The global abundance of tree palms

Aim: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location: Tropical and subtropical moist forests. Time period: Current. Major taxa studied: Palms (Arecaceae). Methods: We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results: On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions: Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests

Assessing vegetation changes in the dry deciduous Ainurmarigudi Reserve Forest, South India

The dry deciduous forest of Ainurmarigudi belonging to Anogeissus latifolia - Tectona grandis - Terminalia alata type, was classified as a reserve forest under the Project Tiger in 1973. Twenty years later, although felling has not been resumed, fires still occur regularly and the density of herbivores has increased considerably. This article attempts to determine the impact of 15 years (1978-1993) of total protection on the evolution of the stand from studies on the floristic and spatial structures, mortality, recruitment and regeneration. The stand is still open and deficient in young individuals (except for the population of Grewia tiliifolia). All the species do not evolve in the same manner. Tectona grandis and Dalbergia latifolia have serious problems of regeneration. In contrast, Grewia tiliifolia, whose recruitment is impressive, does not seem to be capable of establishing itself in the adult stage. From the point of view of regeneration, the only species which appears to maintain itself in the forest is Anogeissus latifolia. Establishment of the reserve has thus led to the opening up of the stand as well as a fall in its biomass, and also a slight decline in its tree diversity. The increase in the populations of big herbivores probably plays a major role in this evolution.Impact de la mise en réserve sur la forêt décidue sèche d'Ainurmarigudi, dans la réserve du «Project Tiger», Inde. La forêt décidue sèche d'Ainurmarigudi, à Anogeissus - Tectona - Terminalia, a été classée en réserve en 1973, dans le cadre du Project Tiger. Vingt ans après, si l'exploitation n'a pas repris, le feu passe régulièrement et les populations de grands herbivores ont considérablement augmenté. Cet article tente de déterminer l'impact de cette mise en réserve totale dans l'évolution du peuplement. L'étude des changements intervenus pendant 15 ans (1978-1993) dans les structures floristiques et spatiales, la mortalité, le recrutement et la régénération permet de dégager les tendances évolutives. Le peuplement est en phase d'ouverture et présente un déficit en jeunes individus (excepté pour la population de Grewia tiliifolia). Toutes les essences n'évoluent pas dans le même sens. Tectona grandis et Dalbergia latifolia montrent de graves problèmes de renouvellement et déclinent. Grewia tiliifolia, dont le recrutement est en revanche impressionnant, ne semble pas capable de s'installer à l'état adulte. La seule espèce qui paraît se maintenir dans le peuplement est Anogeissus latifolia. La mise en réserve, en plus d'une ouverture et d'une diminution de biomasse, est donc à l'origine d'une perte de diversité au niveau arborescent, l'augmentation des populations de grands herbivores jouant vraisemblablement un rôle majeur dans cette évolution