Major Plantation Species Research Articles

Plasticity of leaf functional traits and growth responses to disturbance among cutting cultivars of Cryptomeria japonica in southern Japan

ABSTRACT Cryptomeria japonica (Thunb. ex L. f.) D. Don is the most major plantation species in Japan, and cultivars have been developed and planted under variable environmental conditions across the country. Productivity of clonal plantations is influenced by the ability of the genotype to acclimate to edaphic- and geographic-scale variation in environmental conditions and disturbance regimes. Because all individuals are genetically identical in a clonal plantation, the trait differences among individuals represent phenotypic plasticity. Here, we investigated how phenotypic plasticity and response to disturbance vary among cutting cultivars of C. japonica. We compared tree height, leaf morphology, nitrogen content, and frequency/intensity of growth-release observed in tree rings after thinning and disturbance among six cutting cultivars in 45-year-old provenance trials in south-western Japan. Nitrogen use efficiency was higher in the site where maximum tree height (H max) was taller, while shoot mass per area (SMA) was larger in the site where H max was shorter. Cultivars that grew well had high leaf nitrogen content (N G) and showed more efficient nitrogen use with high nitrogen-resorption efficiency (NRE). Yabukuguri, an intermediate-growth cultivar, was characterized by large SMA and greater plasticity in SMA and tree height in response to topographical and regional variation, as well as greater intensity of growth-release in tree-ring series indicating growth resilience following disturbance. Our results provide guidelines for selecting cultivars with high acclimation potential and resilience to environmental perturbation, which is important for sustaining plantation forests in uncertain environmental conditions expected by future climate change.

Reducing ecological risk from the impacts of introduced exotic species in forestry industry: Limiting the invasiveness through a management and biological practices in Acacias plantation in Indonesia

Balance benefit of ecological, economic, and social is a part of sustainable forest management. Industrial forest plantation is one of the ecological practices through increasing land cover to provide a good impact for economic and social. Introducing suitable species for industry from out of regions is commonly practiced in the plantation. In Indonesia, some Acacias species have been recognized as major plantation species to meet industrial requirements that are economically feasible, suited to major end-product, high productivity, and fast growth. However, some studies have classified the Acacias as exotic species which potentially show an invasive. Taking into account such invasiveness and anticipating ecological risk, this paper presents some considerations on plantation management and biological practices of the Acacias. Compromises among the reproductive system, growth, and rotation in the plantation management could limit the invasiveness. Besides high stand productivity, results from genetic and breeding could also provide a positive impact to diminish the reproductive process of trees that consequently reduce seeds in the Acacias plantation and limit its invasiveness. It concludes that some considerations and a good understanding of biological factors in plantation management practices could reduce ecological risk from the invasiveness of Acacias, and even it could be used for increasing plantation productivity.

Chromosome-specific polymorphic SSR markers in tropical eucalypt species using low coverage whole genome sequences: systematic characterization and validation.

Eucalyptus is one of the major plantation species with wide variety of industrial uses. Polymorphic and informative simple sequence repeats (SSRs) have broad range of applications in genetic analysis. In this study, two individuals of Eucalyptus tereticornis (ET217 and ET86), one individual each from E. camaldulensis (EC17) and E. grandis (EG9) were subjected to whole genome resequencing. Low coverage (10×) genome sequencing was used to find polymorphic SSRs between the individuals. Average number of SSR loci identified was 95,513 and the density of SSRs per Mb was from 157.39 in EG9 to 155.08 in EC17. Among all the SSRs detected, the most abundant repeat motifs were di-nucleotide (59.6%–62.5%), followed by tri- (23.7%–27.2%), tetra- (5.2%–5.6%), penta- (5.0%–5.3%), and hexa-nucleotide (2.7%–2.9%). The predominant SSR motif units were AG/CT and AAG/TTC. Computational genome analysis predicted the SSR length variations between the individuals and identified the gene functions of SSR containing sequences. Selected subset of polymorphic markers was validated in a full-sib family of eucalypts. Additionally, genome-wide characterization of single nucleotide polymorphisms, InDels and transcriptional regulators were carried out. These variations will find their utility in genome-wide association studies as well as understanding of molecular mechanisms involved in key economic traits. The genomic resources generated in this study would provide an impetus to integrate genomics in marker-trait associations and breeding of tropical eucalypts.

