Critical Zone Hydrology Group

Hydrological impacts on the reforestation process across a degradation gradient in Leyte Island, the Philippines

Supervisors and collaborators:

• L.A. Bruijnzeel - VU University
• H.J. van Meerveld - VU University
• J. Herbohn - University of Queensland, Brisbane

Duration: Sept. 2011-2015
Funding: China Scholarship Council (CSC) and Australian Centre for International Agriculture Research (ACIAR)

Research questions

Since the 1960s most primary forests on Leyte have been cleared and replaced by shifting cultivation, bush land or pastures and coconut plantations (NAMRIA, 2003). This led to increased soil erosion and loss of biodiversity. In the 1980s a logging ban was put into force and since efforts have been undertaken to reverse these trends through reforestation. However, it is still under debate whether the reforestation process has really brought benefits to the residents and the local environment. What kind of plantation best controls soil erosion? What is the influence of the soil physical characteristics? Is there a reduction in the frequency and/or magnitude of storm flows during the rainy season after plantation establishment, and does the streamflow increase during the dry season? Prior to plantation establishment, what was the rainfall-runoff response of the grasslands? The overall objective is to help the forestry department of the Philippine government make decisions during the plantation establishment, and to evaluate the 'net' hydrological effects of the reforestation. The following research topics are addressed in my research:

• The effects of different plantation species on the soil restoration process.
• Comparison of the rainfall-runoff response between two grasslands with different levels of soil degradation.
• Comparison of stormflow response between two forested catchments. One is plantation only and the other has a mix of plantation and old-growth rainforest.