Breeding systems – diverse
Trees are also notable for their diverse breeding and reproductive systems, which are in turn major determinants on spatial patterns of the tree species genetic diversity. Most tree species reproduce sexually, although many have a combination or sexual and asexual reproductive means, while a few have lost the ability to reproduce sexually and are maintained as sterile, root-suckering clones in certain parts of their range, e.g. Chittering grass wattle (Acacia anomala) in south-western Australia (Coates, 1988), swamp sheoak (Casuarina obesa) in western Victoria (Australia), and Eastern Polynesian sandalwood (Santalum insularis) on Mangaia (Cook Islands). It is possible that a long distance pollen or seed dispersal event to such plants might lead to their regaining a sexual mode of reproduction. Trees species reproducing by sexual means have diverse reproductive biologies including monoecious (separate male and female flowers on the same tree), dioecious (individual trees may bear either male or female flowers), hermaphroditic (functional bisexual flowers) and polygamous (with male, female and bisexual flowers on the same tree). Almost all flower sex combinations are possible including trees with male and bisexual flowers; female and bisexual flowers and with both bisexual flowers and small number of either male or female flowers. At a global level, populations of flowering plant species are mainly hermaphrodite (72%), with a variable proportion as monoecious (4%), dioecious (7%), gynodioecious or androdioecious (7%) and trioecious (10%) (Yampolsky and Yampolsky 1922; Dellaporta and Calderon-Urrea 1993), but these rates will vary regionally and between trees and other flowering plants, e.g. dioecy, an obligate outcrossing pollination arrangement, was found to be higher (>20%) in tree species (Bawa et al. 1985). The majority of angiosperm species with hermaphroditic flowers have preferential out-crossing systems such that fertilized, viable seeds are generally derived from outcrossing. Reported outcrossing rates4 in tropical angiosperm tree species in different families, and including those occurring at low density, found outcrossing rates typically were in the range 60 to 100%, but with considerable variation. Outcrossing rates vary within species, populations and between different flowering events. For example tropical acacias from humid zones in Papua New Guinea and northern Australia typically have rates of 93-100% outcrossing, but lower rates (30-80%) have been found in more southerly populations of mangium (Acacia mangium), while polyploid dry-zone African acacias had low outcrossing rates of between 35-38%. Plasticity in mating systems has also been observed in response to changes in pollinators, e.g. kapok tree (Ceiba pentanda) had predominantly self-incompatible system in regions with high bat pollinator visitation, but changed to a mixed mating system with high levels of self-pollination in situations with low pollinator visitation rates (Lobo et al. 2005). Conifers are wind pollinated and either monoecious or dioecious (obligate outcrossing): species in the families Araucariaceae, Podocarpaceae and Taxaceae may be either monoecious or dioecious; Pinaceae and Cupressaceae are monoecious (with the exception of Juniperus which are usually dioecious); and Cephalotaxaceae are dioecious or occasionally monoecious (The Gymnosperm database; http://www.conifers.org accessed November 2012). Mating systems in conifers vary in space time, mainly due to variation in self-pollen availability (Mitton, 1992). Mechanisms to promote outcrossing have been identified in monoecious conifers, e.g. loblolly pine (Pinus taeda; Williams et al., 2001), and the outcrossing rate for most conifer species is above 80% (for the 52 species reviewed in O’_onnell, 2003)/ Through their long evolution plasticity in the reproductive systems of conifers may have helped them to survive, e.g. Saharan cypress (Cupressus dupreziana) has evolved a unique reproductive system of male apomixis whereby the seeds develop entirely from the genetic content of the pollen (Pichot et al., 2000). Coast redwood (Sequoia sempervirens) reproduces by both asexual (basal suckering) and sexual means but with low seed set (1-10%) due to irregular meiosis and associated with its hexaploid condition; dual reproductive systems have enabled redwoods to maintain heterozygosity and adaptability for survival (Ahuja 2005).
