Species-site matching in mixed species plantations of native trees in tropical Australia

Mixed species plantations using native trees are increasingly being considered for sustainable timber production. Successful application of mixed species forestry systems requires knowledge of the potential spatial interaction between species in order to minimise the chance of dominance and suppression and to maximise wood production. Here, we examined species performances across 52 experimental plots of tree mixtures established on cleared rainforest land to analyse relationships between the growth of component species and climate and soil conditions. We derived site index (SI) equations for ten priority species to evaluate performance and site preferences. Variation in SI of focus species demonstrated that there are strong species-specific responses to climate and soil variables. The best predictor of tree growth for rainforest species Elaeocarpus grandis and Flindersia brayleyana was soil type, as trees grew significantly better on well-draining than on poorly drained soil profiles. Both E. grandis and Eucalyptus pellita showed strong growth response to variation in mean rain days per month. Our study generates understanding of the relative performance of species in mixed species plantations in the Wet Tropics of Australia and improves our ability to predict species growth compatibilities at potential planting sites within the region. Given appropriate species selections and plantation design, mixed plantations of high-value native timber species are capable of sustaining relatively high productivity at a range of sites up to age 10 years, and may offer a feasible approach for large-scale reforestation.     

Comparisons of spatial pattern,structure, and tree composition between virgin and cut-over jarrah forest in Western Australia

Several old growth (unlogged) and regrowth (logged) stands in the northern jarrah forest of Western Australia were studied in respect of spatial pattern of tree species, segregation between tree species, distribution of trees of each species by diameter class, and tree species composition. The species are Eucalyptus marginata and Eucalyptus calophylla (overstorey) and Banksia grandis, Allocasuarina fraseriana, Persoonia longifolia and Persoonia elliptica (understorey).Most populations of the species are aggregated at small but random at large scale. This pattern probably originates from non-random seed fall. Eucalyptus marginata and B. grandis are segregated, probably for the same reason. Manipulative experiments showed that interspecific competition does not prevent establishment of B. grandis seedlings. On a local scale, heterogeneity in several surface soil properties does not help explain spatial patterns.The diameter-class distributions indicate that regeneration of all species occurs irregularly. This probably results directly from the release of dormant advance growth following temporary reduction in overwood competition induced by disturbance such as wildfire or logging. Banksia grandis is not a rare or scattered component of old growth jarrah forest. A single logging of jarrah trees does not necessarily alter the density or diameter class distribution of B. grandis.     

Fertilization in a Fourth Rotation Eucalyptus grandis Plantation with Minimal Management

ABSTRACT

Successive rotation and wood harvest of fast growing trees, like Eucalyptus grandis, can deplete soil nutrient pools. In these intensively used soils, productivity can decrease, and fertilization can be necessary to recover soil fertility. The aim of this work is to evaluate if fertilization with N and P increases tree growth and foliar nutrients in an Eucalyptus grandis plantation growing over a soil used for three rotations of this species. In the same experiment, both fertilization on seedlings and coppiced trees were evaluated. One and two years after planting, any fertilization treatment increased tree growth, even though coppiced trees had higher total height and DBH than replanted trees. Coppiced trees had lower specific leaf area, as well as lower N and P leaf concentration. The lack of promotion in growth due to fertilization can be explained by the inputs of nutrients from the harvest residues of the previous rotation. As residues were never burned in this site, its decomposition released a high part of nutrients necessary to sustain growth during the first two years. We conclude that in sites where residues were left on site and were not burned, nutrient availability is enough and so fertilization at establishment is not necessary. It remains to be determined if fertilization is necessary at mid or end rotation, in order to balance nutrients export with harvest wood.     

