Lignin chemistry—past,present and future

Summary Some pertinent results and views from the earlier history of lignin chemistry, pointing to the importance of the arylpropane skeleton, are outlined. Later development, beginning with the dehydrogenation theory and experimental studies on the dehydrogenative polymerization of p-hydroxycinnamyl alcohols, is then reviewed. Finally, recent degradative work resulting in a detailed picture of lignin structure is discussed.     

Directions in tropical agroforestry research: past, present, and future

Reflections on the past two decades of organized research in tropical agroforestry raise several issues. Research efforts started with an inductive and experiential approach but have subsequently followed a deductive and experimental approach that includes hypothesis testing and the development of predictive capability; agroforestry research is thus being transformed into a rigorous scientific activity. The research agenda, so far, has given high priority to soil fertility and other biophysical interactions, less priority to anthropological and sociological aspects, and little priority to evaluating costs and returns, pests and diseases, and the so-called non-timber forest (tree) products. Moreover, larger-spatial-scale issues, such as carbon sequestration, water quality, and biodiversity conservation, have been neglected because of the emphasis on field- and farm-scale studies. Overall, the high expectations that were raised about the role and potential of agroforestry as a development vehicle have not been fulfilled. In order to overcome this, it is imperative that research be focused on the generation of appropriate, science-based technologies of wide applicability, especially under resource-poor conditions and in smallholder farming systems. Future research agendas should entail a judicious blending of science and technology. Applied research should build upon the findings of basic research to generate technologies for application at the farm, regional and global levels. Such research should place increased focus on previously neglected subjects, for example, the exploitation of indigenous fruit-producing trees, the agronomic components of agroforestry systems, and the global issues mentioned above. Furthermore, an appropriate methodology that embodies economic, social, and environmental costs and benefits needs to be developed to realistically assess the impacts of agroforestry, and an enabling policy environment that will facilitate agroforestry adoption needs to be made available. Agroforestry research of the 21st century should strive to build bridges from the inductive phase of the past, through the deductive phase of the present, to the future phase of harnessing science and generating technologies for the benefit of the land and its present and future users. This revised version was published online in June 2006 with corrections to the Cover Date.     

Australia's forests: Contested past,tenure-driven present,uncertain future

Australia's forests have been characterized by a history of contestation and conflict since British colonization in 1788. This paper adopts a “pathways to sustainability” approach to review Australia's forest governance models, which are strongly tenure-dependent, and generally vary between sub-national jurisdictions; only climate change-related policies, which are in a state of considerable flux, apply to all forests. Consequently, pathways to sustainability are defined largely in terms of the dominant purpose of particular tenures, and are now little-integrated across institutions, landscapes or tenures. Three decades of trialing devolved models of natural resource governance have effectively been abandoned, as have many of the initiatives intended to support development of a more diverse and more integrated ‘forestry’ sector. While the near-term prospects for sustainability of Australia's forests in anything more than the narrowest sense are poor, there are both knowledge-based and historical institutional foundations from which more substantive progress towards sustainability could be realized. This progress will need to be founded on approaches to policy development and implementation that recognize and accommodate the plurality of interests in forests, that enhance coordination and integration between institutions and across landscapes, and that empower and enable the diverse communities of interests in forests.     

Ecophysiological responses of woody plants to past CO(2) concentrations

An approach is detailed for calculating historical rates of CO(2) uptake and water loss of leaves from measurements of leaf delta(13)C composition and climatic information. This approach was applied to investigate leaf gas exchange metabolism of woody taxa during the past 200 years of atmospheric CO(2) increase and in response to the longer-term atmospheric CO(2) increases plants experienced over the Pleistocene. Reconstructed net assimilation rates and water use efficiencies increased in response to increasing atmospheric CO(2) concentrations in both sets of material, whereas stomatal conductance, showing the combined responses of changes in stomatal density and leaf assimilation rates, was generally less responsive. Woody temperate taxa maintained a nearly constant c(i)/c(a) ratio in response to the increase in atmospheric CO(2) concentrations over both timescales, in part, as a result of changes in stomatal density. The reconstructed leaf-scale physiological responses to past global climatic and atmospheric change corroborated those anticipated from experimental work indicating the adequate capacity of experiments, at least at the scale of individual leaves, to predict plant responses to future environmental change.     

