Changes in soil carbon and total nitrogen following reforestation of previously cultivated land in the highlands of Ethiopia

Abstract

Changes in soil C and total N stocks were investigated following reforestation of previously cultivated soil in compariso n with soil subjected to continuous cultivation and soil under an adjacent natural forests in south central highlands of Ethiopia. Two of the most widely planted tree species in the highlands of Ethiopia, namely Eucalyptus saligna and Cupressus lusitanica, were considered in the plantation treatments. Soil C and total N contents in the upper 0-10 and 10-20 cm soil layers were significantly different in the order: Natural forest > C. lusitanica > E. saligna > Farmland. Differences in soil C and total N contents among the sites for soil depths greater than 20 cm were negligibly small and statistically not significant. Soil C and total N stocks in the upper 0.80 m mineral soil also varied significantly in the same order as above. Estimated average annual soil C accruals were 156 and 37 g C m -2 yr -1 for Cupressus lusitanica and Eucalyptus saligna, respectively. The results demonstrate that reforestation of former arable soils in the dry Afromontane region of Ethiopia could yield significant restoration of soil C and total N that are lost in the process of natural forest conversion into arable lands and subsequent cultivation. However, the two plantation species differed considerably with respect to the rate of soil C and total N accrual. This suggests that proper selection of tree species will considerably affect the magnitude and rate of soil C sequestration.

The extent of soil organic carbon and total nitrogen in forest fragments of the central highlands of Ethiopia

“…Due to the reduction in aboveground biomass through different impacts from human and livestock activities; there will be variation in SOC accumulation and TN across the fragments sampled with relatively higher concentration for fragments with higher diversity of species. The loss of SOC and TN is particularly significant in the context of land use changes due to the reduction in aboveground biomass (Lemenih et al 2005;Gelaw et al 2013;Gurmessa et al 2016;Tesfaye et al 2016). We also anticipate a decrease in SOC and TN as depth increases (Lemenih et al 2005).…”

“…Maintaining SOC and TN through improvements of forest cover is an important aspect in climate change mitigation as the loss of carbon and nitrogen to the atmosphere through soil disturbances can cause an enormous addition of the elements to the atmosphere (Lemenih et al 2005;Vágen et al 2005;Strassburg et al 2010;Gamfeldt et al 2013;Berenguer et al 2014;Gelaw et al 2014;Gurmessa et al 2016;Tesfaye et al 2016). It has been found that forests and their soils store about 45% of the terrestrial carbon and act as crucial carbon sources (Gamfeldt et al 2013;Tesfaye et al 2016), and tropical forest ecosystem soils store about 60% of the total carbon stocks (Vágen et al 2005).…”

“…Although studies (Lemenih et al 2005;Workneh 2008;Gelaw et al 2014;Tesfaye et al 2016;Gurmessa et al 2016) have clearly shown that forest ecosystems play vital roles in regulating of carbon and nitrogen losses to the atmosphere, little research has attempted to come up with the roles played by fragmented forests in improving the maintenance of SOC and TN in the soils except a study conducted by Cardelús et al 2013and Vanderhaegen et al (2015 in Northern and South western Ethiopia.…”

Advances in quantifying soil organic carbon under different land uses in Ethiopia: a review and synthesis

“…There exist several published scientific articles and case studies on soil carbon pools for different parts of Ethiopia (Yimer et al 2006;Girmay et al 2008;Hawando 1997;Solomon et al 2002a;Lemenih et al 2005;Haileslassie et al 2005;Lemma et al 2006;Edwards 2007;Chibsa and Ta 2009;Freier et al 2009;Fisseha et al 2011;Kim et al 2015;Demessie et al 2015;Berihu et al 2017) but with a missing gap on the national soil database carbon pools estimate (Shiferaw et al 2013;Okolo et al 2016). However, most of the SOC researches were conducted in the southern part of Ethiopia, thus not giving a comprehensive clear overview of the trend in total soil carbon distribution data across different landscapes and regions of Ethiopia, which this review intends to address systematically.…”

“…However, most of the SOC researches were conducted in the southern part of Ethiopia, thus not giving a comprehensive clear overview of the trend in total soil carbon distribution data across different landscapes and regions of Ethiopia, which this review intends to address systematically. For example in the highlands of southern Ethiopia, changes in SOC stock was investigated by Lemenih et al (2005) after reforestation of previously cultivated soil in comparison with continuously cultivated soils and adjacent natural forests soils. For Cupressus lusitanica and Eucalyptus saligna, they reported an average annual soil C accumulation estimate of 156 and 37 g C m −2 year −1 respectively.…”