桉树生态问题及发展思路

列举了桉树生态问题争论的主要事件及焦点,阐述了桉树的水分利用、养分消耗和化感作用,在对桉树生态问题进行评价的基础上,提出了正视桉树人工林的生态问题,强化规划、设计、施工监督和质量管理;遗传育种应由单一性状向多性状转变,培育具有节水保肥的新品种和优良无性系;注重桉树菌根等新技术的研发与应用,提高桉树对土壤养分的有效利用和保水能力;采取综合营林措施,维护桉树林的土壤养分平衡;开展固氮菌接种和维持林地的持久生产力等桉树发展思路。     

Carbon balance for different management practices for fast growing tree species planted on former pastureland in southern Europe: a case study using the CO2Fix model

Although it is known that forestry mitigates carbon emissions to some degree, there is still a need to investigate the extent to which changes in forest management regimes affect the carbon cycle. In a climate-change scenario, forest management schemes must be optimized to maximize product supply and minimize environmental impacts. It is difficult to predict the mitigating effects of different silvicultural regimes because of differences in the growth characteristics of each species, destination of products, and industrial efficiencies. The objective of the present study was to use a modeling approach to evaluate the effects of different management regimes for fast growing species in southern temperate Europe in relation to mitigating climate change. A comprehensive study was carried out considering the C sink effect in biomass, soil and wood products, the substitutive effect of bioenergy, and particular conditions of the forest industry in southern Europe. The mechanistic CO₂Fix model was parameterized for three species used in fast growing plantations in southern Europe: Eucalyptus globulus, Eucalyptus nitens, and Pinus radiata. Data from 120 plots covering the complete age range observed for each species were used to calculate changes in C stocks in aboveground biomass and organic and mineral soil and to validate the parameterized model for these conditions. Additional information about the efficiency of forest industry processes in the region was also considered. A strong bias in soil organic carbon estimation was observed and attributed to overestimations in the decomposition rates of soil compartments. Slight bias was also observed in the carbon biomass estimation when forest-specific yield models were used to simulate afforestation over former pastureland. As regards the model sensitivity, the Yasso model was strongly robust to turnover of leaves, roots, and branches. The chip wood production alternative yielded higher carbon stock in biomass and products, as well as in bioenergy substitution effect, than the sawn wood production alternative. Nevertheless, the sawn wood alternative was the most effective as regards the C stock in the soil. Site index had an important effect for all species, alternatives, and compartments, and mitigating effects increased with site index. Harvesting of clearcutting and thinning slash for bioenergy use led to a slight decrease in the soil carbon equilibrium but significantly increased the mitigation effect through bioenergy use.     

国外工业人工林培育的目标及技术途径

作者论述了当前国际上工业人工林培育的定向、速生、丰产、优质、经济效益和稳定性等6个目标; 介绍了工业人工林的主要培育措施, 包括: 遗传控制、立地控制、密度控制、维护与提高林地土壤肥力、优化栽培模式、生态系统管理等; 指出了当前的人工林基地在生态方面存在的3个问题: 病虫害日趋严重、林地土壤退化、人工林抵御自然灾害及大气污染的能力弱.     

Emergence,early survival,and growth of seedlings of six tree species in Mediterranean forest of Western Australia

This paper reports an experimental and comparative field study of germination, early survival, and height growth of six tree species in the northern jarrah forest of Western Australia. The species are Eucalyptus marginata and Eucalyptus calophylla (comprising the overstorey) and Banksia grandis, Allocasuarina fraseriana, Persoonia longifolia and Persoonia elliptica (all understorey).Seed weight does not correlate with germination success, survival or height growth. Germination success is greatest for B. grandis (90%) and zero for Persoonia spp. Survival of caged germinants is highest for B. grandis and E. calophylla; that of uncaged seedlings is least for E. marginata, E. calophylla and B. grandis because of browsing.Over 40% of seeds of E. marginata, E. calophylla and B. grandis do not germinate because they are harvested and presumably eaten. Viability of seeds of all species exceeds 70%. Germination is influenced by type and depth of litter but not by artificial shading or root competition from forest trees. Browsing by herbivores (kangaroos) is an important cause of death of seedlings of E. marginata, E. calophylla and B. grandis. Litter type and depth affect survival of E. calophylla, B. grandis and A. fraseriana but root competition and shading are unimportant. Height growth of E. marginata, E. calophylla and B. grandis is reduced by root competition and browsers further reduce height growth of B. grandis. Litter affects growth of E. marginata and B. grandis and shading influences growth of E. marginata and E. calophylla. Poor germination explains the low abundance of both Persoonia spp. in the jarrah forest but differential seedling establishment does not explain the adult representation of the other four species.     

