The Ecuadorian coast has two main types of forests, which are differentiated by their phenology: dry forests are deciduous and more humid forests are evergreen. Less of the dry forests on the Ecuadorian coast is protected (13% of its area) than the evergreen forests (28%), and the area devoted to the protection of dry forests (1069 km2) is substantially less than the area devoted to the protection of evergreen forests (2800 km2). Yet the conservation status of dry forests is more critical, with 83% of their area classified as having very low connectivity, 70% as being highly fragile and 86% as being highly threatened. In addition, the dry forests have fewer protected areas than the evergreen forests. It is therefore necessary to increase the protection of deciduous ecosystems as part of a comprehensive national strategy because they support high levels of biodiversity and many endemic species.

This study aims to understand the distribution of species of Jacquemontia (Convolvulaceae) in Brazil and to determine the centre of endemism of the genus in that country. A database of around 2000 records of samples deposited in 46 herbaria was created. Twenty-one species were classified as widely distributed, of which 14 have continuous distributions and seven have disjunct ones. The remaining 26 species were classified as restricted and among these, 14 were considered endemic and 12 microendemic. The centre of endemism of the genus is in the Espinhaço Range, which traverses Bahia and Minas Gerais. The distribution patterns are discussed and a new assessment for the Red List of Jacquemontia is suggested.

The Pleistocene Arc Theory (PAT) suggests that present-day disjunct fragments of dry forests in central tropical South America give evidence of a previously more continuous distribution during the Pleistocene that has been disrupted by dry-cold vs. humid-warm climatic cycles. This Arc extends from NE Brazil to NE Argentina and eastern Paraguay, through the Chiquitanía to NW Argentina and SW Bolivia and into the dry inter-Andean valleys in Peru and Ecuador, with intrusions into the Great Chaco. Seasonally Dry Tropical Forests (SDTFs) are floristically and physiognomically dominated by woody legumes, mostly deciduous in the dry season. In the last two decades field collection and research on legume taxa has greatly increased, with a significant number of taxonomic revisions and molecular phylogenetic studies, together with some paleoclimatic modelling studies. The evidence accumulated in the last 23 years has confirmed the integrity of the Chaco and Caatingas phytogeographical provinces, with an impressive and increasing level of botanical endemism discovered. The PAT pattern has also been supported, specifically through the mapping of five selected woody Leguminosae species (Anadenanthera colubrina, Enterolobium contortisiliquum, Pterogyne nitens, Amburana cearensis and Piptadenia viridiflora). The pre-existing nuclei of South American SDTF (Caatingas, Misiones and Piedmont) are now increased to four with the postulation of the Chiquitanía Nucleus in south-eastern Bolivia and bordering Paraguay. Some new endemisms are compiled from recent literature and mapped for the Misiones and Chiquitanía nuclei. The need for more botanical collections and further taxonomic, phylogenetic and demographic studies of South American legumes is emphasised.

The distribution of the nutrients N, P and K in soil and vegetation and their mobility through litterfall and decomposition in mature and successional stands of a subtropical dry forest were studied in Guánica, Puerto Rico. Soils of the Guánica forest have high total amounts of N (9100 kg/ha), P (1820 kg/ha), and K (7460 kg/ha). However, high extractable Ca (>4000 mg/g) and pH (> 7–8) may explain why only 1.3 and 25% of the total P and K, respectively, were extractable. Total ecosystem storage of N, P and K was 10,300, 1900 and 7700 kg/ha, respectively, of which vegetation stored only 10, 2 and 3%, respectively. Litterfall returned 26, 18 and 180% per year of the N, P and K stored in the ground litter compartment. Trees retranslocated about 30 and 65% of the N and P required to satisfy aboveground net primary production and immobilized P in dead roots. Slow leaf decomposition (7.3 yr for 95% decomposition) released K faster than mass, P as fast as mass, and ash and N slower than mass. The use efficiency of P by litterfall was high compared with other tropical forests, while that of N and K was similar to other tropical and temperate forests. Cutting and regrowth of vegetation resulted in differences in the nutrient concentration in litterfall and nutrient use efficiency of successional vegetation.

The Pleistocenic Arc, which must have originated from the climatic shifts in South America during the late Pleistocene, ranges from the Caatingas of north-eastern Brazil through south-eastern Brazil to the Paraguay and Paraná rivers confluence, into south-western Bolivia and north-western Argentina, and extends sporadically into dry Andean valleys of Peru or coastal western Ecuador. It is regarded as a new phytogeographic unit for South America, here named the Tropical Seasonal Forests Region, as it is characterized by a considerable number of endemic plant taxa at both generic and species level. The paradigm of the arc is the distribution pattern of Anadenanthera colubrina (Fabaceae), which, when superimposed on those of other woody species of seasonal forests, permits a reasonably accurate mapping of the new region, which might also have biogeographic implications for endemic bird taxa. The plant communities of this newly recognized unit are unique in their nature and floristic composition, when compared with other floristic areas of the continent by means of classic phytosociological and numerical analyses (PCA). These ecosystems have remained submerged within other vegetation units in South American phytogeography (such as the Chaquenian or Amazonian regions), and have been particularly neglected in conservation policies. An urgent call is made for these areas to be preserved before they disappear, because they are located in areas with some of the best agricultural soils of tropical South America, and therefore subject to clearing for farming.