Tree species composition of natural forest islands in a savanna matrix in the northern Brazilian Amazonia

Study Extent

The study was carried out in 12 forest fragments distributed in the Roraima’s savanna region, located in the municipality of Boa Vista (state of Roraima), northern Brazilian Amazonia, in a locality currently known as “Projeto de Assentamento Nova Amazônia I” (PANA I): 2.8864 N to 3.1526 N / -60.7638 W at -60.9865 W. The phytophysionomic formation of the region is typically savanna, ranging from grassy to parkland, with several forest fragments scattered in the general landscape. The temporal coverage of the study was 07/2013 to 03/2014.

Sampling

The natural forest fragments (forest islands) inventoried are Pleistocene relics that represent the richness and tree species composition of the past forest formations occurring in the forest-savanna contact zone of the northern Brazilian Amazonia. The forest inventory was articulated through the establishment of three transects crossing each island in the north-south direction. In each transect, sampling plots (10 m x 30 m) were dispersed between the border and the interior of the fragments: 8-10 plots for fragments with area > 30 ha, 4-8 for islands between 10-30 ha, and 2-6 for islands < 10 ha. This sampling design was the most adequate to represent the forest fragments, avoiding pseudo replication and maintaining a minimum distance (independence) between transects and plots. Forest inventory was performed based on measurements of stem DBH (cm) and individual total height (m); the last one by visual estimates. Vegetative and reproductive material were collected, as well as a general description of each species was done. Photographs of all collected morphotypes were done too.

Quality Control

All the individuals observed were measured. Most species were collected and registered by a numbered tag in the fieldwork. All of them were identified botanically to deposit in herbariums. Thirty-six vouchers representing most of the inventoried species were deposited in the UFRR Herbarium.

Method steps

1. The species identification was done by R. O. Perdiz using both (i) specific literature and (ii) comparison with herbarium specimens from INPA, K, MIRR, P, RB, SPF, UFRR, and US, including the digital resources of Projeto REFLORA (Plantas do Brasil: Resgate Histórico e Herbário Virtual para o Conhecimento e Conservação da Flora Brasileira - http://reflora.jbrj.gov.br/reflora/herbarioVirtual/). Herbaria acronyms follow Thiers (2019).
2. Scientific names of the species list were checked against database provided by BFG (2015) and Tropicos (http://www.tropicos.org/). The circumscriptions for the botanical families followed APG IV (2016).

The study was carried out on 12 natural forest fragments (forest islands) dispersed in a Roraima’s savanna area, located in the municipality of Boa Vista, state of Roraima, northern Brazilian Amazonia. This area is legally characterized as an INCRA agricultural colonization project - currently named as “Projeto de Assentamento Nova Amazônia I” (or PANA I). The PANA I cover an area > 43,000 ha in extension in the confluence zone between Rio Cauamé and Rio Murupu, both integrating the Rio Branco basin.