Andringitra Mountains, Madagascar

Understanding a landscape created by fire and herbivores: Ecological Analysis and Management Plan of a unique Subalpine Forest/Grassland Ecotone

In Cooperation with Bernardin Rasolonandrasana, Urs Bloesch, Frank Klötzli, Peter Schachenmann, Hanta Rabetaliana, and Michel Randriambololona

In the subalpine forest/grassland ecotone at ~2000m asl., traditional land use through grazing and fire, has over the last 100 years produced an anthropogenic mountain landscape with a complex mosaic of forest patches, ericoid bush and open grasslands, maintaining unique biodiversity, important pasture values and aesthetic beauty. Since work began for the creation of a National Park in 1993, management objectives focused on protection, preservation and scientific research, initially excluding traditional landuse. However, control of grazing herbivores and fire provoked rapid ericoid bush encroachment, pioneered by fire sensitive Philippia cryptoclada. This lead to the challenging question how Protected Area management objectives can be linked with local communities' traditions and needs to safeguard in collaborative approaches unique biodiversity, use- and scenic values.

Results from floral and faunal inventories declare Andringitra mountains a biodiversity hot spot in Madagascar. The subalpine forest/grassland ecotone is outstanding for Ericaceae, Asteraceae, Poaceae, geophytic Orchidaceae and Succulents. 14 punoid to paramoid vegetation units were identified. Amongst Poaceae, the dominant genus is the palatable Panicum, represented by 13 species with P. andringitrensis, endemic for Andringitra. Convergence phenomena between the genera Panicum, Philippia, Helichrysum and Stoebe highlight similar adaptation strategies to special climatic conditions.

To reopen ericoid bush and arrest further encroachment, strategic use of clipping close to the ground and controlled burning are studied as future management tools. Philippia cryptoclada, trichoclada and floribunda react to clipping by extensive resprouting from the base, increasing dramatically the number of stems. Burning kills all Philippia spp. except Ph. trichoclada, which resprouts from the base as seen in the clipping experiment.
To assess ecological trends of systemic ecosystem dynamics and resilience, we developed a simple monitoring methodology, using Composite Entomological Traps for sampling epigeal terrestrial invertebrates. Relative insect abundance is grouped into 4 main trophic guilds of phytophages, detritophages, zoophages and parasitoid and then compared in relation to the anthropogenic history of 7 sites along a forest-grassland gradient from east to west. For mountain forests disturbed by fire and cattle, supplementary research in progress studies the re-colonisation patterns by non-flying Micro-mammals (Insectivores and Rodents) as indicators for habit damage, rate of recovery and speed of return to functional habitats.

Our investigations have shown, that unique mountain forest/grassland biodiversity, pasture-, and aesthetic values have evolved with and are maintained through moderate anthropogenic disturbance. A holistic, proactive systems approach to park management has thus to consider the shaping role of human culture as an intrinsic part of biodiversity and ecosystem functionality.