Dominique Hervé

Carbon and Nitrogen Dynamics of Potato Residues and Sheep Dung in a Two-Year Rotation Cultivation in the Bolivian Altiplano

Abstract In the high Andes, the traditional rotation is two or three years cropping with potatoes and cereals after 5 to 10 years of fallow. In the Bolivian Altiplano, the balance of available soil nitrogen (N) was monitored during 2 years of cultivation after 3 years of fallow. Two varieties of potato were planted in the first year as the head of the rotation. Potatoes or barley were planted in the second year. Fertilization with sheep dung was only applied for potato cropping. The dynamics of decomposition and N‐release of the amendment and the plant residues were measured using litterbag incubation in the field. Using the N‐release rates provided by the litterbag experiment, we modeled the fate of the mineralizable N originating from the sheep dung and the potato residues decomposition of a 2‐year succession to assess if the N supply from fertilization covered the plant demand.

An environmental governance support tool: community-based forest management contracts (Madagascar)

This article reports on the implementation of community-based forest management contracts in Madagascar as part of a national environmental action plan designed to strike a balance between rural development and conservation of natural resources. The article highlights how these systems offer an outstanding opportunity to observe the negotiation processes and shifts in relationships between the actors involved, and thus to learn more on the conditions governing sustainable management of conservation and development. A single, specific management system like community-based management cannot be expected to resolve every single issue, but analysing the interplays between different management systems provides insight into the specific features of target cases. They would appear to be promising decision support tools for environmental governance issues as they promote social and territorial reforms and generate new flexibilities for all the stakeholders involved.

Spatio-Temporal Evolution of the Fragmentation Classes of the Mikea Dry Deciduous Forest (Southwestern Madagascar)

In southwestern Madagascar, the Mikea forest is a highly diverse ecosystem of great biodiversity, which mixes dry deciduous forest in the eastern part and xerophytic thicket in the western coastal area. However, dry forests and shrubs are rapidly destroyed due to slash-and-burn cultivation (hatsaky) and exploitation of forest resources by riparian communities and external operators. The aim of this paper is to evaluate forest fragmentation in the Mikea national park, by comparing past and recent forest maps. The analysis of forest fragmentation is based on landscape indices. The changes in forest cover have been detected from time-series SPOT satellite images registered over 15 years (1999, 2005, and 2014). Between 1999 and 2014, forest area is reduced by 39.8% which is equivalent to an annual forest loss rate of 4.6%. The forest fragmentation is associated with a significant decrease in forest patch size. The mean patch size decreases from 37,228 to 18,731 ha from 1999 to 2014. The primary direct causes are economic driven due to intense anthropogenic activities such as wood charcoal production, logging, accompanied by frequent wild land fires. The indirect cause is the absence of a sustainable environmental management and conservation strategy.