Plant species diversity changes in abandoned chestnut (Castanea sativa) groves in southern France

Over the last few decades, marked land use changes have taken place in many Mediterranean ecosystems. For example, many chestnut groves in France are now abandoned and have turned into 'natural' coppice stands while others ar e now dear-cut every 10 or 15 years for wood. Species composition and life form diversity of the plant communities have changed markedly both in the a bandoned groves and in the periodically clear-cut coppice stands. What are the consequences of these changes on biodiversity at local and regional sca les, and what are the implications for 'new Forestry' management intended t o conserve biodiversity at the same time as it optimizes productivity and p rofitability? To answer these questions we studied plant species diversity in the understorey strata along a successional gradient including cultivate d grove; abandoned grove: young (15 years old), medium (40 years), and old (>55 years) coppice stands. The results showed that species richness decrea sed quickly but not steadily along this gradient. but life-form spectra dat a highlighted that the high levels of plant species biodiversity in cultiva ted groves were due primarily to the large number of therophytes (annual pl ants). Ar a shorter time scale, we also studied the consequences of experim ental clear-cutting on plans species biodiversity. Direct measurements over four years showed that species richness and diversity in the understorey i ncreased in the first two years after clear-cutting, but decreased during t he 3rd and 4th years. This decrease corresponded closely with a steady incr ease in Leaf Area Index of the forest canopy. These results have been used to suggest some possible ways to manage the biodiversity in these ecosystem s.