Project lists

Reconstruction and sustainable management of degraded forest based on the combination of inter-planting nitrogen fixation rare tree species and thinning
25 Feb 2020     

Project title:   Reconstruction and sustainable management of degraded forest based on the combination of inter-planting nitrogen fixation rare tree species and thinning  [project ID:  2018P4-CAF ]

Executing agency:     Experimental Center of Tropical Forestry, Chinese Academy of Forestry 

Implementing agency:   Institute of Forest and Wildlife Research and Development

Budget in USD (total / APFNet grant): 503, 000/378, 000

Kick-off date & duration: 04/2018-03/2021

Target economy: Cambodia

Site Location:  Bos Thom village, Khna Por commune, Soth Nikum, Siem Reap province, Cambodia.


To demonstrate effective approaches on degraded forest transformation to improve the growth and quality of the forest stand and enhance ecological services by enhancing forest restoration and sustainable forest management;

To improve the livelihood of the local forest dependent poor people;

To share information and knowledge of best practices on forest restoration and rehabilitation.

Expected outputs:

Explore and demonstrate effective approaches on degraded community forest, optimize the forest structure, and improve forest ecosystem services;

Non-forestry livelihood activities are developed to improve the local’s livelihood;

Share information and knowledge of best practices on degraded forest restoration and rehabilitation in Cambodia.




Restoration of degraded forests in Cambodia remains challenging due to financial issues and a lack of experience in using different restoration technologies. Most degraded forest areas in Cambodia, often community forests, are covered with unfertile soil, that means they are  low in soil nutrients, sandy, low in soil organic carbon, and have a poor water holding capacity.  True restoration of a forest ecosystem is a complicated process, so the selection of suitable methods which are appropriate for the local site conditions, increase economic value while restoring ecosystem services should be considered.

Sharing a similar fate with other community forests, the Bos Thom community forest is located 30km from Siem Reap city and has 445 ha of degraded forests. The forests have been over exploited due to a lack of management and supervision, allowing illegal cutting of valuable tree species and firewood collection. This resulted in large forest canopy gaps, reduced biodiversity and soil erosion. In short, this site is in dire need of effective forest restoration that not only restores the trees, but also the soil.

The APFNet funded project on “Reconstruction and sustainable management of degraded forest based on the combination of inter-planting nitrogen fixation rare tree species and thinning “demonstrates new approaches on integrated forest restoration by restoring the soil through the use of nitrogen-fixing tree species while also improving local livelihoods. Building upon the completed project “Multi-Function Forest Restoration and Management of Degraded Forest Areas in Cambodia”, also funded by APFNet, this project will complement prior and showcase new forest restoration approaches in different forest ecosystem conditions to help practitioners in Cambodia find a restoration solution that works for them.


 Restoring forests by restoring their soil

APFNet has tested several different restoration models across Cambodia, especially enrichment planting, agroforestry, assisted natural regeneration, and general silviculture techniques in Siem Reap, Kampong Thom, and Kampong Speu province.

Differing from those, degraded forests of Bos Thom CF in Siem Reap province will adopt a new method with technical support and experiences from the Experimental Center of Tropical Forestry under the Chinese Academy of Forestry. The method will focus on close-to-nature forest management through group inter-planting in forest gaps with rare tree species that have a nitrogen fixation ability such as rose wood species Dalbergia cochinchinensis, and Senna siamea.  This approach of using nitrogen fixing trees is one of the most promising and low cost measures for restoring degraded forests both above- and below ground. This method involves removing poorly growing or damaged tree to make space, and inter-planting the stand with nitrogen fixing species.

Gradually, in the community forests, the approach will promote a resilient uneven-aged mixed forest, enhance productivity, stand quality, stand stability and ecological function of the forests, accelarate forest succession and provide timber resources through the thinning the non-target tree species.


Reducing dependence on forests by improving local livelihoods

Successful forest restoration is not just defined by whether the forest itself is restored, but by whether additional economic benefits for local people who are dependent on forest resources are provided.


Fig. 1 A local folk house

This project will provide benefits and income generation for the local community by establishing home gardens and providing alternate sources of energy in order to reduce the pressures on forests.  Normally, local households in rural villages live in a wooden house on a small piece of land (less than 1ha and sometimes bigger for higher income families) on which several tree species, crops and vegetables are growing. However, this setup can usually only cover the basic needs of single household. Transforming these small patches into homegardens can enable families to earn an income instead of only barely subsisting on their land. The general concept of home gardens is to combine various trees in multiple stories with crops and sometimes domestic animals around the homestead. This project will interplant fruit trees that can provide short term income such as banana, papaya, coconut or cashew nut and combine it with the existing plants around local households. This will give local people both an opportunity to improve the food diversity for their own daily consumption and enable them to sell to the local market. Additionally, in order to avoid cutting trees from natural forests the project will encourage local people to plant trees for firewood around their house. Furthermore, the installation of small scale solar equipment will provide adequate electricity to reduce overall expenses in the family. Finally, we expect that the combination of alternative sources of income, the availability of alternate firewood resources and the general decrease in living costs will reduce the pressure the surrounding forests are currently experiencing.


What are nitrogen-fixing tree species? 

Nitrogen is one of the key nutrients in soil and essential for plant growth. Generally, the way soil obtains nitrogen is through the surmise and subsequent break-down of organisms on the forest floor (that is: falling leaves, or other dead plant or animal tissue), but importantly forests cannot just use atmospheric nitrogen. Despite this forests are generally fairly good at keeping the nitrogen levels stable through internal recycling. The one threat to this cycle is soil erosion, which effectively washes the nitrogen off the site, leaving the earth stripped of nutrients.

Nitrogen-fixing tree species form a unique symbiosis with certain types of bacteria and archaea called rhizobia within the nodules of their root systems. These organisms are able to transform atmospheric nitrogen into molecules such as ammonia that can then be used by trees. Eventually these trees die and their dead plant material will be added into the overall nitrogen cycle of the site, effectively adding former atmospheric nitrogen into the soil.

Project materials:


Cambodia projects brochure