Abstract
Pulse-like rapidly increasing CO2 effluxes occur in soils under seasonally dry climates in response to summer rain events, and these CO2 outbursts can have a marked influence on the ecosystem carbon balance. Two irrigation experiments were conducted at the end of the dry season in a Mediterranean Pinus canariensis forest at its upper distribution limit in Tenerife, Canary Islands. Soil CO2 efflux was discontinuously monitored along with soil temperature and soil water content during and after irrigation. Correlation analysis suggested that soil moisture is the leading environmental factor regulating soil CO2 efflux during summer rain events. Cumulative CO2 efflux following a precipitation pulse was estimated to be 50% higher than the value calculated for the dry soil, which is approximately 3% of the year round soil CO2 efflux. It is concluded that such CO2 effluxes may have implications for the prediction of forest response to increasing dryness combined with an increase in the irregularity of summer rain events in Mediterranean regions.
Acknowledgments
The authors express their gratitude to the Spanish Government (Projects CGL2006-10210/BOS ME and CGL2010-21366-C04-04 MCI), University of La Laguna (MGC/08/14 and 2009), and Canarian Government-University of La Laguna (“Proyecto Estructurante”) all co-financed by FEDER. The authors also thank the National Park's Network for permission to work in Teide National Park. P. Brito received a fellowship from ACIISI, Canarian Government.
Notes
Note: c (=F S at 10°C; µ mol m−2 s−1) and d (°C−1) are regression coefficients, R 2 is the proportion of variability explained by soil temperature in 10 cm soil depth. Q 10 calculated from b (Q 10 = e10d ), and p-value. The standard errors of the regression coefficients are shown in brackets.