M-TROPICS observatory

M-TROPICS observatory

Scientific context

Tropical ecosystems are subject to a growing demography associated with rapid changes in land use, leading to the degradation of water and soil resources in these regions. Multiscale TROPical Catchments (M-TROPICS) observatory aims to quantify  the matter balance exported by basins in a context of contrasted and complementary vegetation cover and land use in Cameroon, India and Southeast India. In Cameroon, the conversion of rainforest ecosystems to slash-and-burn agriculture is studied thanks to five nested watersheds, from the experimental Mengong basin (Nsimi, 0,6 km²) to Nyong River basin (Olama, 18 500 km²). In South India, the impact of groundwater-irrigated agriculture, in  a subhumid context, is discussed by comparing an agricultural experimental basin (Berambadi, 80 km2) with a preserved forest experimental basin (Mule Hole, 4.1 km2), both located in the Kabini river basin. In Southeast Asia, the erosion generated by land use changes in a mountainous area is studied in three experimental basins in a humid context: Houay Pano (0,60 km²) North Laos, which is the most instrumented site, Huay Ma Nai (0,93 km²) North Thailand, and Dong Cao (0,47 km²) North Vietnam.


Starting year: 1993 Cameroon, 2000 Southeast Asia, 2003 India

Localisations: Cameroon, Inde, Laos, Vietnam, Thailand

Keywords: tropical climate, tropical agrosystems and forest ecosystems, monsoon, hydrochemistry, erosion, weathering

Database: https://mtropics.obs-mip.fr/catalogue-m-tropics/

Web site: https://mtropics.obs-mip.fr/

Cameroon : Stéphane AUDRY and Jules NDAM ;
India : Jean RIOTTE, Laurent RUIZ and Sekhar MUDDU ;
Southeast Asia: Laurie BOITHIAS, Olivier RIBOLZI, Alain PIERRET, Arthon BOONSANER, Tien MINH TRAN, Nivong SIPASEUTH

Landscape of the Berambadi basin, India © Jean Riotte

Scientific questions

The scientific question that led to the creation of the M-TROPICS observatory is the response of tropical watersheds to global change (land use, climate). More specifically, M-TORPICS aims to:

  • Determine the flux of water, organic and inorganic matter present in solution (major anions and cations, carbon) and in suspension (particular organic carbon);
  • Establish physical erosion and chemical alteration balances.

In all sites, hydrological, biogeochemical (Cameroon and India especially) and erosive (Southeast Asia) issues are developed.

Sites and measured variables

Meteorological variables (daily rainfall, temperature, wind speed and direction, relative humidity, solar radiation, atmospheric pressure) are measured for all the experimental basins by automatic weather stations. In Cameroon, six measuring stations (source and outlet of the Mengong near Nsimi village, Messam bridge on the Awout stream, So’o bridge on the So’o river, Mbalmayo and Olama on the Nyong river) are concerned with measurements of river flows and water chemistry. At Nsimi, soil pits and piezometers network are installed to monitor groundwater levels.

In India, both Mule Hole and Berambadi sites are instrumented to carry out hydrogeochemical monitorings of river and groundwater.

In Southeast Asia, each basin encompasses the monitoring of seveeral sub-basins at scales ranging from microplots (1 m²) to small watersheds (~1 km²). Data from land use, agricultural practices, flows, suspended matter and bed-load are collected. Each site has a weir for monitoring flows and bed-load, and an automatic sampler for monitoring suspended matter.

Partners and further information

M-TROPICS is managed by the Géosciences Environnement Toulouse and iEES Paris laboratories, with a collaboration between researchers from IRDCNRS, Université Paul Sabatier, and partner institutions in the South. In India, it is the Indian Institute of Sciences; Bangalore. In Cameroon, it is IRGM-CRH, Yaoundé I and Dschang Universities. In Southeast Asia, partners are the Ministère de l’Agriculture et des Forêts of Laos, the Department of National Park, Wildlife and Plant Conservation in Thaïlande, and the Soils and Fertilizers Research Institute in Vietnam.