The growing trend of clonal forestry worldwide is due largely to higher demand for quality wood fibre. Clonal eucalyptus forestry, for instance, has already been developed in a number of countries including Brazil, Venezuela, South Africa and Colombia.
    The benefits of clonal forestry are plenty, chief of which is improvement in wood quality particularly when integrated with specific end uses. Given a six- to seven-year rotation, these wood quality improvements are the main objectives of clonal eucalyptus
    The implication is that mill and financial mangers can have the type of wood desired for the process environment and the eventual paper buyer. Mill and forest staff will have to work together to achieve this.
    Clonal forestry refers to vegetatively reproduced material gown in plantations. This material is normally obtained from rooted cuttings, but it can also be from tissue culture, somatic embryogenesis or other methods.
    Organizations need to look into several key issues before they take the plunge into clonal forestry.

Cost Effectiveness

    As with any forest management technique, a number of steps must be implemented successfully for a cost-effective clonal programme. For a start, a wide range of species, provenance and progeny trials are required as part of a tree improvement strategy to maintain a wide genetic base. From this base only a small number of clones will emerge into the operational planting programme, having been identified in trials on multiple sites.
    Besides trials, nursery technology, including clonal garden management, is critical. Unlike seedling management, coordination of clone demand by site and year requires careful planning in order to maximize growth. This is due to higher initial cost of clonal plantations compared to seedling plantations.
    Changing the extensive clonal garden management system to one of micro-cuttings is being done to reduce the cost of each cutting. Field trials of clones on multiple sites are being undertaken to identify disease resistance and the capacity of different clones to respond to available resources such as water and nutrients.
    And lastly, improvement in wood properties has to be looked into. This includes selecting clones for higher wood density as well as for better pulp and paper making ability. For instance, the genetic modification of lignin in certain existing clones is being evaluated. Such a modification may reduce digester charge or time, thus lowering the cost of pulp.
    


  
   
   

 

 


Managing Clonal Forestry

 By Dr. Jeffery Wright

Clonal Forestry Management

Careful management of several distinct aspects can ensure successful clonal forestry. While each of these can be managed separately, organisations with successful clonal strategies must coordinate all of them including.
o Nursery management
o Silviculture
o Tree improvement
o Growth and yield
o Disease and insect monitoring and control
o Wood quality

Nursery Management

Venezuela is one country with a long and successful history of forestry nursery management. Although initial efforts were by government organisations, the private industry is now more effective in nursery management, being supported by research from domestic and international institutions.
    Production includes seedlings and clones of important industrial species such as Eucalyptus urophylla, Eucalyptus urograndis, Eucalyptus camaldulensis, Gmelina arborea and Pinus caribaea var. hondurensis, as well as trials of other introduced species, including Acacias. Native species produced include mahogany, saqui saqui (Bombacopsis quinata) apamate (Tabebuia rosea) and others. 
    A growing trend in Venezuela is to develop clonal forestry for pine and eucalyptus. Given climatic and plantation establishment constraints, however, the clonal eucalyptus programme has to innovate in order to be successful. Organisations cannot merely duplicate techniques from other nurseries, as this will normally result in failure.

Silviculture

Selection of sites for eucalyptus clones is an ongoing task in silviculture, which looks at the relationship of a forest to its enviroment including the development, care and reproduction of forest stands. There are certain soils with characteristics that always produce high clonal yields. On marginal soils, and these are frequent, a number of factors are considered to determine whether clones should be planted. Clonal genetic potential cannot overcome poor soil or site preparation conditions.

    The extent of site preparation depends on the soil conditions, nutrient availability and physical structure and properties. Typical site preparation consists of subsoiling to a depth of 40cm, disking in two directions, followed by bedding in sites with poor drainage. In subsequent rotations, the only soil preparation is subsoiling to reduce any compaction resulting from logging practices.
    Control of weeds is critical in the first 18-24 months following planting. A pre-emergent is applied along top of the bed prior to planting. Two or more chemical control sprayings are required in the first year. In the second year only one chemical weeding is required in most stands.
    Fertilisation treatments have recently increased in order to achieve higher plantation yields. Research to date indicates that some sites are more responsive then others and that genotypes utilise resources differently. The research emphasis now is to identify soil parameters associated with fertiliser response and the financial return from fertilisation.

Tree Improvement

A viable and continuous investment in free improvement must be made to ensure that clonal gains are not a one-time occurrence. Some of the organisations that are best known for cloning have no long-term tree improvement programme in place.
    In Venezuela, Smurfit Carton e Venezuela (SCV) has had a eucalyptus tree improvement programme since the mid-80s. This programme is becoming more sophisticated as new techniques become available.

    The SCV tree improvement programme includes the introduction of new species and seed sources for testing Seed orchards, control crossing, progeny testing and evaluation are part of the improvement strategy for the seedling population. This programme is the basis from which new clones will e selected. All clones are tested in statistically designed trials prior to their deployment.

Growth and Yield

Clones of eucalyptus can have 10-15% less taper than trees growing n seedling stands. Thus, new volume equations are required. In addition, selected clones have better survival rates and less variation in height and diameter. This makes the development of new growth and yield equations an essential component of the clonal programme in order to increase the accuracy of total wood projections.








Information Resource: Asian Timber

Disease and Insect Moitoring and Control

The most common problem in the case of insects is leaf-cutting ants. The ants are controlled by chemical and mechanical methods. Other insect attacks come from defoliators. The most effective controls are biological especially those related to parasites or predators that reduce the population of the target insects.
    In the early stages of new planting programmes for exotic species, the trees are isolated from those insects and diseases that affect them in their area of origin. Native pathogens require time to adapt before they can infect exotic species, thereby giving a window of opportunity to produce large quantities of wood. However, this opportunity is short-lived and generates the need to develop innovative mechanisms to manage insects and diseases. Diseases in the forest plantation cannot be controlled by fungicide applications, though this is a regular practice in the nursery.
    Disease control includes planting species or clones that are highly resistant and maintaining a healthy tree status using appropriate silvicultural methods.
    The constant monitoring of insects and diseases in commercial stands and trials is very important to predict the arrival of new pests and evaluate their impact on survival and final yield. Information shared among numerous organisations worldwide is helping to reduce the risk of growth loss due to disease and insects.

Wood and Pulping Quality

In the case of SCV, the main product of the eucalyptus clonal programme is pulp for the manufacture of paper. Clones are tested for wood density so that higher density clones can be selected. Individual clones have also been tested for pulp yield, kappa number and paper strength traits. One area of mutual interest is to modify lignin in tested clones of eucalyptus to reduce the cost of pulping.

Outlook for Global Clonal Forestry

Future clonal programmes are expected to have an increasing element of biotechnology while retaining traditional methods. Besides, marker-aided selection will likely become more important, as will tissue culture for the rapid bulking up of the best clones.
    Movement of eucalyptus clones worldwide will probably increase because DNA fingerprinting and other techniques allow royalty payments to be controlled. Improved stand management, including re-fertilisation, will help increase yields on those sites where a response can be predicted. In addition, mill requirements will be integrated with clonal selection to leverage the integration the enterprise.