Early growth results of three Eucalyptus grandis × Eucalyptus nitens hybrid clonal trials and their response to snow events

Eucalyptus grandis × Eucalyptus nitens (G×N) hybrid clones are selected to combine complimentary characteristics of E. nitens and E. grandis. G×N hybrid clones also have the potential to increase growth rates and provide adaptability to a changing climate. A series of three trials planted across a range of high-productivity, mid-altitude sites in the KwaZulu-Natal midlands was established to test the suitability of a suite of G×N hybrid clones. Seven commercially available G×N clones together with two widely planted pure species controls, Eucalyptus dunnii and Eucalyptus smithii, were chosen for this study. The trials were set out in random complete block designs with nine treatments and four replications set out in square plots of 25 trees. The trials were measured for diameter at breast height at 23 months and monitored for snow damage over two winter seasons. Snow was noted at the Baynesfield site and subsequent snow damage assessments were performed. Basal area per hectare was calculated for each plot as a function of diameter at breast height and survival. Significant differences were observed between G×N hybrid clones in both growth and snow tolerance. The top-performing clones significantly outperformed both pure species controls in terms of growth and snow tolerance. Early results indicate that G×N hybrids may be better suited to high-potential, mid-altitude sites exposed to light snow risk than the currently recommended pure species.     

桉树人工林的社会、经济和生态问题

按树具有很好的社会和经济效益。按树人工林不但提供各类木材和非木材产品,而且对农田风沙防护、园林绿化以及水土保持等也有重要作用。但长期以来,对按树人工林的生态问题存在很多争论,本文就此作了详细的论述。     

Can climate at the seed-source predict the success of eucalypts planted on sites that have been grazed for over 100 years?

Many regions of southern Australia exposed to broad-acre grazing are denuded of trees. Re-establishing trees in these landscapes is important for both environmental and economic reasons. We investigated whether climate at the site of origin of the seed can inform species selection for tree establishment on ex-pasture sites within agricultural landscapes. We established trials at four sites in the sheep and cattle grazing region of the Midlands of Tasmania at: ‘Woodland Park’; ‘Sorrel Springs’; ‘Inverel’ and ‘Glen Morey’ farms (long-term average rainfalls of 584, 520, 520, and 479 mm, respectively). Eucalypt species were selected, based on high tolerance to frost and drought inferred from climate at the sites of origin and based on the limited scientific literature available, from across Tasmania and mainland Australia. We investigated the mortality, health and height growth of 18 eucalypt species three months, one and six years after planting. Climatic data from the site of origin of the seed of these species was used to group species into categories of mean annual temperature and mean annual rainfall at seed-source. Sensitivity of species to environment was investigated and compared using modified joint regression. At three planting sites, Woodland Park, Sorrel Springs (except health of the temperature category comparison at six years) and Inverel, we found significantly greater height and health one and six years after planting for local (Tasmanian) compared to non-local (Australian mainland) species, and for species where the site of origin of seed was categorised as low or medium mean annual temperature compared with those categorised as high mean annual temperature. There were no significant differences in mortality for these comparisons. At Glen Morey, height was significantly greater at six years after planting of local compared to non-local species and of species from low and medium mean annual temperature categories compared with the high mean annual temperature category. Mortality was significantly greater in local than non-local species six years after planting. Health was not significantly different for these comparisons. Differences in height, health or mortality of species categorised into mean annual rainfall at seed-source were largely non-significant at all sites one and six years after planting. A study of the sensitivity of species to environment of planting indicated that Tasmanian species were less sensitive than mainland species when height data was compared. When health data was compared, species with a site of origin of seed categorised as low rainfall were less sensitive to environment than species categorised as medium and high-mean rainfall. When mortality data was used significant differences were identified in the sensitivity of species to planting environment but this was not related to locality, mean annual temperature or rainfall at seed-source. Species that attained above average height and low mortality across three or more sites included Eucalyptus pulchella, Eucalyptus perineana (Tasmanian species), and Eucalyptus microcarpa, Eucalyptus benthamii and Eucalyptus melliodora (mainland species). Whilst temperature (and to a lesser extent rainfall) at seed-source is a good indicator of the success of tree establishment, high variability between sites points to the need to consider climate, browsing pressure and farm management at the paddock-scale when planning revegetation plantings. This has important implications for carbon sequestration plantings.     