Plant trait database for Cryptomeria japonica and Chamaecyparis obtusa (SugiHinoki DB): Their physiology, morphology, anatomy and biochemistry

AbstractCryptomeria japonica (sugi) and Chamaecyparis obtusa (hinoki) are major Japanese timber species whose plantation area accounts for 44 and 25%, respectively, of the plantation forests in Japan. Physiology, anatomy and ecology of the species have been intensively studied for this half century, which now forms a huge stock of information. These data, however, were scattered in diverse sources, including papers, bulletins of research institutes, reports of other kinds and books, and were presented in nonstandardized, diverse styles in each source. This paper provides a database (SugiHinoki DB) that compiles 177 plant traits of sugi and hinoki from 364 primary sources published since 1950. The compiled traits include physiological, morphological, anatomical and biochemical features that are recognized as relevant to life history strategies, vegetation modeling and global change responses. Collected data have been obtained under different environmental conditions, for plants with different ages and for organs with a different age or different position, which provide information of within‐species variation for a given trait. Each data entry is accompanied by detailed ancillary information describing the site of measurement, stand of measurement and detailed measurement conditions, which help users account for data variations as a consequence of phenotypic plasticity and genetic variations and to filter data. To provide data in a consistent format, the data and the ancillary information were standardized, and units were converted. After data compilation, outliers were detected by calculating interquartile range for each trait per each species. As of August 2019, SugiHinokiDB contains 24,683 data entries (16,410 for sugi, 8,273 for hinoki). As sugi and hinoki are major plantation species in Japan, the data mostly came from study sites in Japan (from Hokkaido in the north to Yakushima island in Kyushu to the south) but were also obtained from arboretums or plantation forests in Taiwan, Korea and China. Data were largely obtained from plants in plantation forests but also from plants in natural forests and under experimental conditions. The improved availability of trait data offered by SugiHinokiDB provides new research opportunities, such as the intensive parameterization of vegetation models for a more accurate prediction of climate change impacts.

Relationship between stem diameter and transpiration for Japanese cypress trees: Implications for estimating canopy transpiration

AbstractPrevious studies reported relationships between stem diameter at breast height (DBH) and whole‐tree transpiration (Qt) across a variety of species and locations. It might be possible to develop a relationship between DBH and Qt with smaller variations when we focused on a single species. We attempted to develop such a relationship for Japanese cypress (Chamaecyparis obtusa), which is one of the major plantation species in Japan. We collated Qt for 51 Japanese cypress trees from nine different‐sized and different‐aged stands using the sap flux method. We found a strong linear correlation between DBH and the reference value of Qt at a vapour pressure deficit of 1 kPa (R = .883). This was a consequence of a strong correlation between DBH and sapwood area (AS_tree; R = .973) and the absence of a correlation between DBH and sap flux density (R = −.043). We confirmed that using the relationship between DBH and AS_tree, while assuming typical responses of sap flux density to meteorological factors, provides reasonable Qt estimates. This study also demonstrated how the DBH–Qt relationship can be applied to estimate changes in EC with changing forest management.

Effects of soil water decline on diurnal and seasonal variations in sap flux density for differently aged Japanese cypress (Chamaecyparis obtusa) trees

The effects of soil drought on transpiration are often neglected when predicting transpiration for forests in humid regions under the influence of the Asian monsoon. These effects have indeed been neglected for Japanese cypress, Chamaecyparis obtusa, a major plantation species in Japan and the surrounding area, probably because previous studies have reported no clear effects of soil drought on transpiration for Japanese cypress forests. However, a few studies have reported an apparent reduction in transpiration with soil drought for young Japanese cypress forests. It remains unclear whether such a reduction in transpiration is limited to young Japanese cypress forests or if it is not uncommon for mature Japanese cypress forests, which occupy a large area in Japan. To clarify this point, we conducted sap flux measurements in a year with soil drought on three differently aged Japanese cypress stands including mature (43 years old) and relatively young (23 and 26 years old) trees. In a diurnal time scale, a cross correlation analysis of sap flux density (Fd) and vapor pressure deficit (VPD) showed that the time lags between Fd and VPD were 1-3 h in dry soil conditions. These were larger than those of wet soil conditions (<1 h) for all sample trees. Fd at a given VPD in dry soil conditions was smaller than that in wet soil conditions for all sample trees; a 28%–63% reduction in the rate of change in Fd was observed under dry soil conditions. Because our results were obtained when the non-exceedance probability of recorded monthly precipitation was 9%–18%, the results suggest the need to consider the effects of soil drought more extensively. Those effects should be considered for not only relatively young but also mature Japanese cypress when predicting diurnal and seasonal patterns of transpiration in years with soil drought, and when predicting inter-annual patterns of transpiration for Japanese cypress despite humid temperate climate.

