Effects of Invasive Animal Species and Wildfire on the Water Budget in a Tropical Forest and Savannah Mixed Watershed in New Caledonia (SW Pacific)
Abstract
Rusa deers were introduced in Grande Terre (the main island of New Caledonia) in the middle of the XIXth century as a source of healthy meat for hunters, as there was originally no big mammals in New Caledonia. They proliferated and present now a severe threat to forest regeneration in Grande Terre. Feral pigs cause damage to soils and roots but are also considered as valuable game for hunting.
Both species impact the water budget and water quality in mountainous catchments that provide most of the water resource of Grande Terre. Their impact on the water budget must be quantified to inform policymakers to improve management of these invasive species. Wildfire are a major concern in New Caledonia. Resilience and recovery of forests and savannas have yet not been assessed in the tropical and humid climate of the East Coast. Three experimental plots were set up in contrasted areas in the 64 km2 Thiem watershed (Touho, North East coast of Grande Terre) with an area of nearly 100 m2 and a slope of 32% which is the mean slope of the watershed. They are limited by steel plates rammed to a 15 cm depth. Runoff is deduced from the water level measured at a 24 cm HS Flume and one or two series of humidity probes were set up at depths of 20 cm and 60 cm in each plot. Raingauges were set up at less than 100 m of each plot. Two plots are located in the tropical forest and in the sub watershed of the Haccinem reservoir used for drinking water. The SCAR plot is strongly impacted by deers which are trapped at least twice a week by automatic cameras. Soil is almost devoid of leaf cover; seedlings as well as shrubby layer are almost absent. On the contrary the REGEN plot present strong regeneration with high seedling density. The SAV plot is located in a niaouli (Melaleuca quinquenervia protected from fire by its thick bark) savannah. It was burned 3yrs ago by wild fire and artificial fire is planned to be set in Oct. 2019. Records spanning one year show that runoff is pronounced at SCAR and minimum at REGEN, were humidity sensors present extensive infiltration of rainwater. SAV present intermediate results. Relating these results to invasive species still needs to address the following questions : 1) large heterogeneities of land surface in the watershed, 2) influence of subsurface flow in SCAR.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H13K1841G
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCES;
- 1632 Land cover change;
- GLOBAL CHANGE;
- 1803 Anthropogenic effects;
- HYDROLOGY;
- 1836 Hydrological cycles and budgets;
- HYDROLOGY