1.1.3 Types and complementarities of FGR conservation
Conservation of forest genetic resources can be defined as the policies and management action taken to assure their continued availability and existence. The strategy of conservation and the exact methodologies applied depends on the nature of the material, the timescale of concern, and the specific objectives and scope of the programme. There are two basic strategies for genetic conservation: these are in situ (on site) and ex situ (off site, e.g. in designated conservation stands/field gene banks, genebanks, arboreta and botanic gardens). These two strategies are generally viewed as being complementary and best carried out in parallel in the case of conservation of species and intra-specific genetic variation. However this presents major organizational, institutional, regulatory and technical challenges due to the different types, ownerships and dynamics of repositories of FGR (Sigaud et al. 2004). A highly coordinated approach is required between the various concerned agencies and organizations, viz. Forestry Departments for managing reserved forests and in situ gene conservation stands; Environment Departments managing protected areas; Government Agencies and Private forestry companies and cooperatives for tree improvement programs; Government Research Agencies, Botanical Gardens and Universities maintaining gene banks of seed and tissue cultures; private landholders and communities managing privately owned managed forests, plantations, agroforests and farmlands. Both the general and particular strategies and programs to be pursued will be dependent on factors such the available financial, human and land resources; human population and resource use pressures on land, forests and trees; technological options for particular species and the nature and dimensions of the conservation challenges, e.g. whether the aim is to conserve a large number of forest species, a smaller number of rare and endangered species or to conserve the genetic diversity and evolutionary potentials of a smaller number of high priority species for planting programs. Additional challenges and opportunities arise in situations where there is an international dimension, e.g. for species with natural ranges which cross national borders (or even state/provincial borders); in cases where a species may be much more economically important as a planted exotic than in its own country and native habitats; and opportunities for ex situ conservation in wellresourced facilities (tree seed banks, tissue culture facilities etc).
The management of forest genetic resources to simultaneously ensure their conservation, improvement and sustainable use is a complex technological and managerial challenge. Fortunately, when simple basic principles are applied, the production of goods and services from managed forests forming part of a legislated permanent forest estate is generally compatible with the genetic conservation and development of particular forest tree species, as discussed in section 1.1.5.
There are four quite different, but complementary, approaches and actions which are making important contributions to conservation of forest genetic resources. These are:
1. Targeted species based approaches, typically highly resource intensive, and which aim to conserve as much intraspecific diversity as reasonably possible for high priority forest tree species (SP 11). The main reason for high priority rating is that the particular species is of major national and/or international economic importance. A species based approach may also utilized for endangered tree species, but in these cases the intensity of genetic conservation effort is less and directed towards maintaining enough diversity, in preferably more than one population, to ensure the species survival. In the ideal species-based conservation plan the distribution of the species intraspecific diversity and associated relevant factors will be well known. Populations for conservation are selected on the basis of most efficiently and securely conserving as much genetic diversity as possible including rare alleles and co-adapted gene complexes of identified high value populations/ seed sources, in a network of managed in situ FGR reserves. For species exhibiting clinal variation, connectivity and gene flow between populations would be maintained through vegetation corridors and/or linked by circa situm plantings. In many instances implementation will involve a diverse group of land managers and interested parties, and in some cases international collaboration. Ideally safety duplication of the material conserved in situ would also be undertaken through ex situ methods, such as long term seed storage banks for species with orthodox seed storage behaviour, and through tissue culture banks and field gene banks for species with recalcitrant seed storage behaviour. Despite this approach having major benefits and having been widely promoted by FAO and forest geneticists over the past thirty or more years, there are few examples where it has been implemented, and these are mainly restricted to developed countries in Europe and North America e.g. Norway spruce (Picea abies) in Finland (Koski 1996), but with only a few documented cases in tropical countries, e.g. Sumatran pine (Pinus merkusii) in Thailand (Theilade et al. 2000). Since 2007, considerable preparatory work for many species in 36 European
countries has been undertaken through _ioversity’s European Information System on Forest
Genetic Resources (EUFGIS), including through creation of a network of a national network of FGR inventories and development of minimum requirements for dynamic conservation units of forest trees.
2. Large scale, long term ex-situ conservation in seed banks for tree species with orthodox seed storage behaviour (SP 7). Many countries have national tree seed banks but these are usually active collections, with rapid turnover and use of collected seedlots and in which conservation is a supplementary or incidental benefit, e/g/ _SIRO’s !ustralian Tree Seed _entre/ ! major international example of this conservation strategy for trees and woody species is the Kew Millennium Seed Bank Partnership, based in Wakehurst, UK (http://www.kew.org/scienceconservation/save-seed-prosper/millennium-seed-bank/about-the-msb/index.htm and see section 1.1.6). This partnership covers about 50 countries, and has already successfully banked 10% of the world's wild plant species, including many woody species, and has an objective of conserving 25% of the world’s wild plant species by 2020/ !n example of this partnership in action is in Burkina Faso where the National Forest Seed Centre (CNSF) has 160 tree species in long-term cold storage (Burkina Faso p 2 and 22).