기후변화를 고려한 잣나무의 미래 적지적수 변화 예측

Korean pines(Pinus koraiensis) are one of the major plantation species in the Republic of Korea and their natural habitats range from Japan and China to Siberia. The seed of Korean pines, pine nuts, are well know for good food reserves. Due to the global changes which drive the Korean peninsula into the semi-tropical climate, current plantations and natural habitats of Korean pines are faced with the change in the environmental conditions to some extent. To anticipate suitable sites for Korean pines in the future, the location of Korean pines were extracted from the 'Map of suitable trees on a site' that provides the map of suitable trees on a site considering tree species for timber and special uses, and then MaxEnt modelling was used for generating a prediction map on the basis of statistical analysis. As a result, the order of predicted suitable sites were Kangwon-do, Kyungsangbuk-do and Chungcheongbuk-do provinces and sites with high elevation within those provinces were considered most suitable in common. The prediction map of suitable sites for Korean pines presented that suitable sites in the future decreased by 72.2% by 2050's and almost disappeared with a decrease of 92.1% by 2070's on a nationwide scale. In relation to the major production regions of pine nuts in South Korea - Gapyung gun and Yangpyung gun, Kyunggi province and Hongcheon gun, Kangwon province, suitable sites within their areas were predicted to increase by 2050's but become extinct in South Korea by 2070's. To establish a long-term countermeasures against the improvement on forest productivity quality in terms of managing national food security, the result from this study can be considered as a firm basis of predicting plantation suitability. Also, it can be used to predict the changes in supply of forest products and thereby market values in accordance with climate change scenarios.

冰雪灾害对中亚热带人工针叶林净初级生产力的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 冰雪灾害对中亚热带人工针叶林净初级生产力的影响 DOI: 10.5846/stxb201309222322 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划（2012CB416903）；国家自然科学基金项目（31130009）；中国科学院知识创新工程重要方向青年人才项目（KZCX2-EW-QN305） The effects of ice storms on net primary productivity in a subtropical coniferous plantation Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:结合中亚热带江西千烟洲人工针叶林2005、2008和2011年3次树木清查数据以及树木相对生长方程，比较了2008年1月南方冰雪灾害前后的NPP，评价了森林生态系统灾后的恢复能力。结果表明：乡土树种马尾松（Pinus massoniana）与杉木（Cunninghamia lanceolata）比外来树种湿地松（Pinus elliottii）抗灾害能力强；在个体水平上，胸径（D）较大的树木抗灾害能力较差。灾后马尾松与杉木的D 增长率降低，而湿地松增大。冰雪灾害导致大量碳（10.44 t C/hm2）从乔木层碳库转移到死生物量碳库，占乔木层碳储量的18.28%。灾前NPP和碳利用效率（CUE）分别为736.23 g C m-2 a-1和0.41；灾后经过近4年的恢复，NPP和CUE分别为683.08 g C m-2 a-1和0.38。 Abstract:In the context of global warming, climate change will increase the occurrence probability of extreme weather events such as severe droughts and ice storms. In recent years, the increasing frequency of ice storms in southern China has prompted us to study the impact of these weather events on the net primary productive (NPP) of forest ecosystem, particularly plantations, which are more sensitive to extreme weather events. Severe ice storms during mid-January and mid-February 2008 in southern China provided an opportunity to study the effects of this disturbance on the NPP of a plantation. We used data from field inventories and eddy covariance observations to evaluate the direct impact of the ice storms and the post-ice storm recovery in a subtropical plantation at Qianyanzhou, Jiangxi Province. We developed biomass allometric equations for the three major plantation species; estimated the NPP before and after the ice storms by combining the forest inventories for 2005, 2008, and 2011; and evaluated the recovery ability of the ecosystem. We obtained the following results. (1) The optimal biomass model developed from our survey data was a power function model. The biomass model fit for slash pine (Pinus elliottii) and Chinese fir (Cunninghamia lanceolata) was improved after adding tree height as a further independent variable, whereas that of Masson pine (Pinus massoniana) was not. Compared to the biomass data collected from other stands calculated using allometric equations, the biomass calculated using the optimal model was closest to the observed values. (2) The exotic species slash pine was more severely damaged by ice storms compared with the native species Masson pine and Chinese fir; this difference can be attributed to the specific characteristics of the slash pine. A large number of broadleaved trees regenerated in the study plot after the ice storms. (3) At the individual level, the extent of damage to trees varied with the stem diameter at breast height (D): trees with a larger D were more susceptible to ice storm damage than tress with a smaller D . Prior to the ice storms, the D growth rate of Masson pine and Chinese fir increased with increasing D class (the maximum values were 1.9 and 0.8 cm/a, respectively), whereas the D growth rate of slash pine increased with decreasing D class, with a maximum value of 0.1 cm/a. Post-ice storm, the relationships between the D growth rate and D class of the three species were exactly reversed. (4) The carbon (C) density of living trees in tree layer was 57.10 t C/hm2 pre-ice storm, but decreased to 46.66 t C/hm2 (a reduction of-10.44 t C/hm2 or 18% of the original living tree biomass pool) post-ice storm. The NPP was 736 g C m-2 a-1 pre-ice storm, and the carbonuse efficiency (the ratio of NPP to gross primary production, CUE) was 0.41. After nearly 4 years of recovery, the NPP was 683.08 g C m-2 a-1 and the CUE was 0.38. Furthermore, the biomass C storage of living trees had increased to 54.38 t C/hm2. 参考文献 相似文献 引证文献

