Impact of indigenous land uses on tree structure, diversity, and species composition in Bosawás Biosphere Reserve, Nicaragua

Abstract

Griffith, D.M., Coronado, I., Asa, C., Polisar, J., Carmona, I. (2012). Impact of indigenous land uses on tree structure, diversity, and species composition in Bosawás Biosphere Reserve, Nicaragua. Ecosistemas 20(1-2):101-117

Indigenous societies inhabiting tropical forests have been recognized for their role in conserving biodiversity and natural resources through traditional patterns of subsistence. However, few studies have quantified the relative impact of these land use patterns on the structure and diversity of forest species. This study compared the size, density, diversity, and species composition of trees between three principal land use zones (agriculture, hunting, and conservation) in an indigenous territory of Bosawas Biosphere Reserve. Trees with a minimum diameter at breast height (DBH) of 10 cm were identified and measured in 13 1-km transects located among the three zones. The first hypothesis was that tree size, density, and diversity are less in the forest mosaic of the agricultural zone than in the forests of the hunting and conservation zones. This hypothesis was accepted in the case of total DBH per transect, while mean height, mean DBH, individual tree density, stem density (some trees had multiple stems),  and  estimated diversity were not significantly different among the three zones. The second hypothesis that tree species composition in the agricultural zone is distinct from that of the other two zones was accepted. However, composition was also different between the hunting and conservation zones and was not significantly related to distance from the nearest indigenous community. Although all indigenous farming and nearly all forest product extraction occurs in the agricultural zone, the mosaic of secondary and mature forests that constitute the majority of land use cover in this zone exhibited tree structure and diversity similar to that of the conservation zone, where human impact is minuscule. In contrast, indigenous land uses influenced species composition. This last result emphasizes the importance of maintaining remnants of mature forest in the agricultural zone to serve as species refuges and of strengthening traditional norms that insure forest protection in the hunting and conservation zones.