Forestry practices that maintain genetic diversity over the longer term will be required as an integral component of sustainable forest management

Yüklə 0.55 Mb.
ölçüsü0.55 Mb.
1   2   3   4   5   6   7   8   9   10   11

1.2.4 Preserving future development options

One of the most important values and characteristics of FGR is that they will be vital for preserving future options, some of which are becoming all-too-evident such as coping with climatic extremes and adapting to the new warmer climates brought about increases in atmospheric CO2, but others for which we may currently have little idea. Based on geological records, the Earth is likely to return to a new period of glaciation possibly 3,000 to 20,000 years hence, but the impact of longer term impacts of current human-induced warming on global climate on a future glaciation event are unknown. In the meantime it would be reprehensible if we allow useful tree species and populations adapted to cooler climates to become extinct from global warming and other factors when their germplasm might be safely and relatively cheaply conserved long term in cool storage such as the Svalbard Global Seed Vault in Norway, i.e. for several hundred to thousands of years at −18oC.

The importance of maintaining FGR for preserving options applies to both natural forests, where a key dimension is capacity to adapt to changing environments, as well as planted forests where the key dimensions may be the need for new products and services while and at the same time proving resilient. In the case of planted forest tree species, there is a need to maintain as much intraspecific diversity as possible to allow tree breeders to continue to select and develop improved and adapted germplasm to cope with new demands and growing conditions. This might include development of new wood products and NWFPs, especially pharmaceuticals and neutriceuticals, such as sources of antioxidants, antiinflammatories and other chemo-protective natural compounds. There may be novel uses such as specifically breeding trees to sequester carbon, recycle plant nutrients from beyond crop root depth, or to ‘harvest’ precious minerals through phytomining, e.g. Wood and Grauke (2010) have found that tetraploid hickory (Carya) species are high accumulators of rare earths (almost 0.1% dry weight) and much higher than diploid Carya species, and non-Carya tree species. In New Caledonia, several hypernickelophore tree species, including Geissois pruinosa and Homalium kanaliense can accumulate the valuable metal nickel to up to 1% of leaf dry mass (Boyd and Jaffré 2009). The differential ability of plants to accumulate gold is also well known, e.g. Girling and Peterson (1980), but has not been commercially exploited to date. In future certain tree species and genotypes might be used or selected and bred for phytoremediation, viz. to remove or neutralize contaminants, as in polluted soil or water (e.g. Raskin and Ensley 2000; Pilon-Smits 2004).

In summing up it is evident that well-characterized12, genetically diverse wild populations (or provenances) of different tree species will provide extremely useful genetic materials both for immediate planting programs and as the basis for any future selection and improvement programs. The diverse values and uses of forests and trees and FGRs identified in country reports underscore the need for national FGR strategies, and effective programmes and action plans to address not only the applications and requirements of the formal forests and forest industry sectors, but also their roles in the informal economy, the alleviation of poverty, in social, cultural, religious and identity areas, and their role in environmental services and rehabilitation. The major contribution of FGR to the informal economy highlights the need to consult with the widest range of forest users possible when preparing national strategies and programmes. Development of appropriate policy tools to provide a national framework for action and strengthening of institutional capacities constitute a fundamental strategic priority for conservation and sustainable use of FGR.

1.3 Between and within species diversity

Most of this SoW-FGR report deals with intraspecific diversity, but it is also appropriate to consider the economic and other uses of trees and woody shrubs provided through diversity at species level. Indeed the future wellbeing of the human race, and the health and productivity of various ecosystems and communities, will often be reliant on genetic diversity both within and among tree species. A concise treatment of interspecific tree diversity (or diversity among and between tree species) follows, while Annex XXX provides a review on uses, products and services provided by different tree and woody shrub species, organized by phylogenetic relationship in plant families, throughout the globe.