Ecosystem-and landscape-based conservation approaches and management regimes which either aim to, or sometimes incidentally, conserve in situ a wide array of forest tree species and their diversity (SP6). These approaches are devoid of a particular tree species focus unless the tree species has been identified as a keystone species whose continued existence and diversity are vital for maintaining the ecosystem’s health/ These management regimes are well-suited to areas with high tree species diversity, such as lowland tropical rainforests. In locations where local human populations are reliant on a vast number of tree and woody species to provide diverse products, then managed multiple-use production forest systems. This approach can ensure the continued survival and availability of large numbers useful tree species which may have localised and/or potential importance. Fully protected areas systems will only likely succeed in the longer term in areas of low population pressure.
Conservation through planting and use (SP9). Increasingly many socio-economically important tree species are being conserved through use, often planted for productive and other purposes in plantation forests, agroforests, orchards and urban landscapes (home gardens, parks and street trees). The conservation of FGR in these cases is often incidental, unplanned, and suboptimal; an exception is breeding programs and seed orchards which are often designed with maintaining a balance of diversity and improvement. There are opportunities to conserve substantial tree species diversity (including within species diversity), in for example urban landscapes, farms, hotel resorts, golf courses etc if managers of these areas could be made aware of the importance of such activities and linked into national FGR programs.
1.1.4 Forest Cover
The Global Forest Resources Assessment 2010 (FAO, 2010) provides a comprehensive assessment of the world’s forests/ Some of the major findings of FRA 2010, with notations on impacts and considerations for FGR5, are as follows:
The world’s total forest area is just over four billion hectares, with the five most forest-rich countries (the Russian Federation, Brazil, Canada, the USA and China) accounting for more than half of the total forest area. The rate of deforestation – mainly from the conversion of tropical forest to agricultural land shows signs of decreasing, but is still alarmingly high. Around 13 million hectares of forest were converted to other uses or lost through natural causes each year in the last decade compared with 16 million hectares per year in the 1990s. Two countries with biodiverse and FGR-rich forests, viz. Brazil and Indonesia, which had the highest net loss of forest in the 1990s, have significantly reduced their rate of loss and this will also entail a slowing in rate of loss of tree species and populations.
At a regional level, South America suffered the largest net loss of forests between 2000 and 2010 – about
4.0 million hectares per year – followed by Africa, which lost 3.4 million hectares annually. Both regions are rich in tree species and FGR, and such forest loss would be accompanied by an irreplaceable, but poorly documented loss, of valuable FGR. Oceania also reported a net loss of forest (about 700,000 ha per year over the period 2000–2010), mainly due to large losses of forests in Australia, where severe drought and forest fires have exacerbated the loss of forest since 2000. The area of forest in North and Central America was estimated as almost the same in 2010 as in 2000. The forest area in Europe continued to expand, although at a slower rate (700,000 ha per year) than in the 1990s (900,000 ha per year). Asia, which had a net loss of forest of some 600,000 ha annually in the 1990s, reported a net gain of forest of more than 2.2 million hectares per year in the period 2000–2010, primarily due to the large-scale afforestation reported by China. Whilst the forested area has been increasing in Asia, this is masking a loss of valuable FGR (both species and especially populations of useful tree species) from shrinking native forests in many countries in south and south-east Asia. Primary forests, which include some of the most FGR-rich forests, account for 36 percent of the global forested area, but have decreased by more than 40 million hectares since 2000 with, in most cases, a permanent loss of associated forest genetic resources. It some cases the forest cover estimates have varied from FR! 2005 due to changes in the criteria used for assessment, e/g/ Ethiopia’s forest cover jumped to 11% (from 3.5%) in the 2010 FRA assessment on inclusion of high woodland areas into forested area (Institute of Biodiversity Conservation, 2012), but during this period there has been increased human pressures and severe drought impacts on Ethiopia’s tree resources/
Around the globe the area of planted forest is increasing and now accounts for seven percent of total forest area, with the highest proportion in Asia (almost 20%). These figures underscore the need to carefully consider the genetic materials being used to establish planted forests, and for forests regenerated artificially or with human management. There is a need to ensure such forests are utilizing appropriate, diverse, adapted (including for predicted new climates) and useful genetic materials and that information on the genetic makeup is being well-documented. There is also a need for safe movement of germplasm to ensure that pests and diseases are not inadvertently introduced, especially as forest tree species may be more vulnerable to pests and diseases due to climate change. Regionally and sub-regionally there are large differences in the proportion of planted forest consisting of exotic species, from a very high proportion of exotics in Eastern and Southern Africa (100%), South America (97%), Central America (81%), Oceania (77%), Western and Central Africa (70%) through to very low proportion of exotics in North America (2%) and arid regions, such as Western and Central Asia (4%) and North Africa (7%). This data underscores the need for continued and increased international collaboration in the conservation, exchange and benefit sharing of tree germplasm and FGR.
