TY - JOUR

T1 - Soil CO2 efflux in an Afromontane forest of Ethiopia as driven by seasonality and tree species

AU - Yohannes, Yonas

AU - Shibistova, Olga

AU - Abate, Asferachew

AU - Fetene, Masresha

AU - Guggenberger, Georg

N1 - Funding information: We would like to thank Deutsche Forschungsgesellschaft (DFG) for financial support of the study within the project package PAK 188. We thank Deksiso Bulcha, Getu Tadesse, Temesgen Yohannes, Abule Loya, and Awol Assefa for their assistance and support in collecting data in the field. We also thank Roger-Michael Klatt, Ulrike Pieper, Pieter Wiese and Holger Ciglasch for their laboratory assistance in soil analysis. Likewise we are grateful to Frank Schaarschmidt and Hany El Kateb for their advice in statistical analysis.

PY - 2011/3/15

Y1 - 2011/3/15

N2 - Variability of soil CO2 efflux strongly depends on soil temperature, soil moisture and plant phenology. Separating the effects of these factors is critical to understand the belowground carbon dynamics of forest ecosystem. In Ethiopia with its unreliable seasonal rainfall, variability of soil CO2 efflux may be particularly associated with seasonal variation. In this study, soil respiration was measured in nine plots under the canopies of three indigenous trees (Croton macrostachys, Podocarpus falcatus and Prunus africana) growing in an Afromontane forest of south-eastern Ethiopia. Our objectives were to investigate seasonal and diurnal variation in soil CO2 flux rate as a function of soil temperature and soil moisture, and to investigate the impact of tree species composition on soil respiration. Results showed that soil respiration displayed strong seasonal patterns, being lower during dry periods and higher during wet periods. The dependence of soil respiration on soil moisture under the three tree species explained about 50% of the seasonal variability. The relation followed a Gaussian function, and indicated a decrease in soil respiration at soil volumetric water contents exceeding a threshold of about 30%. Under more moist conditions soil respiration is tentatively limited by low oxygen supply. On a diurnal basis temperature dependency was observed, but not during dry periods when plant and soil microbial activities were restrained by moisture deficiency. Tree species influenced soil respiration, and there was a significant interaction effect of tree species and soil moisture on soil CO2 efflux variability. During wet (and cloudy) period, when shade tolerant late successional P. falcatus is having a physiological advantage, soil respiration under this tree species exceeded that under the other two species. In contrast, soil CO2 efflux rates under light demanding pioneer C. macrostachys appeared to be least sensitive to dry (but sunny) conditions. This is probably related to the relatively higher carbon assimilation rates and associated root respiration. We conclude that besides the anticipated changes in precipitation pattern in Ethiopia any anthropogenic disturbance fostering the pioneer species may alter the future ecosystem carbon balance by its impact on soil respiration.

AB - Variability of soil CO2 efflux strongly depends on soil temperature, soil moisture and plant phenology. Separating the effects of these factors is critical to understand the belowground carbon dynamics of forest ecosystem. In Ethiopia with its unreliable seasonal rainfall, variability of soil CO2 efflux may be particularly associated with seasonal variation. In this study, soil respiration was measured in nine plots under the canopies of three indigenous trees (Croton macrostachys, Podocarpus falcatus and Prunus africana) growing in an Afromontane forest of south-eastern Ethiopia. Our objectives were to investigate seasonal and diurnal variation in soil CO2 flux rate as a function of soil temperature and soil moisture, and to investigate the impact of tree species composition on soil respiration. Results showed that soil respiration displayed strong seasonal patterns, being lower during dry periods and higher during wet periods. The dependence of soil respiration on soil moisture under the three tree species explained about 50% of the seasonal variability. The relation followed a Gaussian function, and indicated a decrease in soil respiration at soil volumetric water contents exceeding a threshold of about 30%. Under more moist conditions soil respiration is tentatively limited by low oxygen supply. On a diurnal basis temperature dependency was observed, but not during dry periods when plant and soil microbial activities were restrained by moisture deficiency. Tree species influenced soil respiration, and there was a significant interaction effect of tree species and soil moisture on soil CO2 efflux variability. During wet (and cloudy) period, when shade tolerant late successional P. falcatus is having a physiological advantage, soil respiration under this tree species exceeded that under the other two species. In contrast, soil CO2 efflux rates under light demanding pioneer C. macrostachys appeared to be least sensitive to dry (but sunny) conditions. This is probably related to the relatively higher carbon assimilation rates and associated root respiration. We conclude that besides the anticipated changes in precipitation pattern in Ethiopia any anthropogenic disturbance fostering the pioneer species may alter the future ecosystem carbon balance by its impact on soil respiration.

KW - Croton macrostachys

KW - Ethiopia

KW - Podocarpus falcatus

KW - Prunus africana

KW - Soil CO efflux

KW - Soil moisture

KW - Soil respiration

KW - Soil temperature

KW - Tropical forest

UR - http://www.scopus.com/inward/record.url?scp=79551522931&partnerID=8YFLogxK

U2 - 10.1016/j.foreco.2010.12.032

DO - 10.1016/j.foreco.2010.12.032

M3 - Article

AN - SCOPUS:79551522931

VL - 261

SP - 1090

EP - 1098

JO - Forest ecology and management

JF - Forest ecology and management

SN - 0378-1127

IS - 6

ER -