Genetic control of flowering in spotted gum, Corymbia citriodora subsp. variegata and C. maculata

Genetically controlled asynchrony in anthesis is an effective barrier to gene flow between planted and native forests. We investigated the degree of genetically controlled variation in the timing of key floral developmental stages in a major plantation species in subtropical Australia, Corymbia citriodora subsp. variegata K.D. Hill and L.A.S Johnson, and its relative C. maculata K.D. Hill and L.A.S. Johnson. Flowering observations were made in a common garden planting at Bonalbo in northern New South Wales in spring on 1855 trees from eight regions over three consecutive years, and monthly on a subset of 208 trees for 12 months. Peak anthesis time was stable over years and observations from translocated trees tended to be congruent with the observations in native stands, suggesting strong genetic control of anthesis time. A cluster of early flowering provenances was identified from the north-east of the Great Dividing Range. The recognition of a distinct flowering race from this region accorded well with earlier evidence of adaptive differentiation of populations from this region and geographically-structured genetic groupings in C. citriodora subsp. variegata. The early flowering northern race was more fecund, probably associated with its disease tolerance and greater vigour. Bud abundance fluctuated extensively at the regional level across 3 years suggesting bud abundance was more environmentally labile than timing of anthesis. Overall the level of flowering in the planted stand (age 12 years) was low (8–12% of assessed trees with open flowers), and was far lower than in nearby native stands. Low levels of flowering and asynchrony in peak anthesis between flowering races of C. citriodora subsp. variegata may partially mitigate a high likelihood of gene flow where the northern race is planted in the south of the species range neighbouring native stands.

Evaluating the deployment of alternative species in planted conifer forests as a means of adaptation to climate change—case studies in New Zealand and Scotland

A strategy widely proposed for increasing the resilience of forests against the impacts of projected climate change is to increase the number of species planted to spread and reduce the risks from a range of biotic and abiotic hazards. We tested this strategy in two case study areas in planted conifer forests in New Zealand and Scotland. The performance of the major tree species and an alternative was compared: radiata pine and Eucalyptus fastigata in New Zealand and Sitka spruce and Scots pine in Scotland. The process-based model 3-PG2S was used to simulate the effects of projected climate change at the end of this century, with and without CO2 fertilisation, upon productivity and financial returns. The effects of an abiotic hazard and two biotic hazards were considered. Under the current climate, the major species outperform alternatives in nearly all circumstances. However, with climate change, their relative performance alters. In New Zealand, planting of E. fastigata becomes more attractive particularly when various hazards and elevated CO2 concentrations are considered. In Scotland, Scots pine becomes more attractive than Sitka spruce at lower interest rates. The major plantation species in both countries are well suited to the current climate, but deployment of alternative species and/or breeds can help to adapt these planted forests to the impacts of climate change.

