Search

Questions : Which role did historical anthropogenic disturbances play in modifying the natural fire regime? To what extent have they shaped current forest? Do those disturbances have lingering impacts in the present‐day landscape? Are certain tree species related to former land use? Location : eastern Quebec, Canada. Methods : Spatial data on landscape structure, burnt areas, settlements, and forest patches were vectorized on an archival map dating back to 1938. For each landscape class, the total area, the number of polygons, and the proportion of the total landscape occupied by the largest polygon were analyzed according to elevation and to the Euclidean distance from the "settlement" polygons. An index of the spatial link between the landscape classes was calculated, based on the proportions of the perimeter of the polygons of each class shared with each of the other classes. A Kolmogorov–Smirnov test for pooled data was used to obtain the frequency distributions of landscape classes as a function of distance. The association between settlement fires and present‐day vegetation, and more specifically Populus and Betula stands, was tested by superimposing the most recent ecoforest map on the 1938 land‐use map. Distance bands on either side of the 1938 settlement front were delineated to calculate the proportion of each distance class occupied by present‐day aspen and birch stands. Results : Anthropogenic fires generated a recognizable landscape pattern of land use. Burnt areas were mostly located within 2 km from a settlement. Most burnings observed on the 1938 map were human‐induced, based on their spatial connection with the settled areas. Lingering impacts of these 20th‐century fires on present‐day forests were identified using the peculiar spatial distribution of tree species. The presence and spatial distribution of aspen in the present‐day landscape is tightly associated with previously burnt areas. Conclusions : Past land‐use strongly altered the natural fires regime and associated tree species. Current land‐use could potentially lead to increased degraded forest landscapes in the near future. -- Keywords : anthropogenic fires, aspen, boreal forest, land use, North America, Populus, settlement, spatial landscape structure, temperate forest.

Palaeoecological and archaeological studies have demonstrated that human populations have long inhabited the moist forests of central Africa. However, spatial and temporal patterns of human activities have hardly been investigated with satisfactory accuracy. In this study, we propose to characterize past human activities at local scale by using a systematic quantitative and qualitative methodology based on soil charcoal and charred botanical remains. A total of 88 equidistant test-pits were excavated along six transects in two contrasting forest types in southern Cameroon. Charred botanical remains were collected by water-sieving and sorted by type (wood charcoals, oil palm endocarps and unidentified seeds). A total of 50 Accelerator Mass Spectrometry 14C dates were also obtained. Results showed that charred macroremains were found at multiple places in the forest, suggesting scattered human activities, which were distributed into two main periods (Phase A: 2300–1300 BP; Phase B: 580 BP to the present). Charred botanical remains indicated two types of land-use: (1) domestic, with oil palm endocarps most often associated with potsherds (villages) and (2) agricultural, with charcoal as probable remnant of slash-and-burn cultivation (fields). Oil palm endocarp abundance decreased with distance from the identified human settlements. Our methodology allowed documenting, at high resolution, the spatial and temporal patterns of human activities in central African moist forests and could be applied to other tropical contexts.

While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and-burn agriculture since 3000–2000 BP (Before Present) could be the main driver of the persistence of light-demanding tree species. In order to examine anthropogenic factors in the persistence of such populations, our study focused on Pericopsis elata, an endangered clustered timber species. We used a multidisciplinary approach comprised of botanical, anthracological and archaeobotanical investigations to compare P. elata patches with surrounding stands of mixed forest vegetation (“out-zones”). Charcoal samples were found in both zones, but were significantly more abundant in the soils of patches. Eleven groups of taxa were identified from the charcoals, most of them also present in the current vegetation. Potsherds were detected only inside P. elata patches and at different soil depths, suggesting a long human presence from at least 2150 to 195 BP, as revealed by our charcoal radiocarbon dating. We conclude that current P. elata patches most likely result from shifting cultivation that occurred ca. two centuries ago. The implications of our findings for the dynamics and management of light-demanding tree species are discussed.