FRA 2010 is a treasure-trove of useful data on forest distribution and their status, including on matters impacting on FGR conservation and management for example type of regeneration method, indicators of sustainable forest management, extent of permanent forest estate and protected area. This first SoW-FGR is complementary to the FRA process, and annual State of the World Forests reports, given that forest cover and related data cannot be used as a surrogate for assessment of the status of FGR, and will help to differentiate between the state of the world’s forest resources and the genetic resources on which they depend for their utility, adaptability and health.
1.1.5 Management systems in the field (including in situ and circa situm conservation of FGR)
“Sustainable forest management of both natural and planted forests and for timber and non-timber products is essential to achieving sustainable development and is a critical means to eradicate poverty, significantly reduce deforestation, halt the loss of forest biodiversity and land and resource degradation, and improve food security and access to safe drinking water and affordable energy…The achievement of sustainable forest management, nationally and globally, including through partnerships among interested Governments and stakeholders, including the private sector, indigenous and local communities and non-governmental organizations, is an essential goal of sustainable development…” (Paragraph 45, Plan of Implementation, Report of the World Summit on Sustainable Development).
The sustainable utilization of timber and non-wood forest products (NWFP) from forests, without depletion of the supporting FGR, is becoming increasingly challenging, notably in the context of heavily-populated, developing countries many of which suffer poverty and chronic famine6. Limited options for economic development and an imperative to focus on immediate needs, promotes short-term perspectives in the use and management of natural resources, including forests and the FGR on which they depend. The global population continues to increase7, especially in tropical developing regions and placing additional pressures on forests. There are estimated to be around 400 million people dependent or highly reliant on forests for their livelihoods8. Whilst there is a marked trend towards increasing urbanization of human populations9 the movement of people into cities does not much diminish their needs for wood and fibre for building, fuel, paper; NWFPs and agroforestry tree products (AFTPs) such as herbal medicines and foods. Forest genetic resources conservation and management in the field, should ideally, be considered and integrated into all land uses and management systems containing trees, the most important of which are sustainable managed multiple-use production forests, protected forests, and agro-forests10.
FGR in sustainably managed multiple-use production forests
Sustainable forest management involves the management of forests in a manner that ensures that their overall capacity to provide environmental and socio-economic benefits is not diminished over time. Central to the sustainable development of forests is the challenge of balancing resource use and conservation. Sustainable forest management and the maintenance of FGR are best considered as interdependent: the essential underpinning role of FGR in forest and natural resources management practice needs to be better understood and appreciated by forest owners, custodians and managers in order that they will implement effective interventions for their conservation and use. In many cases, the management measures for maintaining diversity in forest ecosystems and for simultaneously promoting the sustainable use of this diversity have been developed and are known (see for example, FAO 1993; Thomson 2004). What is lacking is their constant application and monitoring. Furthermore, harmonizing conservation objectives and utilization practices in production-oriented, multiple-use native forests will be essential for conservation of the diversity of the majority of tree species, given that they are not well represented in protected areas, plantations and ex situ collections (Thomson 2004).
Technologies for sustainably managing and utilizing native forests without diminishing, and preferably enriching, their FGR have been traditionally practiced through diverse indigenous forest management systems and practices. FGR management practices are able to be readily integrated into modern silvicultural systems by forest agencies and/or private forestry companies. However in many parts of the world, tree species diversity and intraspecific diversity, is declining because best practice forest management systems are not being implemented or are breaking down for various reasons.