RESENSIES—REVIEWS

Results at harvesting are described of two comprehensive NPK fertilizer experiments with E. grandis on sites previously under wattle in the Natal Midlands. The experimental sites differ considerably in respect of physiography, climate, and soil. The difference in climate and soil are clearly evident from the respective analyses of soil samples from the sites, one soil of a dystrophic series belonging to the Griffin form, and the other a mesotrophic series of the Hutton form.

Except in one instance, nitrogen application showed no significant response, which is expected on these nitrogen-enriched soils of old wattle plantations. There is a tendency, which in one instance was significant, that nitrogen has a depressive effect on E. grandis, but this is ascribed to burning the transplants when the fertilizer is too concentrated and applied too close to the trees.

Superphosphate application on these sites gives highly profitable results, the additional net profit per ha being nearly R400 on the better site and at least R35 on the poorer site. The optimum application rate on the better site is not more than 130 g superphosphate (8,3% P) per tree, while the optimum rate on the poorer site might be as high as 260 g.

Significant responses to potash application are limited to mesotrophic soils and are of a curvilinear nature. This last phenomenon especially is difficult to explain, but is known to have occurred elsewhere.     

我国桉树生物质能源林研究与利用综述

开发利用林业生物质能源是改善能源结构、保障能源安全和保护生态环境的重要途径之一.桉树不仅是工业原料林生产的重要树种,也是林业生物质能利用的良好原材料.本文从品种研究、评价指标(热值、灰分、生物量、能量现存量)、造林技术(立地条件、整地方式、造林密度、混交造林、收获周期、效益分析)和利用方式等方面阐述了我国桉树生物质能源林研究与利用现状,简要总结了我国发展桉树生物质能源存在的不足并提出今后加强研究的重点,以期为我国合理开发和利用桉树生物质能源提供参考.     

Estimating biomass and macronutrient content of some commercially important plantation species in South Africa

The removal of biomass, in any combination of stemwood, bark or branch harvesting, can cause a significant increase in nutrient loss from commercial timber plantations. Ensuring long-term site productivity of forest plantations is a key issue for forestry management. Managers need to secure a continued supply of tree biomass components, while understanding the impact of various harvesting operations on plantation nutrient reserves. It is imperative to quantify the biomass and nutrient stocks and their removal during silvicultural operations, such as harvesting, burning and various forms of site preparation. At present, there are no simple methods to estimate inherent site nutrient reserves, or nutrient gains through processes such as atmospheric deposition or rock weathering, or the quantities of nutrients lost through silvicultural operations (harvesting, burning and site preparation). The aim of this work was to construct simple multipliers that can be used in conjunction with plantation timber volumes to estimate stem, branch and bark biomass and nutrient contents. The multipliers were developed from data existing for Eucalyptus spp., Pinus patula and Acacia mearnsii stands throughout the summer rainfall region of South Africa and Swaziland. Due to limited data unique nutrient multipliers were not developed for each productivity range and the multipliers were assumed to be consistent across all productivity ranges. The ratios may underestimate on fertile sites where luxury consumption of nutrients may occur and not accurately predict where stand management practices have altered wood density, allometry or canopy architecture. Although genus and species impacted on the quantity of nutrients held in the plantation biomass, productivity and harvesting intensity were the biggest driver of nutrient removal. Although the multipliers developed here have value in creating a general estimate of nutrient content they are from a limited dataset and need to be expanded upon across species, site and age ranges before being able to precisely estimate nutrient contents. Although harvesting is a major component of nutrient export, natural additions and losses of nutrients, and site nutrient reserves need to be known in order to gain a complete understanding of the impact of nutrient loss on site nutrient reserves.     