1.3.1 Interspecific diversity (between species)

Trees and woody shrubs exist in two major groups of seed-bearing plants, viz. gymnosperms (cone-bearing plants) and angiosperms (flowering plants), with angiosperms having evolved and radiated into vastly more families, genera and species, including about 250,000 living species according to Kenrick (1999) over the past 290 million or so years. Approximately 80,000 to 100,000 tree species have been described and currently accepted as valid and unique: and together with larger woody shrubs they likely represent about 50% of all vascular plant species. Considerable research has been undertaken to understand how tropical forests develop and maintain their typically vast tree species diversity but answers remain elusive (e.g. Denslow 1987; Cannon et al. 1998; Ricklefs and Renner 2012). Tree diversity in complex ecosystems may not only be maintained, but may also have been in part generated, by host-pathogen and host-parasite interactions (Wills et al. 1997), as well as diversity in rainforest gaps or regeneration niches (Grubb 1977).

Research, development, conservation and utilization of tree species, in particular tropical species, has often been frustrated by insufficient and inadequate taxonomic knowledge, e.g. assessment of conservation status of different species (Newton and Oldfield 2008). Increasingly an array of more powerful and efficient genetic technologies is available to complement traditional, morphological-based, taxonomy and field studies. This is leading to a better circumscription of tree species and understanding of their phylogenetic relationships. The nature of variation in trees is such that species boundaries will not always be readily defined, including for example: species existing as morphologically distinctive and geographically disjunct populations which rarely exchange genetic materials and are best considered as provenances, varieties or sub-species; species which are readily discernible in most of the natural range, and have evidently been reproductively isolated for much of the recent evolution, but which form fertile hybrid swarms in small overlapping contact zones; species with polyploid races, often coupled with apomictic reproduction; and ochlospecies whose complex variation patterns cannot be satisfactorily accounted for by conventional taxonomic categories (Whitmore 1976).

Based on literature reviewed in preparing Annex XXX it is conservatively estimated that there are more than 34,000 tree species13 in more than 1000 genera that are of socio-economic, environmental and scientific importance and utilized on a regular (daily or weekly) basis by peoples throughout the globe. This number is comprised of both angiosperms (33,500 species in 976 genera and 131 families, including bamboos and palms) and gymnosperms (530 species in 67 genera and nine plant families, excluding cycads).

In total 7941 species and subspecies were mentioned in Country Reports (Figure 1) and 2363 species and 2363 subspecies were mentioned as being actively managed in various systems (Figure 2).

Figure 1: Number of species and subspecies mentioned in Country Reports, total number and by region

Figure 2: Number of species mentioned as actively managed in Country Reports, by region

In practice, this vast diversity at species level in trees means that, for a given product like wood (e.g. fuelwood or timber) or service, local people and foresters may have the choice between hundreds of species, which are locally available and/or suitable options in different ecological conditions as illustrated by Figure 3. As well as providing opportunities this vast species genetic resource can throw up challenges for ascertaining which species to prioritise for R&D and replanting. In north-east Thailand a framework species selection approach was adopted to identify a small number of local tree species for revegetation, from more than 350 local tree species, so as to most efficiently restore forest cover and catalyse return of biodiversity, and regeneration of hundreds of other tree species (Elliot et al. 2003).

Figure 3: Number of species mentioned as actively managed in Country Reports: total number and by main management objectives

Conservation of FGR, including a vast diversity at the tree species level, is seriously hampered by a lack of taxonomic skills, inventory and knowledge of species distributions as indicated in many country reports. Accordingly there is an urgent and ongoing need to strengthen national FGR assessment, characterization and monitoring systems.

