Species Selection

Selecting suitable species to plant is a crucial step when restoring degradation stages 3 to 5 (see Forest Degradation), particularly when deciding which species satisfy the criteria of "framework species" and/or nurse crop species. We suggest two simple semi-quantitative methods to facilitate the process of species selection: the ‘minimum standards’ approach and a ‘suitability index’, is based on a ranked relative scoring system. They may be used independently or in tandem, such as using minimum standards to create a short-list of species that is subsequently ranked by relative suitability index. These two methods make best use of the data available, while retaining the flexibility required to meet the various objectives of different projects.

Applying minimum acceptable standards of field performance

The most important field-performance criterion is survival rate after planting out. No matter how well a species performs in other respects, there is not much point in continuing to plant it if its survival rate after 2 years falls below 50%. Additional minimum acceptable standards can be applied to growth rates, canopy width, suppression of weed cover, but all are subordinate to survival.

Extract field data collected after 18–24 months (at the end of the second rainy season in seasonal forests) 

Example: Three minimum standards are applied to field-performance data collected at the end of the second rainy season after planting

• survival >50%;
• height >1 m (as seedlings should be planted when 30–50 cm tall, this represents a more than doubled height);
• crown width >90 cm (i.e. the crown has obtained more than half the width required to close canopy at a tree spacing of 1.8 m (equivalent to 3,100 trees per hectare)).

In the table below, data that fail to meet minimum standards are indicated in red.

What if too few species exceed minimum acceptable standards?

• improve overall planting stock quality — review the nursery data to see whether there is anything that can be done to increase the size, health and vigour of the planting stock;
• experiment with intensified silvicultural treatments (e.g. carry out weeding or apply fertiliser more frequently), particularly if you think that site conditions could be limiting;
• try different species — review all sources of tree species information and start collecting seeds of species that have not already been tested.

When selecting trees in nurseries, species identification is crucial. However, the leaves of seedlings and saplings in nurseries are often different to those of adults and described in regular plant-identification manuals. So here we present a seedling identification guide. Just click on the image below to open the database in a new window. Either type in either the characteristics of the plant, to determine its name,  or type in the name of a species to determine if the plant you have matches the description and pictures. The tool is also useful when performing rapid site assessments and trying to determine the initial density of saplings in order to calculate the number and species of trees to plant.  The database was compiled by Dr. Greuk Pakad under the project "Tree fruits, seeds and seedlings for forest restoration in northern Thailand: Phase 2" funded by the National Science and Technology Development Agency, 2016-18.

CLICK HERE - for database of tree seedling morphology