Soil Carbon and Nitrogen Stocks Under Plantations in Gambo District, Southern Ethiopia

Abstract

The effect of six plantation species in comparison to natural forest (NF) on soil organic carbon (SOC) and total nitrogen (TN) stocks, depth-wise distribution, biomass carbon (C), and N was investigated on plantations and cultivated lands on an Andic paleudalf soil in Southern Ethiopia. The SOC, N, and bulk density were determined from samples taken in 4 replicates from 10-, 20-, 40-, 60-, and 100-cm depth under each site. Similarly, the biomass C and N of the plantation species and understory vegetation were also determined. The SOC and N were concentrated in the 0- to 10-cm depth and decreased progressively to the 1-m depth. Next to the NF, Juniperous procera accrued higher SOC and N in all depths than the corresponding plantations. No evidence of significant difference on SOC and N distribution among plantations was observed below the 10-cm depth with minor exceptions. The plantations accrue from 133.62 to 213.73 Mg ha^–1 or 59.1 to 94.5% SOC, 230.4 to 497.3 Mg ha^–1 or 6.9 to 14.9% TBC and 420.37 to 672.80 Mg ha^–1 or 12.5 to 20% total C-pool of that under the NF. The N stock under Juniperous procera was the highest, while the lowest was under Eucalyptus globulus and Cupressus lusitanica. We suggest that SOC and N sequestration can be enhanced through mixed cropping and because the performance of the native species Juniperous procera is encouraging, it should be planted to restock its habitat.

Keywords:

• soil organic carbon (SOC)
• soil nitrogen (N)
• natural forest (NF)
• total biomass carbon (TBC)
• plantation forest
• Ethiopia

Acknowledgments

The financial support to this study from NORAD to Hawassa University, Ethiopia is gratefully acknowledged. The authors would like to thank Line Tau Strand and Jan Mulder for their comments on the manuscript and to Sheleme Beyene, Tesfaye Abebe, Abrahm Woldemichael, and Admasu Tsegaye for all support they provided during the fieldwork at Hawassa, Ethiopia. The authors also thank Teramage Tesfaye for his enormous assistance during the entire period of data collection and fieldwork.