1.3.2 Intraspecific diversity (within species)

Intraspecific diversity or genetic diversity within tree species can be characterized at different levels and is manifested in different ways. These include at a molecular level through nuclear DNA (such as RAPD Random Amplified Polymorphism DNA – neutral markers), chloroplast DNA (especially useful for providing evolutionary information), direct RNA sequencing (providing information on gene regulation and proteins) and enzyme variation (gene products assessed through isozyme electrophoresis). Genetic variation is also observed at expressed levels such as through quantitative variation in growth and other traits as assessed through field trials, and including morphological, physiological, entomological and pathology studies. Sometimes variation is discontinuous, giving rise to the identification of varieties including chemotypes, morphotypes and alike. Intraspecific patterns of genetic variation in tree species have been found to vary due to factors such as the evolutionary history of the species; distribution of populations and connectivity; reproductive biology and mating system; dispersal of pollen and seed; introgression and hybridization with related species; chance factors and genetic drift. Observed patterns of genetic variation can vary between different genomes of the same tree species, if inherited differently, and with associated differences in dispersal of pollen and seed, e.g. Japanese beech (Fagus crenata) in Japan (Tomaru et al. 1998).

Humans have long been interested in utilizing and influencing tree diversity, especially tree species producing edible fruits and nuts, e.g. domestication and selection of walnut (Juglans regia) in Azerbaijan (p 22). Another well-documented case is the selection, translocation and domestication of tropical nut trees in Melanesian arboricultural systems in Papua New Guinea and Solomon Islands and dating more than 3,000 years (Yen, 1974; Lepofsky 1992; Lepofsky et al. 1998). However, the vast majority of traditional knowledge and improvement of FGR is undocumented and national-level assessments are needed a priority, especially in tropical countries, and before the information dies out with the holders of such information.

The forestry profession has had a long-time interest in studying and utilizing variation in trees, including investigations of geographic variation in economically important planted forest tree species through field trials, e.g. IUFRO coordinated provenance trials of Scots pine (Pinus sylvestris) established in 1907, 1938 and 1939 in Europe and the USA (Wright and Baldwin 1957, Langlet 1959, Giertych 1979). After the hiatus of World War II, provenance field trial research recommenced with earnest, e.g. ponderosa pine (P. ponderosa) provenance trials established in USA in 1947 (Callaham 1962) and new P. sylvestris provenance trials in Sweden from 1952-1954 (Eiche 1966; Erikkson et al. 1976). During the 1960’s and 70’s, assessments of genetic diversity in forest tree species gathered pace and extended to tropical and southern Hemisphere species: these assessments were focussed mainly on morphological attributes including wood traits, adaptiveness, quantitative growth characters, disease tolerance, and genotype x environment interaction. This information was determined through series of field trials, often undertaken in several countries and referred to as provenance trials. Some of the tree species studied in these early investigations included yellow birch (Betula alleghaniensis; Clausen 1975), cordia (Cordia alliodora; Sebbenn et al. 2007), river red gum (Eucalyptus camaldulensis; Lacaze 1978), Timor mountain gum (E. urophylla; Vercoe and Clarke 1994), European beech (Fagus sylvatica; Giertych 1990), gmelina (Gmelina arborea; Lauridsen et al. 1987), khasi pine (Pinus kesiya; Barnes and Keiding 1989), patula pine (P. patula; Barnes and Mullins 1983), radiata pine (P. radiata; Nicholls and Eldridge 1980), teak (Tectona grandis; Lauridsen et al. 1987), and limba (Terminalia superba; Delaunay 1978). Based on the success of the earlier provenance trials, the provenance trial approach has been continued and extended, including to national trials with native species – some examples include mulga (Acacia aneura; Ræbild et al. 2003a), ear-pod wattle (A. auriculiformis; Awang et al. 1994), Senegal gum acacia (A. senegal; Ræbild et al. 2003b), red alder (Alnus rubra; Xie 2008), neem (Azadirachta indica; Hansen et al. 2000), beach sheoak (Casuarina equisetifolia; Pinyopusarerk et al. 2004), chukrasia (Chukrasia tabularis; Ratanaporncharern 2002), Melanesian whitewood (Endospermum medullosum; Vutilolo et al. 2005), gao (Faidherbia albida; IRBET/CTFT 1985-88), pochote (Pachira quinata; Hodge et al. 2002), Caribbean pine (Pinus caribaea; Hodge and Dvorak 2001), pinabete (Pinus tecunumanii; Hodge and Dvorak 1999) and chicha (Sterculia apetala; Dvorak et al. 1998).

