Growth-ring analysis of Diploknema butyracea is a potential tool for revealing indigenous land use history in the lower Himalayan foothills of Nepal

Abstract

Slash-and-burn is a farming practice of the indigenous communities in the Himalayan foothills of Nepal. The traditional land-tenure system is based on a customary oral tradition. However, the government's persistent denial of land rights has fueled the indigenous conflicts in the last few decades. Deliverance of scientific evidence-based arguments may underpin the ongoing conflict-resolution dialogues between the authorities and the indigenous communities. Dating growth rings of trees in a slash-and-burn system might help the indigenous people to find evidence of their historic land uses in the mountainous landscape. In this pilot study, we examined the potential of Diploknema butyracea (Roxb.) H. J. Lam growth rings for documenting land use history of Nepalese indigenous farming practices, as this species is being preserved during the slash-and-burn practices. The species is an economically important and ecologically interesting (as it flushes leaves when everything is dry, and sheds leaves while everything is green) deciduous tree species belonging to Sapotaceae family and widely distributed in Sub-Himalayan tracts. Five stem discs were studied which were originated from the Kandrang valley of the Chitwan district, Nepal. For the first time, we revealed distinct growth rings in this species which are marked by fibers with thicker cell walls. Growth-ring anomalies, i.e., wedging and partially missing rings, were also found. Four out of five samples could be crossdated at a marginal level (GLK ≥ 60 and t ≥ 2.0) which is a confirmation of the annual nature of growth rings. One of the samples showed black spots of oxidized wood which are traces of fire, suggesting evidence of slash-and-burn practices in the study area since 1933. This study suggests a strong potential of D. butyracea for growth-ring analysis to reconstruct indigenous land use history in Nepal.