Abstract
To examine claims that reforesting degraded Imperata grassland in Leyte (Philippines) made streamflow perennial again, we studied the hydrological behaviour of a 23-year-old mixed-species “reforest” between June 2013 and May 2014. Typhoon Haiyan, one of the strongest events ever, caused major damage to the site in November 2013. Average daily apparent water use (ET) was 5.0 mm day −1 pretyphoon and 3.2 mm day −1 after disturbance. Corresponding ratios of period total quickflow Q q to precipitation were 16% and 44%. Quickflow volume and peak discharge increased rapidly once a threshold value of ~250 mm for soil water storage in the top 60 cm was exceeded. Before disturbance, quickflow consisted predominantly of lateral subsurface flow due to high soil hydraulic conductivities down to 60 cm. After disturbance, shallow groundwater rose regularly to within 10 cm of the surface on foot slopes, and saturation overland flow was observed during several large storms. Comparing estimated annual ET and Q q for undisturbed conditions for the reforest and a nearby degraded Imperata grassland microcatchment suggested that the extra infiltration following reforestation (~240 mm year −1 ) exceeded the extra ET by the reforest (100–185 mm year −1 ), implying a net positive trade-off (55–140 mm year −1 ) and tentatively confirming local claims of improved dry-season flow.
| Original language | English |
|---|---|
| Article number | e2055 |
| Pages (from-to) | 1-20 |
| Number of pages | 20 |
| Journal | Ecohydrology |
| Volume | 12 |
| Issue number | 2 |
| Early online date | 5 Nov 2018 |
| DOIs | |
| Publication status | Published - Mar 2019 |
Funding
We dedicate this paper to Divina and Uldarico Padecio, leaders of the Manobo tribe, through whose vision and perseverance a degraded Imperata grassland has been transformed to a lush and well‐ functioning forest. Financial support from the China Scholarship Council, Vrije Universiteit Amsterdam, and the Australian Centre for International Agricultural Research (ACIAR Grant ASEM/2010/050 to J. Herbohn) is gratefully acknowledged. Professor Alfredo Lagmay and Dr. Maricar Rabonza of the University of the Philippines kindly supplied the DTM files that enabled the preparation of the site map. We thank Dr. Nestor Gregorio (ACIAR project and University of the Sunshine Coast, USC) and Professor Arturo Pasa (VSU) for overall facilitation of the work and Professor John Herbohn (USC) for his continuous support. The manuscript benefited from the comments of an anonymous reviewer.
| Funders | Funder number |
|---|---|
| Australian Centre for International Agricultural Research | ASEM/2010/050 |
| University of the Philippines |
Keywords
- Imperata grassland rehabilitation
- infiltration trade-off
- reforestation
- streamflow
- typhoon impact