Population dynamics and management of Amazon tidal floodplain forests: Links to the past, present and future

Although tidal floodplain forests represent the oldest commercial logging frontier in the Amazon, tree demography analyses are lacking. Consequently, the accurate evaluation of impacts of past use and the development of ecologically sound forest management has lagged. To address that gap, we combine matrix model methods with data from interviews with tidal floodplain smallholders regarding land use and ecological knowledge. Here we examine the population dynamics of 8 common tidal floodplain species and explore the link between species population ecology and past, present, and future timber use.Despite the generally high timber stocks due to the dominance of Mora paraensis, these tidal floodplain forests offer challenges to management similar to those seen in tropical forests elsewhere, including low recruitment and species-specific tree growth rates, population densities and size distributions. Furthermore, species population ecology and survey results indicate that the long legacy of forest use in the tidal floodplain forests will influence the future of forest use and management, negatively impacting some species (e.g., Virola surinamensis) while likely benefiting others (e.g., M. paraensis). The observed diameter distributions of species least harvested in the past (e.g., M. paraensis, Licania heteromorpha) follow those derived from stable stage distributions. For other historically harvested species (e.g., Carapa guianensis, V. surinamensis), a larger number of harvest-sized trees for most species would be expected under unlogged conditions, a result corroborated by survey results indicating that maximum log size of long-used timber species has decreased over the past decades.While timber extraction in the Amazon Estuary has endured for centuries, our results suggest long-term timber use does not necessarily entail sustainability; a long history of timber harvesting can also indicate a gradual process of resource depletion as preferred species are sequentially exhausted. If current practices are left unchanged, the prospects for long-term management are likely to decrease further as the densities of preferred high-value species (C. guianensis, V. surinamensis, P. filipes) fall to levels that make management economically unattractive.     

Alley cropping: past achievements and future directions

There is a need to develop viable farming systems for tropical uplands dominated by low-activity clay soils; such systems should ensure sustained crop production while protecting the soil resource base. Alley cropping has the potential to meet this need. For over a decade, the alley cropping technique has been tested, with varying results, in various agroecological zones. Results obtained thus far show that the best potential is on the high base-status soil in the humid and subhumid zones, and that crop production can be sustained in this ecozone with low chemical inputs. Further research is needed for other ecozones, particularly with inclusion of better adapted or indigenous hedgerow species. The potential and limitations of the alley cropping technique are highlighted and areas of future research discussed.     

Effects of gaps on regeneration of woody plants: a meta-analysis

Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.     

Tyrosinase inhibitory activity of proanthocyanidins from woody plants

Flavanol values, molecular weight distributions, polyphenolic patterns, and tyrosinase inhibitions of proanthocyanidins (PACs) from karamatsu (Larix sp.) bark, acacia Morishima (Acacia mearnsii) bark, and commercial quebracho (Schinopsis lorentzii) extracts were examined to investigate the relation between the structures of PACs from woody plants and tyrosinase inhibitory activities. Aqueous acetone (70%) extracts of acacia showed high flavanol contents and strong tyrosinase inhibition. On the other hand, the quebracho extracts inhibited tyrosinase activity slightly despite its high flavanol content. Phenyl nucleus analysis by the nucleus exchange reaction provided information that karamatsu, quebracho, and acacia extracts consist of procyanidin, profisetinidin, and prorobinetinidin, respectively. The relation between the phenolic hydroxylation pattern and tyrosinase inhibition suggested that the PACs with a 5,7-dihydroxyphenyl structure in the A-ring and a 3,4,5-trihydroxyphenyl structure in the B-ring have potent tyrosinase inhibitory activity.Part of this paper was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

木本植物转基因研究进展

综述了近年有关木本植物的转基因技术的主要成果,从应用的目的基因、转化方法、受体系统、选择标记系统等方面分别进行了阐述,并探讨了当前木本植物转基因研究存在的问题及未来的发展方向。     

木本植物重金属毒害及抗性机理

主要从重金属对木本植物毒害作用和木本植物对重金属的抗性机理方面,综述了国内外在该领域的研究进展,并分析了现阶段在研究重金属对木本植物的毒害和木本植物对重金属的抗性机理方面存在的问题,提出了今后的研究趋势。     

Measurement of sap flow in roots of woody plants: a commentary

Measurements of sap flow in roots have recently been used to study patterns of resource acquisition by woody plants; however, the various thermometric methods employed have yielded disparate findings. These findings may be harmonized by accounting for the phenomenon of reverse sap flow in roots. We suggest that only methods capable of measuring slow and reverse rates of flow and that do not require assumptions of zero flow during the night are applicable to studies with roots. The heat ratio method and the constant power heat balance method fit these criteria, whereas the constant temperature heat balance, compensation heat pulse and thermal dissipation methods do not.     