A comparison of planting and coppice regeneration of Eucalyptus grandis × Eucalyptus urophylla clones in South Africa

Results from two coppice compared to replant trials are presented that originated from clone by site interaction (CSI) trials established on high? and low?productivity sites in subtropical coastal KwaZulu?Natal, South Africa. After the 84?month CSI trial measurements were completed the trees were harvested. Selected plots were allowed to coppice with the remainder replanted to the same four Eucalyptus grandis×Eucalyptus urophylla hybrid clones. Growth was higher at Kwambo Timbers (average mean annual increment [MAI] 34 wet white tonnes [wwt] ha?1 y?1), characterised by a higher mean annual precipitation, than at Palm Ridge (average MAI 11 wwt ha?1 y?1). In these trials coppicing of sufficient stumps per hectare (>1 000 stumps ha?1) resulted in similar volume production on the higher?productivity site and slightly improved (additional 3.4 wwt ha?1 y?1) yield on the lower?productivity site compared with the planted crop. The benefit of coppicing was mainly related to a reduction in the temporary unplanted period and reduced establishment cost. This study showed that coppicing can be a viable, cost?effective alternative to planting in commercial forestry if a number of criteria are met. However, it is recommended that the decision to coppice or to replant should be evaluated on a case?by?case basis.     

An evaluation of the conical approximation as a generic model for estimating stem volume, biomass and nutrient content in young Eucalyptus plantations

Accurately and non-destructively quantifying the volume, mass or nutrient content of tree components is fundamental for assessing the impact of site, treatment, and climate on biomass, carbon sequestration, and nutrient uptake of a growing plantation. Typically, this has involved the application of allometric equations utilising diameter and height, but for accurate results, these equations are often specific to species, site, and silvicultural treatment. In this study, we assessed the value of incorporating a third piece of information: the height of diameter measurement. We derived a more general volume equation, based on the conical approximation, using a diameter projected to the base of the tree. Common equations were developed which allowed an accurate estimate of stem volume, dry weight and nutrient content across two key plantation grown eucalypt species, Eucalyptus grandis W. Hill ex Maiden and Eucalyptus globulus (Labill.). The conical model was developed with plantation-grown E. grandis trees ranging from 0.28 to 15.85 m in height (1.05 g to 80.3 kg stem wood dry weight), and E. globulus trees ranging from 0.10 to 34.4 m in height (stem wood dry weight from 0.48 g to 652 kg), grown under a range of contrasting cultural treatments, including spacing (E. grandis), site (E. globulus) and fertilization (nitrogen and phosphorus) for both species. With log transformed data the conical function (V_con) was closely related to stem sectional volume over bark and stem weight (R² = 0.996 and 0.990, respectively) for both E. grandis and E. globulus, and the same regressions can be applied to both species. Back transformed data compared with the original data yielded modelling efficiencies of 0.99 and 0.97, respectively. Relationships between V_con and bark dry weight differed for the two species, reflecting differing bark characteristics. Young trees with juvenile foliage had a different form of relationship to older trees with intermediate or adult foliage, the change of slope corresponding to heights about 1.5 m for E. grandis and age 1 year for E. globulus. The V_con model proved to be robust, and unlike conventional models, does not need additional parameters for estimating biomass under different cultural treatments. More than 99% of the statistical variance of the logarithm of biomass was accounted for in the model. V_con captures most of the change in stem taper associated with cultural treatments and some of the change in stem form that occurs after the crown base has lifted appreciably. Fertilization increased N and P concentrations in stem wood and bark, and regressions to estimate N and P contents (the products of biomass and concentration) were dependent on treatment. For instance, there was a large growth response to N fertilization in E. globulus corresponding with a change (P < 0.05) in the intercept of the regression to estimate N content.     

