. Apical dominance is associated with conditions of low light shade also reduces the extent of branch development, encouraging good form. Blackwood is susceptible to frost and defoliation by pests though both are a function of the type of foliage present. Leaves are more efficient than phyllodes at producing photosynthate per unit carbon invested in foliage, though both types of foliage appear reasonably well adapted to a range of light environments. Application of phosphorus fertiliser at planting is generally associated with improved early growth and this may be allied to increased numbers of root nodules. Addition of nitrogen fertiliser appears unnecessary in the absence of N deficiency. Whether grown in pure or mixed stands, form pruning is necessary to produce good stem form, and lift pruning of live branches to produce clearwood. Various approaches to form pruning have been used but all are designed to prevent the development of large branches. Crown shape, which is variable in blackwood, can determine whether lift pruning reduces subsequent growth. Establishment at high stockings and thinning to a final crop of between 100 and 250 stems ha−1 is used commercially. Nurse crops have been used, particularly in Tasmania, to induce good form and to minimise the requirement for form pruning. This practice has met with mixed success as the use of eucalypts or Pinus radiata has led to overtopping and suppression of the blackwood. In New Zealand, the use of nurse crops has led to little improvement in stem form.

INVESTIGATION ON THE STEM QUALITY OF PINUS BRUTIA INDIVIDUALS GROWN FROM HEALTY TREES WITH POOR STEM QUALITY

Natural mature brutian pine (Pinus brutia Ten.) stands are generally composed of individual trees with poor stem quality owing to fact that they have not been managed by a proper thinning programme. An expectation gains weight as to whether the undesirable trails will carry in the new generation to be established by using the seed obtained from those of trees with poor stem form. The present investigation was commenced in 1986 in order to study this problem. 1+0 seedlings grown by generative and vegetative methods from the Suleyman Demirel Universitesi Orman Fakultesi Dergisi Seri: A, Sayi: 2, Yil: 2001, ISSN: 1302-7085, Sayfa:11-26 12 healty trees with good crown structure but poor stem form were planted in autumn,1987 to carry out the experiments. Assesments were made in 1994 after the individuals are attained a certain height and form at 7 year of age. But, time was too early for reliable result on this subject. Final report was not published that time, therefore. In the spring of 2001 observations clearly showed that the sceptical topic mentioned above is not justified and a new generation composed of high quality young individuals may be regenerated by the readily available seed supply from the old generation with poor stem form. Keywords : Pinus brutia stands, regeneration, individuals with poor stem form.

Boron deficiency in eucalypt plantations in China

Boron deficiency is identified as one of the more important causes of poor stem form and malformed leaves in plantations of Eucalyptusglobulus in Yunnan Province, and of Eucalyptusgrandis, Eucalyptustereticornis, and Eucalyptusurophylla in Guandong Province. Symptoms of B deficiency in E. globulus were rolled and malformed leaves, stem dieback, and a prostrate form. In E. urophylla, leaf margins became chlorotic then necrotic, leaves turned brittle and corky, shoots died back, and the upper stem nodes were enlarged supporting numerous short-lived axillary shoots. In E. grandis, stem dieback was preceded by the basipetal accumulation of anthocyanin in leaves. Boron-deficient E. tereticornis leaves developed marginal and interveinal chlorosis and recurved margins. Depressed foliar B concentrations were associated with visible symptoms. In E. globulus, the mean B concentration in young leaves of healthy trees was 31 mg/kg dry matter compared with 10 mg/kg in prostrate trees. Symptoms did not appear in E. globulus trees supplied with B fertilizer at planting. Normal shoot growth was restored in E. urophylla by the addition of B to the soil.