Past,present and future of industrial plantation forestry and implication on future timber harvesting technology

Plantation forests are established,and expanding,to satisfy increasing global demand for timber products.Shifting societal values,such as safety,productivity,environmental,quality and social are influencing the plantation forestry sector.This is primarily driven through an ever increasing world population,which in turn influences the way nations view the value systems by which they live.More people require more resources—also forest products.Also,the availability of information is influencing the pace of technological development.These changes could result in a difference in the management of plantations that could affect the forest engineering systems of the future.This review aimed to summarize the current status of plantation forests;summarize future developments and possible scenarios in forest plantation management for the various products;and assess whether these developments in a plantation environment could affect the harvesting systems used.Factors influencing the form of plantations include the type and nature of the plantation owner;the change in demand for different and new forest products;climate change factors,including the use of biomass for energy,carbon sequestration and trading;ecosystem services and other products and services;and sustainability certification of forest management.The impact and influence of these factors were summarised into a series of key drivers that will influence the technology used in harvesting machines,as well as the choice of harvesting machines,systems and methods.These drivers were the effect of variations in tree size,the expansion of plantation areas onto more difficult terrain,diversity in plantation design,increased attention towards site impacts and the increased use of biomass for energy.Specific information is provided regarding how the harvesting systems could be affected.     

金沙县国家级保护木本植物调查初报

通过对金沙县国家级保护的木本植物进行调查,有Ⅰ级保护的木本植物3种,Ⅱ级保护的木本植物4种。     

Tree domestication for agroforestry: present status and future directions

Seven different activities constitute tree domestication: (1) manipulation of tree populations by silvicultural practices; (2) enhancement of site productivity; (3) control of destructive agents; (4) evolution of trees under natural selection; (5) semi-natural selection for survival in the socio-agricultural circumstances in which trees are grown; (6) conscious human selection for desired characteristics; and (7) correlated response to selection (which usually involves reduction of those plant parts that are not desired). Each of these activities is discussed, and its contribution to the present makeup of tree populations used for agroforestry is considered.Although tree domestication has been practiced by farmers for many centuries, selection and breeding programs for multipurpose agroforestry trees have existed for only the past thirty years. Some of the problems faced by existing tree improvement programs are discussed; these include: multiplicity of usable species, great demand for multipurpose trees (MPTs), existence of improvement programs with few species, difficulty of combining desired traits in a multipurpose ideotype, high cost and slow progress with present methods, and the fate of improved material introduced on farms. Among the solutions considered is more involvement of farmers in the process of selection, testing, and propagation of MPTs. The possible use of species mixtures also holds promise.     

木本植物组织培养器官发生植株再生研究进展

综述了我国木本植物组织培养器官发生植株再生研究领域的研究现状，分别从影响木本植物器官发生的主要因子、生理生化基础、遗传变异性以及在基因转化中的应用等几个方面进行了评述，提出了该研究领域目前存在发展不平衡等问题。     

Biological significance of RNA-seq and single-cell genomic research in woody plants

RNA-seq and single-cell genomic research emerge as an important research area in the recent years due to its ability to examine genetic information of any number of single cells in all living organisms.The knowledge gained from RNA-seq and single-cell genomic research will have a great impact in many aspects of plant biology.In this review,we summary and discuss the biological significance of RNA-seq and single-cell genomic research in plants including the single-cell DNA-sequencing,RNA-seq and single-cell RNA sequencing in woody plants,methods of RNA-seq and single-cell RNA-sequencing,single-cell RNA-sequencing for studying plant development,and single-cell RNA-sequencing for elucidating cell type composition.We will focus on RNA-seq and single-cell RNA sequencing in woody plants,understanding of plant development through single-cell RNAsequencing,and elucidation of cell type composition via single-cell RNA-sequencing.Information presented in this review will be helpful to increase our understanding of plant genomic research in a way with the power of plant single-cell RNA-sequencing analysis.