Seasonal intrusion of litterfall from non-native pine plantations into surrounding native woodland: Implications for management of an invasive plantation species

Radiata pine (Pinus radiata) is commonly grown throughout the world as a major plantation species. Non-native radiata pine plantations are often established as monocultures amongst large tracts of remnant native vegetation. While the direct impacts on native biodiversity of such vegetation replacement have been well documented, much less is known about how plant litterfall from such plantations influences ecosystem dynamics beyond the confines of the plantation limits. In this study, we assessed the inputs of plant litterfall from radiata pine plantations into surrounding native woodland vegetation over a two-year period in south-eastern Australia. We found that pine litter was a significant and even dominant component of litterfall at certain times of the year, typically autumn and winter, when quantities of pine needles falling were up to three times the fall of native leaves. Pine litter was found to be lower in quality than native litter, containing less carbon (C) and nitrogen (N) and having a higher C:N ratio than native litter. Although the comparatively larger inputs of pine litter resulted in C and N inputs that were 2–3 times those of native litter during some seasons, the influx of low-quality pine litter is likely to decompose slowly and immobilise N, thereby limiting the availability of N for plant growth in the long term. The intrusion of large quantities of pine litter into native eucalypt woodland may have a suite of further short and long term impacts on native biodiversity through a number of mechanisms including alteration of leaf-litter invertebrate communities, increased fire intensity and changes in microclimate. These impacts may be alleviated by preventing pine litter entering woodland communities through the use of modified buffer zones and by employing appropriate plantation design. We discuss the merits and shortfalls of various options available to land mangers to minimise pine-litter intrusion into adjacent native woodlands.

Ecological Impact on Nitrogen and Phosphorus Cycling of a Widespread Fast-growing Leguminous Tropical Forest Plantation Tree Species, Acacia mangium

Symbiotic nitrogen fixation is one of the major pathways of N input to forest ecosystems, enriching N availability, particularly in lowland tropics. Recently there is growing concern regarding the wide areas of fast-growing leguminous plantations that could alter global N2O emissions. Here, we highlight substantially different N and phosphorus utilization and cycling at a plantation of Acacia mangium, which is N2-fixing and one of the major plantation species in tropical/subtropical Asia. The litterfall, fresh leaf quality and fine-root ingrowth of A. mangium were compared to those of non-N2-fixing Swietenia macrophylla and coniferous Araucaria cunninghamii in wet tropical climates in Borneo, Malaysia. The N and P concentrations of the A. mangium fresh leaves were higher than those of the other two species, whereas the P concentration in the leaf-litterfall of A. mangium was less than half that of the others; in contrast the N concentration was higher. The N:P ratio in the A. mangium leaf was markedly increased from fresh-leaf (29) to leaf-litterfall (81). Although the N flux in the total litterfall at the A. mangium plantation was large, the fine-root ingrowth of A. mangium significantly increased by applying both N and P. In conclusion, large quantities of N were accumulated and returned to the forest floor in A. mangium plantation, while its P resorption capacity was efficient. Such large N cycling and restricted P cycling in wide areas of monoculture A. mangium plantations may alter N and P cycling and their balance in the organic layer and soil on a stand level.