Country reports tabulated species/provenance trials, often extensive, which have been undertaken.

However, a good many of these trials are in progress or not yet mature, and haven’t been reported and readily available in the published scientific literature. Bulgaria’s research has been focussed on 38 tree species, including 57 provenance trials. Canada reported 983 provenance tests comprising 7,493 provenances that have been established for 41 forest tree species and hybrids, eight of which are exotic. In recognition of their wide planting in reforestation programs, six native species have been extensively tested both nationally and provincially, viz. white spruce (Picea glauca), black spruce (Picea mariana), jackpine (Pinus banksiana), lodgepole pine (Pinus contorta var. latifolia), Douglas fir (Pseudotsuga menziesii) var. menziesii, and western hemlock (Tsuga heterophylla). China commenced provenance trials in the early 1980s and has now conducted trials for more than 70 important planted species such as Asian white birch (Betula platyphylla), Chinese fir (Cunninghamia lanceolata), Dahurian larch (Larix gmelinii), Prince Rupprecht's larch (Larix principis-rupprechtii), Korean spruce (Picea koraiensis), Chinese white pine (Pinus armandii), Masson’s pine (Pinus massoniana), Korean pine (Pinus koraiensis), Chinese red pine (Pinus tabuliformis), Yunnan pine (Pinus yunnanensis), oriental arborvitae (Platycladus orientalis), Chinese white poplar (Populus tomentosa), tzumu (Sassafras tzumu), Chinese coffin tree (Taiwania cryptomerioides), Siberian elm (Ulmus pumila) and various key exotic species (China p 11-13). In Madagascar (p 14) provenance trials of important and promising forest plantation species, mainly exotics, have been undertaken for Acacia spp, Cupressus lusitanica, Eucalyptus spp., Khaya madagascariensis, Liquidambar styraciflua, Pinus spp. and Tectona grandis.

Provenance/progeny trials continue to be undertaken amongst the first steps in domestication and improvement of wild tree species: the range of attributes being assessed is diversifying depending on the particular envisaged and sometimes specialist end uses, such as pulping and fibre properties, timber uniformity, as well as wood and leaf essential oils, fruit and nut characteristics for multipurpose species. There has been a continual increase over the past two decades in the number of species being developed in tree improvement programs, especially in response to wide interest in utilising native species in planting programs and utilizing the approaches and technologies developed for exotic species. For major industrial timber plantation species the improvement work has been undertaken through private sector and tree-breeding cooperatives, whereas early domestication and less intensive improvement of a broader range of species is being undertaken by National Forestry Departments, often in association with NGOs, and with international donor support or organizations such as ICRAF.

Internationally coordinated provenance trials of tree species will become increasingly important in providing data to better assess the modelled impacts of climate change on plantation productivity and to determining which species/provenances will be best adapted to the new and modified climates, e.g. Booth et al. 1999, Leibing et al. 2009 (SP15). Provenance trial data can also be used to assist interpretation of the likely impacts of predicted climate change on native species and populations, e.g. for Pinus species in tropical Asia and Americas; van Zonneveld et al. 2009ab, and for Eucalyptus species in Australia where minor changes in climate will expose at least 200 Eucalyptus species to completely new climatic envelopes (Hughes et al. 1996) and for which their adaptation potentials are unknown.