Traditional forest and woodland management systems are coming under increased pressures, viz. more people per unit of available forest, resulting in tree resources being harvested and used unsustainably, including overharvesting of timber, fuelwood and NWFPs; reduction in seed sources of pioneer and early secondary trees and not enough time for deep-rooted perennial vegetation to replenish soil fertility in-between shortened fallow periods. Selective overharvesting, much of it illegal, and leading to extinction of the highest value species in the forests is a major and increasing problem intertwined with rural poverty. Tree being harvested include both high value timbers such as Thai rosewood (Dalbergia cochinchinensis) species in Thailand and Indochina, African blackwood (Dalbergia melanoxylon) in sub-Saharan Africa and red sandalwood (Pterocarpus santalinus) in India, and those producing valuable NWFPs, such as massoia (Cryptocarya massoia) in New Guinea (bark for massoia lactones for food industry), African cherry (Prunus africana) in Afromontane forests (bark for treatment of benign prostrate hypertrophy), sandalwoods (heartwood of certain Santalum and Osyris spp. for essential oils) in India, Indonesia, Timor Leste and the Pacific Islands and Himalayan yew tree (Taxus contorta for production of taxol, a chemotherapy drug to treat cancer) in Afghanistan, India and Nepal.
Harvesting of wood resources for fuelwood and charcoal is often less discriminatory but can lead to permanent loss of tree species and locally adapted populations, reducing options for future recovery either by natural or human-mediated means from the associated environmental degradation. For example, severe deforestation is taking place in Somalia to provide income for the militant group al-Shabaab: this includes elimination of ecologically important tree species such as Acacia for charcoal, along with selective harvesting and loss of the highly valuable frankincense (Boswellia spp.) trees. In north-east Thailand, high rates of drug addiction in some villages have resulted in increased charcoal production and unsustainable resin harvesting from dipterocarps and pines in adjacent forests to pay for the illicit drugs, threatening Thai Forestry Department efforts to conserve unique lowland populations of Sumatran pine (Pinus merkusii).
FRA 2010 reported on broad progress towards sustainable forest management since 1990 and found that at the global level the situation has remained relatively stable. The 2010 assessment did not include species or population-level indicators suitable for a global comparison of trends over time and therefore does not directly report on FGR. The biological diversity theme was covered through reference to: the area of primary forest, areas designated for conservation of biological diversity and area of forest in protected areas. The results for forest biodiversity conservation were mixed, with the area of primary forest recording one of the largest negative rates (in percentage terms) of all measures, and declining by between 4.7 million hectares per year during the 1990’s and 4/2 million hectares per year between 2000-2010. The area of forest designated for conservation of biological diversity increased by about 6.3 million hectares per year during the last decade with a similar increase in the area of forest in protected areas. The area under production forests, and considered equally vital for conservation of FGR, has continued to decline at an increasing rate, by about two million hectares per year during the 1990s and three million hectares per year between 2000 and 2010.
FRA 2005 reported that globally 80% of world’s forests are under public ownership and that 80% of
publicly-owned forests are under public administration. This data would suggest that National Governments are in a strong position to directly influence and control forest management practices. However, in the developing tropics, many production forests are under private logging concessions, and Governments frequently lack resources to develop and enforce sustainable best practices by private operators, such as codes of logging practice and reduced impact logging guidelines. The problem is compounded where concessions are issued for a short term or once-off, as the logging concessionaire will harvest in a manner that will maximise profits from the logging operation, with less or little consideration for regeneration and subsequent harvests.
In future sustainable production of goods from native forests will be increasingly challenged by predicted more extreme climatic events, the most severe of which for forest products will include more intense tropical cyclones, droughts and associated bushfire, intense rainfall events with landslips and flood, and melting of permafrost. There will also be interactions of climate change with existing and new pests, diseases and invasive weeds, and on pollinators and dispersers, which will impact on production, selective forces and the future forest composition. The genetic diversity contained within and among tree species will provide an essential buffering for these impacts on many forest productive and service functions, but may require a much greater level of management intervention and manipulation, including movement of tree germplasm to respond to new climates, changed pest and diseases and new selective pressures.
Sustainable forest management cannot by itself ensure conservation of all FGR. There are tree species and populations that require special and immediate attention, as well as many species of no or little current utilitarian value that the forest manager probably will not be able to attend to. Some of these lesser-known or less economically important species may depend on complicated ecological interaction and may suffer from what at present is believed to be gentle utilization of the forest resources. Therefore, an integrated approach encompassing management of natural stands and establishment of specific conservation populations is advocated.