Modeling the longitudinal variation in wood specific gravity of planted loblolly pine (Pinus taeda) in the United States

Loblolly pine (Pinus taeda L.) is a major plantation species grown in the southern United States, producing wood having a multitude of uses including pulp and lumber production. Specific gravity (SG) is an important property used to measure the quality of wood produced, and it varies regionally and within the tree with height and radius. SG at different height levels was measured from 407 trees representing 135 plantations across the natural range of loblolly pine. A three-segment quadratic model and a semiparametric model were proposed to explain the vertical and regional variations in SG. Both models were in agreement that a stem can be divided into three segments based on the vertical variation in SG. Based on the fitted models, the mean trend in SG of trees from the southern Atlantic Coastal Plain and Gulf Coastal Plain was observed to be higher than in other physiographical regions (Upper Coastal Plain, Hilly Coastal Plain, northern Atlantic Coastal Plain, and Piedmont). Maps showing the regional variation in disk SG at a specified height were also developed. Maps indicated that the stands in the southern Atlantic Coastal Plain and Gulf Coastal Plain have the highest SG at a given height level.

MYCORRHIZA-LIKE STRUCTURES IN ROOTED MICROSHOOTS OF PINUS PINEA L.

Pinus pinea L. (stone pine) is one of the major plantation species in Iberian Peninsula, being Portugal the largest edible seed producer in the world. The induction and improvement of in vitro rhizogenesis of microshoots of Pinus pinea was developed in our laboratory using a co-culture system with ECM fungi. In the acclimation phase in mixed substrates, or in rhizotrons, anatomical and morphological studies were done to observe the evolution of the root system in microshoots from the co-culture system vs. control plants. Extensive dichotomous and coralloid branching of lateral roots occurred spontaneously in inoculated and control plants as well. Moreover, similar branching occurred in liquid culture of excised seedling roots without the presence of ECM fungi. The striking similarity of these organs with pine ectomycorrhizas prompted their anatomical analysis; however the presence of Hartig net was not confirmed. These results suggested that the development of ECM-like structures might have occurred spontaneously.

Improving controlled pollination methodology for breeding Acacia mangium Willd.

Acacia mangium is a major plantation species for the pulp and paper industry in south-east Asia and there are a number of active breeding programs. The species is predominantly outcrossing, but with a demonstrated capacity to set selfed seed where outcross pollen is limited, with consequent inbreeding depression in the progeny. Current controlled pollination methods therefore include a time-consuming emasculation step. We used microsatellite genotyping of seedlings to determine the consequences of outcross pollination with and without emasculation. Only 1 of 3 mother trees set a small amount (5%) of selfed seed. Using whole inflorescences from the male parent as the pollen applicator rather than sieved pollen reduced outcross contamination rates from 19.1 to 8.7% and substantially increased worker productivity. Application of sugar solution to the female flowers immediately prior to pollination increased yield of sound seeds per spike. Additional improvements to the pollination protocols are discussed.

Detection of Cryptomeria japonica roots with ground penetrating radar

Coarse tree roots, which are responsible for most root carbon storage, are usually measured by destructive methods such as excavation and coring. Ground penetrating radar (GPR) is a non-destructive tool that could be used to detect coarse roots in forest soils. In this study, we examined whether the roots of Cryptomeria japonica, a major plantation species in Japan, can be detected with GPR. We also looked for factors that impact the analysis and detection of roots. Roots and wooden dowels of C. japonica were buried 30 cm deep in sandy granite soil. From GPR measurements with a 900 MHz antenna, the distribution and diameter of samples in several transects were recorded. The buried roots were detected clearly and could be distinguished at diameters of 1.1–5.2 cm. There were significant positive relationships between root diameter and parameters extracted from the resultant GPR waveform. The difference in water content between roots and soil is a crucial factor impacting the ability to detect roots with GPR. We conclude that GPR can be used as a non-destructive tool, but further investigation is needed to determine optimal conditions (e.g. water content) and analytical methods for using GPR to examine roots in forest sites.

Introduction ofPinus radiata for afforestation: a review with reference to Aba, China

Pinus radiata D. Don, native to a California coastal environment, has been introduced to many parts of the world as an exotic species for afforestation. It is now a major plantation species in the Southern Hemisphere. In 1990, it was introduced to the heavily degraded, dry Min river valley area in Aba prefecture of Sichuan Prevince, P. R. China. Survival and growth of young trees planted st several sites appear to be reasonable. This review is to serve as an introduction to the large body of literature onP. radiata for forest scientists in Chine. It convers the following aspects:P. radiata in its native environment and in ex situ plantations, provenance and genetic variations, environmental limitations and climate niche, diseases and pests, lessons from unsuccessful introductions, and the use ofP. radiata for ecological restoration. The early growth ofP. radiata planted in the dry river valley area is briefly described. Potential problems associated with the introduction ofP. radiata in Aba and future research needs are also identified.