Increasingly, and gathering momentum over the past twenty years, detailed genetic information is being obtained for tree species often selected for study on the basis of their economic importance, conservation status or for use as representative model species. Many of the early molecular studies of diversity in tree species, in 1980s and 1990s, focussed on high priority timber trees and were mainly undertaken in forest genetic laboratories in developed countries using electrophoresis techniques. Detailed genetic evaluations using DNA and enzyme markers have now been undertaken for many important forest tree species in Europe and North America (e.g. Canada tabulated intraspecific genetic studies for 28 Canadian tree species). Until recently, in most developing countries there have been few detailed studies of intraspecific genetic variation. Such studies are needed for the formulation of scientifically-based gene conservation programs. Increasingly as evidenced in the scientific literature (and reported in country reports prepared for SoW-FGR) the patterns of genetic diversity for a much greater range of tree species, and from throughout the globe, are being determined and using a wide range of genetic markers, e.g. Thai tree species, Chantragoon et al. (2012) and more than 100 tree species in China over the past decade. In Burkina Faso, shea (Vitellaria paradoxa subsp. paradoxa), néré (Parkia biglobosa), tamarind (Tamarindus indica), palmyra (Borassus aethiopium) baobab (Adansonia digitata), Senegal gum acacia (Acacia senegal) and marula (Sclerocarya birrea), have been studied with intra-specific methods from simple description morphological characters of the organs by enzyme electrophoresis or neutral markers of DNA (RAPD).

The planning of specific and efficient programs to both conserve and exploit the genetic diversity in target forest tree species requires a detailed knowledge of the species patterns of intraspecific diversity, notably a knowledge of how genetic diversity is distributed between and among populations (genetic snapshot), and complemented by a knowledge of the species ecology, especially regeneration ecology, reproductive biology and including relationships with other species, including pollinators, dispersers, symbionts, predators/parasites and competitors; in short the selective and evolutionary forces which had resulted in its genetic makeup.

Increasingly the data from genetic studies is being used to inform conservation of FGR in particular tree species. For example, yellow cypress (Xanthocyparis nootkatensis) and western red cedar (Thuja plicata)

are mentioned in _anada’s report/ Other examples in the published literature include:

  • Red calliandra (Calliandra calothyrsus) in Mexico and Central America indicating need to conserve representative populations in four identified evolutionary significant populations Chamberlain 1998);

  • Pau-Brazil (Caesalpinia echinata) in Brazil indicating need to conserve different populations in different geographic areas (Cardoso et al. 1998); and

  • Marula (Sclerocarya birrea) in Kenya indicating need to conserve specific populations with high genetic diversity (Cardoso et al. 1998).

Sometimes genetic studies together with provenance trial/quantitative variation data, e.g. pino candelillo (Pinus maximinoi; Dvorak et al. 2002) or morphological quantitative data, e.g. he guo mu (Paramichelia baillonii) in China are used to inform conservation plans (Li et al. 2008). Various genetic studies are demonstrating the importance of glacial refugia for conserving tree species and their diversity, e.g. for broad-leaved trees such as oaks (Quercus spp.) in Europe (Iberian Peninsula, Appenine Peninsula and the Balkans) (Potyralska and Siwecki 2000); for bush mangoes (Irvingia spp.) in central and West Africa (central southern Cameroon, south-western Nigeria and central Gabon; Lowe et al. 2000) for Chinese firs (Cunninghamia) in east Asia (Huang et al. 2003). On the other hand, species growing in marginal environments or at the extremes (climate and soils) of the range may contain unique diversity and specific adapatations that warrants special attention for evaluation and conservation.

The increased information being generated through DNA studies is also being used to make generalised recommendations on how to conserve genetic diversity e.g. Hamrick (1994) suggested that five strategically placed populations should maintain 99% of their total genetic diversity when more than 80% of the total genetic diversity resides within populations. The review of Newton et al. (1999) noted that application of molecular techniques to diversity studies in a variety of tree species had highlighted a greater degree of population differentiation than indicated by previous isozyme analyses: in the absence of detailed information of the genetic structuring of a species, it may be prudent to conserve as many populations as feasible and resources allow. In many countries the organizations involved in undertaking DNA research on trees, such as Universities and Research Agencies, are often different and not well linked up with the agencies tasked with developing and implementing FGR conservation strategies such as Forestry and Environment departments, land managers and others. Accordingly improved FGRC&M planning and outcomes will require closer communications between both groups both in identifying priority species for study and subsequent planning, implementation and monitoring of conservation and management strategies based on research findings.

1   2   3   4   5   6   7   8   9   10   11

Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur © 2016
rəhbərliyinə müraciət

    Ana səhifə