速生桉树造林常见问题与对策

桉树作为南方速生丰产林的首选树种越来越受到人们的重视和青睐,南方几省掀起了新一轮造林高潮,但随着社会大规模造林,也出现越来越多的造林问题:只求数量不求质量、林地准备和造林措施不规范,出现了许多低残林。针对这些问题开展了试验和调查研究,提出解决对策,为广大造林户提供参考,解决当前造林存在问题,提高林地单位产量,做到林地可持续经营,实现最佳的经济效益。     

Stand Density Management Diagrams for Three Exotic Tree Species in Smallholder Plantations in Vietnam

When smallholder farmers establish tree plantations to sell wood to the wood industry, they may run into problems when the plantations are mature and to be marketed because these farmers usually (1) do not know how to estimate the growing stock and (2) do not have sufficient knowledge of the wood markets. In this study, we tackle problem (1) and present stand density management diagrams (SDMDs) as a simple tool that allows rapid estimation of standing volume from data that stem from very basic inventory. Our data come from smallholder plantations in Vietnam, from four communes in the provinces of Binh Dinh and Phu Tho. Immense afforestation activities have been taken place in the country during the past two decades and it is special to Vietnam that a large share of these afforestations are under smallholder management with the goal to generate an additional source of income for these rural poor. A certain type of SDMDs is elaborated for three important exotic tree species commonly used for establishing industrial tree plantations (Acacia hybrid, Acacia mangium and Eucalyptus urophylla). They can be used for volume estimation and are also a tool to guide stand management and silvicultural treatments in general. Both implementation of the inventory and usage of the SDMDs are straightforward and simple so that this tool may be well suited to support smallholders in a better informed marketing of their wood, as well as, a better informed silvicultural management of their plantations.     

The silviculture of conifers in Great Britain

The original paper by H.M. Steven, with this title, describedthe silvicultural characteristics of the main coniferous speciesthen available in British forestry. The use of these introducedconifers was justified by the limited site tolerances of theone native species, Scots pine, and the need to expand forestcover on to sites with infertile soils in harsh climatic conditions. This paper reviews the developments in silvicultural techniquesand understanding that have enabled the rapid expansion of productiveforestry in the last seventy years:

• The problems associated with afforestation, requiring ameliorationof soil physical and chemical conditions, have been resolvedand the climatic limits to the use of individual species aremore clearly defined.
• Increased knowledge of the physiologicalresponses of individualspecies to environmental factors hasinfluenced silviculturalpractice from nursery production tothe regeneration of maturestands.
• Analysis of genetic variationwithin introduced conifer specieshas refined their use andis leading to improvements in theirproductivity and timberquality.
• The application of ecological principles, based onthe ecosystemconcept, has led to an understanding of foreststand dynamicsthat should ensure production from exotic specieson a sustainablebasis.

Future requirements in the silviculture of conifers includethe transferof the results of computer simulation modellinginto practice, the developmentof silvicultural systems appropriateto British conditions and greater emphasis on the quality ofproduction.     

Effects of planting food crops on survival and early growth of timber trees in eastern Panama

Restoration of degraded pasture lands in the tropics through afforestation is widely supported. The greatest obstacle to afforestation, however, is the long delay before initial financial returns from wood harvesting are realized. Interplanting young trees with food or energy crops has been proposed as a strategy to help overcome this obstacle. We investigated the impact of this practice on the survival and growth performance of young tropical tree seedlings in Panama. Five native timber tree species and the exotic species Tectona grandis were interplanted with four different crop rotations and monitored over 2 years. Survival of young tree seedlings was up to eight times higher when planted in association with Manihot esculenta. Only during the first 3 months after maize sowing was a significant negative effect of intercropping on tree seedling survival found. Here, survival rate of tree seedlings was up to four times lower than in the pure plantation. Tree growth was not adversely affected by crops. In fact, Astronium graveolens, Cedrela odorata and Terminalia amazonia showed significantly superior growth performance in association with both Zea mays and Cajanus cajan. When combined with the latter, the height increment of these tree species was up to four times that achieved in pure plantations. We conclude that intercropping can be an important silvicultural practice to facilitate forest restoration. Multi-purpose shrubby crop species with cropping cycles of more than 6 months are particularly beneficial, as they quickly shade out grasses, thus reducing the need for herbicides.