Susceptibility of some Eucalyptus species and their hybrids to possum damage

Summary Common brushtail possums (Trichosurus vulpecula) are a significant vertebrate pest of eucalypt plantations in Tasmania; their browsing damage can cause loss in growth, reduced seedling survival and deformities. Possum damage could therefore become a serious problem in Australia's rapidly expanding eucalypt plantations. In addition, expansion of plantation areas is projected to include drier zones, where inter-specific eucalypt hybrids may play an important role. However, hybrids are currently being developed with little knowledge of their resistance to pests. This study examined the susceptibility to browsing by common brushtail possums of a range of eucalypts (Eucalyptus bicostata, E. globulus, E. gunnii, E. nitens, E. morrisbyi and E. ovata) and their F1 hybrids in four separate field trials in Tasmania. The Tasmanian endemics E. gunnii and E. morrisbyi were extremely susceptible to browsing whereas the other four species were relatively resistant. Within E. globulus, significant differences in damage between provenances were also detected. Field damage on interspecific F1 hybrids was generally intermediate in crosses between susceptible and resistant eucalypt species. While the exact degree of susceptibility varied, crossing a relatively resistant species with a highly susceptible species resulted in a significant increase in the susceptibility of the F1 hybrid compared with that of the resistant species. Only the hybrids between the two major plantation species E. nitens and E. globulus were significantly more susceptible to browsing than either the E. nitens or E. globulus controls, which were both relatively resistant. In practical terms, the present study indicated that possum susceptibility is an important factor to consider when investigating the potential of pure species and their hybrids for commercial use.

The pathogenicity of isolates of Endothia gyrosa to Eucalyptus nitens and E. globulus

A severe epidemic of Endothia gyrosa in a plantation of Eucalyptus nitens at Tewkesbury in Tasmania prompted a comparison of the pathogenicity of isolates from this site with that of isolates from elsewhere in Tasmania and mainland Australia. Sixteen isolates were artificially inoculated on 12-month-old seedlings of two major plantation species, E. nitens and E. globulus. The majority of isolates produced lesions on both host species that were significantly different in size to those in non-inoculated seedlings and were not callused-over at 7 months after inoculation. Seedling mortality was negligible. Certain isolates originating from various regions in mainland Australia and from the Tewkesbury site appeared more pathogenic although differences in lesion size between isolates was not always significant. Only one out of seven isolates from Tewkesbury demonstrated significantly higher levels of pathogenicity than all other isolates although there was a trend for isolates from this site to cause greater lesions in size. It is, however, unlikely that the epidemic caused by E. gyrosa at Tewkesbury, even though of far greater impact than previousiy observed on plantations in Australia, is solely the consequence of more pathogenic strains. This conclusion does not exclude the possibility that more pathogenic strains of an opportunist pathogen such as E. gyrosa could have played some determinant role in epidemic development.

The Silviculture of Indigenous and Exotic Forest Trees other than Pines and Eucalypts in Malawi

SYNOPSIS Most of the work of the Department of Forestry for at least the first 30 years since its foundation in 1902 concentrated mainly on indigenous trees such as Widdringtonia nodiflora (Syn. W. whyteii), Pterocarpus angolensis and Khaya nyasica, just to mention a few examples. The emphasis started to change in the early 1930s when it was realised that the faster growing exotic species, mainly pines, could be grown under the local conditions and produce high returns of construction timber in a relatively shorter time than the indigenous species. Gradually the work on the indigenous trees was reduced to almost ad hoc silvicultural trials, mainly on the culturing methods of a few selected species. These were done in the form of unreplicated arboretum plots, although some replicated trials started to be established in the early 1960s. However, by this time, the exotic trees Pinus patula, P. elliottii, P. taeda and the Eucalyptus spp. had by far passed the experimental stage and had become the major plantation species in the country. Consequently attention was almost totally paid to these species and a number of the old indigenous trial plots were neglected or simply forgotten. This paper, therefore, merely lists some of the important indigenous trees of which the plots are still maintained and from which information, although sparse and broken, is available. Information on establishment and management techniques has also been given for each species wherever available.