Effects of exotic <em>Eucalyptus spp.</em> plantations on soil properties in and around sacred natural sites in the northern Ethiopian Highlands

Abstract

Species of the genus Eucalyptus (common name eucalyptus) are widely planted all across Ethiopia—including on large areas of land previously allocated to food production. In recent decades eucalyptus has also increasingly been planted on lands around and within “church forests,” sacred groves of old-aged Afromontane trees surrounding Ethiopian Orthodox Tewahido churches. These revered holy sites have long been recognized for their cultural values and also for their ecosystem services—including their potential to support species conservation and restoration, as church forests are some of the only remaining sanctuaries for many of Ethiopia’s indigenous and endemic plant and animal populations. Ethiopian Orthodox church communities have a long history of planting and nurturing indigenous tree seedlings to sustain church forest groves. However, due to the fast-growing nature of eucalyptuscombined with its widely recognized socio-economic benefits (as fuelwood, charcoal, construction wood, etc.), this introduced species has been widely plantedaround church forests—in some cases even replacing native tree species within church forests themselves. In many developing country contexts the introduction of exotic eucalyptus has been shown to have ecological impacts ranging from soil nutrient depletion, to lowering water tables, to allelopathic effects. In this study, we collected soil samples from indigenous forest fragments (church forests), adjacent eucalyptus plantations, and surrounding agricultural land to examine how eucalyptus plantations in Ethiopian Orthodox church communitiesmight impact soil quality relative to alternative land uses. Soil properties, including organic matter, pH, total nitrogen, and total phosphorus were measured in samples across 20 church forest sites in South Gondar, East Gojjam, West Gojjam, Awi, and Bahir Dar Liyu zones in the Amhara Region of the northern Ethiopian Highlands. Findings indicate that although soil in eucalyptus stands is more acidic and has lower organic matter and nutrient levels than nearby church forests, eucalyptusplantations also exhibit consistently higher organic matter and nutrient levels when compared to adjacent agricultural land. These findings suggest that eucalyptus planting could potentially benefit soil fertility on land that has been degraded by subsistence agriculture.