Harvesting techniques, hemiparasites and fruit production in two nontimber forest tree species in south India

Increasing demands for non-timber forest products and their commercial extractions can result in harvesting methods that maximize short term economic gains with little attention to long term ecological consequences. We assessed the ecological impacts of harvesting techniques used by an indigenous group, the Soligas, on the non-timber forest products they extract from the forests of Biligiri Rangan Hills, south India. Specifically, we examined patterns of resource availability of two non-timber tree species, Phyllanthus emblica and P. indofischeri, and how the current fruit harvesting techniques influence fruit yields, and susceptibility of trees to infestations by hemiparasitic plants of the Loranthaceae family. We also assessed how hemiparasite infestations affect fruit production and growth rates of Phyllanthus trees. There was considerable variation in fruit production in both species of Phyllanthus from one fruiting season to the next. The Soligas harvest an average of 86% (±17.72%) of the fruit yield on a per tree basis in P. emblica and 94.17% (±6.9%) in the case of P. indofischeri. At the population level, 64.75 and 86.6% of the fruit productivity is harvested in P. emblica and P. indofischeri, respectively. However, not all individuals or populations are harvested. Harvesting techniques used resulted in cutting of 15% of P. indofischeri trees and 5% of P. emblica trees. The current harvesting techniques used by the Soligas reduce fruit production in P. emblica in the following year (R²=0.27,p=0.03). Furthermore, the Soligas selectively harvest fruits from trees that have larger fruit crop sizes in both species. Individual trees that carried a greater load of hemiparasites produced significantly lower fruit yields (P. emblica: r=−0.32,p<0.013; P. indofischeri: r=−0.73,p<0.001). The presence of hemiparasites significantly affected the growth rates of trees.

Current harvesting techniques used by the Soligas have negative impacts on trees of Phyllanthus spp., as do infestations by hemiparasites. Current fruit harvesting strategies and techniques used by the Soligas focus on maximizing the economic returns by adopting methods of extraction such as lopping of branches and cutting of trees. Such practices can ultimately decrease the rates at which the populations grow, thereby making the extraction of Phyllanthus fruits unsustainable. Adopting more sustainable methods of harvesting appears to be one viable solution to the current ecological problem facing the conservation of Phyllanthus trees in the forests of Biligiri Rangan Hills.