Results of aPinus taedaProgeny/Provenance Type Trial in Natal, South Africa

SYNOPSIS Fifty-two families of Pinus taeda from the North Carolina State University's co-operative breeding programme were tested in Natal and compared to three open-pollinated South African seed orchard families. At fifteen years the best provenances are those from USA planting zone 4. Great variation exists among origins as well as families within this zone. The vigorous family from Marion County in Florida had poor stem form. The Livingstone Parish seed source from Louisiana did very well, both in vigour and form. The most northern and north-eastern sources had poor vigour. The results support earlier reports that seed from the most southern part of the natural range of the species should be imported and tested. Appreciable gains would be possible if families from the American co-operative breeding programme could be imported.

Effects of micronutrients on the growth form of two families of Pinus radiata (D.Don) seedlings

Micro-element deficiencies have been implicated in the development of poor stem form in Pinus radiata plantations. Cu, Mn and B have been implicated in previous studies as influencing tree form and/or the process of lignification in plants. Therefore an experiment was initiated to examine the individual and interactive effects exhibited by these trace elements on stem form and lignification. The investigation showed that Cu deficiency reduced both lignification and stem form in seedlings. Mn, competing with Cu for uptake, enhanced the symptoms of Cu deficiency. Boron addition did not alleviate the expression of deformity or increase levels of lignification. There was a clear family influence on the development of seedling stem form in response to variations in mineral nutrition.

International Provenance Trials of Pinus kesiya in South Africa: Results at First Thinning

SYNOPSIS A series of international provenance trials of Pinus kesiya were planted in three forest regions of South Africa during 1972–73. The results of measurements taken at the age of the first thinning (82–114 months) show that P. kesiya is an extremely good volume and wood mass producer (± 40 m3/ha/a in unthinned stands or ± 14 dry t/ha/a), but is plagued by poor stem form, the frequent occurrence of forks and a large number of relatively coarse branches. The species is also susceptible to the pine woolly aphid. The presence of seedlots of South African and Zambian P. kesiya taken from selected trees revealed that considerable progress can be made towards obtaining an acceptable plantation tree by positive and systematic selection for better form and branching despite the negative correlations between vigour and these characters. If the problems of stem form, coarse branching and susceptibility to aphids can be cured through tree breeding, the high volume growth of P. kesiya and its good wood properti...

Provenance Trials ofEucalyptus urophyllaandE. albain South Africa: Seven-year Results

SYNOPSIS Three trials of E. urophylla and E. alba seedlots were established, one in the semi-temperate eastern Transvaal and two in subtropical Zululand, during 1973 and 1974. The trials consisted of imported seed-lots of both species and South African and Brazilian collections of E. urophylla. Although the trial in the eastern Transvaal suffered frost damage, both the volume and the wood mass growth of E. urophylla were better there than in Zululand. Volume production of E. urophylla was less than that of either E. grandis or E. saligna of the same age, but because of the higher wood density of E. urophylla the wood mass production of this species was better than that of E. saligna and equal to or slightly better than that of ordinary E. grandis. The stem form of most E. urophylla seedlots was very good. Within the species, two types of E. urophylla were distinguishable, the smooth-barked and the rough-barked. Although the two types did not differ much in volume production in Zululand, in the eastern Transvaal the rough-barked seedlots were superior. The smooth-barked seedlots had a higher basic wood density than the rough-barked types, making them superior wood mass producers in Zululand. In the eastern Transvaal the rough-barked seedlots, because of their very good volume production, were the best wood mass producers despite their lower basic wood density. Eucalyptus urophylla has shown very high potential as a producer of mining timber and pulpwood and there are indications that it could be a good sawtimber species. Eucalyptus alba seedlots showed poor to fair growth and poor to very poor stem form. This species has no potential for use in South Africa.

Low Pruning Radiata Pine

SUMMARY The short-term effects on basal area increment, volume increment, and stem form of pruning radiata pine (Pinus radiata D. Don) to 2.3 m four, five and six years after planting at Brunswick, Western Australia, are compared with the growth of unpruned trees, and the relevance of these effects to pruning policy are discussed. The trees in plots pruned at 4 years produced 18 per cent less stem volume than unpruned trees at a stand age of nine years. Pruning did not increase the incidence of poor stem form or stem defects such as forks or multiple leaders.